+++ #55
Subject: Wood Winged Bearhawk????
From: Tom Brant 

I thought this might stir up some discussion...  Anyone ever think about
using a wooden wing on the Bearhawk?  I've given it some thought lately,
and am considering designing one.  I like working with wood much more
than sheet metal and I know there are others like me out there too.  I
am aware that the wieght and cg and strentgh will all need to be
considered, but are there any of you engineer types out there that would
like to comment?  Depending on what I hear from people here, I will
probably call up Bob Barrows and get his opinions on this as well, but
as far as I know, no one has ever designed one before, or even thought
about it.  Let me know what you guys think!

+++ #56
Subject: Re: Wood Winged Bearhawk????
From: Float-by Shooter

> I thought this might stir up some discussion...  Anyone ever think
> about using a wooden wing on the Bearhawk?  I've given it some

If you are serious about building wooden wings, you might take a close
look at the Christavia Mk. 4.  It is a 4 seater similar to the bearhawk
though it probably won't cruise as fast.  Like the Bearhawk, it has a
welded steel tube fuse, and was designed for wooden wings so you will
not have all the issues of integrating your own design wings into the
bearhawk design.  I think if the Bearhawk didn't exist I would probably
be building either a 2 or 4 seat Christavia.

There is an unofficial Christavia webpage at
http://www.spots.ab.ca/~kbeanlan/christavia.html

Also check out Corky Scott's christavia mark 4 project at
http://www.dartmouth.edu/~cscott/

I think there is a lot to be said for the wooden wing over the aluminum
one as far as the required tool investment goes.  I've read on the
rec.aviation.homebuilt newsgroup that the spruce spars can be difficult
to come by in the size needed, but one solution to this is to use
douglas fir instead.  One thing about aircraft spruce, it is great to
work.  I still have one complete unairworthy citabria spar which I am
hoarding for another boat project someday....you have to keep an eye on
it though since if left unattended it tends to be used for other, less
worthy causes (just ask Mike M.)

Don't get me wrong though, I still like the Bearhawk better.

+++ #59
Subject: Wood Winged Bearhawk????
From: Russ Erb

>Anyone ever think about using a wooden wing on the Bearhawk?<

Tom, you asked for an opinion, so here's mine. (You can probably guess
where this is going...) The only reason why you should consider
designing a whole new wing for the Bearhawk would be if you enjoy the
process of designing. The process would certainly drag out your building
time for several years more. I suspect the result would be heavier than
the aluminum wing. If you're going to do that, why stop at the wing?
Design yourself a whole new airplane.

Even though, like most people, wood was the first medium I learned to
work in, I personally don't care for wood as an aircraft building
material because the high quality wood required is difficult (extremely
difficult?)  to find, and then you still end up rejecting 90% of
it. (Note: This is what I've read, I haven't actually tried it myself)
As a result, it gets very expensive. With aluminum and steel tubing, I
call up my friendly supplier, order some material, and whatever shows up
is useable. No hassles.

Then there's the whole gluing issue. The glueing process seems far more
picky about quality of fit, environmental conditions, time required, etc
than riveting.

If you are thinking of a fabric covered wood wing, you'll need a second
wing strut to the rear spar to take care of the wing torsion. This now
gets into fuselage modifications--Yikes! If you stay with the single
strut, the wing would have to be skinned in plywood, and I'm guessing
the result would be heavier.

It was a Fokker Tri-motor with a wood spar that killed Knute Rockne and
ended up with wood banned from commercial airliners as a material. Study
your aviation history if you don't know what I'm talking about.

As for the tool investment that Del mentioned, the key word is
"investment." Yes, it may be a factor if you only plan to ever build one
airplane. The investment cost drops quickly when amortized over several
airplanes. Even if you only build one, a good set of tools should be
easy enough to sell to another up and coming homebuilder when your done
with them and recover a large amount of the cost.

If your sole reason for asking this is because you like working with
wood better than aluminum, I would recommend you do one of two things:
1) Forget the Bearhawk and build something already designed with a wood
wing 2) Take a class in sheet metal. I've found with the right tools
aluminum is actually quite easy to work

Hey, you asked...

+++ #174
Subject: Re: Bearhawk to Sweden
From: Float-by Shooter

> I'm forwarding your message to our Bearhawk e-mail group.  Perhaps one
> of them knows more about float planes.

Russ, thanks for posting this.  I also received email from this person
earlier in the week but somehow lost the message and with it their
address, I think it fell victim to my clumsy fingers.  I don't think I
can help them much but I felt bad about not being able to respond.

> I was told about the Bearhawk from Sune Larsson in sweden.  The plane
> looks great. But will it be a great floatplane?  Could you get me in
> contact with a Bearhawkbuilder that has some experience with
> floatplanes?

Based on what I have seen in the archives I think it is high time that
we find such a person and recruit him for the Bearhawk email list.
Ideally this person should have a Bearhawk/float combination flying.
8^)

> I have also found a pair of EDO 2440 floats with a fastening kit to
> the Maule (they have some damage, but can be fixt). They must be the
> right ones for the Bearhawk?

Two things that I would try to do, first find out what Maule they were
on and find out what its gross weight is, and how closely it compares to
the Bearhawk's.  IF the gross weights are similar try to talk to
somebody who has flown that particular combination of plane/floats to
find out how it handled.  Maybe there is a Maule type club.  One
suggestion that has been made to me when I asked a similar question on
the rec.aviation.homebuilt newsgroup is to contact the seaplanes
association at www.seaplanes.org and also maybe see if I could get my
hands on some float STC paperwork for similar certified craft.  You
might try contacting Kenmore Air in Seattle since they seem to be the
float experts, also there are probably people at Lake Hood in Anchorage
who could advise you.  I haven't done any of this yet since at the
moment researching a float setup has a relatively low priority on the
(ever growing) list of things to do.  One of my goals for the next 3-4
years is my float rating which is supposed to be one of the easier
ratings to get.  I recently spoke with an aquaintance who got his at
lake hood last year in a Beaver, cost him about $600.  Once I do that I
should have the knowledge base and contacts to dive into the research.

Which of course is absolutely no help to you now.

+++ #181
Subject: Bearhawk to Sweden
From: Rod Smith

The EDO 2440 floats would make a good choice for the Bearhawk. They are
certified for use on every model of Maule aircraft except possibly the
new 160HP version. I don't recall exactly the gross weight allowable but
I believe it is about 2500#s for a Maule on these floats. The Bearhawk
is very similar in size, construction and performance to a
Maule. Chances are the struts will need to be modified somewhat for
attaching to the Bearhawk but they should be close to the correct
size. Will not be a big deal if you can put the Bearhawk together. Just
a matter of buying some streamline steel tubing or possibly cutting the
struts you have to fit. The important thing is getting the correct deck
angle set. May want to send a copy of page 1 of the BH plans to EDO to
see if they can help you.

+++ #202
Subject: So You Want To Be An Aircraft Designer
From: Russ Erb

Greetings, Bearhawkers!  Below is an article I wrote at Mike's request
for inclusion in Bear-Tracks.  For various reasons not worth repeating,
it's been more than a year from when he requested it.  As you'll see,
the article grew until it was way too big for Bear-Tracks, so I'm
releasing it in this forum.  I'm sure that it will soon appear in Del's
FAQ file.

So You Want To Be An Aircraft Designer?

That's the real question you are asking when you take up that time
honored homebuilder's hobby of aircraft design modifications. If you
feel you are qualified to do this and understand the risks involved,
then do so and enjoy.  If you have not had the appropriate engineering
training, and your engineering techniques are best described as "eyeball
engineering" or "TLAR" (that looks about right), realize that there are
risks involved in design changes, and you're probably better off just
building your aircraft to the plans.  Besides, if you have to make major
design changes to make the aircraft do what you want it to do, maybe
you're building the wrong aircraft.

Purpose

I am writing this article in response to a request from Mike Meador.
After reading some of my previous writings, he felt that I would be able
to respond with the benefits and pitfalls for some of the many
modifications that builders have asked Bob Barrows to approve.

It never ceases to amaze me how many unqualified people think they can
"improve" a design, but don't understand the design process.  Of course,
with sufficient study they could learn enough about aircraft design to
be successful, but typically they don't bother.  After all, college
students spend years learning about engineering and design.

Think about how a designer might respond when, after years of effort
making everything work together, some yahoo comes along saying the
design is okay but here's how to make it better.  Usually said yahoo
does not see the disadvantages of his proposed modification, or its
impact on other parts of the design.  Thus, the purpose of this article
is to give you some insight into the design process and hopefully make
you think twice about that modification you might be proposing.

Not All Modifications Are Bad

However, before I get any farther into this, let me make the point up
front that I am not saying that all modifications are bad.  The Bearhawk
plans intentionally leave a lot of latitude for the builder to
personalize his or her airplane.  In fact, you can't get away from it.
You may have noticed that drawings 29-32 detailing the firewall forward
engine installation were not included in your plans package.  There's a
good reason for this--they don't exist!  Bob realized that the biggest
variation in Bearhawks would be what engine was installed, so he didn't
even bother drawing up his installation because he knew yours would be
different. While I don't share Bob's allergic reaction to electricity, I
do know that my arms are allergic to an improperly hand-propped
engine. Therefore, I will be installing an electrical system, complete
with starter.  However, we will see that there is a difference between
modifications which don't affect the primary aircraft structure and
those that do.

Defining Your Mission

No, this isn't trying to describe the Alamo or San Jose.  This is simply
deciding what you plan to do with your completed aircraft.  Knowing what
your planned mission is will help you answer many questions.  For
instance, if your desire is to cruise at 25,000 feet at 300 knots, you
will know that you don't want to build a VP-1 Volksplane.  The Glasair
III is a fine aircraft, but would not be a good choice if you want four
seats to carry yourself, your spouse, and your two kids.  When deciding
what aircraft you want to build, you should start with an aircraft
design reasonably capable of completing the mission without
modification.

The "Design Propagation Nightmare"

Design is characterized by a series of compromises. A design is not
optimized to do any one thing, but to do everything adequately.  A
design optimized for strength would probably be too heavy. A design
optimized for minimum drag would probably be difficult to build and
maintain.

A design is like a house of cards--if you move one card, it affects all
of the other cards.  It has been said that changing the number of screws
in the spinner would eventually require a new tailwheel. Changing one
item will change another, which will change another, which will change
another, until an incredible amount of seemingly unrelated things have
been changed.  This is what I call the "Design Propagation Nightmare."

A classic historical example was designing the Spirit of St. Louis.
Charles Lindbergh went to San Diego to visit the Ryan Company and was
suitably impressed with the Ryan M-2 Mailplane.  It looked like it would
suit his mission of flying from New York to Paris. It was a three place
aircraft with low drag, an efficient design for it's day, and a good,
reliable engine.  Sounds perfect, except it had one minor problem--it
didn't have sufficient range to fly from New York to Paris, which, of
course, was a major mission requirement.

Now at this time, a typical homebuilder might think "No problem!  We'll
just put in a larger fuel tank."  If only it were that simple. The
Spirit of St. Louis makes such a good example of the Design Propagation
Nightmare because Lindbergh was not interested in increasing the
endurance of the airplane by a couple of hours.  He needed to increase
the fuel capacity by 750%! Adding this much fuel impacts the design in
two major areas--volume and weight.

Volume was a problem because there wasn't enough room in the wings or a
header tank for that much fuel.  The large amount of fuel compared to
the aircraft's empty weight (fuel fraction) meant that it was possible
that the aircraft's center of gravity could change drastically as the
fuel was consumed.  To minimize the change in cg, all of the fuel tanks
were concentrated around the cg.  Additionally, Lindbergh did not want
any fuel tanks behind the cockpit for fear of getting trapped between
fuel tanks in a crash, especially during takeoff.  The most obvious
effect of this decision was that the fuel tanks totally blocked his
forward visibility.  Lindbergh decided that this was an acceptable
impact for several reasons.  Taildraggers are notorious for poor
visibility on the ground, so what's a little less visibility?  Most of
the flight would be over water on instruments with no landmarks to see
anyway.  Lindbergh was also confident that there would not be any other
aircraft on his route that he would need to see and avoid.

The increased weight dictated that more wing area was needed to keep the
wing loading to an acceptable value for the available power and to keep
the cruising speed close to the best range speed.  Donald Hall, the
designer, chose to keep the same chord, allowing him to use the existing
wing ribs and the same fuselage attachment.  Wing area was increased by
increasing the wing span.  With a larger wing span, the longitudinal and
directional stability were both decreased.  The solution to both of
these problems was to either enlarge the tail surfaces or to lengthen
the fuselage.  In this case, Donald Hall decided it was easier to
lengthen the aft fuselage than to redesign the tail surfaces.
Lengthening the aft fuselage threw the cg out of whack, so the nose had
to be extended to compensate.

The increased span also decreased roll performance, but since roll
performance was not important to this mission, the ailerons were not
changed.

The increase in span did create an increase in wing bending moments,
which required beefing up the wing structure, which added more weight.

The increase in gross weight required a stronger landing gear, which
again adds more weight, and may cause more drag. More weight and drag
requires more fuel, which increases the weight, and the cycle repeats.

The end result was that the NYP (as Ryan Aircraft designated the design)
was a totally new airplane except for the tail feathers, all because of
a "simple little change."

The vast majority of modifications, especially those typically added by
EAAers, all have one thing in common--they add WEIGHT!  In my extensive
studies, I have only found one instance where adding weight is a good
thing.  Racing sailplanes carry water ballast to increase their gross
weight, which increases the airspeed for best glide without changing the
glide ratio.  Even in this case, the water ballast is jettisoned prior
to landing to restore the landing speed and weight back to an acceptably
low value.  In every other case I have ever looked at, adding weight
will be a detriment to aircraft performance.

Now that we've discussed modifications in general terms, let's look at
some specific modifications that have been proposed by Bearhawk
builders, presented here in no particular order.

Cockpit Adjustable Rudder Trim Tab

Very few if any similar production aircraft have rudder trim tabs. For
the flight conditions that a Bearhawk is likely to see, there is very
limited usefulness for one.  During takeoff, you are actively
controlling the rudder in an effort to remain lined up with the runway,
so rudder trim would be of little use.  During the climb, a constant
rudder deflection will probably be required to keep the ball centered,
but this is only for a limited duration (If you can't hold the rudder
for a few minutes, maybe you should visit the gym more frequently).  For
cruise flight, a fixed tab can be ground-adjusted to trim the rudder.
You're probably going to cruise at pretty close to the same conditions
most of the time, and the propeller effects on directional trim are
small over the limited range of cruise airspeeds.  For descent, you will
probably be at similar airspeeds to the cruise conditions, so rudder
trim changes would be minimal.  In the landing phase, the rudder will be
actively controlled as in the takeoff.

A cockpit adjustable rudder trim tab could be installed without
significantly affecting the primary structure.  However, the benefit
gained would be very small compared to the time and effort required to
install it and the weight that would be added at the tail end of the
airplane, which is probably the worst location to add weight (because of
its effect on the cg).

Another possible way to get the same result much simpler would be to
install some sort of bungee trim system on rudder system.  This could be
as simple as a lever in the cockpit attached to a spring attached to the
rudder cable.  It doesn't affect primary structure, is much simpler than
implementing a tab on the rudder, and the added weight is closer to the
cg.  A similar system could be considered for aileron trim as well.

Folding Wings

Folding wings have been popularized in recent years by the Kitfox and
Avid lines of aircraft.  This popularity is primarily based on a
marketing concept of being able to land at the airport, fold the wings,
tow the airplane home, and store it in your garage.  To a lesser extent,
folding wings could allow the airplane to be stored in a smaller hangar.

There are several things that they don't tell you, however. The effort
required to fold the wings may quickly convince you not to bother.  It's
the same line of thinking that a car is much more likely to be put in
the garage if the garage has an automatic door opener.  Otherwise the
benefit of putting car away is quickly overpowered by effort to get out
and open door.  (Of course, some of you may be unfamiliar with the
concept of putting a car in a garage--after all, the purpose of a garage
is to give you a place to build airplanes, right?)

Though Skystar shows the airplane being towed on its landing gear, they
will also quickly tell you that you don't want to do that any farther
than a mile or two.  Remember that the landing gear bearings and
suspension are designed to taxi slowly to the runway, then roll at high
speed for the length of the takeoff or landing.  They aren't intended
for high speed over long distances.  Skystar will tell you that if you
want to go any farther than a couple of miles you'll need to put the
airplane on a trailer.

I don't know how big garages are in Nampa, Idaho, but a Kitfox would not
fit in the garage of any of the last three houses I've lived in.  Well,
it would fit in the two car garage, but it would have gone in diagonally
and taken up the whole garage.  I seriously doubt many Kitfoxes are
towed home from the airport and stored in the garage, regardless of what
Skystar's marketing says.  What makes you think your Bearhawk, which is
much larger than a Kitfox, will follow you home and live in your garage?
It sure won't fit in mine!

There's also that minor detail that any vehicle on the road is limited
to a width of 8 feet.  Folding the Bearhawk wings directly rearwards,
pivoting at the rear spar (as the Kitfox does), would result in a
vehicle 12 feet wide!  You could design a pivot to fold the wings
against the fuselage as in the F6F Hellcat or TBF/TBM Avenger, but that
pivot would still have to carry all of the flight loads.

Still think you want to fold the wings?  Here are a few more items
you'll want to consider.  Will the trailing edges of the wings overlap
in the folded position?  You might be able to move the flaps and
ailerons out of the way, but what about the back rib area at the root
and the wingtips?  Is the fuselage in the way of the folding wing?
Getting fuselage clearance may require redesign of primary structure.
An additional strut would be needed to support the wing during the
folding process, and the attach point for the strut would have to be
moved onto the folding axis.

I'm estimating that the wing weighs about 100 pounds.  This weight, plus
the weight of the fuel (up to 165 pounds per wing) adds up to a large,
heavy object that I would rather not try to muscle around. A vent system
for the fuel tanks would need to be designed that would properly vent
with the wings in the extended position and at least not let fuel drain
out in the folded position.  The aileron control system of the Bearhawk
does not lend itself to wing folding, so it would have to be
redesigned. Most of all, you would be messing with a critical structural
area, and adding at least one more critical preflight item.

Then there's the horizontal tail. It is 10 feet wide, which is too wide
to tow down the road unmodified.  You would either need to be able to
remove the horizontal tails, which would again require disconnecting
flight controls, or redesign the tail to also fold.  If you redesign the
horizontal tail to shorten its span, you would have to increase the
chord to maintain the same area.  Actually, you would have to increase
the area because the lower aspect ratio is aerodynamically less
effective, and the elevators would also be less effective.  The
structural load paths would also change, requiring more redesign.  Of
course, the tail would look different, and would probably not look as
good.  Aesthetics are a big part of how well your airplane is accepted.
After all, you don't want to fly around with a bag over your head, do
you?

Spring Steel Landing Gear

Spring steel landing gear change the paths of the landing loads into the
fuselage from 3 points to 2 points for each side. A tapered rod landing
gear further reduces it to 1 point.  Because of these differences,
changing the landing gear style would require the redesign of major
fuselage structure. According to Bob Barrows, large steel plates would
be required to distribute the loads, which would add more weight.

Even if spring steel gear were installed, I'm not convinced it would be
an improvement.  As the name says, the landing gear is a big spring with
very little damping. As a result, you will probably bounce more landings
than with the as-designed damped landing gear, which allow heavier
landings with the dampers preventing the landing gear springing the
airplane back into the air.

The purported benefit of spring steel landing gear is reduced drag over
tubular landing gear, especially landing gear with exposed bungees, such
as on the Piper Cub.  There would only be a slight difference in drag
between the spring steel landing gear and the Bearhawk gear.

Stinson 108 Landing Gear

The existing landing gear is plenty big enough. While I am not familiar
with the Stinson 108 landing gear, I am told that it is heavier.
Besides, unless it would be a pure bolt-on replacement, using it would
create more work than it would save, because you would have to redesign
the landing gear attach points on the fuselage.

Fabric Covered Wings

This is not as easy as just leaving off the aluminum skin and covering
the wing in fabric.  Have you ever noticed that fabric covered wings
always have two struts per wing while aluminum wings only have one
strut? The difference arises from differences in how the torsion
(twisting) loads are handled.

An aluminum skin will resist torsion.  To see this, try twisting a soda
can.  It will resist the twisting, even if you partially flatten it so
that it looks more like an airfoil.  Now try twisting a leg of panty
hose.  The fabric offers virtually no resistance.  To prevent twisting,
a fabric covered wing requires two struts, one to each spar.

Two Strut Wings

As mentioned above, two struts are only needed with fabric covered wings
for torsion resistance.  A second strut adds nothing but drag and weight
to an aluminum covered wing.

36 Foot Wing Span

The current wing span is about 33 feet, so a 36 foot wingspan would be
an increase of 1.5 feet on each side.  I'm not sure of the reason for
this proposal.  Perhaps more wing area for shorter takeoffs and
landings?  The Bearhawk already has as good or better STOL performance
than most any aircraft out there, such as the Cessna 180. Perhaps
looking for a higher gross weight? On the contrary, if you extend the
span without changing the structure, you would actually DECREASE the
maximum gross weight because the wing bending moment would increase
because of the longer moment arm.  The highest bending moment for a
strut braced wing is at the strut attachment point.  If the wing span is
increased without moving the strut attachment point, the longer wing
would increase the bending moment.  The bending moment might be reduced
somewhat by moving the strut attachment point outboard, but this has the
drawback of worsening the bracing angle of the strut.  As the bracing
angle changes, the tension loads in the strut and the compression loads
in the wing between the strut and the fuselage increase. Additionally,
since the portion of the wing between the strut and the fuselage is
longer, its resistance to buckling under compression is reduced.  The
bottom line is that if you are interested in increasing the wingspan
with the idea of increasing the maximum gross weight, you will need to
totally redesign (beef up) the wing structure.

Steel Wing Struts

A steel strut with the same tensile strength as the specified aluminum
strut would be of a smaller cross section.  While this might seem
advantageous for reducing drag, it is weaker than the aluminum strut in
compression (i.e. more likely to buckle) because of the smaller cross
section.  Wing struts are occasionally under compression, such as when
you are sitting on the ground, the occasional hard landing (though you
never do that, of course), and during that nasty big down draft that
bounced you off of your seat belt last week.  Because the wing strut is
very slender for its length, it is much weaker in compression (buckling)
than in tension.  Reducing the cross section size (i.e. making it more
slender) makes the problem worse.

Switching to a steel strut may or may not reduce the weight when sized
strictly for tensile loads.  When a steel strut is sized to handle the
compression loads, it will very likely be heavier than the aluminum
strut.  Either that or you will have to add a jury strut as seen on
Piper Cubs, which adds back the drag you were trying to get rid of.

Then there's the corrosion problem.  Seen a few Piper ADs lately?  The
Bearhawk runs the aileron control cable up the inside of the wing strut.
If you set up a steel strut the same way, water would soon get inside
the strut and start rusting it away from the inside.  Tough to detect
and even tougher to repair.  Alternatively, you could seal the strut by
welding the ends closed, and then run the control cable externally
through fairleads on the back of the strut, as was done on early Piper
Cubs.  However, this will probably add as much drag as you saved.
Additionally, if you get into icing conditions, you're going to get some
serious flight control problems really quick.  Incidentally, such a
configuration is no longer certifiable under current FARs for just that
reason, which can be interpreted to mean that it's not a very good idea.

Extruded Wing Spars

I don't see the benefit in this, unless you happen to have the equipment
to make the extrusion dies and do the extruding.  Even then, you would
not want the spar to have a constant cross section from root to tip.
The spar design is beefiest where the greatest loads are (at the strut
attach point), and thins out where the loads are smaller.  Any constant
cross section extrusion strong enough to handle the loads at the strut
attach point will be heavier than the built-up spar.  Either that, or
the extruded spar will require extensive machining to remove the extra
unneeded weight.  The built-up spar is actually a very simple and
effective design.  I think it is even simpler than the RV spar which
uses bigger rivets (3/16") and has multiple webs.  Of course, the RV
spar has to be bigger, since the wing is cantilevered.

Tricycle Landing Gear

You're on your own for this one.  Mike Meador tells me "We will never
live to see the day Bob caves in to this."  That tells me that your
first problem would be to find a new name for your aircraft, since a
"Tri-Gear Bearhawk" or a "Tri-Bearhawk" or even a "Bearhawk-A" are all
oxymorons.  The next (and biggest) problem would be redesigning the
fuselage structure because the landing gear loads are now in totally
different locations.  Also, the tail would probably be over 10 feet
tall. Take a look at the Piper Tri-Pacer to get the idea.  Might be
tough to get in your T-hangar door as well.

Besides, if you are building a Bearhawk because of its STOL capabilities
or its ability to operate from grass or unprepared strips, there are
numerous reasons why a conventional gear (the proper name for a
"taildragger") arrangement is better, which I won't go into here.

If you're concerned that you don't know how to fly a taildragger, find
an appropriate instructor and go take some lessons.  You can learn
how--consider that virtually every pilot up through World War II learned
to fly taildraggers.  If they could do it, then you can too.

Wooden Airframe

This question has actually been raised.  Simply replacing the steel
tubes with similar sized sticks of spruce won't cut it.  Find a
toothpick and a similarly sized nail.  Try to break each one with your
hands.  Which one broke?  Which didn't?  Point made?

While it's true that large aircraft have been constructed of wood
(e.g. the Hughes HK-1 Hercules, a.k.a. the "Spruce Goose"), typically
they use a totally different construction method.  The DeHavilland
Mosquito used a monocoque or semi-monocoque construction where wood
formed the outer shell of the aircraft and this shell carried the loads,
much like the shell of an egg. The Corby Starlet fuselage is built from
sheets of plywood reinforced by a wood truss.  The majority of the loads
are carried through the skin acting as shear panels.  The primary
purpose of the truss is to keep the unsupported panel areas small enough
to prevent buckling.

Another type of wood construction uses a large number of stringers held
in place by wooden formers, covered by fabric. The Sopwith Camel was
typical of this type of construction (Many Fokker aircraft used welded
steel tube construction--Anthony Fokker was a pioneer of this method).
Most Guillow rubber-powered airplane models use the stringer and former
construction.

Both of these methods are significantly different from the method used
in the Bearhawk fuselage. Thus, choosing to change to a wooden fuselage
would necessitate designing an entirely new fuselage.  If you really
want to do that, you might as well design your own airplane.

Elimination of the Front Strut on the Tail

I'm not sure what would be gained by this. The left and right horizontal
tails attach to the fuselage by a tube slipping over a tube, held in
place with a bolt.  While this setup handles forces sufficiently well,
it doesn't handle moments very well.  It's actually rather similar to
the wing root, where the pin (bolt) carries the forces and wing strut
counteracts the moments.  The three struts on the horizontal tail keep
it from flapping up or down.

Because the horizontal tail is fabric covered and thus has no load
bearing skin, it is not exceptionally stiff in torsion. Therefore, two
struts are used on the bottom just as with a fabric covered wing.  Both
the forward and aft strut systems are necessary.  The forward strut is
large enough to take loads in tension and compression.  The aft struts
are thinner, but only need to take loads in tension because of the upper
and lower struts.  Removing any of these struts would compromise the
torsional rigidity of the tail.

All Aluminum Tail Feathers

You could do this, but you would be designing the whole thing
yourself. The structure would be much more like the wing than the
current tail feathers.  Aluminum tail feathers would definitely be more
complex, take longer to build, and might even be heavier.

All Aluminum Flaps and Ailerons

The only benefit that I could see for this would possibly be in a bush
flying scenario where the flaps and ailerons might frequently be hit by
debris.  Of course, by that same logic, you'd probably want to cover the
fuselage in aluminum too.  Even then, you're trading fabric tears
(temporarily repairs in an emergency with duct tape) for aluminum dents
(which may be more difficult to repair).  Aluminum covered flaps and
ailerons would be heavier, since the aluminum sheet is heavier than the
fabric.  The ailerons would also pick up additional weight because of the
increase in ballast required to balance them.

Wet Wings
 
While wet wings are doable, the increase in fuel volume would be
minimal, while the increase in complexity and building time and effort
would be very large.  You wouldn't be able to make the tank fill more
rib bays without significantly changing the load distribution and
redesigning major portions of the wing, such as the flap actuation
mechanism.

There are benefits of having non-integral tanks.  For instance,
fabrication and plumbing are easier.  If maintenance is required, such
as finding a fuel leak, the tank can be removed for inspection and
repair.

Skylight

Here's a change of pace--this one has actually already been approved!
See the April 1996 Bear-Tracks, where Bob said that the transparent
portion could be continued over the fuselage back to the rear wing spar.
The covering in this area is non-structural.

Of course, there is a down side to this--you will increase the sun
radiation load in your cockpit significantly.  In other words, it can
get HOT!  Take a flight with a buddy on a sunny day in a Long EZ, RV, or
any other aircraft with a bubble canopy.  You'll see what I mean.  The
point here is that you'll want to think about providing a sun shade for
those days when the sun is oppressive.

Stretching the fuselage

This will launch you down the path of redesigning the fuselage.  If your
idea was to increase the payload, see the previous discussion on
increasing the wing span.

Electric Flaps

Electric flaps are usually mechanized by placing a jack screw in place
of the flap lever.  This adds one more gadget to fail on you at the
worst time.  One advantage of electric flaps are that you can set them
up to be able to stop at any deflection.  Even so, with four positions
available on the manual flap lever, this benefit is minimal at best.  My
experience has been that manual flaps can be set to a different position
faster than electric flaps if desired.  You might find the faster manual
flaps a benefit if you like to retract the flaps quickly after landing
to "plant" the airplane on the ground.

So What Should I Do?

As you can probably see by now, your best bet if you don't consider
yourself an aircraft designer is to build your Bearhawk according to the
plans for the parts where the plans exist.  There are plenty of
non-structural areas and areas not specified in the plans, such as the
engine installation and the instrument panel layout, where you can
express your individuality with your own design, while still feeling
confident about the primary structure around you.  If you still feel
that the Bearhawk is not right for you without some major design change,
then maybe you should be building some other design.

+++ #203
Subject: *So You Want To Be An Aircraft Designer - COMMENT
From: Mike Meador

Bravo! Excellent!

OK - now with that article in print let me make a few comments:

1) Do not think that Bob is adverse to ANY changes in the airplane.  He
listens to everybody and will give design suggestions some thought.  You
may have a better way of doing something - we can't think of everything.

2) We always welcome questions and your phone calls.  It is fun to talk
to the builders and get an idea of how each project is progressing.

3) As Russ said - Bob left plenty of area in the drawings for you to
express yourself.  We doubt that there will be two planes built that
look exactly the same - even if they were built side by side.  Where
your changes will not affect a structural component - go ahead - do what
you want.

4) I will try to get this in Bear-Tracks - it may take an issue or two
but it covers a lot of good points that I think everyone should read.  I
faxed the article to Bob and we'll see what he thinks.

Thanks Russ for another of your enlightened post - you deserve a cookie
- help yourself!

As a side note are any of you planning on coming to the Bearhawk Fly-In
on Oct.  23rd?  We should have Proto II in the air - we are hoping that
we can get a weight and balance in the next issue of the newsletter.
Preliminary weights show that even with the Utility Door System (UTS)
and the O-540 and (GASP!)  electrical system the empty weight of Proto
II is around 1300+lb.  There are a few caveats to go with this number
but we were very pleased.  The real weigh in will occur in about 3
weeks.

+++ #212
Subject: Possible Bearhawk Mod.
From: bearhwk27-

Have another possible bearhawk mod that maybe Mike could bounce past
Bob.

Every time that I Fly and then park a Husky I am thankful for the hand
holds at the tail on the lower fuselage longeron and the front of the
horizonal tail. Have you seen them? Used them?  What do you think? Might
be handy on a larger aircraft like the Bearhawk.

+++ #213
Subject: Re: Possible Bearhawk Mod.
From: Float-by Shooter

> Every time that I Fly and then park a Husky I am thankful for
> the hand holds at the tail on the lower fuselage longeron and the 
> front of the horizonal tail.  Have you seen them? Used them?
> What do you think? Might be handy on a larger aircraft like the Bearhawk.

My brother's Citabria has a hand hold on each lower longeron in front of
the horizontal stabilizer, I was planning on the same setup on my
Bearhawk.  The only thing I will do differently, is make them a little
bigger so heavy gloves will fit in them better.  If you want I can snap
a picture, it is basically a "U" shaped piece of narrow tubing welded to
the longerons at the upper part of the U.

Actually that was my second choice, first choice was one of those
electric tugs like you see at FBO's, but.....

+++ #214
Subject: Re: Possible Bearhawk Mod.
From: Mike Meador

OK - This is a Mod that has been installed on Proto II - with an Alaskan
twist. During our trip to Alaska last year Bob noticed that a lot of the
homebuilts did have the handles but they were turned around - in other
words they were pointing down. Well the question begs "Why?" Turns out
that it is a handy resting place for the tail when you are working on
the tail wheel (they do that a LOT in Alaska) and that keeps you from
bending the stringers. It is also handy to strap a 2X4 back there for
flying a canoe in to that remote lake (I am in no way recommending this
- do it at your own peril).

You should be able to see the handles in the newsletters - well you can
barely make them out on the back page of Jan 1999. I'll see if we can
get a small write up and photo in the next newsletter. It shows up a lot
in the Fuselage photo pack - as a matter of fact photo #31 is just about
nothing but. I just shipped out 7 Fuselage Photo Packs Monday and
another 3 should go out in the morning - it is hard to keep up with the
demand (I'm not complaining).

+++ #360
Subject: The 400# Question
From: Mike Meador

400 Pounds - When you think about it - that is a lot of weight. Bob came
up with the 400 pound figure based on the heaviest aircraft engine that
is suitable for the design.  The conversion should not weigh more than
400 pounds.  That figure does not include the propeller.  Most
conversions that we see are HEAVY and bulky.  The Bearhawk will fly fine
with a lot of weight up front as long as you counter it with weight in
the back.  All this weight is cutting into your useful load.  Don't
think that a lot of horse power is going to make up for all that weight
- keep the conversion in the proper range (150 - 260).

With the O-540 design in Proto II the cg range is a bit too far forward
(we don't have the battery in place yet) for the first flight.  We will
put 50 pounds of lead in the baggage compartment for the first hop.

As for the one degree increase in the wing angle of attack, well it does
have at least one more degree.  Mostly that one degree is in the landing
gear.

The Bearhawk was signed off Tuesday by the FAA.  We should have the
first flight as soon as the weather breaks.  I'll let you guys know as
soon as it happens.

+++ #380
Subject: Re: Float Use & Engine Choices
From: Bruce A. Frank

>I am curious if anyone has identified a suitable set of floats to use
>for the Bearhawk yet.  Earlier iquiries this summer indicated no.

I missed that topic but certainly there are several certified type
floats that will work in the gross rating of the Bearhawk. As I have
said in other venues the Bearhawk is not a unique design. It has decades
of Piper rag and tube design in its lineage. Mods to the airframe to
allow fitting of floats range from simple to complex and all examples
can be found on Piper craft ranging from the J-2 to the PA-22. There are
also at least half a dozen float kit manufacturers that make straight
and amphib floats for gross weights from 2000 to 3000 pounds.

+++ #382
Subject: Re: Float Use & Engine Choices
From: Perry Delano

A project of interest with regard to floats might be Eustace Bowhay's
RV-6 (RV-6F) on Zenair floats, featured in the July 1994 issue of
Kitplanes and now even seen on Van's website "vansaircraft.com". This
was no haywire job and obviously took a lot of careful thought and
engineering. He is only now nearing the point now where they may kit the
installation for straight and amphibian floats. Eustace is a retired
high time pilot used to flying in the northern reaches of Canada and
deferred engineering on this installation to professionals. You can keep
up with developments by signing on to the RV builders site at
"www.matronics.com" and doing a search. Just food for thought.

+++ #407
Subject: Float Lift Points
From: Russ Erb

All right, all of you aqua-Bearhawkers...here's something important that
nobody has mentioned yet.

We've seen several mods in the newsletter to make for fitting floats to
the Bearhawk. Something I've seen on a Glastar and a Cessna 180 with the
float kit are lifting points (usually 4) on the top of the fuselage for
lifting the airplane up to swap floats and wheels, or just to lift it
out of the water.

I haven't seen such a thing in the plans, although it looks like it
would be a requirement.

Just a nudge to get ya'll thinkin'

+++ #408
Subject: Re: Float Lift Points
From: Float-by Shooter

> All right, all of you aqua-Bearhawkers...here's something important
> that nobody has mentioned yet.

It's there in the archives, I don't remember when though. Probably
before I joined the list. Another one to think about, is provision for
controlling the water rudders. There needs to be some means of
connecting them to the air rudder controls, plus means of raising and
lowering them.  I'm told you lose style points for forgetting to raise
the water rudders before takeoff.

+++ #479
Subject: metalizing
From: woodpre-

I have been sitting here reading the talk of Tig welding,the different
powerplants,and the wiring.so it lead me to thinking down the road and I
was wondering has anyone thought about metalizing a Bearhawk.I don't
have a hanger to store it in,and I havn't come up with any push-button
and there is your airplane shelter,so the metal seems to make sense
today.since I am not in a hurry to get the airplane done because on
minimal extra time.any thoughts,Sonny

+++ #486
Subject: Re: metalizing
From: Bruce A. Frank

>I have been sitting here reading the talk of Tig welding,the different
>powerplants,and the wiring.so it lead me to thinking down the road and
>I was wondering has anyone thought about metalizing a Bearhawk.

With all the stories of old fabric(cotten) and its deterioration there
has come into existance the belief that fabric covered planes don't last
when stored outside. If you keep the coating clean, waxed and repaired
if any cracks develop in the coating, the plane will last 20 years
before it needs recovering. THe ONLY thing that causes deterioration in
polyesther fabric is exposure to UV light. If the coatings are cared for
the fabric will be sound forever. If along the way you rejuvinate (dope)
or re-color coat when wear starts to show the fabric will last longer
than you want to go between strip down inspections of the tubing.

Then again, mounting tabs with nut plates would allow for relatively
easy covering with aluminum--wouldn't last any longer, but do-able.

+++ #566
Subject: Howzabout an Update on the Utility Door System?
From: Russ Erb

I was just reviewing the original words on the Utility Door System in
the October 1996 Bear-Tracks. At the time, Bob didn't sound very excited
about it, and was only offering it because we insisted.

More recently, Mike made a comment that the doors on Proto II turned out
a lot better than expected.

Now that Proto II has flown, I'm asking Mike for all of us to give us an
update on how the doors turned out. What, if any, disadvantages compared
to Proto I did you find from the doors? If they really did turn out
well, is Bob more excited about them now?

+++ #568
Subject: Cargo Door
From: Tim

I have the Big Cargo Door admendment...but that Big hole looks to me as
the weak link in the fuselage.....Thinking of the stresses in that area,
with a good pull-up/out......yikes.....but me only an eye-ball
Engineer...You real thing Joe.

Let me take a second look......Hey, hang on a second.....Think I have
two copies... stuck together here....wadya know.....  ;-)

+++ #572
Subject: Cargo Door
From: Rod Smith
 
The cargo door arrangement is very similar in size and arrangement to
the one that Maule has used for years with no problems. The only concern
I might have is about float reinforcement. Maule used to weld a steel
sheet with lightening holes over the entire lower sill area on the
inside to add reinforcement for floats. Later they dropped the steel
sheet and just increased tube thicknesses in that area. This weekend I'm
going over to the local Maule guru with plans in hand and look at one of
his uncovered fuselages. He has a very good idea of what is strong
enough in this area as he has rebuilt enough of them.
 
+++ #578
Subject: Re: Cargo Door
From: budd davisson

Someone send me a copy of the door plans and I'll take a look, as I'm a
structural engineer, although I'm absolutely certain Bob has it nailed,
as he is prone to err on the conservative side. To open up a bay in the
side for a door only requires a "K" member, which is nothing more than
pulling the diagnal down towards the corner and adding a short
stabilizing piece. Very common structure.

+++ #714
Subject: radial engine drawing
From: budd davisson

This may be redundant as I tried to send this earlier and nothing seemed
to go out. If it did go out, excuse me for trying again.

I've attached a jpeg of the radial engine Bearhawk I worked out a couple
years ago. I don't know if this is going to work or not, but one of you
is bound to be able to help me get this jpeg out to the rest.

There are some mods to the airframe of the 'Hawk to pull the radial
engine thing off and I haven't completely worked out all the details,
but it's an easier conversion than it looks. Bob has already looked at
it, so probably has some good input on it. Also, if I remember
correctly, I moved the tail back 10" for more tail volume and CG
balance. I'm not sure. I'd have to measure it.

If the jpeg won't make the corner through the group server, anyone who
really wants to see this should contact me at budd.goodnet.com. I know I
can send it to individuals.

Also, I'm going to be jealous if anyone actually does this. I wish i
could make the time to do it.

<Attachment - DesertHawk.jpg>

+++ #717
Subject: Re: Budd: Permission for posting?
From: budd davisson

> Budd--most cool sketch of the "Desert Hawk".  Even so, I think I'll
> still go with the original.  I always liked the skinny cowling top to
> bottom, which was very unlike the 172's.
> 
>  Can I have permission to post your sketch on my Bearhawk web page
> (with appropriate credits, of course)?  Del and Tom may be interested
> in doing that too.

Post away!

> I assume you thought about how you would beef up the structure, since
> you would be going above the 260 HP design limit.  Comments?

Not as many beef-ups as you'd assume because the weight isn't changing.
The primary beef ups I did involved a few minor changes in the side
truss to relocate the rear gear attach point because of the much taller
gear which requires a sub-truss inside the fuselage. That doesn't even
have to be done, if the beefing is restricted to the present attach but
it would involve some fairly heavy metal. I didn't do a finite elment
analysis of the wing, but because of the possible speeds, I might
consider going up a little on the bottom sheets but that would be all.
Bob's work is really quite good, even with this horsepower.

This airplane would be working in the same speed ranges he used for his
calculations so not much needs changing.

With this power, two people and half fuel, the power to weight ratio is
the same as a single-hole, big engine Pitts but the wing loading would
be the same as a normal, light Bearhawk.

FYI, at gross weights a 172 is wing loaded at 15 pounds while the 'Hawk
at gross is 13.3. That's where the airplane is getting much of its
performance because that's a HUGE difference. Now think about using the
Vendenyev. At 1900 pounds, the wing loading would be 10.6 with a power
loading of 5.3. The airplane would literally leap off the ground.
Besides the light wing loading and astronomical power loading, that big
prop would be "blowing" the inner wing panels, including the flaps, so
takeoff would be mind boggling.

If I keep writing this stuff, I'm going to talk myself into building the
airplane. Someone get me under control! Please!

+++ #723
Subject: Re: radial engine
From: Tom Kennedy

I saw some jack screws utilized on a Cougar elevator (Tailwind
knock-off) that could be incorporated into your Desert Hawk prototype.
You could then fine tune the elevator incidence angle, if necessary,
without having to perform any structural changes. The additional weight
could also provide CG ballast.

+++ #921
Subject: Slats
From: Tim Anderson

Well, nose rib #1 is complete (sort of).  Now it's time to EXPERIMENT.
My diversion dicussion topic for the day is "RETRACTABLE LEADING EDGE
SLATS" Those of you that have seen a Helo Courier, or had the pleasure
of flying in one, you'll know what I mean.

They Are AWESOME.

I figure I'll simply take the existing nose rib template, make a few
cuts, make a stiffener bracket behind them, install some pushrods and -
Presto - retractable Slats.

A bearhawk that can T/O in 100 ft fully loaded, stall at 15 MPH.  Ha

Actually, they would be nice.  Maybe after I get the airplane flying in
10 years or so, I'll make a second pair of wings with retractable slats.

+++ #923
Subject: Re: Slats
From: budd davisson

Having flown a number of slat-equipped airplanes and being an aero
engineer, I can say they might be nice, when right, but getting them
right ain't easy. The best I've flown were the Messerschmitt 108. You
couldn't even feel them coming and going. The Helios tend to bang more
and are a little abrupt.

with a 260 and 20 knots of wind, a lightly loaded bearhawk will probably
get off in 100 feet without the slats.

Now, VG's that's an entirely different discussion. Also those little "T"
shaped things they put on the Glass Stars really work. I flew it before
and after they put them on and it was an amazing difference.

Great! Discussions of slats and VGs and I haven't even started cutting
metal yet. First things first.

+++ #925
Subject: Re: Slats
From: Tim Anderson

A friend put VG's (homemade little angles) on his sportsman 2 +2, and
they made it almost stall-proof. he said it just got "mushy"

The Helo slats did scare the _ _ _ _ out of me when they magically
"deployed" at around 60 or 70 Kts. One wing slightly before the other at
that. We were fully loaded, four adults, plus about 400 lbs of gear,and
a good load of fuel and that airplane (on floats) did amazing things.

+++ #926
Subject: Re: Slats
From: budd davisson

Re: Helo's 

The Helo can do amazing things but they scare the hell out of me on the
ground. It has to be one of the worst ground handling airplanes ever,
with the gear so far forward and CG so far back. I hate that part of it.

+++ #929
Subject: CG/taildragger
From: budd davisson

As you run the CG back on any taildragger, in relation to the main gear,
it has narrower right/left envelope it must stay in for control. In the
case of the Helo, they've driven the main gear far forward so you can
stand on the brakes. As long as the CG (i.e. tail) is directly in line
with the ground track, it's okay, but once it starts off, it really
wants to keep going, so you have to stay right on top of it. The
Bearhawk is nearly a no-brainer in that department.

+++ #934
Subject: Re: Slats
From: Tom Kennedy

I've looked into VG's and it appears that most vendors offer custom
installations for specific aircraft and or airfoils.

Is their any chance that an individual could perform a DIY installation
on something like a Bearhawk?

+++ #935
Subject: Slats
From: Russ Erb

The smartest thing you said was that you would do the slats on the
second set of wings.  I can fully agree with the idea to first get a
good flying airplane, then start experimenting.

The best example of slats I have seen are on the T-39 and F-86.  They
were segmented and had many many supports and ball bearing rollers.  The
only way to tell when they moved was to look at them.

The same pilot told me about slats on the A-4.  Absolutely terrible.
Just about every A-4 pilot has a story about uncommanded roll in the
final turn as one slat came out and the other didn't.  The biggest
problem was binding as one end of the slat tried to come out faster than
the other.

The down side of this would obviously be the increased weight and
complexity.  What do you see as the benefit?  When the Bearhawk already
will fly slower and take off shorter than most other aircraft, what is
the benefit of making it more so?  Do you plan to fly out of 100 foot
strips?  Or are you just proposing an idea to see if it can be done?

+++ #936
Subject: Re: Slats
From: Tom Kennedy

To http://www.microtec.net/dedalius/ for a look at automatic slats.

+++ #939
Subject: Pega Stol Wing
From: Rod Smith

> To http://www.microtec.net/dedalius/ for a look at automatic slats.

A little history on the Pega Stol wing shown at this website. This wing
was designed for the Pegazair aircraft which is a French Canadian, small
two seater. Its stall speed at its 1300 lb gross is something like
18mph. There is one flying in Fairbanks, Alaska. I have talked with the
builder but haven't yet caught up with him for a flight. If you do the
calculations you come up with a very high coefficient of lift for this
wing arrangement. I calculated what this wing, scaled up for the
bearhawk would do. I dont remember exactly but the stall would be in the
low to mid 30s at BH gross. For the person that wants to get into the
places that few Super Cubs dare to go this might be the direction to
pursue. The downside is cruise. The Pegazair cruises at 85mph with
100HP. The full span slot between the wing and flaperons adds a huge
amount of drag at cruise speeds. I was really intrigued by the Pegazair
but it was just way too small. The Bearhawk has such a nice balance
between short field performance, load hauling capability and reasonable
cruise speed that it is hard to beat for total performance. Even the
Helio with the 400HP engine cruises slower than a 260HP Bearhawk
will. There is no free lunch in aviation.

+++ #940
Subject: Whitman's Buttercup
From: Bill Cox

Did you ever get the opportunity to fly Steve Whitman's Buttercup? It
had a very simple manually retractable slats and Steve claimed some
amazing performance. There is a fellow currently building a copy of it
and I believe he intends to offer drawings once he gets it going. Steve
was in the process of building a similar wing for the Tailwind at the
time of his death, but I don't believe anyone is finishing that project.

+++ #941
Subject: Re: Slats
From: Tim Anderson

All I know is what I saw.  They were full span, and where mounted on
rods that obviously were on rollers in the wing.  On the ground, and up
to a certain airspeed they hung down, and then at about 60 or 70 Kts,
pushed themselves back in.  They also popped out when you slowed down.
I believe the Helo company was based in Canada and I'm not sure if they
are made anymore.  I tried to find a Website once and struck out.  The
helo was easy to spot on the flightline because it had a huge rudder,
good for float flying where one needs a lot of rudder authority.

I seem to recall the Murphy line of kitplane had Fixed slats.

+++ #942
Subject: Re: Slats
From: Tim Anderson

If I made a second set of wings (and the question is "IF" and "when") I
would not make the slats deploy/retract themselves.  I would go a route
simular to how the flaps are deployed with pilot controlled pushrods.

Why?  (The million dollar Question) The bearhawk seems to be a VERY VERY
capable airplane.  But for EXTREME bush use (which I may return to
someday) one needs to conserve every Foot of help.  especailly at full
gross wt.  If you have a gravel bar that's 300 ft long and you need 325
ft, your sunk or in the trees.  And that 300 ft gravel bar may be the
only place to land.  I'm not referring to an emergency landing, I'm
talking about flying in to your favorate fishing or hunting spot (which
can be very important to you, or not important at all) How much
advantage does one gain is the big question, vs the complexity.

The VG's seem be a much easier option, with minimal risk.

+++ #943
Subject: Re: Whitman's Buttercup
From: budd davisson

No I never got into the Butter cup, which was a milestone airplane, even
though it really didn't lead anywhere. Wittman was one of the true
geniuses of our time. I spent some time with him, which was barely
enough to convince me he was an absolute one of a kind in every area, as
an engineer, pilot, human being. I never got a chance to inspect his
slats, but like all the rest of his designs, they would be crudely
innovative and work like stink. No one could do red neck engineering as
well as he could except maybe Curtis Pitts.

+++ #944
Subject: Re: Slats
From: budd davisson

A note on slats, etc.

I spent a fair amount of time flying the Sherpa (which doesn't have
slats) and hanging out with its designers and I learned a terrific
amount about serious bush flying. I'd flown a lot of bush before, or
thought I had, but I hadn't. We did stuff you wouldn't even attempt in a
Super Cub. Only a helicopter would match it. We thought 200 feet was
plenty, as long as the boulders weren't much bigger than basketballs.
Really!

The key to bush is lots of power, lots of wing and really good flaps AND
the ability to see the touchdown point right to the ground. Helios are
lousy at that: you can't see over the nose, if really slow and have to
trade speed for visibility. The name of the game is hit the spot as
slowly as possible. Ideally, you do it as the Sherpa does, with a
minimum amount of power required, rather than riding the throttle down
final. Also, a really tough landing gear is necessary. Another keyis
reliability which is another way of saying simplicity.

I'd like to see the Bearhawk have good, slotted Fowlers, but the barn
doors it does have are probably a good trade off because they build so
easily. Also, don't forget that with a big engine you are really blowing
that section of the wing while accelerating. The flaps are probably
ready to fly the airplane almost as soon as you're rolling and are just
waiting for the rest of the wing to catch up. If we get the Desert Hawk
in the air, with the big prop and thrust, the blown wing/flap effect
should be VERY noticable.

If I was going for super bush with the Bearhawk, I'd probably go with
VGs and a slightly longer wing (with appropriate beef ups). However, if
you're going into areas the present Bearhawk isn't able to get into, you
probably shouldn't be there in the first place. Get it flying, tinker
with VG's THEN decide if you really do need more. I doubt if you will.

+++ #945
Subject: Auto SLAT's
From: Tim Cramb

Guy's below is the page from the site Rod mentioned.  It's a Quebec team
of tinker-er's.....This Pegastol design is a Chris Heinz ripp off,
although they have put much more 'thought/follow through' into the
wing...Something Heinz isn't noted for.

Look at the wing tip photo and you can see how the flaps contour into
the L.Edge....Look's very Aerodynamic <(Big word for 'Go Fast').

http://www.microtec.net/dedalius/Document/Ailes_A.html

+++ #946
Subject: Re: Auto SLAT's
From: Stephen Wolfe

So- if the slats deploy on one side and not the other, or deploy
unevenly, do you eat dirt?

+++ #947
Subject: Dirt Devil...???
From: Tim Cramb

Eat Dirt....?.....One of our club members did, last summer in a Soob
powered 701.  This machine had the fixed slat's and he stalled it.  The
Pegastol A/C if I read correctly, has 4 auto slats which work
independantly "WHOOPIE!" So in answer to 'Eat Dirt'.....I haven't the
slightest.....Sounds like a query for Test Pilot Budd!

+++ #948
Subject: Re: eating dirt
From: budd davisson

I'm no expert in slats having flown maybe four different light airplanes
airplanes with them. They ranged from independent, free minded units to
coupled, if one moves, they all move types. On at least two occassions
while playing with yaw and slow I was able to get one to retract faster
than the other and it did pretty much what you'd expect; I got a little
uncommanded roll, but nothing the ailerons couldn't handle. As I
recollect, A-4's loved to stick one out and one in. In fact, a navy
friend of mine spun one with one out and one in, but by playing with yaw
rates got the other one in.

Russ can probably pull some knowledge out of Edwards, but I'd be
surprised to find an airplane that is uncontrollable with assymetric
extension. It would be irresponsible to design an airplane that couldn't
be flown with that kind of malfunction. As an engineer, besides trying
to come up with problem solutions, the thing that's always in the back
of your mind is failure modes; what happens if it doesn't work? I'm
primarily a structures type, but I'll bet the aerodynamic guys work the
same way.

+++ #949
Subject: Re: eating dirt
From: Russ Erb

Someone mentioned a key point a few messages back, but it may not have
been clear. I'll try to steer clear of the engineering terms to make
this clear.

Flaps are wonderful high-lift devices, but primarily not because they
let you fly that much slower. I've noticed over the years that flaps
typically will reduce stall speed only by 5 knots or so. However, the
biggest benefit of flaps is it lets you fly at that very low speed with
a lower pitch angle. Try this in a 172 or other airplane with effective
flaps (Piper Traumahawks need not apply). Fly in level flight at slow
speed and note your pitch attitude. Now put the flaps full down and fly
the same speed level. Your nose will be much lower. The point here is
that with large flaps, you can SEE that sand bar you're trying to land
on, rather than it being hidden below the nose. I remember the Twin
Otter (UV-18) having a very pronounced nose down attitude with full
flaps out.

On the other hand, slats and leading edge devices will let you fly
slower, but by allowing you to fly to a higher angle of attack, which
will generally result in a higher pitch angle, making the aimpoint that
much more difficult to see.

+++ #950
Subject: One more on slats
From: Russ Erb

One last thought that passed through my mind...

Slats are going to be most effective at lowering your landing speed, but
may have little to no effect on your takeoff speed. Slats work by
allowing you to go to higher angles of attack. If you are below the
no-slat stall angle of attack, the slats do nothing extra for you. On
takeoff, your liftoff angle of attack is limited to the angle between
the wing and ground in the 3-point attitude. The only way to increase
that angle of attack is to change the landing gear or wing incidence
(neither recommended). Flaps can lower your takeoff speed.

+++ #955
Subject: Slats, VG and Flights of Fantasy
From: bearhwk27-

Slats, VG may have there purpose somewhere but for the vast majority of
us builders the capability of the aircraft is most likely greater than
our piloting skill. Slats and VG allow an aircraft to perform better at
the edge of the envelope and can remove some cushion from the edge.
When the flying is over its over. Not the best situation for low
proficiency.  For most builders / pilots the issue should be: How can I
best safely operate my aircraft and what can I do to improve my skills
at the edge of the envelope?  What techniques can I incorporate to
minimize ground distances?  What can I do to maximize climb performance?


( I vote, build the thing, learn to fly it, then VG if needed.)

+++ #956
Subject: New member
From: george velguth

I've been a Bearhawk plans owner for a few years now - #278 - and I've
just dusted off my drawings and am getting serious about starting to
bend metal. I wanted to weigh in on this issue of slating a Bearhawk
wing.

My first thought is my experience suggests that it simply is not
necessary. I owned a C-172 on floats for about four years. This airplane
had a 180 HP engine and constant speed prop, and a Bush STOL kit
consisting of a leading edge cuff, stall fences, slightly drooped wing
tips and aileron and flap gap seals. I routinely flew this machine in
and out of some incredibly tight bodies of water. I have to believe that
a Bearhawk will do as well, probably better, since most will probably
have bigger engines that my 172 had. It is my feeling that some
tinkering with VGs, wing tips, stall fences, etc. will yield scary short
field results and make a complex undertaking like slats impractical.

A few years back there was an article in Sport Aviation about a fellow
who'd tinkered around with the wing of a C-150. He'd stuck all sorts of
Vgs on it, installed a radical wing tip and extended the flaps. The
result was some unbelievably-low takeoff and landing speed. The point is
that some pretty impressive performance gains can be had with simple
modifications.

+++ #963
Subject: Re: Slats, VG and Flights of Fantasy
From: budd davisson

Kevin hit the nail on the head about the VG/Slat thing: This airplane is
more than just about everyone reading this needs, especially with a 540.
The best bush planes I've flown were those which required no special
techniques to extract max performance out of them and were very honest
and forgiving at that point. None had anything more than big flaps, bit
wings and big engines. Pushing a wing to give super performance
sometimes sharpens up what would be an otherwise blunt lift curve giving
an airplane bad habits when it had none at the beginning.

If you learn to fly this airplane as well as it can be flown, only those
who are working a true bush environment are going to want more, and
that's not very many of us. But then, they ALWAYS want more.

+++ #967
Subject: Re: Slats, VG and Flights of Fantasy
From: Float-By Shooter

I'll try to keep this short since I'm not a bush pilot, though some of
my friends are. A large percentage of the fleet in this area is used for
bush work, and consist mainly of super cub variants, a scout or two, and
Cessna 170/180/185/206 and of course dehavilland beavers and otters
(single). A lot of the cubs will have heavy duty landing gear, and
modifications allowing more power/gross weight, and sometimes squared
wing tips and things like that. The larger airplanes aren't modified
nearly as often, other than maybe hanging a larger engine/prop.

The key seems to be pilot skill; these guys do it day in and day out
during the warmer season. A friend of a friend supposedly took his
mostly stock 150hp cub to a bush piloting competition, and beat a lot of
heavily modifed cubs in the spot landing competition (I understand this
was less than appreciated).

Don't get me wrong, I have learned a great deal from the discussion on
slats and other stall delaying devices, but I think 168 ribs are enough
for anybody to make. One of my buddies has been threatening to get his
CFI and I think I'd be better off to just get as much dual with him as I
can manage. For those who do not read the rec.aviation.homebuilt forum I
submit the following pictures of him:

http://www.netpackrat.com/planes/avpix/boog.html

+++ #968
Subject: Re: eating dirt
From: Archie Dunbar

I have many hours (1200 or so) in A-4's.  The usual scenario for getting
asymetric slats was; 1) rapid increase in angle of attack, 2) yaw.  In
fact on a PMCF (Post maintenance check flight) we would try to induce
this to check the operation before doing a rate of roll check with the
hydralics disconnected.  It was kind of critical that everything work
properly before doing this as they could not be reconnected until you
got back on the ground and the control forces without them were
extremely high.

Any way, the slats worked well most of the time.  As long as you kept
the yaw out, you could play the angle of attack and watch the slat cycle
in and out in your canopy rail mirrors.  They were mounted in roller
bearing tracks, worked very smoothly and would operate aerodynamically
to any position dictated by the current AOA.

+++ #992
Subject: Utility Door System Plans
From: Russ Erb

I received the supplementary plans for the Utility Door System a few
weeks ago. In case you're wondering, Bob has done an outstanding job
again. I'm very impressed by the numerous little details that are
covered simply and elegantly. The baggage door is held closed by pins at
the top and bottom.  The "rear" door (the one between the front door and
the baggage door) is held closed by a pin into the baggage door. The
part I found most delightful and slick is that the design of the door
latches makes it impossible to close the rear door until the baggage
door is properly closed. Very slick.

+++ #996
Subject: Re: Utility Door System Plans
From: Float-by Shooter

> held closed by a pin into the baggage door.  The part I found most
> delightful and slick is that the design of the door latches makes it
> impossible to close the rear door until the baggage door is properly
> closed.  Very slick.

And the fact that the baggage "suicide door" (rear hinged) isn't going
to be opening until after the rear door is opened!

I think that the cargo door plans would be a worthwhile investment for
anybody, even if they are not planning on including it in their plane.
A lot of the features should be applicable to the main doors and the
detail is considerably better than the newsletter door instructions.

On the subject of doors, is anybody else thinking of installing one-
piece upward opening "seaplane" doors?  I'm not sure yet how difficult
it will be to clear the strut, and you would (probably) lose being able
to open the windows in flight, but I think it would be worth the
sacrifice for ease of entry and exit.  And of course it would make
walking forward of the strut much easier on floats.

+++ #1002
Subject: Re: Utility Door System Plans
From: Tim Anderson

I have not had the pleasure of seeing the BH in person, but your
observation has been in the back of my mind also.  My Kitfox has the
one-piece upward- swinging door and I loved that feature when on
floats. (The strut is behind the door also) If the door were to hit the
strut, one could make a modified super-cub version two piece (one down,
one up).

+++ #1006
Subject: Re: Utility Door System Plans
From: george velguth

> RE: "On the subject of doors, is anybody else thinking of installing
> one-piece upward opening "seaplane" doors?"

I, too, thought immediately of upward-opening doors.  I haven't done the
measurements to see how much strut interference there would be, but I
seem to remember the prototype having a small hinged section in its
doors which articulated to clear the strut, so absolute clearance has
not been established as a precedent.  I also don't think the loss of the
upward-opening window is a foregone conclusion.  For what its worth,
though, the door on my 172 was no obstacle when it came to quicky
getting out onto the float and ahead of the strut.  The critical step in
docking - aside from not hitting the dock - was getting the pilot seat
back far enough that you didn't snag your feet on it and end up hanging
upside down.

+++ #1007
Subject: Re: Utility Door System Plans
From: Float-By Shooter

> I, too, thought immediately of upward-opening doors. I haven't done
> the measurements to see how much strut interference there would be,
> but I seem to remember the prototype having a small hinged section in
> its doors which articulated to clear the strut, so absolute clearance
> has not been established as a precedent.

I think I'll probably wait until I have the fuselage welded up and the
wings mounted before I start worrying too much about it. I think it
would be neat to try to integrate any hinged panel that would be needed
for clearance, with the latch mechanism, but I'll have to wait and see
what is needed.

> I also don't think the loss of the upward-opening window is a foregone
> conclusion. For what its

I thought about it some more last night, and I think I would split the
side window into 2 pieces. The front section would be fixed in place,
and the rear would slide forward in its channels, inboard of the front
window and overlapping by enough to prevent leakage in flight
(hopefully). If you wanted to be really slick, locate the inner door
latch where it can be reached through the window and dispense entirely
with the outer door latch. Cement a small piece of plexiglass in the
rear corner for a handle both inside and out. Just like my old MG. 8^)
The flap handle is similar enough to the handbrake lever, that I ought
to feel right at home in the Bearhawk, by pretending the second set of
seats doesn't exist.

+++ #1008
Subject: Re: One piece doors
From: budd davisson

Re: one piece doors

I've drawn a set of computerized plans for the Bearhawk to work out
stuff on my own airplane and doing a quick and dirty examination (I can
actually swing the door open on the computer) it looks as if the strut
will interfere only about 3", may be 4". A little cut out with a spring
loaded flap, similar to the way the back corner folds on Bob's own
doors, will do the trick.

As for windows, just hinge them at the top, ala Cessna and make sure
they are closed when the door is opened.

Or hinge them at the bottom, ala L-5 Stinson, so they fold down and clip
flat against the outside of the door and you can cruise with your elbow
on the sill. Just make sure the latch is flush enough it doesn't hit the
wing should you forget and open the door with the window open.

+++ #1027
Subject: Re: One piece doors
From: george velguth

> A little cut out with a spring loaded flap, similar to the way the
> back corner folds on Bob's own doors, will do the trick.

Are you planning to hinge that little cut out in both directions? If
not, how will you re-close the door once its been opened past the point
of strut interference? Perhaps, instead of spring loading the cut out,
it could be mechanically opened, and held open, by the door latch
mechanism.

> As for windows, just hinge them at the top, ala Cessna and make sure
> they are closed when the door is opened.

My thought exactly, no need to sacrifice the cool,
upward-openeing-in-flight window to gain an upward-opening (in-flight?)
door.

+++ #1028
Subject: Re: One piece doors
From: budd davisson

Re: door cut out

Details, details! I forgot about it needing to swing both directions. If
it doesn't interfere with getting in and out, how about having a
matching lump, maybe rubber, on the door sill and forgeting about the
flap?

+++ #1029
Subject: Re: One piece doors
From: george velguth

The simplest solutions are usually the best, and I think you've come up
with the best one here.  (Why didn't I think of that?)  I see no reason
why a small hump in the bottom of the door frame would interfere with
entry/exit, it would almost certainly exist entirely below seat cushion
height, plus you'd have a unique little gizmo that would get noticed.
Then you could proudly say, "Its a little modification I came up with to
address an oversight in the plans."  Oohs and aahs cascade from the
adoring crowd.

+++ # #1043
Subject: Re: One piece doors
From: robert gaddy

> Are you planning to hinge that little cut out in both directions?

I was thinking that one could hinge the little flap in each direction,
and spring load it to the extended position(in same plane as the
door)position. I fitting on the strut could have a "rub rail" to help
the flap over the strut, in both directions. When opening the door, the
flap would hinge one way and spring back to the orginal positon, and
when closing the door, it would hinge the other way.

Another way is to invent a linkage operated flap. A cable could be
connected to the fuselage in such a way that the flap would be swung up
when the door is opened such that sufficient clearance was available as
the door cleared the strut. The linkage should be such that the little
flap is full up when the door is full open (full forward against the
engine cowl for amphib ops).

I don't think I would select the "bump on the door frame" method unless
it could be removed as the seats are folded forward for entry into the
rear seat area. This would be easily done, however.

What about the addion of a boarding step for the rear seats that would
accommodate this cut out area?

+++ #1049
Subject: Re: One piece doors
From: Float-by Shooter

> I was thinking that one could hinge the little flap in each direction,
> and spring load it to the extended position(in same plane as the
> door)position.  I fitting on the strut could have a "rub rail" to help
> the flap over the strut, in both directions.  When opening the door,
> the flap would hinge one way and spring back to the orginal positon,
> and when closing the door, it would hinge the other way.

I think I like this solution the best.  Instead of using springs to hold
it in place, maybe some light bungee cords under tension.  It might take
some trial and error to get the right amount of tension that will allow
the flap to move easily for opening/closing the door, yet not flap
around in flight, but no big deal.  It should also be easy to make it so
the bungees aren't visible when the flap is closed.

> Another way is to invent a linkage operated flap.

I thought about this too, but I think it would be a lot more complicated
than necessary.

> I don't think I would select the "bump on the door frame" method
> unless it could be removed as the seats are folded forward for entry
> into the rear seat area.  This would be easily done, however.

I think that is what some of the 180/185 operators do, but I don't like
the idea at all.  Just one more thing to snag on while I am getting in
and out, and if something can be snagged on, I *will* eventually find
it, usually in a painful manner.  I'd rather stick with the standard
doors than put a bump on the door frame.
 
> What about the addion of a boarding step for the rear seats that would
> accommodate this cut out area?

Add the cargo door option and you won't have to worry about rear seat
passengers crawling in over and messing up your front seats.  8^)

+++ #1051
Subject: Re: Door Flap
From: bearhwk27-

I have been looking at that little door flap issue for quite a while and
have resolved it down to making the whole bottom half of the door just
lift out, climb in,drop in and go.  In a pinch the door can double as a
cutting board, snack tray or an oar.

+++ #1053
Subject: Re: One piece doors
From: Tom P.

Have any of you seen the Cirrus SR20 door?  It opens both up and out.
It's top hinge is a rod end bearing, allowing it to pivot out and up.
The bottom hinge is also a rod end bearing, but it's attatched to a
shock (gas?) strut that's attatched further back on the inside of the
door.  On a Bearhawk, this would allow the bottom of the door to clear
the wing strut and totally eliminate the need for a flap/bumper/etc.
Take a look at the Cirrus next time you're at Sun n' Fun or Oshkosh.

+++ #1058
Subject: Re: Door Flap
From: budd davisson

Don't over complicate the doors unnecesarily guys. If necessary, make a
modified Cub door, with the bottom half being just narrow enough to fold
down. You only need about six inches to allow the rest to fold up and
clear everything.

Incidentally, Clipped Cubs have an interference where the bottom door
half hits the strut because of the different strut angle when clipped.
To allow the bottom door to fold all the wy down , you cut a notch in
the top of the bottom door and have a fixed flap on the bottom of the
top half that covers the gap, when closed.

Or, if you want to do something unique: put a sliding track on both door
posts, split the door in the middle and hinge it so it goes up like a
bi-fold door.

I'm leaving mine the way God and Bob intended as mine will never have
webbed feet.

+++ #1063
Subject: fuselage width
From: george velguth

I seem to recall reading - perhaps it was in the original Sport Aviation
article - that the Bearhawk fuselage could be widened 2 inches and a 182
windshield used. I'm wondering if anyone has done this?

+++ #1064
Subject: Re: Door Flap
From: Float-by Shooter

> Don't over complicate the doors unnecesarily guys. If necessary, make
> a modified Cub door, with the bottom half being just narrow enough to
> fold down. You only need about six inches to allow the rest to fold up
> and clear everything.

I think I have (in my own mind, anyway) a solution that would not be
much more trouble to install than Bob's moving flap, using the bungee
cords like I mentioned last night.  If I get some time maybe I will draw
it up so that other people can look at it.  The only thing that worries
me now is weathersealing a flap that goes both ways, and as a result
doesn't have anything to rest against.

> Or, if you want to do something unique: put a sliding track on both
> door posts, split the door in the middle and hinge it so it goes up
> like a bi-fold door.

I had an idea that might be similar to that (I'm not sure I understand
what you are talking about there).  Hinge the door normally at the top,
and split it horizontally in the middle, below the window.  Put a piano
hinge there, so the bottom of the door could swing inward to avoid the
strut.  There would have to be some sort of device (like a cable of the
right length inside the door so it would be invisible) to limit how far
down it swings so people don't bang their heads on the doors getting in
and out, but it might be workable.  One benefit would be that since the
standard doors could be modified to this configuration, one could wait
until after the plane is flying before experimenting with the doors.

+++ #1065
Subject: Re: Door Flap
From: Bob Marek

There were a couple of guys that were building a Bearhawk near me that
hung the door from the top.  They then put an hinge in the middle on the
inside, so when they opened it the bottom half would fold under the top
half.

+++ #1083
Subject: Re: fuselage width
From: Rod Smith

I talked to Bob about this probably a year ago. As I recall he said you
can go 1" wider using the 170/172 windshield. I plan on building mine 1
1/2 " wider and using a 182 windshield. My reasoning behind this is the
Bearhawk is the same width as my Maule was. I was always cramped in that
while winter flying with a friend, both of us in parkas. For most
purposes it is probably wide enough. Another option would be installing
bubble windows on the front doors, they provide great visibility
straight down also. Probably best to call Bob and get his latest
thoughts on this.

+++ #1087
Subject: Re: Newsletter Info
From: Tim Cramb

Roger your last......Tell Bob thanks!.........If Bob is thinking of
building yet another BHawk #3......How bout a wider cabin on the next
one.....I sat in my brother Dean's Coyote/Bush hog and at 47.5" wide
(true inside measurement) it is an experience that you can't
forget.........For men of Stature, truly an orgismic experience ;-)

+++ #1099
Subject: On widening the fuselage
From: budd davisson

I ran into an interesting thing yesterday while flying the Aviat 110
Monocoupe Special that might be worth investigating on the Bearhawk.

Monocoupes are REALLY tight. I didn't measure it, but it must be around
36 inches across and tapers quickly towards your feet.

The airplanes have always had a metal fairing sticking out from the
front door post to which the sheet metal attaches. The original door was
about that thick. What Aviat did was build a new door that is barely an
inch thick and hinge it at the top with a nitrogen-assist cylinder
(which works really well, by the way). The point of all of this is that
there is a 1-2" step outwards at the door post because the door no
longer occupies the space. The result is that the cockpit is at least
three inchest wider because your hips and shoulders can stick out into
the space where the door had been.

On the 'Hawk, the .035 stand-off sheet that holds the boot cowl at Sta.
B-P could be extended upwards to the top of the fuselage and the door
hinges could be moved out an inch or so on each side. The exact
dimension used would probably be determined by the width of a 182
windshield at that point. The stand-off at Sta. D-N would have to be
similarly modified. The effect would be the same as widening the
fuselage, in terms of shoulder and butt room. Aviat used the vertical
panel formed at the front door post to mount some switches and phone
jacks (which is a really vulnerable location for jacks).

Just a thought. 

+++ #1584
Subject: Re: 'OTHER' Prototype II 'SKYLIGHT'
From: Mike Meador

> Did.....Bob end up putting an overhead skylight in Proto II?...If so
> was it much of a job???

No Bob did not put the skylight in - we really don't need it out here.
As for that "Homo Homebuilt" comment - what can I say HOMOsapiens have
to build the homebuilts so I don't view that as a Freudian slip.

+++ #1615
From: Float-by Shooter  <packrat@c...> 
Subject: [Bearhawk] Re: Mike - Rough field modifications 

> Living and flying in Alaska, I would be willing to add a few pounds to
> my Bearhawk's weight or loose a few MPH off of my top end if it meant
> an increase in rough field durability.  I realize the best rough field
> durability a aircraft can have is the pilot's technique, which is why
> I am so interested in beefing up my Bearhawk.

One thing which has been on my mind lately was suggested to me by a
local Super Cub pilot I know.  He told me about an STC'ed modification
he is planning to add to his Cub, available from F. Atlee Dodge which
involves boxing the area where the tailwheel mounts.  Basically you buy
the box structure already welded up, open the fabric enough to get it in
place, and attach it with hose clamps.  Then at your next
rebuild/recover, it is welded into place permanently.  He also suggested
leaving the boxed area uncovered, which creates more drag (which as a
cub pilot he isn't terribly concerned about) but would make it very easy
to inspect this area for cracking at preflight.

The person who suggested it to me isn't a mechanic or anything, just a
very skilled bush pilot.  I'm not planning on taking my Bearhawk into
the kinds of places he goes, but I thought I would pass the information
along, especially to anybody who was thinking of using a tapered rod or
tube spring to help prevent side loads, since something similar may be a
easier solution if you can live with the weight gain.  If and when he
makes the mod to his cub I will try to get pictures if anybody is
interested.

He had another tip to offer which makes perfect sense but might not
occur to non-bush pilots (like me).  When turning around in a
particularly rough area, he gets out of the plane, lifts the tail and
physically points it in the direction he wants to take off, saving a lot
of wear and tear on the tailwheel area.  With the engine left idling,
the propwash over the tail surfaces makes this easy.

+++ #1618
From: Budd Davisson  <budd@g...> 
Subject: [Bearhawk] Re: Mike - Rough field modifications 

Re: rough field use.

One of the BH's weak spots in really rough field use is the shock
absorbing system although, in reality, there is no perfect system for
really rough work because you want it to displace and soak up the
shocks, but it has to come back to neutral and "recock" itself amost
immediately to be ready for the next hit. If it's slow coming back to
center, it can't absorb the next hit becauswe it's already partly
displaced and if it snaps back too fast (like on bungees) it has too
much rebound. The BH shock strut is a good compromise, but could
probably stand to be another 1/4" in diameter for serious work. The
Sherpa people solve the instant-recock, soft-rebound thing by putting a
large diameter, short stroke shock at the end of their bungee mount so
the gear can come back quickly, but can't snap back.

I'm going to sleeve the longerons in the area of the landing gear
fittings going back about three stations with at least .063 and will put
finger gussets (not triangular gussets) on most of the joints in that
area. I may also go up a wall thickness on the rear gear leg as thats
the one that really catches hell from the spin-up loads of big tires.

If not using a tapered rod tailwheel spring, I'd also suggest boxing and
finger gusseting the last bay where the tailwheel mounts. Dodge sells a
lot of those kits because Super cubs are always breaking back there.

I'll bet the big secret, however, is running about 5 pounds of air in
31" tires. Then, except for the spin-up loads (which are monumenta as
each tire weighs 44 pounds!!), most of the airplane doesn't know it has
hit something hard.

Them's my thoughts

+++ #1619
From: Rob Gaddy Zippydogg  <Zippydogg@a...> 
Subject: [Bearhawk] Re: Mike - Rough field modifications 

Just wondering, Has anyone used large tires that have come available for
use on ATCs and Sandrails on a bush aircraft. I was thinking that the
lightweight aluminum wheels could also be used, using lug nuts to attach
to an automotive type spindle. Brake calipers from ATC, motorcycle or
light car could be used.  Maybe a weight savings, definitely an increase
in convenience with the lugs, and perhaps a cost savings depending on
equipment used and machine shop usage to make parts.

I run a sandrail with 14 inch wide wheels with sand tires; all in all,
they are very light. My sand car weighs about 1,500 lbs, and is more
abused than an airplane would be by jumping, running down washes,
etc. Also the tires absorb about 200 HP from a turbo motor.

+++ #1620
From: george velguth  <gcv@g...> 
Subject: [Bearhawk] Re: Mike - Rough field modifications 

While I have no real wheel-plane bush experience from which to respond
to your question, I have some floatplane experience that may apply.
When I flew pax in the floatplane I could not afford the luxury of
waiting for the rough water to go away before taking off or landing.
Nor was it practical to land in a sheltered area, then spend serious
time slow taxiing through the rough water back to the dock, like all the
floatplane textbooks tell you to do.  What made the difference between
normal operations and a busted, maybe sunk, airplane was airspeed.

We recently had a long and sometimes far-reaching discussion here about
STOL mods for the Bearhawk.  My rough water operating experience in a
STOL-kitted Cessna floatplane has convinced me that STOL mods are worth
their weight, and then some, in gold.  They allow slower and shorter
takeoffs and landings, which saves wear and tear on the airframe, and
has a definite impact on operational safety.  I am convinced that the
STOL kit on my Cessna floatplane saved my, and my passengers', lives
once.

The engineering types here can probably tell you in detail about the
energy reduction that accompanies each knot of landing speed reduction.
I can only offer my opinion that the first step in modifying any
airplane for rough field use should be to enable it to land and takeoff
as slowly and shortly as possible.

At the risk of re-opening the STOL mod discussion, I think the Bearhawk
is a prime candidate for a properly engineered set of vortex generators.

Just my opinion.

+++ #1621
From: Float-by Shooter  <packrat@c...> 
Subject: [Bearhawk] Re: Mike - Rough field modifications 

> Has anyone used large tires that have come available for use on ATCs
> and Sandrails on a bush aircraft.  I was thinking that the lightweight
> aluminum wheels could also be used, using lug nuts to attach to an
> automotive type spindle.  Brake calipers from ATC, motorcycle or light
> car could be used.  Maybe a weight savings, definitely an increase in
> convenience with the lugs, and perhaps a cost savings depending on
> equipment used and machine shop usage to make parts.

I ride a couple of ATC's myself, one of which I restored starting with
buckets of parts and a frame, and later converted to a 4 wheeler.  While
I am just a first time aircraft builder I think I know ATV's about as
well as anybody and you will not be finding any ATV components on my
aircraft.  The tires are much thinner than the aviation tires I have
handled, especially in the bead area.  The stock front spindles on atc's
and quads are quite small compared to the axles on an aircraft.  If you
try this, maybe get some trailer axle stubs and trailer hubs, which you
can get in a bolt pattern to match the atv wheels.  I don't have any
idea how much weight this would add.  You would also want to use heavy
duty tubes which might reduce the chance of losing a bead, which as they
say would ruin your whole day.

The brakes would be a whole 'nother nightmare.  Imagine trying to stop
2500 pounds of aircraft with brakes designed to stop 5-600 pounds of
quad and rider.  Don't expect to save any money either.  I recently
rebuilt the rear master cylinder on my ATC200X.  I wanted to replace it
but the new cylinder was somewhere in the ballpark of over $150 if I
remember correctly.  The rebuild kit was "only" $60.  I haven't priced
the rotors lately, but I'm always trying to scrounge parts and a good
rotor and/or caliper is a real score.  Brakes from a small car might be
a possibility, but by the time you have tied this motley assortment
together I'll bet you would have been better off just buying the
specified aircraft parts.

Sorry to be so negative, especially since I've had the same idea before.
If I were building an ultralight or near ultralight I might seriously
consider atv hardware for the landing gear.  +++ #1622 From: Float-by
Shooter <packrat@c...> Date: Mon Feb 21, 2000 2:37am Subject: [Bearhawk]
Re: Mike - Rough field modifications


> One of the BH's weak spots in really rough field use is the shock
> absorbing system although, in reality, there is no perfect system for
> really rough work because you want it to displace and soak up the
> shocks, but it has to come back to neutral and "recock" itself amost
> immediately to be ready for the next hit. If it's slow coming back to
> center, it can't absorb the next hit becauswe it's already partly
> displaced and if it snaps back too fast (like on bungees) it has too
> much rebound.

Perhaps this is an area where off-road technology might help.  Many
sport and racing ATV's (and I'm sure sand buggies) use shock absorbers
filled with nitrogen gas at high pressure, with remotely mounted
reservoirs.  If you ever get a chance to watch the top racers traversing
the whoop-de-do's you will see how effective they can be.  Maybe
somebody with a lot of money could have Works Performance, PEP or one of
the other off-road suspension companies engineer a set of shock
absorbers for bushplane use (I bet that they would be interested, but
afraid to touch it due to liability).

+++ #1623
From: Budd Davisson  <budd@g...> 
Subject: [Bearhawk] Re: Mike - Rough field modifications 

Re: Speed and landing shocks 

Everything having to do with landing energy is a squared function of the
speed. Knock off a few knots and it does wonders for energy tht doesn't
have to be gotten rid of. However, make sure you can still see over the
nose, since landing short is a function of how much runway you leave
behind you: hit the end of the runway, not 200 feet down it.  I'll be
flyign the hawk at SnF and intend on working with it in tht regime.

The real bugger in rough field work is the hard shocks that come from
rocks and ruts. Soft tires and slow speeds help this, but you'd be
amazed how hard some of those suckers hit even at slow speeds.

The Bearhawk is probably the best of all compromises between a utility
airplane and a serious bush bird like the Sherpa. The Sherpa, in case
you did notice it, uses 4 x 4 truck tires with the tread shaved off and
it's definition of a rock is something bigger than a
watermelon. anything smaller is gravel. And I'm not kidding.

+++ #1624
From: Zippydogg  <Zippydogg@a...> 
Subject: [Bearhawk] Re: Mike - Rough field modifications 

It is my understanding that remote shock reservoirs are needed for heat
dissipation where the shocks are required to adsorb energy for a long
period of time, such as an off-road race. I would think (IMHO) that the
landing and takeoff events are of such short duration that nothing more
than the plans shock would be needed.

I've set up a couple of car suspensions. As a general guide (in my
opinion) you want the softest suspension you can without bottoming out
the system.  The "thud" at the end of the stroke is what breaks
things. This is the whole point of progressive rate springs and
suspension systems. As far as damping rate, this is an area for
experiment by the builder. Changing fluid viscosity (remember this
varies a lot with temperature for some oils) and orifice size until
acceptable performance is reached. I would think that the spring rate of
the gear and the tire will affect the damping rate that would work
best. I think you would not want the plane to "bounce" after dropping it
in. Equal damping (same on compression and rebound) is probably near the
best. I wonder if the equations for damping would provide guidance as a
starting point.

It would seem to me (as a mechanical engineer) that the Bearhawk design
will be vastly superior to other gear systems, such as spring leaf, rod,
bungees, etc.

+++ #1625
From: Bearhwk272  <Bearhwk272@a...> 
Subject: [Bearhawk] Landing Gear - Shock Strut 

The Bearhawk landing gear is actually quite a good design and for most
of us will work very well, you outbackers might consider the mods
mentioned by Budd.  As has been alluded to the shock strut holds a big
key to whole picture.  The shock strut in the Bearhawk is a spring
loaded fluid damped shock strut. Bob has a hole drilled thru the piston
to function as a damping orifice. One technique used in real rough field
applications ( I mean real rough....Like in Carrier Landings) is to use
a "smart" orifice in the piston head. The orifice is designed as a
restrictor check valve with two across the head, back to back, then
extension and retraction load rate profiles can be set.( Other tricks do
velocity and end of stroke snubbing ) I plan on doing some analysis in
this area when I get to the fuselage.  If there is a huge interest now
and everyone is almost on the gear....  well twist my arm a bit..  A
Great Lakes Biplane has a similar dampened strut setup and has wonderful
landing and ground handling.

Back to the wings

+++ #1626
From: Rod Smith  <rsmith@a...> 
Subject: [Bearhawk] Rough field-Shock absorbers 

> One of the BH's weak spots in really rough field use is the shock
> absorbing system although, in reality, there is no perfect system for
> really rough work because you want it to displace and soak up the
> shocks, but it has to come back to neutral and "recock" itself amost
> immediately to be ready for the next hit. If it's slow coming back to
> center, it can't absorb the next hit becauswe it's already partly
> displaced and if it snaps back too fast (like on bungees) it has too
> much rebound. The BH shock strut is a good compromise, but could
> probably stand to be another 1/4" in diameter for serious work. The
> Sherpa people solve the instant-recock, soft-rebound thing by putting
> a large diameter, short stroke shock at the end of their bungee mount
> so the gear can come back quickly, but can't snap back.

I have an aquantance who ran into this problem with his Maule which uses
very similar shocks. He was on Skiis and landed on a snow covered lake
for some spring Bear hunting. The wind came up while they were there and
made hard packed short spaced drifts on the Lake. When they tried to
take off the shocks couldn't recover between drifts, went to full
extension and something broke, I dont remember what. They were fortunate
to be only 10 miles or so from a highway, started out on snowhoes and
some snowmobilers came across them before they got there.  Hauled
materials and tools back in on snowmachines to make the repairs.

+++ #1627
From: Kelvin Gurney  <kgurney@k...> 
Subject: [Bearhawk] Re: Mike - Rough field modifications 

OK Budd, this is the price you pay for having "Them thoughts"
again. Here I go displaying my ignorance again.

1.  Why another 1/4" in diameter?  I think I see why short stroke
hydraulic damper coupled with a bungee mount would work.  Lacking the
bungee component I had thought a longer stroke coupled with a simple
check valve in the piston to allow hydraulic fluid to return faster
would handle rough fields better.

2.  Why sleeve the longerons?  Why not increasing the longerons from
.049 to .095 or .120 and then splicing at station E or F?  Wouldn't this
be simpler and do a better job of distributing the load?

3.  Finger gussets?  A small gusset welded center line to center line on
the tubes?  What advantage does it have over a triangular gusset?

4.  If I could find an example of a taper rod tailwheel spring I am sure
I would have questions about it.

5.  I plan on using large, soft tires.  (They ever cost $$$).

+++ #1628
From: Rod Smith  <rsmith@a...> 
Subject: [Bearhawk] Re: Mike - Rough field modifications 

> I'm going to sleeve the longerons in the area of the landing gear
> fittings

Okay here is my contribution from personnal experience with rough field
use in a Maule. The gear attach bolts, in particular the shock strut
attach bolts take a real beating. I routinely changed them out at every
annual. I would have to hammer out the shock attach bolts with a punch
because they would be slightly bent. Once one of them was partially
sheared. Therefore, on my Hawk, I plan on 7/16th bolts for all 6 attach
points instead of 3/8th and will still change them out on each annual.

+++ #1631
From: budd davisson  <budd@g...> 
Subject: [Bearhawk] Re: Landing Gear - Shock Strut 

Kevin, When you start doing work with the shocks, get ahold of me and we
can share experiences and what we think needs to be done to the shock. I
agree with Kelvin that the BH shock is the best compromise and fine
tuning it with orfice diddling (sorry, didn't mean to get so Freudian)
and spring rate/snubbing is the way to go.

Incidentally, just so everyone knows: we're talking edge of the envelope
stuff here. 99.9% of users will find the BH design close to perfect.

+++ #1632
From: budd davisson  <budd@g...> 
Subject: [Bearhawk] Re: Mike - Rough field modifications 

> OK Budd, this is the price you pay for having "Them thoughts"
> again. Here I go displaying my ignorance again.
> 
>     1.  Why another 1/4" in diameter?  I think I see why short stroke
> hydraulic damper coupled with a bungee mount would work.  Lacking the
> bungee component I had thought a longer stroke coupled with a simple
> check valve in the piston to allow hydraulic fluid to return faster
> would handle rough fields better.

I'm not positive it needs the diameter, but the longer the stroke, the
further it has to recover once extended and recovery rate is critical to
handling multiple shocks (picture a plowed field). The suspension
experts amongst us can chime in, but unless I'm mistaken, the best
situation for multiple, not-rediculous shocks (as you see with ATV's) is
a medium length shock, with high spring rates (probably progressive) and
orfices with check valves that move a lot of fluid and control travel
both ways possibly at different rates. If all we had to worry about was
the first shock, we could go to single action, long stroke shocks like
carrier plans.  > > 2.  Why sleeve the longerons?  Why not increasing
the longerons from > .049 to .095 or .120 and then splicing at station E
or F?  Wouldn't this be > simpler and do a better job of distributing
the load?

I wasn't going to do the entire longeron, just the bottom half to
prevent crushing. This saves weight.

>     3.  Finger gussets?  A small gusset welded center line to center
> line on the tubes?  What advantage does it have over a triangular
> gusset?

Triangular gussets work very much against strengthening the structure
sometimes because they transfer the point of bending from the center of
the joint to a point at each end of the gusset. In reality, we should
never use triangular gussets, although most of the time, its no problem
because the tubes are heavier than they need to be in the first place.
Finger gussets wrapped along the centerline of the tubes and no wider
than the tube (a cluster finger gusset looks like a glove, when
flattened out) keep the loads centered inthe joint but spread theloads
up the tubes and give more weld length.  > > 4.  If I could find an
example of a taper rod tailwheel spring I am sure > I would have
questions about it.  > > 5.  I plan on using large, soft tires.  (They
ever cost $$$).

I've heard numbers like $350 each for the 31 x 6 tires, but can't very
five that.

+++ #1633
From: george velguth  <gcv@g...> 
Subject: [Bearhawk] Finger gussets, et. al. 

One of the most vivid memories from my seaplane days is of seeing the
incredible vertical movement of the back side of the spinner as the
plane smashed its way over waves in the last few seconds of some of the
roughest-water takeoffs, and first few seconds of the roughest-water
landings. This spinner movement - which, of course, was a visible
symptom of engine movement - occurred despite a highly refined
takeoff/landing technique which ensured absolute minimum airspeeds and
rough water exposure times, and the gentlest-possible touchdown.

What I'm slowly getting to here is that the amazing loads which caused
such engine movement were transmitted directly through the
float/fuselage attach points. Although I have no intention of routinely
operating a Bearhawk on floats in such extreme conditions, as was often
necessary in the commercial environment, I am keenly interested in ideas
for strengthening the Bearhawk fuselage in the gear (float) attach
areas. I was following your finger gusset description quite nicely, or
at least I thought I was, until you described it as looking like a
flattened glove. Any chance you can post a drawing or photograph, or
even a Jethro Bodine-type textual description to get me back in the
loop?

+++ #1634
From: Archie Dunbar  <dunbar@m...> 
Subject: [Bearhawk] Re: Finger gussets, et. al. 

> I was following your finger gusset description quite nicely,

Page 4-63 of AC 43.13-1b

I think this is what Bud is describing.

+++#1635
From: Kelvin Gurney  <kgurney@k...> 
Subject: [Bearhawk] Re: Finger gussets, et. al. 

Thanks Archie!

George, I don't know if you have Russ's CD.  If you do it's in folder
"AC43", Adobe file "1v-ch4_5.pdf" page 11 of 26.

+++ #1640
From: Mike Meador  <mike2799@r...> 
Subject: [Bearhawk] Do you Really Think? 

OK Guys - let's slow this down a bit.

First - don't ask me for design change approval. It is fine if you want
to do whatever you want to do - just don't think I'm going to say it's
OK.  It'll be your neck up there, not mine.

Second - PLEASE read Rus Erb's scholarly work "Design Propagation
Nightmare" - I think you can find it on his web site. It can cool the
hottest mod.

Third - We only have 2 Bearhawks flying right now so there is not a
whole lot of historical evidence that any areas need "beefing up" -
let's get a couple of hundred of these things in the air first and then
we can make it better (if it ever really needs to be).

As for all this landing gear stuff - I have yet to see the landing gear
design that is perfect. In a really hard landing I think I would rather
have the gear collapse under me, absorbing tremendous shock, than have
the world strongest gear come punching up through the floor in its
magnificent glory. You want good bush gear go with the BIG tires - I'll
have another "Other" post on this if you are interested - don't go
"improving" Bob's design. We have seen a 4 G landing in the prototype
and nothing broke so it must work.

Budd, I think you had a really good article one time about the angle of
impact vs. survivability. I can't remember where I saw that. (if it was
not you I must have seen it in Kitplanes)

+++ #1643
From: Mike Meador  <mike2799@r...> 
Subject: [Bearhawk] Other - BIG Tires 

Some Experimental Tire Thoughts - 

During our trip to Alaska in 98 - Bob and I inspected a lot of the 30+
inch diameter tires on the bushplanes, the Alaskan Bushmaster seemed to
be the most prevalent. There were several sizes and a couple of wheel
mods to accept a larger tire.  One thing we found out were that those
real bush tires are not cheap and the blimp tires are way too heavy.

Doing some research I have found what I think to be the perfect
Experimental Bush tire - it is the rear tire of of a light duty Kubota
tractor.  It is Bias Ply, it uses a tube, it is only 4 plys thick (light
weight, relatively) it is 31" in outside diameter and it mounts on a 12"
rim.  The only problem I have is obtaining one (or two) for research -
we have a local Kubota dealer but he does not seem to be very helpful
and I have not had much luck on the web.  The tire stores have huge
books with all sorts of tires in them but not this one.

Just some thoughts - maybe one of you would like to look into this more.

+++ #1645
From: Kelvin Gurney  <kgurney@k...> 
Subject: [Bearhawk] Re: OTHER - Do you Really Think? 

Mike, Seeing how I started this thread let me say in my own defense I
was not trying to improve Bob's design.  But rather was operating out of
the belief he originally designed the Bearhawk for his own needs,
carrying loads and flying out of a grass strip.  My needs are slightly
different and as a result I suspect things can be tweak to meet those
needs an still stay out of the "Design Propagation Nightmare".  Got to
tell you though, I wish I had read your post before I posted the "almost
but not quite flap rod ends".  I think I would have waited a few days!
(Grin)

+++ #1646
From: Zippydogg  <Zippydogg@a...> 
Subject: [Bearhawk] Re: Other - BIG Tires 

Tires.

I think that there are some tires on the market that would be suitable
for aircraft use. I think the garden tractor idea is promising.

One interesting comment made here was the retention of the tire on the
rim.  Definitely a requirement on any takeoff or landing. The car guys
have a similar problem retaining the tire on the rim at low tire
pressures. They have developed "bead locks" that are additional rings
that bolt at the bead area, mechanically retaining the bead.

Brakes - Another interesting comment concerned brake capacity. I was a
brake engineer for a while and should point out that brakes are sized
for capacity and capability. Capability means can the brake develop
sufficient torque to do the job, generally can it lock the wheel on dry
open concrete. Capacity means can the brake adsorb then transfer enough
heat energy for the application, generally can a reasonable number of
multiple maximum energy stops be performed within a given amount of
time. (I've flown military aircraft that could make one, and one only
maximum effort stop at max weight.) I'm not advocating this small of a
brake for general use, but think that motorcycle calipers on motorcycle
disks should do an adequate job on an aircraft that can weigh up to
2,500 lbs (correct gross weight?). A very valid point was made that the
cost of motorcycle parts can be as outrageous as aircraft parts.

+++ #1648
From: Kelvin Gurney  <kgurney@k...> 
Subject: [Bearhawk] Re: Other - BIG Tires 

I had a letter from the man who makes the Alaska Bushwheel tundra tires.
Basically I was asking him why I should spend $3000.00 on his tires when
the competition's were $800.00. I tossed his letter when I decided a set
of $3000.00 tires were not in my near future.  He had a problem with the
side wall strength of most tires adapted for aircraft use.  If I recall
correctly, (and there is no guaranty that I do), they lacked sufficient
side wall strength and would try to "go around" obstacles instead of
"going over" them.  I do recall the result was lateral loads being
transferred to landing gear designed for vertical impact, not lateral
impact.  He said there was allot of broken landing gear because of this
fact.

(Hope I didn't screw up what he told me too bad!)

+++ #1649
From: Russ Erb  <erbman@c...> 
Subject: [Bearhawk] Wheel Pants... 

It occurs to me that we have concurrent threads running, to wit:

1) Those who want streamline wires on the tail to go faster
2) Those who want earth mover tires so they can land in gravel pits, and
thus fly slower

(If you want streamline wires AND big tires, you're having a serious
mental lapse in your mission requirements!)

Therefore, just for grins, let's stir the pot some more, and see if we
can mix the two of these together, namely faster tires...

Has anybody thought about using wheel pants? Since my buddy's C-180 uses
the same size tires, it would seem that C-180 wheel pants would work.

BTW, improperly designed wheel pants (mostly with too big of gaps around
the tire) can actually INCREASE your drag by acting like little
parachutes.

+++ #1650
From: Float-by Shooter  <packrat@c...> 
Subject: [Bearhawk] Re: Wheel Pants... 

> (If you want streamline wires AND big tires, you're having a serious
> mental lapse in your mission requirements!)

True, but there isn't anything that says somebody with big tires can't
also have a set of smaller ones with wheelpants.  My brother has
contemplated getting a set of little tires for his Citabria for making
really long cross countries with no rough work anticipated.  In any
event, the streamline wires can't hurt anything.

In my case I think I will probably just stick with the plans as far as
gear go since I don't anticipate anything too rough.  I probably won't
bother with the fairings at first, however, since I initially only plan
on having the gear installed until I can build or otherwise get my hands
on a set of floats!

+++ #1654
From: Kelvin Gurney  <kgurney@k...> 
Subject: [Bearhawk] Re: tires and wires 

I couldn't find their web site either and I looked for awhile before I
posted what I could remember being told about tundra tires.  I know I've
seen a web page before.  Those tires are made by Alaska Tire and Rubber
Co.  The best I could come up with is a picture at
http://www2.coastalnet.com/~cn2568/sponsors.html

+++ #1655
From: Bruce A. Frank  <BAFRANK@w...> 
Subject: [Bearhawk] Re: tires and wires 

I did also but found this tid-bit.

http://www.safetydata.com/tundra.htm

+++ #1656
From: delton Savage  <dshannon@p...> 
Subject: [Bearhawk] No Subject 

Try (alltheweb.com) and search for Alaska Bushwheel Tundra Tires. I got
a hit in .0752 seconds. Read 1. Frequently Asked Questions

+++ #1662
From: george velguth  <gcv@g...> 
Subject: [Bearhawk] Re: Wheel Pants... 

Check out the June 99 issue of Sport Aviation. Page 59 features a photo
of some wheel spats installed on a Turbine-Powered Luscombe which the
caption claims gained 10-12 mph in cruise speed. I have seen these
half-wheel pants on several other types, including the Kitfox, and
generally like their appearance. It seems to me that they would also be
a good compromise for a bush plane: While they could still be damaged in
an extreme environment, e.g. landing amid boulders, logs and gullies,
they at least would follow the wheel through the thick stuff, instead of
blazing the way.

+++ #1663
From: Budd Davisson  <budd@g...> 
Subject: [Bearhawk] modifications, etc 

Re: modifications

I want to make a personal comment here concernign modifications. There's
a tendency for many of us who spend our lives
building/rebuilding/modifying flying machines to forget that other
people are listening to our conversations who don't necessarily have the
same experience level. For that reason, I want to make a flat statement:

THE BEARHAWK NEEDS ABSOLUTELY NO MODIFICATIONS FOR PRACTICALLY ANY USE
YOU CAN CONCEIVE OF. FURTHER, UNLESS YOU'RE AN ENGINEER AND PRIVY TO
BOB'S THOUGHT PROCESS WHICH LEAD TO A PARTICULAR PIECE OF DESIGN WORK,
TO MAKE ANY MODIFICATIONS IS NOT ONLY PROBABLY COUNTER PRODUCTIVE, BUT
POSSIBLY DANGEROUS. AN AIRPLANE IS A CHAIN OF PARTS AND ANY MODIFICATION
MADE TO ANY LINK, CHANGES THE REST.

Any of my comments are based on personal taste and opinion and apply to
my own, rather peculiar, uses (360 hp) and absolutely do not reflect on
the design. If I had a brain in my head, I'd build it with an 0-540 and
leave it alone. However, since I'm doing what I'm doing, that
automatically says how much vacant cranial space I have. I also have a
degree in aeronautical engineering with an emphasis on structures and
still do engineering design projects for a number of airframe companies,
so i'm not too rusty. And I've lost track of the number of airplane
projects I've been directly involved in.

So, I'll toss my two cents in, but when it comes to making a decision,
do it the way the plans show. Period! I can't improve on anything Bob
has done and chances are not many of us can.

As for tires: go with something proven. it would be a real bummer to
wind up on your back because of trying to use some tire that has no
track record in aircraft uses.

Re: flying wires: the plans show an elegantly cheap way to do it. If you
want to spend the bucks, go streamlined but buy them from Steen Aerolab.

Re: landing gear mods: The airplane doesn't need any gear mods unless
you're planning on landing on plowed fields full of stumps and that
probably won't hurt it either, if you're flying fat tires.

+++ #2149
From: WIL DAY  <wlday@n...> 
Subject: Re: Budd's SnF/P-II comments 

>Only downside is that at 23 square (Bob cruises at an amazing 19 square
>for 7.5 gallons and 120-125 mph) it's only cruising at about 150 and
>the wing is nose down about 2 degrees, which puts the fuselage about 4
>degrees tail high. A huge amount of horsepower is being wasted. We
>talked about fixes which includes changing angle of incidence to level
>fuselage in high cruise (won't change wing nose down), clipping the
>wings for the big engine birds (to load the wing more) or changing the
>airfoil slightly. Clipping it or changing the airfoil enough to get the
>airplane level would add AT LEAST 12-15 mph to the cruise and hardly
>effect the low end with that power. If used as a pure bush bird, I
>wouldn't do either as it's perfect for the mission right now.

Since I am a newby to some of this info could you explain what you mean
from above?

What to you mean by "23 square"?

How does clipping the wings (shorting the wings?) work?  I kinda
understand about the angle of incidence.

So, what would you recommend for engine size to fully utilize the plane
as it?

What advantages/disavantages would your mods do for the plane?

+++ #2153
From: budd davisson  <budd@g...> 
Subject: Re: [Bearhawk] Re: Budd's SnF/P-II comments 

I'll be putting a complete report on the 260 BH on Airbum.com right
after the first. That'll address most of the details.

23 square means 23" of manifold pressure and 2300 rpm, which is
something like 65% power.

clipping the wings forces the wing to work at a higher angle of attack
to provide the same lift, which is normally bad, but since it's plowing
along nose down, could help. It would hurt the STOL performance although
it accelerates so fast I doubt if you could measure the difference. A
better airfoil is the way to do it.

As I noted, however, as a working bush type bird just built it as is, as
it'll jump off in nothing flat and still has a fast enough cruise. I'm
just an efficiency freak is all and I hate to see all that horsepower
wasted in cruise. Even with a 180, it's a kick in the shorts!

+++ #2157
budd davisson  <budd@g...> 
Subject: SnF/P-II comments 

The airplane is flying perfectly level at about 125 mph which is about
where it cruises at 21 square with the 180 (as I recollect) and 19
square with the 540. . The drag rise resulting from the negative angle
of attack and fuselage angle starts to get noticeable at about 135 mph.

+++ #2171
From: budd davisson  <budd@g...> 
Subject: Re: [Bearhawk] 180 vs BH 

> The Bearhawk has the potential to become the "poor man's Cessna
> 172/182"

Apropos of nothing but a 180 hp Bearhawk will out haul and out climb a
182. A 260 BH will blow it's doors off although neither version is as
fast a 180/182 because of the wing.

+++ #2172
From: Steve Eldredge  <steve@b...> 
Subject: RE: [Bearhawk] SnF/P-II comments 

Russ, and others still listening,

I mis-understood that decalage was the difference in the angles of the
wing and the tail angles on incidence. Is there a term for that?

I do understand the second point (I think).  The increase in drag would
come from the elevator and stab fighting against each other, and would
also cause pitch trim problems.

In layman's terms what I believe Budd was describing is the fact that
with the current setup, at 260hp, the wing is producing too much lift
above about 135mph.  Solutions like shortening wing span and decreasing
wing incidence, reduce the ammount of lift produced at a given speed,
and would allow the plane to cruise faster.  A different airfoil is best
since it would allow a faster cruise speed, without (in theory)
detracting from the low end STOL characteristics of the modified
(shortened) origial wing.

+++ #2185
John Morrison  <johnm@v...> 
Subject: Sea duty.... 

Evening all, Knowing that my BearHawk is going to spend a great deal of
time on the water, I want to build it with this in mind.  Therefore I
will pay particular attention to detail in protecting the metal tubing
etc.  Can anyone speculate as to the formula/parameters involved in
designing and building amphibious floats for the bird?  Clearly we know
certain parameters, such as the gross weight of 2500lbs.  I would assume
the buoyancy of the floats must be equal to or greater...which should
have gone without saying (so why did I say it?).  I wonder is this
process is as simple as scaling down or scaling up existing float
designs to accomodate the size and weight of the BearHawk?  I know some
of you are looking at what fuselage adjustments are required, has anyone
gotten as far as floats?

On this topic, assuming several of us are working on the floatplane
issue, wouldn't we be better served if one of us tackled the fuselage
mods, someone else research the mods needed to correct adverse yaw
caused by the floats and finally someone researching float design?
Strength in numbers eh?

+++ #2186
budd davisson  <budd@g...> 
Subject: Re: float design... 

Johnny Canuck, 

First, the 1200 pound useful on the BH is determined by Bob's own
airplanes and I guarangoddamntee you that no one is going to build one
as light as he does. I think he even uses helium in the tires. If anyone
gets within 100 pounds of his, I'll be surprised. The starter/alternator
(not lightwieght units) alone add 37 pounds and that doesn't count the
battery and cables. And I'd like something a little sexier than Ceconite
for upholstery.

As for designing your own floats: forget it. Build them, yes. Design
them, no. The complexities of good float design are much hairier and
less understood than designing an airplane. If you want to build your
own, track down a set of EDO's and copy them. That goes for the strut
system too.

I'm not much of a float pilot, but most of the specs seem to favor EDO's
in terms of time on takeoff, as opposed to Wiplines or others. Any of
you northerners have any opinions.

Here's an idea: how about one of you float types cornering the right
size EDO and drawing up a set of plans for them.

+++ #2191
From: Nathan Wight  <wightgnats@n...> 
Subject: Re: [[Bearhawk] Sea duty.... ] 

John, I was in Middlebury Vt last week and saw a great looking set of
amphibious floats for a Pelican. They looked like they would scale up
quite nicely. The gentleman from the FBO said they were made by the
company that kits the Pelican, so I don't know if plans or larger kits
are available. Well worth looking into.

+++ #2193
From: budd davisson  <budd@g...> 
Subject: Re: [[Bearhawk] Sea duty.... ] 

Again, designing a good float is more of an art than a science and
scaling an existing float may not work. Stick with the ones that
actually work, EDO's, and copy one of those.

I wonder if the company that now makes EDO's would consider punching out
kit parts or selling plans. Probably not because of the liability issue,
but someone ought to ask.

+++ #2194
From: Tim Anderson  <fuzzet@h...> 
Subject: Re: [Bearhawk] Sea duty.... 

I'm not a float expert, but I am a float pilot and have Lotus floats on
my plane.  If my memory serves me right, The displacement of the two
floats must be equal or greater than 180% of the gross wt.  I talked
briefly to Bob about float fittings, etc, at S&F.  He made the comment
that the gross wt on the BH could probably be increased if on floats
because the landing gear is often the Gross wt determining factor.  This
is why you will often see a planes gross wt increase if on floats.  When
I get to the point that I'm adding floats, (8 or 10 years) I'll talk
over the Gross wt with Bob.

There are a few kit built floats out there, but I'm not sure if they are
in the range of the wt's required for the BH.

Lotus floats are alright.  The are relatively inexpensive compared to
alum.  floats.  I beleive they make models now in the 2500 pound range.
They are very smooth (being air filled) on landing, but they don't have
a bottom keel so if you are step taxi-ing, you may water-loop the plane.
Also, the sweet spot when on the step in very narrow compared to EDO's
or other alum floats.

Just my thoughts.

+++ #2195
From: Bill Cox  <t18cox@f...> 
Subject: Re: [Bearhawk] Sea duty.... 

Zenair is kitting a 2200 pound float that will also be available
anphibias (spelling?).

+++ #2197
From: Todd Chisum  <toddc12@h...> 
Subject: Re: [Bearhawk] Re: float design... 

There is an ad in Kitplanes and/or Sport Aviation for Easy Lift Floats
in Canada. I have the photo info pack, he has amphibious floats that
might work. They are metal. I have missplaced the order sheet, so I
don't know many details. His name is Roger Laland, 819-727-9660, fax
819-727-4330.  Sorry, I don't have his address handy and don't know of a
website, but a recent magazine should have his B&W add. The back of his
card says "float kit or full fabricated from 950 to 3430 (GW maybe??)
straight or amphibious....all technical assistance available".

There is also a company in Canada working on wood amphibious floats for
ultralights, MukTuk floats. They currently sell plans for straight
floats for different GW planes. They might be a helpful source in the
future.

+++ #2198
From: george velguth  <gcv@g...> 
Subject: Re: [[Bearhawk] Sea duty.... ] 

I'm all for float construction drawings. Several years ago, I rebuilt my
Edo 2000s. These things are wheat-paste-simple. I expect floats with
flat tops and sides would be even more so. As for getting Kenmore, or
whomever is currently producing edo, to sell kit components, well, let
me just say that you haven't really been screwed until you've purchased
edo float repair parts.

As an example, were you to have started with a C-172 float plane and a
set of 2000s, less struts, you would have spent 8,500 1997 dollars to
purchase just the struts needed to attatch floats to fuselage.

As far as I can tell, the