+++ #396
Subject: Rudder and Elevator Hinges
From: Rodney Smith

I'm at the point where I am ready to build the 6 control hinges as shown
on drawing 21. I am unsure of the best way to bend the .062 pieces
around the 1" tubing. My current plan is to tack weld the flat piece on
the back side of the 1" tubing, heat it with a torch and carefully form
it around the tubing by hammering, maybe adding some more tack welds as
I go. Then I would drill the hole last, match drilling them with the
7/8" tail post and horiz. stab rear tubes. Has anyone devised a method
to cold form these pieces? If this doesn't sound like a reasonable plan
please let me know.

+++ #398
Subject: Re: Tail Wheel Steering Yoke
From: Float-by Shooter

About bending the hinges, I've thought about them a bit, but haven't
been able to do more than think about them.  There ought to be some way
of making a rolling fixture kind of like a tubing bender, but the
biggest problem I can see is how to allow the right amount for
springback.  Probably take a lot more effort to make the tooling than
the actual parts, but that hasn't stopped me yet.

If I were going to hammer them, I would find a piece of solid steel
round stock the same size as the tubing and use that instead of the thin
tube, but you probably already thought of that.  Does anybody know how
Bob makes them?  By the way, a good cheap source of solid round bar for
this sort of thing, is old suspension linkage from a junkyard.  IIRC, a
lot of old 4 wheel drive pickup trucks have a 1" bar running from one
spindle to the other as part of the steering linkage.  We rebuild quite
a few front ends in the shop here, and never lack for homemade punches
in various sizes...

+++ #402
Subject: bending tailfeather hinges
From: Float-by Shooter

Last night I mentioned that some kind of rolling fixture should work for
bending hinges for the elevators and rudder.  I thought about it some
more, and came up with an idea along those lines that ought to work
pretty well, but might be a lot of work to make.  Well, tonight I was
looking through one of my tool catalogs, and saw almost exactly what I
had in mind.  Now I'm not suggesting that anybody go out and spend the
$190 to buy one just for bending the hinges, but I found a picture of
the tool on their (Grizzly's) website in case anybody else wanted ideas.
The link is:

http://www.grizzlyimports.com/fcgi-
bin/lookup.fcgi/products/lookup.cfg?q=item&kw=G7153

+++ #403
Subject: Re: Rudder and Elevator Hinges
From: Mike Meador

Ok - I checked with Bob and he said the best way for you to use the hot
bend method. You will not have to worry at all about springback and it
is simple to do. A single tack is all that is required. Tack the strip
in place and heat it red hot in the radius area and push it around - You
will not need additional tacks and you will be pleased with how easy it
is. Proto II hinges were made this way.

Bob did say that you could do it cold if you want - but it is a but more
difficult and you might not get repeatable results. Use a 5/8" diam. rod
or tube for the forming die and wrap the strip around 180 degrees plus
20% to take care of springback. I am not sure how the strip is held in
place while doing it this way but I am sure that you could figure
something out that does not involve a $150 machine.

+++ #404
Subject: Re: bending tailfeather hinges
From: Archie Dunbar

> Last night I mentioned that some kind of rolling fixture should work
> for bending hinges...

I made a device.  It worked real well.  I took four flat steel bars and
rigged them into parallel pairs hinged together at one end.  the hinge
portion was bushed out to about 7/8 inch.  Then one side has a rod
through it to trap the strap and the other has a roller(bushing) to
press the strap around the 7/8 inch piece as you squeeze the two
parallel pairs together.  It took about an hour to make and ten minutes
to get the hang of using it.  I had to make the straps about an inch
longer than finished size because it is hard to eyeball just where the
middle of the bend is going to end up.  The pieces fit perfectly and can
be trimmed and drilled later.

I can't find the thing just now and I don't have a coler scanner but
I'll work on getting a picture.

+++ #763
Subject: steel
From: Pat Fagan

Don't think this went through last time so I'll try again.  After adding
up what I needed to order for my fuselage steel, I decided to get the
whole order from Dillsburg afterall.  Spruce is so expensive that the
savings from just the 3/4 .032 will pay for the truck freight for the
whole order. Sheesh.

I sent Bob Barrows a note asking about a question I had on the plans.  I
don't recall the plan sheet number, but it is the sheet covering the
rudder.  There are two drawings of a typical hinge for aileron and
rudder.  On the top view of the hinge, I asked what kind of gap should
we be looking for between the moving and stationary parts of the hinge.
He said "parts can contact before welding, should turn freely after
welding, up to .030 gap is OK".  On the other view where it appears you
are looking through the hinge, I asked about the "V" shaped piece that
appears to be welded to the stationary post.  He said it is a piece of
.062 X 1/2 wide 4130, welded to the tube for reinforcement against side
loads.

+++ #765
Subject: Rudder to fuselage fit
From: Rod Smith

I have a question that probably either Mike or someone who has the
rudder fit to their fuselage will have to answer. While measuring the
tailpost for drilling the rudder hinge holes I noticed some dimensions
on the plans that didn't look right. On closer investigation it appears
to me that as designed, the bottom of the rudder is offset upward from
the bottom of the fuselage nearly an inch. Is this correct? I didn't
notice that when I saw the prototype and it doesn't appear that way in
any pictures that I have.  It seems to me it would look better flush
with the fuselage. The only reason I can think to offset it upward would
be for more clearance from the tailwheel if you landed real
hard. Anyways this doesn't make me real happy as I just finished welding
the rudder. I gas welded it and am pretty happy with the way it turned
out. Looks great in profile, but has a few minor side to side wobbles in
the 3/8th tubing. I imagine some tapping with a mallet will fix those. I
have the rest of the tailfeathers tack welded.  It's no fun to be at
work over Christmas but has been a great week for building Bearhawk
parts.

+++ #1005
Subject: Tail wheel springs
From: Tim Anderson

For all you tail dragger "maintainers"

Have you ever developed (or do you heard of) a good procedure or tool
for effectively compressing both tail wheel springs in order to connect
or disconnect the rudder/wheel linkage.

The method of pushing the rudder one direction and the tail wheel the
other to get some slack in the connections works, but.......
Fortunately, one does not have to deal with this problem very
frequently.

+++ #1011
Subject: 023 Update
From: William & Delinda Johnson

Rudder completed and Scott Tail wheel mounted this past weekend. The
PA25 tail spring works absolutely great! It is 1.75 inches wide and fits
the Scott tail wheel perfectly. Came with four springs - two go all the
way to the tail wheel bolt. I plan to use only three of the four. I will
add the forth if necessary.

Notes:

1. I used a large v-belt pulley for bending my tubing on the rudder
which worked well.

2. Spruce sells the tail position light fixture which you weld to the
rudder by cutting approximately one inch out of the T3 tubing (back of
rudder). See their catalog page 373 P/N 11-07000.

3. I used a piece of angle iron clamped to the tail post while welding
on the vertical fin. Helped to minimize the problems of bending due to
welds.  Mine came out perfectly straight.

4. Although not on the plans, notice the rudder stops in Mike's picture
set. Could be easily missed.

5. Be careful NOT to weld all the way around the .090 washers on the
rudder horn! Look at the weld pattern on the plans carefully. I made
this mistake! Also, install the rudder horn with the hinges since the
gap is not wide enough to install over the tube after welding the ribs
in place.

6. I am modifying the tail spring attach bracket. Instead of 4 bends as
shown, I am making the u channel (only two bends) and welding tubing
vertically on each side for the AN4 bolts. Benefits include fewer bends
and I can get the bolts closer to the springs and further from the edge
of the bracket welded to the fuselage.

+++ #1012
Subject: 023 Update
From: Russ Erb

> 5. Be careful NOT to weld all the way around the .090 washers on the
> rudder horn! Look at the weld pattern on the plans carefully. I made
> this mistake! Also, install the rudder horn with the hinges since the
> gap is not wide enough to install over the tube after welding the ribs
> in place.

Okay, I'll bite. Why would welding all the way around the washer be a
problem?

+++ #1016
Subject: Re: 023 Update
From: Float-by Shooter

> Okay, I'll bite.  Why would welding all the way around the washer be a
> problem?

My understanding is that welding across the arm might create a point
where cracks can form, I think one of the Bingelis books mentions this.
The washer just provides extra bearing surface so that the hole does not
wear prematurely, so it probably doesn't need to be welded around the
full circumference.  I've noticed that in some places the plans show
levers (like the flap arms) without the weld going all the way around
the washers, and in others the weld is over the full 360 degrees, like
on the rudder lever pieces that I formed last night.  Unless I hear a
compelling reason for doing so, I'm not planning to weld across the arm.

I think the washers are a really nice touch on Bob's part.  I looked at
the old steering arm from my brother's Scott 3200 when he was working on
it over his Christmas break, and the holes were severely elongated.  I
think welding washers on the ends would have prevented that, but would
probably violate the sanctity of his certified aircraft!

Mike, do you know when/if Bob is going to publish the plans for his
homebuilt tailwheel?

+++ #1022
Subject: washer welding
From: budd davisson

Welding around the washer: 

It's always a good idea, where possible to avoid welding across the load
path so as to avoid possible disruption of the material characteristics
in that area. In the case of the washers in question, they arejust
adding thickness to avoid bearing failure of the metal: They aren't
needed for shear or tear-out strength, but keep the metal from getting
pushed out of shape.

Welding across the load path isn't a super bad thing, but it's usually
avoided where possible.

+++ #1025
Subject: Re: 023 Update
From: William & Delinda Johnson

Below comment is is my understanding as well.  I looked at a rudder arm
off a Citabria - no washer.  I asked my father (A&P AI for 20+ years).
He said that on arms with washers, they never weld across the arm.
Flexibility being the reason.  So, I made mine over again without the
360 degree weld - my first was perfect but is now in the scrap pile!
Perhaps I will try a destructive test to validate.

Mike Meador, can Bob add any information to the discussion?  He must
have a reson for not showing a 360 degree weld.

+++ #1034
Subject: Re: washer welding
From: pfflyer-

I would think it would be acceptable to braze the washer on since all
you are trying to do is hold it in place, an ideal job for brazing.
Even less chance of chance of adverse effects with brazing.

A question for those that have built the the landing gear shock strut,
what is the source for the 1018 steel cap material?  I can't find any
pipe in 2 5/16 O.D., or greater, with enough wall thickness to get the
inside dimension.  Is it going to be necessary to bore out the cap from
a solid steel bar?

For you structural engineer types, I started working on my horizontal
tail, and after bending the leading edge to the EXACT curvature,
discovered that I had bent it the wrong direction.  The long side of the
scarf at the fuselage is on the inside of the curve, not the outside as
in the plans.  Does it matter?  If it does, fine, I'm used to doing
things over, but why does it matter?

+++ #1038
Subject: Re: washer welding
From: budd davisson

I don't think it's a good idea to braze the washer on. The theory behind
the washer is that it is making the bolt/pin think the 4130 is that
thick all the way through. It provides a bearing pad for the pin to push
against. Brazing will have a different modulus of elasticity than a weld
(which is the same as the steel)and the washers will be willing to move
at a different rate than the parent material, so the bearing resistance
effect will likely be compromised. Welding it gives everything the same
ability to resist and the pin/bolt won't even notice it is pushing
against two pieces, not one.

+++ #1271
Subject: Re: Bearhawk CD
From: Rod Smith

> > In the first hour two questions were answered for me that I didn't
> > get reply's to on the list.
> 
> Okay, Rod, you've got me curious. What were the two questions you had
> answered?

Actually I guess I only asked one of them on the list. The relationship
between the bottom of the rudder and the bottom of the fuselage. The
detail pictures clearly show that the rudder is raised about an inch
higher. Another question answered for me was how is the wing faired to
the fuselage behind the rear spar. Good detail pictures of that. I had
wondered what you do with the fabric around the rudder and elevator
hinges. Now I see that Bob just cut it around them. I asked the other
day about adding washers at the end of the rudder pedals and had lots of
responses. Your picture of the rudder pedals in the prototype shows that
Bob did that also although its not shown in the plans. I went through
your wing rib construction section last night. Your detailed description
and pictures are going to save me considerable time in that area.

+++ #1273
From: Float-By Shooter

> wondered what you do with the fabric around the rudder and elevator
> hinges. Now I see that Bob just cut it around them.

I had also wondered about that and saw how Bob did it when going through
the CD. I can't help but think that there has to be a better (and better
looking) way. I know that Bob probably isn't too worried about it down
in Virginia, but it seems to me like that would be a good place for
water to get into the surfaces and possibly freeze in the winter. I
realize that the tailfeathers will have vents on the bottom to allow
drainage, but they could get plugged and if the water never gets inside
it doesn't have to drain. Would it be possible to surround the hinges
with .032 channel to provide a surface to stick the fabric to?

+++ #1274
Subject: Re: Bearhawk CD
From: Bill Cox

> Would it be possible to surround the hinges with .032 channel to
> provide a surface to stick the fabric to?

Jim Clements, the master Tailwind builder, adds a flat piece of .032
roughly triangular shaped around the hinge. This adds about 1" of glue
area all around the hinge and makes a nicer looking cover job. It also
eliminates the problem of the fabric rolling up a bit on that trimed
edge.

+++ #1363
Subject: Rudder Details
From: Rod Smith

This is a follow up to some information I posted awhile back. On drawing
21, Bob shows a 2 1/2 long 3/4 inch tube welded into the 7/8th tube at
the bottom of the rudder. The annotation says inside dimension to fit
rudder arm shaft or something to that effect. I had stated that the only
ones I had found had a 3/4" shaft and I was concerned that there would
be a somewhat sloppy fit inside the 7/8th .049 tubing. After a fruitless
search for a used rudder arm, I purchased a new one made by Scott, part
#1140 same as sold by ACS. It is cast aluminum and has enough surface
roughness that the 3/4 inch shaft makes a nice snug fit inside the 7/8th
tubing. It has steel bushings for the steering spring connections. So my
advise is dont weld the 3/4 inch tube on the bottom of the rudder. I
left the main 7/8th rudder spar tube 1/2" longer to match the plans
length with the 3/4" tube.  This will all be much clearer if you have
the drawing in front of you to reference.

+++ #1428
Subject: Rudder Ribs etc
From: Gary Danford

Because the ribs for the rudder and stab are so hard to build, I am
considering building them as they are on the WACO. They used 1/4 .028
from the top edge of the 7/8 to the top edge of the 3/8 and another rod
on the other side. I don't think two pieces of 1/4 028 would be any
heavier than the .032 channel. It gives a perfect surface for the rib
stitching and as with the channel you have to use tape on the edges
unless you get the 1/8 inch bend correct. I guess if it worked for the
WACO why wouldn't it work for the Bearhawk. I sure would be easier and
faster. I have tried bending the channel on my Hatz and without a bar
folder or a large brake its almost impossible.

+++ #1429
Subject: Re: Rudder Ribs etc
From: budd davisson

Re: tail ribs 

Using .028 x 1/4 is an alternative method called for on many plans
because bending the ribs can be such a bear otherwise. I've used it on
several airplane and it works fine. Some folks let the tail edges over
lap each other at the trailing edge (the ends lay side by side) but
that's ugly and makes rib stitching tough. The tubing is so small, I'd
just cut a really long taper on the band saw and grinder and weld them
into a nice flush triangle at the trailing edge.

A note however. The bigger ribs on the stabilizer and elevator will need
a single short piece welded vertically in the middle to keep the
ribstitching from compressing them.

I'll be talking to Bob today and I'll try to remember to ask him about
this.

+++ #1432
Subject: Re: Rudder Ribs etc
From: Rod Smith

I'll be the first to admit that bending up those channels is a pain in
the butt. I was very fortunate in having access to a large shear for
cutting out the blanks and then a 12' brake for bending them. There are
as I recall 35 channel pieces required for the entire project. It took
me about 4 hours to bend them all. With a helper it probably would have
taken an hour. The hardest part was getting the piece aligned properly
to catch the 1/8 lip. Sometimes the piece would spring out of the brake
before that 45 deg bend was complete. I visited a local business that
welds up new Super Cub fuselages to see what pointers I could pick up
from them. I watched in fascination as one of the guys was bending up
channel for the cub tail feathers. It was a small brake capable of
making bends close together. It had stops set so he just jammed the
piece in as far as it would go pulled the arm to the stop and repeated
on the other side to get the 45 deg lips, faster than I could write
about it. Sure wonderful when you have the right tool for the job. The
only negative I see to using the tubing is I know that at my level of
welding experience it was easier for me to weld the channel pieces than
those tiny tubes. The worst looking welds on my tailfeathers are the
1/4" tubes. I realize that is just an experience issue.

+++ #1452
Subject: Re: stab rib weight
From: budd davisson

Did I comment on this already? My senior moments seem to be getting
closer together.

If my math is right, and it seldom is, the cross sectional area and
therefore the weight, of two pieces of 1/4 x .028 versus a 7/8" x .035
channel shows the channel to have about 20% more area/weight. So, yes,
the 1/4 tubing would be lighter, but ti would also not be nearly as
strong without a few intercoastals (could be short pieces of verticle
tubing or even flat tabs of.049) about every six inches. No big deal,
but otherwise the longer ribs will be too flexible.

As for welding the small tubing, it's not as hard as it would seem as
long as you use a smaller tip and watch it carefully and be prepared to
sort of "dab" weld it, pulling the torch back if you see it getting too
lot and proceeding one bead ringlet at a time. It's just a matter of
directing the heat and takes only a little practice.

I forgot to ask Bob about tubing ribs yesterday, but will try to
remember tomorrow between Pitts hops and stomping out brush fires in the
office.

Someone ought to remember to ask Charlie Vogelsong if he has a design
for a bench top break that would do the ribs. Then one of us with the
capability should build a couple of them and loan or rent them to the
rest because the channel ribs are definitely the right way to do the
project.

+++ #1458
Subject: Re: Bearhawk>ribs
From: budd davisson

> What are channel ribs and where does the brake come in?  Tube ribs?? I
> might have deleted some posts..and got lost.

The channel ribs are .035 sheet, bent into C shape with an 1/8" lip bent
down at each leg. That has to be done on a break and a leaf brake works
best. Another way to form them is to hammer them over a steel form
block, but that means making steel form blocks.

Tubing ribs have a small diamter tube top and bottom with nothing but a
few intercoastals connecting them.

+++ #1473
Subject: Bearhawk Re>ribs
From: nov222p-

Hello group,

Thanks Del and Budd. I was stuck on wing ribs.

Anyone currently watering trees or planting beer cans proceed with
caution..delete this post now if unsure.

My work is in a sheet metal fabrication shop where I split time between
out cnc punches and lasers. My skill level is no where near our
experienced fabricators, but I can setup and safely operate all our
equipment.

If these C channel are a problem may I offer my help. You have my
Saturdays for a month. A quick look in the book shows one of our
suppliers has 22ga 4130 sheet 24"x144" in stock. I can sheer a sheet
into strips, DE-burr, bend into C channels, and drop off at ups in
mailing tubes.

I can bend some channels out of .030 mild steel for inspection and
approval by a couple of you. I would want to piggyback the 4130 on
another order to avoid shipping charges and meet the minimum order
requirements. My labor would be free..my payback in the satisfaction of
some bush planes in the air perhaps a little sooner.  There might be a
charge for use of the sheer and brake. There would be an equipment
charge for me to use the cnc's. I would have to buy beer for the shop
either way.

On the way into work a little early to ask permission to make some test
bends, it seemed a .125 lip would'ent catch the back side of the quater
inch bottom die due to the radius along the top side of the vee. It
turned out the die's in our best break have almost no radius but the
quater inch bottom is really .310 wide (converted from metric I
think). So to allow a bite on the back side of the die the tightest I
could go bends up a 3/16" lip. Can you live with this? The sheer was
introducing a .005 taper over 20" that could probably be shimmed out. I
was getting over .010 change in cut size depending on how hard I held
the sheet into the back gauge. The laser would eliminate these variation
and might be the way to go if there are lightening holes or a radius to
the ends of the channels. I do not have a set of plans. The narrowest
the strips would form up without die interference was 15/32. The width
must be wider than that I hope. My bends were all coming up to nice 90's
checked with a square..pretty hard to check that narrow of a lip..the
dial calipers showed some variation. What this means is I should be able
to hold repeatability within .010 if the 4130 behaves the same..maybe
someone could mail me a small piece and report back to the group.

What do you think? Is there enough interest to split up a full sheet?

+++ #1475
Subject: Re: Bearhawk Re>ribs
From: budd davisson

Your e-mail is the kind of thing that makes scratch-building what it is.
Very, very nice. Your place in homebuilder heaven is now assured.

Group, I'd suggest we get Fred a set of rib drawings (which means
someone will actually have to draft them since they don't exist
separately as three-views.

Any volunteers? 

+++ #1484
Subject: Re: Bearhawk Re>ribs
From: The Martins

Did everyone else just take one step back? ;-)

I can probably get them into CAD format Sunday night, then email them to
somebody for checking in .dwg or .dxf format (one pair of eyes is never
enough, even though it is a pretty simple part) or plot them and send
the plots out Monday.  I'm too tied up before then.  If somebody has
them already done it won't hurt my feelings any.

Any determination on whether the 3/16" lip will cause any problems?  (It
doesn't look like a structural problem from here) I could draw it out
both ways if I don't hear back.

Obviously, count me in for the ribs.  What a deal - wish I could help
more.

At the very least, Fred shouldn't have to spring for the beer.

+++ #1489
Subject: Re: Bearhawk Re>ribs
From: budd davisson

The 3/16 lip is no problem other than a little weight. You could belt
sand it off, if it bothers anyone.

+++ 1490

Subject: Re: Bearhawk Re>ribs
From: budd davisson

PS

Make sure the bend radius is right, though.

+++ #1501
Subject: Re: Bearhawk Re>ribs
From: Rod Smith

> On the way into work a little early to ask permission to make some
> test bends, it seemed a .125 lip would'ent catch the back side of ...

The horiz stab ribs are 7/8" wide and do not taper. The rudder and
elevator ribs taper from 7/8" to 3/8" , the trim tab ribs taper from
1/2" to 3/8". On the brake I was using, I had interference between bends
on everything but the 7/8th ribs. I made the two main bends as close to
90 as I could get and tried to make them even. In other words I might
end up with 60 deg bends on each side. I had to hand form the bends the
rest of the way. You could just hammer them over to 90 but you will end
up with curved webs. I made some forms out of 1/4" steel that slipped
inside the channel to keep the web straight while hammering the flanges
to 90 deg.

+++ #1502
Subject: Re>ribs
From: The Martins

got an earlier start than I thought, but still didn't make much headway.
Would somebody please check my count on these ribs?

I show 8 ea. 7/8 untapered ribs for the H stab
           4 ea. 1/2 to 7/8 at the H stab /elevator facings (elev 2@ 3/8?
and stab 2@ 5/8 wide)
           2 more 1/2 to 7/8 taper elevator center rib
           4 ea 3/8 to 7/8 elevator ribs
           6 ea. 3/8 to 1/2 trim tab ribs (misc length)
           3 ea. 5/8 to 7/8 V stab ribs (top one called out as 5/8 flanges -
does this mean 5/8 width like elev or 5/8 flange?)
           1 more 5/8 to 7/8 rudder rib
           3 ea. 3/8 to 7/8 rudder ribs

Can't find a reference to bend radius.  Is 1T good here? (.032)

With the 15/32 as the narrowest, sounds like the 3/8 tapers won't make
it, but everything else fits within that.  Any ideas?

Well, it's tomorrow and I need to start again soon.  I might be able to
get some of the profile views drawn up when I get back.  Oh yeah, if
someone has the lengths of the various tapers (use that lumber store
yardstick) it'll save me some time and maybe a few errors.

+++ #1503
Subject: Re: Re>ribs
From: Gary Danford

Ref:  THE RIBS

I found last time I tried to build ribs was to determine the inside
length of the rib.  I mean the shortest length between the 3/8 tube and
the 7/8 tube.  Then drill a 7/8 hole in one end and a 3/8 in the other.
Then draw your taper to the edges of the hole.  It makes it easier to
align in the brake and then simply slice the rib to length through the
center of the holes after the rib is bent. 

On the Hatz they didn't fold the 1/8 edge.  I don't know if Bob put that
bend for strength or to stop the edge from cutting the fabric.  The Hatz
only used .020 and without the fold and they worked perfectly.  Of
course you had to put that heavy white medical tape like we used back a
century ago when we played football in high school.  The tape went on
all sharp edges before applying the fabric.

Maybe Bud or Mike to talk to Bob and maybe there is an easier way.

+++ #1511
Subject: 3-view CAD rib drawings available
From: The Martins

well, I didn't have time to doublecheck them but I placed a drawing of
the T-25 ribs in the common vault area. Three-views of each size, with
counts and dimensions for each. It ended up being a lot more detail work
than I expected but I think I got them all right except for possible
measurement errors off the plans - I was trying to finish in a useful
time frame.

The composite drawing should plot 1:1 on E size (36x48), or 1:2 as a C
size (18x24)

There are two identical versions - T25RIBS.DWG and T25RIBS.DXF (both
should be AutoCAD r12 compatible) I didn't bother to make a new folder
for them since I figured they're just there temporarily to start them
moving toward the wonderful Frederic Kess, but anyone who wants them
feel free to grab them.

Is there somebody who can check my work? Especially somebody who has
already built the tailfeathers who could do direct measurements.

btw, yesterday went to visit a VERY tidy Capella that's nearly ready to fly.

+++ #1520
Subject: Re: 3-view CAD rib drawings available
From: Float-by Shooter
  
Thank you for doing this work!  However, I need to show my ignorance -
where are the drawing files?  How do I nagivate to the folder to
retrieve them?

You have to go to the egroups/bearhawk website and log in, then click on
the "vault" section.

+++ #1527
Subject: Re: 3-view CAD OOPS!
From: The Martins

hey, it was late An E size plot will be 1:2, not 1:1, and C size will be
1:4 which should match the plans (except for the 1:10 fin drawing) I can
break them up into groups in smaller drawings if somebody needs 1:1's in
a more manageable format.  I made some 1:4's today and am going to try
matching them up to the plans to see how close I got, time
permitting. Most will have to wait 'til tomorrow.

+++ #1528
Subject: Bearhawk Re>ribs
From: nov222p-

Thanks Gary, Rod, and Tom for the help.

I did a crash course on AutoSketch this weekend to get a look at the rib
drawings. My first thought was Holy Cow, or words to that effect.  I'm
up to my boot tops so hopefully those "experienced" guys at work will
have a plan to fixture something up and take the hammer out of this.
I'm thinking a fancy press brake not nearly as important as being good
with a mallet. I'm all ears from the group on suggestions..hammer ones
included. Thanks again Rod for the first hand account in the brake. Hope
my next report is positive.

+++ #1539
Subject: Re: Re>ribs error report and corrections
From: The Martins

I overlaid my 1:4 plots over the plans, and here's what I have so far:
(these are my measurements only, so beware)

Part labeled 'Elevator outer rib" is shown as 19.250", should be 19.000"
even -- I apparently measured to the outside edge of the rear tube
rather than its center

--> general note - I rounded to the nearest 1/4" (1/16" at scale) but
they seem pretty true to the plans. All measurements were taken to the
center of diameter of each tube rather than to the weld lines (at least
that was my intention)

Part labeled 'Vert fin end rib' is shown as 17.500 should be
16.250. Looks like I measured to the wrong (rudder) tube.

There are two parts labeled 'Rudder fwd rib' - the top one (in the V fin
group) should be labeled 'VERT FIN BOTTOM RIB'

Real part labeled 'Rudder fwd rib' shown as 16.250 should be 16.500

Printing at 1/10 , the bottom fin rib (27.500) seems a little short when
laid over the plans, but it might be because I used a printer for that
one. My scale still shows the length to be correct.

I made the above corrections and reposted the drawings as T25RIBSb.dwg
(and dxf)

These should be a little closer.

Frederic - keep us posted, I didn't know how much was involved until I
started drawing up all those ribs!  If your co-workers don't have a
better solution, ask them if a set of steel block dies and punches would
do it. I could have them waterjet cut if we spread the cost enough. I
was thinking 1/2" thick dies, and 3/8 (or slightly thinner to clear the
flanges), then pre-bend the flanges and use the dies in a giant press to
finish the inner bends. I know just enough to be dangerous, so this
might not work at all, or just as bad it might be the hardest way to do
a simple task. It would take a die set for each tapered rib size.  Or,
it might be best to do the inner bends and let us use Bill Johnson's
technique to finish the flanges. Let me know.

+++ #1542
Subject: Re: Rudder Ribs etc
From: budd davisson

Keep bugging me on the subject as I forget easily. And yes, the tubing
should work fine on the rudder, especially, if a long taper is cut in
the tubes so they are sort of "mitered" together at trailing edge.
That's the way I've done every rudder I've ever built.

+++ #1550
Subject: Re>ribs
From: nov222p-

Greetings Group

Posting a quick report on my tail ribs.  The good news is the sheer
setup on the tapers goes quickly and accurately and all the bends can be
placed with the nc backguages on the brake.  Yesterday a special top die
was pulled from the tool crib that provided but a little more clearance
allowing the inner bends to come up to 70 degs on the 3/8 small end ones
and 75 degs on the 1/2 to 7/8 ones.  Several ribs are on the shop
foreman's desk tonight for him to kick around with tomorrow.  My mallet
is getting a little smarted but not by much.  Got to be some way to
squeeze those guys without deforming them.

+++ #1576
Subject: Re: Bearhawk Re>ribs
From: pfflyer-

I had been at a standstill on my tail surfaces, waiting for a band saw
bland to arrive, won't ever let that happen again.  Once it got here I
cut up some steel and and milled some dies that I can slip inside the
channels, clamp in a vise, and hammer over the 1/8 flange. I expected
that gradual hammering would bow the channel, but it didn't.  It would
have sure been easier to bend them in a brake, but I can't imagine how
it could be done on the ones that taper to the back of the elevator and
rudder.  One bright spot in only bending the channel to a C on the brake
is that it is much easier to fit with the tubes.  After getting
everything cut and fit, and all holes through the channels cut, I took
them out and bent the final flanges.

+++ #1609
Subject: Re>ribs re>the lips
From: nov222p-

I've got some nice looking 45's coming up on the 1/8-inch tail rib
lips. Yes, those 3/16 lips are history and this is so simple, anyone
with access to a press brake has got to try it. Most likely been done
before, but I'm glad to have stumbled upon it.

Along a straight edge on a chunk of lexan, layout the centerline and
width of your bottom die. Score the centerline slightly deeper than the
blade kerf with your table saw. Cut to width and you have a micro die.

Anyone not familiar with brakes this is what to do. Tape the strip to
your bottom die. Bring up the tonnage on the brake just enough to close
the dies, using the over 90 top, and lock in your bottom. Back off on
your die opening and maybe leave the tonnage alone as this thin of metal
bends up so easy.  Stick your metal in and try it out.

The whole idea can be improved upon a lot. I might be dreaming but
anyone thinking of building a brake: could it be made from a sheet of
lexan? It machines easy, could be bolted into laminated layers, and the
stuff is tuff and might not flex or stretch.

I'm learning as I go and this is only a step forward on the tail
ribs. The big lip our smallest dies formed however, was killing me when
bending up the 90's with top die interference.

Thanks for everyone's comments, files, photos and construction notes.

>>> 2mar02 #7686-9153
+++ #7989
From: Budd Davisson <buddairbum@h...>
Subject: Re: Digest Number 587

It needs a few minor tweaks that I'm aware of. I'd like to know
from those flying how the new rudder aerodynamic balance effects
the rudder break-out forces, for instance. The original balance
area was too big and the rudder a little light. All of the plans
show a slightly smaller one and I'd like to know if the change
had much effect.

There are some minor tweaks needed in the aileron cable/flap
interference we've all talked about. And there's the need to
reflex the flaps. The 540 in Bob's airplane runs hot with when
worked even slightly hard so there are some cooling issues with
the big motors. Cowl flaps may be in the offing.

The nice part about this airplane, however, is that the basic
design is so good that improvements just make a good thing
better, rather than trying to compensate for something that is
basically wrong.

bd

>>> 4sep02 #9154-11297
+++ #9590
From: "Pat Fagan" pfflyerz@c...
Subject: trim control horn

     I recently covered my horizontal tails and found that the top of
the small control horn, on the end of the trim torque tube, just barely
rubs against the inside of the skin.  The fabric isn't distorted
upwards, but it does touch it and would drum against it in flight, so I
put a piece of fabric tape over the spot.  If I had it to do over again
I would file off the top of the horn after welding it to the tube.

+++ #9591
From: Budd Davisson <buddairbum@c...>
Subject: Re: trim control horn

This is a common problem with lots of airplanes, including factory built
Pitts Speicals and youhave to file too much off the fitting to clear the
fabric when it is drumming in flight.

A good compromise is to take the curved end off a plastic spoon, sand it
flat so it fits tight, and glue it to the fabric, as a streamlined
fairing, before painting. Works reallywell.

+++ #10883
From: Budd Davisson <buddairbum@c...>
Subject: rudder balance/trim/engines

> I was interested in the group's view of minimizing the rudder aero
> balance, just enough for some weight for a mass balance.  bd mentioned
> a plan to decrease the balance area for the rudder, but I haven't seen
> anything about it.  Has this been done already on the higher numbered
> plans sets?

Re: Rudder balance

The plans have a smaller rudder balance on them than The Bob has on any
of his airplanes. Marek and Graf both have the smaller balance but they
haven't said anything abut it. This is no big deal. It's just that the
rudder is lighter than we're used to but still not as light as a
Luscombe.

+++ #10905
From: Russ and Penny Erb <erbman@p...>
Subject: RE: Re: OK Enough of the teasing. What did you buy?

> bd mentioned a plan to decrease the balance area for the rudder,

My understanding is that this change was made on the plans before any of
them went out.  If you forget it was ever said, you'd never notice the
difference--your plans should already have the smaller rudder balance.

>>> 20may03 #11298-18250
+++ 13283
From: "Dan Shilling" <dlshilling@g...>
Subject: Elevator Rudder Hinges

In the second sentence of the "Building the Rudder & Elevator Hinges"
section on the Erbman CD, it says "(If you are interested in a simpler
design, contact AviPro.)"  I am interested.  Budd...??

Also, I seem to have a slight twist in one of the ailerons I just
finished.  One corner is raised about 1/4" off the table.  Anybody
have any suggestions before I lean real hard on it.

Dan Shilling

+++ #13299
 From: Budd Davisson <buddairbum@c...>
Subject: Re: Elevator Rudder Hinges

> In the second sentence of the "Building the Rudder & Elevator
> Hinges" section on the Erbman CD, it says "(If you are interested in
> a simpler design, contact AviPro.)"  I am interested.  Budd...??

It's a Bob Approved change we haven't instigated yet. We'll let you
know when we dod.

+++ 


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