+++ #143 Subject: Tips on Bending Channel Pieces From: Rod Smith I took advantage of having a large bending brake at my disposal and got all the T-25 channel pieces bent up. What you will find when bending these, especially the narrower ones is that after bending the first flange to 90deg, you cannot bend the second flange to 90 deg because the first flange hits the foot of the brake. You will have to carefully and gently tap the second flange with a hammer to get to 90deg. I found that the best way to fabricate these is to bend both flanges equally as far as possible, usually to about 75deg, then bend the 1/8th lips as far as possible, usually about 30deg, then carefully tap both flanges over to 90deg. The downside of this method is that the center portion of the channel ends up curved somewhat. This is not a structural or strength problem but Bob Barrows says you can cut another strip of metal and insert it in the channel in a vice while tapping the flanges over to prevent this. I had access to a 24" wide hydraulic shear for cutting the pieces. I recommend finding one you can use for this job. Five of the pieces were longer than this and I had to cut them out with a bandsaw. The cutting and dressing of these five pieces took about as long as the total fabrication of all the rest. The sheared pieces just require a couple quick swipes along the edges with a file to remove the burr. You can cut right on the line with no waste. Also in the last month a machinist at work taught me how to use the vertical milling machine and I have completed the end fittings for the Bearhawk struts. I have also made quite a few of the fittings that attach to the fuselage. Nice to see a growing pile of parts. +++ #147 Subject: riveted spars From: Archie (dunba-) There is an interesting article by Bill Welch in the August issue of kitplanes that discusses the problems associated with riveted spar caps. It will bring home the importance of good practice and ultimate care in insuring that your spar caps are drilled perfectly and deburred prior to meticulously setting every rivet. Also at the zenithair.com site ther is a good article by chris heintz on riveting in which before he makes his pitch for pop rivets he extols the virtues of set rivets. +++ #508 Subject: Re: MAIN SPAR CAP STRIPS From: J.T. Newbegin I got mine from WICK'S , you might find the 6061 at a shop that fabricates truck beds or cattle trailers. Cutting angle with a bandsaw has been done and the cut cleans up nice. +++ #607 Subject: Re: New member From: csisters- The lighting holes in the spars DO NOT get flanged. +++ #831 Subject: Re: rear spar From: Bill Cox > Does anyone know whether the 1/8 x 3/4 inch cap strips on the rear > spars are one piece (165 13/16 long) or are they in sections? Melvin, I understand them to be one piece. Wicks has the material at reasonable cost. +++ #832 Subject: rear spar From: Russ Erb Yep, one big long piece (4 per spar) just under 14 feet long. Only the .032 webs are two pieces spliced together. +++ #833 Subject: Re: rear spar From: Mike Meador You can buy that material now from Wicks if you don't want to cut it out of the channel. They have been offering it since early last year. +++ #848 Subject: Re: cap strips From: Bill Cox > thanks for the information on the rear cap strips, but why does the > back spar have a one piece strip and the front spar comes in three > sections? it seems like the front strip would be one piece too. thanks > for the help. mel k 351 The front spar has a long cap strip with a shorter cap strip in the strut area. On these shorter strips the front and rear are offset from each other, which may make it appear to be in three pieces. The drawing can be a little confusing, but a little study will clear it up. So for the front spar there is a long strip and a shorter strip both top and bottom and front and rear. Mike Meador sells a set of wing construction photos that helps to clarify many of the details. On the rear spar there is a full length cap strip top and bottom, front and rear. +++ #852 Subject: Re: cap strips From: Melvin Kinikin Thanks for the input, but I am still confused. Looking at the plans it appears that on the front side of the spar you have three sections-- one 30 3/8 then 72 1/8 then 39 1/8 and on the back side of the front spar you have 41 3/4 then 72 1/8 then 28 1/4. The wing construction photo is not that clear to me. According to what I see on the plans there are three sections with the dementions shown above. +++ #853 Subject: Mainspar (fabrication sequence) From: gcwhit- It has been some time since I posted a query to the group, but now I am at a point where one is warrented. Before I continue, I wish to thank the regular contributors to this forum. Your comments, suggestings and solutions have been stimulating and very helpful. This forum is one reason I chose the Bearhawk (along with Bud Davisson's article). To date, I have fabricated all of the ribs and two weeks ago finished bending up the main, trailing and flap spars. "Aircraft Sheet Metal" and Tony Bengelis' books were very helpful in setting up the brake and calculating setbacks and so on. Yesterday, a local sheet metal shop cut the 1.25 inch 2024 T3 spar caps from a large sheet of 0.125 2024 T3 I acquired via Boeing Surplus. I now have (36) 1.25 x 144 inch cap strips (enough for two sets of wings plus "goofs") for only $27.00 in labor. The questions I would like to pose are regarding the fabrication sequence of the main spars. Which should be fabricated first? The spar plates? Drilling the spars or spar caps? Those of you who have completed the spars, what sequence worked best for you? Regarding the lightening holes, is it best to cut them following match drilling with the cap strips? I would apprecate your comments and suggestions. Where is a good source for the 0.25 x 0.5 inch 6061 T6 pieces that the 0.032 x 0.5 x 0.5 attach angles are riveted to (between the attach angles and the spar web)? +++ #855 Subject: Re: cap strips > Thanks for the input, but I am still confused. There is a cap strip 142 1/8" front and rear, top and bottom. In front is an additional cap strip 72" beginning 30 3/8" from the inboard end of the long cap strip. In the rear is additional cap strip 72" beginning 41 3/4" from the inboard end of the long cap strip. All cap strips are 1/8X1 1/4" 2024 t3. +++ #857 Subject: Mainspar (fabrication sequence) From: Russ Erb > The questions I would like to pose are regarding the fabrication > sequence of the main spars. You really need to think through the procedure so that you don't forget something or do something out of order. I am including below the file that I used to guide myself through building my spars. Please note that it is provided WITHOUT EDITING (which means there will be some things in there that only have meaning to me) and without warranty. I have not reviewed it since the spars were built. Hopefully nothing embarrasing is in there. You may use it as a guide to develop your own procedure. Please don't just follow blindly without thinking about it yourself. Both Spars Procure: 85.5" of 1/8" x 1/2" 6061T6 (1 12' length) 85.5" of 1/4" x 1/2" 6061T6 (1 12' length) Aluminum Angle 6061T6 1-1/2 x 1-1/2 x 1/8 14' long 3 pieces (Need 4, have 1) 2*1/4 lb MS20470AD5-8 rivets 1/4 lb MS20470AD5-9 rivets 1/4 lb MS20470AD5-10 rivets 3*1/4 lb MS20470AD5-12 rivets 1/4 lb MS20470AD5-14 rivets (not in Spruce catalog) 1/4 lb MS20470AD4-4 rivets 1/4 lb MS20470AD4-5 rivets 3*1/4 lb MS20470AD4-7 rivets 4*1/4 lb MS20470AD4-8 rivets 1/4 lb MS20470AD4-9 rivets 1/4 lb MS20470AD4-10 rivets 1/4 lb MS20470AD4-12 rivets 1/4 lb MS20470AD4-13 rivets 1/4 lb MS20426AD4-8 rivets 1/4 lb MS20426AD4-10 rivets 1/4 lb MS20426AD4-12 rivets 1/4 lb MS20470AD3-3 rivets 15 AN4-13A bolts 30 AN960-416L washers 15 AN365-428A elastic stop nuts 0.190" 4130 Steel Sheet 9"x18" 03-25700 Look at Harbor Freight for low cost small clamps more bar clamps 2x4s for spar holding fixture #6 x 1" machine screws, nuts, and washers Level Tables Main Spar Print drawings of main spar Add centers of lightening holes Invert for right wing Cut capstrips to length 8 pieces 142-1/8" Bandsaw should work Support far ends Cut 4 pieces into 8 pieces 72" long Use hacksaw or cutoff wheel Pieces will be slightly short by half the width of the kerf Bandsaw will not work--too much loss from required angle to cut Smooth edges of capstrips Dress grooves out of scotchbrite wheel Place buffing wheel over table Pull strips under wheel On scrap piece, use fly cutter to cut 3" hole Test ability to get each hand with bucking bar through hole Leave fly cutter set for spar holes Mark centerlines full length of spar webs Lightening Holes Locate hole centers and center punch Do not put holes in area of landing light Drill with 1/4" drill Cut 3" holes with fly cutter Smooth holes Locate and Clamp Cap Strips Clamp Cap Strips into place Mark and Centerpunch holes Locate holes at rib locations first. Measure all from same point Use rib spacing guide to locate in between holes Identify and mark special holes Don't drill holes under root doubler plates Mark, don't drill holes for flap drive (3/16) Locate several holes around web splice per plan Mark, don't drill holes for aileron drive Set up spar holding fixture for drilling spar caps Drill holes in spar caps not otherwise prohibited Clamp and align with #6 machine screws, washers, nuts and taped rivets Cut vertical stiffners slightly over size Sand to length Drill and cleco/bolt Cut web splice plates, root plates, and strut fitting spacer Fit as required Drill and cleco/bolt Cut strut fittings (4) Use Charlie's shear? check length (15"+) Drill all holes through all four fittings at same time Wait to drill holes through spar until spar pieces riveted together Do not drill holes for flap or aileron drives until steel parts are built and in the jig Disassemble, deburr, aloding, and prime Rear Spar Print drawings of rear spar Add centers of lightening holes Invert for right wing Rip 8 capstrips to 3/4" wide Will require two cuts to get square corners Use bandsaw with metal cutting blade Need method to support strips Cut capstrips to length 8 pieces 165-13/16" Bandsaw should work Support far ends Smooth edges of capstrips Dress grooves out of scotchbrite wheel Place buffing wheel over table Pull strips under wheel Mark centerlines full length of spar webs Lightening Holes Locate hole centers and center punch Drill with 1/4" drill Cut 3" holes with fly cutter Smooth holes Locate and Clamp Cap Strips Clamp Cap Strips into place Mark and Centerpunch holes Locate holes at rib locations first. Measure all from same point Use rib spacing guide to locate in between holes Identify and mark special holes Don't drill holes under root doubler plates Mark, don't drill holes for flap drive (3/16) or flap hinges Mark, don't drill holes for aileron drive or aileron hinges Set up spar holding fixture for drilling spar caps Drill holes in spar caps not otherwise prohibited Clamp and align with clecos If clecos don't hold, order long reach clecos (1/2" reach) Cut vertical stiffners slightly over size Sand to length Drill and cleco Cut root plates, and spacers Fit as required Drill and cleco/bolt Drill and cleco web splice plates Do not drill holes for flap or aileron drives until steel parts are built and in the jig Disassemble, deburr, aloding, and prime Assembling Ribs Identify attach angles for locations Angles to NOT be attached Spar attach angles (nose, center, back ribs) Ribs 2 and 5: false spar attach and Rib 1 same place Spar attach angles, Tip rib Determine and post rivet length and squeezer settings for .025/.025, .025/.032, .032/.032 Make drill jig Chipboard on 2x4s Print out rib templates 1:1 Drill 3/16" hole, insert AN3 bolt from below for jig hole of nose ribs, use nails to position rib. Use tall nails at angle positions--stretch string between nails over rib to mark angle position. For center ribs, use nails to position ribs with 1/8" aluminum spacers for spar cap thicknesses. Same strings to mark angle position Clamp in place and drill rivet holes Unclamp and deburr Apply primer between angle and rib Cleco in place Apply primer in rivet holes Insert rivet and squeeze Repeat with next stiffner Assembling Spars Main Spar Set up and level tables Set up overhang 2x4s Assemble parts as before Apply primer between parts Use bolts, rivet pins (tape in, and clecos. Use bolts through holes that shouldn't be riveted right away-specifically in capstrips at rib locations (above/below verticals) Mark capstrip holes that should not be riveted as listed below - put bolt through if possible Rib locations Stiffener angles for landing lights Flap Drive bolts Aileron Drive bolts Wing Strut Attach Strap bolts Aileron Cable Pulley bolt Build holder to hold spar in vertical position for riveting Prime and Drive rivet at root end of top and bottom capstrip Prime and Drive rivet at tip end of top and bottom capstrip Prime and Drive rivet in center of top and bottom capstrip Continue driving rivets to separate into 4ths, then 8ths, then 16ths, continue at 2^n Determine capability to squeeze or drive NACA rivets through 0.125/0.032/0.125, 0.125/0.032/0.25, and 0.25/0.032/0.25 Post results and rivet lengths Position vertical stiffners Prime and cleco Prime center hole and squeeze or drive rivet +++ #859 Subject: spars From: Sonny Cilley for those having a hard time seeing how the spar cap strips are assembled,my vision is to think of them like leaf springs in the way they are assembled,the CD sounds like the way to go.Myself I am about to bend up the spar webs and finally start the assembly process. +++ #999 Subject: Spar vertical stiffeners From: Bill Cox The main spar drawing appears to have the vertical stiffener/filler at each nose rib location. I think from looking at Russ photos he did it that way. Looking at Mike's photos of Bob's wing constrution it appears he did not use the stiffener/filler at the intermediate rib locations, only where there was a center rib. Which is correct and if it is only at center rib locations is there structural advantage to using them at each nose rib location. +++ #1000 Subject: Spar vertical stiffeners From: Russ Erb Pat Fagan told me a long time ago that he talked to Bob Barrows who told him that the stiffners should be installed on both sides of the web at each nose rib location. The stiffeners don't just fill the gap under the rib. They also break the shear web up into smaller shear panels that can take higher loads without buckling. At least that's the way I interpreted it. Nothing on the plans implies to leave any out--they're always shown in pairs. +++ #1001 Subject: Re: Spar vertical stiffeners From: budd davisson I was going to say as much earlier but got side tracked. Russ is right; the way you make a thin web stronger is by breaking it into smaller and smaller shear panels (within reason), so put stiffeners at each rib station. As the saying goes, "it can't hoit." +++ #1161 Subject: Spar caps From: budd davisson don't mess with the spar caps. The strength of a spar comes almost entirely from the spar caps and is driven by the amount of material in the caps and it's distance from the neutral axix (center) of the spar. In otherwords, its a cubed function. The web is only there to hold the caps in position and not wrinkle in the process. With the rib pitch as tight as it is in the Bearhawk, the web isn't about to wrinkle. I need to beef it up a little, but I'll just increase the width of the caps an 1/8 or so, or maybe make them slightly longer and add another strip. It won't take much. +++ #1173 Subject: built up spar From: stephan pelgar i saw that you were talking about making the spar caps a little wide.about a 1/8 or so.by doing this will this also increase the gross weight of the aircraft when its done? i have a nother ? about building up the spar.i was in a fuel tank for one of the planes here in my squadron.i noticed how the spar was built.the web was a 35 ft piece of alum with a l channels riveted to it.the thickness of the web tapers but it is a big plane.i was thinking instead do you think could do something like that.cut the webs then mount the l channels and spar strips on the webs.please let me know what you think about this idea. +++ #1174 Subject: Re built up spar From: budd davisson > i saw that you were talking about making the spar caps a little > wide.about a 1/8 or so.by doing this will this also increase the gross > weight of the aircraft when its done? It probably would but other areas of the airplane would have to receive the same attention to actually increase the gross. I'm going to assume it is still 2400 pounds no matter what I beef up. > i have a nother ? about building up the spar. Don't screw with bob's design work. He's done it right and not one of us can improve on it. Even though I'm a structural engineer by training, I'm going at this thing very carefully because every design detail is the result of a long thought process and not being privy to that process means there's always the possibility of making an "improvement" and upsetting something else at the same time. +++ #1176 Subject: Re: Re built up spar From: Tim Anderson I'm no gross weight expert, you can talk circles around me I'm sure. It seems like the GW determination is kind of smoke and mirrors. Some companies due a mock-up loaded with sand bags until failure, which is the 150% point(I think) then they scale the GW back. Some have advocated a drop test of some kind, to mimic sudden loading force. I ran into serious GW issues on the Kitfox with floats. The company said their test model failed at internal fuselage braces, not the wings. So, bottom line is the wing is only part of the GW determination. But a few additions of metal here and there may not hurt. +++ #1177 Subject: re builtup spar From: stephan pelgar thanks for the insights.it was just a idea that i thought might make easier tobuild.that is why i asked.when it comes to building aircraft parts i know alot and always trying to learn more.i also like to share my knowledge that i have picked up on the way.but if i dont know the answer i try to ask someone who might know the answer.i just got a copy of a old aircraft sheetmetal book written in the 40's.it has so much info that they dont teach anymore.they go into a lot of detail of hand forming parts.i am researching this stuff so i can write about this and stuff i have been passed down from guys with alot of years of this work. +++ #1178 Subject: Re: Spar caps From: Tim Cramb Yes that's the other option going up to the next width 1.75 (1-3/4") same thickness (1/8). Then adjust the lightning hole size if needed, so the holes don't touch the cap strips like they 'appear' to do on the rear spars of protoII in Mike's Construction Photo Manual pg 23.................. +++ #1388 Subject: .125 2024T3 Bar vs Sheet From: Tim Cramb Done looking up here for .125 2024T3 Bar (cap strips). I priced a .125 4x12 sheet for shearing.......$800. So I guess ACS has the best price, 1999 Catalog puts them .02 cheaper than Wicks and Spruce will also cut 10% off when ordered in 12' lengths. I was talking with Bob, he mentioned that in the future he should engineer a wing (future design) using 6061T6, as 6061 is More Available and in different sizes, CHEAPER and has better corrosion resistance.....like duh? +++ #1657 From: (Joe Lisanke) LISANKEJM Subject: [Bearhawk] Re: rear spar I just recently received this material from Wicks. The numbers are just the dimensions of the stock with an alloy suffix. Eg: BR1/8X3/4-T6 for the rear stock and BR1/8X1 1/4-T4 for the front stuff. You have to specify full lengths for each; 14 ft. and 12ft. respectively. The advantage here is time saved not having to finish the edges of the stock which would be considerable. +++ #1843 From: robert gaddy Subject: [Bearhawk] Main Spar Dimension Check Short Version I measured the distance from the upper to the lower surface of the airfoil on drawing #7 and came up with 7.789 inches (outside of lines) and 7.699 (inside the line. I noted on drawing #3 at the Main Spar cross section a reference dimension of 7.59 with the note "check for fit with finished rib." Have others who have made the main spar C-channel come up with similiar numbers? Long Version I'm having a local craftsman bend up my C-channel for the spars. He called to my attention that the measurements from drawing #7 at the main spar location do not agree closely with the spar cross section drawing.(See above) He is making fixtures to do my job, with the option of making channels for others. It would be best to have an agreed on measurement for the dimensions of the channel so that he would have a standardized product. Could the reference dimension be nailed down a little closer? It would seem to me that shimming is required is the 7.59 dimension is used without checking for fit to the ribs as directed by the drawing. +++ #1844 Float-by Shooter Subject: [Bearhawk] Re: Main Spar Dimension Check > Could the reference dimension be nailed down a little closer? It would > seem to me that shimming is required is the 7.59 dimension is used > without checking for fit to the ribs as directed by the drawing. According to the newlsetters you are supposed to bend your spar webs to match your finished ribs. I haven't bent my spars yet (due to lack of a suitable brake and storage concerns) but I have formed all of my ribs, and also had concerns about my ribs being taller than the spar dimension. I asked about it on the email list nearly 2 years ago and was told not to worry about it. Just bend your spars to match your ribs and everything should work fine. The reason there is no hard and fast dimension for the spar height, is there is also no such dimension for rib height, due to the inevitable minor variations in individual rib form blocks and builder technique. Now, if one were to set up production tooling for hydroforming the wing ribs, you could sell complete sets of ribs and also standard size spar webs to match, but they would probably only work with with the preformed ribs unless a builder got lucky and they happened to match his hand-formed set. This is exactly what A&E aircraft had planned, but they abandoned the Bearhawk parts business due to lack of demand some time ago, I believe at least a couple of years ago. I called them to confirm this last year. Now, with over 400 sets of plans sold perhaps things have changed and it is possible that sufficient demand exists for pre-formed wing components. A&E has reportedly changed hands in the meantime, and maybe the new owner would be interested, or might be able to tell of the whereabouts of the hydroforming dies which the old owners had made. It would certainly be worth looking into. Of course, none of this is of much use to those of us who have already formed their ribs the hard way! +++ #1845 From: Russ Erb Subject: [Bearhawk] Main Spar Dimension Check >Have others who have made the main spar C-channel come up with similiar >numbers? I remember that to make the spar match my ribs, I had to use a dimension different than what was shown in the "ref" dimension. I don't remember what it was short of digging it up as that was some time ago. As Del said, the important thing is matching them together. If you look through the archives (or on the CD) I think you'll find evidence that the joggles in the ribs are not absolutely required. So you'll have to decide if you want the spar to fit with joggles in the ribs or without. +++ #1846 From: Budd Davisson Subject: [Bearhawk] wing kits, etc Re: hydroformed parts Stand by as I'm working with some people who will be stamping out ALL parts of the wing. some details to be worked out yet, but looks like a 90% success probability at this juncture. Don't ask price, because I don't know yet, but it'll be more reasonable than you'd believe. Not as cheap as planting beer cans, but close. How many out there would have interest in wing kits, or assembled wings, if the price was right (yeah, I know: what IS right?). Ditto complete fuselages/tails/landing gear. +++ #1854 Float-By Shooter Subject: [Bearhawk] Re: Main Spar Dimension Check > I assume you followed drawing #7 as closely as possible. I traced my form block directly from drawing #7, and after finishing it I checked it against the drawing, and found it to be right on the money. My ribs turned out about 1/8" taller than the spar dimension given on the plans. When I questioned this on the email list, the replies I received reported heights ranging from about 1/10 to 1/8" taller than the plans spar dimension. Not much, but probably enough to make fitting the ribs to a standard spar web a nightmare. My point is that if all follow #7 closely, then the spar height could be nailed down to fit the ribs built to that drawing. I think the problem is you are dealing with individual builders each with differing levels of experience using their own favored tools and technique, isolated from each other for the most part. Even assuming identical forming blocks, there are a lot of variables to nail down. Bottom line as I see it, the Bearhawk wasn't designed to be mass-produced, it was designed to be built in quantities of one by a guy in his garage or hangar. Don't misinterpret me as being against the idea of standard parts, I for one would jump at the chance to buy my spars pre-made since I do not have the equipment available to me to bend them at this time. I'm not complaining, that's just one of the trade-offs I made when I chose to build the aircraft. And I don't exactly lack for parts to build in the meantime.... +++ #1856 Schutt, Barry C Subject: [Bearhawk] Re: Main Spar Dimension Check OK, OK I guess I'll add my 2 cents worth. I also found the ribs to be taller than the spar ref, dimension and just made the spar that much taller. But am putting the spar cap strips at the required height and taking up the excess height half on the upper and half on the lower. Now for your comparison, I don't have access to an eight foot bender, so I took all of my spar material, sheared by the supplier, and dropped it off at Accurate Metal Products in Kent Wa to be bent per drawing with height adjustment. The cost for all spars, front rear, flap and aileron totaled $400. They matched my (formed on home made form ) ribs perfectly. The spar height was measured off of my rib form block at the correct location for front and rear, flap and aileron spars. > ---------- > Subject: [Bearhawk] Re: Main Spar Dimension Check > > I assume you followed drawing #7 as closely as possible. +++#1862 From: Tim Anderson #398 Bearhawk390 Subject: [Bearhawk] Re: Main Spar Dimension Check my spars were 1\4 off drawing i to split the differance,thicker wing more lift? just a thought. +++ #1873 From: Tim Anderson Subject: [Bearhawk] Re: Main Spar Dimension Check My three cents worth. I have to agree with one of the previous comment on the fact that the correct dimension is the one that fits for the builders ribs. Period. No two of us would build our ribs to the exact same size. But that's not a problem, as long as we are consistent (rib to rib) and (rib to spar). It does make getting pre-fab-ed spars difficult. kind of the chicken and the egg senario, what comes first. +++ #1876 Barry Schutt Subject: [Bearhawk] Spar dimensions OK, so here is what I did. I took the mylar rib drawing to the print shop and had a duplicate made (of mylar that is). It came out like a clone. Cut it out and used rubber glue to stick it to my form block. Cut the form block a little on the plus side of the line and sanded to the line (mid line or about).Marked on the form block where the spar web would fall and measured the height of the form block at that point. Then used that dimension as the inside height and as the spars are of .032 material, added .064 and that gave me the riquired outside dimension. Note that this is the finished height of the spar not the required amount of material going in befor bending. One must take into account the bend radius to obtain the correct amount of material or use trial and error and bend some sample pieces prior to bending the real thing. A aerospace style shop would know what all the setbacks etc etc required for height and radius.Enough said, here are my outside heights measured off my spars Front spar 7.63 inches drawing showed 7.59 Rear spar 5.09 inches 5.06 Flap spar 4.28 inches 4.25 Aileron spar 3.71 inches 3.69 Good luck----just be consistant----as a side note, I put a little joggle in my rib flanges where they duck under the spar flange---by sanding off a little of the form block at that location, about an inch long by about .025 deep---my ribs nest real well without raising the spar flange. +++ #1877 From: Zippydogg Subject: [Bearhawk] Re: Spar dimensions Thank you for the information. This "jives" very well with my measurements. I also plan to incorporate a joggle in my rib to go under the C-challel of the spar. This is one reason why I am building (having build) the spar first. +++ #2469 Tim Anderson Subject: Short-Winged bearhawk Club Well, Serious Mistake #1 (of many). I started working on my spars this past weekend (they are already rough cut with the flanges made). I thought I left a small amount of excess material on the spar distances that I would have to trim off. So I sat down and re-calculated the appropriate spar lengths. The outboard section isn't given directly on the plans but I "cyphered" it to be 92 5/16 inch (I think). Well I measured my rough cut main spar and it was 92.000000000 inch!!!!! I thought I had mis-measured, but I got out my hand drawn paper used for the layout on the 032 sheet and it had 92 inch!. I guess 2 years of calculus in college and all the imaginary numbers I used in electrical engineering didn't help much when adding and subtracting FRACTIONS. I think my mistake was "cyphering" from the drawing measurments given the area around the wing rootplate. The cap strip length for the rear spar should have been a clue for me, BUT NO. Anyway - luckly it was the outboard section and not the inboard spar section which would have caused the splice joint and strut attachment fitting to be out of wack. I'm going to live with the 1/2 inch shorter spar, just have the last rib bay a touch short and probably tweek a few minor other things. Oh, and that's not all folks, I drilled a line of holes directly on the spar splice joint for the splice plate. The Scrap box is getting full. +++ #2485 From: Tim Anderson Subject: Re: [Bearhawk] Short-Winged bearhawk Club I'm taking the 1/2 inch off between the last ribs. Probably have to take a corresponding 1/2 inch off the end of the aileron. I'm leaving all the hinge points and other measurements the same. If I had short-changed the in-board spar, that would have caused all kinds of measurment adjustments on the strut attachment and so forth. probably would have scraped those spars sections and re-built. +++ #2537 From: Rob Gaddy Subject: Source of Spar C-channels I started my project a little differently. I obtained some .032 aluminum sheet, and arranged for a local (Phoenix) craftsman to bend up the spar C-channels. I wanted to be able to check the ribs to the spar rather than the reverse. My source made some fixtureing to facilitate the bending with the prospect of selling to other builders (by mail?). He is a retired "airplane guy" who has a great amount of experience. I am very pleased with the dimensional accuracy of the items, although a couple of the channels have some scratches that I will have to deal with. I found him to be trustworthy, a bit expensive ($400 + material), and a bit slow. If anyone is interested, just drop me a line and I will forward the details. +++ #2690 From: Gary White Subject: Spar End Plates I am ready to match drill the main spar end plates (the 3/8 in diameter hole) where the main spar is bolted to the fuselage. Is a close tolerance bolt used at this location, and if so what diameter should it be reamed to? I am also planning to match drill the rivet holes to 0.125 in (slightly undersize) and enlarge them upon installation to number 21 when the - 5 rivets are installed. Those of you who have passed this point, what did you do? +++ #2693 From: Subject: Re: [Bearhawk] Spar End Plates Welcome Aboard ! I drilled my spar endplate holes about 2 # drill sizes under and reamed to .375 after the whole spar was assembled. When drilling the spar caps and web assembly I drilled to size and clamped, bolted, clecoed and or taped rivets into the holes to maintain alignment. There were very few holes that needed re-drilling at riveting time. +++ #2742 Russ Erb Subject: [Bearhawk] Spar End Plates From Bear-Tracks: "Dear Bob, ...My final question is in relation to the wing to fuselage spar plates, do you drill and ream if required the 3/8" and 5/16" bolt holes out to full size at the time of assembly onto the spars or do you pilot drill only at that stage? Regards, Ray Thurston - New Zealand Dear Ray, ...When fitting the wings, I used a smaller 3/16" pilot holes in the fuselage fittings and wing root fittings, then drilled to size on assembly. Best Wishes - Bob " Thus, the spar to fuselage attach hole on my spars are only 3/16" at this time and will be until assembly to the fuselage. As for the rest of the rivet holes (actually all rivet holes on the spar), they were all pilot drilled at #40, then drilled out to the appropriate size for the rivets. +++ #3390 Subject: Re: [Bearhawk] To all PostWingSkinners (Sets) From: Since the amount of material being riveted in the wings is constantly changing when attaching the rib angles to the spars, I made this list of what rivets worked best for various combinations of material. As an example, .032+1/8+1/8+.032 would indicate that the rivet will go through the spar, a 1/8 stiffener bar on each side of the spar, and 1 rib attach angle. Standby, this may take awhile. Table number is rivet length in 32ns. 470-4 rivets 470-5 rivets .032+.032 4 .032+.032+.032 4.5 .032+1/8+1/8 7.5 8.5 .032+1/8+1/4 9.5 10 .032+1/4+1/4 11.5 12.5 .032+1/8+1/8+.032 8.5 9 .032+1/8+1/4+.032 10.5 11 .032+1/4+1/4+.032 12.5 13.5 .032+1/8+1/8+.032+.032 9 9.5 .032+1/8+1/4+.032+.032 11 12 .032+1/4+1/4+.032+.032 13 14 For the center of the stiffener bars, which are double flush riveted, I used: 426-4 rivet .032+1/8+1/8 8 .032+1/8+1/4 11 .032+1/4+1/4 13 For the wing skins, I used: 426-4 rivets .025+.025 4 .025+.025+.025 5 .025+.032 4 .025+.032+.032 5 .032+.032 4 .032+.032+.032 5 Lots of odd ball sizes there. I know I cut a whole lot of rivets to get what I wanted, but a more experienced riveter could do a good job with even sizes. Hope this helps, sorry I don't have the figures for how many it takes. +++ #4991 From: "DANFORD, GARY" Subject: Rivets I am finally getting around to the Wing Spars. I think I remember (but cannot find) a previous E-Groups message someone put together listing number of and sizes of rivets required for the BearHawk Spars!!!! Am I nuts or is there such a list or just another of my illusions? +++ #4992 From: Benton Holzwarth Subject: re: Rivets (wing spar) These may be what you were remembering -- Russ' detailed description of his spar construction was in post #857, and Pat Fagan detailed which rivets worked best for him, for various combinations of cap- strip stacks in post #3390. I was able to pull this up in about two minutes searching for 'rivet' in [moving to www.siletzbay.com bjh] +++ #5015 From: Russ Erb Subject: Spars > I copied your message 857 on the assembly of the spars and > have some questions before I start messing up several hundred > dollars of alum. I had to go to yahoo to see which message that was. Remember, I never updated that procedure or verified that it matched what I did, nor do I have any interest in doing so--too long ago. I think I remember that I built spars, but that's about it. Use it as a guide, not as direction. > 1. How did your rivet estimates come out? extra or short? I had plenty of rivets as I recall, because the minimum possible orders are so large. One note-- the MS20470AD5-14 rivets are bogus. The size you really need would be a -13 rivet, and nobody makes those. Buy the -16 rivets and a good rivet cutter and cut them to -13 length. > 2. Did drill the spar cap strips and the spars at one time, or did you > drill the caps then clamp them to the spars and drill through the caps to > drill the spars? The same question for the splice plates, root plates and > strut fittings. Always match drill whenever you can. Clamp everything together and drill the entire hole at once. That way if the hole is slightly out of position, it is the same out of position in all of the pieces. Drilling parts separately and then putting them together is incredibly risky--the holes almost never line up. > 3. Did you individually alodine and paint the cap strips > and spars THEN assemble them or did you assemble and then > paint the spars as a single assembly? All of the parts were drilled, then disassembled, individually alodined and primed, then assembled and riveted. The point is to get the corrosion treatment between the pieces. If you assembled the spar and then treated, you've wasted your time. One scratch in the wrong place will let water in between the now unprotected faying surfaces and then the corrosion can start. > 4. How did you insure that the flaps and ailerons (hinges) > align to the rear spar hinge brackets? Hope the measurements > are correct or did you align during construction of the spars? Match drilled again. The holes for the hinge mounts were not drilled until the wing skeleton was assembled and the skin clecoed in place. Using the completed flaps and ailerons, the spar was drilled through the hinge mounts. Don't rush this, and be very deliberate and careful--you only get one shot to get it right. Very nerve wracking. > 5. What/how did you mean "set the spar holding fixture"? Did > you assemble horizontally or vertically? Heck, I don't know what I meant. To see how I did it, see your Bearhawk CD. Basically I used several 2x4s overhanging the work tables to set the spar on. This allowed access to both sides of the spar. Move the spar back and forth to keep clear of the 2x4s. > I've built wings before (wood) and have completed all the wing > parts but for some reason the spars have got me going. > Appreciate the help. I also recommend pilot drilling all holes. I drilled each hole with a #40 drill first, then enlarged to #30 or #21 as required. Be sure to disassemble and deburr all of your holes. Be very careful lining up the webs and spar caps, especially the capstrips on the bottom side. I had to scrap one 12' and one 6' capstrip and redrill because I didn't line it up well enough. They're not that difficult, just tedious. I recommend "mindless repetition" and don't worry about when they will be done. Someday you'll suddenly notice they are done. +++ #5140 From: "DANFORD, GARY" Subject: RE: [Bearhawk] Comm check I am working on my wing spars and have a couple of questions. 1. On the rear spar the "web spar" ends (on the fuselage end) at the same point as the spar cap strips, short of the fuselage attach bolt. 2. On the main spar it doesn't show the end so I suppose it extends all the way to the wing attach bolt hole. Thus the short spar web is different lengths for the Main and Rear Spars!!! by about 1 3/16 inches!! 3. FYI, Wicks is out of the 14' 6061-T6 spar caps and are waiting on another mill run. The mill run isn't due in until mid March. +++ #5144 From: Russ Erb Subject: RE: [Bearhawk] Comm check Nope. Try again. Look at your CD on wing spar page 2--about the 3rd picture shows the rear spar web at the root. All spar webs extend to the very root end of the spars and are trimmed to match the shape of the plates. You can also see it on page 23 of Mike's picture book. Without the web there would be an .032 gap between the reinforcement plates. +++ #5145 From: Kevin bearhwk272@a... Subject: Re:Spar webs I double checked my plans and then checked the spars. Both spar webs run out to the end of the spar root fitting, past the bolt. Check the plans. There is a dimension from the splice to the end of the root fitting that should cause you to say oh, yea, unles you built them all ready, then you will say something else. +++ #5155 From: "DANFORD, GARY" Subject: RE: [Bearhawk] Re:Spar webs When I look at my plans I see a dashed line on the rear spar indicating the end of the spar web. I agree with Russ that that leaves a .032 deficiency at the wing attach bolt hole thus my question. If the dashed line doesn't mean the end of the spar, what does it mean since the main (front) spar doesn't show the dash line for the spar web. +++ #5159 From: Kevin bearhwk272@a... Subject: Re: [Bearhawk] Re:Spar webs It means .5 x .125 vertical stiffener / spacer ie hidden line of part. +++ #5161 From: Russ Erb Subject: RE: [Bearhawk] Re:Spar webs Now I see what the confusion is. The dashed line of which you speak is the end of the capstrips and the side of a 1/8x1/2" vertical stiffener on each side of the web, just like at all of the rib stations. This stiffener is under the large plate at the root. The spar web follows the outer shape of everything else. +++ #5956 From: Russ and Penny Erb Subject: RE: Wing Length From: Matt [SMTP:mattnaiva@y...] > > Plans # ??? > > I have a 20' (outside dimension) garage would I run into > dificulty assembling the wing and closing the door. How long > is the wing panel? With and without tips. The wing spar is just under 14 feet long. I think my garage is 22 feet long--it's tight but doable. People visit my shop and wonder how I move around. I've been doing it for so long I move around quite easily and quickly. The trick is designing the wing jig to allow opening the door, which I try to avoid as much as possible. The jig is attached to the rafters and the floor (glued in place with Bondo). The jig at the door end has a cross piece on the bottom to provide lateral stability. There is a removable section (piece of angle iron) between the main part of the jig and the part attached to the rafter. The removable piece is clamped to the jig and top piece. When the door needs to be opened, the clamps are taken off and this piece removed. After closing the door the piece and clamps are replaced. When the piece is removed, the jig is sufficiently sturdy to hold the wing in place, but is not sturdy enough for building on. The jig must be attached to the ceiling to be sturdy enough to push against and do all of those things required for building. Russ Erb #164, Edwards CA +++ #6047 From: "Melvin Kinikin" Subject: Wing spar stiffeners I have a question on the spar stiffeners. Do you attach the stiffeners to the spar seprate, or do you attach them when you rivet the nose and center ribs to the spar? One other question. Where do you purchase the rod ends that is specified in the plans for the flap and aileron hinge? Thanks. mk +++ #6050 From: Russ and Penny Erb Subject: RE: Wing spar stiffeners The archives on the Bearhawk CD has extensive discussions of the rod end bearing issue. To summarize, you can get them from Spruce and other sources. Wherever you get them, get ready to shell out the big bucks. It's a pretty important part, so don't skimp. I got mine at Sun N' Fun out of a bin that The Bob pointed at and said that's what I needed. As it turns out, they weren't exactly the same, and I had to do several modifications to make them work. From an answer I gave previously to another builder: > The way I did it was straight forward and didn't require undue > precision. > > 1. For the angles that attach ribs to spars: pre-drill the > holes for rib attachment in the angles. This will be on one > side of the angle only. It doesn't matter which side, just turn > it later as required. Do not pre-drill the holes for the spar > attachment in this angle. I made jigs so that I could drill the > angles quickly without constantly measuring--slap it in and > drill. > > 2. On the spars: Drill all of the holes through the stiffener > and cap strips on the spar. These don't have to be perfectly > perpendicular because the angles will be match drilled. After > the spar has been assembled, clamp the angle into place > (clamping the side with no holes to the spar--the pre-drilled > holes are for the rib attachment), and drill through the > existing hole in the spar into the angle. If there is to be an > angle on both sides, such as where a nose rib and center rib > meet, do one angle at a time. Drill one, take it off, drill the > other. Much easier than trying to do both at once. You'll > probably want to label the angles since they will now only fit > in one location. > > 3. After the spars are in the jig, position the rib, clamp in > place, then drill the rib through the existing holes in the > attach angle. Note that these will be so close to the spar that > a 90 deg drill probably won't fit. I used a 12" #40 bit flexed > slightly to drill the holes. Note that you'll spend a lot of > time taking ribs off to get them out of the way then putting > them back on. Plan out your drilling sequence, don't just jump > into it anywhere. > > Clear enough? Russ Erb #164, Edwards CA +++ #7293 Date: Tue, 21 Aug 2001 16:26:56 -0000 From: jmellor@ Subject: Cap strips I have been following along with the group for some time now and know there is a huge amount of knowledge and insight here for the asking. I have been looking over my plans(484) and reading through all the postings and it looks like it's my turn to ask a question.It deals with the cap strip and nose rib length relationship. The length of the nose ribs vary with the stack-up of the caps. For "ease" of construction would it not be easier to run the cap strips "full" length ,thereby making the nose ribs the same length? I understand this would be overkill and add extra weight. Would the added thickness of the caps interfere with other strutural parts? I don't pretend to be an aircraft engineer trying to design a new wing, I only want to keep it simple. YES I have read "so you want to be an aircraft designer". Just a thought. What do you guy's think? Newbie plans owner R.Michael Mellor +++ #7302 Date: Tue, 21 Aug 2001 18:57:53 -0400 From: "William & Delinda Johnson" wjohnson@ Subject: RE: Cap strips I made all my ribs the same length - to the spar center line. As I install, I intend to trim a slight amount off the rear part of the nose ribs and front part of the center ribs. No need to keep each rib marked etc. I will post some pictures if I can find the time - working on multiple airplanes keeps a person busy! Bill +++ #7309 Date: Wed, 22 Aug 2001 03:58:55 -0000 From: "doug" metalfab@ Subject: Re: Cap strips > ........ For "ease" of construction would it not be easier to > run the cap strips "full" length ,thereby making the nose ribs > the same length? weight penalty #8, Wallet penalty $105 per wing, if you could even find full 14' lengths of 2024-3 1/8X1-1/4 doug #433 +++ #7344 Date: Wed, 22 Aug 2001 17:34:08 -0700 From: Russ and Penny Erb erbman@ Subject: RE: Cap strips > For "ease" of construction would it not be easier to run the > cap strips "full" length I don't think you'd really make it that much "easier" by doing this. There will be plenty of challenges much tougher than that. For a perceived savings of a few hours of work now, you'll live with the extra weight for many years. That doesn't seem like a good "cost/benefit ratio" to me, but you may not agree. Then again, I'm "Mr 3 Sigma". Several approaches have been suggested. On one end is Bill Johnson's suggestion to cut them all alike and trim on assembly. At the other end was my approach to figure out the length of each rib, custom cut each one, and label it for its position. I didn't think it was that difficult or added that much work, and the end result worked out very well. I wonder what length AviPro will be supplying its ribs at? My recommendation: Build it per plan. In keeping with recent discussions, you are fully authorized to disagree with or ignore my recommendation. I won't be offended in the least. Russ Erb >>> 2mar02 #7686-9153 +++ #8258 From: "Dan Montee" Subject: Re: Offset Spar Caps As I read the plan it calls for the front side 72 1/8" strips to start 30 3/8" from the root end of the 142+" cap strip. The rear 72 1/8" strips start 41 3/4" from the root end. Viewed from the top, the caps would be offset by 11 3/8".......? Dan Montee # 415 +++ #8259 From: bearhwk272@a... Subject: Re: Dan--Offset Spar Caps Yes,the clarified question is as you have now posed it and the answer is that the spar caps are "staggered". The reason for this is that the spar loads are large at the strut attach point requiring more material thickness, hence the total cap thickness of .500 thick. The loads further out from the attach point reduce therefore requiring less material to carry the load. The stagger is performed to provide an more uniform transition of material thickness and a better means of "feathering" out the section change in the spar. If the caps terminated in line the large change in section would create a stress riser at the cap termination, this would not be a good thing. Kevin Bearhawk 272 Yup! The spars are to print. +++ #8362 From: "Dan Montee" Subject: Rivets? Rivets? How Many Rivets? Question for those who have completed their spars: How many rivets connect the attach angles to the main spar? It looks like the spar drawing shows 4, Mikes' pictures show 5, and I think the photos on Russ' CD and the rib drawing show 6. It looks like 6 is the winner but just checking. Does the back side of the main spar behind the nose rib without a center rib get a vertical stiffener? Again from the photos it appears not. On the main spar how many rivets are in the first rib attach angle that attaches to the root end laminate? On the drawing it looks like 4 and I can't pick up anything in the photos. Thanks in advance everyone. I know this first time builder asks some very basic questions. Sorry about that.. Dan Montee # 415 +++ #8363 From: pfflyerz@c... Subject: Re: Rivets? Rivets? How Many Rivets? > Does the back side of the main spar behind the nose rib > without a center rib get a vertical stiffener? Again from the > photos it appears not. This is the only question I can for certain remember the answer to. Put stiffener bars on both sides of the spar at all nose rib locations. Same thing goes for the rear spar. Pat Fagan #232 Pearblossom CA +++ #8364 From: bearhwk272@a Subject: Re: Spar rivets and such. > Answers from a completed their spar: > How many rivets connect the attach angles to the main spar? > It looks like the spar drawing shows 4, Mikes' pictures show > 5, and I think the photos on Russ' CD and the rib drawing show > 6. It looks like 6 is the winner but just checking. Mine have 7 on about 1 in ctrs, spar cap to spar cap. > Does the back side of the main spar behind the nose rib > without a center rib get a vertical stiffener? Again from the > photos it appears not. Main spar has vertical stiffener at every nose rib location on both sides of the spar, when between spar caps. Rear spar has stiffiners at the center rib locations, both side of the spar. > On the main spar how many rivets are in the first rib attach > angle that attaches to the root end laminate? On the drawing > it looks like 4 and I can't pick up anything in the photos. I have 5 at the root plate. Dan, I had some of the same quandries, resolved it down to some mini layouts of the various joints and made spacing that would allow some common tooling and such. Another note is rivet sizes, walk thru them carefully. I thought that the plans indicated one thing, but the photo book clearly showed 1/8 in clecoes ( Copper Color) in a few areas where I assumed 3/32. ( Silver Color ) Kevin #272 +++ #8370 From: Russ and Penny Erb Subject: RE: Rivets? Rivets? How Many Rivets? Been gone a couple of days. Let's see if I can resurrect some memories here... > How many rivets connect the attach angles to the main spar? There is a discrepancy between drawing 3 and 6. I went with drawing 6 because it matched Mike's pictures. The rivet on the centerline (-4) holds the vertical stiffeners in place. Use a countersunk rivet and drive the rivet into a countersink. This will leave it flush on both sides. You may need to shave the head a bit. This rivet does not pass through the attach angles. It merely holds the stiffeners in place while you assemble the rest. 4 rivets (-4) go through the attach angles, stiffeners, and spar web. 2 rivets (-5) (1 at top, 1 at bottom) go through the attach angles, cap strips, and spar web. Clear enough? Go back and study the CD some more. There are pictures that will show it if you know what you are looking for, which you should now since I just told you... > Does the back side of the main spar behind the nose rib > without a center rib get a vertical stiffener? Again from the > photos it appears not. As Pat said, each nose rib station has a stiffener on both sides of the spar web. These are not just fillers--they serve the important purpose of breaking the shear web up into many smaller shear panels, which greatly increases the strength in buckling. On the rear spars, there are stiffeners on both sides of the spar web every third lightening hole. > On the main spar how many rivets are in the first rib attach > angle that attaches to the root end laminate? On the drawing > it looks like 4 and I can't pick up anything in the photos. Studying the photos on the CD again, there is a -5 rivet through each capstrip (2) and three -4 rivets through the laminate. On drawing 3 the center rivet cross is drawn differently than the other two -4 rivets. If you still have questions, you know where to find us... Russ Erb +++ #8380 From: "Montee, Dan L." Subject: 1/4 X 1/2 Aluminum Bar Stock I'm not having much luck locating the 1/4 X 1/2 6061 T6 for the verticals on the main spar. Is there another option like doubling up the 1/8 or is this something we whittle out of plate stock? Thanks guys, Dan Montee # 415 +++ #8382 From: "Del Rawlins" Subject: Re: 1/4 X 1/2 Aluminum Bar Stock > I'm not having much luck locating the 1/4 X 1/2 6061 T6 These people appear to have it: http://www.onlinemetals.com/ Del Rawlins +++ #8383 From: "rodsmith52" Subject: Re: 1/4 X 1/2 Aluminum Bar Stock > I'm not having much luck locating the 1/4 X 1/2 6061 T6 Wicks carries this making it one stop shopping for all the spar reinforcing materials. Rod Smith #246 +++ #8387 From: "Montee, Dan L." Subject: RE: 1/4 X 1/2 Aluminum Bar Stock > http://www.onlinemetals.com/" Thanks Del, they indeed did have it in stock. I tryed Wicks first since they stock the BH package. No luck. I went to Airparts Inc. No luck. That's when I thought I'd check with you all before I chased my tail any further. I'll keep onlinemetals in my favorites. Great site. Easy to use. Thanks again everyone, Dan Montee # 415 +++ #8390 From: Russ and Penny Erb Subject: RE: 1/4 X 1/2 Aluminum Bar Stock I know you guys resolved this already, but just to throw in one other option: I was able to get mine through Aircraft Spruce on a special order. Since it was a special order, I had to buy the whole length, which I think was 12 feet. Russ Erb +++ #8470 From: "bearhawk0312" Subject: Cutting spar blanks I am looking for suggestions on how to cut spar blanks without a shear and with minimal distortion. Is it possible with a good pair of 12" snips or should I look to borrow a shear? Thanks, #312 Doug +++ #8471 From: Budd Davisson Subject: Re: Cutting spar blanks > I am looking for suggestions on how to cut spar blanks Screw a cheap extruded aluminum angle to the edge of your work bench. Tape the sheet aluminum for protection and clamp a piece of plywood over it and use a tip bearing-piloted router. 3/8" works great. It'll take three times as long to set it up, as to cut it and the edge is perfectly straight (or as straight as your guide) and distortion free. Incidentally, it's not critical that the edges be perfectly straight, but it helps. Bending it is going to be your next big challenge. bd +++ #8472 From: "lbhensley" Subject: Re: Cutting spar blanks I have used a bandsaw with a fence. I used a 4tpi raker blade at a fairly high speed. The cut was clean with no distortion. I used this method to cut out all of my templates for layout on the 4130 wing parts. Make a sample cut to satisfy your own quality level. Once you have made the cut use a second cut flat bastard file and 'draw' the file down the sawcut edge with the file 90 degrees to the length of the spar. Try this first and see of this will fill the bill for you. Please let me know how this works for you. Take your time and good luck. +++ #8473 From: "teyeomans" Subject: Re: Cutting spar blanks When You find the person with the 8-10 ft brake to bend the chanels most likely they will have a shear that will handle the job.... Saves a lot of time doing the setup and manual work.. Tom Yeomans +++ #8474 From: Russ and Penny Erb Subject: RE: Cutting spar blanks At the risk of being accused of posting a "me too" message, I just want to verify that what budd suggests works and works well. It's essentially a description of how I cut my spar blanks. Russ Erb +++ #8475 From: Budd Davisson Subject: Re: Cutting spar blanks Just to clarify: the router bit doesn't have to be anything special. Get a Formica edging bit from Home Depot. A 3/8 with 1/4 shaft carbide one costs fifteen bucks. Two flute works best. A similar set up with a plywood form work great for cutting the rib blanks. You can stack them up and do a number at a time. bd +++ #8486 From: Ken Beanlands Subject: Re: [Bearhawk] Cutting spar blanks This is also a good way to cut out your instrument panel. Once you are satisfied with the layout in plywood, then use your router to trace it onto the good stuff. Ken Beanlands B.Eng (Aerospace) +++ #8732 From: Bob Romanko Subject: Spar Formblock? A thought hit me on the way to work at 0430 today.... Why are folks even considering using up a brake to form spar webs? I may be missing something here, but why on God's green earth couldn't we just rip an 8 foot piece of MDF and make a form block out of it? Put pins through pilot holes drilled where the lightening holes go, slap another piece of MDF on the back, clamp the whole mess togther, and just bend the lip over like you did with all those ribs. Heck, after bending that many ribs I'm having a hard time figuring out why someone wouldn't have enough skill to hand-form a spar web. Seems to me the form block would take about a whopping 30 minutes to make, and I'd venture that folks have a lot more time than that spent on hunting down and setting up an 8 foot brake. Okay. I'm missing something obvious, right? Planter "Grow it, Build it, Fly it!" +++ #8733 From: Budd Davisson Subject: Re: Spar Formblock? It'l work, but you may have to glue a 2 x 4 on edge the full length to keep it from flexing. Go for it! duck bill pliers will take care of any waves. bd +++ #8734 From: "Chris Vuxton" Subject: Spar Formblock? You can get the type of duckbill pliers that home siding companies use at Home Depot. Less that $20 and for about $15 more you can get two more sets of jaw inserts. One is set 12" long. Chris +++ #8735 From: Russ and Penny Erb Subject: RE: Spar Formblock? The only issue I see is that bending the flange piecemeal will stretch the edge, resulting in waves. Then again, coming off the brake I used the edges were not perfectly straight. Everything seems to take some adjustment. I think the duckbill pliers that budd referred to are what the Avery catalog calls a hand seamer, as opposed to the really long needle-nosed pliers or the offset aviation snips, which I have also seen called by that name. I would say if you have access to a brake, then use it. Otherwise what P-Bob describes would work, but it will take more effort. Try to bring the flange down as evenly as possible to avoid stretching. I have used a similar method on many of the steel pieces, especially the thicker ones. Russ Erb +++ #8736 From: Bob Romanko Subject: RE: Spar Formblock? The key is to support, secure, and clamp the h-e-doublehockeysticks out of it. If you took the remaining MDF and laminated the block and the backing block to about three layers or so thick, put in many pins, then clamped the whole mess down onto a solid workbench at 12" intervals, I'd venture that the stretch would be minimal at best. As dad used to say, "We're not building a watch!" I'd like to see a Bearhawk Poll of the builders who have built their spars already and actually bent their webs on the FIRST try accurately using a brake. Planter Bob +++ #8737 From: Brian Cox Subject: RE: Spar Formblock? I had a thought along these lines while driving to work this week also. How about clamping the web between two sheets of MDF. Then use duckbill pliers to work down and back and slowly form the bend. Kind of like using the Bobstick to make hole flanges. Work a little at a time, just bending part way on each pass. Brian Cox, #478 +++ #8738 From: Bob Romanko Subject: RE: Spar Formblock? Duckbills? Maybe, but I'm not so sure you'd want to bend it so locally with duckbills. I'm planning on using the same hammer I used for the ribs, just being more particular about where/how I pound. For the finished flange I'm thinking of smoothing the whole flange out using a rounded off piece of ash. I'm not too concerned about stretch. The fewer operations the better. That's probably the best rule of thumb for reducing stretch. Remember, anytime you bend metal you stretch metal, whether you bend it with a hammer or bend it with a brake. The trick in either method is to keep the stresses evenly distributed throughout the piece. Distributing the stresses better is what I hope to accomplish with the ash. I'm about two months away from this process. Hopefully I'll be in Homer by then and able to start building the spars. My ribs are all done. Planter Bob +++ #8742 From: "Kent White" Subject: RE: Spar Formblock? Stretch/Shrink? Spar Formblock?Stretching and shrinking both occur at the point of bend, as compression at the inside radius of the metal occurs right alongside the tension at the outside radius. It may not be much, but with the tightest radius bends, it does occur. To the degree that both compression and tension balance each other, the bend will be straight along the length. Other factors also contribute to achieving a straight or curved bend, such as the die condition and alignment and strength of the machine (flex). It is possible to shrink 2024 T3 with hand hammers, as it is also obviously possible to stretch. Those of you making the ribs might have seen some compression of the wrinkles, at some ideal spot. Using the form blocks may be the ticket, If... The clamping and the forms are groinked down tight and solid... The legs are worked consistently and gradually, avoiding any sudden departure of contour. And if the striking surface is contoured to avoid marks or sudden departures when striking the metal. Flow forming may have the advantage, as many sudden whacks are better than fewer big sluggish ones, and the tooling (whacker) is more easily adjusted for the metal contour and thickness. Thanks to kind contributions by Kevin Deutscher, Benton Holzwarth, and Russ Erb-onomic the wingrib article is due to appear in Sp Av in a few days. There is mention of the flow forming method in this article, and the tooling and images of the work possible is now up on our website. Kent White www.tinmantech.com +++ #8744 From: "Bruce A. Frank" Subject: RE: Spar Formblock? I think you guys are all desperate for something to do! Like making the wings take one and a half years instead of "just" one year. Keeping that bent-over flange straight and smooth over such distances is more of a chore than one might think, particularly when many here have voiced concern over the final dimensions varying a few thousandths from spec. Pounding it over is asking for a lot of "fixing" afterwards. Better to take hardware store piano hinge and back up the MDF on both sides of the hinge with 2 X 4 lumber. Still, finding a break and even paying someone to form the pieces may be less expensive. If the break-man can't hold the ? thickness of the metal in the final dimension and you agonize over that, wait until you have gone through your total aluminum inventory and are still 1/8" off with your MDF brake machine. Don't get me wrong, I think doing it yourself from a tool you built yourself is what it is all about, but be aware that the end result is going to be less than perfect and the getting it "perfect" is very time consuming (if possible at all). If you realize that "perfect" is not necessary then this forming block method will provide great satisfaction. Bruce A. Frank +++ #8970 From: "Forrest Ferdon" Subject: Spar Splice plates for Barrows Wing Struts Does anyone know if the spar splice plates are different if using Barrow's wing struts? I am gettine ready to bend and build up my spars and I don't want to scrap anything. I just ordered Erbman's CD via PayPal, so I don't know if it is referenced there. Any help would be appreciated. I intend on using the Barrows struts, but don't want to purchase them or the drawings until I am ready to hang my wings. What do you guys think? Forrest Ferdon +++ #8971 From: John Dougherty Subject: Re: Spar Splice plates for Barrows Wing Struts If you follow the plans, you will have no problems with the splice plates. The struts will fit. The new plans for strut fittings do not affect the wing spar splice.......John >>> 4sep02 #9154-11297 +++ #10310 From: "Javier Garza" Subject: FAT RIBS As i do some test bends for the main spar the plans show a web width of 7.59 which is about 7 9/16, for the spar to go on the outside of my rib`s flange it will have to be almost 7 11/16. my ribs are biger because the form block was cut along the line of drawing #7, it shows to be exact but it looks like the ribs grow a little due to the bending around the form block. If i continue as is my wing will be a full 1/8 wider afther the skin goes on, any coments will be appreciated. +++ #10311 From: Russ and Penny Erb Subject: RE: FAT RIBS Ahh, the fat rib question arises from the ashes... From our previous discussions, we've determined that the 7.59" dimension on the plans does not match the mother form block that the Bob drew your #7 around. Everybody's spar, including mine, is slightly larger than the shown dimension. Bend the spar to match your ribs and don't fret about it. The air molecules won't mind and won't even notice the difference. +++ #10316 From: "Schutt, Barry C" Subject: RE: FAT RIBS I was accused of building my airplane so heavy that it would never get off the ground---for the same reason you have just described. I think the problem is that---when making your form block, you should have sanded the line away---I also sanded just to the line, made all my ribs and then addressed the spar size only to find out the ribs were to tall.----not a problem though! You can either remake your ribs if you have only a couple of them done or you can make the spars a little taller (both/all front, rear, aileron, flap)----is what I did, and this won't be a problem to it flying either----this is such a small change that it won't make any difference at all. Barry Schutt +++ #10329 From: Russ and Penny Erb Subject: RE: FAT RIBS > Has the group discussed calculating setback and bend allowance in > order to get the spar to match the ribs more easily yet? There's a good discussion of that in the yellow Bingelis book. +++ #10336 From: "Tom Yeomans" "teyeomans" Subject: Re: FAT RIBS > Has the group discussed calculating setback and bend allowance in > order to get the spar to match the ribs more easily yet? If you follow the information Bob has in one of the early news letter the spars will bend very accuratly. He did a great job of getting the point over. I'm sure it will work for you also. +++ #10345 From: Bob Romanko - Planter Bob Subject: Bend Allowance (Was: FAT RIBS) > Okay. I already know how to bend alclad; I was just wondering if > everyone else knew... Afraid of Bend Allowance? Naahhh...we're not afraid to bring up ANYTHING! (grin) Bend allowance (BA) is how much sheet metal it takes to make a bend over a given inside radius. So it's really the amount of metal needed from the start of the bend to the end of the bend. Picture a sheet that's .032" thick. If you bend it 90 degrees the inside of the bend has compression. It has to, because there's less material on the inside of the bend. The outside of the bend has tension, because the outside is a larger radius. Where the bend starts and stops is called the bend lines, and those will differ because of thickness between the inside and outside bends. If you imagine a centerline in the material, that's called the neutral axis. Actually, in a perfect world, it would be the center. I was taught that it's closer to 45%, but why split hairs? The neutral axis, wherever the FAA says it is, retains dimensional stability throughout the bending operation because it has neither compression or tension forces acting on it. Picture your spar. It's .032" thick. Let's put a nice 1/8" (.125) radius in that puppy to keep it simple. To make it even more simple, let's cut the spar in half so it's easier to crunch the leg and the flange. The web of the spar would be the leg, and the flange would be the...well...errr...the FLANGE! Let's say our ribs are 7.6" to keep it easy. I'm gonna chop that spar down the middle and go with 3.8" plus a .5" flange. We all know that you just can't add 'em up and get 4.3", right? No, that would be TOO EASY! We need to figure out bend allowance first: What's the radius of the neutral axis? Well, if we're shooting for .125 radius it would be that plus 1/2 the stock thickness. In this case .125 + .016 which equals .141". So, the radius of the neutral axis is .141". We have a 90 degree bend, right? Okay, so that's 1/4th of a circle. Now what we need to do is to find the circumference of a circle having a radius of .141", and then divide by 4. The circumference of a circle is 2piR, we take 2 x 3.1416 x .141 and end up with .88593". So, .88593" is the circumference of a circle with a radius of .141". Still, that's not where we want to be, because our bend is only 1/4th of a circle, 90 degrees. Now all we do is divide .88593" by 4 and TADA (drumroll please) we get a bend allowance of .2214825". Now what to do? Well, we want to know the lengths of the unbent portions. To do this, we only need to subtract the stock thickness and the inside radius from the leg and the flange. Our flange is .5", so .5 - (.032 + .125) = .343", which is the unbent portion of the flange. If the leg length is 3.8" we'll do the same crunchin' for that: 3.8 - (.032 + .125) = 3.643". Now, one more step and we're almost home. Add up the flange, the leg, and the BA and we've got 1/2 a spar width finished. 3.643 (leg) + .343 (flange) + .2214825 (BA) = 4.2074825". We're STILL not home yet...one more thing to do, right? Yup! Take that sucker times 2 and you get 8.414965. So, with this spar web width with my made up numbers, I think all this is right. My math could be off, but ya'll should get the gist of how to crunch this sort of thing. I'm runnin' on about four hours sleep, and ready to curl up with the Good Book before giving Peaches on more pat on the head and dozin' off. Ya'll have a good one, and I'll be giving you an Alaska trip update here in a week or so. +++ #10346 From: Drew Schumann Subject: Bending aluminum the wrong way. Anyone besides me a little scared of bending aluminum along the grain on those big old nasty spars? I was a little nervous about the full-size wing ribs, but put the proper radius on the form block, and they didn't show any outward sign of cracking or weakening.....Yet. Bein's the spar pieces are 8 ft long and the metal is 4 ft wide, don't you have to bend the aluminum along the grain, like it prohibits doing in all the texts I've read so far? Maybe there's a technique here I'm not understanding. +++ #10350 From: Russ and Penny Erb Subject: RE: Bending aluminum the wrong way. Don't fret, Drew. Bending with/across the grain is only an issue when using a minimum bend radius. Bend it too sharp and it cracks. If you make a bend with no cracks, you're fine. The newsletters call for a 1/16" bend radius, which I think is too sharp for the spars. I used a 1/8 bend radius and they came out just fine. The *preferred* direction to bend is across the grain, but you can't always do that. There is no "prohibition" against bends with the grain, only a caution. Don't confuse *radius* with *diameter*. A 1/8" RADIUS is what you would get wrapping a piece of aluminum around a 1/4" drill bit. Go in piece and bend your spars. +++ #10351 From: Russ and Penny Erb Subject: RE: Spar Construction > Now, if true, why could you not bend the flanges separately from the > web in 48" sections on a standard sized brake and rivet them in place > between the caps and web during assembly? Disadvantages: 1. Higher parts count 2. More weight 3. More work to get everything aligned 4. Other reasons I just deleted because I figured out what you were saying and they weren't applicable anymore Assuming you can live with that, I'll throw it over to those with more background in structures to chew on it. It's actually an intriguing idea for attacking the problems facing a one-off builder. In a production environment, you'd just buy the proper tooling. +++ #10354 From: Budd Davisson Subject: Re: Spar Construction > ...why could you not bend the flanges separately from the web in 48" > sections on a standard sized brake and rivet them in place between the > caps and web during assembly? There's nothing really wrong with the logic of your proposed approach, although it's hardly the way we like to see structure put together. The fewer the joints, the better it works. To make your idea work, it would require a couple of things to make it work safely: -an analysis of the shear and bending loads at each station where you propose a joint -an analysis of the reqired thickness of the splice plates front and rear for each joint. -the analysis would show how many rivets would be needed at each plate -it's really bad technique to have that many open splices running under the spar cap strips where they can work, so some considerationwould have to be given to running the splice plates under the spar caps so you'd need full length spacers to make up the difference. -the bent flange should also be doubled, which would be most easily done with bent splice plates that nestle inside the spars and run from edge to edge. You're putting joints right where you don't want them (mid-bay) and there would be so many splice plates and spacers that it would be a night mare spacing the spar caps out, modifying the rib spacers, coming up with correct rib lengths, etc. There are about a dozenthings I've forgotten or over looked here, but the bottom line is that in the long run you'd be better off spending a little extra time finding someone with a break and shear and educating them, even if it results in some wasted spar material. There are some good reasons you don't see very many spar splices mid-span. There's a rule most of us structural engineers keep in the back of our minds: we are unlikely to run into a structural problem someone else hasn't already run into, so don't re-invent the wheel by coming up with a brilliant new idea thatmay or may not work when there is already a proven idea out there that does work. +++ #10359 From: "Bruce A. Frank" Subject: Re: Spar Construction What Bud points out is absolutely true, but at the chance of also having to don the Nomex I'd like to proffer some alternative wing assembly methods. Back when there was the discussion about getting the flange of the spar bent exactly so that the finished width was dead on spec brought this thought to mind. Why not make the flanges separate pieces of formed angle that is riveted to the web of the beam that is created. Height could easily be set perfectly and then the rivet holes drilled. Only a few inch wide piece of aluminum would have to be worked with no loss of large quantities if there were a screw up. In fact, as I see it there would be very little chance of having to discard material because the adjustments are made at the rivet hole drilling point. This would also eliminate having to "train" the break operator to hit your marks so just about anyone with an 8 foot brake could be recruited to make that flange. And on the chance of sounding blasphemous there may even be formed angle available on the market, such what the BD-4 people get produced in quantity with which they assemble their craft. ( and are obtainable in pieces as long as 20 ft) Now let me put my foot farther into my mouth. Making the formed spar in 4 ft sections and assembling with additional backing plates, spar caps and rivets if laid up in a plywood jig just wouldn't be that complicated. Another method: I have built spars, not for aircraft use, but rated to support cantilevered walkways and balconies for heavy people traffic, by splitting extruded Piper style spars down the middle of the web, separating the pieces to the width needed then riveting in an overlapping web "doubler" that took the spar strength to three times the original design strength.(additional doublers added where higher strength is needed. There are STC'd splice methods for certified spars that do not increase the strength as well. My point here is that there are perfectly acceptable ways to create a built up spar that sacrifice nothing in strength, and little in increased weight, compared to a full length spar. See the very small attached JPG if my words didn't paint a clear enough picture. Adjust the rib attachment flanges to an additional layer added, if needed, to compensate for the web missing between the angles could be straightly forwardly figured. Layers could be overlapped at the web splice points and the flange adjusted rather than adding a rivet plate doubler at the joints. Working with materials available to meet the strengths and rigidity needed, coming up with alternative methods is part of my trade. Maybe that makes it seem too easy to me, but I see most everything as a "build to fit," solution. +++ #10362 From: Bob Romanko Subject: RE: Spar Construction > ...why could you not bend the flanges separately from the web in 48" > sections on a standard sized brake and rivet them in place between the > caps and web during assembly? My thinking is, sure, it can be done, but why? To avoid having to find someone who knows how to drive a brake? I just can't see how the added complexity of analysis, fabrication, assembly, and weight offsets the need to find someone who knows how to bend metal and perhaps the cost of a few scrap 8' long strips of 2024T3. Heck, if you scrap a few strips, no problem. Aluminum, like trees, is a RENEWABLE resource! If you scrap a few pieces no big deal, we'll just plant more! You'll find plenty of things to do with those 8' long strips. Losta plane to build after the spars are bent, don't you agree? For what (little) it's worth, +++ #10369 From: "wrenchspinner1" "Mark Deacon" Subject: Spar construction OK so maybe it was a hot sunny day and I wasn't wearing a hat and the exhaust got to me. But... I wasn't suggesting bending up the spar in 4 pieces. This technique would allow the web to be made in one piece from root to tip eliminating the existing splice at the center/ strut attach point. Just the angles at the top and bottom would be in four separate sections. My ASSumtion is that the angles are there just attach the skin and does not add to the spars load carrying capacity. If so and the angles are along for the ride so to speak, does it matter that they are in 8 pieces? Parts count, without the plans in front of me I figure 10 pieces. The flanges (8) and 1ea under the strut and root plates. Yes it would be harder to assemble, more pieces always are. For me it's just another part of the "measure twice cut/ drill once" sheetmetal assembly sequence. Weight, my estimate is about 2lbs per main spar, less for the aft. I'm no structures guy, just a little old A/P in search of higher knowlege. Don't hesitate to poke holes in the theory as you see fit I'm used to being wrong as I've been married for 11 years. +++ #10372 From: Russ and Penny Erb Subject: RE: Spar construction > This technique would allow the web to be made in one piece from root > to tip eliminating the existing splice at the center/ strut attach > point. You might be able to eliminate the splice on the rear spar, but not on the main spar. That splice plate has a primary job of distributing the load between the spar and the strut, with a secondary job of holding the two shear webs together. +++ #10375 From: "Bruce A. Frank" Subject: Re: Spar construction > My ASSumtion is that the angles are there just attach the skin and > does not add to the spars load carrying capacity. Actually the skin of the wing becomes part of the "flange" of the spar and I think your assumption is reasonable. Still, in my own construction I would like the flanges continuous regardless of the method of splice of the web of the spar......not just because my wings will be fabric covered. +++ #10408 From: "Rimas Miknaitis" Subject: false spars The answer is probably right in front of my face, but I am measuring and cutting out wing ribs and spar webs and I can't find the LENGTH for the false spars between ribs 2 & 5 behind the fuel tanks. I could just use the rib spacing and deduce it from that, but I can't find an exact measurement on the plans for rib spacing either. Any help to point me in the right direction would be appreciated. +++ #10409 From: Russ and Penny Erb Subject: RE: false spars See the spar drawings for rib spacing. +++ #10435 From: Budd Davisson Subject: Re: Spar Construction Using extruded spar caps is always a great idea, but the extrusions have to be either custom made or milled afterwards to make the tops of the extrusions follow the airfoil. It takes a different extrusion for every airfoil and airplane application because the spars are always in different places on different air foil.s The ideal situation is an extrusion which in its raw form has enough top flange width or verticle leg thickness that it could make up for the stacked spar caps. It would then be machined to give the necessary strength where needed. It would also mean a different riveting situation in the skins because of the thickness of the spar cap and different joggles in the rib. These are all good ideas but don't lend themselves easily to the guy building it in his garage with a minimum of tools, which was Bob's original goal. What you're talking about is a complete spar redesign, which isn't out of the question if our production gets big enough to justify custom extrusions, but I don't see that happening. +++ #10444 From: "Bruce A. Frank" Subject: Re: Spar Construction Yes, an extruded piece like the caps of the Piper spar would present difficulty. But rather than a real extrusion for the Bearhawk type, I was thinking more on the lines of a strip of the print specified material pushed through a roller die guide to bend it to the approximate shape that will pull into position with rivet, bucking bar and rivet gun when the skin is installed....Just the same as the present method. Shape is the same as the top and bottom caps out of the same material just riveted to the web rather than bent off of the web. The only change I was really proposing was that the flange of the spar could become a separate riveted on piece which would allow for precise adjustment of the spar height which at the same time would eliminate the chance of lost material due to a mis-bent flange. I am not even saying that this should be a change. I am offering a different way to think about how the spar could be assembled for those who have shown concern over inexact, slightly different than the print, heigth of the spar brought about by a break operator who can't hold the tolerance. +++ #10813 From: "Dan Montee" Subject: Re: False spar > I can't find information on the false spar, in the bear tracks or the > C.D. Is there a false spar to build, or is it the front of the fuel > tank.? Yep, you will find it on drawing #6. I scratched my head for a few hours myself. +++ #10814 From: Russ and Penny Erb Subject: RE: False spar The only "false spar" called out on the plans is the rear wall of the fuel tank bay. The top of the spar is shown on Drawing 2. The end shape is shown on Drawing 6. There is no separate drawing of just the false spar. More info can be found in the April 1996 Bear-Tracks. The false spar shows up in many pictures in the "Wing Assembly" section of the Bearhawk Reference CD. +++ #10962 From: Russ and Penny Erb Subject: RE: just checking > On the rear spar web splice, drawing shows a 032 sheet both sides but > i have not found the detail on riveting the webs , how many and how > far apart? If you're talking about the hexagonal splice plate, there's one on the front and back. I made the rivet pattern just like the little dots on the rear spar drawing (#4). If that doesn't help, ask your question again. >>> 20may03 #11298-18250 +++ #11798 From: Benton Holzwarth Subject: Formblock for Spars I tried making a formblock to bend spars over. Routed an edge into a 8' 2x4, and screwed some steel strap onto it, then radiused it to the 0.1" callout on the plans. Total invested, including eight bar-clamps to hold the metal in place -- about $25. Tried running a first test this evening -- putting a flange on a 2'6" piece of scrap 0.025 Al. I think it did a decent job on the first 80 deg (90 deg less springback) but when I tried to whack the edge over the rest of the way 'freehand', to the slightly closed angle to match the flap rib, I think there was a little stretching, so that over the length there is about a 1/8" rise (bow) towards the flange. I'm guessing flutes on the spar flanges would be a bad thing, so I'll try some more to perfect the technique. Failing that, I'll look again for a brake. Benton +++ #11873 From: Benton Holzwarth Subject: Followup to "Formblock for Spars" Last saturday I posted a quick note on my attempt to bend spars (scraps so far) over a formblock. The earlier, only partially successful test was on a piece of 0.025" Al. I tried again last night on a piece of 0.032" -- what the spars are supposed to made from. It seemed to go better. I was more careful about trying to work it more uniformly, and I think there was less stretching of the flange material as it went over. This thicker scrap was only 16" long, but the bowing due to stretching in the flage area was less than 1/32" I'd guess. Also, the radius I filed into my formblock reinforcement (inlaid steel strap) looks to be about nuts-on -- a 7/32" rod (drill bit) just lays in the corner of the bend. I have one more refinement to make on my formblock, and then will take a whack at a real spar. I'm working on flaps and ailerons first. Benton +++ #11866 From: "abdunbar60012" Subject: Re: Followup to "Formblock for Spars" > Last saturday I posted a quick note on my attempt to bend spars > (scraps so far) over a formblock. why do you want to do this? I drove over to the local heating and a/c contractor, explained what I wanted to do and they were excited to help. They have really big brakes. Archie +++ #11884 From: Benton Holzwarth Subject: Re: Followup to "Formblock for Spars" > why do you want to do this? Well, yes, I could have done it that way, I suppose. But this way - I can work when I want to (typically 8 - 11pm), - Bend them as I need them, rather than having to get everything lined up for one visit, - Learn a little more about what I can do with the metal, - Have a new trick if I ever need a bend longer than the biggest brake I can find. (This technique scales up.), and best of all, - I don't have to admit it to anyone if a screw one up later in the processing. Benton +++ #11886 From: John Thompson Subject: Formblock spars Archie, Not everyone has access to a understanding sheetmetal shop. someone may not bother helping you when you try to explain bend radius, and some will not have anything to do with an "experimental plane" for fear of liability. Some just won't do it. I for one am interested in the results. It will be interesting to discover if he can make it without bowing or not. John +++ #11918 From: Del Rawlins Subject: Spar Riveter I've been designing a fixture for riveting the wing spars in my hydraulic press, and have reached the point where all that is left is to build the thing and test it out. Since I am not able to do either at this time, I thought I would pass the drawing along to the group in order to solicit comments and possible suggestions for improvement. I only know enough about CAD to be slightly dangerous, so bear that in mind while viewing them. They were drawn and converted to DXF in an old version of Autocad LT which hopefully won't cause any viewing problems. The dxf and original dwg files are available on my site at: http://www.rawlinsbrothers.org/rriveter.dwg and http://www.rawlinsbrothers.org/rriveter.dxf The purpose of the whole exercise is to provide a precise means of setting the rivets in the wing spars. I've got nothing against rivet guns, but my thought is that using this fixture will minimize the chance of messing up the spars, either from (mis)driving the rivets or removing the bad ones. It probably wouldn't be worthwhile except I already have a hydraulic press that I built a while ago. The main feature of the riveter is the adjustable depth stop, and I welcome suggestions to simplify and otherwise improve it. -- Del Rawlins [ Followup under $3.1.5 Riveting ] +++ #11938 From: "miknaitis" Subject: spar vertical stiffeners The plans call for 1/2" X 1/4" stiffeners on the main spar where the 1/8" cap strips double up. Anyone know if it is okay to use doubled up 1/8" stiffeners, or does it have to be a solid 1/4 inch? Thanks, Rimas +++ #11943 From: Russ and Penny Erb Subject: RE: spar vertical stiffeners > Anyone know if it is okay to use doubled up 1/8" stiffeners, or does > it have to be a solid 1/4 inch? That should work fine--it is just a spacer and a stiffener on the spar web. Either method should work just as well, although using the 1/4" piece is a lower parts count and less things to align. I was able to get the stiffener stock through Aircraft Spruce on a special order--the only downside is you have to buy the entire 12' piece, but that's close to what you'll need anyway. I bet Wicks can make the same special order. Russ Erb +++ #11952 From: Del Rawlins Subject: Spar alignment I had another thought on keeping the spars aligned while riveting. Since I'm planning to operate my Bearhawk as a seaplane, I'm going to go a little farther with my corrosion control measures than most of you (Erbman excluded) will need to. This will include priming the spar pieces individually, and assembling with a light coat of primer between the parts. Would there be a problem with assembling the spars on edge in a normal fixture like would normally be used riveting them together, using evenly spaced bolts through the rivet holes as per The Bob's recommendation, and then waiting until the primer dries before installing the rivets? This plan assumes that it would be possible to get even clamping force along the length of the spar caps (which may not be easy), but the cured primer should tend to keep the spar straight while riveting. Particularly if the spar was being moved around during the riveting, like if I decide to use my proposed press fixture instead of a gun. -- Del Rawlins +++ #11956 From: Russ and Penny Erb Subject: RE: Spar alignment Del--review your new BHCD. I used "sufficient" #6 machine screws to hold the capstrips in place, and filled the rest of the holes with rivets held in with tape (if required). This holds everything in place as you drive the rivets. My concern with using a drilling block with an index pin to drill the rivet holes would be any error in the distance between the hole and the pin would be magnified along the distance of the spar. With over 130 rivets, a .001 error would be over 1/8" off at the other end. You'd need some way to manage tolerances. However, I think this is overkill. I drilled every stinkin' rivet hole by hand, and it worked just fine. The rivets don't have to be dead-nuts square, just reasonably close. As for the holes for the flap/aileron mounts, those were drilled after assembling the spar and during the assembly process with the flap/ailerons. The spar construction and assembly deserves care and accuracy, but it's not really as sensitive as many of you seem to think. Unfortunately, you won't fully understand that until you're done with the spars. Russ Erb +++ #12018 From: Budd Davisson Subject: Re: For Budd, Spars John, We don't have any plans on getting that far down into the list of components. We offer finished spars and ribs, only. You'd be better off finding a brake locally, or getting one of the guys to do it for you. Just make sure they "over bend" the flanges slightly because you can bring them back and keep the edges straight, but if they are underbent, when you try to force them farther they stretch and get wavey. bd +++ #12207 From: Benton Holzwarth Subject: Formblock Spars update This weekend I cut out blanks for my aileron and flap spars, and bent the first of the flap spars over the form block I'd written about earlier. As a counter to the bowing I thought I'd seen earlier in a short test piece, I arched the formblock about 1/8" away from the direction the flange would be going over, to try to compensate. I think it worked. This first spar isn't going to fool anyone that it was done in a brake, but I think it may be usable when all is said and done. A couple people have tapped me recently to pop by for a look at the project; I'll get a few more opinions. It sure was a lot of work pounding it over. I'm don't know that I'd recommend the technique if there is access to a big brake. Benton +++ #12249 From: bcgh@a...> Subject: (More) Formblock Spars Showed my first flap spar -- bent over a formblock -- to a couple guests last night. (Thanks for coming over guys!) They seemed to agree with my read, that while it might have come out better (smoother flange, straighter on the bend line) done with a brake, what I have is 'airworthy'. (That or they were just being nice.) I'll continue to show the work to anyone who'll look, and will forge ahead with bending the rest. When I get a little time, I'll put up some pictures on my webspace, and let you all know. Benton +++ #12522 From: Don Rennie Subject: Spars I got my break work done at Calgary aluminum, they made my Front and Rear wing spars, False spar, Flap spar, Aileron spar, Wing skin stiffeners, and Flap and Aileron trailing edges. This company really did a great job, the ribs fit like a glove. This company makes aluminum tool boxes and armor for 1/2 tons and other trucks. They have all the radiuses for the break and even rubber edges. If there is a business in your area like this, they may be able to do your break work. I cut and labeled all my pieces, I also photo copied from the plans the related info. They carefully made all my pieces. It cost me $300 canadian (that's .50cts. USD.) But they did a great job and I think it was well worth it. These people also made some landing gear parts for another one of our club members. I worked a lot out of town this summer and fall, so the work on my Bearhawk stalled. I'm so glad to be back at it, and also my tail dragger lessons. Hope this info helps some one. Don & Bev Rennie +++ #12598 From: Don Rennie Subject: Fat ribs. Some time ago "FAT" Ribs were discussed , and it was said to make sure the spar size was increased to accommodate the larger ribs.I did thank you. Now when installing the spar ends , web splice and cap strips. They are a little ways away from the side of the spar. It looks like they are a ways away on the plans but I'm not sure. I got my wing photo log today and I thought it would clear it up but I'm still not sure. HELP. Don & Bev Rennie +++ #12599 From: Russ and Penny Erb Subject: RE: Fat ribs. Here's the answer to what I think you asked: Adjust the position of the flanges on the spar web (the .032 piece) as required to match your ribs. The position of everything else (cap strips, splice plates, attach angles, etc) relative to the spar center line should remain as shown on the plans. Russ Erb +++ #13190 From: "Dan Montee" Subject: Rear spar Questions For those of you that have finished your spars, On the rear spar, Splice: Are the rivets -3 or -4? Verticals: Are verticals attached with 2 rivets or 3 rivets with the center rivet counter sunk ala the main spar? Thanks, Dan Montee # 415 +++ #13197 From: Russ and Penny Erb Subject: RE: Rear spar Questions I used -4 rivets in the rear spar splice, based on the note near the bottom of Drawing 4 stating "unless otherwise noted all rivets MS20470-4AD". Per Mike's picture book, my verticals have 3 rivets--a double countersunk rivet in the center to hold the stiffener in place while the angle brackets are attached through the remaining 2 holes plus the rivets in the capstrips. Russ Erb +++ #13937 From: "Greco, Bob" Subject: RE: Cutting .125 capstrips > Instead of running around looking for a very large shear why not use > a router? I used a table saw on the .125 capstrips when I built a MMII. Worked great! Just had to make certain tht the aluminum was protected so it was not scratched as it slid across the table. Allow an extra .016 to .032 on each side for cleanup so the tooth marks can be removed. Use a plywood or other fine tooth blade. WEAR SAFETY GLASSES OR A FULL FACE SHIELD (PREFERED). It does throw chips!!!! +++ #13954 From: "gmgdls" Subject: Re: Cutting .125 capstrips > Instead of running around looking for a very large shear why not use > a router? It's amazing the shear number of aircraft sheet metal and extursion parts that are manufactured by the "hand rout" method, the process of hand rout is old but very cost effective and time efficent, granted with some operations there is fixturing and router bushings with "set- back" used - but the concept is still sound and with some fore thought there is no reason hand routing could not be utilized by the homebuilder. A tremendous amount of hand routing is accomplished with a 1/4" die grinder and 1/4" dia. multi-flute high helix tooling. After working in the Aerospace fabrication and manufacturing arena I was shocked at the large tolerances allowed and the amount of variation accepted. We seem to be lead down the path of perfection when dealing with aircraft, Obviously don't scrimp on safety but heck in flange width and for the most part doubler web width a 1/32"- 1/16" is nornal tolerancing. Michael Corrigan +++ #14006 From: Russ and Penny Erb Subject: RE: Cutting .125 capstrips The beauty of shearing (if you can find a 12' shear) is zero material wasted. One 4x12 sheet of .125 2024-T3 will provide capstrips and enough leftovers to make all of the .125 aluminum pieces for two (2) Bearhawks at half the cost to each builder as buying the strips as extrusions. It's Bob approved. You can legitimately call #232 and #164 sister airplanes, as they share the exact same main spar capstrip DNA. Pat came up with the idea and convinced me--our main spar capstrips were sheared from the same sheet. The only downside to this method is trying to find another builder ready to buy capstrips at the same time you are. Of course, you could do it and sell them off later. Russ Erb +++ #14024 From: "Montee, Dan L." Subject: Cap strips I haven't kept up with the whole thread on this issue lately so if this a repeat I apologize. I followed the lead of the Erbman and shared the material with another BH'er. That was before Wicks started carrying the correct size strips. I think I would buy the strips before I tried to whack 'em out on table saw or with a router. Since my spars are all dressed up with no place to go (all done, waiting for the season to change so I can get outside to prep and paint) I am considering making the front cap strip mods Bob talks about in the recent B-tracks. If I do, I'll buy the new cap strip material from Wicks. . Dan Montee +++ #14064 From: bcgh@a... Subject: re: Cap Strips > That was before Wicks started carrying the correct size strips. I > think I would buy the strips before I tried to whack 'em out on > table saw or with a router. I may have screwed up the math, but I calculated that even with the waste going into a 3/8" router kerf, Wicks was charging about the price of a full sheet of 0.125 Al, and delivering about 1/4 sheet. I'll noodle the numbers again before I run out and buy, but I'm figuring I'll try to cut my own, and perhaps offer a set or two on the 'open market.' Benton +++ #14103 From: pfflyerz@c... Subject: Re: Cutting .125 capstrips > Do the sheet metal fabrication shops often have 12' shears? If I > might ask, what did you and Pat pay to have the shearing done 3 or 4 > yrs ago? This was not a fabrication shop, but rather a dealer in metals. They had all sorts of equipment for cutting metal because that was their business. I don't recall what the cost was, but at the time it seemed very reasonable. The one caveat, they were not real aware of the potential for scratching the metal while shearing. After shearing a strip, they pushed it out of the way with the remaining sheet and somewhere in all that movement we got a number of scratches we had to burnish out. If at all possible, monitor the work and check out the first strip before proceeding with the others. Pat Fagan +++ #14159 From: Russ and Penny Erb Subject: RE: Cutting .125 capstrips > The beauty of shearing (if you can find a 12' shear) is zero > material wasted. Flipping back through the archives, the shearing charge was $44 in 1997. Russ Erb +++ #15792 From: "Andrew Rekow" Subject: Spar Cap Material I'm at the point where I need to buy materials to build my spars. In the drawing for the main spar Herr Bob specifies 2024-T3/T4. Does this mean -T3 is interchangeable with -T4? Also, I had planned on ordering from Wick's and having a friend pick it up for me who's going to be in St. Louis anyway. I know I'm opening up a huge can of worms here but... Are there better places to get aluminum? What (approximately) would be the truck freight charges to get it from there to Iowa? +++ #15793 From: lisankejm@g... Subject: RE: Spar Cap Material The freight was about $35 for all the spar caps and the trailing edge material from Wicks to Ocala, Florida several years ago(two long cardboard tubes). That included picking it up at the freight terminal about 40 miles away from where I live. If they would have delivered it to my door, I understand it would have been over $100. +++ #15801 From: "Lee H. Erb" Subject: Spar Cap Material > Does this mean -T3 is interchangeable with -T4? Somebody else may have answered this, but: -T3 is the temper for sheet and -T4 is for plate but can be for thicker sheets. -T4 is not quite as strong. Therefore -T3 can be used for -T4 but I would not use it vice versus. Lee H. Erb +++ #16240 From: Del Rawlins Subject: Re: Longer range Bearhawk? > If your going to put another aux tank outboard of the existing one > the spar caps should be run clear to the tip. Bob has mentioned this > but check with him anyway. Wing tanks are free weight until you > land. Is this recommendation a result of the wing testing, and if not, do you know if Proto II (which has the extra tanks) has this modification? And does this mean both layers of spar caps on both the front and rear of the spar? Essentially, in combination with the recommended mods to the root end of the spar, this would make the main spar one constant thickness section from root to tip. -- Del Rawlins +++ #16242 From: Budd Davisson Subject: Re: Longer range Bearhawk? I knew I shouldn't have made that comment!! This isn't anything we've investigated at all and was just a comment Bob made one night over a hamburger. This has nothing to do with the existing aux tanks because they are part of the design and inside the end of the spar caps. This was talking about putting a second set outboard of the usual aux tank. Either forget I said it or go ask Bob :-) bd +++ #16387 From: Del Rawlins Subject: Re: Digest Number 1191 > Hi guys, if one inadvertantly drilled a rivet hole within a quarter > inch of a rivet hole that is slated to hold a wing center rib, does > it mean the spar cap strips are junk. What size rivet goes in the hole (i.e. front or rear spar?), and is the 1/4" the distance between the hole centers or the hole edges? -- Del Rawlins +++ #16391 From: "Bruce A. Frank" Subject: Re: Digest Number 1191 Drive the rivet and forget about it!!! Other than the fact that you know a hole is out of line, you have impacted nothing else pertaining to strength of the structure of the wing. Bruce A. Frank +++ #16393 From: Russ and Penny Erb Subject: RE: Digest Number 1191 I'm not real sure what you're describing, but my thought would be to fill that hole with a driven rivet and drill the other hole where you need it. I can't imagine that the spar is so closely designed that one rivet hole would make a difference. Filling it up will add some of the strength back. And be more careful next time! DO: Measure twice, cut once DON'T: I cut it twice and it's still too short! Russ Erb +++ #16403 From: "Schutt, Barry C" Subject: RE: Digest Number 1191 The situation you describe isn't a very big problem until you get several in a row like that. Although the rib shears will load that rivet transverse to the cap strip length direction, the main loads are along the length of the cap strip. If the errent rivet is to close to the rib and the rib overlaps the rivet head, you could just touch countersink the errent rivet hole and drive the rivet and shave it flush. This sort of fix is used all the time at the Big B kite factory. Barry(036) +++ #16418 From: sonny cilley Subject: Re: Digest Number 1193 > What size rivet goes in the hole (i.e. front or rear spar?), and is > the 1/4" the distance between the hole centers or the hole edges? -- Hi Del, the hole drilled in the wrong place is for a -5 rivet and the distance is between the hole edges. I had a thought that if I moved the center rib location a 1/4 " away from the dreaded hole that all might be alright. it is at the 11 th center rib location and the hole is in the main spar cap strip. is there any reason a 1/4" move of the rib would hurt anything . I don't see how it would structurally. thanks, Sonny +++ #16626 From: "Mark Conover" Subject: Re: Spar Mods > Can somebody give me the skinny on the spar capstrip mods that were > suggested after the destructive stress tests. ... I've placed the list of modifications here: http://www.conotech.com/bearhawk/public/mods.html Mark Conover +++ #16684 From: "larpnwt" Subject: Main Spar Cap Strip Mod I'm trying to get a bit more info on the main spar mod. After looking over the list of suggested changes (thanks Mark) I have a couple of questions. 1) Could someone with a copy of the Beartracks that covers this tell me how the new and improved, longer, top, front capstrip is terminated at the spar root plate. Is the plate trimmed or left as original or what? 2) Also does an additional 1/8x1/2 spacer extend from the bottom edge of the top capstrip to the bottom edge of the bottom capstrip at the rib locations affected by this? 3) Is the new round rather than oval rear holes in the .032 mid-ribs for builder convenience or for strength and should I remake my oval ribs? Since I'm waiting for the nov.01 to present Btracks is there anything that warrants a heads up that didn't make it onto Erb's v3 cd, Bentons archives, etc. that I should know before I build my main spars? Thanks, Larry +++ #16685 From: Russ and Penny Erb Subject: RE: Main Spar Cap Strip Mod Larry--nothing has been published other than what Mark had on the web. There have not been any drawings released in Bear-Tracks. Mike should be sending out another soon, but I have no idea what is in it. Russ Erb +++ #16756 From: "larpnwt" Subject: A misplaced hole or 2 Well now I've done it! There I was laying out my pre-drilled cap strips on my main spar web and managed to put not just 1 but 2, #40 holes in the wrong place by about 1/4 inch. The cap strips are fine but it looks like the "wrong" holes in the .032 web are going to just overlap the "correct" holes when they're drilled to finished size. These are where the top and bottom #5 rivets that hold the 1/2x1/2 angle onto the cap strips are to be. Feel free to heap loathing and contempt on me. What's a fella to do, scrap the spar web? I don't have the distance between the holes to drop a rivet in like someone suggested to a another builder recently. Would the epoxy filler during final assembly be ok and safe? The safety/reliability of the spar is my only concern. Larry 562 +++ #16758 From: Russ and Penny Erb Subject: RE: A misplaced hole or 2 One option would be to make two angles with a leg longer than 1/2" so that you can use the holes where they are. Of course, that will only work if the holes are displaced away from the rib. If they are on the other side, I'd say drill the holes where they should be and don't worry about it. You could fill the hole with something to prevent corrosion. I was just mentioning to another builder that what doesn't appear in hardly any of the books on any construction method is how to fix mistakes. budd--this may be another venue for exploitation... Russ Erb +++ #17967 From: "bearhawk598" Subject: Spar lightening holes I am looking at the drawing yesterday and for the back spar lightening holes it is quote to 3" but is it with flanging or without or it is because it don't have the flange. 4.75" - .75" - .75" = 3.25" so is it because the flange have only a 1/8" ??? OR the drawing show always the diameter of the hole with the flange??? Daniel" hole boring " Gagnon +++ #17969 From: supermexgarza@a...> Subject: Re: Spar lightening holes No flange on the spars un less you make the hole 2.5 in and flange it 1/4 but it does not call for a flange Javier Garza +++ #17970 From: Russ and Penny Erb Subject: RE: Spar lightening holes I interpreted the drawings as showing the hole size BEFORE flanging in each case. For the rear spar this is a moot question, since none of the spar holes are flanged (main or rear spar). Russ Erb +++ #17973 From: Russ and Penny Erb Subject: RE: Spar lightening holes Don't do that unless you have really small hands! Believe it or not, the primary reason for the holes in the spars is not to reduce weight. It's to allow you to get your hand in to buck rivets. You have to reach through the main spar to buck the leading edge, and you need to reach through the rear spar to buck the last few rivets on the bottom skin. Russ Erb +++ $Id: 2.1.2-Wing-Spar,v 1.14 2003/05/21 14:56:08 bentonh Exp $