Covering the 7BCM wings with the Poly Fiber process

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s35pilot
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Covering the 7BCM wings with the Poly Fiber process

Post by s35pilot »

Well, I'am finally ready to cover wing for the 7BCM, I asked Joe how he would like to have my postings on covering the Champ wings with the Poly Fiber process, he suggested starting a new topic, So here I'am. I will post as much of the process as I can but, as a disclaimer, PLEASE READ THE BOOK!
This will be my second set of wings and by all means, I do not know this process completely. The guy that is showing me and sharing his knowledge, knows this system well, he will keep a good eye on me.

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Here are the wings installed in the rotater, I borrowed these from Bob. I had to make a couple of blocks to bolt the nav light bracket to the rotater.

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Also, you can see a brace I use to stiffen the wing with as I rotate it, I remove it once I have the wing in position and then re-install to rotate again.

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This is the start of the process, Poly Brush. I brushed 2 coats on the leading edges of both wings and then I will start putting on all the anti-chaffing material.
s35pilot
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Re: Covering the 7BCM wings with the Poly Fiber process

Post by s35pilot »

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I started the anti-chafe taping, the PK screws are taller than the rivets used when covering the Scout wings, Bob suggested doing this 3 tape process to soften the screw heads, it seems to work well. I installed the first row just to the side of the screw heads and then installed another tape to cover just to the other side. Then put one down the center.
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It is easier to install the tapes long and trim with razor blade. Don't slice the tape, lay the blade down straight up and pull the tape up.
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Change razor blades regularly as the tape dulls them quickly. As you see you get a nice clean cut.
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After all screw heads, sharp edges are covered with the anti-chaffing tape I coated all tape with 2 coats of poly brush. If you tape and do not put the Ploy Brush on, the tape will eventually come loose and may fall off. I think it will stay put for a couple of hours. The Poly Brush really makes it adhear well.
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Now I'm ready to cover, well, monday I will install the Inter-rib bracing and start covering.
Champ Dreamer
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Re: Covering the 7BCM wings with the Poly Fiber process

Post by Champ Dreamer »

Hey there S35 guy from a D35 guy.

Just finished covering my wings with polyfiber, and I can't say enough nice things about their process. The book is excellent. I too built a wing rotator, and found it beneficial during the rebuilt process, but not while re-covering. I used Adal clamps to grab the tip bow, had to unhook that end to cover. During re-cover, I built a rolling sawhorse for the outboard end and left the inboard end attached to the rotator. I was able to lift the wing tip, roll the sawhorse out of the way with my foot, flip the wing over, then roll the sawhorse back in place with my foot. Not for the weak of heart! Saved having to chase around the airport and find help, however. Not a suggested method for one without excellent balance! Looks like you're off to a great start, wonderful workmanship. If you need any hints (or encouragement) from an absolute novice, let me know.

Best of luck,
Brian Walker
s35pilot
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Re: Covering the 7BCM wings with the Poly Fiber process

Post by s35pilot »

Hi Brian (D35guy), If you are ever out this way(LGB) in your Beech (or in the Champ), stop by and say hi. I have a question, did you use the Martin clip in the aileron trailing edge bay. The original wings had Martin clip in one side and screws in the other, I think someone had opened the fabric for repair at sometime and just closed back up with screws. The holes are right in the corner (very inside corner, I wish I was at the airport, I would take a picture) of the aileron bay trailing edge. I ordered some Martin clip material from AS but, my mentor is not familiar with it (not used on Scouts, they have 2 rows of rivets). Do you use reinforcing tape (it would have to bend 90 degrees) under the Martin clip or just install the clip over the fabric. Bob was going to be out at Flabob today with his Waco (a fly-in today) and see if he could get an answer out there but, if anyone is familiar with my question please, chime in.
jkvincent
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Re: Covering the 7BCM wings with the Poly Fiber process

Post by jkvincent »

Martin clips are not used anymore, you don't need anything there, "things" don't continue to shrink
like in the old days. Talk to Aircraft Tech Support and they'll tell you exactally that. They offer the very best Tech Support
I have ever expierenced anywhere, period! I finished my (PolyFiber) wings about a year ago, ...came out great.
Are you using Blankets or envelopes? If Blankets, wouldn't the PolyTack adhere better to the leading edge if it were clean metal?
I didn't see that process (covering the leading edge with PolyBrush first) anywhere in the manual.
I followed your postings on your Wing rebuild, ...beautiful work!
Jim
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Re: Covering the 7BCM wings with the Poly Fiber process

Post by Champ Dreamer »

I used screws thoughout, never considered the martin clips, look like a pain to me. Also, I've read several posts here and elsewhere of folks wanting to use rivets in lieu of screws. I don't understand why. It took me about 6 or so hours per wing to do all the "screwin". You might save an hour riveting, but the poor bastard who covers those wings next time will be calling you unmentionable names ! Jim, the polyfiber manual specifically lists "priming" the leading edges with polybrush for better fabric adhesion. Additionally, I ran over the new aluminum on my leading edges with a scotchbright pad to improve the polybrush adhesion. The first coat I applied couild be peeled off easily, so I did so, then scarifed the surface as mentioned. The next coat really stuck!

Brian
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Nathan K. Hammond
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Re: Covering the 7BCM wings with the Poly Fiber process

Post by Nathan K. Hammond »

Pre-Coating leading edges, and/or any large surface, is standard procedure and in the manual. Regardless of covering style; blanket or envelope. By pre-coating, you dramatically reduce the chances of pin holes in the spray coats. The PolyTak will chemically melt the PolyBrush, so there's no worry about adhesion strength.

Tim; skip the the martin clips, they play hell on ribs. Pre-coat the aileron bay cove with PolyBrush like you did the leading edges, and that will keep the fabric in place. Normally you don't rely on a glue (because adhesives work in sheer not peel) but since this is a relatively normal pressure/low wind area you don't need a mechanical fastener.

Looking Good Tim!!!!

nkh
7AC-5691
Super 85-12F @ DVK
s35pilot
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Re: Covering the 7BCM wings with the Poly Fiber process

Post by s35pilot »

Hi David,
Nathan's responce to pre-coating the leading edge is my understanding also, you will also see how we wrap the leading edge material, Nathan, scotch pad seems like a good idea but, after seeing how Poly tak sticks, I not too worried but, I think I would scuff them up next time. The Martin clip was intended for the aileron inside edge only, I plan on screwing all the ribs.
Going to start covering today!
MikeB
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Re: Covering the 7BCM wings with the Poly Fiber process

Post by MikeB »

Brian,
Not to high-jack the thread on the nice looking wing project but the problem with using PK screws on new ribs is that they are all predrilled for 1/8 rivets. If I were using all old ribs or even a couple of new ribs, no question I'd use PK screws. I know you can drill a new hole away from the exisiting 1/8 hole but your rib would look like swiss cheese when you're done and especially in the wash area. As I opted for all new ribs ($$$) when I rebuilt my wings I didn't feel I had much choice. Not sure removing them would be too much of a problem as you'd just grab the tail of the rivet with a vise grip and drill the head off. Hopefully, I'll never have to find out. Obviously, the rivets are more expensive than PK screws.

I used Superflite on the three projects I've worked and basically they also use a very thinned glue to stick down the leading edge and help prevent pin holes. I'm not sure I'd use SF again. Even though they use a 'flex agent' in the primer and cover coat, I've run into some cracking especially in the cold climate up here. I've taken the cutouts from the inspection panels and bent them around when it's warm. When I tried it in cold weather the cover coats cracked. Poly-fiber will too to a certain extent but it's not as pronounced. Of course, there is should be no reason to bend the fabric 90 degrees once it's on the plane so maybe it's a moot point.

MikeB
s35pilot
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Re: Covering the 7BCM wings with the Poly Fiber process

Post by s35pilot »

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Started off today with inter-rib bracing, after I strighten all the ribs, I put a small dab of Poly brush on lacing tape to keep the rib from moving ( it's not in the book, I just thought it would help).
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Also, as I wraped the tip bow.
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I covered the inside corners of the aileron bays, I pre-coated the pieces with poly brush (helps keep clean edges on the material when you trim) and then Poly tak them in place.
A pencil works well to push the material into 90 degree corners.
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We dry fit5 the blanket to the top of the wing.
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Nobody snapped a shot of Poly Taking the leading edge, so I thought I would show you what we used to keep the Tak smooth, use a squeegy and start in the center and push the Tak out and down, smoothing all the glue. Doing only 2 bays at a time. When you are doing a inside corner, like the aileron bay was 2 squeegies to keep from pulling the material out of the inside edge.
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Cut out were the spar sticks out of the butt rib, again bush a lite coat of poly brush on all areas to be cut.
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Then pulled back the material and Poly taked the butt rib.
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After finishing the wing root area we moved on and completed the aileron bay rib ends.
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After the Tak dried, brushed on some Poly brush at the back of the leading edge sheet metal to in order to trim the material to the edge of metal (when dried).
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We did finish covering both side of 1 wing but, I'll have to take care of some work business now, I'll finish posting tomorrow.
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The leading edge looks wrinkled but, have not ironed the bottom yet, the bottom blanket comes all the way around to about 2" from the back of the sheet metal on the top, no trimming (factory edge) it will all tighten up nicely.
s35pilot
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Re: Covering the 7BCM wings with the Poly Fiber process

Post by s35pilot »

Just something I wanted to ad, the book mentions starting the covering with the bottom (also says it does not matter) we chose to start on the top, since it is a high wing puts all the seams on top of the wing, not visible on the ground. Don't know how much I will get done today, not feeling well, fighting a cold.
s35pilot
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Re: Covering the 7BCM wings with the Poly Fiber process

Post by s35pilot »

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The tips are a little more challanging, we tak the Poly fiber to the top of the bow, brushed a little Poly brush on the material and then cut to allow the material to wrap completely around the bow.
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Then darted as neccessary.
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Tak the Poly fiber around the bow.
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Smooth out the Tak, I got a good wrap completely around the metal.
Oh, by the way the top is much easier than the bottom because it is fairly flat.
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We shrank the top to 250 degree, starting at the tip and then move to the butt bay, alternating rib bays until we finished in the center. Every one of the small wrinkles came out on the tip at 250.
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Heat forming the bottom material around the tip bow.
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After heat forming we Tak up the material and trimmed, we got a good 1 1/2" lap.
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Here is a shot of the bottom ironed to 350 degrees. It may be hard to see the pencil marks in the rib bays, but I put a line one way when I ironed at 250 and then made an X when I came back at 350, that way I always knew what was ironed.
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One wing covered, not much going to get done until next week getting real busy at work again.
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A friend of mine send the building the spar link to someone he meet and he sent him this plane, pretty cool.
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joea
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Re: Covering the 7BCM wings with the Poly Fiber process

Post by joea »

Any updates on the wings?
s35pilot
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Re: Covering the 7BCM wings with the Poly Fiber process

Post by s35pilot »

Hi Joe,
Got real busy at work and the Holidays, hope to get back to work on them soon, thanks for checking on me.
Tim
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