National Aeronca Association Bulletin Board

Finish up around the wing tank....

I ended up putting the aft screw out of line and the first two ribs so they would catch the tank lid and rib. If I had put the screws in line with the rest, it would have pulled the leading edge down creating a very noticeable "ramp" leading onto the fuel tank.









nkh

Nathan,
(You may already have the answer on this) but......it's necessary to remove the brace that goes from the butt rib to the spar in order to get the Wag Aero tanks to fit in. When I tightened the fabric on my L16 it caused the butt rib to bend in slighty which caused the plywood floor to move the bottom of the second rib over a corresponding distance. Probably doesn't hurt anything but looks like to the practiced eye. If I had it to do over again I'd try putting a temporary angle iron brace on the butt rib to try to prevent the problem while tauntening the fabric.

Most Champs I've looked at on annuals ,etc. have the bent butt rib even with the brace but doesn't bother unless you have the wing tank a they're covered up by the fairings.

(For that whatever it's worth department )

MikeB

MikeB wrote:Nathan,
When I tightened the fabric on my L16 it caused the butt rib to bend in slighty which caused the plywood floor to move the bottom of the second rib over a corresponding distance.

MikeB

I used countersunk screws to attach the tank to the ribs and to attach the plywood floor to the ribs along the bottom. I'm hoping that will stiffen things enough to prevent much movement by the butt and second ribs. Take a look when I bring the airplane to Middletown in 2 years and see if it worked.

I guess anything will help but it's part of a kind of poor design (lack of bracing) and mostly starts with the bending of lower part of the butt rib as far as I can tell. The fabric has a lot of "pull" when it's being tauntened. Kind of like the bending of the outboard aileron bay rib. I finally installed an aluminum angle iron in addition to the wood filler which pretty much took care of the problem.

Mikeb

I took your advice Mike and looked at the root; sure enough it moves about 1/8" towards the tip, even with the blocks pressing against the tank.

I'm reluctant to add the old braces, only because I don't want to screw them into the spar. But, I could rivet a small piece of angle aluminum from one rib to another and triangulate it out. I'll look into that.

Thanks for the heads up.

nkh

After drilling all the holes for the leading edge, I removed the skins and deburred all the holes using a large drill bit. This might sound like extra work, but it helps the skins lay down flat and allows me to remove all the metal shavings from the drilling.

Now the skins are on for good!






After attaching the skins, I took a file to each screw head. These little 4x4 can strip out REALLY easy, and they usually deform the cross-hatch when you screw them in. This results in a little bur sticking up and can snag the fabric and eventually wear through (granted it may take 20 years or more.) It doesn't take much, 4-5 passes with the file; you can actually hear when the bur has been removed. The first couple passes sound like fast clicking buzz (as the ridges and grooves of the file hit the high spots) and by the 4th-5th pass, it's a nice smooth sound. Took about 20 minutes to hit all the leading edge screws.

Maybe you can see the bur...





Now I'm waiting on some aluminum from ACSpruce to finish the tip skin. $30 for 2 sheets of 2'x4' 2024-T3 .016" and $20 to ship it. Figures....

nkh

Are you going with pop rivets to attach the fabric in accordance with SL85? Unsure if you have the heavier .032 ribs but if you do I can send you a copy of approved paperwork.
Mike

Probably so; the ribs are pre-punched with holes too big for the #4 screws. And I really don't want to start drilling more holes in new ribs.

I plan to cover it after all the work is done; but I'll take a copy of your 337 for the files next time you get a chance. No hurry, it'll be a while before I need it.

nkh

The fastener (pop) is a bit less obtrusive than the PK screws but removing several hundred when the wings need covering again could be a real chore.

Send me your address by PM and I'll snail mail a copy to you.

Mike

I removed rivets from a Citabria and it was not a bad chore. Rivets have a big advantage during installation. Use a Harbor Freight air-puller and the job goes fast.

Started working on the tip this evening. Pulled up drawing 7-556 and it show's the last two bays as one piece; mine came apart in two separate pieces, but I think I'll do it like the drawing. Before cutting aluminum, I'll finish make a template out of cardboard so it fits perfect. (Cardboard is cheap)

Didn't get to work on it any this weekend (camping with the boyscouts) and only had a couple hours today. So this is the first try, and I already have a couple of tweaks that need to be done before finished.

I'm headed to Georgia for a couple weeks, so won't get much done on this wing.

Ike the wonder dog keeping everything in check.





And the project from this weekend; 18' to the platform. The kids, cut/limbed the trees and lashed this together in one day, then spent the rest of the weekend shooting potatoes from the platform. All kinds of fun!





nkh

Wishing you made the tip leading edge in 2 pieces yet? David J.

I bought the one piece tips from Wag Aero and finally wound up cutting them apart and made a two piece. Just couldn't make the compound bend. Maybe with some kind of a metal stretcher or english wheel but then metal work never was my strong suit.......not sure what is (????).
MikeB

Haven't touched it since I took the picture; down in Georgia for the week. But I'm guessing I'll be cutting it by the way you guys are talking.

DJ; you and Old Fart jump in Green Hornet this Saturday and come on down to PeachState, I'll buy ya a cup of coffee.

nkh

How about Sunday? Got a full plate Saturday. David J.