Flap and Top Wing Skin

[MarkSchmitz]

I'm getting ready to fit the wings and "re-discovered" a problem I set aside awhile back: My flaps push up against the wing top skins at the outboard ends (where the flaps end and the ailerons begin.) There's a fair amount of friction until the flaps are lowered. The flaps are pushing the wing skins out slightly less than 3/32" past where they rest without tension. I've double-checked my flap spar orientation, etc. and everything seems correct. I've tried tweaking the leading edges of the flaps to no avail. Is this a common issue? Any suggestions for correcting or judging as to whether it needs to be corrected?

Any insight would be greatly appreciated!

Mark
RV-8
Slow Build Wings / QB Fuse

 

[mannanj]

Flap-Top Skin

Looks like you may have to use a bigger hammer (a little more force in "tweaking") the outer flap leading edges. Idealy there should be no force, just slight contact between the two along the entire length of the flap-upper wing skin junction.

 

[GAHco]

Its a trade off, deformity on top, or deformity on the bottom

I'm getting ready to fit the wings and "re-discovered" a problem I set aside awhile back: My flaps push up against the wing top skins at the outboard ends (where the flaps end and the ailerons begin.) There's a fair amount of friction until the flaps are lowered. The flaps are pushing the wing skins out slightly less than 3/32" past where they rest without tension. I've double-checked my flap spar orientation, etc. and everything seems correct. I've tried tweaking the leading edges of the flaps to no avail. Is this a common issue? Any suggestions for correcting or judging as to whether it needs to be corrected?

Any insight would be greatly appreciated!

Mark
RV-8
Slow Build Wings / QB Fuse

The area where the piano hinge is riveted onto the brace and bottom skin can be tilted down gently and make up some of that difference in the area where you need it to come further from your top skin.

The hinge pine line needs to remain in a strait line.

The results are that if you have been careful and not bent anything severely, the bottom skin (at the hinge) in that area will be a little further from the top skin and on the bottom skin it will most likely have a small swale starting at the skin and going forward about 1&1/2 to 2 inches.

Its a trade off, deformity on top, or deformity on the bottom.

On mine I got the top to fit and look perfect and the bottom was only adjusted so slightly that its change in appearance is barely noticeable.

One could put in some fill in the swale but if its that bad, your flap has probably been manufactured with a fat outboard and and may need to be rebuilt itself.

 

[az_gila]

I needed a shim on the top side of my rear spar...

.... if your top skin is not exactly straight - a smooth curve in a fore and aft direction - on the top surface where the flap touches (the swale mentioned above?), a thin shim might make the difference.

 

[MarkSchmitz]

Thanks for the input guys. You've reassured me that one way or another, I've got to get rid of the tension being put on the wing skins by the flaps.

I think I've tweaked the leading edges of the flaps as much as I can without risking damage. I'm going to try shims between the wing skins and rear spars next: Only a few (relatively speaking) rivets to drill out and an easy to un-do if I don't get the desired results. If that's a no-go, I'll try bending (gently) the hinges / bottom wing skin.

Hopefully one the options or the combination will get things where they need to be.

Thanks again -

Mark
RV-8
Slow Build Wings / QB Fuse

 

[MarkSchmitz]

Resolved!

I ended up adding a shim (about 9" long, .032 thick tapering to .025) between the wing top skin and rear spar. Combined with a little additional rolling of the flap leading edge and expert help, I've finally(!) got a good non-binding fit.

Thanks again for the responses and getting me on track!

Mark