Covering fabric control surfaces... what about TE?
 

Getting ready to do my first Koverall fabric control surface job on my SBD and have a question about technique.

The control surfaces are built with an aircraft ply core, then ribs are built out from each side (from the ply core/center). Pretty common construction. My question is this... when you get to the trailing edge, the ribs taper down to nothing at the TE, so when you cover one side, overlap the TE to the other side, you get a little bit of a "tenting" effect as the fabric goes between ribs. Unless, you don't iron the fabric to the ply core except for it's very end/edge.

If I only iron it to the actual edge of the core, that means the fabric is only connected to the TE in a 1/16" wide area for the full length of the surface. Seems like this would pull loose very easily. I would prefer to anchor it to the "face" of the core at least 1/8" or so down the length of the surface. But, again, that makes somewhat of a nasty tenting effect as it goes over the tapered ribs.

Also, same issue when you do the opposite side of the surface, plus, do you go ahead and overlap it across to the opposite side 1/8" or so like you would if you were glassing it? This seems to make a nasty seam on the opposite side surface face, and you can't sand the seam out like you can on a sheeted surface.

Looking for tips.

Thanks,

Tom

RE: Covering fabric control surfaces... what about TE?
 

Tom:
I glue a strip on like the triangular piece, between the ribs, and sand it level with the ribs. Maybe 1/8 or 1/4 in depending on the size of the plane. The real plane would have had an aluminum U shaped channel along the trailing adge riveted to the ribs. This would simulate it quite well. Hope this helps. Just got through doing a FW 190 D9 this way.

RE: Covering fabric control surfaces... what about TE?
 

The full scale would have all those faults in the covering, but these wouldn't be noticed due to the scale effect.

RE: Covering fabric control surfaces... what about TE?
 

Flypaper, that's exactly what I thought and was planning on trying. Thanks for the tip.

Tom

RE: Covering fabric control surfaces... what about TE?
 

If you cover the bottom first and trim it flush where it overlaps, then overlap the top onto the bottom it should not come loose. Just be sure to seal the seam well. You can add an extra piece at the trailing edge as has been suggested, but it's really not necessary.

Also, when you shrink the covering, avoid putting heat on the edges while it's shrinking. Kind of hard to do sometimes, but it's not impossible. I've been in that situation several times and managed to get it to work.

Good luck.

RE: Covering fabric control surfaces... what about TE?
 

I've built two Haffke Gee Bees with ailerons like that. I left the core piece about 3/32" thick and radiused it slightly. The covering seems to stay attached pretty well to just that small area. Just get it on smooth to start with and you won't have to do too much shrinking.