How much glue? (Aileron and flap covering question)

[Pbruce]

I’m covering a flap in one continuous wrap. My intention is to glue the covering down thoroughly to the bottom TE, then wrap up and around the top of the flap, forward and then down around the LE, then overlapping the formerly glued fabric TE on the bottom TE strip, terminating at the very TE.

I’m thinking that I need at least a 2” strip of glue at the LE. Should I do more, like 4” maybe? Or should I glue the entire sheet metal LE? I am planning to fully glue the ends and also the top of the TE. I’m using Stewart’s so other systems might not be relevant here-I don’t know. Thanks.

[rodsmith]

I think that is similar to how I did mine. If you are using Stewarts now preferred method of coating the fabric with thinned glue after the heat shrink, it will pretty much be glued to the metal anyways. There is one exception, the underside of the ailerons are slightly concave, at least on the A model wing, not sure about the B wing. I would put a straight edge across the bottom and check. If it is concave be sure to glue the fabric to all the metal on the underside and be careful with the heat shrink, but the glue should hold it. Otherwise the fabric is going to pull away from the metal and it won't look good. I made that mistake.

[Pbruce]

Ok thanks. I’ll watch for that. When I took the Stewart’s course, the instructor said that a control surfaces should have at least a 2” perimeter glued. But these are big thick foils, so I’m inclined to glue the material down more thoroughly.

[jaredyates]

Does the Stewards guidance also call for rib stitching, like polyfiber does?

[rodsmith]

Yes you rib stitch also. Where the fabric pulled away was over the aluminum on the underside of the ailerons, just a narrow band.

[spinningwrench]

My Stewart instructor indicated a 1" wrap over tubing was sufficient. Stewart is the only process (compared to Poly-Fiber or Stits) where a 1" overlap of fabric to fabric over an open bay is acceptable from a FAA perspective. Make yourself a test strip where you glue two pieces of fabric together with a 1" overlap and let it dry overnight. You will not be able to pull it apart. Its amazing stuff. If you have concave surface I would recommend you rib stitch especially if you only have the width of a rib to glue to.

[Pbruce]

Boy, it’s amazing how many questions arise about these details when actually working through the process. I watched the Stewart’s videos again, and re-read their instructions (brief as they are).

I ended up doing a 3” overlap at the LE of the flap and spreading a couple inches of glue outside the perimeter of the hinge bays and the end ribs. I will be stitching the ribs but as far as I can see, Stewart’s says to glue fabric only around the perimeter (with overlaps). As Bruce said, that’s 1” min on control surfaces, generally and I think Stewart’s allows as little as 2” on a wing. However, these flaps are like Pitts wings! It’s a long way from the glued strip at the LE back to the first rib stitch so I went wider still with that 3” overlap as extra insurance against fabric lifting. Rod suggests (correctly, no doubt) that the thinned glue applied to the fabric will adhere the fabric to the sheet metal, but maybe it would not be a “complete Stewart’s Systems bond”. I’m sure I went overboard. Thanks to all who commented.

[spinningwrench]

You have plenty of glue area. The 1” overlap test will really convince you of the strength of those joints. The Stewart glue ( made by 3M) is the same stuff used at American Champion Aircraft for their fabric covering.