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Broken rib stitching

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Dana

Super Moderator
Staff member
Joined
Apr 3, 2007
Messages
12,666
Location
CT, USA
At the risk of starting a flame war over this ever popular subject...

Inspecting my new (to me) FP-404, we discovered numerous broken rib stitches. This may be because the builder used very thin thread instead of the typical thicker waxed thread, though mice in the wings was also likely a factor. Some will immediately say, "recover the wings", but naturally I'd rather not have to do that, and besides, the fabric and paint are in good shape.

So, first question: is rib stitching really necessary on a slow (95 Vne) plane like this? I know opinions vary...

Complicating the situation is the finish used. If it was a simple dope finish it'd be a simple matter to stitch through the existing fabric and dope a patch over each stitch (or a new tape all the way around), but this plane was done with Ceconite, then top coated with automotive enamel... which I _may_ be able to match. AC43.13 says, "finishing tape should be applied as weather protection over all rib lacing", so I'm thinking perhaps I could simply apply the patches over the new stitching with the topcoat enamel... thoughts?

One final wrinkle... which caused wrinkles... is the way the builder attached the fabric at the trailing edge of the lower wings (at the front of the ailerons). I don't have the drawings handy (I took a quick look yesterday and it looks like this is a change from the plans... he made a number of mods, most of which were well thought out). The rib cap strips extend past the rear spar, with another strip of wood attached to the cap strips (but not to the spar), so that the wing cover extends over the aileron leading edge, closing the gap... looks nice and aerodynamically more efficient. However, that thin strip wasn't stiff enough to support the fabric during shrinking, or perhaps the fabric was over shrunk, so it deformed, causing some minor puckering of the fabric at the rib stitches, and another strip was added afterwards to tie it to the spar for more support. Assuming that was done immediately after the aircraft was covered, it's held up for 350 hours so I'm not particularly worried about it, but it may have contributed to the failure of the stitching.

Sorry for the long post... I'm trying to figure out how (or if) I can get flying before winter...

Dana
 
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