Flaperon rivets missing

[GMKman]

Hello. I'm new to Kitfox ownership and have recently purchased a Kitfox vixen and have noticed that my left flaperon is missing 3 rivets on the trailing edge. Is this a normal maintenance occurrence? Should I just get the rivet gun out and put some new rivets in or should it be replaced?

[TahoeTim]

a little scary

looks like its delaminated - consult the experts on that one :)

[Dave S]

Brad,

First time I have ever heard of this happening....no...not a normal occurance - not at all.

A couple things on construction of the flaperons - 1) the flaperons are laminated at the factory - the spar tube, foam ribs and trailing edge of the flaperon are bonded together in a jig at the factory, I believe bonding is done with Hysol. 2) The builder is the one who puts the rivets in the trailing edge.

In any case - looks like in addition to losing some rivets - possibly the foam rib has delaminated as well as the trailing edge.

Check the rivet holes - The original spec calls for the builder drilling 3/32" holes for the 3/32" rivets using a #40 wire gauge drill. Check to see if the holes for the rivets are 3/32".....This is the only place on the plane where the smaller rivets are used. If the original builder happend to have used a #30 wire gauge drill (which is used all over the plane for other rivets) - that would result in the 3/32" rivets not fitting tightly enough to grip...I have no idea if that is what may have happened - but it would explain what you see if it did happen. Also check the trailing edge rivet spacing - the specification is 4" spacing. For the missing rivets - also check to see if deburring may have been overdone - the skin of the flaperons is thin and if a deburring tool was pushed too hard - it could have enlarged the rivet hole enough to let the rivet pull through.

In any case - I don't know if it is even possible to do a thorough/safe repair if the ribs delaminated from the skin as the original assembly is done in a factory jig (except for the ends and the riveting of the trailing edge).

Check the rivet holes for size in relation to the size of the rivets which should have been used - again - I don't know that from the photo but it's a place to start to figure out why this happened because I don't think this happens if everything is assembled according to the manual.

Wish you luck,

Dave S

[HighWing]

Not an expert. Since the flaperon has a spar running full length that bears a good portion of the control torque, this is what I would do. I would squeeze the trailing edges together using clamped half inch angle iron top and bottom. If the entire trailing edge lines up, I would first clean the mating surfaces then glue the trailing edge back together with a structural epoxy adhesive. After curing, add back in the rivets. Regular clear packing tape would make a good separating medium to prevent glue adhesion to the angle.iron. i should mention that the rivets are like "suspenders" to help support the adhesive - "belt". If the trailing edge won't line up you may need a new flaperon.

[cap01]

if you do determine that you can rehysol and reinstall rivets be sure not to use ad rivets, use only a rivets and don't use a rivet gun . the a rivets squeeze easily. the flaperon skin is way too thin to try and shoot rivets

[TahoeTim]

I am wondering if the damage was a result of a wing fold accident? Are there any dents in the trailing edge?

[GMKman]

No, there are no dents anywhere throughout the flaperon. Not even any scratches. I just got the plane a week ago and noticed it yesterday during preflight.

[t j]

I had a flaperon delaminate on the trailing edge early on during my flight testing due to a poor job of riveting I did. I had used a 100 degree counter sink to taper the holes in the top skin to get a flush fit of the solid rivet heads. That was a bad idea. A rivet head had pulled through the skin and the trailing edge popped apart right there.

I re-glued the delaminated spot with hysol then drilled out all the solid rivets and replaced them with aluminum pop rivets. No more problems.

[GMKman]

Thanks for.the advice. The holes are a bit sloppy so thinking about going to 1/8 pop rivets and using Hysol. Again, new to Kitfoxes and Googled Hysol and found many different types. Is this the one you guys recommend? What prep do I need to do?

[Dave S]

I believe Kitfox uses the 9460 - should be in their parts catalog page 28

[Paul Z]

I've had this happen on my Kitfox SLSA it was on the right flaperon. It did start separating. I sanded re-epoxied and had to go with a rounded head rivit wher the rivit pulled out. I added two additional digits on doth sides of the rivit that pulled out. On preflight a, I now inspect between each of the rivets to check for delamination. When I was flying out to the 2015 Kitfox Factory Flyin I noticed it while unpacking in Abilene, Texas. I got socked in in Abilene with fog, I did a temp fix and when the weather cleared I flew home.

[HighWing]

I believe Kitfox uses the 9460 - should be in their parts catalog page 28

I hope this doesn't result in a debate, and I have no personal experience with the 9460, but do have experience with the "Structural adhesive" shipped for wing assembly in the early Kitfoxes. My opinion is that the 9460 is application specific - meaning with a thick consistency appropriate for building a fillet on the ribs as the wing is being assembled.

I have used the 9430 for many years - available at Aircraft Spruce. It has a honey like consistency and is excellent for bonding thin materials face to face. That would be my choice. It has no fillers that, also in my opinion, would tend to result in cracks in the adhesive. If it were my airplane, I would use the 9430 but with a thorough preparation of the mating surfaces - lots of careful going over with something like 300 grit sandpaper. rinsing with Acetone, then more sanding.

[Paul Z]

If the rivets keep popping out the results could be catastrophic. I ubmitted a safety write up to John.

[Northof49]

If the holes are sloppy , you can drill them up to a 1/8
And dimple the hole . Then put a Ad 426 -4 solid rivet back in.
.016 is to thin to counter sink it knife edges .
1/8 dimple dies at AC spruce $24.
Mike

[jmodguy]

While you are "out and about" a roll of gorilla tape can come in pretty handy...

[GMKman]

I definitely second the duct tape idea!!
It kept my last plane (Glastar td) in tact a few times in a pinch.
After doing much research and listening to the comments here, I'm thinking about using this stuff for the epoxy aspect of this repair.
Has anyone used this and if so, what's your thoughts?
From what I've read, the only two things that will withstand a nuclear blast is cockroaches and the two pieces of aluminum I bond together with this stuff.
Brad..

[jiott]

I would personally stick with the Hysol 9460. Don't think you can beat it, other than what Highwing says maybe the same stuff but different consistency.

[dholly]

A bit late to the party but IMHO... G-Flex would be appropriate for this purpose, and maybe more so than either Hysol due to it's modulus of elasticity properties. I used it for bonding dissimilar materials (Plexi to aluminum) and my testing showed very tenacious results. While there is no need for the ability to withstand expansion/contraction of dissimilar substrates in this instance, there is flexing of the flaperon skins in flight and perhaps some elasticity under both tensile and shear stress in this application would be a good thing.

From West Systems:


650-8 G/flex Toughened Epoxy

A toughened, versatile, liquid epoxy for permanent waterproof bonding of fiberglass, ceramics, metals, plastics, damp and difficult-to-bond woods. With a modulus of elasticity of 150,000 PSI, it is a bit more flexible than standard epoxies and polyester, but much stiffer than adhesive sealants. This gives G/flex 650 the ability to make structural bonds that can absorb the stress of expansion, contraction, shock, and vibration. It is ideal for bonding dissimilar materials. It can be modified with West System fillers and additives, and used to wet-out fiberglass tapes and fabrics. Mixed at a 1:1 ratio, G/flex 650 gives you 45 minutes of working time at 72°F. It reaches an initial cure in 7 to 10 hrs and full cure in 24 hrs. (8 fl. oz. / 236 mL)

[GMKman]

Thanks for the responses. I agree and think the gflex will be what I use as I can peel the existing epoxy off with just my fingernail.

[jrevens]

I agree that the G-Flex sounds like it might be a good choice for this issue. The fact that you can peel the old stuff off with your fingernail points to probable improper preparation of the mating surfaces before bonding.