Spar attach fittings, flox or microballons?

[Av8r3400]

[southwind32]

That is hilarious, I got my laugh of the day.

I'm right in the middle of my condition inspection. Maybe I need to verify whether it has micro-baboons or micro-balloons because I didn't build the wings.

What do you get if you mix micro-baboons with Gorilla glue?

Micro Go Booms

[David47]

.... The fittings in question are attached with a lot of rivets, and the epoxy should add additional strength to the joint, so why not make the joint as strong as possible and not decrease the strength with micro, while still sealing the contact area between the dissimilar metals from air and moisture? My original comments were just voicing what have been my thoughts from the beginning of my Kitfox project.

Just a comment on yours John. Joints like this that are bonded and riveted gain most of the strength from the adhesive, provided the adhesive has sufficient shear strength, which Hysol has. The rivets provide clamp up and squeeze out of the adhesive, and also provide residual strength in the event the adhesive degrades. Case in point is the Aloha Airlines 737 that suffered major structural failure when the fuselage lap joints unzipped the fuselage section above the cabin floor. The primary cause was degradation of the adhesive bondline of bonded and riveted skin lap joints, which then caused high loading on the rivets over time, which eventually lead to multiple fatigue cracks between rivet holes and then bingo, the joint(s) let go. There's a lot more to this story than that but it serves to demonstrate the idea.

With respect to Kitfox, the wing joints are a proven design with many years of safe operation, all having been built to the manual requirements so that speaks for itself. In my particular case, however, I didn't use micro-balloons (or micro-baboons per Larry's redefinition ..!!) for the very reason you said. Maximum joint adhesive strength. But that's a personal choice and something I can do because my aeroplane is Experimental.

[cposer]

Anyone thought about using cherrymax instead of SS rivets for the spar attach fittings?

[efwd]

If I recall, they are really expensive.

[jrevens]

Anyone thought about using cherrymax instead of SS rivets for the spar attach fittings?

Another question - why would you want to do that? There is nothing wrong with using the rivets furnished in the kit. I think they have been well-proven to be adequate and safe for this application. In my opinion only, you could certainly use the stainless steel CherryMax rivets for the spar attach fittings if you wanted, or the slightly oversized version if you had an oversized hole within the tolerances of that oversized version of the rivet, but as Eddie said, they are very expensive.

[Flybyjim]

Being an experimental aircraft you can do as you please, that is part of the fun building however for me if the suppling company, aka Kitfox, has a proven history of saftey with their design I will stay with their plans and listed parts to complete the build.

[David47]

I bought Cherrymax for precisely this use. But didn't use them (duh). As I said earlier, the adhesive does the work. The limiting strength, should the adhesive fail, is the bearing strength of the tube, making the type of rivet used irrelevant. An opinion ... I'd just use the ss rivets with the kit.

[jiott]

Spend your extra money where it matters, like some nice options you will enjoy.

[Guy Buchanan]

The other problem with the Cherry-Max rivets (I have them) is that they're big and ugly on the leading edge. I minor consideration, to be sure, but worth mentioning for all you Oshkosh aspirants.