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Permalink Reply by Mike Hammond on June 20, 2010 at 12:11pm

The skins are too thin to countersink. The thinnest skin that can be countersinked is .032, end even when countersinking .032 you have to use NAS1097 rivets (100 degree countersink small diameter heads). You could easily dimple the skins and rivet them with MS20470 rivets (100 degree countersink standard diameter heads).

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Permalink Reply by Bob Pustell on June 20, 2010 at 11:45pm

Michael Hammond is right that you could flush rivit only if you dimple everything. Our planes are not fast enough to bother with flush rivits, in my opinion, for what it is worth.

However, one could certainly do a lot of riviting with driven button head rivits. They are stronger than the Avex pulled rivits. However, since Chris designed the airframe around the Avex rivit, I am inclined to just go with them. Much less effort and difficulty.

The very limited areas I am considering useing driven button head rivits are the rivits used to install the upgrade kit T doubler above the wing spar on the outside of the fuselage (to avoid the galvanic problems with the stainless steel Avex pulled rivits that are suppsed to go there). Supposedly, the driven rivits have as much strenth as the pulled stainless, and that keeps aluminum against aluminum.

The other spot I think I might put them is along the rivit line on the bottom of the wing leading edge skin where it rivits to the spar. Several members reported smoking rivits in that area when built to plans. The driven rivits in that inboard few feet might help the joint stay stronger and not smoke or streak.

Finally, the other place where driven rivits will be used is, obviously, in the upgraded spar area, as one reinstalls the driven rivits that were removed to upgrade the spar and center spar section.

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Permalink Reply by Jacob on June 21, 2010 at 7:59am

Thanks guys, sorry ment dimple just used the wrong terminology. Was thinking the dimple option because I thought reverse riveting with a big flat dolly would be kindest to the skins or even just normal riveting. Need to confirm shear and tension strength of the pops so I can use comparable solids. Sad thing is though i'd imagine it will fall right in between a 3/32 and 1/8 solid meaning a 1/8 will be required in alot of spots that are very thin making installation very tricky. Wonder how pure alluminium rivets compare to the pops? probably to weak i'd imagine, be much easier to install though. Might look up some specs. Any more thoughts, opinions?

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Permalink Reply by Jake Reyna on June 21, 2010 at 8:29pm

Jake, I agree it's not worth the effort for all the reasons posted. If the XL/650 was a 150mph+ airplane it might be worth the effort. Solid rivets are stronger and would require fewer, but that's not going to help on pre-punched skins.

If I was going to use solid flush rivets it would be on the leading edge, nose ribs, and wing spar. Ed has a good solution for that path using Avex rivets.

Jake

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Permalink Reply by Dr. Edward M. Moody II on June 21, 2010 at 8:24am

I second the notion that our planes are not fast enough to make flush rivetting a functional benefit. It does offer a nice look and if the appearance is the driving motivation it can be done... the RV guys do it, so can you. It is one hell of a lot more work and is much more technique sensitive than the Avex pulled rivets. A middle ground option is to dimple and use the Avex rivets set with a flat-nosed rivet puller rather than the cupped nosepiece as normally done per Zenith instructions. In any case have fun and good luck.

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Permalink Reply by Chumphol Sirinavin on June 22, 2010 at 1:26pm

Instead of flat-head aluminum Avex rivet, use steel flat-head for strength. I read it somewhere that the cupped nose-piece of rivet gun is an invention of Chris Heintz to turn flat-head aluminum Avex blind rivet into dome headed, with the benefit of the added strength, for same weight.

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Permalink Reply by Jacob on June 23, 2010 at 8:09am

Thanks again,

I think im going to stick with the regular pops simply because it makes the project as a whole so much more achievable. Although I have too admit that it is fun to scheme about alternative ways about doing things. I think the idea of solid riveting some of the reknown trouble spots is a good one which I will take onboard.

Jake

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