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Getting ready to mount wings, we now find that the rivet we were required to install on the Front Upper Strut Fitting (75W2-5) and Doubler (75W7-1) interferes with installation of the Front Upper Strut Fitting (75W8-2). We drilled and riveted exactly as shown in the drawings, but now find the rivet is not only unnecessary, but it interferes. Our options seem to be:
1. notch the strut fitting on both sides to fit around the rivet,
2. replace the rivet with a flush rivet and only notch the backside of the strut fitting,
3. fill the hole with an aluminum type liquid steel such as Scotch Weld, or
4. remove the rivet and live with the hole.
Hi Loren, I have a fifth option for you, countersink both sides and set a double flush rivet. A pancake drill with either a deburring bit or a very shallow counter sink bit should be able to countersink the top hole.
This website has a discussion that may (or may not) describe it better.
For what it's worth, I'm considering not installing it. The bolt seems to be doing most of the work in this joint.
You may get many different opinions on this, go with the one that makes the most sense to you.
Hope this helps! Good luck!
I've never seen a pancake drill or double flush rivets. Something to look into even if we don't use it.
I'm hoping someone who has been flying their aircraft for a long time, after performing one of the other options will chime in.
Understood, I look forward to hearing how other builders have approached this.
Just for reference, here is the setup I might use to perform the countersink for the top hole, not much clearance in that location, the pancake drill attachment is available at yardstore.com. I've also attached a picture of a practice piece I used to try out the double flush technique. First try was a complete failure, countersink was too deep. Second try was better. Still need more practice before I try it on the real part, if I decide to do it at all.
David, this may be a long known problem to some Zenith builders, but it completely escaped me. Our 750 STOL is the latest version, and it's incredible that the builders guide and plans continue to require a rivet that we later need to replace.
I just got email from Roger suggesting we "replace with a countersunk flush rivet and notch the backside of the strut fitting."
I agree with David. The rivet IS necessary and apparently acts as a stress relief. I recall a simplistic explanation that "stress flows to the path of least resistance, just like water, and the rivet controls where that stress flows."
On my build, I pretty much installed the rivet per plans. I had to slightly radius the fitting's edge to clear the rivet and it seemed to work OK ... or at least has worked OK for 500+ hrs! ;>)
Ok, so doing as Roger suggests by replacing with a flush rivet and slightly notching the back side to fit the rivet should suffice, although not as clean as Clint's double flush rivet.
Thank you guys for the information.
Actually, I stole the idea from David. I've been trying to keep my workmanship standards on par with David's, John's, and Joe H's planes (along with a bunch of others on this forum). I figure if my plane turns out half as nice as their's I'll be happy. Keep up the good work!
You guys left me in the dust a long time ago, following the rudder build.