Trim tab riveting; need a new tool…again

Not exactly the most productive day.  I was out pretty late at a concert, the band of a former coworker of mine. (shameless plug for Atlantans…Seven Handle Circus, AWESOME)  So after getting home about 2 AM, I slept in pretty good.  Finally got out in the garage around midday.

The instructions for riveting the trim tab are kind of vague, and there’s sort of a lot going on here as well for such a small piece.  I did a fair amount of research on handling all the riveting tasks here, and thought I had a pretty good handle on things.  Even though the instructions call for riveting the lower flange of the spar on first, I knew that doing so would really limit access inside the tab, which I needed to rivet the control horns on.  Actually, I don’t think the instructions ever literally tell you when to rivet the horns on.  So I decided to rivet the horns first, before the spar. (of course, I omitted the forwardmost rivet on each half, since it goes through the spar as well)  This wasn’t much of a problem with the no-hole yoke, but since I have the 3″ and not the 4″, I didn’t have any way to reach the aftmost rivet on the longer horn half.  I tried to come up with some creative ideas, but eventually I just relented and used a blind rivet there.

OK, now for the spar itself…this spar is a bit odd, since the upper flange points forward, while the lower points aft.  Kind of limits access to the rivets there, but I thought I had a good handle on this.  Research indicated that these could be back riveted, and I just figured I’d do that…until I actually was looking at my piece.  I felt like i had to pull way too hard on the skin to get it out of the way for back riveting.  I don’t want to bugger up my trailing edge bend.

That left me with limited options.  The spar is too large to get in there with any of my squeezers.  I suppose I could have bucked the rivets, but there’s no good way I’ve found to clamp the unfinished tab down steady enough for that.  Finally, I hit on a possible solution.  Back when I did the Sportair workshop, we actually did some rivet setting using the C-frame, albeit only with 470 rivets.  Pretty simple, just put the work under the C-frame and bang on it to set the shop head.  And getting the C-frame shaft in there required less skin pulling than the back rivet set, since it was thinner.

Seeing as how I hadn’t done this in a long time, and never with flush head rivets, the prudent thing to do was to practice first, so I grabbed a piece of scrap and drilled and dimpled a few holes.  I taped the rivets in place like I was back riveting, got Josie to hold the assembly in place under the C-frame, and started banging with the dead blow hammer.  A little at first…then harder…harder…this rivet really doesn’t want to set, odd.  I stopped to examine the work and found a problem: the manufactured head of the rivet was not sitting flush in the dimple.  I guess this is why the back rivet set has that spring-loaded collar, to hold the work against the plate and keep the flush head from ending up proud.

So I decided this technique was not a good idea.  Better to get a longeron yoke for my Main Squeeze and do it right…I probably could have borrowed one, maybe from Daniel, but I’ll undoubtedly need one again, so I went ahead and ordered one for myself.  Besides, I feel like there should be some kind of minimum waiting period before I bother Daniel again.  Oh well…I’m on hold until that comes in later this week.

I didn’t even take any photos today.

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