Wed Feb 17 2021

Fabricating rib doublers

These two pieces of metal are .063 thick material that I previously annealed. I want these to nest in the 3/32" radius of the rib, which will require me to use a much smaller bend radius than possible with -T3 temper. In the -O temper, I should be able to use a bend radius that is as small as 1x the material thickness. preparation for bending those doublers, I tested on a couple samples. This material is .063 thick and I used a 1/16" bend radius. On the top part, the grain direction is parallel to the bend and resulted in a crack. On the bottom part, the grain direction is perpendicular to the bend and did not crack. I'm uncertain if this is because my temperature control was a (suspected) problem when I annealed the sheet, or if it's solely due to the grain direction. Since it's going to be a little while before I can get the oven issues sorted out, I'll order some -O material. Also, I may order some thinner material since .063 seems a bit too thick for these doublers. Van's design doesn't use any doublers at all. Yes, my design will experience ~25% greater load, but even without any doubler, the fact that I have two full ribs to support the pivot (instead of one full rib and one half rib) should already be sufficient. I'll still add a doubler, but I'll probably shoot for .040 or .050 thick instead of .063.

So, I went looking for these bolts in order to modify them, but couldn't find them after maybe an hour of looking. I hate doing this, but decided to just order a couple replacements. Checked Aircraft Spruce...they want $20 EACH for these. Guess who didn't order replacements. I'm going to have to take the shop apart looking for these.