Wings 50, Total 513 Made Decisions for Final Support Bracket Work

I think I reached some decisions about countersinking or dimpling several of the holes in the outboard aileron support brackets, an also for the skin attach holes on the inboard section of the rear spar. But first.... almost done with the shed doors. Just a small amount of painting left to do and I'm finally done with that fiasco.

New doors in progress:

Looks kinda funny - brand new doors on a scrappy looking shed, but oh well. Maybe it will last a few more years before the whole shed needs to be replaced.

So I decided to countersink the 4 holes on the outboard-most edges of the two aileron support brackets instead of dimpling them as someone at Vans suggested. The reason is that I did a sample countersink on a piece of .040 scrap aluminum from the trim bundle that I received from Vans, and I also checked the info in Chapter 5 of the manual. The spar and the support bracket are both made from .040 thick aluminum.

The manual shows a pic with 3 examples for countersinking. One with a top skin thicker than bottom skin, one where both skins are the same thickness, and one where the top skin is thinner than the bottom skin. The one where both skins are the same thickness, which is also the case for the assembly of the brackets to the rear spar, shows that the minimum acceptable countersink situation is where the countersink just hits the bottom of the thickness of the top skin, or in other words when you countersink you do NOT go deeper than the thickness of the top skin.

I was able to achieve this by countersinking the holes, whereas the guy at Vans was telling me that I would end up countersinking into the rear spar just a bit if I did this. Several other builder sites and my own test countersink confirmed that this works just fine. If I dimpled the support bracket, I would also end up needing to dimple the rear spar and the rib flange, and I was just not going to go there.

This pic shows a trick that I had tried a while back when countersinking the nut plate rivet holes for the spacers for the tie down and aileron belcrank brackets (when my countersink bit broke.) I butted the two brackets together on the last hole to provide enough surface area for the countersink cage to rest on so that I could create a good countersunk hole.  Worked pretty well on both holes.

For the hole closest to the top flange of the bracket, you cannot get the countersink cage to fit in this area at all, so out came my cordless drill and the deburring bit that I have used to create countersunk holes for the elevators. The first one ended up a bit oblong for some reason, and I was able to clean it up enough by finishing it by hand instead of letting the drill do all the damage. I think this happened because I did not support the deburring bit with my fingers as I started the hole.This allowed it to grab and wonder in the hole just a bit.

When I did the bracket for the right side I spent more time finishing the hole by hand - harder on the hands and fingers, but the hole came out much better. I used the deburring bit in the drill to start the hole and get it to a certain depth where the head sits just proud of the hole, and then I removed the bit from the drill and turned it by hand a little at a time until I was satisfied with the fit of the flush rivet head against skin on the bracket. These rivets must sit absolutely flush because an angle support bracket for the aileron hinge gets placed directly over the top of them, and the angle sits flush against the support bracket. The ailerons will get used a lot for banking the aircraft, so the hinges need to be securely fastened.

And finally both brackets with countersunk holes, next to my test piece of aluminum where I tested the countersink before doing it on the actual parts:

For the inboard skin attach holes, I decided to use the tank dimple dies on the first 9 inches of holes on the top flange of the rear spar, because there is a doubler skin that goes over the main skinthat is about 9 inches wide by 26 inches long, and the two skins then attach to the rear spar flange. The tank dimple die gives a slighty deeper dimple (also tested this on the scrap .040 aluminum), and this will allow the additional doubler skin and the inboard wing skin to sit in the dimple on the rear spar flange nicely I think. The remaining spar flange holes that make up the remaining length of the doubler fork can be dimpled with the standard dimple dies, since only the wing skin attaches to these holes. I used a test piece of .032 thick aluminum with a 3/32 dimple to verify the fit.

What is the doubler skin for you may ask? This is the platform on top of the wing that everyone will stand on so that they can step into the cockpit of the aircraft, and take the ride of a lifetime. I think that this approach will work out well.

Lastly, there are 4 skin attach holes on the outboard support bracket that I think I will also predrill to #40. Vans told me to leave those until I assemble the wing skins, but the more I thought about, I realized that the skins will need to be clecoed to the spar, and until these holes are drilled through the solid bracket flange, I will not be able to insert the clecoes. The other reason is that I want to be able to debur the holes in the support bracket flange. If I go ahead and rivet the bracket to the spar without drilling and deburring the holes first, I will not be able to debur them later. So there is no time like the present to make sure all the holes are clean.