Flaps: Part 3

 Over the past couple of days I was able to finish up the de-burring, dimpling, priming, and riveting the Right Flap skeleton. It is always a much better feeling putting things together rather than taking them apart. All in all, awesome!

I don't know why, but I ended up priming the components in small batches. I started with the main spar. After priming the main spar I went back and re-wrote all of the placement numbers on top of the primer due to me not really paying attention during my MEK wipe down. With the main spar primed I went back and laid everything out on the table making sure the order was not disturbed.

If you have been keeping up with these posts, you will know that this is the first major component that I am really doing from start to finish. I had picked this project up from another builder... After internally debating my primer choices for weeks I decided to go with rattle can self etch primer. I remember reading a bunch of posts about self-etch rattle can primer needing a top-coat because it was prone to absorbing things like air tool oil (I am not going to weigh the pros and cons of primer choices here, but even the Vans manual specifically states that they don't think you really need to top coat primer on the internal structure [if you so choose to primer the internal structure with rattle can self etch]). I distinctly remember thinking to myself at the time of reading that, why do so many people call out air tool oil absorption? Well... Take a look at the photo below. This was the first piece that I riveted. I clearly put air tool oil thumb prints on it. So I guess I get it now. 

As everyone other builder has mentioned, a pneumatic rivet squeezer is the bomb!

There were two places in which were un-squeezable. The first I forgot to take photos of, but the center flap bracket with the 2 doublers in it was too wide to squeeze the -10 rivets that hold it together. I initially had heard that from someone else, so when I put my squeezer on them and they fit I was pretty excited. Then when I attempted to actually squeeze the rivet I learned that while the squeezer fits, the problem is actually that because the squeezer is so far extended it does not have the power in the beginning of its throw to squeeze the rivet. 

The second part that was problematic were ribs at each end of the flap. The pnematic squeezer can squeeze the middle rivet, but has a hard time getting in to the top and bottom rivets. While hard to see in this photo, you can see the slight angle on the setup. Even if you bend the rib inwards the bulk of the squeezer makes getting good alignment impossible.

 

 An alligator type squeezer would have been good here. Given that I don't have one I was about to buck these three rivets when I thought I would dig through my tools to see if a manual squeezer would fit. After all, I have never used it, and have heard people say that you should still get a manual squeezer if you intend to go with a pneumatic one. To my amazement, the manual squeezer was able to get a perfect alignment! I guess those things are useful.

While writing this, I realize something pretty dumb on my part. While squeezing the rest of the skelton together I ended up using a 1/2 inch flat set to get around the flange. I tried every configuration I could think of to get the manufactured head on the thinner rib material, but in the end put the shop head on the rib side of the spar so that I did not have to bend and stress the ribs in order to get the squeezer in place.

I don't know what I was thinking while doing this. This isn't a horrible thing, until you hear that I have a flanged yolk for my squeezer that is just sitting in the drawer. The flanged yolk would is designed exactly for this setup, but I completely forgot I had it. O well.

Just some photos:

More Tooling

It was another warm weekend and another great opportunity to spend time in the downstairs shop while I waited out the drying time on the flap primer. There have been two things that while I was building out the right flap that I figured I would build a jig for to make life a little easier when completing the left flap.

The first jig was a good way to machine countersink joggled flanges. The problem with doing this by hand is that even a small micro-step countersink has clearance problems getting into the angle of the joggled flange. That is, the cage hits the angle thus giving an uneven surface to countersink off of.

For this I took some 1/8" 1x2 rectangular 6061 and milled a .060 inset into it. From there I milled a 1/4 slot into that inset to accept the #40 holes (and thus the countersink pilot) from the joggled flanges.

With that done, I was able to remove the cage from the micro-step countersink and use the DRO of my mill to set a zero and accurately countersink each hole to a defined depth.

The results were just what I was looking for! Excuse the scratches in the flange bracket, this was a piece of scrap.

The second jig is for the countersinking of the Trailing Edge (TE) wedges. The TE wedges need to be drilled and countersunk perpendicular to the centerline of the wedge. This is kind of annoying because well, its a wedge. You end up drilling a lot of holes and it would be nice to do this in the drill press rather than with a hand drill in order to keep all of the angles as they should be.

I started with a piece of 1/2" x 2" 6061 bar. After facing the top surface with my SuperFly I milled a 1/2" slot 1/4" deep into the bar. 

Within the main slot I put another .020 deeper slot stopping roughly .250 from each end. The idea here is that I wanted to use a piece of the trailing edge itself set into the base of the slot in order to get the angles correct. Mainly, I didn't feel like re-tramming my mill after this project so rather than set the 10 degree slope with the cutter, I cut a 0 degree slot and used a short piece of trailing edge to be used as the base of the jig.

From there, I made a little cutout to accept the micro-step countersink, hand filed the radius of the base TE corners (to accept the 1/8" radius that was left from my end-mill), and finally drilled a hole through the TE to give some clearance for the pilot of the countersink.

With that complete I was able to take the TE that I needed to countersink and set it into the jig (with the wedge in the reverse direction of the base wedge). This brings the face of the surface I need to countersink perfectly perpendicular to the countersink!