Luis & Fab's RV-7A Construction Log

Here is a close up of one of the fuel tank vent lines. This is just a tube that goes along the entire length of the tank, and it terminates open on the inside near the fuel tank. It goes to a fitting on the last rib (shown removed in the picture), and eventually goes to a drain on the belly of the plane. This is so that pressure (or vacuum) doesn’t build up in the tank and causes it to burst. When I get ready to install the inboard rib, I will flare the end and hook it up to a threaded fitting. You can see the blue nut near the rib in the picture below.

This was my first time using a pipe-bender, and it wasn’t bad at all. Of course, the aluminum tube is very soft, so it is very easy to work with.

So, how to draw a line that goes exactly through the center of the flap hinge, along the entire length of the flap? I could use a very long straightedge, which I don’t have, or try to rig up a piece of string, etc, etc. Well, instead I found this $14 edge marker block at Avery Tools. I’ll be the first to admit that paying $14 for two pieces of plastic and a screw is very very unlike Mr. Cheapass here, and even now it seems like quite a bit for what it is. However, when you think this is probably hand-made (or very nearly so), and it saves a lot of grief, it probably is worth the fourteen bucks. Anyway, Here is a picture of said tool. You stick a marker in the hole, set the distance for exactly half the length of the hinge, and just draw a nice, long line, as straight as the edge of the flap itself. The only trick is to keep the arm resting on the edge of the hinge at all times.

So the flap rear spar and the inboard rib are not at 90 degrees to each other. In fact, they are at something like 96.5 degrees. This means the flat bracket you get as part of the kit has to have a 6.5 degree bend. How do you do this you ask? Well you whack the heck out of it with a hammer!

I’m not kidding either. I put it in the vice between two blocks of wood, and then went at it with the hammer. This is 1/8″ aluminum, and there is not a lot of leverage, so I had to hit it pretty hard for it to move.

How do you know when to stop hitting it? You take it off the vice, test-fit it on the spar with the other bracket, and then go hit it some more. When the two brackets, the spar, and the rib all fit really nicely, you quit hitting it!

This is what a 6.3 degree bend looks like:

The piece on the top is what the bottom one looked like before cutting, drilling and sanding.

The next two pictures show the brackets in place next to the spar and rib. Note that the first picture shows the square bracket before drilling. Because three of the holes will go through the bracket, the spar, and the rib, this one has to get matched drilled to the spar and the rib.

So, I first clamped everything in place, and then used a long 12″ drill to drill from the rib side through the pre-punched holes in the spar and into the bracket. Not hard as long as you have this handy 12″ drill bit.

Decided to take a quick break from the tanks and work on the flaps. I started by clamping together the flap skeletons, and then the bottom flap skins.

The skin itself is used as the ‘rear spar’, and the ribs don’t always get close enough to the skin. So, I had to make tiny shims out of 0.025″ aluminum to insert between the rib and the skin-formed rear spar. Also, because these rivets will be completely enclosed by the flap skins, they are AN470, 1/8 inch. It is very tempting to just drill them #40 (which is what I did initially), but closer inspection of the plans will set you straight.

Here is the flap with the top skin on.

The most inboard rib will have a bracket rivet to it. This bracket eventually connects to the rod that makes the flaps go up and down. Also, it is important to make sure the rib is oriented correctly. You can tell because the tooling hole on the left (closest to the front spar) is closer to the bottom of the flap.

Next time, I’ll work on making this bracket. Apparently it uses a very non-conventional fabrication method…

These are the brackets that hold the ailerons to the wings. They come pre-shaped, so I just had to match drill and deburr them.

The next little thing was cutting off a piece of the flap brace. The flap brace is a long thin piece that goes between the wing rear spar and the bottom skin. It gives the skin a little more strength, since the flap is hinged on the skin only (well, and the brace). In order to clear some of the rear spar reinforcement plates, you have to take off a piece of the brace as shown by the blue line below. Just a matter of taking the snips to it and cleaning it up a little afterwards.

After that, it was just a matter of fitting each brace on the wings and match-drilling, then on to get primed.