Starting on the Rear Spar   May 16th, 2007

With the tiedown bars out of the way, it’s time to start on the rear spar. This is a Z-channel with some reinforcement plates.

The first plate is at the tip of the spar. This is where one of the aileron brackets will mount. It does not come pre-drilled, so I aligned it to the edge of the spar and clampled it, and used the holes in the spar to match-drill the doubler.

After drilling, the row of holes closest to the tip of the spar needs to be countersunk. Note that there is one more hole that will have a countersunk head rivet. However, there is a piece of angle that actually goes on top of the doubler, and IT needs to be countersunk, not the doubler! By the time I figured this out, I had already countersunk the hole. I figured it’s probably OK, but it’s a cheap part, and it will basically be holding my aileron to the wing, so I went ahead and ordered another one 🙂

Also, the hole closest to the 90 degree bend is too close to the bend to use a countersink cage, so I had to free-hand it. I chucked the countersink on the drill and went slowly, checking for depth often. Turned out pretty good…too bad I’m doing this piece again in a couple of days…

The doubler in the middle of the spar is aligned by measuring 50 3/4″ from the edge. I used the same method to match-drill the holes.

In addition to the #3o holes, there is a funny-shaped hole that needs to be cut out for the aileron pushrod. I traced the shape with a marker, and then used a unibit to drill a couple of holes sort of close to the final shape…

Then I used a Dremel tool with a little drum sander attachment to get the final shape. I was very pleased with the result…see for yourself!

Finally, there is a fork-shaped doubler that goes on the root end of the spar. There is also yet another doubler that goes on top of the fork. This is where the rear spar will attach to the fuselage…

Posted in Dremel, Rear Spar, Wings | Comments Closed