Flap Hinge May 28th, 2009
One of the last steps in drilling the flaps was the flap hinge. This is a piano hinge that holds the flap to the wing, so it goes along the length of the entire flap. The hinge is not very wide, and it is not pre-drilled. This leaves very little margin for where the holes are drilled. If the are pretty much not right dead center of the hinge, the rivets will be too close to the edges.
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.
After drawing this line, I just clamped the hinge to the bottom of the rear spar. I used little wood blocks with a round cutout so my clamps wouldn’t squeeze the loops in the hinge. Finally, I just made sure the line showed exactly through the middle of all the holes int he flap, and started drilling away, putting a cleco in every hole.
Now it’s time to take everything apart and prime. Back to working on the fuel tanks!