The horizontal stabilizer on our F1 Rocket (like most RV-type aircraft) has a very thin profile—a symmetric airfoil with a finely pointed nose. Getting the sheet metal to lay down tightly on the leading edge ribs can be tricky—you can only bend it so far without risking a crease. And even then, getting a perfect fit is tough. Clecos just won’t hold tightly enough, and sooner or later, you’ve got to take the last one out.
Here’s a little trick to get the skin to lay down perfectly while riveting. It’s a squeezer frame made out of 1×2 pine lath (try and find some straight ones from the big box store (it’ll take some searching) and some all-thread. A few fender washers and appropriate nuts complete the squeezer. Now comes the trick: Use a plastic carpentry shim against the surface of the skin, and wedge a little block of wood between the plastic and the long “bow” of the clamp. Squeeze the ends of the clamp by hand and tighten the nut down – this will put the pressure right on the nose, and lay the skin down on the rib for that last rivet.
(Caution: If you need a wrench, you need to take everything apart and squeeze the skins some more or you risk puckering the skin at the ribs and pillowing it in between them.)
This is just about the cheapest tool you can make, and it does a great job!
