Over the last few days I match-drilled the #30 leading edge-to-counterweight holes in the left and right ailerons. For those of you who aren’t familiar with an RV aileron counterweight (and that’s probably most of you), it’s simply a length of galvanzied steel water pipe that’s blind-riveted inside the aileron’s leading edge. Its purpose is to add some aerodynamic balance to the control surface, and to improve aileron control feel.

Nothing magical here, the only minor trick is getting everything up off the workbench when drilling these two parts in assembly because the leading edge skin is pretty flimsy and can be easily damaged by horsing the counterweight around. After drilling these holes, the counterweight is countersunk and the leading edge skin is dimpled. There’s no real mystery in countersinking the weight, you just need to know how deep to go. I went far enough so that the edges of the blind rivet are completely enclosed by the countersink; that means that the hole actually is an oval in the pipe. Sorry, no pictures of the hole – only the pipe. Use your imagination.

But how do you dimple those holes in the leading edges that will nest inside the countersinks just completed? There’s a simple trick – just cleco the weights back into the leading edges, support the assembly with a 2″x4″, and use a male dimple die to press a dimple into each countersink. Doesn’t have to be perfect, since the skin and blind rivets are prett soft and will give somewhat when riveted. To make this process easier, I stuck a #30 male dimple die into my old non-adjustable rivet squeezer set – like in these pictures.

A couple of light hits on the set with a dead-blow hammer, and the hole is dimpled. A CS4-4 blind rivet fits pretty well…