If you have built (or have attempted to build, or are looking forward to building…) an RV-style metal trim tab, you are probably wondering just how you are going to work with those tiny little ribs that taper away to a dimension far below what you can dimple with any tool you can find. So here’s a tip from our F1 Rocket project.
The ribs on the Rocket are pre-formed from 0.040” aluminum – thick enough that you can countersink it for #40 holes. The problem is how to do this without the countersink wandering about. Using a wood block you can kill two birds with one stone – you can easily drill your rivet holes with precision, and also do the countersinking. Obviously, a rectangular block of wood won’t fit into the tapering rib – but that’s what band saws are for!
Measure the taper of the rib onto a scrap of wood (we always have 1×2 and 2×4 scraps in a box by the cutting tools for this kind of thing). Run it through the band saw and slide the block into the rib. You can now measure and drill the holes with precision, and the nosepiece of the countersink bit will stay put (and not wander) as you countersink the holes. You’ll dimple the skins for a “dimple-into-countersink” fit, and while you can certainly figure out how to buck the rivets with the blade of a large screwdriver (bucking bars won’t fit), you can also just use a small Cherry CCC-3-2 rivet and fill the hole with a daub of micro—no one will ever know the difference.
