The UPS man just delivered a 30# package of spruce capstrip from Aircraft Spruce. I can now — finally — start building.
The first step was to set up the table saw to groove the top and bottom rib capstrips for the geodetic braces. They need a 3/32 x 3/32 groove cut on one side. Getting the saw set up to cut a perfectly centered groove was trivially easy, and it gave me a reason to install the zero clearance throat plate on the saw for the first time. Not wanting to experiment on the expensive spruce, I cut a couple of strips of pine the exact size of the capstrip and used one to set up the saw for the right depth and spacing. The strips are small enough that rather than trying to use a push stick to feed it all the way through, it works out best to feed most of it through in one direction and then flip the piece around and feed the other end in. The saw is set up precisely enough that you can’t see where the transition is between the grooves cut from the two ends. It’s perfect. With that done I grooved a dozen pieces of capstrip and decided that would be good for a limited test run.
I’ll also need a bending jig for the capstrip, since the top piece needs a pretty good curve toward the leading edge. I could really probably do it dry, but I’ll feel better knowing that the wood is less stressed during assembly. Better to put the curve in beforehand, I think. The spruce is flexible enough that I don’t think there will be a problem with the bottom pieces, but we’ll see how it works out. I cut a bending fixture from a chunk of scrap 2×4 — it split on the end as I was finishing up the cut, so I figured what better time to mix up a spoonful of T-88 and epoxy it back together? After all, the glue joint should be stronger than the wood itself. We’ll test that out. Once that glue cures and I get some capstrip soaked in water and bent, I will finally be able to finish blocking in the rib jig and start cutting the geodetics. I’ll need to also set up some sort of rig to sand or plane the ends of those down to 3/32″.
The grandkids are coming over Saturday to get some help with their Pinewood Derby cars. Looks like a full-on woodworking weekend.