Here, the hone is clamped around the airframe. If the wing nuts are tightened too much, the hone will freeze up against the airframe. I found the best results were with two threaded rods on one side only and a gap on the other side. The flex in the wood provides a bit of variable spring force. The small holes provide a break in the sanding surface, allowing the dust to clear out.
I made these tapered end caps to jam into the rocket, and these aluminum hubs to clamp onto the conduit.
If you try this at home. Make a handle for the hone, and keep your hands away from the threaded rod ends. If the hone grabs the rocket, your hands need to be clear of any spinning metal parts. I put a zip tie over the drill trigger (on a fairly slow speed), and ran the hone up and down the airframe. A lot of dust was generated.
I did a lot of coarse sanding with the drill and hone setup, but I still did final sanding by hand. Jim Jarvis wrote an excellent document on how he builds his rockets, and one of the best tips is after coarse sanding, apply a very light coat of epoxy to your rocket, and wipe most of it off with a rag. This fills all of the coarse sanding scratches, greatly reducing the time spent hand sanding. It is important to avoid drips and runs, so use just enough epoxy to erase the sanding scratches.
With hand sanding, it is so easy to put a flat spot into a round rocket. I use a foam sanding block. I keep it aligned along the long axis of the rocket, and make a motion as if I'm following an imaginary candy cane stripe painted on the rocket. I switch directions, and the pattern left behind is a series of X's. Let's see if this gif I made works.
Watching this in a continuous loop makes me anxious, because the last thing you want to do is sand too much, and cut into the carbon fiber (or glass fiber if you are working on fiberglass). If you break through the epoxy only layer, stop right away. If more sanding is needed, add a coat of epoxy, let it cure, and sand some more. With practice and patience and a lot of thin epoxy layers, it should be possible to avoid ever sanding into the fiber reinforcement.
I use automotive body filler (bondo), in very small amounts to fill pin holes, and to get my upper and lower airframe to line up better.
But when I have rocketpoxy left over from another operation, I will use it as body filler. Here I am filling the seam of my nose cone halves.
This is automotive rattle can primer (rustoleum or duplicolor primer work well for me).
This is engine block orange and engine block clear from Duplicolor.
