Originally posted by Justin
Powderburner-
What do you use to wax and polish the rocket? And by finishing the fins you me to just use some sanding sealer and sand very fine?
If I was wanting to put a smooth finish on balsa today, I would start by applying a light coating of CA. Drip it out onto the balsa and spread it with a Qtip. When the CA cures it will leave the balsa with a rather rough surface because the loose wood fibers rise up. Sand with fine sandpaper (100-180 grit).
Then I spray with something like KilZ primer. Other guys here on TRF have lots of other good ideas for similar primers (do a search). Sand again with fine sandpaper (200-300 grit). If necessary to get a smooth finish, repeat the spray sealer and sanding. Remember that your purpose is to get a smooth surface, not to pile on gobs of primers and sealers. Sand until you think you almost see the balsa coming back through. Spray *lightly* one last time and sand lightly.
When you are happy with the finish you can proceed to the paint stage, but if you are building a competition model you don't want to put a lot of paint weight on the rocket. Spray lightly if you must paint at all. Sand again with even more fine sandpaper (400-600 grit?)
DO NOT overlook getting a tight/smooth fit between the NC and the BT. The diameters should match. Exactly. NO forward- or aft-facing steps (differences in the diams of the NC or BT). Almost all NC parts, as they come from the factory, will require some fitting and sanding to attain this fit. Wrap the shoulder if needed to get a snug, smooth fit inside the front of the BT. Use CA inside the front of the BT and sand smooth. To hold the sandpaper, DO NOT use your finger---the paper will flex uncontrollably and you will sand all sorts of unwanted contours into the inside of your BT. Roll a small piece of sandpaper around a dowel that is small enough to fit inside the BT but big enough to come close to matching the same curvature and contours. Put pressure on the sanding 'stroke' only when drawing your sanding tool out of the rocket. Roll the BT as you make this stroke to try for an even finish around the entire inside surface circumference. After you are done, the BT insides should be hard, smooth, and even, and the front edge of the BT should still be square and full-thickness. If not, throw it and start over (cut off the end of the BT and move down the length of your stock----you did start with a full length of BT, didn't you?). You cannot get a good NC fit if the BT is junk.
For a balsa NC use CA to reinforce the shoulder, and sand gently until you have a snug, smooth fit. Then go to work on the external surfaces of the NC, sanding or filling to make a smooth joint. You may need to insert the NC into an alternate piece of BT to get the NC shape just right if you are heavy-handed with the sanding, because you may damage the outside of the BT near the lip when you are trying to work the NC. OTOH, if you can manage a light touch and not kill the BT, you might be able to work the NC while using your 'good' piece of BT. After your initial joint is smooth, CA the NC near the joint (remove the NC before applying the CA) and then sand lightly to remove the roughness. Proceed with the NC finish like you did on your fins.
If you use a plastic NC you may still have to do a lot of sanding to make the NC diam match the BT diam. Beware of thin spots that may result. Drill a hole in the base of the NC and swab in a little epoxy if you need to fix up a thin spot.
You can use a wax like Future over all external surfaces. Years ago, some of the gang I competed against would argue over which was the best **car** wax to use. Hey, anything that gets you a smooth surface is OK! Polish/buff until you can see reflections!
Don't forget to use an external anchor for your chute/streamer (before you paint or wax). Load the rocket with a used motor casing, pull out the NC and recovery system, and find the balance point in 'descent' mode (you *want* the rocket body to hang sideways during descent to add a little more drag). Anchor your tether there, on the outside of the rocket, and use a piece of heavy linen thread or light kevlar line. To prep for launch, you will pull the excess line snug & straight up the outside of the BT, gather the excess tether and place it inside the front of the rocket on top of your wadding, followed by the chute/streamer.
If you are serious about competition you will not use launch lugs. You will need to make a tower, and you will probably soon want to make yourself a piston launch booster.
OK, all the rest of you guys, it's 'open kimono' time----let's hear all your secrets too!