This article is from the Model Rockets FAQ, by Wolfram von Kiparski with numerous contributions by others.
From Dan Wolf:
>I am putting together a few rockets with competition in mind, and
>having never been to a rocket competition before, I have a few
>Do people generally paint competition rockets? If so, what kind of
>paint is used, and does performance increase due to smoother surfaces
>or decrease due to added weight?
>And if people don't paint their competition rockets, do they
>generally seal the fins for more laminar flow (this assumes balsa
>instead of G10).
>Finally, what about gliders? Do people paint/dope them or just seal
>them, or neither?
Many competition rockets these days go unpainted, particularly in
duration events where the models often end up thermaling away. Also, a
lot depends on the materials used. Fiberglass and vellum body tube
rockets are rarely painted (although sometimes fiberglass models are
made with colored die added to the resin). Blackshaft tubing is still
used somewhat and it is usually not painted. If the body tube is a
conventional Estes type, some competitors will color it with "Magic
Marker" if anything. For duration, the preference is to go for reduced
weight other than a smoother finish. For altitude, the trick is to do
both. Fins on unpainted rockets are often flown unfinished, or
finsihed with a couple of coats of clear dope (sanded smooth).
Gliders are rarely painted these days. Either magic marker is used to
color them, particularly the underside of the wings (black marker) for
visibility. Or, the glider is tissued with lightweight tissue (ie. Jap
tissue). This adds strength with a minimal weight penalty and also
increases visibility and makes it easier to trim (the tissued stab
surfaces can be more easily warped into position on the field).