My first serious attempt at this and am using Ultracote. The instructional videos make it look easy, but man-o-man is it a challenge! Let me see if I got this right- if you want it to stick, you apply heat; if you want it to unstick, you apply heat; if you want it to stretch, you apply heat; and if you want it to shrink, you apply heat. So let it be written, so let it be done. Ha!
Dave Mo…
Pretty much, yes. It's common for a covering to be designed so that the glue melts at a lower temperature than the covering shrinks, so on flat or simply-curved surfaces you want to stick it on at that temperature, then shrink it later.
It only stretches if you heat it up to it's "shrink" temperature and pull on it -- and it'll stretch in the direction you're pulling while shrinking in the other. This is basically
the trick for getting covering to go around a complex curvature like a wingtip or cowling.
This is in pretty much all the books & videos, but you almost always use an iron to stick it down and a heat gun to shrink it. There's good exceptions to that rule in both directions, but if you're not sure what to do -- stick it down with an iron, shrink it with a gun.
There is a learning curve -- don't be discouraged if your first attempts are wrinkled-up messes. You need to get a feel for the material, and if you switch brands you need to get a feel for
that one (eventually you learn how to get that feel pretty darn quick, which is good if you're working with a hoard of swap-meet MysteryCote).
I almost always cover over bare balsa,
except I've built a lot of profiles with the fuselage finished in silkspan or fiberglass using Minwax polycrylic to about an inch out on the wings, then white Rustoleum, then cover the wings with white 'coat and paint on trim.
It's versatile stuff. Way easier than silkspan & dope to get a good functional medium-good finish, probably harder to get a 20-point finish (folks will dispute this -- hence my "probably"). Just like silkspan & dope you have to understand and respect the medium if you want to get the best out of it.