On Wednesday, 11 November 2015 02:15:39 UTC, Jonathan St. Cloud wrote:
Any idea how much weight the urethane paint option adds to an 18 meter glider?

PU or Acrylic topcoat paint is just used as a very thin UV block, it is usually a very thin layer and is not used to "profile" the surface. If you are not concerned about the durability of your glider finish and want to maximise performance then just going with gelcoat would be the obvious choice... it also allows you to more easily reprofile the wings once they have done their "shrinking". Schempp seem to be the only glider manufacturer to largely avoid their wings looking like prunes after a few years.

If I was having a new glider I would have the fuselage, tailplane, control surfaces all done in PU and then get the wings and tip extensions painted a couple of years later once the shrinkage has stabilised and surfaces have been "profiled". If you do leave the wings bare then consider having the numbers done in cellulose so they can be easily removed prior to painting.

I would also have the underwing numbers clearcoated and faired in so there are no sharp edges left to mess with the airflow.