On Sunday, November 15, 2015 at 5:24:23 PM UTC-5, wrote:
PU does seal that surface up better, mostly because it seals up the porosity in the gelcoat as well as being a much better UV barrier.
UH

UH...Curious as to the factory steps taken to apply a PU finish. Is everything the same (same gelcoat, same thickness, same sanding, same prep, et cetera sans waxing) then the wing is taken to a paint booth and sprayed like a car?

After spray painting, are the wings sanded or "rubbed" in any way?

What is the current "favorite" maintenance wax or polish for factory finished PU?

Thanks for your response.

I used to work in the paint shop at schempp-hirth.

the two processes are quite different.

What they do for paint is this: they apply a thin layer of molding gelcoat to the molds. it provides excellent adhesion to the composites, and releases from the mold nicely. when the fuse/wing/whatever is pulled from the mold, the thin layer of molding gel-coat is scuffed with sandpaper. at that point they then spray urethane primer, wetsand it, then do a PU topcoat, wetsand it. then its ready for trim stripes/ decals and polishing. after any striping, they also offer clearcoat to remove the lip edge of any decals/contest letters et cetera. but that's only applied in the local area of the decal.

With gelcoat the process is the same, except after the mold they just spray gelcoat onto the scuffed molding gelcoat.