Stuart Grant wrote:

Wings of my 87 Discus had a light craze when I got it two years ago.
About a year ago people who had owned glass gliders a long time said I
really should sand it. Crazing got worse this past year so I spent
almost a week of my vacation between Christmas and the New Year sanding
my wings. With a little guidance from friends it was really pretty easy.
Started with 400 then 600, 800, 1200, 1500 and finished with 3M Finesse.
I will be doing the wax (WX-Block/Shield) this weekend. Did the coarser
sanding at 45 degree angles to the cord with a 10 inch "preppin-weapon"
sanding block and the 1200 and 1500 as full sheets by hand at 90 degrees
and parallel. All was done wet. Used about 8 sheets each of 400, 600 and
800 in quarters and 4 each of the 1200 and 1500. 1 full bottle of
Finesse applied with a 7" polisher and the edge of cloth wheels. Wasn't
strenuous work just dish-pan hands form being wet and sore feet from
standing. I think you can do a wing in about 12 hours once you get the
hang of it. Gel coat is remarkably easy to sand. I did a patch about the
size of my palm that came out just fine other than color difference. It
would be nice if someone who has done it more than a few times would
write an article on the fine points for Soaring Magazine. Bottom line is
that sanding and small gel coat repairs are relatively easy, require
minimal materials and equipment and no extraordinary skill except for
color match. Have no fear.


This is done almost routinely in my club. The club has a permanent employee
who manages the flights during the soaring season and do the maintenance
work during winter. As part of this job he repairs the various scratches
on bellies or wing following outlandings in the way you describe and if
times remaining permits (we have 20 "plastic" gliders) he completely
refinishes the glider with the most cracked gelcoat (the last time this happened
was 2 years ago). Under his supervision a private owner also completely refinished
the fuselage of his Nimbus3 last winter.

When I watched this work, I saw they used a trick that you didn't mention.
Before each wet sanding pass, they paint the surface to sand with red paint
very highly diluted with aceton. This helps to stop the sanding where/when
the paint is gone by sanding.