Eric Greenwell wrote:
Marc Ramsey wrote:

I had a trailer with a sandwich top, polyurethane on the outside,
pretty grey spackle paint on the inside. I could read a book by the
light that came through the top when I was closed up inside (the
glider was also painted with polyurethane, however, no gelcoat to
damage).

This is also true of your canopy, but it still stops almost all the UV.
The amount of visible light that penetrates is not a good indication of
the UV shielding. I believe the resins used in composite construction do
a good job of filtering, but I don't have any data for them.

True, but it a trailer which admits no visible light is also likely
blocking UV, a trailer that admits visible light may (or may not) be
also passing UV.

I had another trailer with a sandwich top, gelcoat outside, thick
dark gray paint inside, it was totally dark inside. I had yet another
trailer with glass on steel frame, the gelcoat deteriorated, so I had
it sanded and repainted in white automotive acrylic. Within a year or
two it was obvious which parts of the glider were facing upwards in
the trailer, as those parts were distinctly yellower. I've seen a
glider which had badly crazed gelcoat just in those areas that face
upward in its fiberglass top trailer.

This discoloration and crazing might also be caused the heat and
dampness in the trailer. The upper foot or so inside a trailer can be
very hot in the summer sun, much hotter than the outside air temperature.

Except one could also make out the shadows of the wing saddles, etc.,
which is why we concluded it was UV damage.


An aluminum top protects the glider from UV, even without paint. If I
were to roll the trailer with the glider inside, I'd rather have an
aluminum top. If I lived in a damp warm area, I'd rather have a
fiberglass sandwich top with dark paint on the inside, as there would
likely be a lot less condensation inside the trailer...


Also my sentiments, though I would also consider an aluminum top that I
insulated.

I wasn't offered that option with the last trailer I bought, but it
sounds like a good one...

Marc