The hot weather canopy closing problem is often due to the plexiglas's
high thermal coefficient of expansion, and hot weather. The canopy
expansion is much higher than that of most fuselage composites. The
manufacturers generally ship their sailplanes with nicely fitting
canopies, when the air temps are about 75 degrees F (I think). So when
we bring them to our hot summers here, it is really necessary to sand
some of the forward and aft edges of the canopy to get them to close
properly.

A strip of carbon paper placed in the canopy gap before closing will
clearly mark the interfering areas. I try to sand the canopy frame only
to achieve the needed clearances.

I remember the Polish Team sanding vigorously on their canopies when
they first came to Uvalde for the 1991 Worlds Championships.