Canopy Closing Problem

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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.

[Mal]

Cool water on the canopy does the trick.

[Andy]

Until you land and find you can't open it.

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I had a similar problem when I was flying a Ventus B. If help was
available, having someone push down on the nose distorted the fuselage
just enough to allow the canopy to close without too much trouble. I
tried the sanding route too with little improvement.
Between heat and humidity you can have some significant expansion in
materials. Most canopies are made from a material that is hygroscopic
and if you move your glider from a dry climate to a wet/humid one, you
can count on seeing and feeling the effects.
The forward hinged canopies seem to tolerate these effects better.
Respectfully,

[Eric Greenwell]

wrote:
> I had a similar problem when I was flying a Ventus B. If help was
> available, having someone push down on the nose distorted the fuselage
> just enough to allow the canopy to close without too much trouble. I
> tried the sanding route too with little improvement.
> Between heat and humidity you can have some significant expansion in
> materials. Most canopies are made from a material that is hygroscopic
> and if you move your glider from a dry climate to a wet/humid one, you
> can count on seeing and feeling the effects.
> The forward hinged canopies seem to tolerate these effects better.
> Respectfully,

Keeping the canopy closed and latched all the time seems to help.

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Eric Greenwell
Washington State
USA