Max,

Most gliders of that generation use the Wortmann FX 67 airfoil, which has
degraded performance when wet.
Some examples are :
Kestrel, DG-400, Pik-20, Nimbus 2, Lak-12, LS-3, Janus, HP-18, Jantar 2B

Apparently some are worse than others, I suppose this is due to the fact
that some use this profile on the wing roots only, with another profile
towards the wingtips (these being "better" or more "tolerant"), while some
use only the FX-67 only. But it could be something else.

Apparently the laminar flow is disturbed very easily on this profile, so not
only water, but bugs will degrade their performance as well.

Reading Dick Johnson's flight tests, especially some from the 70s, will tell
you a little bit more about this.
If you go to this link (http://www.ssa.org/Magazines/Johnson.asp) and scroll
down, there are 3 reports about the Pik-20, very illuminating.


"Matt" wrote in message
...
do they fall out of the sky when they get wet?