Hi,

Does anyone know where and why the seemingly bizarre custom of throwing
a bucket of water on a newly soloed glider originated?

German custom is different:

The new solo is given a bunch of "flowers" picked from around the
airfield. Usually the ones with the most thorns are selected. Then they
are given a good slap on the bottom from everyone present. That
supposedly is for calibration.

Found a video of such a ceremony at
http://www.youtube.com/watch?v=mZSmBddTo_M. Starts at 5:30.

Beer is also usually involved. But we get a lot of very young solo
pilots that a) are not allowed to participate and b) can't afford to pay
for everyone.

Ciao, MM