In trying to decide what had caused this problem, I remember trying to
fill my tank (Smiley Bags) with a water house and having a similar
result, this helped me in my decision to fly home as I knew that these
wings are built in halves and epoxyed together. Now I fly gliders
because they have fewer things to go wrong with them. I am not a
mechanic, engineer or technician, I just enjoy flying them and as John
Sinclair says I have a slow learning curve. Needless to say, however,
I don't want this to ever happen again. I called John Sinclair to
discuss what caused it, how to avoid it again and what to do next. I
had seen many people place water tanks on the roof of their motor
homes and fill their tanks that way.....my tank was a closed system
with no vents as I am sure many are. John informed me that that
practice put too much of a head (pressure) on the water going into the
wing and that even 5 lbs. pressure is too much. I had undoubtedly
weakened the structure and that coupled with a probable air bubble
entrained in the tank and the rapid (10 kt.) climb and altitude
pressure reduction (17,000 ft.) all combined to cause the problem.

The fix: 1) Fill one wing at a time.
2) Have a relief valve in the hose coming from the
motor home, no more than 1 meter above the wing.
3) Place a vent in the water bag system in thE glider.