Schempp-Hirth water Ballast Cap vent Mod

I was working on a 300K speed triangle record out of Parowan, Utah and
had reached Richfield, some 75 miles to the North, conditions were good
and I had made the turn at Richfield airport and was at the top of a
rapid 1000 fpm average thermal at 17,000 feet when I heard or felt a
loud thud. My immediate reaction was that the water ballast had frozen
in my vertical stabilizer and blown apart. (Graham Thomson had caused
this apprehension by discussing the issue while putting anti-freeze in
his tail ballast). I moved the controls and still had control of all
surfaces and attitudes. I then looked at my right wing and saw about
a 2 foot split on the leading edge about 2 feet out. It looked as if
it were a foot wide also and I immediately dumped all water ballast and
the split reduced to no more than 1/4 inch. Stew Tittle in his LS6 and
Dale Bush in his Nimbus were close by as I announced my situation and
decision to head home. As I slowed to below 70 kts and headed home we
discussed the situation. I had reduced my performance on the computer
by 15 % and had enough altitude to make it back in my Pegasus. Dale
and Stew continued to shepherd me as I slowly made my way home. As I
arrived in the Parowan Valley and with still about 4000' over the
ground I determined to try the spoilers to see if this had any adverse
affect on the split, it didn't, I continued on to a safe landing at
Parowan and subsequent repair. Dale continued on South to the North
Rim of the Grand Canyon and return.

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.