Udo Rumpf wrote:
Steve,
I should maybe manifold all three lines at the turtle deck that would

prevent siphoning.

Now that I think about it a bit more, it is not so much siphoning, as
simply draining. With the wing low enough that the water is up to the
level of the vent at the outboard end of the tank, and the exit point
of the vent tube from the aircraft is below the water level in the
tank, it will simply drain. I suspect there is a point in the vent
tube that goes above the water level in the tank when it is sitting
with one wing level with the ground.

I think if you just keep them above the level of the water in the tank,
it should be OK. Manifolded together, or individually. I would make
sure it is either outside the airplane or in an area that can drain, as
if you tow the ballasted glider around a corner, you will likely push
some water into the vents, even if it was level to start with.

Steve