It was a 1500 Kaymont balloon.

Knowing the pressure differential is extremely low. When I tested the ping pong ball, I know it leaked badly. The texture of the ball just would not give a good seal.

I went with the silicone on both the "O" ring and the ball.

I also went with a pressure of the spring, Actually a spring I just could not find a spring suitable.  So I used a left over strip of balloon latex, attached to the ball and to a acrylic shaft.

The shaft was rotated to tighten the tension on the ball and seal.

I made it as loose as possible,, just enough to make the seal, and I mean barely!

I was worried that motion would even break the seal. It was that slight.

Even as light as that was,  it was not light enough, the flight still had a standard flight profile with rise to burst altitude, and did still pop.

Joe WB9SBD

On 7/21/2020 3:41 PM, Hank Riley via groups.io wrote:

Joe, please tell us more.  

Latex or other envelope?  How did it work out for you?  Any special reason for trying this valve method out?  What altitude was reached?   How long did it remain in the air?

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On Sunday, July 19, 2020, 09:06:33 AM EDT, Joe wrote:

I did that once. But the ping pong ball surface is too textured and does not make a bubble tight seal. I did a silicone ball and o ring.