Re: Pressure Testing

[shawl@torchlake.com (Jonathan Shawl)]

Hi Paul,
I didn't want to take this one on because there is no nice way to say this, It won't work!
Sorry but, it sounds like you need to go back to you basic physics and math then work your way up to hull stress calculations. I could calculate a hull for you, but if you want a sub you need to understand it and do the calculations for
yourself. Then have a engineer check your calculations. Then build. After that is done, pressure testing the entire sub is the only way to load the hull for a test that has any practical meaning.
If I tested my sub the way you outlined, it would probably hold up to a few thousand pounds on only 1 sq. in of the hull and that would give you the wrong results. According to my calculations, my sub can safely hold up to about 75 psi
per sq. in max. (don't quote me on that figure it's been a long time) safe water pressure, but when I stand on it in one spot that is way over that amount. The only way to shop test a sub is to seal it in a big pressure vessel and fill it
with water then bring up the pressure. I took my sub to the lake and with a line attached lowered it (unmanned) to the bottom 140' below, being careful not to let the line get tangled around me or the boat in case of an implosion. No
shortcuts here!
I hope this helps, sorry if it hurt.
Jon Shawl

Paul Julius wrote:

> Suppose that one wants to test their pressure hull.  One has the option of sending it down, unmanned, for safety.  How about testing in the shop?  What does everyone think of the following?
>
> At 100 feet we know that we are encountering about 50 PSI.  Make a block, one inch by one inch, then balance 50 pounds on top of it while resting the block on random spots on the pressure hull.  If the hull holds up, then ok, move on.
>
> Is there a better way to "shop test" a design?
>
> Paul