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PART TWO.......
Sorry, I lost my e-mail thing for a minute....Any way, It's not essential
to have a VBT at all, but it makes a lot of sense to include it in your sub if
you're building your own. Just how much VBT is best is another question.
Available room for the tank, and storage of enough HP air to blow it dry
are two things that come to mind right off. How many times you'd need to blow it
out on a dive would dictate how much air you'd need onboard if it was fairly
large and you expected to make adjustments while at depth. It could take a LOT
of air to blow a 40 gallon tank dry at 500 feet!
I would think that most psubbers use the VBT for fine adjustment of
buoyancy, and that is done usually at the beginning of the dive while
still shallow. Then, once the adjustment is made, the tank is valved off, and
remains that way until the dive is over and you're back up near the surface. For
that simple operation, no level gage would be required, ( although it would
still be a great convenience ) and the tank needn't be that strong.
The other options of adjusting at depth would require a much stronger tank
and more stored HP air to adjust it. I guess it depends on how you plan to use
your sub, and whether you wanted or thought you needed the extra option of
deep adjustment in buoyancy. Is it a necessity? or just a convenience. Frank
D.
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