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Re: [PSUBS-MAILIST] Thought experiment

Hi Philip, very interesting, I love the glider idea.  Just seeing Cliff Redus' sleek machine gives the idea that you might get a decent glide ratio.  I suppose Cliff could operate in glide mode too, although he'll have that prop back there adding some drag. 

My thoughts would be to look at Karl Stanley's CBUG ?? and get all the info possible.  Didn't he add electric thrusters at some point?  I'd say any boat/pilot that operates regularly with passengers has some major experiences and knowledge to relate!

VBTs are built hard to withstand the max depth of your boat.  Regarding those internal pressure changes, someone more knowledgeable could probably give you a good answer.  I guess one technique is to add air as you pump out, and so maintain the internal tank pressure.  And your pump may need that higher pressure to prevent cavitation.  This 'water in a hard tank' design seems to be the most common PSUB VBT design so there might be some value in just copying what everyone else is doing.

Another style of VBT, different from the air and water tank, is to use internal and external bladders filled with oil, connected with plumbing and a pump.  The external bladder is in a compartment open to the sea, and the internal is in your air-filled passenger compartment or other location where it doesn't affect displacement.  To descend, your pump would move oil from the external bladder to the internal, reducing your displacement.



Paul

On 7/18/07, Philip Ridenauer <akula151@yahoo.com> wrote:
Paul,
A 1atm would be much more comfortable but from an expense standpoint ambient seems to be the way to go.  Don't know exactly what type of glide ratio I could expect, (that torpedo pool toy you can get at Wal-Mart looks to be better than 2:1) but if one could obtain 5:1 then a 1ft/sec descent would yield 5ft/sec forward or abt. 3kts.
Forgive my ignorance but how does a VBT work?  If you expell water from the tank with a pump aren't you left with a vacuum which would collapse the tank?
PR