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Re: Re: [PSUBS-MAILIST] Re: Variable Ballast Calculations, Bill

Hi Shawn.
 
Very interesting. Your ballast tank bladders remind me of something like the bladder for a surface well water tank.
 
So in your design, the bladder's air, would be emptied back into the main compressor tank and NOT back into the hull compressing
 
its atmosphere? The air from the bladders would have to be compressed to go back into the main compressor tank,
 
so would you  use a compressor to suck the air out of the bladders and then store that air in the main compressor tank?
 
Is that what you meant? Interesting idea to keep moisture out of the bladders. But why would it be important to keep moisture
 
out of the ballast tank bladders?
 
Bill.
 
 
----- Original Message -----
From: Shawn H.
Sent: Thursday, November 17, 2005 5:00 PM
Subject: Re: Re: [PSUBS-MAILIST] Re: Variable Ballast Calculations, Bill

Just jumping in here... I dont know if you guys mentioned this before, but I'm actually thinking of employing a certain type of ballast system in my design(s).  It involves the use of kevlar (or hybrid kevlar/carbon-fiber) bladders.  Basically the actual ballast tank is merely a shell to hold the bladder.  The bladder itself is connected to the inside of the pressure hull and pumped full for positive bouyancy.  In reverse, it can be emptied back into the main compressor tank, to enable negative bouyancy.  The bladder shell of course is open to the sea ventrally.
 
This system ensures the air in and out of the boat is dry and takes some of the pressure off of the shell.  If for some reason there is a valve failure you dont run the risk of getting water inside the boat unless at extreme depth and the kevlar fails.  They actually use similar systems for use in portable hyperbaric chambers.  The chambers can be collapsed to fit into a suitcase, then pressurized to whatever depth is required.
 
As well, this system is what I'll be using for all consumables (fuel, black water, grey water, fresh water, etc.)  This ensures minimum airspace inside the boat as the excess space around the bladders are filled with water.
 
Anyways, something to think about... albeit expensive.  :(
 
Shawn