Re: [PSUBS-MAILIST] RE: payload

[Andy Jensen <drewacard@charter.net>]

I was thinking about a VBT but I did not think of the mess just lack of compressibility
.... Yep, Ii see your point.

What do the K series use for a VBT?

Andy J.

 
---- vbra676539@aol.com wrote: 
You mean aside from the inevitable mess? What's wrong with air? Oil will give you 25% lift per volume, give or take. Air gives you pretty nigh onto 100%. Your idea will certainly work, but why bother? Vance 
 
 
-----Original Message-----
From: drewacard@charter.net
To: personal_submersibles@psubs.org
Cc: ShellyDalg@aol.com
Sent: Tue, 5 Dec 2006 10:37 AM
Subject: Re: [PSUBS-MAILIST] RE: payload


I was thinking about using an oil kept in side the sub and pumping it into an 
expandable bladder out side the sub using either an electric or hand hydraulic 
pump.

one through hull and one valve. A truck inner tube in a small thin tank open 
tank.
using water to force the oil back in.  Most hydraulic connections are rated at 
3000PSI working pressure should give me plenty of over head for 600'.

It seems to simple so what am I missing?

Andy J.



---- ShellyDalg@aol.com wrote: 
Kory. I have always thought trim tanks were to adjust trim, not compensate  
for varying loads.
Water density changes with temperature and salinity, but not very much. It  
is possible to run into a salty current or water layer and trim can be added or 
 reduced to compensate.
Sometimes subs have forward and aft trim tanks to change the angle of the  
sub while still maintaining neutral buoyancy.
Adding lead ballast before a dive, depending on load, is easier than having  
a separate, large system with associated piping and tanks which  requires 
maintenance, cost, and monitoring.
With a few dives, you know how much added weight your sub needs to  reach 
neutral, and then you adjust with weights from there for added  passengers, 
cargo, new equipment, or whatever.
Trim tanks need to be at one atmosphere, whether full or empty.
Ballast tanks are ambient. 
If your trim tank is half full and open to the sea, ( like a ballast tank  ) 
the air will compress when you get deeper, and you'll start sinking  fast.
Large, one atmosphere tanks for trim will require heavy walled tanks, fill  
valves, drain valves, pressure monitoring, and take up room and add weight  
because they're thick steel.
And you have to flush them out after every dive so they don't  corrode.
Better to have small tanks for trim and carry some lead.
Just my opinion....Frank D.



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