Re: [PSUBS-MAILIST] question about general design?

[TeslaTony@aol.com]

In a message dated 8/8/01 6:50:55 PM Pacific Daylight Time, 
kandd@softdisk.com writes:

> Re: [PSUBS-MAILIST] question about general design?Is my reasoning flawed?  
If 
> you have a off the shelf compressor bottle that is rated to 125psi that is 
> outside your pressure hull, it would limit your diving to depths greater 
than 
> 125psi (I don't know how many feet that is)   Otherwise, you aren't gonna 
> blow ballast at 150psi with 125psi air.  So, if the tank always has 
pressure 
> inside of it greater than the pressure outside, it ought to be happy as a 
> clam.  They way I figure it, if the outside presure is 50psi and the tank 
is 
> holding 75 psi, that's like having a tank at 25 psi with no pressure on the 
> outside.  Being a newbie, I may be all wet, if so someone please  
straighten 
> me out.   Ken Harris
>  
I don't know how much the 125psi tanks cost, but I can't see them being less 
than $75, not including compressor. SCUBA tanks, on the other hand cost 
$150-$200 for 80 cubic foot tanks (new) and $400 or so for a 120 cu/ft. tank, 
$5 for refills or about the same for a one day rental. SCUBA tanks are meant 
to go underwater and provide 3,000 psi air reliably enough for someone to 
trust their life with one down to 100 feet, something which shop compressors 
probably aren't reliable enough to do.

In short: SCUBA tanks are cheaper for how many PSI they deliver, are meant to 
go underwater and will blow your ballast faster, assuming a shop compressor 
tank can blow the tanks at all.

Now if you have the sub tethered to the surface a shop compressor just might 
be what the doctor ordered since you really don't have to worry about running 
out of air if you have gas in the engine or a proper power source for the 
electric models, but I'd probably still want to keep a tank of compressed gas 
onboard in case of emergency (a large bottle for a paintball gun might fill 
the ticket here, but I'm sure someone else will nix that idea)

Anthony