Re: variable ballast

[shawl@torchlake.com (Jonathan Shawl)]

Hi Vance, and all,
    I don't plan on diving past 100' with my current home built propane tank sub
(no ribs). So my VB system I have now works good down to that depth. I have 2
external large HP air storage tanks filled with clean air at a scuba shop. If I
had a internal leak or had to use air to equalize the hull to get out, I want
clean air. I get about 20+ dives on a air fill up, depending on depth and how
much I waste, that's about 2 bucks max. per dive cycle for air. Much cheaper than
a short air plane ride (right Gary). I have an internal oxygen regulator set to
120. They are very reliable and I haven't had to rebuild it yet. If I was going
deeper then I can see the need for more pressure, maybe. But 120 over ambient
seems like a lot of excess pressure. Especially if you want to take on water,
that is a lot of air to vent. I find that even 10 to 20 psi over ambient is
plenty for a fast blow with a 1.25 " water valve. At 120 psi over ambient, I
could empty the full 5 gallons in about 2 seconds if I wanted to. I think I like
the total control I have with a big water valve and lower pressures. Vance, what
size is your VB water valve? Also I am wondering if everyone has or plans to have
a 2" through hull valve, in case you want to get a drink of water. :-) But
seriously now, so you can equalize the pressure to get the hatch open in the
worst case, and you have to abandon ship. Other wise without it you may be
building a sealed steel casket.
Just thought I would bring that up since I have not seen any discussion about
that safety feature.
Jon

VBra676539@aol.com wrote:

> Jon,
>         Sounds similar.  My tank is external and I use scuba 1st stage
> regulators to hook them up, set up toward their maximum pressure (max is
> usually about 140-150 lbs/I use 120ish).  This keeps the system over ambient
> rather than some pre-set level.  One of the K-boat problems was slow to no
> air at maximum depth.  158 psi at 350 feet and the first stage reducer
> mounted internally, which is what George calls for, gets maxed out at max
> depth.  I moved the bottles outside, plumbed them through to a block
> manifold, and supply MBT and VBT as well as a BIBBS port from a panel inside.
>  It works pretty well, but the external 1st stages need watching, have to be
> rebuilt every year, and need spares in case of a failure.
> Regards,
> Vance