RE: Ballast Bladders

["Morrisson, Richard D" <Richard.Morrisson@PSS.Boeing.com>]

Marcel,
A suggestion.  Instead of meticulously trying to get rid of all the air in
the bladder when packing it (like a parachute), try submerging it in water
and getting rid of the bubbles while packing.  This would leave a little
water in it to keep the surfaces from sticking together when compressed and
to take up those small spaces which would otherwise be compressible pockets
of air.  The water will neither add to or subtract from your overall
bouyancy.
Dick Morrisson

> ----------
> From: 	Marcel Michaud[SMTP:michaudr@telusplanet.net]
> Sent: 	Tuesday, November 03, 1998 8:06 PM
> To: 	personal_submersibles@psubs.org
> Subject: 	Re: Ballast Bladders
> 
> Ray Keefer wrote:
> > 
> > Hi Martin,
> > 
> > > Is anyone using soft external ballast bladders for emergency ascent or
> > > surface  freeboard?
> > 
> > Yes. I always thought of using some kind of bladder or lift bag as an
> > emergancy bouyancy device. I would use soft ballast tanks for regular
> > usage. But if they get damaged like in a collision I would like to open
> a
> > valve and pop open the emergancy bouyancy bags.
> > 
> > > Unfortunately, there are some other problems,like containment of the
> > > inflated bladder,  possible bursting as you ascend, volume of blowing
> air,
> > > reliability etc.
> > >
> > 
> > I would put them in flat boxes on the upper hull. The boxes would
> protect
> > the bags from wear and tear but would open up to let the bag out.
> > 
> > The air pipe would be  located inside the bag with possible a length of
> > flexible tubing. In any cases the opening of the bag would be centered
> above
> > the air pipe. The bottom of the bag would be open. So fill it up at
> depth and
> > as we ascend the expanding air will just leak out the bottom.
> > 
> > > Any comments?
> > 
> > Always. :)
> > 
> > Regards,
> > Ray
> I am thinking of using this kind of system on my sub now under
> construction, I have included two port in the tower that would supply
> high pressure air to these emergency lift bags, these bags would be
> inside a PVC pipe mounted on the outside of the sub but inside two side
> panel that I have installed to protec the sub and piping etc. and when
> needed would be used the way you explained it. 
> 
> One problem that I can see, the bag would have to be folded in a way
> that very little or no air would be trap inside, the flexible tubing
> would have to be extended all the way inside bag and secured.
> 
> Marcel
>