Re: Ballast Bladders

[Marcel Michaud <michaudr@telusplanet.net>]

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