Re: Ballast Bladders

[Rick Lucertini <empiricus@sprint.ca>]

Marcel Michaud wrote:

> [snip]    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.

Salut, Marcel, ca va?

I like the idea of wrapping them in a pipe.  Make sure that, after deployment, your hatch is well
above the surface, so watch where you place your attachment points.

The shape of your sub, combined with the placement of the bags, will determine the attitude of the sub
on its way to the surface, if you inflate them at depth.

My suggestion: drop hard ballast in small amounts from the forward end of the sub to establish a
bow-up attitude.  As the bow lifts off the bottom (or whatever) drop some hard ballast from just aft
of amidships to help it just enough to begin your ascent.  Only when the sub reaches the surface
should the soft bags be deployed.

Something that comes up for commercial divers is losing air from lift bags due to a shift of the bag
in an out-of-control ascent.  As the bag rises, it loses the air and the heavy object crashes back to
the bottom.  The same thing could happen with a sub if it has the bottom of the bladder or ambient
tanks open to the surrounding water.

So, be stable at the surface, then deploy the bags.  Another advantage to this technique is that you
don't need any compressed air to do this.  At the surface, all you would need is a simple pump to draw
air from a snorkel mast extending form the cockpit or fairwater.

A prochaine . . .   :-)

Rick


--
Rick Lucertini
empiricus@sprint.ca
(Vancouver, Canada)

"I resent that - I don't deny it, I just resent it!"
  --- Groucho Marx ---