Proper ballast tanks are the solution (~30% reserve
buoyancy).
Some additional thoughts on lift bags:
1.
It usually takes two to maintain a level condition and cause
your hatch to be exposed at the surface.
2.
Bags need to be attached very low on the sub, especially when
looking at a PSUB the size of a K-350.
3.
Lift bags should be fully inflated at the bottom to maintain a
controlled ascent, otherwise
a.
The ascent will be under constant acceleration (i.e. continually
speeding up)
b.
When surfaced rapidly, the bags/sub may broach and the bubble is
lost resulting in the sub sinking once again (and potentially injuring the
survivors inside).
R/Jay
-----Original Message-----
From:
owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of
MerlinSub@t-online.de
Sent: Wednesday, December 02, 2009 5:18 PM
To:
personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] emergency lift
bags
To open the hatch at -1 ft seems a better solution =
drop weight.
20 ft = 6 meter depth - hatch of 2ft diameter has a area
of 0,283 m2 so at 20 ft the pressure on the hatch wil be stil 1,7 ts.
Means in even a full dry boat with just destroyd mbt you
have to flood it and destroy all the interior by saltwater..
"If you have air a to blow an lift bag - means you have
still air to blow the mbt"
Lift bag is a good thing to have - on shore in store at
the car close to the diving spot.
vbr Carsten