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Re: [PSUBS-MAILIST] Ambient Death Trap

Hi Alex, Greg.

Can you make a latch that opens even when the hatch is being pulled up? Maybe
some kind of emergency screw thing that you can screw in and push the latch
open with.

Yes you could do something like that. Herve calculates the pressure on the
haches of his ambients & ensures that his locking mechanisms will be sufficient for the purpose.
I'm building a small ambient as a prototype for a 1 atm & had bought latches similar to what
Doug used, latching over a hook. With a dome, I'd still have about 50 kilos of lift once partly
open, & then need to lift the latch off the hook.
I realized that I could run into problems with this after Carsten's post on sub escapes.
Alan
----- Original Message ----- From: "Alex" <spm2@nomad.ignorelist.com> 
To: <personal_submersibles@psubs.org>
Sent: Monday, September 12, 2011 12:17 PM
Subject: Re: [PSUBS-MAILIST] Ambient Death Trap



Can you make a latch that opens even when the hatch is being pulled up? Maybe
some kind of emergency screw thing that you can screw in and push the latch
open with.


On 11-Sep-2011 Alan James wrote:

If the sub had 1000 liters of cabin space & was at 100ft the
air would compress to 1/4 & give 250kg lift. But as you say
at 33ft there would be 500kg lift.
I may be wrong, but if the sub had a 4ft diameter hull & at 33ft you
equalized the hull,
the water level inside would be half way up & the pressure inside would be
the same as the
sea water pressure at that corresponding height in the water column outside.
The hatch two feet above would see a 1psi pressure above it's surrounding
water.
So multiply the square inch area of the hatch to get the pressure on it.
Regards Alan
----- Original Message ----- From: Hugh Fulton 
  To: personal_submersibles@psubs.org
  Sent: Sunday, September 11, 2011 10:13 AM
  Subject: RE: [PSUBS-MAILIST] Ambient Death Trap


  How does Carsten get to ¼ ton?  That is 250 litres.  Is that correct?
Wouldn't it depend on depth as to how much air you have in
the sub.  The shallower, the more air, the more lift.  It should only be the
projected area of the dome seal to the water level plus
the dome volume minus the dome weight.  I am not disputing Carsten's figures
as he mentions water level but just asking if there is
any agreement on how it is calculated ?  The rule of unlocking before
flooding is the most important.  As Alan says an Ambient would
pose a problem.   Hugh.



  From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Alan James
  Sent: Sunday, 11 September 2011 7:39 a.m.
  To: personal_submersibles@psubs.org
  Subject: [PSUBS-MAILIST] Ambient Death Trap



  After Carsten's posts on his submarine escape practice it occurred to me
that

  it would be very difficult to escape from an ambient submarine.

  >>>  First you have 30 Liters air in the dome create a lot of lift. And if
you flood the boat you have a overpressure in the sub
(distance of the compressed air  from the inside water level to the hatch
seal) which create also a hell of lift to the dome
latches - about a quader of a ton..
  At the end you can not open the dome.

  Rule : ALWAYS unlock the dome you want to exit before you flood the sub..

  In an Ambient sub the pressure inside is the same as the water pressure
outside at a certain point in the water column.

  So if you set your ambient equalization system half way up your hull,
everything above that point would see internal pressure.

  To visualize the pressure, imagine suspending your submarine upside down &
filling it half way with water. That water pressure

  on the hatch would be the same as the air pressure on the hatch in an
ambient sub.

  There is no opportunity to unlock the dome before you flood the sub as in a
1atm.

  Maybe a screw down type hatch closure would work. Perhaps an outlet valve
at the top of the hull to release the pressure to the

  dome level, to reduce a bit of pressure on the hatch.

  Any thoughts, comments?

  Regards Alan



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--
Mailed on 11-Sep-2011.



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