Re: [PSUBS-MAILIST] Ambient pressure sub hardware

[SFreihof@aol.com]

Doug;

I also plan on hatches top and bottom.  Top, to allow ingress/egress while surfaced, and the bottom hatch to allow ingress/egress submerged.  Both hatches open outward since I don't have room in the cabin to permit hatch incursion.  The bigger the cabin, the more buoyancy, thus the more weight needed, so minimize volume to minimize weight.  I want my sub as light as possible for easier handling/transport.

I don't understand why you say you have to flood the sub to open the top hatch???  Put a valve on your purge pipe.  When you surface, close the purge and open the hatch.  You float like a boat because water can't get in, no?

My concern then is freeboard... how high is the hatch above the waterline?  Too little freeboard and there is a danger of swamping even in small waves or boat wakes... so maximize freeboard.

Stan
2 man Ambient Dry
Ft. Lauderdale

In a message dated 12/6/2002 2:59:02 AM Eastern Standard Time, DJACKSON99 writes:

> Stan 
> 
> Yes I plan on using an AirLine hookah system for the air supply. Very good point I'll have a check valve in the supply line.  I though about the check valve in the purge line but decided I would rather start flooding than putting crushing preasure on a flat acrylic view port. 
> 
> Here is the current design: 
> http://www.djackson99.netfirms.com/sub/Sub_H4_files/index.html 
> 
> This all comes back to my on going major concern about the hatches.  I plan to have bottom dive hatch that opens outward.  That one I am not too concerned about.  But I also want a top hatch so I can stay dry in cold water.  If the hatch opened inward it would be easier to build and less likely to leak but it would require us to wait for the cabin to completely flood before we could open it.  My thinking is that maybe that is fine, because opening it outward for an emergency escape before the cabin was flooded could really knock us about, and I don't want to drop the spare air cylinder.   
> 
> Perhaps the bottom hatch could be build to swing inward too.  It would require some squirming around in order to let it swing inward. But that would let us open the bottom hatch and equalize without completely flooding in order to make our escape. 
> 
> Other Ideas? 
> 
> Where can is see your design?  I have not seen many Ambient Dry 
> designs. 
> 
> Thanks! 
> Doug Jackson 
> Tulsa, Oklahoma 
> 
> 
> 
> In a message dated 12/5/02 9:36:37 PM Central Standard Time, SFreihof@aol.com writes: 
> 
> 
> If you are planning a surface supply, I see no reason why this wouldn't suffice... but there is a caveat....(warning!!!) 
> 
> The original hard hat divers were in danger of a failure in surface supply pressure, and it sometimes happened.  Loss of supply meant that suddenly the hard hat pressure dropped to 1 atm (surface) pressure, and the diver was still at ambient.  Many divers were buried in their helmet from the resulting compression. 
> 
> Eventually, a one way valve was incorporated so that loss of surface supply did not result in a loss of pressure in the hard hat.  Make sure this is also true in your design, or your hull could flood if you lose supply pressure, and then the sub quickly becomes negatively buoyant... like a rock.... 
> and if you try to close a valve on the pipe sticking out the bottom to stop the flooding, then you risk implosion due to pressure differential beyond design limits. 
> 
> Stan 
> 2 man Ambient Dry 
> Ft. Lauderdale 
> 
> In a message dated 12/5/02 5:38:58 PM Eastern Standard Time, DJACKSON99@aol.com writes: 
> 
> 
> I was just planning on putting a short piece of pipe sticking out the bottom of the hull. When water is coming in, then I'm descending too fast, otherwise its blowing bubbles out 
> the pipe.  Why would I need a relief valve or regulator? 
> 
> Doug