Jay,
Thanks for confirming that for me. I was interested to know if I might be on the right path.
So make them very strong, check.
Your resident properly reinforced pipe dreamer ;)'
Regards,
Szybowski
From: bottomgun@mindspring.com
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] Upward Buoyant Pressures on Ambient Interior Surfaces
Date: Thu, 4 Sep 2008 19:59:14 -0400
Brent,
Your port attachment has to be very strong. If it should pop out from the interior pressure, there will be a big pressure transient with a hard hitting water slug coming in at you. Seems that I remember at least one (if not more cases) from way back where there were some deaths from this type of accident.
R/Jay
Respectfully,
Jay K. Jeffries
Andros Is., Bahamas
Talk sense to a fool and he calls you foolish.
- Euripides (484 BC - 406 BC)
From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Brent Hartwig
Sent: Thursday, September 04, 2008 7:45 PM
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] Upward Buoyant Pressures on Ambient Interior Surfaces
Thanks Jay,
That makes sense to me, since the air is displacing exactly that much water, which is being kept done below the waters surface by the weight in the sub to become neutrally buoyant. So since the air in the cabin is basically very close to the surrounding water pressure, difference being the constantly added air for breathing and the slight difference in water pressure at the bottom of the sub from the top. Then we add the buoyant force on the upper surfaces. Which I was thinking would be applied to the sides as well, on a gradient scale gaining more pressure as you go towards the ceiling. Which if correct would mean it would be harder to calculate. But to be safe you could make the ceiling able to easily with stand all the buoyant pressure to a FOS of 2 or more, plus make the side equally strong.
So this would seam to mean to me, that the ceiling will have a good bit higher psi being applied to it, over the lower pressure water on the other side of the ceiling.
I had been toying with the idea of making one or more of the really amazing FRP kit car kits out there, into an ambient sub, with a view to die for, but for go the dying part. So I didn't want my windshield t pop out or brake out. I was thinking about using the commercially available automotive wind shields for the sub, and adding stronger exterior flanges to secure it. The other option was to use the glass wind screen, for a blow mold, or drape mold to form a new wind shield out of acrylic. Any thoughts.
Your resident bubble boy dreamer ;)'
Regards,
Szybowski
From: bottomgun@mindspring.com
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] Upward Buoyant Pressures on Ambient Interior Surfaces
Date: Thu, 4 Sep 2008 18:58:20 -0400
Brent,
Two things need to be sorted out in this mental exercise. How many cubic feet of air? Convert this into the weight of the equivalent volume of water…this is the force pushing up. Now have many square inches of surface (upward side) is that air applied to? Divide the force (equivalent pounds of water) by this surface area and you have the PSI sensed by the interior overhead. As you descend, the bubble gets smaller is no air is added, buoyancy decreases, and the applied air pressure to the top surface decreases. Water force inside and out are the same for an ambient sub.
R/Jay
Respectfully,
Jay K. Jeffries
Andros Is., Bahamas
Talk sense to a fool and he calls you foolish.
- Euripides (484 BC - 406 BC)
From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Brent Hartwig
Sent: Thursday, September 04, 2008 6:34 PM
To: PSUBSorg
Subject: [PSUBS-MAILIST] Upward Buoyant Pressures on Ambient Interior Surfaces
Upward Buoyant Pressures on Ambient Interior Surfaces
Grand Greetings SMMOM's ;)'
I've been pondering this question for some time now, when I was designing a couple if different ambient subs in my head. Doug, I believe brings up some good points below about the higher PSI inside the ambient subs being a little higher. He also made a point recently about the PSI being a little higher from the constant flow of air, coming into the cabin for breathing.
I was thinking that there is one more thing item we need to consider. That being that air is really buoyant, as we all know. So one of the main reasons that 1 ATM subs are so heavy, is that they need to counter act the buoyant forces that the air in the interior is exerting upwards. So that means to me that all the air in the ambient subs cabin is mostly pushing upward on any surface that's there. This is why I was thinking that a hatch and/or any windows and frame work can handle that amount of buoyant pressure that is trying to lift the sub, and will do so, if you release a drop weight. For some large ambient cabin spaces, I would think that pressure might be substantial. Any thought? I wouldn't be surprised if I missed some thing.
Your resident bubble dweller ;)'
Regards,
Szybowski
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] depth indicator
Date: Fri, 29 Aug 2008 09:55:57 -0400
From: djackson99@aol.com
I think the correct answer is "almost" no difference.
Take a 4 ft pipe. Cap one end and anchor the open end to the bottom of a lake so that the cap is just below the surface. Now fill the pipe completely with air. At the open end of the pipe the air pressure is equal to the water pressure and a depth indicator will read the same if it is inside or outside the pipe. But at the top of the pipe the water pressure outside the pipe is zero and the air pressure inside the pipe still indicates the pressure for 4ft of water.
So my dive computer outside the view port will indicate the depth of the view port, and inside it would indicate an additional 3+ feet, to were I release air into the surrounding water.
Best of Luck
Doug
www.submarineboat.com
-----Original Message-----
From: Jay K. Jeffries <bottomgun@mindspring.com>
To: personal_submersibles@psubs.org
Sent: Fri, 29 Aug 2008 5:01 am
Subject: RE: [PSUBS-MAILIST] depth indicator
In ambient sub senses the same pressure inside or out so there is no difference having the gage inside or out.
Talk sense to a fool and he calls you foolish.
- Euripides (484 BC - 406 BC)
Hmmmm... Not the weight of the sub. It should indicate the depth of the vent where the air is released into the surrounding water and likely a little deeper since the constant flow of air may add a few psi to the ambient cabin. Air at the top of the cabin is at the same pressure as the air at the bottom of the cabin where it is vented to the surrounding water. So it does not matter where the gauge is inside the cabin.
That also makes the air at the top of the cabin at a pressure higher than the water surrounding the top of the cabin. So a hatch in the top of an ambient sub seals naturally if it opens inward. Completely opposite to a 1ATM sub.
In my case the dive computer is going to ride along outside the forward view port. There is no room for it inside and with it outside it will automatically start logging the dive when it submerges.
So what are you thinking of building?
Doug J
www.submarineboat.com
In an ambient submarine, if one uses a dive watch type depth indicators to give an indication of how deep He is, does this display the actual depth or will it be off a little having the additional weight of the sub working on it? One of those HMMMM thoughts...
David Bartsch
Be the filmmaker you always wanted to beearn how to burn a DVD with Windows. Make your smash hit=
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