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Re: [PSUBS-MAILIST] Hookah Sub (First Try)

Sean

Thanks for the ....hmmm help?  Did you even look at the plans?

Doug Jackson

In a message dated 10/6/02 8:58:17 PM US Mountain Standard Time, sts@telus.net writes:


--Original Message Text---
From: DJACKSON99@aol.com
Date: Sun, 6 Oct 2002 21:36:26 EDT

Hi all

I am trying to design a low cost
I will defer this one to the experienced sub builders here
easy to construct,
as above
2-person dry ambient submersible for shallow lakes (60 ft). Visibility is poor so speed is not important.
On the contrary, speed is of particular importance in low visibility environments, both for collision avoidance and depth control above the bottom.
Materials must be common and not special ordered.
What do you mean by "common"? It is unlikely that you will find everything you need for a project of this nature at Home Depot.
It must be able to be constructed using only hand tools and a welder.
Defer to experienced builders.
I want to be able to exit the sub while it's down for dives. The cabin cannot flood (much) when I exit to dive,
When a diver exits, the associated volume must be compensated somehow -- either by a rise in water level, or by the addition of gas to the dry space to drive the interface down to the desired level.
and I want a second egress that allows me to stay relatively dry.
Not entirely sure what you mean here.
It also has to weight less that 1 ton so its easy to tow, launch and recover.
Unlikely. 1 ton is 2000 pounds. The (presumably fresh?) water displaced by your sub weighs 62.4 pounds per cubic foot. This displacement needs to be offset by weight to make the vehicle neutral in the water. Even assuming a physically impossible construction material which had no solid volume, this would only leave you with 32 cubic feet of vehicle space to work with. Good luck fitting two persons with dive gear into 32 cubic feet.
The primary air supply will be 3 air lines coming down from the surface where my towed hookah system will be following along. One of the line will be used for cabin air and ballast contorl the other 2 will have regulators and enter the sub through the dive hatch.
What exactly are you trying to accomplish here? Why would you have hoses entering the sub through the hatch (wouldn't this preclude closing the hatch)? If you have a low pressure compressor running topside, isn't that tended? I wouldn't depend on that as my sole source of breathing gas or ballast gas. What happens if the compressor quits?
Hookah means I can exit the sub without a BCD or scuba tank and very little weight. The hatch can therefore be relatively small.
No. Hookah means that the gas is surface supplied, typically from a low pressure compressor. Diving on surface supply does not alleviate the requirement for carrying a bailout bottle, to be used in the event of a main supply failure. Depending on the size of your bailout bottle, you may need buoyancy compensation to stay neutral as the gas in that bottle is consumed. This is especially critical if you incur a decompression obligation, as you need to hold stop depths.
Maximum dive time! is 3 hours, and then the hookah on the surface runs out of gas.
If you plan on doing three hour dives at 60 feet, you will have a decompression obligation that needs to be planned for when sizing a bailout -- not insignificant.
You can see my 1st design "H1" at http://members.cox.net/djackson99/sub/Sub_H1.htm

I would love to see other designs that meet some of these requirements and I welcome any suggestions from the group.

Thanks!
Doug Jackson

Doug, since you are contemplating diving here, I assume that you are dive certified. I think it may be a good idea to go back and re-read the physics chapters in your training materials.

-Sean