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Re: [PSUBS-MAILIST] Hybrid for Joe? and hatch installation.

Death trap.  It would be easier to just build a one-atm boat with a 30 metre operating depth.  Or just leave it as an ambient boat.
KISS - Keep It Safe and Simple
Rick L
----- Original Message -----
From: Akins
Sent: Saturday, February 11, 2006 11:54 PM
Subject: [PSUBS-MAILIST] Hybrid for Joe? and hatch installation.

Hi Joe.
I have a couple of ideas for you.
First idea....I know that you said previously that your intent for the octopus is to use it a lot as a surface boat that will occasionally dive to shallow depths as an ambient sub.
After posting my last post about using propane tanks to create a hybrid 1 atm/ambient system, I am wondering if you could fit a small propane tank into your sub design that would allow you and
the other person to still seat in tandem. Since you plan to only dive to shallow depths anyway, this way you could operate as a 1 atm sub to perhaps 2 atm and not have to worry about dive tables.
Then if you did decide to go deeper you could do that also by the system automatically switching to ambient operation beyond 2 atm of depth. The advantage of this over you just making the octopus
strictly ambient is that if you don't plan to dive very deep most of the time anyway, it wouldn't automatically pressurize. That means you would not have to worry about the problems of accending too
fast after being down a while which can give you the bends (decompression sickness) as long as you did not go deep enough for the valves to automatically switch to ambient operation. Remember,
when operating an ambient sub your body is under the same pressurization as if your body was at that depth in the water. This is one DISADVANTAGE an ambient sub has that a 1 atm sub does not have,
because a 1 atm sub can rapidly pop to the surface without any ill effects to your body. This would afford you a margin of safety in that you would not only NOT have to worry about dive tables, but you would not have
to worry about emergency accents or unexpected accents that could injure your body if done too rapidly in an ambient sub. I thought this might be a good thing for you to consider Joe.
Second idea.
I was reading Doug Jackson's sub site at this link.... http://www.submarineboat.com/
Go to his site and look for the contents heading of "Evolution of Design". Then scroll down to just a little before the bottom of the page and you will find this paragraph.......
"5. The hatch was designed to open outward after testing in a card board mock up, but now that I can test with the real cabin, it is easy to see that opening it inward is not really a problem. And opening it inward is much easier to seal and safer, since the pressure on the hatch when submerged naturally wants to push the hatch outward.  This is a trait of ambient submarines and opposite of their 1 atm (atmosphere) cousins."
If you do decide to build the octopus to be strictly an ambient sub, you might think about if you would want to install your hatch to open inward as he has. Since an ambient sub has internal pressure that pushes outward against the interior of the sub's hatch,
Doug reasoned that the hatch would seal better when closed if designed to open inward. If you ever got stuck on the bottom and had to bail out of your sub, you would have to open your scuttle valve and use a bail out tank and wait for the water to enter your sub
and equalize the pressure so you could open the hatch inward. You would have to do this in a 1 atm sub too. The only difference would be that with the ambient sub's hatch opening inward, your internal air pressure is pushing it against its flange seal, whereas in a 1 atm sub the water pressure is pushing it the opposite way against its flange seal.
I didn't know if you had considered the differences regarding hatch installation between 1 atm and ambient systems Joe.
That is the end of my two ideas for you. But now I have a question for myself and others here. Since it is easier and safer to open an ambient hatch inward, as opposed to opening a 1 atm hatch outward, how would someone install a hatch
that would go on a 1 atm/ambient hybrid sub like I have described previously?  Sometimes you may only use the hybrid as a 1 atm sub for a given dive. Other times you may decend a bit deeper and automatically switch to ambient operation.
Which way would someone install the hatch in this situation? This one has me puzzled. Anyone have any idea?
Bill Akins.