RE: [PSUBS-MAILIST] Thought experiment

Alec,

In a word...absolutely! I'm not advocating shot ballast over HP air and, it did not occur to me but,... yes I would be lynched if I dumped shot here!

I was using Phillips original post as an exercise in what I might do if I were to build such a powerless glider. In hindsight and, after Vance's reply it's apparent that the way to do that would be to copy CBUG as it originally was done, (really very clever).

Still though, someone mentioned that Karl eventually added thrusters. I suppose those mid-water transits would be like flying in clouds, novel at first but, not much to see.

As for the ball valves, every time I think about overcomplicating the valve system, those silly little valves get in the way. :)

Joe

From: "Smyth, Alec" <Alec.Smyth@compuware.com>
Reply-To: personal_submersibles@psubs.org
To: <personal_submersibles@psubs.org>
Subject: RE: [PSUBS-MAILIST] Thought experiment
Date: Fri, 20 Jul 2007 12:03:30 -0400

Hi Joe,

Don't you think using HP air is actually far more reliable than anything electromechanical? It's easy to install redundant, independent systems, and ball valves are so straight forward it's hard to see how they can fail. Plus, a conventional drop-weight can be used as further backup, in case say your MBTs were damaged in a collision. If you were to install say 3 SCUBA tanks with 3 regulators, 3 separate lines, and 3 ball valves, I really can't imagine all of them failing.

As I recall, Trieste actually had considerable difficulties with the shot method, and only shot from a particular supplier worked. Other suppliers' material tended to jam in the hopper nozzle. Plus, if a shot powered sub were used in some places such as over coral reefs, it wouldn't be too kind to the environment to be jetissoning shot over a delicate bottom. Particularly lead shot, which is toxic.

cheers,

Alec

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From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Joseph Perkel
Sent: Thursday, July 19, 2007 5:09 PM
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] Thought experiment

Phillip,

Sorry for the delayed response but, I had to think about the question and, take a peek at C-BUG again. I find the question itself interesting because fine buoyancy control, is of particular interest to me, (although by different methods). So this is an exercise in basic buoyancy control for me as well.

In our application, we have buoyancy and thrust as our 2 ways of changing depth....correct? For the glider method,...... eliminate thrust.

I'm not quite clear on the "suspending" piston idea but, in thinking about this "non-powered" mode of changing depth, we're left only with manipulation of buoyancy...correct?

This had me thinking about , what manner of "ballast control", would I personally feel comfortable with in this application and,... like you,.... I feel air is unattractive for the ascent phase as..."failure is not an option".

So for my "glider", in the negative buoyancy phase, descent would be initiated from a positive buoyancy condition on the surface by, standard venting of soft tanks. The positive buoyancy ascent phase, would be by releasing lead shot via some type of failsafe release mechanism, (electromechanical).

Hope to be of some help and, thanks for the mind bender!

Joe

From:  Philip Ridenauer <akula151@yahoo.com>
Reply-To:  personal_submersibles@psubs.org
To:  personal_submersibles@psubs.org
Subject:  [PSUBS-MAILIST] Thought experiment
Date:  Sun, 15 Jul 2007 13:47:00 -0700 (PDT)





I've been running a thought experiment in my head for an ambient dry glider (though I suppose a 1atm sub could do the same). The idea is to have
the sub ballasted negatively and use gravity as the propulsion source. At max depth (depending upon how much pressure the pilot was willing to risk/withstand) enough ballast is expelled to provide positive bouyancy. The ballast taken on and expelled should be forward of the CG to provide nose down attitude at neg. bouyancy and nose up at pos.

Query: is there a means of expelling ballast water mechanically so that one does not have to carry an inordinate amount of compressed air to achieve this effect?

I have an idea for a suspended weight acting as a piston but don't know if this is feasible.

Just toying with an idea.

PR

ps My computer and server are sloooow, so I don't ck my email every day. It might take me a while
to reply to any questions.




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