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Re: [PSUBS-MAILIST] Thought experiment



Vance,

One of the design texts I've been reading, in explaining the basics of buoyancy control via ballast, casually mentions seawater as the most "convenient" source. Hmmm.......most "convenient" source! Your reply here, drives this home.

Peter Madsen said something recently about a working man being "smart" in building a psub with limited resources. That textbook, Peters statement and, your reply.....has me looking at CBUG in a much different light! Damn that was one clever teenager! And a bit ballsy too I might add to ride that thing to 600'!

I left the control surfaces out of my response because, I was including them (by default) in the discussion about the glider, my fault for not being more clear about that.

The shot, because I thought Phillip wanted to dispense with HP air to come back up from down deep. Here, I was just modeling the Trieste, NR-1 and Alvin's solid weights, all high dollar / workload systems as you said.

Thanks Vance, the simplicity re-direct is always appreciated.

Joe






From: vbra676539@aol.com
Reply-To: personal_submersibles@psubs.org
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Thought experiment
Date: Thu, 19 Jul 2007 19:05:01 -0400

Joe, What about control surfaces? Like a glider, it seems that some kind of wing would be necessary, and if you've got one of those, then you might as well be able to tilt it for control. And the same for a rudder.?Fine buoyancy control is all well and good for hovering in a?powered boat,?although mostly unnecessary, I've found. However, the gravity powered sub is going to need a little guidance to extend the glide path, control heading changes and avoid the occasional pod of humming whales, yes??You've done away with thrusters for primary motive force, but in fact, you'll still have moving water to contend with. It looks to me that control surfaces would be even more important in this application. As for?dropping shot, I want?you to have a quick look at your bathtub and think about loading that much rusty buckshot into your tanks for every dive. Yoikes!!! I'd say external hard tanks mounted fore and aft and overboard pumps or compensated HP air (much faster trim changes)?mi! ght be better in the long run. And cheaper. Flood the tanks and the boat gains weight?without changing displacement and down you go. Use a moveable weight for pitch change, flood heavy, and OFF you go!!!?Better pack a lunch, though. It's going to take a while.?Vance?


-----Original Message-----
From: Joseph Perkel <joeperkel@hotmail.com>
To: personal_submersibles@psubs.org
Sent: Thu, 19 Jul 2007 5:08 pm
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. 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.?
?
to reply to any questions.?
?









??






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