Re: [PSUBS-MAILIST] Dan, Rick, Bill, Myles, Carsten

Gentlemen.

Here is what started the trouble for me in the first place, this replica of the S-44 boat.

http://www.fastkayak.com/s44.html

When I saw this, I wondered if it would be technically feasible to build a similar fully submergible ambient design of the same materials. At first I had big ideas but reality dictates a different approach.

I am attempting to apply the scientific process to try to prove or disprove the theory. The ugly little problems of weight and buoyancy continue to plague me however, the math appears to prove at least the technical feasibility (practicality issues aside for a moment) of some combination of weight and variable displacement capability.

What most of you have, is a "real" submarine, which isn't trying to be anything else. What I am "attempting" to do, is a surface boat in submarine clothing trying to submerge (very shallow) on occasion.

The problem that I am having is that I am trying to "merge" two disciplines, (subs and boatbuilding) neither of which I am expert, into something unique using proven principles.

All of the other practicality issues of control, air systems, structures, etc, have to be addressed one at a time and proven or disproved mathematically.

I have a mental picture of what I am after, but all I can do is "sew" all of the pieces together and see what kind of monster I have come up with on paper before I would ever actually try to build anything.

All of the technical advice from this group is invaluable and much appreciated. I have a special file just for that.

Thanks

Joe

From: "Dan H." <jmachine@adelphia.net>
Reply-To: personal_submersibles@psubs.org
To: <personal_submersibles@psubs.org>
Subject: Re: [PSUBS-MAILIST] Re: Variable Ballast Calculations, Rick M
Date: Sun, 13 Nov 2005 23:20:43 -0500

Joe,

Your math is correct. If that's all you are asking us to comment on, then that's that. Your correct!

Submerged displacement    = 28,637 lbs

Minus vessel dry weight     - 10,000 lbs

Variable ballast required       18,637 lbs = 2,330 gallons of seawater in tanks

I know what I was commenting on, and I think most of the other comments and questions you were getting are; it seams that your building a really large sub and are planning to fill about 2/3 of it with water so you can get it to dive. That doesn't make a lot of sense to me. I can't see the reason you would build such a big expensive hull with such big tanks and have to control that much mass while maneuvering the sub also.

Maybe your only planning to build a small pressure hull with a big fairing for your subs appearance. If so, then your displacement is only your pressure hull and the fairing can be free flooding and not part of your displacement equation at all.

If I have it wrong, it's not the first time I've misunderstood someone. If so, please explain it to me once again.

Dan H.

----- Original Message -----

From: Joseph Perkel

To: personal_submersibles@psubs.org

Sent: Sunday, November 13, 2005 6:49 PM

Subject: [PSUBS-MAILIST] Re: Variable Ballast Calculations, Rick M

Rick,

    "the tanks they are refering to are the soft ballast tanks.

which does not effect submerged displacement"

Now I'm confused again. Just when I think I have a concept down, bang along comes a problem. It's been a long day for me, I need to take a break and review terms again later. I can't possibly do the math now, info overload!

I will review what you're trying to tell me when I have a clear mind again.

Thanks

Joe

From: "rick miller" <rickm@pegasuscontrols.com>
Reply-To: personal_submersibles@psubs.org
To: <personal_submersibles@psubs.org>
Subject: Re: [PSUBS-MAILIST] Re Variable Ballast Calculations
Date: Sun, 13 Nov 2005 15:34:22 -0800

joe

    the tanks they are refering to are the soft ballast tanks.

which does not effect submerged displacement, they effect surface displacement. soft ballast is normally free flooding

the only time they effect submerged displacement is durring emergency blow. but due to the large quantity of air require to do this and the chance of an uncontrolled accent this is not thee prefered method of operation.

    lets look at what is happening in the soft ballast tanks if you want to use them for a controlled accent , for ease of the numbers we will use an accent for 66 ft or 3 atm absolute. fixed factors accent raate is basesd upon drag and the positive displacement. we will use an accent rate of 60 ft /min and a positive displacement of 128 or 2 ft^3.

durring the first thirty three foot rise you will have to vent 1 ft^3 of air thru an oriface/ valve with a differential pressure. in most tank designs this space would be approx 1 inch allowing for a differential pressure of .03 psi ie a really shitty flow rate.

    for the next thirty three feet of rise you will need to vent off 2 cf of air , while the air density has decreased the flow is not linear based sloely on density

    so you would have to throttle the vent valves in order to made any kind of controlled accent. this could be done using control valves and a pid controller incorporated in a plc.but that waywould increase costs dramatically.

    the cheapest way to accomplise this is to use a small trim tank open at the bottom that has only the capacity to give a small quanity of positive displacement. as the air in it expands it will just blow out the bottom. this method will using more air the a sealed trim tank if you are planing multiple accents and decents durring a dive but eliminates the need of a high preesure tank and control system for the water intake valve. although it would require a crew wiegh in to establish basic trim.

    a standard scuba tank is 80 cf a 3000 psi/200 bar. assuming a full tank at 1000 ft or 500 psi abient pressure. you will have a reserve lift capacity of

tanks size = .4 cf

volume air 80 cf air compressed to five hundred pai ==2.35 cf

an available air supply of 1.95 cf or 125 lbs of lift.

the formula is p1v1=p2v2

size of tank

80*14.7=3000x

80*14.7/3000=x

.392= x

3000*.4=500*x

(3000*.4)/500=x

x=2.4 cf total airremember the air that will stay in the scuba tank

2.4-.4 = 2 cf of available air.

rick miller

Original Message -----

From: Joseph Perkel

To: personal_submersibles@psubs.org

Sent: Sunday, November 13, 2005 1:28 PM

Subject: Re: [PSUBS-MAILIST] Re Variable Ballast Calculations

Rick,

I had read in the NAVPERS manual for fleet boats, that a submarine does precisely that to submerge, (reduce displacement by flooding the tanks).

As for practicality, well this is all just math for now. Incidentally, I am not using terms correctly in these posts, ie hard, variable, soft ballast.

Thanks

Joe

From: "rick miller" <rickm@pegasuscontrols.com>
Reply-To: personal_submersibles@psubs.org
To: <personal_submersibles@psubs.org>
Subject: Re: [PSUBS-MAILIST] Re Variable Ballast Calculations
Date: Sun, 13 Nov 2005 12:16:22 -0800

joe

    you dont reduce displacement by adding water. displacement = the total volume of all non free flooding spaces.

the introduction of large internal ballast tanks creates a sinificant engineering problem and a possible piont of flooding for the passenger spaces. most hard tanks are hard to inspect for corrosion. not to try to rain on your parade, the kiss pricipal seems to be the way to go here, if you ever want to get in the water.

rick m

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