Re: [PSUBS-MAILIST] Ballast volume moon Shaped

[Ray Keefer <Ray.Keefer@Sun.COM>]

Funny,

I ran numbers and got a cross section of 419.5 sq in per ballast tank. I put
my math at http://www.psubs.org/designguide/CylinderBallastTanks.jpg.

With two tanks that would be 839.0 sq in.

For 12 foot length the volume for both tanks would be: 

	V = 839.0 sq in * 12 ft * 12 in/ft = 120816 cu in = 69.9 cu ft

Water Density:

	Fresh Water     62.3164 lb/ft^3 at 20 degrees C
	Sea Water      ~64      lb/ft^3 
                        
Displacement:

	Fresh Water     62.3164 lb/ft^3 * 69.9 cu ft = 4355.9 lb
	Sea Water      ~64      lb/ft^3 * 69.9 cu ft = 4473.6 lb

So why are our numbers so different?
	
Regards,
Ray

	                     
> Date: Mon, 17 Jun 2002 13:33:06 -0700
> From: Ian Roxborough <irox@ix.netcom.com>
> To: personal_submersibles@psubs.org
> Subject: Re: [PSUBS-MAILIST] Ballast volume moon Shaped
> Content-Transfer-Encoding: 7bit
> 
> 
> Hi,
> 
> According to QCad, 
> 
> the circumference of the cross section = 53.1066 inches
> the area of the cross section = 104.457 square inches
> 
> At 12 foot long, this would ~15,000 cubic inches.
> This would give you 547 pounds of buoyancy.
> 
> I don't know for sure if the information QCad gave
> me is correct, but the cross section of the tank
> is equal to approx. one third of the cross section
> of the 20" OD cylinder.  This sounds reasonable I guess.
> 
> Ian.
> 
> 
> On Mon, 17 Jun 2002 14:36:08 -0500
> "John R. Farrington" <jrf@austin.ibm.com> wrote:
> 
> > I think the 'area' of your ballast tank is going to be roughly
> > 55.38 square inches.  Take that times 12 feet, and you 7975
> > cubic inches, which is 4.65 cubic feet for each of your ballast
> > tanks.
> > 
> > Each tank would displace roughly 300 pounds of water, giving a
> > total of 600 pounds of buoyancy when the entire tank is below
> > the surface of the water.  You'll have to also tank into account
> > the weight of your tanks as well.
> > 
> > I just 'brute-forced' these numbers on scratch paper so I could
> > be wrong.  If you're interested, I can type of the description
> > of how I came up with these numbers.  Might be a good idea to
> > get a verification from someone else with a CAD package.
> > 
> > -John
> 
> 
> -- 
> The moon ate the sun on Monday and it was an awsome sight to see.