Re: [PSUBS-MAILIST] Ballast volume moon Shaped

["Captain Nemo" <vulcania@hawaii.rr.com>]

----- Original Message -----
From: "Graham K" <cryogenicz@dsl-only.net>
To: <personal_submersibles@psubs.org>
Sent: Monday, June 17, 2002 8:56 AM
Subject: RE: [PSUBS-MAILIST] Ballast volume moon Shaped


> 30" OD Cylinder hull, Yes 20" diameter clinder? Cut lengthwise so you have
> to equal sized half cylinders? One for each side.
>
> also, 12 ft long.
>
> Thanks :)


Graham,

To determine the volume of the ballast tank, we need to know the inside
diameter, not the outside diameter.  Just for drill, let's say the wall
thickness is 1/4 inch.  That gives a ballast tank cylinder I.D. of 19.5
inches.  So, by tried-and-true "Flintstone Factoring", with the tank volume
reduced by the shape of the pressure hull::

Approximately 1050.7 pounds Buoyancy Potential in both tanks combined; or
525.4 pounds per tank, with flat end caps.

When dry, these tanks will bring a section of the cabin above the waterline
that is equal to about 16.4 cubic feet of seawater; and submerge that
section at neutral buoyancy when flooded.  Keep in mind: you want to figure
in an added margin for functionality and safety, so since you already have
the hull and tanks made, adjust gross vessel weight accordingly.

Ian: it looks like you calculated for the part of the tanks taken up by the
pressure hull (one third); not the two-thirds remaining, which is what we
need.

Ray, I don't know what you did, but your numbers are way off.  (Sorry!)

John, without checking, your recently-posted numbers for each half tank
(about 15,000 cubic inches per) look about right for a 20" diameter.
Calculated on the 19.5" inside diameter (taking into consideration the wall
thickness), I make the internal volume a tad over 14,000 cubic inches per
tank.

But Graham: how is it that you're already in the steel fabrication phase and
haven't figured out the basic design math yet?

Pat