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Re: [PSUBS-MAILIST] sub bouyancy
> -----Original Message-----
> From: HeyCLOWNeY@aol.com [mailto:HeyCLOWNeY@aol.com]
> Sent: Friday, December 14, 2001 12:42 PM
> To: Personal_Submersibles@psubs.org
> Subject: [PSUBS-MAILIST] sub bouyancy
>
> im thinking of building a sub out of a propane tank (500 gallon), it weighs
>
> 1069 pounds ( as it sits now before ribs,con tower,tanks whatever) im trying
>
> to figure out the bouyancy of a tank this size so i can calculate how much
> weight i can build on to it before i reach negative bouyancy,does anyone
> know
> the formula for figuring this problem? hahahahaha i would hope so!! thanks
> bill v
Hi bill its a very basic question :
(soory I must use metric .. hope you use US galleons..)
1.) Your propane tank has 500 gallone space inside.
2.) The weight of the (steel) shell is 1069 pounds.
The density from steel is 7,86 gr/cm3 or 7,86 t/m3
1069 pounds is in kilogramms : 1 pound equal to 0,4536 kilogram
1069 x 0,4536 = 484,9 Kilogramms or 0,4849 t steel weights.
If I divided the weight of the steel to his density
like 0,4849 t steel/ by 7,86 t/m3 I get a volume for the
stell itself of 0,0616 m3 (cubic meter) or 61,6 liters
1 galleon (US) is equal to 3,7853 Liters
If I divided 61,6 Liter/3,7853 I get 16,27 galleons
for the steel volume.
So the overall displacement of your propane tank outside
is 500 Galleons together with 16,27 Galleons and
this should be very close to 516 Galleons.
The outside volume of your tank is equal to your displacement
- complete dived in freshwater (densitiy is 1,0 t/m3)
So you have a reserve building weight in this very basic calculation
of : 516 galleons - equal to 1953 Liters ,
- equal to 1953 kilogramms (in freshwater) - 484,9 kg/shell weight
= 1468,3 kilogramms (3237 pound) (for the ribs, equipment, drop weight
etc. )
The reserve weight in seawater is higher because the density
of seawater is higher (about 1,025 t/m3).
516 galleons equal to 1953 liters x 1,025 t/m3
is still 1953 Liters but lift 2001,8 kg (in seawater).
2001,8 kg - 484,9 shell weight
= 1516,9 (3344 pound) for the ribs, equipment etc..
The differnce of this both weights
1516,9 - 1468,3 = 48,6 kg (or 107 pound) should be
onboard as lead ballast - put it in if you use
the sub in seawater and keep it out if you want to
use it in freshwater.
But please note, if you change the outside displacement
by waterproof items like hatches, sailes , battery pods etc.
you get more displacement and must recalculate the
volume / weight items.
And also if you get non waterproof items outside.
for example a freeflooding deck - than you have to add the
volume of the material itself to the displacement.
You have to save some of this weight for your
hardregulator-waterballast. But this is another long item..
A radio controlled selfdesigned and selfbuild Submarine model
is a very good way to understand the basic questions.
And a cheap way also..
best regards , Carsten