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Joe,
My research into this tells me
this:
Dry weight of sub = Displacement
= Neutral bouyancy.
Ballast tanks allow the sub to be positively
bouyant by purging the water out. Positive bouyancy = float = % of sub
ABOVE the water line = freeboard.
Basically, if your sub's dry weight is
10,000 lbs then the displacement must also = 10,000 lbs if you want the thing to
sink (which is the whole idea behind a sub). If the dry weight is less
than the displacement, it will float.
In your calculations, add up all those
things that will displace water. Eg. Pressure hull, tower, battery
pods, etc. Do not add the volume of your ballast tanks as they will not
displace water once they are filled. For my design, that is exactly what I
have done. I have come up with a displacement of 6,000 lbs which means, my
entire sub must weigh 6,000 lbs if I expect it to sink. If I make all my
weight calculations and it comes out a little light, I will simply add weight to
the keel. If it comes out a little heavy, that's more of a problem as I
will have to figure out a way to lighten it up. Perhaps I could drop 20lbs
myself :)
Not sure if this answers your
question.
----- Original Message -----
Sent: Saturday, November 12, 2005 12:57
PM
Subject: [PSUBS-MAILIST] Variable ballast
calculations
Would some one be please be kind enough
to look this over for me? If I were to be correct with these numbers it would
mean some advancement in grasping of the basics.
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
Cubic feet of ballast tanks required = 291 cf required to reach
theoretical neutral buoyancy.
Does this appear viable?
Thanks
Joe
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