Re: fresh/salt water bouyancy difference

[Mike Young <tvcmikey@yahoo.com>]

Mike here!
Another story was when a Nuke went into the shipyard
and they stripped about 40 layers of lead-based paint,
put back 2 coats of primer and 1 coat of new paint, took it out and it
too wouldn't sink. They ended up adding 10,000 pounds of ballast
inside to make it neutrally bouyant. i.e. 40 coats of lead-based =
10,000
pounds




---Ray Keefer <Ray.Keefer@eng.Sun.COM> wrote:
>
> Hi,
> 
> There is a story I once heard. A Captain of a nuclear Los Angelas
class
> attack submarine took his boat out after an overhaul at Pearl Harbor.
> 
> He took it out clear of Pearl, out to the safe zone to dive and
proceeded
> to submerge. Try as he could. Flood all his tanks: ballast, trim,
bilge, 
> waste ... he couldn't get the boat submerged.
> 
> After a couple of hours of futile attempts to submerge he had to
take his
> boat back to Pearl. Once back in port it was discovered that the
overhaul
> crews had removed the margin ballast.
> 
> Big military submarines are intentionally designed to naturally a bit
> positively bouyant. This is done for a few reasons. 
> 
> First it's easier to add weight to a submarine then to add bouyancy,
just add
> lead bars. 
> 
> Second, if in the future you get bigger and better weapons the
chances are
> they are heavier then the current ones. In which case you just add
less margin
> ballast instead of having to add additional bouyancy in some way.
> 
> The submarine in this story couldn't get under because it was too
bouyant.
> 
> From the book "Concept in Submrine Design" there are three types of
ballast:
> 
> Ballast - pgs. 40 -44
> 	Permanent-brings equity of weight and buoyancy; enables longitudinal 
> 		positions of center of gravity and center of buoyancy to be 
> 		brought into coincidence;  brings vertical position of center of
> 		gravity enough below center of buoyancy to give adequate 
> 		separation, for hydrostatic stability
> 
> 	Margin - to make an allowance for weight growth during design and 
> 		building and future life
> 
> 	Variable - carried in sea water; used to make continuous corrections 
> 		to achieve neutral buoyancy
> 
> Regards,
> Ray
> 
> 

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