Re: [PSUBS-MAILIST] Center of gravity Vs. Center of Bouyancy

[Ed Greany <crest25@attglobal.net>]

Hi Doug,

Honestly, I don't even remember Sub School particulars. I didn't get
serious until I got OUT of Sub School and on a boat when I really began
to understand and WANT to understand what boats were all about. Sub
School to me was just another Boot Camp with it rigidity and rules and
etc. We also could not take notes and keep them since everything was
classified. So,

my experience on the boat was limited to a "boomer". Of course, our
ballast tanks were 12 in number (3 port fwd, 3 port aft, 3 stbd fwd, 3
stbd aft) but were not isolated from their port/stbd partners. In other
words, ballast tank 1A on the stbd side forward had a hole at the top
and one at the bottom with ballast tank 1B. So you could actually say,
there were 6 ballast tanks and each was split port and starboard but
they went all the way around from keel to keel instead of saddle tanks
which infer only partially around the bull.

Subbing on a SSBN boat that weighs over 7,000 tons submerged is going to
be considerably more different than say the Tang with only 2400 tons
submerged and your premise of a hazard of a broadside wave is pretty
much not even a consideration. I liken it to a sailboat where a strong
wind can blow the sail over and actualy capsize the boat. The sail on
the sub is much smaller in comparison to the hull and weight
differential is no where near the same proportion.

Ah, yes, the Trigger trainer. I remember it well. Let's see, "Harder,
Darter, Trigger 'n Trout; always in and never out!" used to be the
saying. The actual Trigger was the first boat I took a dive on.

As for the theory of blowing entirely, that was routine anyway but I
can't disagree with the physics you present concerning the CG and CB
cross. I'll leave that up to the engineers. That is beyond the scope of
my "need to know."  ;) I'm not sure it necessary has to do with ballast
tank design however. As long as the ballast tank blows inside to the top
of the tank forcing water out the bottom, I don't think there is any
problem with a wave. You might incur a roll but not a threatening
situation unless you are in the surf.

By the way, out guys raising havoc with the Diving Officer didn't have
to go thru Control since Control was on the upper deck and we were in
the Middle Deck so no one was the wiser. Lots different on a boat 425'
vs 300' long.

"Straight board; even bubble".

Ed

Doug Niessen wrote:
> 
> Ed,
> 
> If I remember correctly from sub school (1964), doesn't the center of
> buoyancy move up and down the vertical axis of the boat as the ballast
> tanks are blown or flooded? Seems that in the Trigger trainer they
> stressed the point of quickly and completely blowing the ballast tanks
> during surfacing. There is a point when the center of buoyancy and CG
> cross during diving and surfacing and at that point a big wave broadside
> to the sail could capsize the boat.
> 
> This may not be a problem for small subs if the ballast tanks don't
> encompass the hull.
> 
> Or..... I may be making all this up and am completely wrong.
> 
> We have done the same thing, moving ten or fifteen guys for to aft to
> play with a fresh diving officer. The giveaway is these guys streaming
> through control like a line of ants.
> 
> Cheers,
> Doug,   K6STS
> ex-STS2 (SS)