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Re: [PSUBS-MAILIST] Weighing

On Mon, 05 Aug 2002 18:24:12 -0700
"Gary R. Boucher" <protek@shreve.net> wrote:

> One small clarification in my previous posts from a few minutes ago.  The 
> CM is always a point.  The CB is always a point, no mater what the sub is 
> doing, statically or dynamically.  It is just when other forces come into 
> play such as dive planes or propulsion, the CM may not be directly below 
> the CB because of torques or forces.  I did not intend to indicate that the 
> CM or CB change with the application of external forces and you can always 
> consider these two as points as long as nothing changes (shifting weight etc.).

I probably wasn't being too clear, when I said point mass, I was
refering to treating all the objects/components of the submarine as
point masses.  For example, treating a 12 foot long, 4 foot wide
pressure-hull as a point mass, like you said, it only works for
static drive calculations, also calculations that don't involve
pitch, yaw or roll agrees.  It would also seem like there would
inaccuracies in treating everything as a point mass while performing
surface calculations.  Also treating some items, like batteries,
as point masses seem fine, providing you are counting each battery
and not grouping them all together.

> The Moment of Inertial that I spoke about is equal to the Mass at a point 
> multiplied times the distance from he center of rotation to the mass 
> squared.  Moment of Inertia is symbolized by the letter ( I ).  Thus:
> 
> I = M x R^2

R^2, no wonder they wanted to move all the mass to the center
of their subs...

Thanks for the info,
  Ian.

-- 
The moon ate the sun on Monday and it was an awsome sight to see.