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Re: [PSUBS-MAILIST] Weighing
On Mon, 05 Aug 2002 19:25:00 -0700
"Gary R. Boucher" <protek@shreve.net> wrote:
> If you can find the CM of each part or component, yes, you can simply treat
> them as points of mass. This is still with the exception of the moment of
> inertia I mentioned. And it does not matter what angle of roll, pitch, or
> yaw. These don't change the CM. If you locate the CM of your sub and
> stand it on its end, or its side or at any angle, the CM is still at the
> same location. Same with CB under water. Angle does not change this. As
> for the batteries in the box, you can have five points for 5 batteries, or
> you can just locate the point in the middle battery with five times the
> weight (assuming they are grouped together). Does not matter. There is
> even a way to find the vertical center of mass of a battery if it that
> critical.
This is pretty good news then, point mass calculations
are useful. This makes the computer program easier to
write.
Ian.
> At 05:06 PM 8/5/2002, you wrote:
> >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.
>
>
--
The moon ate the sun on Monday and it was an awsome sight to see.