[Date Prev][Date Next]
[Chronological]
[Thread]
[Top]
Re: [PSUBS-MAILIST] Weighing
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.
GB
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.