Re: [PSUBS-MAILIST] A Solution

Sean,

So then with known values of weights, moments and arms, it would be a relatively simple affair to mathematically rule this in or out. Anecdotally...it's looking pretty good, since you can counter those high moments with low slung weight between the pontoons....if it proves necessary.

I will start work on that model when I get the sub design finalized. The CAD program will calculate volume of materials, so starting with known densities, I should be pretty damn close in the estimations.

Joe

From:  "Sean T. Stevenson" <cast55@telus.net>
Reply-To:  personal_submersibles@psubs.org
To:  personal_submersibles@psubs.org
Subject:  Re: [PSUBS-MAILIST] A Solution
Date:  Mon, 6 Nov 2006 12:38:13 -0800
>Stability is not that complicated.  Fully submerged, it just means CB must be
>above CG.  On the surface, or at any degree of partial submersion, CG can be
>above CB, provided that as your vessel rolls, CB shifts outboard so as to create
>a moment arm about the center of roll which counteracts the moment arm created
>by CG.  Imagine your vessel as having a plane amidships, which rolls with the
>vessel.  The vertical distance between the instantaneous CB (which changes due
>to hull geometry, angle of roll and how far the vessel is submerged) and this
>plane is the metacentric height, which is a measure of stability for that
>particular angle of roll.  Large metacentric heights indicate a "stiff" vessel,
>which has lots of stability but may not be quite as comfortable in a sea as a
>"soft" vessel with less (but still sufficient) stability.  A cylinder lying in
>the water has exactly zero stability since CB and CG are always in a vertical line.
>
>-Sean
>
>
>Quoting Joseph Perkel <joeperkel@hotmail.com>:
>
> >
> > Gentlemen,
> >
> > I seem to keep coming back to this particular solution, probably because as a
> > mechanical guy...I can figure out how to build this. As a pilot, I can
> > visualize CG, W&B and forces at work, but what I am not......is an engineer.
> >
> > That lack of knowledge and my desire to build a successful and uniquely
> > spectacular project, is partly the impetus to pursue Naval Architecture,....
> > but I am not there yet. I do not yet know how to calculate for surface
> > stability of floating bodies, but I do have an idea of what's required.
> >
> > the link below is in case the photo won't load
> >
> > http://www.frappr.com/?a=viewphoto&id=269116&pid=3198712&myphotos=1
> >
> > My post to Rick about width is what it is.....a guess. Would this be unstable
> > at 8.5' ???, the key is in the math. Somewhere in here is the answer to this
> > particular option. I'll let Jay speak to the sea sled option as it's beyond
> > my ability to envision it.
> >
> > Thanks to everyone for the participation, the results are self evident.
> >
> > Joe
>
>
>
>
>
>************************************************************************
>************************************************************************
>************************************************************************
>The personal submersibles mailing list complies with the US Federal
>CAN-SPAM Act of 2003.  Your email address appears in our database
>because either you, or someone you know, requested you receive messages
>from our organization.
>
>If you want to be removed from this mailing list simply click on the
>link below or send a blank email message to:
> removeme-personal_submersibles@psubs.org
>
>Removal of your email address from this mailing list occurs by an
>automated process and should be complete within five minutes of
>our server receiving your request.
>
>PSUBS.ORG
>PO Box 311
>Weare, NH  03281
>603-529-1100
>************************************************************************
>************************************************************************
>************************************************************************
>