Re: [PSUBS-MAILIST] newbee

["Captain Nemo" <vulcania@interpac.net>]

OK Rob,

Good attitude!  Go to my NAUTILUS MINISUB page in the PSUBS picture gallery;
at the top of the page, you will see URL's for two other sites; click on the
one for SIMPLIFIED SUB MATH.  This is an easy way to determine the basic
characteristics of your design: Volume, Displacement, Weight, Center of
Weight, Center of Buoyancy, and Longitudinal Hydrostatic Center of Gravity
(the point about which your sub will pitch when submerged).

This will enable you to draw your design on graph paper, and then basically
calculate how it's going to behave in the water.  It doesn't go into
propcalc or crush depth, but it's a good place to start.  (Works for me,
anyway.)

A sub in the water moves about three axes; pitch, roll, and yaw.  Yaw is
actually a hydrodynamic effect, and it loses significance at this point of
the design process as long as your boat is basically straight and
symmetrical.

Roll and Pitch are both hydrostatic qualities; but submarines can be
designed sufficiently top-buoyant and bottom-heavy that positive dynamic
stability in roll is automatic; so my SIMPLIFIED SUB MATH program focuses on
computing the LHCG, or pitch axis (whether the sub will sit level, or
nose-up/down in the water).

The program also goes into computing freeboard and ballast tank volume.

It's based on steel because that's what I like to work with.  I know you
said you don't like to work with steel, but there are a lot of reasons why
it's good material to build subs out of; with the right tools and a little
practice, it's a lot of fun to work with, and amazingly versatile too.

You could use the SIMPLIFIED SUB MATH concept with composites, fiberglass,
ferrocement, or any other material; all you'd need to know is how much a
certain-sized unit of it weighs, and use that variable in the calculations.

But I've gotta tell ya: the idea of making a pressure-hull-type submarine
out of wood and fiberglass lined with plaster scares the hell out of me.  My
mind keeps shouting "DEATH RIG!!! DEATH RIG!!! WARNING, WILL
ROBINSON...DANGER...DANGER!!!"  I'm not saying it can't be done; I'm just
not sure it should!  And there's one other thing: if you hope to get your
boat certified, it must have a STEEL pressure hull.

You'll also find that subs of any size and volume displace a lot of water,
and need to be heavy to compensate for the buoyancy they generate.  Steel is
nice and heavy, and that's well suited to submarines.

Anyway, steel sermon over.  Go get some graph paper, a calculator, and a
pencil or pen.  Draw your sub design, and use SIMPLIFIED SUB MATH to
calculate it's weight and balance.  That's a good place to start.

You'll notice it says something like "this is how I design a submarine".
This is not an egotistical thing; all I'm saying is this is not necessarily
THE way to design a submarine; it's just the way I do it, is all.  (This was
the method I used to calculate the specs for the NAUTILUS MINISUB: a very
ornately complex design which came out right on the money numberswise.)
Check it out, and if you think it might work for you, try your hand at
calculating the specs for some of your own designs.

Good luck with your project.

Very best regards,

Pat Regan
vulcania@interpac.net