[PSUBS-MAILIST] Re: sub

["Michael B. Holt" <mholt@richmond.edu>]

Lew Clayman wrote:
> 
> --- "Michael B. Holt" <mholt@richmond.edu> wrote:
> > What was done was a sphere of hexagonal pieces of plexiglas were
> > assembled into a ball.  One entered the sphere through a
> > door made of the hexagons, and then one walked away across
> > the surface of the water.  So the idea itself is not impossible.
> 
> Please provide that link!

I wish I could.  The only time I ever saw it was in a Popular 
(mumble) magazine of the early 60s.  Fortunately, I happen to
have inherited all my old magazines ...  When it appears, I'll
send the pages to Ray.  Come to think of it, those ads for
dome houses might lead to some of the math.

> The geometry might be a little more involved... something close
> to a sphere can be achieved with a
> combination of hexagons and pentagons (20 hexes & 12 pents IIRC),
> look at a soccer ball for an example.  

I'll accept that you are right; I've never even thought about it
before today.  (Ah!  Check Busby, pages 151 and 163: MAKAKAI and
NEMO were both made of "12 spherical pentagons.")  I hereby
declare you the Expert in These Matters; I know nothing.

> A reasonable spheroid can be done with 20 matching
> triangles, five meeting at each
> corner; slighly less round (but therefore perhaps better for
> the purpose?) is possible with 12
> pentagons, three meeting at each corner.  This all has to do
> with the "Platonic solids" if anybody
> cares about the mathematics.

I'm curious about the math, Lew.  Let's talk about it off
the list.
 
> There are (literally) infinite possible variations with two or
> more flat shapes.  And of course
> faceted near-cigar-shapes and whatnot are possible too.

I bet there are patents, probably for structure, that would
provide some information.
 
> I wonder, though - if you build a faceted submersible, it seems
> to me that the pressure on the
> hull will be distributed very unevenly - seams vs middle of
> facets vs corners etc - could be a
> source of weakness, no?  And many seams equals lots of 
> work, too.

That's what I'd expect.  I do recall that an MTS paper of the
early 60s discussed the idea, and the conclusion was that
seams that are pressed together with external pressure are
less likely to have a leak.  But, as you say, it seems a
lot of work.

> A faceted sub would also seem inefficient in terms of drag,
> again seams and discontinuities make
> for turbulence and for pressure gradients which might create
> spurious "lifts" in odd directions,
> making for steering issues as well as for drag.

Weellll ......  Think of it as an opportunity for some bright
aeronautical or mechanical engineering grad student to get his
degree ....
 
> Or do I miss the point completely (hardly difficult to believe!)

I bet Sarah is wishing she never made this point public.  I think
we're all on the same page here.



Mike