Re: Public response to J. Shawl

[protek@shreve.net]

To Phil Nuytten:

    To start with you have one of YOUR basic facts wrong.  It was not Jon
Shawl that made the comment about being disccouraged that someone would get
on psubs and advocate the "Any material Concept".  It was me "Gary
Boucher".  So, I feel it my responsibility to be the one to state the
response.  First, I am dissapointed that anyone that claims that they know
subs inside and out would get on here and tell a lot of people grappling
with what a PSI is that they can just build it using any material.  I
stated, if you read the whole response, that I agreed that you could build
a sub out of anything.  You can build a house or a bridge or an overpass
out of almost anything that is rigid but is that wise?  Of course it isn't.
 I don't know how long you have been reading some of these psubs ideas but
you seriously need to take some time and read back through the archives.  I
don't think you have a complete understanding of who you are talking to to
a large degree.  Many of these people do not understand the basics and are
trying to ink out some kind of design and do not know what kind of
materials to use.  Some do, but most do not know where to begin.  They are
not engineers but are ready to trust their own instincts as to where to go
and what to do.
    There was one fellow that I have been emailing that said that he was
about to start building something and after listening to this exchange
stopped and said that he felt that he did not have yet enough knowledge.
Frankly, I wish I could reach more people before they go and take your
advise, choose some far-out material and build something that will kill
them.  Rick says test it.  Well most of these people do not know how to
test it properly.
    And, yes once again I seriously question your reasoning here.  You come
on as the ultimate professional the last word in sub design.  You come on
with Youngs Modulus and Poisson Ratios.  That's fine.  I'm sure everyone is
impressed.  But where are you going to be if and when somebody builds a
plywood/fiberglass-painted sub and dies because there were no standards
that they could follow or they just take your statement and run with it
being fully assured that an "Expert" told them they could do it.  Would you
personally go down in a plywood sub built by just anyone on this site?
Assuming you knew it would hold to 30 feet and there was a 80 deep lake
there.  Would you go then?
    Forgive me if it sounds like I am upset.  I am.  I myself, and several
others have spent a considerable amount of time trying to caution people
against venturing off into some exotic material or design practice, when
there are excepted ways, published proven ways in which it can be done.
Then you seem to through it all to the breeze by reassuring everyone that
it can be done with rubber if they want.  
    There has been some talk about PVHO and that standard.  Have you ever
read it?  Where in there does it list Rubber? Concrete? Plywood? Cardboard?
 I must have missed something there.  Maybe I should read it again.

Gary R. Boucher





At 09:10 PM 2/28/99 -0500, you wrote:
>Subbers:
>        I noted, with some interest, Rick Lucertini's eloquent response to
>J. Shawl's comments ( where Mr Shawl appeared to be implying that there
>were some parties advocating research/'odd' materials/innovative design 
>etc. -  over safety):
> 
>Mr. Shawl says > "it is discouraging to me personally when some-one goes
>and says you can build a sub out of anything that keeps out water"   Well.
>goodness gracious . . of course you can!! That statement was not meant as
>my opinion - it is a simple statement of fact! You could make a perfectly
>adequate submarine ( "sub" ="under/below" and "marine'"="the ocean/sea")
>out of rubber - it just wouldn't go very deep and would take a lot of
>weight  to get it under -  but if you were content to be at ambient
>pressure and wanted high portability . . .etc.,etc. I gave the subbers
>credit for understanding that the most basic  material/geometry choices
>always exist and do so in an almost bewildering profusion  of alternatives
>- it was not my intent to discourage any-one - only to open up some of
>those possibilities for discussion . . .which I assumed was one of the
>major reasons for having a forum of this nature.
>         A  major problem with getting too specific in the subject of
>material selection/suitability/depth is that it requires a precise set of
>parameters or definitions to be known, or agreed to, by all participants.
>For example . .we talk about "mild steel" as a common sub material - what
>we really should be saying (instead of 'mild') is : a steel with a yield
>stress ( in Ksi) of 36.0000 Ksi -  a Young's modulus ( in Mpsi) of  30.0000
>Mpsi - a Poisson ratio of  0.3000 - a density ( in lbs/cu in) of  0.2830
>lbs/ cu in . We would then need to define, specifically,  what structure we
>are talking about . . .say, a cylinder with 'adequately' capped ends , size
>. .36 inches ID X 36.5 inches OD ( wall thickness= 0.2500 in ) X 60 inches
>OA cylinder length ( disregarding heads).  If you asked a designer about
>this configuration, the designer  could say " Sure, it will go into a
>thin-wall collapse mode  at 0.1573 Ksi external pressure or a depth of
>about 350 feet - and, using the 2:1 design collapse/safe working depth
>ratio required by most  certifying agencies ( Lloyds/DNV/ABS etc.,) that
>would give it a safe working depth of 175 feet.  It will weigh 483 lbs in
>air and have a bouyancy of  1841 lbs. I could give you the specific Delta
>stress for delta I D/ delta O D/ and delta length . . an so on"
>        The above is not to be smart nor patronising - it is the most 
>basic info required to make the most basic  calculation of safe depth . .
>.NOW comes the harder stuff - you say you want to cut a hole in the centre
>of this cylinder so you can get in? well, how do you propose to restore the
>strength and intregrity  of the cylinder?- doubler plate? ring? You get the
>idea. I'm sure.
>
>        Some of the subbers who have built their own subs can tell others
>how they did it . .what specific hull materials/dimensions/geometry worked
>for them . . . and most seem quite willing to do so.    Some seem to
>indicate that they have arrived at sacred grail through a torturous and
>dangerous maze and tell others that they, too, must travel  that trail and
>should listen well to avoid pitfalls. Nonsense. Basic external pressure
>vessel design is little more than arithmetic and a grasp of exactly what it
>is you are trying to do and how it usually accomplished. 
>        If you just want to know how deep your favorite propane tank will
>go, pay an engineer for a few hours of his time and quit screwing around!  
>        If you are interested in this kind of stuff - go buy a copy of a
>softback titled " Structures - or why things dont fall down" by J. E.
>Gordon    ISBN  0-14-021961-7  and look at  'tension structures and
>pressure vessels'  cost you about ten bucks . . .and I give you my personal
>guarantee that you will get much more than ten bucks worth out of it !! And
>if you like that, then try " The new science of strong materials - or why
>you dont fall through the floor"  also by J. E. Gordon  ISBN 0-14-02.0920-4
>( about $5.00) If you develop a taste for this sort of thing, there are
>dozens of such books in your local library!
>        I must thank Rick for valiantly riding to my rescue -  but it
>really isn't required . . what is, is. My opinion has no more or less
>validity than Jon's - that's what makes hores- races ! Actual facts are
>something different than opinions, however, ( unless the facts and your
>horse are one and the same! ) - and pseudo-facts, jumped conclusions,
>narrow perspectives,and all that sort of stuff - are just  a waste of
>everybody's time - IMHO
>
>Phil Nuytten
>
>