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Re: [PSUBS-MAILIST] Hull material



Robert

   the hull thickness for this depth in a 36 dia hull is .250 inches.
   the pressure hull shape should be spheres or cylinders so the problem of
metal forming does not apply. you would spend more on glass then the hull
would cost in steel, and glass is not elastic like steel. plus with glass
you would have to make the molds and then join the pieces forming a weak
spot. and with out pulling a vacuum on the mold you would end up with voids.
keep it simple go with steel.

   about buoyancy, if you have any kind of endurance planned you will be
carrying a least 500 lb. of batteries, design your battery pods to be
jetisonable. that solves the problem of emergency assent

rick m




----- Original Message ----- From: "Robert Ossian" <rob_neptune@yahoo.com>
To: <personal_submersibles@psubs.org>
Sent: Tuesday, December 27, 2005 9:33 AM
Subject: Re: [PSUBS-MAILIST] Hull material


Very good points, but but I am looking to make a sub
that is by design very postively bouyant so that a
manually released drop weight will guarrantee a safe
surfacing in case every other saftey measure fails.
Plus, my dry compartment is (to put it kindly) tiny.

Thanks for your input though - This is exactly the
kind of input that makes PSUBS such a great source of
info.

/Rob

--- Paul Kreemer <paulkreemer@gmail.com> wrote:

Robert, just one comment regarding the weights.  It
sounds like you're
considering the weight of aluminum as a negative
feature when compared to
the weight of composites.  But really, in many sub
designs some additional
weight is required to get the boat neutrally
buoyant.  Another way to put
this is: any weight saved in building a design in
composites will need to be
added back in as ballast.

A 50cf dry compartment will have a buoyancy of
3200lbs (50cf * 64lb/cf).
When ready to dive with crew and all aboard the boat
will need to weigh more
than 3200lbs to actually sink!  A lot of sub designs
are more like strong,
heavy balloons than aircraft.  That might be a
little stretch of the analogy
but it gives a general idea.  :-)

take care-
Paul


On 12/27/05, Robert Ossian <rob_neptune@yahoo.com>
wrote:
>
> I am in the very early process of designing a sub
that
> will have a maximum depth of about 200-250 feet
and
> have been wondering if there are any experienced
> opinions about using composite materials (enhanced
> fiberglass) as a hull material?  The obvious
benefits
> are that it could be custom moulded to my
> designs/shapes and of course rust-proof.
>
> I have thought about using Aluminum, but the
inherent
> weight and the fact that Aluminum would be
> (relatively) more expensive, I am looking to
explore
> alternative materials (any suggestions are
welcome).
>
> Any thoughts?
>
>
>
>
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