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Brent, You shouldn’t consider syntactic foam as a structural
material in combination with a steel hull. This would be considered a
composite composition and to work properly, the Young’s modulus of the
two materials should be close. If you were to pursue this idea, your sub’s
hull would be very difficult to work on in the future since the syntactic foam
against the hull would have to be removed for maintenance or welding. A
well developed hull that is not going to extreme depths in the ocean should not
need syntactic foam for buoyancy (we are usually worried about how much lead we
have to add) as the hull is not real thick. The R300 is a unique
case as the design strived for the minimum volume to theoretically obtain the
optimum hydrodynamics for speed. You have to be careful installing foam inside against a
hull. Condensation will collect behind it and result in corrosion that is
not obvious. Besides, syntactic foam inside the hull gains you nothing. You keep returning to the Bionic dolphin but it is designed and
built to a different set of operating parameters than would be optimum for a
PSUB. R/Jay Respectfully, Jay K. Jeffries Andros Is., Bahamas A skimmer afloat is but a submarine, so poorly built it will not
plunge. From:
owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Brent
Hartwig Jay, You make a very good point, about using
syntactic foam as much as possible in a way you can work on, or reconfigure the
sub in the future. I've had that in mind for some time now. Some designs
can be done in such a way the the syntactic foam is apart of the strength of a
pressure hull, like the beautiful R300. In that case I would make sure the
metal is carefully treated before it is encased in foam and forget about trying
to do a major reconfiguration later. With regards to my design of
filling the spaces between the ribbing of a K-250 internally, to insulate,
sound deadening, and some extra strength that could be needed in a emergency
like a collision with something or forced deeper then 250'. I could attach the
foam solid to the hull for maximum strength, or wax and then spray a mold
releasing agent on the steel hull surfaces, and then cast the foam. This way
the foam can be removed much more easily. I still don't know how much difference
there is in the expansion and contraction of the foam to a metal hull, wether
the foam completely covers the inside, the outside, or both, as well as if it's
just on part of the hull, like on the Idabel? Will the foam want to pop
loose, or will they move together? I'm aware that it would also depend on the
hull size and thickness, as well at the foam type and thickness. Doc is using a
urethane binder in the new two seater Bionic dolphin. The urethane will
flex allot more then a most resins used to cast syntactic composites and so it
will not have as high of depth rating as most other types. Regards, Brent
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