Re: [PSUBS-MAILIST] Syntactic Foam white paper?

[Phil Nuytten <72020.572@compuserve.com>]

Hi, Ray:
        Re: the proposed paper on syntactic foam: Efficient syntactic is
still quite a 'black art'  . . some buzz words for easier discussion:
statements like " 30 pound foam" are confusing . . .kinda like 'vent' and
'blow' and are often confused, one with the other. When you say "20 pound
foam" do you mean heavy, deep-water foam that has 20 pounds of lift per
cubic foot, or ultra-light foam, for shallower water, that actually weighs
20 pounds per cubic foot and, therefore, has 44 pounds of lift (in salt
water)? Unfortunately, those intrepid souls first embarking on the foam
trail often use the terms interchangeably.  Usually foam 'poundage' is
given as lift, so "20 pound foam" will lift 20 pounds. Foam block actual,
in-air, weight is usually spoken of as 'mass'.  So the 20 pound foam has 44
pounds mass. 
        There is a lot more to this stuff than you would think . . . 
particularly because of the monolithic nature of the pours and the high
insulating value of the material - it is prone to 'ruination by  extreme
over-cook' . It can become ultra hygroscopic by swillions of hair-line
fractures, etc. etc.
        At Nuytco, we shoot for ( and get ) 2000 foot rated (2800 foot
test) foam that can lift  35 - 40 pounds per cubic foot, or close to it,
either way. This is hard to do. First time foam-makers would do well to get
 20 or 25 pound foam and might consider basing their calculations
accordingly. Commercial foam guys eschew the refinements and often settle
for 50/50 foam ( 32 pounds of lift, 32 pounds of mass) because they can get
that reliably without having to wait on high multiple pours.
Over- cured foam is extremely brittle and has about the same structural
strength of a month-old croissant. ( I looked up the Young's modulus for
croissants but they are not listed . . .perhaps in the French edition.)
Phil Nuytten