Ollie;
Some of what you stated is true but I'll correct what isn't. Yes, Spyder Foam was
developed by Dow to the specifications of windsurfer board makers. Consequently the
billet size is 2'X10' X5 1/2". Yes it's called Surfboard Foam in the industry and the
name was changed to Spyder Foam when the foam was marketed to modellers. However,
Surfboard Foam is still available (I bought 10 billets about six months ago) and the
specifications aren't the same as Dow HighLoad 60. As an example, Highload 60 is a
homogeneous extruded foam and the compression resistance is 60PSI in all three axis.
Spyder Foam OTOH has a specific cell orientation and the compression resistance of
Spyder foam is 45PSI in the major axis (5 1/2") and 25 PSI in the other two axis. You
do make a good point that HighLoad 60 makes an excellent substitute for Spyder Foam.
In fact, on a strength to weight basis, Highload 60 is superior to Spyder Foam with
Spyder Foam having a weight of 2.3 pounds per cubic foot and HighLoad 60 weighing 3
pounds per cubic foot. You're also correct that Highload 60 is more readily
available and cheaper than Spyder Foam. However, for Thermal Duration gliders where
every ounce counts, Spyder Foam is still the foam of choice for high compression
resistant applications. In slope gliders or scale ships where weight is unimportant,
Highload 60 is clearly superior.
Fred
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