Fred,
Interesting analysis. I thought it would not make much difference in
overall weight. I ran a simple comparison using the Compufoil demo program
and your planform of choice. I chose the 3-panel planform from the Wurts
layups.xls as an example. I was slightly surprised.
If I did my calculations correct, a set of foam cores made entirely from
Spyder foam would weigh 3 oz more than a set of cores from Hiload foam.
However, I doubt any wings these days are made entirely from Spyder foam
As far as I can gather, only the inner wing panels are made out of the hi
compressive foams, and lighter weight foams near the tips. In this case,
the difference in weight of a set of wings would be about 2 oz.
Of course, when learning, I've bagged wings where the left & right differed
in weight more than 2 oz. just due to the epoxy content :)
Jon Stone
----- Original Message -----
From: "FRED SAGE" <[EMAIL PROTECTED]>
To: "Oliver Wilson" <[EMAIL PROTECTED]>; "Ed Berris"
<[EMAIL PROTECTED]>
Cc: <[EMAIL PROTECTED]>
Sent: Tuesday, September 19, 2000 1:04 AM
Subject: Re: [RCSE] Spider Foam
> 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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