Hey all,
I’d like to know what is the ideal compressibility/compression strength of the polyurethane foam for boards. On us blanks’ site, i have seen there’s a lot, but they do not mention numbers so i don’t know the range.
Until now, i used EPS, which is about 200kPa and i can only get PU foam around 130 kPa which i guess i too soft for a surfboard, since PU is said to be harder than EPS, am i right?
Please let me know!
Thanks!
Minimum compressive strength is useful information, but not commonly used to discuss surfboard foam.
Density is a more commonly reported property of surfboard foam – lb/ft^3 (pcf) or kg/m^3.
Classic old PU density was 3 pcf. PU blank foam is more dense on the outside than in the center.
EPS densities used for standard blanks will run between 1.5-2.5 pcf.
For EPS surfboard foam, a good estimate of minimum compressive strength would be 10 times foam density, that is, 2.0 pcf would be close to 20 psi min. comp.strength.
Check your PMs.
A factor of 10 times pcf is not really that good an estimate.
For XPS. the relationship between min. compressive strength (mcs) and pcf is not linear.
Dow XPS has the following mcs/pcf ratings: 15/1.3, 25/1.6, 40/1.8, 60/2.2, 100/3.0
That’s right, in surfboards world it’s common to use density of foam as indication. Not so bad because for most denser foam have better mechanical strengh. Not so good with pu because density is not constant in blank. In a sandwich build like surfboards, for durability, foam need to have the higher compressive and shear strengh. Lower are those characteristics stiffer need to be skins.