Perhaps we should make a google doc with the properties for each material, perhaps a link to the source.

>I compared mainly the density, since it seems to be fairly proportional to strength (compressive, tensile, shear).

Ah. I was comparing XPS by compressive strength, cause thats what seems to matter. Also the XPS is named relative to that. Dow and Owens Corning name from lowest 10, and 100, respectively, for the 10psi, up to 100, or 1000 for the 100psi.

Yes, the properties are proportional to density, but not linearly. It's curve. Also, there seems a lot of heat in the discussion. So, as a nerd, I retreat to accuracy. Also there are many grades of PET, which also curve properties relative to density.

>The cheap xps seems to be about 25-30 g/cm3. And the strongest xps I've found had 45g/cm3. The other foams where 80-100g/cm3. So 1/4 was from 25/100, and 1/2 from 45/80.

Right, but the 10 psi foams are 1/20th the psi. of H80. And the 100psi is half the psi. Density up 50%, psi up 10x. That's a curve, not linear.

>With what do you agree?

It was, perhaps, a joke.
I agree with everything you said, except in all these areas where I don't. I am not sure it is that funny.

>What's the spec of the xps used in aircraft construction?

Here is the section 1 foam kit for a cozy mk iv
http://www.aircraftspruce.com/builderkits.php?PN=01-01410
The Cozy is an enlarged longEZ. You see a variety of foams used in its construction, not just one. The reason is simple. Aircraft need lightness. Aircraft builders work hard at saving weight way harder than boat builders. So they put the lightest thing they can wherever they can. Note, some of these foams have been swapped out for newer versions as a few originals are no longer available.

I am not going to go on, but clearly, one cannot claim 'XPS is used on planes, so its the best'. H80 is used in planes too! So we have to be careful what lessons we can learn from planes.

Final note. The wings and aerodynamic parts were ~25psi XPS. These were wet layup fiberglass skins, that were way heavier than they strictly needed to be for flight, as wing skins need very little actual strength. They need way more strength to stop impingement damage from a flying creature, or people setting things on, or being grabed, or pushed than they need for flying stress.

Actual wear and tear from ingress and the cockpit used other materials.

There was also solid spruce planks imbedded in the rails of the cockpit, because people pulled and sat on that part alot, and it was critical in a crash.

P.S. if one can flat infuse a wing skin, and wrap it around stringers and spars, that is huge. That is THOUSANDS of hours of bullshit saved.

Can one bend a foam core that much?

• New Members 1