From JP:

"Technora®’s breaking strength is one of the highest of all fibers, it is 8 times stronger than steel and has 4 times the elongation at break than Carbon.
Kevlar™, which is an aramid fiber – just like Technora – is also used for bulletproof vests – that probably explains why it is very good for impact!

The material combination of Technora and Kevlar is ideal as it makes the decks of our smaller Pro Edition boards, which are used for jumping a lot, super strong in terms of breakage strength and impact durability. "

I'll assume the deck is at least 1mm thick, does this mean it is the equivalent of 8mm of steel in strength, or does kevlar reduce the strength a little? Does anyone know what the mix of Technora/Kevlar actually is? Bullet-proof steel is about 6mm.

Is this just marketing clap-trap? (I still like JP)

Will 1mm of Technora/Kevlar be as strong as 8mm of steel? No.
Will a windsurf board with 8mm of steel on the deck float? No.
Will 1mm of Technora/Kevlar be 8 times as strong as 1mm of steel? Yes.

And I'm going to guess that the tests were in tension. (not shear, or compression)

The deck won't be one layer of fibres over a foam core, it's more likely to be a layer of fibres over a dense foam (PVC/divinicel etc), then a layer of fibre again (probably not the expensive stuff though) and then the soft foam core.

Have a look at this: boardlady.com/sandwich.htm
And this (which I've linked from the board lady site - it's a JP 'high wind' board)


www.boardlady.com/anatomy.htm

Aaah, so it's all about tension. I imagine it is similar to water tension, where a small bug can walk across without breaking it, but if it goes in too fast (like a hammer) will break the water tension. The strenght lies in the tension.

Thanks for that, the sandwich link was very, very interesting.