Kiteboards: Carbon Vs Wood

[rynhardt]

Hi,

I have not watched the video, but the title is missleading. There is no full carbon board because it would be heavy as hell and would be so stiff that it would brake your bones. The right terminus is eithrer carbon or glas board. Means it is either made out of carbon or glass. Clueless boardcompanies mix both materials together for marketing voodoo. Usually the C or G board has a wood core.
Wood beats any type of foam hands up when it comes to pressure resistence / weight ratio. When you have serious molds you can wrap the bottom layers on the top layers instead of ABS rails. But even with ABS rails it still would be still either a C or G board.

Stiffness is mostly a function of thickness. A solid carbon board could be very flexible if it was like only 2mm thick. It would still sink though

Some of the lighter woods like paulownia and balsa actually have less compressive strength than high density foam. Wood is however a lot cheaper.

[rynhardt]

ps - carbon fibre is generally very strong in tension and very weak in compression.

Well, carbon's compressive strength is about 80% of its tensile strength, but for all intents and purposes approximately the same.

However, thin unsupported carbon skins suffer from buckling failure at very low compressive strength.
This can happen when the core is weak or the skin delaminates from the core.

[james]

Anything that has suffered core failure or has delaminated is doomed anyway.

Saying one skin material is better than the others prove a point when the core is dead or the laminate has failed is a pointless argument.

One without the other is useless

[iriejohn]

ps - carbon fibre is generally very strong in tension and very weak in compression.

Well, carbon's compressive strength is about 80% of its tensile strength, but for all intents and purposes approximately the same.

However, thin unsupported carbon skins suffer from buckling failure at very low compressive strength.
This can happen when the core is weak or the skin delaminates from the core.

I mean end to end (longtitudinal) compression that for example occurs to the top deck of a board when it is landed vertically from a jump.

(I assume that by "carbon" here are we talking about laminated carbon fibre fabric rather than solid carbon blocks).

[james]

Again your mixing things,end to end compression isn’t the same as longitudinal compression. LC is what occurs when you land as you describe. End to end compression is vertical ( as a column) which carbon is weak in (yes there are exceptions) but thin kite boats laminate isn’t one of them

laminated carbon has good resistance to flex, actually better in tension (the bottom of the board) than the top of the board which is actually being compressed

Laminated carbon is relatively weak under compressive load but with a bottom carbon skin resisting the compression they work pretty well

If they can be linked (wrapped rail) then it is of massive benefit to the stiffness of the structure.

Where failure often occurs on boards that are poorly
designed is on the deck where there is heavy contouring and thickness changes in sections that take a lot of load, typically the area just outside your foot pad towards the tail. Yes they want a thin sexy rail for mega super grips BUT that sets up a huge weak area for the board to break.

Look at the carved stuff or crazy flybcarbin boards, they have a very gradual taper rather than a machined step in the deck. It’s for a reason, the steps are there firvasthetics nothing more

[iriejohn]

That's what I meant. And during landing the board is also being twisted.

Again your mixing things,end to end compression isn’t the same as longitudinal compression. LC is what occurs when you land as you describe. End to end compression is vertical ( as a column) which carbon is weak in (yes there are exceptions) but thin kite boats laminate isn’t one of them

laminated carbon has good resistance to flex, actually better in tension (the bottom of the board) than the top of the board which is actually being compressed

Laminated carbon is relatively weak under compressive load but with a bottom carbon skin resisting the compression they work pretty well

If they can be linked (wrapped rail) then it is of massive benefit to the stiffness of the structure.

Where failure often occurs on boards that are poorly
designed is on the deck where there is heavy contouring and thickness changes in sections that take a lot of load, typically the area just outside your foot pad towards the tail. Yes they want a thin sexy rail for mega super grips BUT that sets up a huge weak area for the board to break.

Look at the carved stuff or crazy flybcarbin boards, they have a very gradual taper rather than a machined step in the deck. It’s for a reason, the steps are there firvasthetics nothing more