Wat material is good on top of wood? Carbon is not an option, because I can't heat it up. Glass fiber? Epoxy?

I'm building the board in wood and want to make it stronger with some other material on top...

Carbon doesn't neccessarily need heat, but it is expensive.
Epoxy and glass is the way to go.
Typical layups: 4-8oz skins over ~9-15mm wood cores, 18-24oz over same thickness foam cores.
More glass for lighter/softer wood like paulownia or balsa, less for birch poplar etc.

Carbon heat, do not understand?. For pre-peg CF yes you would need heat to activate epoxy but even then the heat would not be enough to damage even a wood core. CF has become a lot more main stream and you'll be surprised how much the stuff cost nowadays. Depends on your budget I supose. 3mx2.2m of High modules CF cost me $150, can make a couple of boards easy with that. Remember pop-out boards (manufactured) 90% of the time the CF is there more for show than anything else with bulk of the layup made up of glass you just need to look at a so called Carbon boards rail and you wiull see most of the top bottom layers of these boards are glass. To get required flex/stiffness out of a board purely from CF is just not a viable option boards would be double the cost at retail requiring multiple layers of CF.

So if you looking at using CF in your layup to make it stronger one layer of CF would not be worth the money. A single layer of CF would be more show more than anything else. If you wanted strength and nothing else a aramid (Carbon/Kevlar) fiber would be your best bet. Half the price of CF but way stronger. It requires more work and would not be used as a "glamour" last layer due to the inabilaty to sand it down properly and quite frankly it looks crap/cheap as a final layer. You could add it as a first layer and layup your glass over it. I put some in my speed board (below) is case of catastropihc failure the aramid fiber would hold things together should board break.



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Just to add a bit more support to whats already been said, I came across the chart in the link below that compares the properties of e-glass, s-glass, carbon and Kevlar/Amarind relative to e-glass. Its from the fgi website ( www.fgi.com.au)

http://myvirtualshed.blogspot.com/2011/ ... rties.html

The flexural modulus of carbon compared to the others is interesting. The high number means that the material is very stiff and carbon is known for not flexing much and with its strain to failure being 1/3 that of eglass means that it is basically very brittle. I'm guessing that this means if you are wanting a carbon board with a good amount of flex then the board will need to be very thin in order that it can bend without reaching the maximum strain. All the boards I've come across while googling around use carbon and e/s-glass to get their balance of strength and flex while minimising the total weight of the laminate used.

Something else they comment on which has been mentioned in the previous post is that kevlar holds together when the baord breaks. Whereas carbon is brittle and rips apart when it fails, Kevlar exhibits 'ductile' failure much like metal where it tends to stretche and thin out rather than rupture. Aparently the attractive characteristic is used i nboat building to keep the boat together if the hull should crack so that water doesn't rush in.

Using s-glass seems to be a great trade off in cost-strength/flexibility. Has anyone worked with s-glass to be able to compare it to e-glass?

Fracking aramid fabric is a pain in the but to use. Don't even think about using it as an outer layer and hand layup is not recommended. Impossible to sand down. It's a hard to cut. You can cut it but getting a strait clean cut is beyond me. Maybe if you buy they $100 special shears but for home use I just don't know. That said I still might use it for rails on a sup but that has more to do with having a bunch sitting around the house.

I found the easiest way to cut aramid cleanly is by using a red hot soldering blade.
It just slices cleanly through.
You have to move pretty fast with it or it will form little molten clumps along the cut.
Nico

Aaah why didn't I think of that. But surely for plain kevlar it would work but a carbon/kevlar weave it would be another story?

Ahhh yes. The fastest way to turn high tech fibers into milk jugs... heat. Good idea. I would only think that it would be a problem on curved lines for carbon/kevlar hybrids. If it's a strait cut you can pull one kevlar twill or a carbon twill and cut along the other direction with the correct cutting device. I wonder how well unaligned aramid knobs would sand.

Only works on Aramid.
Seems to react pretty much like any "normal" plastic.
Doesn't cut Kevlar or carbon though.
Nico

They don't I had a nightmare sanding down small pieces sticking out over the rails on my speed board. It just started tuffting. You have to go at it with varying grades of sand paper I started at 160 and ended up at 1000 but it still has a few spot on the edge I could not be bother about.