Hello, My fatherand I are avid kitesurfers and have recently gotten into making our own boards.Our first board was made out of mahogany and is 6mm thick at the thinnest part.This has so far proven to be structurally sound but a bit too heavy, so werelooking into reducing the thickness and reinforcing with carbon fiber or fiberglass.

My question is, is carbon fiber skinning a good choice for this? Can Iapply multiple layers for skinning and if so do you have any recommendation asto how many layers would be needed to maintain the strength if I were to reducethe wood thickness by half? Also it needs to be slightly flexible to absorbimpact and would the clearcoat stand up against salt water conditions or wouldI want to apply a layer of something else on top?

Thanks much

Hi Alex,

Using composites in your kite-surfing boards will certainly enable you to strengthen then up and drop weight out at the same time and can actually be relatively straight forward to do, depending on how fancy you want to be with it.

The carbon fibre 'skinning' process is really used to describe a single layer of carbon fibre being applied to something (for the carbon fibre appearance) although it's essentially exactly the same as laminating multiple layers of carbon onto something (for stiffness) with the exception that you don't need to use a black 'basecoat' if you're applying multiple layers of carbon because there is no danger of the board's colour showing through the weave pattern as soon as you have more than one layer of carbon over it. This means that although the process will be very similar to that which you see in the Carbon Mods skinning video (our sister company) for our purposes we'll really just describe this as laminating and skip the basecoat stage.

Onto the job itself; multiple layers of carbon wet out with epoxy resin will add plenty of stiffness to your boards so you can certainly thin-down that core. How much you thin it down depends on the feel you want from the board and I'll leave up to you. If you stick with a mahogany core then that's certainly a very dense core; usually we would use something lower density for the core (who's main purpose in life is simply keeping the two outer skins in position) like balsa, cork, foam etc., but again you can experiment with what materials are right for you. I would think that dropping to a lower density core would be a good move because the core itself will add little to the stiffness of the board but something as dense as mahogany will certainly contribute a lot of weight.

The outer 'skin' of reinforcement can be applied to your core by simply preparing the board surface to ensure that it is clean, dust and grease free and has a good 'keyed' surface (coarse abrasive paper). Apply a high performance epoxy laminating resin (like our EL-2) to one side of the board and then layer your carbon fibre (or other reinforcement) onto the wet resin. Repeat the resin application (try to only apply as much as the fabric naturally wants to hold) and then add your next layer of reinforcement.

Depending on the compressive strength of the core you use I would think somewhere between 2 layers (for a dense core with high compressive strength) to 6 layers (low density core like foam) of 200gsm 2/2 twill carbon fibre would be appropriate. By doing one face at a time you should then be able to stretch release film over the whole surface of the board (over the wet resin and reinforcement) and then pull it really tight and tape it down to the reverse of the board. Because release film is translucent you can see through it to the laminate and then use a squeegee (like a credit card) to squeeze out any excess resin or air bubbles.

Once cured you can easily remove the release film which should leave a near perfect smooth, shiny gloss finish to that size of the board after which you can tidy up the edges and then repeat the process for the other side of the board.

I hope this gives you some good ideas and some confidence to give this a try because you should be able to get great results for little expense which you can then enjoy out on the water!

All the best, Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

Hello AlexC / Matt,

A question for Matt:  I've seen people suggest bagging to 65% vacuum, or 30% vacuum, etc.  We just chuck it in and switch on the pump, but we are now looking for a gauge and regulator to control the vacuum.  Can you explain how the % vacuum affects carbon fibre, and how we would select the ideal vacuum strength?  Is there potential to go to vacuum infusion for this?

Hi Aka,

The reason people vacuum bag at less than 100% vacuum (which we too suggest people should do) is because vacuum bagging, when done at 100% vacuum, often bleeds too much resin out of the laminate which can leave it with a pin-holed or pitted surface, or even fully dry patches. Not only does this affect the surface finish (meaning that lacquering, gel coating or other reparation is necessary) but it will also result in a weaker laminate. This would never happen with infusion (or pre-preg) they are more like a closed system.

To prevent this bleed-off you can reduce the amount of perforation in the perforated release film, abandon it altogether or reduce the level of vacuum (or a combination of these). With the right level of vacuum and perforation, you should be able to get a pretty good surface finish on your laminate; it's not an exact science though and we have less less 'first time success' with vacuum bagging than any other process.

I think you could move over to pre-preg, with the right planning.

All the best, Matt


Matt Statham
Easy Composites / Carbon Mods - Technical Sales

Thanks for your reply Matt,

You're welcome Aka,

Our reservation with pre-pregs stems from a reluctance to introduce an oven.   Can we make our own "pre-pregs" for the carbon outer layers that do not need to go in an oven?

Not really. If you did make your own 'pre-pregs' then by their very nature you would still need to cure them in an oven. If you don't cure them in an oven then it's not pre-preg in the conventional meaning of the work (although it could be some other technique for pre-wetting out your reinforcement).

Is there a way we can use infusion technology to achieve top and bottom off-form surfaces in a single bagging process?

To use Resin Infusion to achieve a double-A sided finish you would need to use an internal flow media that would facilitate the resin through through the laminate in place of the infusion mesh. Lantor Soric SF is a simple version of an internal flow media/infusion core but there are others. Of course the internal flow media/core remains in the finished laminate and so you would need something that has the performance characteristics that you're looking for but there are different options out there and something might fit the bill just right. You could then use RTV Silicone Rubber to make a reusuable vacuum bag with a smooth finish moulded into the top.

If we wanted to cover much of the surface with broad bands of a single opaque colour, could this be done? What about digital or photographic images? Will the resin/epoxy bond sufficiently to the film/plastic?

The surfboard manufacturers tend to have graphics screen printed onto paper or even glass tissue and then infuse/laminate them in. The epoxy does a nice job of encapsulating the pigments. I would steer clear of embedding plastics as many would be difficult for the epoxy to bond to but on this more experimental side only testing will reveal the best combinations.

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

Hi, I,m looking to make a skim board for my son, how would I conceal the join in the fiber. And is there a way of blending this in.

Hi David, welcome to the forum!