Just out of interest, how strong are the final kayaks you are making? Do they dent easily?
I really want to make a surf kayak but am struggling to decide on the perfect layup. Your layup sounds very thin compared to what I thought I'd need to use, so I'd be interested to know how they last. I assume these are sea kayaks?

Hi Oekmont, Do you know where we can get some soric lrc 1.5 mm, I cant find it in Easy Composites shop, I would like to make some tests.

Best regards and thanks for your suggestions.

Wau - That´s a beautiful racing mashine, i would love to try it
Best Regards Keld 

Soric lrc is really good stuff, and really good for spherical parts with medium-high loads, but it is less pliable than other kinds of soric (but much more than any ccf). And it produces slight hexagonal printthoughts, although much less than 3d core for example (Wich I could recommend for heavier loads and thicker laminates). If you look for a perfect cf finish, a second layer is necessary. I used 100 g/m^2 biaxial carbon for this with perfect results. Every closed kevlar weave should be fine, too. Maybe even 80g, as kevlar has slightly less density,  and therefore more volume. But I have to say that I use 240g/m^2 cloth for perfekt cf finish, wichtige might make a difference, too

Hi Fasta, thanks for reply

I think you are right about at least some of the foam cell er filled with resin, but i dont understand why, because the water uptake should be less than 1 %

How many sqm are the dinghy you make? I'm an old dinghy sailor (Laser, europe) so i´m a litte intersted in what type that is.

What kind of paint du you use, and do you paint in mould or after?

I think we will give soric lrc 1.5 a try, and a lighter kevlar layer. Combined with a better infusion control as mentioed in other posts, it could help us to reach our target. 

Best regards, Keld

Hi oekmont, thanks for your reply

Unfortunally we dont have a oven in that size 5.5 meter, it could be worth to make one. We have no experience with prepeg so it must wait untill next project.

Part of your second suggestion seems to be able to solve our weight problem, but i´m not quite sure. Our first test hull with this layup ended up on 6.5 kg.

Gelcoat 800g + 1 layer 200g carbon + 1 layer 200g kevlar + 2mm soric + 1 layer 200g carbon + 0.7 sqm kevlar all infused in one shot... very easy methode, but the total weight was 6.5 kg. I guess that something vent wrong in the infusion process, perhaps we could save 1 kg there, and another 500g if we use 80g kevlar instead of 200g, then it still be to heavy 5 kg. But with soric light 1.5 mm instead of 2 mm i guess we could cut of 500 g more, and 2 k clear coat instead of gelcoat now we are almost there.  

There is a lot of factors to think and test through

Best regards Keld
 

Hello from me,

I would suggest two approaches:

first: You could try to use prepreg as the inner layer. If you got the oven for this, of couse. Do it all in one shot in prepreg would be an more efficient solution, but kevlar prepreg isn't easy to come by.

second: There is a different kind of soric, called "soric lrc". Lrc means low resin consumption. As you might guess this is sort of a light weight type of soric. The difference is about 700kg/m^3 to 450kg/m^3. This doesn't quite get you to your target, but combined with a lighter kevlar layer, and strict resin measurement you should be able to get there. maybe try to keep the resin pod about a metre below your mould. This prevents most of the resin overflow. I reached around 1930 g/m^2 with the following layup: 200g/m^2 carbon; soric lrc 3mm; 200g/m^2 carbon. Even with 80g/m^2 kevlar this would be a little above your target. But if you swith the inner layer to 160g/m^2 you sould be able to do it.

regards

I think that when you vacuum infuse the inner skin the infusion process fills all of the foam cell surface with resin too and this is why it is heavy.

Hi FLD, Thanks for your ansver

Jes, it sounds that it could be the reason. The vacuum was nearby 100% during the proces, but the resin flow was very slowly, and perhaps we stopped to early with infucion mesh (8 - 10 cm from the flange).

We will try to clamp off, as you suggest.

The Kayak we bulid is a 44 cm Marathon, our goal is a stiff 8kg kayak.

Best Regards
Keld