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Reduction of weight in the manufacture of a kayak with the use of the sandwich material Easy Cell 75 Closed Cell Foam PVC, 3 mm thickness.

 

We have previously used Soric 3mm in a construction of a kayak with one layer of carbon fiber and one layer of Kevlar, then sorric as sandwich and finally a layer of carbon fiber, all produced in a single resin vacuum process.  A strong construction, but a little too heavy.

 

To reduce the weight we have now used Easy Cell 75 Closed Cell PVC Foam, 3mm thickness as sandwich.

In the design we have, with the vacuum resin infusion process, performed the outer carbon and Kevlar layers, and after the final curing, glued with resin, a layer of 3m EasyCell75. After this glue has hardened, we have again, with the vacuum resin infusion process, performed the innermost carbon layer on top of the foam.

 

Unfortunately,the weight is almost the same, and it is apparently a weight gain that occurred during the infusion process in the foam, and the last carbon fiber layer. We know from the past that the carbon layer itself occupies only 50% resin by weight.

 

Why do we have this weight gain?

Wich methode should we use to reduce weight?

Is the infusion process and the foam not suitable?

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 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.

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?