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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?

You could possibly save a little weight by doing the infusion in one go and this would require you to create small holes in the foam at approximately 50mm intervals. I imagine that applying resin by hand when secondary bonding the foam adds a bit more weight than desired.

Hi MarkMk, Thank you for your ansvar.

I dont think that your suggestion will help much, because we only used 200g resin when we applied the foam to the fist layers. I think we have to explain the weigth in each step throughout the process for building the half part (the hull), approx 2 Sqm in each layer. We want this part in total to be max. 4 kg

1. Clear Gelcoat 800g in mould (We think we will try use 2k clear coat or nothing here insted next time)
2. First carbon 200g and kevlar 200g, Infusion
3. The weight at this point after a full cure was 2.6 kg
4. Easy Cell 75 Closed Cell Foam PVC, 3 mm, glued by 200 g resin, by hand.
5. The weight at this point was here 3.6 kg (At this point we expected the total weight to end up arround 4.5 kg)
6. 1 layer of carbon 200g + 0,7 sgm kevlar on strategic points
7. Resin infusion. After full cure, the weigth was 6.5kg Far to heavy we think.

We have made some tests with drilling holes in the foam, and infused all layers in one process with good results. But we thourght it would give us some troubles to hold all layers in place during the layup and vacuum proces. But we would love to do it all in one shot.

Best regards, Keld