Foam Core in a composite kayak

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#1

Hello all,
I’m looking to make a DIY composite freestyle kayak and would like to utilize a foam core in many different parts. I have a few questions:

  1. With a similar nominal compressive/tensile strength is it a good idea to use Polyurethane 2 part foam vs. using a poly vinyl?

  2. On the hull of the boat I was planning on sandwiching a core, but want to give it a true “I-beam” feel with webs of carbon spaced some distance apart amidst the flanges (that are of course just the next layer of fabric). Would it be best to have individual foam beams wrapped in carbon butting up together, or is it strong enough as a traditional “core” with just one core and laminate on both sides?

#2
  1. Forget PU foam. Go either PVC or SAN foam. Depending on requirements choose:

cross linked PVC (stiff, somewhat brittle)
SAN (less stiff, ductile)
lineair PVC (not so stiff, very ductile)

cross linked PVC: Airex C70, Divinicell H series, etc
SAN: Core-Cell
lineair PVC: Airex R63

Choose a 80 kg/m3 (5 lbs/ft3) foam.

  1. I am not fond of shear webs. You can design a normal core as strong as it needs be.