shear load . snap resistance? greg?

Again, in composites all parts of the composite share the load. Many times in a surfboard the stringer ends up being the weak link. Thanks Kenz.

Different flex charateristics can also be had by changing resin modulus. The resin modulus should, ideally, reflect the elongation percentage in the fabric. This balance of elongation provides that each is sharing the load. Many of the failures in composites come from an imbalance between the two. This is especially true in carbon composites. Few epoxy systems can provide high enough modulus for a carbon composite to reach it’s maximum yield. Most times when a carbon composite fails it’s the carbon that gets the blame. Many times it’s an imbalance from a low modulus resin.

Havard, use 1# EPS and H-80 PVC foam. The thinner the better with the PVC.


[snip]Havard, use 1# EPS and H-80 PVC foam. The thinner the better with the PVC.

Greg, is that metric desity for the PVC foam? What kind of glassing would you using under/over the PVC foam? It’s hard to find any details of a good layup for surfboards, but there are a few for sailboard, like this However, 2x5oz carbon + 1x6oz glass deck sound like overkill for a surfboard, right?



greg quoted 1 pound per cubic foot eps which translates to 17 kilo per cubic meter …the h 80 is 80 kilo per cubic meter pvc…

normally in metric 2 terms are used ,either grams per liter or kilo per cubic meter…

as far as pvc goes h 80 is fine around 3mm should do ,i actually use a slightly lighter foam 13 grams per liter,

as a general rule you still use a little more glass on the deck,or a thicker pvc …

on the deck you wanna use more glass over the pvc than under ,to make up for the fact glass has good tensile properties and poor compression …

hey kenz what do you do with composites ? coz youve posted stuff thats accurate information…

haavard once you start this your gonna have way more questions ,so rather than answer them before it happens ,ill just wait and answer them as you go ,coz theres so many possibilitys…and sounds like a few others here know whats going on as well so im sure your gonna have some good back up…

how lucky …we had to learn the hard way…



Greg and Bert,

thanks alot for the information. I’ll see what I can get my hands on and go from there.



this is a very interesting thread [:)] I can’t comment on the pros and cons of sandwich construction rhino chasers in massive waves, but I definately have a preference to this construction in the wave range that I can cope with. Its hard to give a coherent description of why i prefer it but i’ve used the words “lively” and “responsive” in other posts.

After building only one I’m no expert but to give you an idea of what worked well for me Havard here was what I did.

  1. 4oz s-glass on hull + 1/8" corecell (SAN foam)

  2. 4oz s-glass on deck + 1/8" corecell

  3. 6 oz s-glass on deck

  4. 4 oz s-glass on hull ie. a reverse lap - i did this coz i read a post by Greg Loehr months ago where he said they were getting good results with reverse lapping epoxy.

With that much glass i just don’t think its going to snap - comments anyone?

All above layers lapped fully, no deck patches but i did put some oval patches for the lokboxes. SAN foam did not cover edge of rails but full laps give a total of 18oz of rail reinforcement. I took the hull SAN foam up to the edge and semi wrapped the top layer about as much as i felt the vacuum would bend it without any heat treatment.

the above seemed the easiest to me, but it would be nice if you could try some of the rail reinforcing suggestions given by Bert, then post how you did it here so we can all learn.