G'day shapers and tinkerers.
what density EPS core do you guys recommend for a waveboard?

.Are you going to build one ?

That's the plan

You know there is a one and only rule , a law actually ?

No

Pics man , we need many , MANY pics .

Are you going to vac bag or traditional layup.

Yes the law says photos are required.

I used 24kg/m3, with 3mm d-cell, 2 layers of 4oz glass + 6oz carbon reinforcing in the impact areas. These boards have had a lot of work, with no problems. But I haven't been over 70kg while using them, and only at Avalon, probably never much more than half mast.

But I think the stiffer you make the sandwich, the lighter foam you can get away with.
I haven't tried jumping my estuary boards, that only have 13kg/m3 foam in them. After a few thousand Km in the estuary they did develop a slight concave under the feet.

thanks Decrepit.

Yep i'll bombard you all with pics once i get started. and vac bag is the idea at the moment but i'm open to traditional lay up. would you change the blank for that??

I would use lighter eps if vac bagging because you can build stronger sandwich construction.

Id use mainly biax glass with carbon / timber patches and high density foam in the sandwich. All of the experienced shapers ive spoken with have advised against too stiff construction on wave boards because the boards snap when landing jumps in bigger surf.

no sandwich + the highest density foam you can get, Plenty of the old PU/polyester boards failed early compared to sandwich construction, nearly always in compression, because a few layers of glass doesn't have much compression strength, you're mainly relying on the blank.

And with Gestaslt's point about stiffness, I lay the carbon reinforcing between tail and mast track at 45degrees, this lessens the longitudinal stiffness of the carbon, allowing the glass to do some of the work. It also means that every strand of carbon is working.

A few strands of carbon along the board will stiffen it up, but won't have enough strength to resist a very flat landing.

No positive answer.
some posters are set in what's worked for them.
huge difference between 24 and 48 kg/ m3.

consideration include weight, strength.
S-Glass, stronger than e. Carbon stiffness, as strong as the previous layers.

Select to expand quote

decrepit said..
no sandwich + the highest density foam you can get, Plenty of the old PU/polyester boards failed early compared to sandwich construction, nearly always in compression, because a few layers of glass doesn't have much compression strength, you're mainly relying on the blank.

And with Gestaslt's point about stiffness, I lay the carbon reinforcing between tail and mast track at 45degrees, this lessens the longitudinal stiffness of the carbon, allowing the glass to do some of the work. It also means that every strand of carbon is working.

A few strands of carbon along the board will stiffen it up, but won't have enough strength to resist a very flat landing.

you make a good point about the carbon direction decrepit.

on a slightly different note, my next board build is a flat water board and i am going to try and do sandwich construction over light eps without using a vacuum bag.

For sandwich, 13kg with the right reinforcement is just fine. Similar to most factory boards
Many custom guys use 15.5kg

My 13kg core, 3mm top and 5mm bottom corecell is about 500g heavier than a cobra board due to reinforcing but could be down to 6kg if you wanted it to.

One guy was breaking factory boards pretty consistently and has two seasons on one of mine now with no issues.

I like the simplicity of old school construction and 28kg core that some guys here have done, but thats a light wind riding board, not a hard jumper.

Interesting, the same density but different sized balls of styro has a very different strength and I don't have enough of an engineer brain to interpret some of the stuff in the research paper I read. I'd love to be able to order it made like that