OK folks...

I'm going to have a crack at building my own SUP, a 16' downwind board. Now I've done a bit of boatbuilding, but haven't used EPS before, so here's my methodology and please feel free to suggest otherwise.

Laminate will be 135g Innegra closest to EPS then 200g carbon over that. Rails will be doubled up so bottom skin will run over rails to deck and deck skins will run down rails to bottom of board to stiffen board and provide some impact strength where it needs it most. In the standing area will be 4mm perforated PVC foam (with resin filling the perforations) with an additional skin of carbon on top of that. Fin box/rudder, steering and leash points will have additional local reinforcement.

The plan is to do most of the lamination using an infusion process, but to start, do I resin coat the blank (using Qcells or Microlight) before laminating or do I just wet lay up the Innegra on the blank, peel ply it and then infuse the rest?

Over to you...

Pretty sure there's no need to seal the blank.

The build specs sound great.

Definitely seal it first. It stops excess resin seeping in and adding unnecessary weight and as Kami said reduces the number of annoying pin holes.

Bill

Magilla,
I would have thought that you would get better lamination (cloth to foam) by NOT sealing the foam beforehand.
You can always run over the laminated board with micro balloons after lamination and before painting (yellow of course!), but if you seal the foam beforehand you add another layer of lamination to the mix - ie lamination of foam to sealer, sealer to cloth.
Given the flex that these boards go through (especially with some of our more portly members...) I would think the risk of an extra kg of resin is better than the risk of delaminating the whole thing.
But whaddoIknow, I'm just a dumb skiff sailor! Happy to be corrected!

Helmy said..
Magilla,
I would have thought that you would get better lamination (cloth to foam) by NOT sealing the foam beforehand.
You can always run over the laminated board with micro balloons after lamination and before painting (yellow of course!), but if you seal the foam beforehand you add another layer of lamination to the mix - ie lamination of foam to sealer, sealer to cloth.
Given the flex that these boards go through (especially with some of our more portly members...) I would think the risk of an extra kg of resin is better than the risk of delaminating the whole thing.
But whaddoIknow, I'm just a dumb skiff sailor! Happy to be corrected!

Helmy

The board will have to be faired after it's laminated and pre-painting. I'm not that good! Theres a risk with infusing the board that the resin finds its way between the beads of EPS, hence sealing the board first with the first layer of the laminate and vac bagging to ensure good adhesion and then infusing the rest. Microbalooning the foam blank first just adds weight. Some fibre can do the same and it has a purpose

I'm working on having a board that doesn't flex or has minimal flex. I'm not convinced bendy boards are fast, but I'm just a dumb one-design sailor. Maybe I'll just keep winging it!

HumanCartoon said..

magillamelb said..

I'm working on having a board that doesn't flex or has minimal flex. I'm not convinced bendy boards are fast,

Hmmm...i tested a board recently that was SO stiff it felt sort of dead and wasn't a pleasure to ride. There's stiffness, there's flex, and somewhere in between there is 'compliance'. I reckon a little compliance in the ride can be a good thing (especially for maturing gents with creaky knees and backs and so on).

Maybe not on this forum, but can you let me know what it was?

I infuse moulds twice a week and i have made a few EPS boards too over the last few years , IMO you cannot infuse an EPS blank as the amount of Vacuum needed will crush the foam core, if you stumble across a foam that will not crush (ps you will not) then it will drink gallons of epoxy due to its open cell structure , the best laminate you can make is a high density PVC sheet foam (or wood veneer etc) vacuum bagged on at low pressure and it will need a fibre of some description between the EPS and the foam/timber/bamboo etc or heaps of other bad **** will happen .

You must have so much time to play with ? if you try to vacuum just a fabric down first even the lowest pressure will push the fibres into inevitable voids (missing or torn foam balls) and you will have a golf ball looking result , then you cannot sand the innegra due to it "fluffing up " (it's a poor mans kevlar) which is why professionals use glass or carbon on top of the innegra . Let alone the cost of the consumables you will waste

latman said..
You must have so much time to play with ? if you try to vacuum just a fabric down first even the lowest pressure will push the fibres into inevitable voids (missing or torn foam balls) and you will have a golf ball looking result , then you cannot sand the innegra due to it "fluffing up " (it's a poor mans kevlar) which is why professionals use glass or carbon on top of the innegra . Let alone the cost of the consumables you will waste

That's exactly why there is a layer of 200g carbon with a fibreglass veil (hopefully infused) going over the Innegra. Then fair and paint.

I am appreciating the advice Latman BTW!

Thanks Bertie & Latman. I peel ply everything I do anyway as a matter of course and will very lightly screed/seal/fair the blank before I lay anything up.

if you use "neat" (regular laminating epoxy) you get little "tentacles" of it penetrating the foam core , this does add some grip/shear strength to the laminate but it also adds weight , If you were going to seal the foam first with a filled (Q-Cells, Aerosil, Microspheres) it would indeed save some weight but it may also lower the grip of the laminate to the EPS , I would do that over the wet filled foam , I would never use spackle ( plaster?) personally as it introduces a 3rd "chemical" to the mix.