Hi, do you think/know whether EPS foam is used in boards? It’s much cheaper than the good closed cell variants and much better in terms of shapeabilty than the cheap closed cell ones
EPS handles some polyester resins as well
I do all my board with EPS.
Surfboards, foil board for kite and for surf, and the one for my e-foil.
It works will with Epoxy resin (never tried polyester).
You have to be careful with the density, i manage to find some huge blocks of 1lb, so that’s what i’m using, but it’s on the light side… 1.5 or 2 might be better.
I’m cutting the blanks out of the block with a hot wire, cheap to do saves so much time shaping it after.
One upside of using 1lb only is that it floats like crazy and is very light, i did a surfboard for a friend with it and it feels very strange at first, but it works well and is strong enough if you use enough glass.
One thing i would advise against is to buy small blocks or sheets and glue them together. it’s a huge pain to shape after and the glue joints won’t let you have clean ans smooth surfaces. i did a foilboard for surf like that, it works, but ugliest board ever… and it start delaminating here and there…
That’s my efoil board halfway through:
And that’s after glassing and painting it:
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THank you, good read
Oh yes I would be using polyester as it’s cheaper, much much easier to work with, the foam body is relatively thick so it will be stiff either way and atop of that I had some signs of epoxy allergy last year so I try to avoid it like plague ever since, tho all type of -esters have been holding up good enough so far
I wonder if one would 'sew/stich" a thick thread, like glassfiber tow, through the dry layed skins at intervals, would this new ‘3d composite’ be Much stronger and stiffer later on when all vac-bagged and cured? Especially with normal surfboards where large areas of weak lightweight EPS foam bond could break up…, I did a test longboard with vinylester infusion (90cm x 25 cm) (600g/m2/uni-d + 200g/m2/ bi-d + 7mm H75(medium) SAN foam + 600 & 200 again) with it once it was stiff as hell. tactically pierced holes into the foam so I got these hard 'resin pillars that later didn’t let the board compress and 5 lines of keval sewed trails didn’t let the skin come apart, although lost the example somewhere, can’t find it now. little off-ramble here
How much do the shapes differ? I see you made this nice rounded displacement hull, but some like the eFoil have these futuristic sharp angles with pointy noses n stuff
Does it matter in terms of resistance whether you have more like ships ‘displacement’ board or a more like motorboat ‘planing’ board? As the latter would produce less resistance at higher speed, or it doesn’t much matter with these?
I have never been on any waterboard yet:)
With the thickness of our boards, even 1lb should be fine.
The issue might be more for ding resistance, thick glass or thin high density foam layer under it can help.
I just googled it and it seems like polyester will melt EPS, you need to coat it before…
The shape don’t necessarily matter much as it’s not supposed to touch the water much 
You just need something that planed easily without hard rails at the bottom that would catch if you’re not perfectly flat.
The constrains i used to draw mine were:
- volume (>100 liters),
- some rocker on the nose to avoid doing the submarine too much, and flat through to the tail for easier planning,
- more width than regular surfboard for better stability,
- thick enough for the batteries,
- short enough to make turning easier (and to fit in my 6ft Polystyrene blocs
)
Curved shapes are easier to glass without vacuum, (be careful to use a weaker vacuum on light EPS… too much vacuum will collapse it), and less painful when you hit the board…
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very beautiful SHELBY board … I love bravo
Do not laminate EPS with ANY Styrene based resin!!! Steer away from polyester putty even on laminated, if not already hot coated. I’ve seen boards almost finished became cave inside, because of that.
With EPS, anything containing Acetone, Styrene or other solvent can’t be used.
Typically, Epoxy is way less nasty than -ester resins, not sure if really less toxic but if you protect yourself with mask, and gloves, Epoxy is easier to use. It doesn’t “kick in” like polyester when gelling, less heat generated and it’s ready to sand smooth, no need for paraffin on hot coat and finishing layers…
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On the outside, polyesters appear to be more toxic because of the smell. Let me assure you that epoxies pose far greater potential health effects from exposure to amines in the hardener.
I cannot count on one hand, the amount of colleges from the boat building industry that can no longer work with epoxy resins because of over exposure.
Do not let the lack of smell fool you into complacency with epoxy resins. The effects are insidious until one day the effects accumulate and present. Game over for you!
Every body is different and some people can work with the stuff for years, and some weeks.
Minimum PPE is gloves and respirator with organic filters. If it gets on your skin, do not clean it off with acetone. It gets absorbed into your skin. Soap and water.
Take care.
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Exactly. Problem is bysphenol…
Yo yea with the esters it the aldehyde group (same that produces the sharp smell of ester resins) and with epoxy (at least most cheaper brands, WEST system IIRC wasn’t one of them) have some compound in the hardnerer that can enhance allergic reaction to something like the epoxy itself and materials with similiar chemical properties/structure like latex
something something
OTOH I have seen mould guys bring us small polyester plugs that have been built atop large what seems EPS blocks with zero damage, can’t remember the adhesion. I’m gonna ask the local composite guys over about it
Polyester resins are typically used on polyurethane foams. Looks similar. I think it might be a bit denser (heavier) which might be why all the big SUP and windsurf boards boards use EPS.
@Mat Hi Mat, Isaw your videos and build on bunch of topics. Best diy boards I have seen so far for efoils here,Great job! I am wondering if you are using any kind of available templates? I am about to start my first board making and a good template will help a lot.
Also if you share the source for buying big EPS blocks I would be really appreciated.
I didn’t used a pre-made template, instead i created a rough board in fusion, and modified it to get a suitable volume.
Length was constrained by the size of the block and what fits in my car.
Width was kind of free, but the more width the more stable you are before starting and at low speed.
Height was constrained by the size of the batteries plus the extra thickness needed for the box, the battery tray, the cover and a few cm of safety… safety which disappeared somehow during the build 
After that i used a projector to put the profiles on paper. you can also do it by hand by measuring point every few cm from the center line…
For the polystyrene, i found a shop that exclusively sells dummy cakes made of polystyrene, yes, i didn’t even thought that could exist. Called them up and the guy was nice enough to cut me the size i wanted… main issue was to transport them…
They only had 1lb density though… I’d feel more confident with 2lb, but it turned out ok thanks to the thickness of the board…
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Hi there Mat what size have you made your board? Thanks Michael.
it’s roughly 1800x600x120 mm
might have become slightly smaller when shaping…
Hey Matt, Ive just installed my foil. its 3d printed with 3-4layers of fiber and 2 layers of carbon but still feels a little bendy . did you have any bend in your mast or is it extremly ridget?
My mast now is a liquid force alu mast… no bend at all…
But before that i made some with wood wrapped in carbon fiber and you could support it horizontally with both ends on pieces of wood, step in the middle and it was not flexing more than a few mm in the middle. It was for kite-foiling though where the mast gets more stressed than for e-foil.
I think the “mixing carbon and glass” discussion is already somewhere on the forum but the bottom line was: do not mix them: carbon is way stiffer than glass, so as the parts starts deforming the carbon take most of the load, and if it’s not strong enough to take it, then it breaks and all the load now goes through the glass…
Only good reason to mix them is for aesthetic purpose…
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I guess you all saw Kyle Lenny pumping hard with his legs to catch the next wave.
Say we would want to also use the board that way. Isn’t that really bad for the board, risking to break it in 2 ? Would it need strenghtening compare to your presents methodology / hardware ?
Thx
I’m not sure pumping is so bad for the board… there’s some energy going through, but it’s all smooth.
gut feel, but I think the stress is more important when going upwind hard with a kite or when hitting the bottom …
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@Matt
Hi Matt, I watched your time laps video of building hydrofoil. Very impressive skills. I am very new to glassing and making boards from scratch. Would you mind sharing your method? Like number of layers, layers material, what epoxy you used?
Also wondering How long it should wait for each layers in vacuum to cure? Is it possible to go without vacuum?
Thank you
I was kind of new too glassing to when I started…
all the layers are written in the movie where I used them,
[12oz Double Bias Carbon Fiber Fabric]
[Style 262, 4.8 oz. X 30in. Carbon Fiber Fabric]
[GAO45 4.4 oz. X 24in. Carbon,]
and the resin I use is always the resin research.
for that project, it was: [2070 Infusion Epoxy w/Fast hardener]
during the vacuum it’s always by feeling, better to wait too much than not enough and kept the rest of the resin in the bucket each time to see if it was cured inside the bag…
without vacuum is ok for the board, not sure for the foil, or you’ll end up with a tick mast I think… an alternative is to compress the layers between some plexiglass plates…
but making a vacuum pump is pretty cheap… either from a salvaged refrigerator compressor or an car AC filling pump …
but before starting, think twice about using a aluminum mast… it won’t end of more expensive, will be stronger and will give you more space for the wires…
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