Build XPC core & epoxy - Allround wave board Ghetto Style

[tungsten]

New project! Always busy in the quest for the best allround wave board. Mushy sloppy blown out low wind stuff, the typical conditions where Kelly Slater would stay in his hammock and read a good book, but which many of us have to deal with on a daily basis.

I found an allround shape I like very much, by Amundson, which I used as an inspiration. The built is going to be Ghetto Style: I want to see if I can build a board for next to no cash out of Styrodur XPS sheets. Some have done it, some reported delamination issues, some say it works. We'll see! To make it more challenging, the sheets are 1.2m x 60cm, and the board is going to be 1.65m long... this is going to be interesting.

Anyways, it sure would be easier to give Amundson a call, and 2 weeks later the board would be sitting in front of me, perfectly nice and ready to go. Aaaaah, but that's too easy, this is about home grown boards after all. And it's not an option for many who just don't have the green to choose the easy way.

A quick preview and a couple of pics. More to come later!

[Lonny]

Great post as always Tungsten. Interesting idea using the XPS sheets. Amundson definitely makes some good shapes. I look forward to seeing how it turns out!

[spewing]

Intresting shape. Definatly a board for the conditions most of us ride.

Looking forward to see what you create.

Kev

[tungsten]

Finally I got around building this board. I had to do extensive tests with the XPS sheets, because some reported delamination issues with XPS, and I wanted to make sure it works before I build a board. Now, gluing XPS was an issue, but it is resolved. I tried all sorts of glues (white glue, polyurethane glues like gorilla glue, hot glue...) and it didn't work. My test ran like this: I cut some test pieces of foam and glued them together. When the glue was set, I tried to break the glued test piece in two. If it breaks at the glued spot, the glue is not good enough. If the XPS breaks in a different place, it's all good, the glue is stronger than the original material.

GLUE
I found epoxy, thickened with colloidal silica (West System 406) to a gooey paste, works perfectly well. The XPS surface you want to glue or laminate MUST be thoroughly sanded (I did 80-120-180). NOTHING will stick on the unsanded surface of XPS sheets. Then, after sanding, work the thickened epoxy in the surface with a squeegee. Small quantity will do, but it is essential to physically work it in. XPS has such fine closed cells, epoxy won't diffuse into the material without pushing it.

I also found a way to make the laminate 100% delam resistant: before I laminate, I work some thickened epoxy into the surface of the XPS blank. Tiny quantity, like 40gr (1.5 OZ) per side. Thereon I lay out the glass and laminate as usual. The result: I did the above breaking test with laminate. Trying to rip the laminate off the test piece, it would rip the test XPS piece in parts. The bond is stronger than the material.

(As we are at it: I spread out a very thin layer of thickened epoxy before I brush on the "hot coat" (epoxy): No fish eyes whatsoever.)

CUT
The best way to cut XPS I found are those sharp foam knives, like a carpet knive, but long blade. They are razor sharp and work just fine. Thereafter, sanding with the drill (24 grit and low speed, otherwise the foam melts) and by hand (80-180 grit) worked perfectly well. (Buy a couple of those knive blades, they don't last forever.)

[tungsten]

Building the board: I printed out the profile and outline and cut a stringer (and a spare one, if I fark up or like the board very much) out of 5mm ply wood (the light sort).

Cut my XPS sheet in half, sanded the cutting edges until perfectly rectangular and even. cut the small pieces of XPS for the front part of the blank, and cut the accurate angle. Glued it together with thickened epoxy, fixed it and let set.

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[tungsten]

Cutting out a rough outline and shaping.

[tungsten]

Glassing: I put on 3x 4OZ on the bottom and 4x 4OZ on the deck. Good glass is essential and a lot easier to work with, I tried cheap ones and hated them. In terms of epoxy, I tried some from cheap to expensive (8$ to 40$ the kg). I found: for boards you would paint anyways, or if you don't care your epoxy yellowing out, the cheap stuff does the trick. Only if you want UV protected epoxy for transparent surfaces, you should go the expensive way. Mechanically there are sure differences between epoxies, but I doubt you will notice the difference between a cheap and and expensive epoxy suitable for laminating. Boards break anyways after some abuse, be the resin cheap or expensive.

The board has wrapped rails, which means, I fully wrapped the bottom glass layers to the deck, and let the deck glass layers hang all the way down the rail. This gives a solid 7 layers (tapered to 6 and 5 towards the tip) of glass in the rails. As the board is quite thin, a bit more strength is a good idea, but it has still some flex, being tapered.

Next is drilling the fin plugs and glueing the fin plugs in. As you see I have some wooden fin dummies for this, easier to handle than fins. Glue is pure epoxy this time round, which I worked into the foam in the fin plug holes to achieve a good bond.

[tungsten]

That's almost it! As a light grey board is butt ugly and would never be spotted in some white water, I decided to paint the whole thing. Consulting my daughters I ended up with "make it pink", which I outright refused, which they didn't like. Anyways, after some time we had a decision: One kid says "white", one kid says "orange", threatening me with not letting me use my computer if I don't obey. That's why the board looks like the board looks. It's a quick spray can job btw.

Done! slapping on some strips of 5mm EVA for footpads, mount the fins, and off we go.

The board came in at 2.4kg with pads but without fins. Thickness 4cm in the middle, down to 2cm in tip and tail. volume is 18 liters.

Hope you enjoyed,

tungsten

P.S. the price list for this board:
stringer 1$
foam 6$
epoxy 1kg = 8$
colloid. silica 2$
E glass 10m = 40$
fin plugs 15$
spray paint 5$
--------------------
total 77$
work 8h

P.P.S. no wind today, I come back with a test another day. Good winds!

[Lonny]

Hey Tungsten,

An amazing project! It is very interesting to see each of the steps involved, and fantastic insights you share during construction. An encyclopedia of information. Thank you once again for taking the time to share it with us here at LTS.

Honestly, I like the paint job. The orange and white looks kind of cool, like a cremesicle surfboard.

Not too shabby for $77. Heck you might spend more on a decent set of fins. Weighing in at 2.4kg or 5.28 lbs is not bad at all. Amazing how expensive that E glass is.

I look forward to your most important report. How is rides and feels. Again, great post!

[spewing]

Really like your work and hope it rides as well as it looks.

Do you think the but joint rather than a scarf joint between the two pieces of XPS will hold up?

2.4Kg with what sounds like a strong glass job is quite impressive.

Look forward to a ride report and some more photos.

Kev

[Yann]

Nice work Tungsten, I'm impressed by your skills!

How many layers of glass does a regular surfboard have (not meant for kiting)? I have a Lost Speed Demon III that I'm about to put some extra layers of glass on. I have some 160g (6oz) glass laying around and I'm thinking of putting one big layer from just below the logo all the way down to the leash plug. Then I'm thinking a second layer, about 40cm for the front foot. What do you think? I don't want to kill all the flex so I don't want to put on too much glass.

[spewing]

How many layers of glass does a regular surfboard have (not meant for kiting)?

Depends on the board and how it will be used but on A polyurethane blank 6oz bottom and 2 x 6oz top would be quite a heavy layup.

Quite common to have a 6oz patch over the area with the most abuse and the a full layer of 6oz.

Some prety disposable boards are 4oz bottom and 4oz patch and full 4oz top but they ding quite easily and thats just surfing.

Kev

[tungsten]

Thanks for your compliments! I was really surprised how easy XPS is to work with and how light and sturdy is the outcome. Re: but joint / glue: yes, it will definitely hold up. Was quite doubtful myself, so I tested it at length, destroying glued samples. Not one time the joint gave in, always the foam, in a different place, away from the joint. I definitely want to encourage anyone who wants to build a ride to try XPS.

As of weight, the shaped blank including stringer came out at 790gr. If you wanted to build a real light board, with XPS it is possible. XPS is a lot sturdier and stiffer than EPS, and it's closed cell all the way, which means, holes in the board don't matter. You keep on kiting and fix that thing when you return from your holidays, it won't take any water.

Yann, as spewing says, 4-6 OZ bottom, 2x4-6 OZ top is a normal-to-heavy glass job for a surf board. If you want to beef yours up keeping flex, consider just doing heel strips. Really depends on what you want to achieve. Slapping on 6OZ from almost tip to toe may be overkill if the board is in general strong enough and just dings. 6OZ might not even prevent it from dinging, on the other hand. I will probably use less glass and a 3mm plywood patch on my next XPS board (like 2x4OZ bottom, 2x4OZ top plus a 4OZ patch plus a ply patch).

As of riding: just had it out for half an hour for a quick spin in dying wind. Very promising, though have to regroove the foot pads as they are slippery. The board feels easy and balanced. I'll do a proper write up after a couple real sessions in different conditions (read: different kinds of chop )

[tungsten]

Finally I got a chance to ride the board for a couple of days. After the first quick spin, I adjusted two things: re-grooving the EVA footpads for better grip, and changing the fins. Grip is perfect now. First I had a set of cheapo surf fins, 100mm base x 120mm depth, with quite a bit of sweep. They might be good for surfing (dunno), but for kiting, they are a drift anchor. As soon as the board speed picks up, you feel that invisible hand grabbing your tail and holding you back.

So I took that set of cheapo surf fins, a jig saw and a grinder, and made my own fins . This is actually rather easy. I was looking for less sweep, less depth and an approved foil and found those FCS looked like what I wanted. Made my personal copy, cutting down the plastic fins to 80x100, with a NACA 0012 foil (outside) and hollowed out on the inside, and I must say, I am delighted with the result: the board came alive at speed, enough grip, good balance. The rear fin is an ordinary small 80mm base x 100mm depth surf fin and works well so far.

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I rode the board in 12-20kn, side to side-on, sloppy shore break, from knee high to shoulder high. It is very easy to ride, super stable (the wide outline with loads of width in tip and tail works really well in those conditions) and feels perfectly balanced. Going out through the shore break without any problems or pearling or anything, accelerating fast with little wind, going upwind nicely. I found it rides best with a rather wider stance, I did not have to move the feet around much, just shifting the weight did it, which makes for a nice lazy ride in the shore break.

Playing with the slop snowboard-style, the board is loose and turns on a dime, goes rail to rail with ease, and carries well through tight turns without losing momentum. Nice! I did a couple small jumps (I'm not very good at this), and had the board glued to my feet, sticking the landings on the first attempt. Very nice! Did not have a chance to try it in clean waves, but I carved some fast turns behind a wave, to see how it goes, and it tracked well, felt good and stable, and I could lay in with all I had without spinning out, as long as I kept pressure on the front foot.

To conclude, I am very happy with this board. Great shape Mr. Amundsen, thanks for that!

[Lonny]

Hey Tungsten,

Great report! Awesome project, and it's even better that the board is meeting your performance expectations. I love that you had to make your own fins. Actually, had you not it would have been out of character. Choosing the right fins make a massive difference in the boards performance and ride. Todd's new board was horrible until he swapped out his fins based on Jon's feedback.

Sounds like you have a great ride for the next year. Nice job!