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Foam core board build and a question for the next step

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jcres
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Foam core board build and a question for the next step

Postby jcres » Thu Aug 18, 2016 7:34 am

About four months ago I got an idea while kitesurfing to build my own board. The board I was using back then started to be quite broken after hitting too many rocks at my local beach. So I head to google and found this forum. I spent quite much time reading all the different experiences to get an idea where to start. I have now built couple boards, some with wood core and some with foam core. From this point onwards I will continue with foam because of the weight of it. I really like riding a light weight board rather than heavy. After each board I have built, there are plenty of new learnings. So it seems that I have a long way to go before I am satisfied.

Here is a short story of the latest build I did and I hope it helps someone who is building boards to find needed answers to some questions.

The board size is 142x42 cm and I start with a 10 mm PVC-foam (60 kg/m3). I have printed to a paper the full size board plans which has all the needed holes and fin places marked. With the help of that I draw all the necessary things to foam. Then I use a router to grind the space for rails. For the outline I have a plywood model of the board.

I have cut ABS to 12 mm strips which is the same size as the router bit I am using. With heat I then bend ABS to rail shape.

Reinforcement for the fins is casted with epoxy containing some chopped fiber glass.
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jcres
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Re: Foam core board build and a question for the next step

Postby jcres » Thu Aug 18, 2016 7:48 am

In the middle the board is 10mm and outer side it is 4 mm. I use router to get all the excess foam away until I get to the rail level. I start with the router from the outer edge and continue to the middle. I do not use anything else than hand to get the board shape.

After the board shape is ready I cut reinforcements from PVC bar for the inserts and make a place for those in the board.

Then I build the rocker table. To make things simple, the rocker table is just some plywood and which I attach to my work table. I use wood strips to get the required rocker and concave. Then I have acrylic sheet on top of plywood.
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Last edited by jcres on Thu Aug 18, 2016 9:02 am, edited 1 time in total.

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rynhardt
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Re: Foam core board build and a question for the next step

Postby rynhardt » Thu Aug 18, 2016 8:42 am

Looks good so far!
What foam are you using? Divinycell H?
What weight and length are you? Your stance width looks a bit narrower than what I'm used to.
And lastly, what layup schedule are you planning? Glass? Carbon?

Good luck!

jcres
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Re: Foam core board build and a question for the next step

Postby jcres » Thu Aug 18, 2016 10:12 am

rynhardt wrote:Looks good so far!
What foam are you using? Divinycell H?
What weight and length are you? Your stance width looks a bit narrower than what I'm used to.
And lastly, what layup schedule are you planning? Glass? Carbon?

Good luck!
I think the foam is Gurit PVC 60 (http://www.gurit.com/gurit-pvc.aspx) or then it is some of those Corecell foams. The weight is the mentioned 60 kg/m3. Local shop sells it and I forgot to ask what is the name of it. The stance is the same as I have in my RRD kiteboard so it feels familiar for me.

I have already built the board and I will post the layup and some other information now. I just got distracted before finishing up the build story. :) I try now to write more.

jcres
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Re: Foam core board build and a question for the next step

Postby jcres » Thu Aug 18, 2016 10:22 am

The layup of the board is same on the bottom and top:

179 g/m2 fiber glass / carbon fiber hybrid cloth in 0/90 degree (ratio of fibers is around 50/50 I was told)
300 g/m2 uni-directional carbon fibre in 0 degree ending on fin reinforcements (you see in the pictures where the ud carbon ends)
Cotton fabric for the colors

Epoxy is SP 115.

The layup makes the board really stiff on the middle but it has flex on the tips. Cotton is under the glass/carbon layer. I laminated separately top and bottom side to get all the excess resin out. First I laminated the top to get the rocker and concave in the rocker table and then the bottom just using a bag.

Core weighed only 520 grams before lamination and the finished board only 1780 grams.
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Last edited by jcres on Thu Aug 18, 2016 10:36 am, edited 1 time in total.

jcres
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Re: Foam core board build and a question for the next step

Postby jcres » Thu Aug 18, 2016 10:35 am

After riding the board and I can only say that it worked really good. I was wondering that as it is so light will it last... And well, something came up. As the carbon ends almost at the part where the board goes from 10 mm to 4 mm it creates a weak line and some of the fibers broke at that line. So there is something I need to make better for the next one. I think I will extend the UD carbon on the other side almost to the tip. Anyway I made a fix and I can again enjoy riding the board. I am a quite big fellow weighing 90 kg so I need a board what take my weight.

Everyone knows that there are tons of details in the build that I did not tell. But in case you want to know more, please just ask.

And this leaves me with the question I have. The looks are not what I want them to be. So I talked with a local print shop, which is eager to help me to find a good solution for the graphics. Do you know what is the material that commercial boards are having on top and bottom? It is some plastic what is printed but what is the type?
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rynhardt
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Re: Foam core board build and a question for the next step

Postby rynhardt » Thu Aug 18, 2016 11:16 am

Some commercial boards use something like PBT (polybutylene terephthalate) for the top and/or bottom sheets. I think the graphics are dye-sublimated into the PBT. Have a look at junksupply.com.
If you need a grind base, the wakeboard companies use sintered UHMWPE.
Some companies just paint the boards with a silk screen process.

So, some of your options are:
* Paint it. Easiest.
* Apply a printed top and/or bottom sheet. Nice, but not easy to do. Supply is problematic/expensive in small quantities.
* Apply a printed fabric below the glass. (What I currently do - my local print shop can do this on their normal material)
* Or just apply vinyls or a board skin to the top deck - they last remarkably long. have a look at boardskins.com

BTW: I also use SP115 for hand layup. It's a very nice resin system.

jcres
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Re: Foam core board build and a question for the next step

Postby jcres » Thu Aug 18, 2016 2:06 pm

Thanks, Junk Supply was a great tip! Placed one order right away there. I am from Finland and nice to see that there is a shop "almost around the corner". :)

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rynhardt
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Cloud C2 17
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Xelerator door
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Location: Johannesburg, South Africa

Re: Foam core board build and a question for the next step

Postby rynhardt » Fri Aug 19, 2016 7:33 am

jcres wrote:Thanks, Junk Supply was a great tip! Placed one order right away there. I am from Finland and nice to see that there is a shop "almost around the corner". :)
Lucky you 8)

You must post your next board's progress here as well!

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downunder
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Re: Foam core board build and a question for the next step

Postby downunder » Sun Aug 21, 2016 2:59 am

jcres wrote:Thanks, Junk Supply was a great tip! Placed one order right away there. I am from Finland and nice to see that there is a shop "almost around the corner". :)

Heh, if you posted this earlier I was working in Helsinki and would bring it to ya :)

The product is named Duraclear and manufactured in France by socrep.com

Other product is made in Austria by isosport, and this is a TPU sold via junksupply as I understand.

Either way, it is a bugger to apply on the board without a press...


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