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Kiteboard build - lamination help

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TomBoy
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Kiteboard build - lamination help

Postby TomBoy » Tue Dec 06, 2016 11:46 am

Hi everybody, thanks websites like that I decided to build own Twintip boards. My goal is Two boards paulownia/red cedar core.
One is 143x43cm(4-12mm thick) another 138x41cm(3-9mm thick).
IMG_20161008_185430.jpg
What I wanna do is carbon fibre and aramid-carbon fibre buttom layer and nice transparent fibre glass on top.
Bigger board I want softer smaller board tougher.
I have already carbon fibre (200g/m2 and 160g/m2) and aramid-carbon fibre(190g/m2).
fibre.jpg
fibre.jpg (91.77 KiB) Viewed 1175 times
Fibre glass I'll buy according to advice.
So my big question is how layers setup should looks like?
For bigger board I want aramid-carbon on buttom layer smaller board I wanna go with carbon.
I'll be happy for expert advice - THX

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Re: Kiteboard build - lamination help

Postby plummet » Tue Dec 06, 2016 6:49 pm

Have you worked with Kevlar before? its a shit to sand and work after layup. Goes all fluffy. I'm not convinced you need Kevlar for abrasion resistance on a kiteboard.
check out nomad kiteboards. They layup is pretty visible.
I'd role with

Here's my suggestion

top
300gram glass matt at 0/90
Thin carbon uni stringers as per nomad kiteboards
core
200gm uni running at 0
200gm carbon twill at 45's

tapered Core thickness 2mm at the tips, 8mm center

http://www.nomadkiteboarding.com/

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downunder
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Re: Kiteboard build - lamination help

Postby downunder » Wed Dec 07, 2016 5:18 am

Why advertising Nomad is unknown to me. Have never ridden or seen one at all.


However, I've built quite a few P.wood boards (as you can see on this forum), and this is my experience:

- Absolutely no need for carbon or kevlar. A carbon stringer yes, looks aesthetically pleasing, but questionable as for strength on top. You also have a nice cedar wood, so based on P. suggestion, you'll loose appealing look of your already very nice build. This boards can easily fetch a value of $700 as hand made, if and only if done properly (meaning ultra shiny varnish). Why ruin it with c/k.

- hence, 200g UNI on top. If really need a carbon, stick UNI tape between 2 cedar strips (wider area). I started using the same carbon tape as TomW. Pro look.
- 120 biax on bottom. If you use 200g UNI, you'll get a bulldozer board.

12mm core is tough as. 9mm might not be that stiff, maybe using 200 UNI for bottom. But, you need to tell us your body weight.

Tapered 2mm at tips? I strongly disagree. 8 mm center? What for? Crazy...Plummet, dare to explain? Do you actually own or ridden paulownia w. board 8mm at centre? Coz i do own a Youri Zoon Pro.

Ps

How will you do the inserts? It would be a shame to use anything than industry standard for this....

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Re: Kiteboard build - lamination help

Postby plummet » Wed Dec 07, 2016 6:25 am

I linked the nomad site because it shows the layup. Something you can't see on most production boards.

Why thinner? If your rolling with carbon then why not take advantage of the additional stiffness with a lighter thinner,stronger board with nice flex characteristics?

I agree if your running 12mm core the full 200g unit on the bottom would be overkill.

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Re: Kiteboard build - lamination help

Postby downunder » Wed Dec 07, 2016 6:55 am

Nomad boards are rare like a hens teeth at my local. Have no idea how they ride.

2mm carbon on tips is brittle as. One drop from only 30cm on a floor and will break. The full carbon board might be very light, so it doesn't break when dropped.

However, the 143x43cm with your layup will make a =>4kg board. That is not light. Using kevlar will make it darker over time since not UV stable (even with heaps of UV varnish). Using a wide carbon is very, very difficult since it will open some threads and expose the wood underneath. It also 'drinks' epoxy. The middle pic carbon is useless as well as right pic kevlar coz used only for curved 3d shapes in multiple layers (say 5-10). Good you posted this pic's tho, so we can comment. This is the real experience answer.

8mm tapered in centre does not edge well at all without the boots.

The bigger question for TomBoy is a springback tho.

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Re: Kiteboard build - lamination help

Postby plummet » Wed Dec 07, 2016 9:26 am

downunder wrote:Nomad boards are rare like a hens teeth at my local. Have no idea how they ride.

2mm carbon on tips is brittle as. One drop from only 30cm on a floor and will break. The full carbon board might be very light, so it doesn't break when dropped.

However, the 143x43cm with your layup will make a =>4kg board. That is not light. Using kevlar will make it darker over time since not UV stable (even with heaps of UV varnish). Using a wide carbon is very, very difficult since it will open some threads and expose the wood underneath. It also 'drinks' epoxy. The middle pic carbon is useless as well as right pic kevlar coz used only for curved 3d shapes in multiple layers (say 5-10). Good you posted this pic's tho, so we can comment. This is the real experience answer.

8mm tapered in centre does not edge well at all without the boots.

The bigger question for TomBoy is a springback tho.
Well I guess we beg to differ. My theory is more reinforcement and less core provides stronger ride that still retains good flex characteristics. When you increase the core you increase stiffness but at the detrement of strength. The thinner board with more reinforcement will flex more before it fails and fail well after the stiffer thicker core fails due to its lower ability to flex.

But thinking about Toms layup and considering he wants glass on top. I think you are right. 8mm core will not work with a glass top layer. the top glass layer wont be stiff enough to match the stiffness of the bottom carbon layup. So 10-12mm core would be the go for a mismatch layup. Bottom only carbon layup will provide some additional stiffness over and above glass only. But really without the top to support it, it becomes a cosmetic function rather than a stiffness function.

Why would an 8mm tapered center core not edge as well as a 12mm if you ended up with a similar stiffness? This is the advantage of carbon. If gives approximately 30-50% additional stiffness for the same weight cloth. You can use less weight cloth top achieve the a similar result. Or you can use less core thickness and the same amount of cloth to achieve a similar stiffness.

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Re: Kiteboard build - lamination help

Postby downunder » Wed Dec 07, 2016 10:22 am

Yes, we do.

I know the stiffness numbers. And I know how strong my 12mm Paulownia board is with just 120g biax FG on bottom and 200g UNI on top (+ carbon tape). Less than 2kg board.

"The thinner board with more reinforcement will flex more before it fails and fail well after the stiffer thicker core fails due to its lower ability to flex." - this is only true for a foam boards. Using wood completely changes a picture. Using balsa and jarrah is not the same, I hope we agree on that.

But back to helping this guy, I think the inserts position on cedar wood is not great. Cedar we have here is a way more softer than P. wood. Consider reinforcing your inserts with at least 2 layers of FG, to protect the inserts pulling out (not so much pulling but making them loose and letting the moisture in).

D.

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Re: Kiteboard build - lamination help

Postby plummet » Wed Dec 07, 2016 11:18 am

downunder wrote:Yes, we do.

I know the stiffness numbers. And I know how strong my 12mm Paulownia board is with just 120g biax FG on bottom and 200g UNI on top (+ carbon tape). Less than 2kg board.

"The thinner board with more reinforcement will flex more before it fails and fail well after the stiffer thicker core fails due to its lower ability to flex." - this is only true for a foam boards. Using wood completely changes a picture. Using balsa and jarrah is not the same, I hope we agree on that.

But back to helping this guy, I think the inserts position on cedar wood is not great. Cedar we have here is a way more softer than P. wood. Consider reinforcing your inserts with at least 2 layers of FG, to protect the inserts pulling out (not so much pulling but making them loose and letting the moisture in).

D.
Your 12mm paulownia board with just 120 of fg and 200 uni on top will be stiff but it wont be strong. It will fail when over flexed well before my thinner cored boards. Well before. But if it doesn't break then who cares if its not as strong!..

I agree that the core changes the flex characteristics. Its real good if the core flex ability is matched to the reinforcement. But the underlying principle of thicker core = stiffer but reduced ability to flex and more prone to failure if over flexed remains the same. Increase the core increase the stiffness with the reduction of the ability to flex.

A graphic example is the landboards I've build 8mm total thickmess. One glass core carbon outer, the other bamboo carbon. Both boards can flex 130mm bottom out on the sand and flex back without breaking. A 13-15mm glass/ply mbs lanboard will snap if it is flexed half of that.

I haven't used cedar so I can't comment on the inserts used.

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Re: Kiteboard build - lamination help

Postby downunder » Wed Dec 07, 2016 2:38 pm

Cmon Plummet,

you know well as I do that bamboo properties are way different, why arguing about that.

Funny you say that, did you actually used Paulownia? ;)

Even an I-Beam will fail when over flexed. This is not a rocket surgery (ouch, a science). This depends on modulus, I would know since have a BSc in Civ Eng.

When you edge hard, and I mean really hard, like board almost vertically, where is the stress on the board? When you jump, where is the stress on landing (providing not landing flat, but one tip first)?

I wonder...

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Re: Kiteboard build - lamination help

Postby TomBoy » Fri Dec 09, 2016 10:43 am

Hey its me again, thanks for replies and opinions.
To Downunder I know you know.. I saw some your posts before I started with project and it was already useful. I wish to read post with Smooth-Cast earlier before I've filled my edges straight with it. (I was f... disaster :-D ) But anyway I'm smarter now.
So I wanna use carbon because I have it and I like the look. My goal is something like this.
bruce board 2.jpg
bruce board 1.jpg
Carbon boards are on markets anyway and If I use it carefuly I can get some flex as well. Correct me if I'm wrong.
I'm 80kg there might be some room for carbon.
I'm thinking to put 200g glass on top and 200 carbon on bottom or something like that.
Or what would be your setup just with Fglass for these two boards?
And spring back is other think what i need discuss. So how many percent of spring back do you think I get? For bigger board I wanna do 60mm rocker table and if spring back will be 30mm I would be happy with it (its gonna be more light wind board). Smaller board I want around 45mm rocker so...

THX for constructive responses.


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