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My second Build (paulownia)

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Timmm
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My second Build (paulownia)

Postby Timmm » Tue Apr 24, 2018 9:12 pm

Hi all,

This is my second kiteboard build, but my first decent one!
I bought a paulownia core and designed my own shape (136X42) with wide tips.
The centre is 10mm and wil decent to 4 or 5 mm at the tips.

Today i routed the outline etc. and poured the rail and fin holes with epoxy.

So i was looking on the internet to find some information for the layup, but i find alot of different lay ups from 200gr FG up and downside to 600gr triaxial on both sides.

I want to end up with a medium flex and be able to ride the board with boots.

What layup would i use???


Thanks already
Attachments
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fluidity
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Posts: 105
Joined: Sat Mar 19, 2016 11:20 pm
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Local Beach: Ngati Toa, Plimmerton, Titahi Bay, Waikanae, Petone, Seatoun, Lyall Bay, Eastbourne, Lake Wairarapa
Style: Wave, jump
Gear: Old Flexfoil 9, Switch Element V4 11m, Ocean Rodeo Prodigy 7m 2014, Nitro14m v6, Nitro9m v6 12mSwitch Legacy2
DIY CAD ultra-concave wave twintips 1500 and 130mm with my own fin designs. Easy upwind, awesome carving.

Re: My second Build (paulownia)

Postby fluidity » Thu Apr 26, 2018 10:34 am

Timmm wrote:
Tue Apr 24, 2018 9:12 pm
I want to end up with a medium flex and be able to ride the board with boots.
What layup would i use???
I haven't got much experience in controlling flex but I think I can still help.
The big shock loadings are going to be between your feet and extending forward and back from them.
When you land (the biggest shock to the board) the tips lift and the centre lifts. As they lift, the bow shape resists bending on toeside and heel side edges.
Just under your heels but on top of the board the forces are compression. These forces spread sideways, becoming weaker towards the ends.
Between your heels and on top of the board are tension forces. Under the board everything is reversed.
If you place strengthening with clear boundaries then the boundaries also become highly stressed regions.
Composites gain strength from the skin surfaces. Stiff fabrics sandwiching soft fabrics resist both puncture and deformation. Sandwiching a stiff fabric between soft fabrics is a waste unless you are trying to get flexibility.
Don't skin with an outer surface like kevlar, polyester or innegra, it will fray if damaged when sanded.
Zigzag your fabric boundaries if you are zoning the composites, this will merge an easy bending zone into a stiff area more softly and soften stresses.
Think about where you want flex, DON'T use carbon where you want flex except maybe on the inside of your intended curve.
Glass and s-glass, basalt are all more stretchy than carbon. Kevlar and Innegra too though they have very little compression strength.
kevlar/carbon and innegra/carbon weaves look pretty but aren't as effective as sandwiching innegra or kevlar between carbon.
For a 10mm thick board my gut feel is that a couple of layers of 200 or 300 oz glass top and bottom would be close to strong enough, but I'd probably run a strip of unidirectional 150mm wide carbon on top between the heels and extending another 150mm past each heel. To reduce the risk of cracking the underside i'd look at either a bit more glass or sandwiching some innegra cloth between underside layers of glass. And I'd zigzag the ends of the carbon on top.

Keep in mind for your flex response that further out to the tips you hardly need any strength as there is no wood past the ends to apply force near the edges, you only need material there for abrasion resistance.

A good reinforcement in line with your heels is most important, then of lesser importance is a skin to keep the rest of your paulonia aligned and free from buckling.

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downunder
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Re: My second Build (paulownia)

Postby downunder » Thu Apr 26, 2018 2:49 pm

^
Whow:)

Coz Im 60kg, and riding 120cm Paulownia diy board which u can find on this forum, I’ll be quiet :) everything is there, right in front of you as MattV would say :)

Here:

viewtopic.php?f=107&t=2387451&hilit=New+year+board

I will just say that boots and Paulownia is not the best no matter of reinforcement.

And, fluid mate, you are over thinking:) I have customers paying big bucks for the beauty of Pwood, with no carbon bs. Wood is a God given in its own right, respect it as such.

Or, use a foam and go wild :) nothing wrong with this.

fluidity
Medium Poster
Posts: 105
Joined: Sat Mar 19, 2016 11:20 pm
Kiting since: 2016
Local Beach: Ngati Toa, Plimmerton, Titahi Bay, Waikanae, Petone, Seatoun, Lyall Bay, Eastbourne, Lake Wairarapa
Style: Wave, jump
Gear: Old Flexfoil 9, Switch Element V4 11m, Ocean Rodeo Prodigy 7m 2014, Nitro14m v6, Nitro9m v6 12mSwitch Legacy2
DIY CAD ultra-concave wave twintips 1500 and 130mm with my own fin designs. Easy upwind, awesome carving.

Re: My second Build (paulownia)

Postby fluidity » Fri Apr 27, 2018 2:43 am

downunder wrote:
Thu Apr 26, 2018 2:49 pm
Coz Im 60kg, and riding 120cm Paulownia diy board which u can find on this forum, I’ll be quiet :) everything is there, right in front of you as MattV would say :)
I will just say that boots and Paulownia is not the best no matter of reinforcement.
And, fluid mate, you are over thinking:) I have customers paying big bucks for the beauty of Pwood, with no carbon bs. Wood is a God given in its own right, respect it as such.
Some cuts :D
You have a point about rider weight. I have a high concave 6mm thick paulonia board with double 200mm glass and polyester that I buckled in a low jump but then I have 1.5m and 1.3m boards I can land 9m jumps in (sometimes over 5G landing) that are also concave tapering from max 15mm.
If a whole board can flex (unlike concave) it's different though. And I'm 98kg!
Definitely reinforce around foot straps and out to the sides a bit though! I don't think landing footstraps or boots are much different on the G forces but you are more likely to bust a boot out than a foot strap.

Timmm
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Joined: Tue Apr 24, 2018 8:50 pm
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Local Beach: Workum, Strand horst, The Netherlands
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Re: My second Build (paulownia)

Postby Timmm » Sat Apr 28, 2018 7:51 pm

Thanks for the reply's!

I have done some further inverstigation and i think that i will go with 600gr (22oz) triaxal glasfiber on both sides, maby with an extra patch of 200gr keper under de pressure point of the boots/straps.

My only concern is that the board may get to stiff with my 80Kg but i think it will be okay.

Her another picture of the process so far.

Upcoming week i'm going to taper the tips and side rail
uitgezaagd.jpg


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