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Flexy board

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Danydan
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Flexy board

Postby Danydan » Wed Feb 05, 2014 2:19 am

I made my first board last year (10.5mm A600 Corecell with 3 layers of fiberglass cloths each side) and even though it felt way too flex I did try it and it confirmed my doubts!!! The board is ''rideable'' but I can't edge too much so it's near impossible to jump with it.

My question is then what are my options???

I do have access to fiberglass cloths for free even though I do not know how many oz it is... Will another 3 layers on each side will make a big difference? It should be noted that the board (135X41) is really light compared to the board I used as a template (Cabrinha Custom)...

More layers of fiberglass cloths will definitely be the cheapest option but I am open to any other sugestions.

Thanks in advance.

Dany

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Re: Flexy board

Postby plummet » Wed Feb 05, 2014 3:08 am

First up. Cloth ie fibres running at 90/0 is an inefficient way to layup a board.

You should use triaxle or a combo of uni-directional and double bias.

Get some 400gm uni. slam a layer on the bottom. Test it. if it needs more slap a layer on the top.

Alternatively. You could consider using triaxle in the middle half on the board top bottom tapering out toward the tips. This will give you a stiffer center section and retain flexable tips that may give you a more progressive feel than a simple uni layer over the whole board.

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downunder
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Re: Flexy board

Postby downunder » Wed Feb 05, 2014 2:11 pm

Define flex please? :)

My thinking board is like a spring, ie. a pen spring. Does a spring fly in the air when bent and released?

Same with a board. But, your corecell hasn't got any elasticity and that is a problem. My bamboo board is like a spring. The elasticity of my board will slingshot you in the air like a soft snowboard.

I am 59kg dry, for sure a springy board for a 100kg rider should be a quite different elasticity.

Do what Plummet suggested only if you didn't varnish your board. If you did, too bad. Epoxy won't bond any more.

D.

PS

It would be interesting to know more about wobbly and high elastic boards. Modulos of elasticity are different for every material and I do think more elastic boards are better for big air. Also more forgiving for a knees and ankles.
If the biggest air is with a stiff board, fair enough. But can one one be sure if never tried an elastic board in the same conditions? Plummet?

Just my 2c.

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Re: Flexy board

Postby sijandy » Wed Feb 05, 2014 2:47 pm

plummet wrote:First up. Cloth ie fibres running at 90/0 is an inefficient way to layup a board.


When you say fibres running at 90/0, do you mean for example, laying one cloth with the fibres running the length of the board (90deg) and then the second layer with the fibres going across (0deg) creating a kind of lattice? What is the most efficient way of laying the glass? Might have to bust out Paint and do some diagrams to explain myself better.

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Re: Flexy board

Postby downunder » Wed Feb 05, 2014 3:53 pm

This topic of laying a FG has been touched many times:)

Brokite explained in details using it with a closed cell cores. However, different cores diff laying...:)
The only way to have a concave in place is 90 degrees FG, me thinks (other than thinning a core). If your concave depends on 60 degrees (or any <90) triax than really the epoxy is taking a load. Not a FG.

Triax in orthogonal application is not a stable structure. Only when used with min. 2 layers, again one layered on 90 and one on 0. Which is basically 90/0 + the rest of triax cloth:)

Think of triax like a accordion instrument. It can be stretched. Slap how many you like on it and still can be stretched. But, lay one more on 90 and bingo!

Triax for torsional application is good tho. Heavy but good.

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Re: Flexy board

Postby plummet » Wed Feb 05, 2014 8:44 pm

glass angles.jpg


Ok bros.

Here's a quick picture. Imagine the oval as a board.

When you orientate fibers a board build you need to consider the direction of the fibres.

fibres running at 0 will stiffen the board up.
fibres running at 90 will hold concave
fibres running at on the angle 45-20 deg(I think tip to tip is best) will give you torsional stiffness.

You need minimal fibres running at 90 deg. one thin layer top and bottom will work. The majority of your layers should be running at 0 with some layers on the angle for torsional stiffness.

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Re: Flexy board

Postby plummet » Wed Feb 05, 2014 8:50 pm


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Bigdog
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Re: Flexy board

Postby Bigdog » Wed Feb 05, 2014 11:39 pm

10mm core and 20oz triax each is a pretty good ride for most people. The triax has more fibers running long axis and being flat is better than weave stuff.

My 135x41, corecell with 20oz triax and 7oz texalium both sides is stiffer than a shinn monk for reference.

Stan

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Re: Flexy board

Postby tkettlepoint » Thu Feb 06, 2014 3:00 am

stan you pressing your boards or vacuum ? Seen some of them and are real nice. one of these times when I am up your way will let you know.

we use 20 oz triax on top and bottom with a 6oz glass
Do full wood, wood\corecell. corecell cores depending on what a person wants.

Terrie
www.jellyfishboards.com

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Re: Flexy board

Postby Bigdog » Thu Feb 06, 2014 4:00 am

Hi Terry
Ask Jim.
I have a bigASS airbag press in a I-beam frame. Really makes good composite fiber/resin ratios and finish all in one.

Big snow here now..ya!

Stan


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