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Pocket board building

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max
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Re: Pocket board building

Postby max » Sat Feb 01, 2020 1:36 am

hi Kiterisland . . .

nice board. I would recommend sanding the board roughly before glassing to allow best bond. Use 40 or 60 or 80 grit paper.


Can you explain your process up to getting the board shown in the pics?

Cut the xps into strips.

Glue with ?

Put together with stringer . . . on a rocker table?

Kiterisland
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Re: Pocket board building

Postby Kiterisland » Sat Feb 01, 2020 11:21 pm

Thanks guys. I rounded the bottom edges a bit more and roughed them up with 60grit. Hope it bonds ok. Made another board today with just 1/4 stringer, comes in at 1.25lbs. Curious how much glass will add.

To answer your question I did it in a pretty ghetto way. I printed the profile in vinyl and made stinger out of that. Cut and glued (tiny bit of wood glue) foam in same profile then sanded just a little bit to make it flat. This way no rocker table or anything is needed.
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Trent hink
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Re: Pocket board building

Postby Trent hink » Sun Feb 02, 2020 1:07 am

Xps bonds fine, the problem with it is that is has a very low shear stength.

So if the board has any flex the foam will shear right at the foam-glass interface.

If you can make the board stiff enough, it might not be a problem, but that means using heavy reinforcement.

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Re: Pocket board building

Postby Kiterisland » Sun Feb 02, 2020 1:43 am

Trent hink wrote:
Sun Feb 02, 2020 1:07 am
Xps bonds fine, the problem with it is that is has a very low shear stength.

So if the board has any flex the foam will shear right at the foam-glass interface.

If you can make the board stiff enough, it might not be a problem, but that means using heavy reinforcement.
I will be using old material that have on hand. 2x6oz fibreglass 1x8oz carbon on both top and bottom, along with a laminate bulker sheet on the top. That should be stiff enough no?

max
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Re: Pocket board building

Postby max » Sun Feb 02, 2020 1:48 am

Kiterisland wrote:
Sun Feb 02, 2020 1:43 am
Trent hink wrote:
Sun Feb 02, 2020 1:07 am
Xps bonds fine, the problem with it is that is has a very low shear stength.

So if the board has any flex the foam will shear right at the foam-glass interface.

If you can make the board stiff enough, it might not be a problem, but that means using heavy reinforcement.
I will be using old material that have on hand. 2x6oz fibreglass 1x8oz carbon on both top and bottom, along with a laminate bulker sheet on the top. That should be stiff enough no?
Yes . . .

I have used 3 x 6onz E glass on the bottom wrapping rails also and it has been fine but have also done the 2x6onz E and a 6onz Carbon.

What do you mean by laminate bulker sheet?

It is good to protect the top from heel dents as that would cause delam also.

Thanks for the extra pics

Kiterisland
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Re: Pocket board building

Postby Kiterisland » Sun Feb 02, 2020 2:07 am

max wrote:
Sun Feb 02, 2020 1:48 am
Kiterisland wrote:
Sun Feb 02, 2020 1:43 am
Trent hink wrote:
Sun Feb 02, 2020 1:07 am
Xps bonds fine, the problem with it is that is has a very low shear stength.

So if the board has any flex the foam will shear right at the foam-glass interface.

If you can make the board stiff enough, it might not be a problem, but that means using heavy reinforcement.
I will be using old material that have on hand. 2x6oz fibreglass 1x8oz carbon on both top and bottom, along with a laminate bulker sheet on the top. That should be stiff enough no?
Yes . . .

I have used 3 x 6onz E glass on the bottom wrapping rails also and it has been fine but have also done the 2x6onz E and a 6onz Carbon.

What do you mean by laminate bulker sheet?

It is good to protect the top from heel dents as that would cause delam also.

Thanks for the extra pics
Good to know
This here...
https://shop.compositescanada.com/#/product/1480-1-LY

PrfctChaos
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Re: Pocket board building

Postby PrfctChaos » Sun Feb 02, 2020 7:17 am

It doesnt make much sense to mix glass and carbon in same layup. If you do want to mix (or want to finish the material you have) I would recommend only using catbon on top of board (tension skin) and only glass on bottom surface (compression skin). Difficult to explain all the whys, but carbon is better in tension than compression. And with the bending axis moving to close to top skin (due to stiff carbon), the glass will see lower load.

If you mix carbon and glass, then the glass will do nothing but add weight and what little carbon is there takes all the load (due to high stiffness).
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jaros
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Re: Pocket board building

Postby jaros » Sun Feb 02, 2020 7:43 am

PrfctChaos wrote:
Sun Feb 02, 2020 7:17 am
I would recommend only using catbon on top of board (tension skin) and only glass on bottom surface (compression skin).
But it is not allways that the top of the board is only under tension, is it? I heard of many reports that the board broke while hitting the water hard at tuchdowns. In this case the bottom is under tension.
The best thing imho is to build top and bottom skin in the same layout.

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Re: Pocket board building

Postby PrfctChaos » Sun Feb 02, 2020 12:02 pm

That might be the case, I was only thinking of riding along on the foil. I still believe a mix of glass and carbon is worst layup, especially with only a small amount of carbon, just glass would be better.

Best thing in my opinion is to use only carbon, top and bottom, for max stiffness.

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Re: Pocket board building

Postby downunder » Sun Feb 02, 2020 2:59 pm

jaros wrote:
Sun Feb 02, 2020 7:43 am
PrfctChaos wrote:
Sun Feb 02, 2020 7:17 am
I would recommend only using catbon on top of board (tension skin) and only glass on bottom surface (compression skin).
But it is not allways that the top of the board is only under tension, is it? I heard of many reports that the board broke while hitting the water hard at tuchdowns. In this case the bottom is under tension.
The best thing imho is to build top and bottom skin in the same layout.

This would be correct however one single carbon layer is not enough.

And Ive seen a lot of carbon TTs broken due to that ;)

It is not tension where the problem is, but the stress point that might be anywhere due to impact point.


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