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Pocket board building

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thewindego
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Re: Pocket board building

Postby thewindego » Sun Feb 02, 2020 4:05 pm

One layer of 650g/m2 carbon is plenty tough.

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Re: Pocket board building

Postby merl » Mon Feb 03, 2020 3:38 pm

PrfctChaos wrote:
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).
Interesting comment. It seems that many production boards mix some carbon and some glass, as do many of the builds posted here. What is the consequence of carbon "taking all the load". It almost sounds like you are implying that 2 regular glass and one carbon layer could be weaker than three regular glass layers - which does not seem so intuitive...

thewindego
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Re: Pocket board building

Postby thewindego » Mon Feb 03, 2020 3:50 pm

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merl
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Re: Pocket board building

Postby merl » Mon Feb 03, 2020 3:56 pm

This explains it all very well - and answers my question exactly:
"Mixing different fibres in the same load path can lead to a component being weaker than it would be if only one type of fibre had been used."
Last edited by merl on Mon Feb 03, 2020 4:04 pm, edited 1 time in total.

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RalfsB
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Re: Pocket board building

Postby RalfsB » Mon Feb 03, 2020 4:01 pm

PrfctChaos wrote:
Sun Feb 02, 2020 12:02 pm
... I still believe a mix of glass and carbon is worst layup...
For some boards I have used a thin and light glass cloth on the top of carbon so that during sanding I do not damage the carbon layer.

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Re: Pocket board building

Postby PrfctChaos » Tue Feb 04, 2020 12:29 am

merl wrote:
Mon Feb 03, 2020 3:38 pm
PrfctChaos wrote:
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).
Interesting comment. It seems that many production boards mix some carbon and some glass, as do many of the builds posted here. What is the consequence of carbon "taking all the load". It almost sounds like you are implying that 2 regular glass and one carbon layer could be weaker than three regular glass layers - which does not seem so intuitive...
Yea bud, two glass and one carbon is basically as strong as one carbon (since the glass cannot take the load, stiff carbon takes it all).
3 glass shares the load between the 3 glass layers.
Also, interesting to note that carbon isnt really stronger than s-glass fibreglass. But much stiffer and lighter, so I like the reactive, stiff feel of a carbon foil board. Even though a s-glass only layup would be stronger and tougher.

If interrested in the hows and whys, should be able to find good info on the interwebs if you search for terms like:
Composite beam bending
Composite material properties: strength, stiffness, toughness

This guy makes a comprehensive videocomparing, carbon, s-glass, e-glass and kevlar. Explaining the mechanical properties well as well.

The guy fron Tech ingredients also makes a good vid and knows his stuff and explains how composite beams work very well.

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Re: Pocket board building

Postby Tone » Wed Feb 05, 2020 11:17 am

thewindego wrote:
Sun Feb 02, 2020 4:05 pm
One layer of 650g/m2 carbon is plenty tough.
I literally about to laminate my board and was going to use 2 layers of 650g/m2 carbon for the bottom of my board. I weighed it up for epoxy measuring and it's heavy.

Are you sure I can get away with just one layer? I will have a second layer only around the mast foot. The core of the board is Corecel.

Cheers
tony

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RalfsB
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Re: Pocket board building

Postby RalfsB » Wed Feb 05, 2020 1:23 pm

Tone wrote:
Wed Feb 05, 2020 11:17 am
thewindego wrote:
Sun Feb 02, 2020 4:05 pm
One layer of 650g/m2 carbon is plenty tough.
Few years ago I built a pocket board using XPS foam, layup was 2 layers of 200 gram/m2 carbon cloth on the top, one layer on the bottom, additional patches around the built-in KF-box. It was light and strong.
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Re: Pocket board building

Postby tomtom » Wed Feb 05, 2020 1:26 pm

you must state board thickness - it is most important variable - without it info about laminate is meaningless. Thicker the board the less laminate and vice versa.

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Re: Pocket board building

Postby thewindego » Wed Feb 05, 2020 1:59 pm

Hi Tone I made 4 hf boards so far with 19mm corecell m80. Layup 1 layer 650gm/m2 plus uni in selected area both sides. Also a pre-layed up plate in mast are recessed into bottom. That serves purpose of insert alignment and additional strength. All boards held up so far. One guy in particular rides his 109 a lot. The 650gm is not nice to wrap rails but can be done if carefull and vacuum bagging with all the tricks. As you have done weighing all the components before hand you get a really good estimate on what the final weight should be. I can predict to within 0.1kg using the area in boardcad and then calculate skin weights etc.
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