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Mark _australia said..

I knew I should not have said it. Yes Windman I know who Bourke is and I know his boards are beyond great. I'd love one (or 3)

In my very humble opinion though, 20-30x stronger is a big claim. For example how much can you put on the footpad area of a normal waveboard before it crushes? About 200kg? So Witchcraft can show 4 tonnes on that small area.....? Sounds a bit rich.

If the engineer calculated it, all good I will shut up.

The strength calculated is rigidity against flexion of that area. The difference in force that they can handle will be smaller but the amount the construction flexes each time will be different, hence fatigue will start much sooner. EPS is quite bad for fatigue.
https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcSP9RmKAYG-_y3qmOa6mPO6nq-tgA0xc5SEeaePSf3SEC8s6B_R8g
This is stuff that any boardshaper should know:
www.diabgroup.com/en-GB/Sandwich-technology/Introduction/The-sandwich-principle

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Witchcraft said..

..................... hence fatigue will start much sooner. EPS is quite bad for fatigue.

Witchcraft, what are your thoughts (or even experience) in using XPS in lieu of EPS for the core?

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sausage said..

Witchcraft said..

..................... hence fatigue will start much sooner. EPS is quite bad for fatigue.

Witchcraft, what are your thoughts (or even experience) in using XPS in lieu of EPS for the core?

XPS is pretty much unworkable IMO. There is practically no flex in it at all and it is so fine it hardly bonds so on any impact, the XPS gets a dent and the laminate pops back leaving a void below. Ive repaired XPS boards and when you sand the crack there is hollow space below it and extending a long way beyond the crack. EPS is OK for its weight. But you cant rely on it too much to support the sandwich. You need to limit its flex it will have to take. Just occasionally to take an impact is fine but a constant movement will lead to fatigue. To do this youll need to spread the force over a bigger area and to do this, you will need rigidity against flex of the composite sandwich construction.

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Witchcraft said..
Only that the proportions of the mast needed to be adapted to the properties of carbon. Hence a RDM.
When I moved to Fuerte 20 years ago, the first 2 years I snapped about 15 SDM masts of any make or type. Becoming desperate I then ordered some Powerex RDM masts from the US and they lasted 2 years.

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Witchcraft said..

Man0verBoard said..

Thanks Bourke, I disagree about carbon performing well under compression. E-glass has about the same compressive strength.
From what I understand about carbon in relation to masts, the work the carbon is doing is more about controlling the flex characteristics and optimising the strength to weight ratio - the saving in weight albeit marginal, and more dynamic reflex is at the sacrifice of some strength and durability.
No?

I do not know the exact compressive strength of carbon or glass but I am sure that carbon is quite a bit stronger. Maybe creasing/buckling strength is the better word instead of compression.

Just to clarify - the optimisation to the current RDM is the perfect example because carbon performs relatively poorly under compressive/buckling/creasing loads. Nolimitz also puts additional fibre(other than carbon) reinforcement at areas at risk of compression damage. Hence their masts are 91% carbon.

^^^ agreed and I think some of the confusion is when people talk about compression when they mean standing on the deck. "Carbon heel patches prevent heel dents as they prevent compression" - yes. "the carbon works well in compression" - no not the right term. When a board flexes, because it has thickness, one side is in tension and the other in compression. Carbon does not perform well in compression (brittle)

The fact 100% race masts break with monotonous regularity and RDM's don't should show that there is other things going on, you don't just make something with carbon and therefore it is good

actually both sides of the board have tension. what you mean is that one side of each sandwich is in compression. that is why sandwich laminates are used.

heel dents to me are impact dents. carbon is not that great with withstanding impact forces. there are many other better materials

alot of general & partially incorrect being thrown around here about the forces involved- carbon performs well in compression but where it fails is when shear loads are applied to it, the angle at where the fibres break is much lower than glass & pe fibres, carbon not the best choice for impact & point load areas. In masts the rdm is stronger as each of the fibres that break are better supported due to increased wall thickness & changed angles of overall diameter. Apparently the resin itself goes a long way in causing the break in the carbon & this is why actual 100% carbon (no bonding agent) is being developed.

witchcraft understand the above & it can be seen in the comparison test vid- stretch of the fibres, bend/angle of the fibres with tying the knot. Where the dyneema will fail which he didn't show is when a shock load is applied (snap the fibres taut) & it will break at alot lower point than any of the other tests. This is irrelevant to windsurfing boards though as we don't apply that type of load.

Dyneema vs Innegra vs Spectra vs Kevlar- each was developed for specific purpose or by different companies, some would have pulled apart the data sheets but it'd selection of use would probably come down to price, availability, workability & health risks. Innegra being used in cobra boards likely addresses price only, they wouldnt care about health, are big enough that anything is available etc. I think it would be difficult for a punter to go i want a board made with kevlar rather than dyneema as i cant imagine people reading & understanding the data unless it's your livelihood.

Dare I pull the tigers tail and mention Vectra...

exactly, there are many different polymers (not just pe) which could be used & are better suited to the purpose. Most will stick to glass & carbon as they are easy to work with, cheap, well known & relatively safe (breathe in either being sanded then good luck with the emphysema, blood vessel & organ damage later in life).

The whole advantage of sandwich is put what you need where it's needed- overall the board has compression/tension on the skin, shear/point load from impacts/feet & torsion/bending from rider, fin, mfp & chop. No one type of cloth will achieve all of that. For us to get better gear we need more witchcraft & peter ross's who experiment & understand & dont just churn out the same old mass produced crap which we seem to be happy with, thank god the prices havnt increased that much in the last 20 years.

I replied above because as a community we believe marketing rubbish & little things incorrectly applied. 20 years ago we could buy a sub 5 kg board, you'd sail it some would last years, some a year depending who made. Now we believe sh!t like we sand our finishes for optimal weight saving, what a load of bs- they were not applying 30 coats, the sub 5kg boards of 20 years ago had full paint. The bloody paint is roughly finished as to achieve something like mistrals is time which to some is $ wasted- a whole 5c of third world child labor type time.

If it wasnt for the shapes getting better the majority of production boards arent worth the money. Some people such as Gestalt (& probably me) may talk some crap, i've even told him in person but it is growing ideas & awareness, his heart is in the right place as is the shapers who bothered to reply objectively in this thread. Some contributors may not have glued together many boards but then do some say to the shapers are you a materials scientist or engineer or designer... no well you mustnt know what you are talking about, learning & paying attention to what you've seen & sailed isnt brain surgery.

It is good to see some waves being made, i watched a board making vid posted here recently & it immediately answered all of the faults i've seen & why i wouldnt own one... sad they had good shapes, couldve been the next big thing yet everyone that owned them started finding out they werent the best built boards as was claimed or full carbon as they'd been thought when they bought them as thats how they were marketed. Now i only know 1 person using them. Similar claim to fame by a wa shaper was on here recently bagging some constructions saying his was the strongest- put your money where your mouth is like witchcraft as the rather weighty flat water board i saw that creased underfoot after a few uses wouldnt substantiate those claims.

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Man0verBoard said..
Just to clarify - the optimisation to the current RDM is the perfect example because carbon performs relatively poorly under compressive/buckling/creasing loads. Nolimitz also puts additional fibre(other than carbon) reinforcement at areas at risk of compression damage. Hence their masts are 91% carbon.

Yes, they put glass fibre on the outside for impact resistance. Since glass has a much lower modulus, it does not do much for the normal loads a mast has to take. Other lower % carbon masts of other brands put the glass in between the carbon as a kind of sandwich fill to save costs. For the bending loads of a mast this is better but not as good for impact.

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Mark _australia said..
^^^ agreed and I think some of the confusion is when people talk about compression when they mean standing on the deck. "Carbon heel patches prevent heel dents as they prevent compression" - yes. "the carbon works well in compression" - no not the right term. When a board flexes, because it has thickness, one side is in tension and the other in compression. Carbon does not perform well in compression (brittle)

You are wrong, carbon is not good for shock loads (brittle) but it is good for compression load as in bending forces on the board.

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Gestalt said..

actually both sides of the board have tension. what you mean is that one side of each sandwich is in compression. that is why sandwich laminates are used.

heel dents to me are impact dents. carbon is not that great with withstanding impact forces. there are many other better materials

No, heel dents are compression forces on the outside layer, tension on the inside. It?s not impact by shock load since you do not hit the board with a speed, heels are not as hard and there is also pads to absorb any shock.

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mkseven said..
witchcraft understand the above & it can be seen in the comparison test vid- stretch of the fibres, bend/angle of the fibres with tying the knot. Where the dyneema will fail which he didn't show is when a shock load is applied (snap the fibres taut) & it will break at alot lower point than any of the other tests.

Completely the opposite. Dyneema can dissipate energy with supersonic speeds and so works extremely well for shockloads. Hence the hammer test or why it is by far the most used material for ballistic armor. It is not very good for compression, extremely good on tension loads. It also has a very long flexlife, is not effected by UV, does not absorb water like Kevlar does.

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mkseven said..

Dyneema vs Innegra vs Spectra vs Kevlar- .

Dyneema=Spectra. They are both tradenames for UHMWPE. Just like Kevlar and Twaron are tradenames for Aramid.

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Witchcraft said..

Gestalt said..

actually both sides of the board have tension. what you mean is that one side of each sandwich is in compression. that is why sandwich laminates are used.

heel dents to me are impact dents. carbon is not that great with withstanding impact forces. there are many other better materials

No, heel dents are compression forces on the outside layer, tension on the inside. It?s not impact by shock load since you do not hit the board with a speed, heels are not as hard and there is also pads to absorb any shock.

when your 110kg sailor lands his back loop flat I would say that is impact where the heels are. how that is not an impact shock to the laminate is beyond me.

fair enough that you disagree though.

Different kind of shock load, different application. Shock dyneema braid and your 50kg test will be broken by hand.

Yes HMPE's are great at energy dissipation, I can explain why at a scientific level if you don't believe me on the above.

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mkseven said..
The whole advantage of sandwich is put what you need where it's needed- overall the board has compression/tension on the skin, shear/point load from impacts/feet & torsion/bending from rider, fin, mfp & chop. No one type of cloth will achieve all of that. For us to get better gear we need more witchcraft & peter ross's who experiment & understand & dont just churn out the same old mass produced crap which we seem to be happy with, thank god the prices havnt increased that much in the last 20 years.

I replied above because as a community we believe marketing rubbish & little things incorrectly applied. 20 years ago we could buy a sub 5 kg board, you'd sail it some would last years, some a year depending who made. Now we believe sh!t like we sand our finishes for optimal weight saving, what a load of bs- they were not applying 30 coats, the sub 5kg boards of 20 years ago had full paint. The bloody paint is roughly finished as to achieve something like mistrals is time which to some is $ wasted- a whole 5c of third world child labor type time.
.

In my experience people do sail more radical nowadays than 10 or 20 years ago. The sailing level has gone up and Ive had to improve the constructions with it. The constructions that I made in those days and would last 5 or in 2 cases even over 10 years would not last half that today. My own boards were 4.2-4.5kg at some point but now they are 6.3. With more volume though.

Also in the department of production mistakes Cobra has improved a lot. The lay ups are as the brands demand but there are far less production mistakes.

But over here prices have increased quite a bit. Cobra has managed to get rid of most of their competition over the years and now with their near monopoly position they have increased pricing. Material costs have not increased much. Labor costs maybe after the strike they suffered. But where would Fanatic, RRD & Co go if they would not accept Cobras pricing? The only other option is to shut down. By going the easy way and give production out of hand, they have created this situation. What we do see over here now is more custom builders coming back. They can be competitive again.

It was more a reference to slalom and speed boards, waveboards have come a long way in some regards- 20 years ago the majority were plastic or fibreglass and either crazy heavy, snapped or 2 inch heel dings in no time.

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Gestalt said..

when your 110kg sailor lands his back loop flat I would say that is impact where the heels are. how that is not an impact shock to the laminate is beyond me.
fair enough that you disagree though.

There probably is a grey area between impact/shock/compressive loads but in this case it still is compressive load. Shock or impact would be if something would hit the board with speed coming from a distance and have at least have similar hardness as the receiving material. Basically at such speed, the energy has no time to dissapate towards the inner layer. Like what would happen if you hit it with a hammer.

what would you define as impact from a real world view.

mast blow from catapult? I've seen rigs detach mid air and the mast foot puncture the deck on landing. that has happened twice to me on my board but without any punctures occurring just a scratch.

I guess in your area rocks are a big one.

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mkseven said..
It was more a reference to slalom and speed boards, waveboards have come a long way in some regards- 20 years ago the majority were plastic or fibreglass and either crazy heavy, snapped or 2 inch heel dings in no time.

OK, I was referring to wave boards. I dont make slalom or speed boards and I dont know who owns these around here. The only time we see them is when the slalom or freestyle world cup sailors bring their boards to repair if they have started to run out.

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mkseven said..

Different kind of shock load, different application. Shock dyneema braid and your 50kg test will be broken by hand.

Yes HMPE's are great at energy dissipation, I can explain why at a scientific level if you don't believe me on the above.

Yes, please explain.

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Gestalt said..

Witchcraft said..

Gestalt said..

actually both sides of the board have tension. what you mean is that one side of each sandwich is in compression. that is why sandwich laminates are used.

heel dents to me are impact dents. carbon is not that great with withstanding impact forces. there are many other better materials

No, heel dents are compression forces on the outside layer, tension on the inside. It?s not impact by shock load since you do not hit the board with a speed, heels are not as hard and there is also pads to absorb any shock.

when your 110kg sailor lands his back loop flat I would say that is impact where the heels are. how that is not an impact shock to the laminate is beyond me.

fair enough that you disagree though.

it's both, if the sandwich was continuous then it'd be tension on opposite side of board but since it is lightly supported by low density foam there would be some tension involved on the inside of the sandwich, probably the ultimate failing point for something like the witchcraft construction would be delamination between the sandwich and core (i've seen this a bit with carbon kevlar boards).

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Witchcraft said..

mkseven said..

Different kind of shock load, different application. Shock dyneema braid and your 50kg test will be broken by hand.

Yes HMPE's are great at energy dissipation, I can explain why at a scientific level if you don't believe me on the above.

Yes, please explain.

Sure for a fee i'm all yours as I'm not digging out specifics in my spare time.

Different but much bigger industry- look into PE and aramid fishing lines, why they use shock leaders and very specific knots, why also when under tension the line has to touch something with the right radius or edge and bang gone.

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Gestalt said..

what would you define as impact from a real world view.

mast blow from catapult? I've seen rigs detach mid air and the mast foot puncture the deck on landing. that has happened twice to me on my board but without any punctures occurring just a scratch.

I guess in your area rocks are a big one.

Yes, a catapult or any hit from a hard object. Or a point load.

This was the result of a guy sailing at Jameos del Agua on Lanzarote, the launch there is pretty tricky. The guy had accumulated these over 18 months of sailing without having to repair it. If there had been a impact on the carbon in the creasing zone I would have told him to bring it in sooner.

yes this is very true. you did in fact say I could talk some crap. I still love you though.

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mkseven said..

exactly, there are many different polymers (not just pe) which could be used & are better suited to the purpose. Most will stick to glass & carbon as they are easy to work with, cheap, well known & relatively safe (breathe in either being sanded then good luck with the emphysema, blood vessel & organ damage later in life).

The whole advantage of sandwich is put what you need where it's needed- overall the board has compression/tension on the skin, shear/point load from impacts/feet & torsion/bending from rider, fin, mfp & chop. No one type of cloth will achieve all of that. For us to get better gear we need more witchcraft & peter ross's who experiment & understand & dont just churn out the same old mass produced crap which we seem to be happy with, thank god the prices havnt increased that much in the last 20 years.

I replied above because as a community we believe marketing rubbish & little things incorrectly applied. 20 years ago we could buy a sub 5 kg board, you'd sail it some would last years, some a year depending who made. Now we believe sh!t like we sand our finishes for optimal weight saving, what a load of bs- they were not applying 30 coats, the sub 5kg boards of 20 years ago had full paint. The bloody paint is roughly finished as to achieve something like mistrals is time which to some is $ wasted- a whole 5c of third world child labor type time.

If it wasnt for the shapes getting better the majority of production boards arent worth the money. Some people such as Gestalt (& probably me) may talk some crap, i've even told him in person but it is growing ideas & awareness, his heart is in the right place as is the shapers who bothered to reply objectively in this thread. Some contributors may not have glued together many boards but then do some say to the shapers are you a materials scientist or engineer or designer... no well you mustnt know what you are talking about, learning & paying attention to what you've seen & sailed isnt brain surgery.

It is good to see some waves being made, i watched a board making vid posted here recently & it immediately answered all of the faults i've seen & why i wouldnt own one... sad they had good shapes, couldve been the next big thing yet everyone that owned them started finding out they werent the best built boards as was claimed or full carbon as they'd been thought when they bought them as thats how they were marketed. Now i only know 1 person using them. Similar claim to fame by a wa shaper was on here recently bagging some constructions saying his was the strongest- put your money where your mouth is like witchcraft as the rather weighty flat water board i saw that creased underfoot after a few uses wouldnt substantiate those claims.

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Witchcraft said..

Mark _australia said..

^^^ agreed and I think some of the confusion is when people talk about compression when they mean standing on the deck. "Carbon heel patches prevent heel dents as they prevent compression" - yes. "the carbon works well in compression" - no not the right term. When a board flexes, because it has thickness, one side is in tension and the other in compression. Carbon does not perform well in compression (brittle)

You are wrong, carbon is not good for shock loads (brittle) but it is good for compression load as in bending forces on the board.

Compression is not bending.

If you bend something, one side is in tension (stretching) and the other side is in compression.

" it is good for compression load "as in bending forces on the board" " WTF? Carbon is NOT good at bending. Simple 100% fact.

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Mark _australia said..

Witchcraft said..

Mark _australia said..

^^^ agreed and I think some of the confusion is when people talk about compression when they mean standing on the deck. "Carbon heel patches prevent heel dents as they prevent compression" - yes. "the carbon works well in compression" - no not the right term. When a board flexes, because it has thickness, one side is in tension and the other in compression. Carbon does not perform well in compression (brittle)

You are wrong, carbon is not good for shock loads (brittle) but it is good for compression load as in (to withstand the) bending forces on the board.

Compression is not bending.

If you bend something, one side is in tension (stretching) and the other side is in compression.

" it is good for compression load "as in bending forces on the board" " WTF? Carbon is NOT good at bending. Simple 100% fact.

Sorry I did not explain that very well. I should have said: Carbon is good to resist the compression/buckling load like you get on one side of the board when you try to bend it. When you land flat there is a compression/buckling force on the bottom of the board. Actually there is a double load, one from the bending of the whole board, the second from the sandwich wanting to flex inward from the waterpressure. Water can only create a force on a board (surface) perpendicular to the plane. Which is why this is the most seen type of breakage. Compression/buckling definately has something to do with bending. Take any rod like a batten or something and push from both ends. You will find that if the batten remains fully straight it can handle quite a high load. As soon as it starts to bend to one side, it will be easy to break it, because the whole compression load moves to one side: buckling. This initial bending force is very little so if the rod would not start bending in the first place, buckling would not occur. But since on the bottom of the board you get a compression load from the bending of the whole board AND you get a second force of the water wanting to bend the bottom (think of the batten example) inward, buckling is much more likely to occur. So it is of the highest importance to keep the bottom stiff. Since carbon does not bend easily like you say, it is good to handle buckling loads. At the same time you limit the flex of the individual sandwich, again preventing fatigue of the EPS. Limiting the flex of the individual sandwich does not mean limiting the flex of the whole board. Dyneema boards definately flex a whole lot more than full carbon boards. There are other more important/efficient ways to how we build up the inside to stop buckling of the outside but I want to keep that to myself.

^^^ Structural Mechanics 101. All that's missing are the diagrams.