i see boards breaking where materials change. ie. the edge of carbon patches. the edge of rail tape. so i am not convinced the issue is the same if building a full carbon board which includes glass or a full glass board. bourke even with his comments of different materials not working still makes boards with carbon in them.

there is also the idea that full carbon boards delam earlier because the foam compresses and the carbon springs back to original shape when impacted

everyone has their own take on it and i think it all comes down to strength to weight and feel. not sure exactly what i think is the best outcome because i'm still experimenting.

one thing i have been told by many experienced people is boards that are too stiff break when jumped and one thing i know myself is boards that are too stiff are less fun to ride.

Carbon is the best material to take compression loads. That is why masts are of carbon, when you downhaul, the fibres are compressed.
Main compression loads are in the top layer under the heels and in the bottom from flat llandings. In the bottom this force is only length wise so carbon UD is better here. Where ever you use carbon, you have to make sure there is enough of it to take the whole load. Then you build it up gradually outside of the main stress areas. Let it end in points as much as possible to avoid a sudden change in stiffness. That will cause weak points and we?ve seen this in practice as well. Also the most force is at the outer most layers, the middle of the deck (unless you have a concave deck) and at the highest points of the bottom shape (along the outline for a concave bottom shape, outline and centre for a double concave) If those layers don?t break, everything else in between will be fine. Like with the stringer of a surfboard, So I do not see the point in putting carbon around the rails. Where ever a board is likely to get hits like rails and nose, it is better to keep carbon away.

the guys who invented carbon on the rail say it is about improving the boards performance during turning by controlling flex. moving the stringer out so the rails are stiffer and flex faster out of turns.

if we take that further and build a stringerless board with no sandwich construction how do we prevent the board from snapping in 2.

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Bouke-Witchcraft said..
Carbon is the best material to take compression loads. That is why masts are of carbon, when you downhaul, the fibres are compressed.

I thought most fibres only work in tensile and little in shear except Kevlar . I also thought in a mast application the resin takes the compression load on the inside of the bend and the carbon fibres only take the tensile loads on the outside .

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Imax1 said..

Bouke-Witchcraft said..
Carbon is the best material to take compression loads. That is why masts are of carbon, when you downhaul, the fibres are compressed.

I thought most fibres only work in tensile and little in shear except Kevlar . I also thought in a mast application the resin takes the compression load on the inside of the bend and the carbon fibres only take the tensile loads on the outside .

yup. i agree.

@ Bouke, since a few years there is Graphene, how do you look at Graphene. Is this something we will see back in windsurf boards?

here is an interesting study into tensile and compressive strengths of carbon and glass layers and includes carbon/glass intra layers.
res.mdpi.com/d_attachment/materials/materials-11-01105/article_deploy/materials-11-01105.pdf

conclusions were that increasing carbon fiber increased tensile strength but had little effect on compressive strength. also of interest is that carbon sandwiched between glass g/c/g performed better than c/g/g or g/g/c

i guess i'll change the way i use carbon. one thing i do because i've seen it done this way is to bond the structural carbon pieces to the blank. looks like it's better to start with a layer of glass.

i guess food for thought if using other types of tensile fabrics.

another "eco" cloth under development from hayden shapes. i think colan may be involved so fingers crossed sanded get some in the future.

Hmmm dunno about that one. They said it was tops and would be avail for sale..... over a year ago. Maybe not all it was touted to be?

Hate to say it but not sure about this.
The motor industry has been doing it for years.
I think you will end up using more cloth therefore more epoxy.
Also how many boards do you have to make to get enough cloth for 1 board.
Just dont use carbon in the first place.
I think you could make more difference running your business more efficiently. Cutting transport to a minimum etc.
I love it when people make a vid of making "eco" boards and they are just pouring epoxy on and its running of the sides and they aren't even wearing a mask.
This is for one of the top "Eco" epoxies. This is for the hardener which is the bad stuff.

Ok now I am going to let them have it.
Whats with the watch I keep thinking. Its a bloody commercial for watches as well. Read the fine print at the end. They guy flies in in a bloody seaplane!
Eco cloth my arse!

i hadnt picked up on the watch ad.

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Gestalt said..
the guys who invented carbon on the rail say it is about improving the boards performance during turning by controlling flex. moving the stringer out so the rails are stiffer and flex faster out of turns.

if we take that further and build a stringerless board with no sandwich construction how do we prevent the board from snapping in 2.

Just think why steel H beams have that shape.

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GinoZanti said..
@ Bouke, since a few years there is Graphene, how do you look at Graphene. Is this something we will see back in windsurf boards?

There is a retired army Colonel living close to me..... without legs.......He is doing research on blast protection for the spanish army. Normally Dyneema for ballistic purposes is used as a non constructive material without resin but he wanted to experiment with Dyneema for helmets and he has been testing my Dyneema for use in helmets etc. He was also testing Graphene and Nano carbon in resin and he mixed me some of my resin. Nano carbon is a dangerous material by itself as it is so fine it will penetrate human cells so you need a special set up to mix it into resin and it is hard to mix it into resin.
It was stronger but one very big problem we then ran into was that we could not get the peel ply off any more. We had to sand it off which is a very time consuming job and difficult to stop in time. I have not found a solution for this yet but to not use peel ply, making the board heavier and a less clean laminate. So so far have I not used it again.

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Bouke-Witchcraft said..

Gestalt said..
the guys who invented carbon on the rail say it is about improving the boards performance during turning by controlling flex. moving the stringer out so the rails are stiffer and flex faster out of turns.

if we take that further and build a stringerless board with no sandwich construction how do we prevent the board from snapping in 2.

Just think why steel H beams have that shape.

yup i get that.

i was asking you how would we go about strengthening a stringerless board if we didn't want to put carbon on the rail. you mentioned above you thought carbon on the rails was the worst place for it. wondering what other solutions you'd consider.

One has to carefully define 'compression' in the context of board design.

Carbon fibers are very resistant to elongation, but not so much the opposite (compression?)

Carbon patch's under the feet on boards probably make the deck under your feet 'stiffer' because they resist elongation, and therefore do not deflect down into the board to compress the foam core as easily. In a sandwich scenario, it would seem logical to put the material with the most elongation resistance (carbon) under the sandwich, and the material with the most compression tolerance (E glass?) on the top of the sandwich.

A materials analysis who specialises in carbon masts explained to me that the masts typically fail on the compression side of the bend, not on the elongation side. The 'flexilbility' of the carbon matrix mast is mostly achived in the resin which allows some shear movment. At least, thats how I understood it.

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Gestalt said..
yup i get that.

i was asking you how would we go about strengthening a stringerless board if we didn't want to put carbon on the rail. you mentioned above you though carbon on the rails was the worst place for it. wondering what other solutions you'd consider.

When you say 'strengthening', do you mean 'stiffening' in longitudinal flex, or do you refer to making it more resistant to snapping in half?

As you have said, overly stiff boards can be not much fun to ride, so I presume you are aiming for the latter.

To make a board more resistant to snapping in half from overloading bending impact, I would assume that your materials should have more elongation tolerance, which carbon done not have.

yep more resistant to snapping in half.

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Gestalt said..



yup i get that.

i was asking you how would we go about strengthening a stringerless board if we didn't want to put carbon on the rail. you mentioned above you thought carbon on the rails was the worst place for it. wondering what other solutions you'd consider.

In the bottom and deck. Like an H-beam has. Basically you will need it just in the snapping zone so the tail and nose can still flex. And you just need it longitudinal so with carbon UD.

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sailquik said..
One has to carefully define 'compression' in the context of board design.

Carbon fibers are very resistant to elongation, but not so much the opposite (compression?)

Carbon patch's under the feet on boards probably make the deck under your feet 'stiffer' because they resist elongation, and therefore do not deflect down into the board to compress the foam core as easily. In a sandwich scenario, it would seem logical to put the material with the most elongation resistance (carbon) under the sandwich, and the material with the most compression tolerance (E glass?) on the top of the sandwich.

A materials analysis who specialises in carbon masts explained to me that the masts typically fail on the compression side of the bend, not on the elongation side. The 'flexilbility' of the carbon matrix mast is mostly achived in the resin which allows some shear movment. At least, thats how I understood it.

Well first of all, you have 2 types of compression: perpendicular and along the plane. A perpendicular force usually leads to a a force along the plane as well. Then compression can lead to 2 types of material failure. Plain collapse of the material, which hardly happens with solid materials but can happen much easier with foams for example. Or creasing. Take a batten and compress it from either end. As long as the battens stays straight, it can take a lot of force. Once it starts bending, it is easy to snap it. The longer or the more flexible the batten between the load points, the easier it is to crease. Often you get a combination of forces both along the plane and perpendicular like in the bottom or under the heels. Most boards snap on creasing though this is often not recognised as after the crease, fibres have broken so it will snap completely. By making the bottom stiffer against flex perpendicular to the plane helps to prevent creasing significantly. There are various ways to do this but I do not want to give away too much. Also if a bottom starts to become more flexible or becomes more concave is a sign of fatigue and probably will not last a lot longer.
This board had the bottom flexing inward but the crease was no so bad the whole board broke:

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Bouke-Witchcraft said..

Gestalt said..



yup i get that.

i was asking you how would we go about strengthening a stringerless board if we didn't want to put carbon on the rail. you mentioned above you thought carbon on the rails was the worst place for it. wondering what other solutions you'd consider.

In the bottom and deck. Like an H-beam has. Basically you will need it just in the snapping zone so the tail and nose can still flex. And you just need it longitudinal so with carbon UD.

a H beam has a web. get rid of the web and you don't have a h beam. the web connecting the flanges gives the beam it's shear strength.

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Gestalt said.

a H beam has a web. get rid of the web and you don't have a h beam. the web connecting the flanges gives the beam it's shear strength.

You are getting quite close to something big. Follow that thought to its natural conclusion and you will have found great wisdom.

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Overner said..

Gestalt said.

a H beam has a web. get rid of the web and you don't have a h beam. the web connecting the flanges gives the beam it's shear strength.

You are getting quite close to something big. Follow that thought to its natural conclusion and you will have found great wisdom.

Is it that h beams dont react well to twisting and therefore a h beam is not the optimal structiral shape for a windsurfer

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Gestalt said..

Overner said..

Gestalt said.

a H beam has a web. get rid of the web and you don't have a h beam. the web connecting the flanges gives the beam it's shear strength.

You are getting quite close to something big. Follow that thought to its natural conclusion and you will have found great wisdom.

Is it that h beams dont react well to twisting and therefore a h beam is not the optimal structiral shape for a windsurfer

But has a board the shape of an H beam and does it need to be? I just mentioned an H-beam as an example to indicate where the forces go. An H-beam is a pretty simple cheap to make part for construction as it can be extruded continuously. And there is a web connecting the flanges or not? The web does not have to be in the middle either and there can also be more than one web. And the shear forces aren?t that high. You can easily cut holes in the web:
And there are other constructions with the same goal, a sandwich construction for example but they also make light and stiff constructions from tubes welded together in various angles.

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leto said..
Would be nice if there was some material similar to say 15-20 density EPS which either could be heated to say 70C to become liquid or was made of some food starch. Imagine you CNC it, build a board then flip the board and heat it up and the entire core is drained leaving a hollow board. Plus the drained liquid can be re-foamed. Or in case of some starch-like material you open the pressure valve, put the board in an anthill and a week later, you get a hollow board.
I think that if the EPS core can be easily removed, it will make all boards about 1.5-2kg lighter and eliminate the problem of water in the core.

There is seemingly only one hollow construction on the market right now, Patrik with its carbon prepreg/honeycomb airnside patrik-windsurf.com/airinside/ Patrik says that weight savings are 15/20% with respect to a normal construction, hard to tell how much that is due to the prepreg/honeycomb. The airinside Slalom 95 is quoted at 5.12 Kg, vs the weight of the regular around 6 Kg. Significant, but you need to consider much bigger boards to see a 1.5-2Kg saving.

Having said that I am really tempted to get it, I need a new medium wind slalom!

Bourke, I don't think that's what he referred to as 'web' he meant the fillet in the right angle between the two surfaces.

I'm no engineer but they do refer to as sandwich construction working well as it is essentially an I-beam (or H beams as some here are calling it), so I believe the engineers.

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Mark _australia said..
Bourke, I don't think that's what he referred to as 'web' he meant the fillet in the right angle between the two surfaces.

Yes, the 2 surfaces take by far the most force. But they need to be connected and it doesn?t matter that much how they are connected as long as they are connected. The web is just one way to do this. The rails is another example. Which surfboards happen to have. Also the connection at the nose and tail do their part.

Of course it matters 'how they are connected'. I beam and H beam have differing amounts of web and thus have differing strengths.

Anyway what I referred to is how you mentioned holes in the web (in that pic) and that's not the web so I made a point of clarification.

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duzzi said..

leto said..
Would be nice if there was some material similar to say 15-20 density EPS which either could be heated to say 70C to become liquid or was made of some food starch. Imagine you CNC it, build a board then flip the board and heat it up and the entire core is drained leaving a hollow board. Plus the drained liquid can be re-foamed. Or in case of some starch-like material you open the pressure valve, put the board in an anthill and a week later, you get a hollow board.
I think that if the EPS core can be easily removed, it will make all boards about 1.5-2kg lighter and eliminate the problem of water in the core.

There is seemingly only one hollow construction on the market right now, Patrik with its carbon prepreg/honeycomb airnside patrik-windsurf.com/airinside/ Patrik says that weight savings are 15/20% with respect to a normal construction, hard to tell how much that is due to the prepreg/honeycomb. The airinside Slalom 95 is quoted at 5.12 Kg, vs the weight of the regular around 6 Kg. Significant, but you need to consider much bigger boards to see a 1.5-2Kg saving.

Having said that I am really tempted to get it, I need a new medium wind slalom!

We made a hollow board some 15 years ago. It was a project for a student engineer as his final thesis. He calculated it with a 12mm outer skin from 8mm honeycomb in combination with 4mm PVC with mainly E-glass and 3 stringers. In the end he said that according to his calculations it would not be possible to make it lighter and/or stronger. It was a 90L board and it ended up weighing 6.5kg. It snapped on the 3rd session.

But I can imagine that for higher volume slalom or racing boards and using carbon prepreg and just honeycomb it is a different story.

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Bouke-Witchcraft said..

duzzi said..

leto said..
Would be nice if there was some material similar to say 15-20 density EPS which either could be heated to say 70C to become liquid or was made of some food starch. Imagine you CNC it, build a board then flip the board and heat it up and the entire core is drained leaving a hollow board. Plus the drained liquid can be re-foamed. Or in case of some starch-like material you open the pressure valve, put the board in an anthill and a week later, you get a hollow board.
I think that if the EPS core can be easily removed, it will make all boards about 1.5-2kg lighter and eliminate the problem of water in the core.

There is seemingly only one hollow construction on the market right now, Patrik with its carbon prepreg/honeycomb airnside patrik-windsurf.com/airinside/ Patrik says that weight savings are 15/20% with respect to a normal construction, hard to tell how much that is due to the prepreg/honeycomb. The airinside Slalom 95 is quoted at 5.12 Kg, vs the weight of the regular around 6 Kg. Significant, but you need to consider much bigger boards to see a 1.5-2Kg saving.

Having said that I am really tempted to get it, I need a new medium wind slalom!

We made a hollow board some 15 years ago. It was a project for a student engineer as his final thesis. He calculated it with a 12mm outer skin from 8mm honeycomb in combination with 4mm PVC with mainly E-glass and 3 stringers. In the end he said that according to his calculations it would not be possible to make it lighter and/or stronger. It was a 90L board and it ended up weighing 6.5kg. It snapped on the 3rd session.

But I can imagine that for higher volume slalom or racing boards and using carbon prepreg and just honeycomb it is a different story.

Yes, exactly, a very different story than a student's attempt that brakes the third time out Hollow construction can of course be done without prepreg and honeycomb. And it can work in extreme conditions: Doyle built hollow B&J and wave boards (Aircore) in the Gorge the 90s.

Weight saving for an high tech solution is significant the only limiting factor is cost and technology ... nobody would ever think to build a sailboat that was not hollow!

(Actually, I take it back. There have been some examples of mini-transat boats with eps core.)