Interesting video,
I wonder what this means to carbon reinforced boards , is it just wank ?
Full carbon i understand.
Nice video. Note the author indicates 'don't mix & match unless you know what you are doing' and is mainly referring to break points/loads of hybrid laminates [SIC]. At an industry level, 21st century board construction has been fine tuned for many decades by pros+composite engineers who mostly know what they are doing. This includes the hard earned knowledge of required bend patterns/reflex characteristics and abrasive/impact resistance not covered in the vid, all essential for getting punters across lumpy water quickly, controlling turns and generally allowing enjoyment of the product until boredom or breakage kicks in. Today's production boards are pretty good with the right laminate being on the right boards and in the right places, certainly more carbon will creep in over time much like we've seen with the rigs we use.
My bet is structural cores will be the next area to bring weight down without reducing longevity. But as with anything new, it will be pricey and primarily for wealthier early adopters in the first instance.
Does it mean that if carbon is added under footpads or for stiffening and impact like some of the new Starboards do along the rails , could the carbon be damaged ( and therefore not working ) without knowing it , even though it looks fine ?
Im in two minds.
According to the vid wouldn't an extra layer of glass be better under the pads and mabee kevlar along the rails for impact strength ?
I understand that carbon has its place,
I also understand that carbon is trendy and looks cool in brochures.
mmmmm
I don't like it. 
Well not in the context of WS board. The video is correct of course but he only addresses strength. He does not address abrasion resistance, or wanting to conform to a weight limit.
(1) at 2:30 he is talking about stretching. Things are stronger in compression than tension so the value (or lack thereof) of carbon on the deck of our boards is different to on the bottom of our boards. The deck is in compression and the bottom in tension for the most part. (neglecting the sandwich layer that also has its own tension and compression areas but I'm trying to keep it simple....) But then under the heels we are back to tension again as we try to dent it downwards. So it is not as simple as just looking at elongation as he says. Essentially: He is talking about just plywood. We have plywood - foam - plywood all glued together. Its different. In some ways...
(2) 5:20 ish he is talking about a layer of carbon over 3 layers of glass. Yes of course it is correct, but it neglects items where one is trying to achieve a weight limit. ie: yes, bunging a layer of carbon over a glass laminate adds no strength (as many assume it does). BUT if you are trying to make a board that is under 7kg then the use of carbon makes sense as strength to weight ratio is high.
That is my main issue here - to a casual observer this video makes it sound like carbon is useless. No, he is just saying adding it for no reason is useless. They still choose carbon to build aircraft wings and windsurf boards for a reason.
(3) 5:59 ish - he talks about reversing the layers being better..... 3 of carbon and a layer of glass over the top. Well, that is what we do in windsurfing boards. Everybody can switch off now
(4) at about 6:32 he says why not use carbon for all of the laminate and forget glass. Again, he is only addressing strength. Glass (and even better, aramid or innegra) offer amazing abrasion resistance. Anyone who has sanded carbon fibre will see how fast it disappears. Its shocking.....
So some outer glass can be a major help.
Then, he makes reference somewhere to how carbon fails completely and glass will break but stay together a bit to limp home - VERY valid to us.
So, no, your carbon and glass board is not crap. He is talking about carbon added for wank factor only.
Select to expand quoteImax1 said..
Does it mean that if carbon is added under footpads or for stiffening and impact like some of the new Starboards do along the rails , could the carbon be damaged ( and therefore not working ) without knowing it , even though it looks fine ?
Im in two minds.
According to the vid wouldn't an extra layer of glass be better under the pads and mabee kevlar along the rails for impact strength ?
I understand that carbon has its place,
I also understand that carbon is trendy and looks cool in brochures.
mmmmm
What the guy says is true, but he's talking about where all the fibers are parallel. When I add carbon in my boards between tail and mast track, I put it at 45deg to the glass, so it really gives the board stiffness against twisting, stiffens up the sandwich to take the load off the core foam, and it goes underneath the sandwich to protect it from sharp impacts. I forget now the exact reduction in stiffness by laying up the carbon cloth at 45, but it's much closer to the glass, may even be less than. I also have smallish carbon patches on the deck under the footpads. 1 layer of 6oz, so far, has been enough to take my weight from some fairly high flatish landings. The Carbon under the pads is there for pressure at right angles, from the feet, to spread the load on the core foam as much as possible, not from the stretching force of something trying to snap the board.
Kevlar is a real pain!!!! extremely hard to cut, an what ever you do sand into it. I use a small patch of carbon/kevlar as nose reinforcing, but I make sure it's under a few layers of sacrificial glass.
Back when I was building whitewater racing Kayaks, we quickly learnt that mixing Carbon into fibreglass was a waste of money.
However, mixing fibreglass with Aramids (Kevlar) was a great benefit as long as you used the much stronger bonding Epoxy or Vinyl-ester Resins. Using them with Poly-ester resins was also a waste of time and money.
IMHO, there is definitely a very large marketing-wizz/wank factor in the advertised use of Carbon Fibre in windsurfing boards, where high strength glass, Aramid fibres or wood would achieve better results. (Aramids are very light, like Carbon, but have far superior tensile strength).
Massive stiffness is something I actually don't want in my windsurfing boards!
One huge reason Aramids have not gained favour in the surfboard and windsurfing custom build industry is for that which Decrepit mentioned. It is impossible to sand! Therefore, it can't be used on any external surface that is subject to sanding in the construction process. For internal layers between core and sandwich foam it is very useful, and can be used under a layer of sand-able glass with care.
Carbon fibre may make sense under foot pads if done correctly. And it has a huge place in fins and masts! 
Marks on the money in relation to compression loads. Carbon slightly outdoes glass in this area as it is about 5 times stiffer than glass. This also means that failure of carbon is catastrophic. (still maybe need a bit of glass)
Carbon under the heels takes the weight of landing etc. due to its layup with the pvc core and inner cloth. when weight is applied the core bends downwards the layers under the core are under tension and the outer layers are under compression. the correct layup of carbon and glass, etc. on the outside helps prevent buckling of the fibres that lead to delamination and laminate breakdown.
Compression is not a force that is at right angles to the cloth. It is a force that is internally applied to the fibres on the outside of a composite that has a force applied externally. Below image shows those forces. If the compression layup cannot handle the forces it will buckle or wrinkle and fail leading to delamination and cracking of the core.
Compression has nothing to do with sharp impact or knocks and bumps, this is impact forces that carbon does not like.
Board makers are putting carbon around the rails to help stiffen the boards while keeping weight down, not for impact resistance.
Carbon has become more popular in board construction due to it have approximately twice the strength to weight ratio than glass, assisting to keep boards light and hopefully kind of strong.....well maybe.......ok, sometimes, but not if it says Textreme on the label.
This video has no relevance to sailboards as you do not make a board by just laying up layers of glass and carbon. Proper core composite layups have a lot more going on than what this video is about.
P.S. I'm not a carbon fan, you can make a decent board without the use of it.
Select to expand quotebuzzy said..
Marks on the money in relation to compression loads. Carbon slightly outdoes glass in this area as it is about 5 times stiffer than glass. This also means that failure of carbon is catastrophic. (still maybe need a bit of glass)
Carbon under the heels takes the weight of landing etc. due to its layup with the pvc core and inner cloth. when weight is applied the core bends downwards the layers under the core are under tension and the outer layers are under compression. the correct layup of carbon and glass, etc. on the outside helps prevent buckling of the fibres that lead to delamination and laminate breakdown.
Compression is not a force that is at right angles to the cloth. It is a force that is internally applied to the fibres on the outside of a composite that has a force applied externally. Below image shows those forces. If the compression layup cannot handle the forces it will buckle or wrinkle and fail leading to delamination and cracking of the core.
Compression has nothing to do with sharp impact or knocks and bumps, this is impact forces that carbon does not like.
Board makers are putting carbon around the rails to help stiffen the boards while keeping weight down, not for impact resistance.
Carbon has become more popular in board construction due to it have approximately twice the strength to weight ratio than glass, assisting to keep boards light and hopefully kind of strong.....well maybe.......ok, sometimes, but not if it says Textreme on the label.
This video has no relevance to sailboards as you do not make a board by just laying up layers of glass and carbon. Proper core composite layups have a lot more going on than what this video is about.
P.S. I'm not a carbon fan, you can make a decent board without the use of it.
Yep. 
I recon the best sandwich will have extra glass on top to resist crush and deform', and kevlar under for tension strength. And maybe a double layer sandwich of lots of deck grip, closed cell foam of you jump to the clouds! 
Interesting video, and responses are even more informative and interesting...
My FS board has glass, carbon kevlar, wood, then finally carbon laminate for its deck (from top to bottom), and the deck is pretty tough, the rest is pretty fragile.
How does this all apply to masts? I understood <100% carbon mast has a similar amount of carbon as a 100% mast, but use the extra glass to improve the durability, and maybe allowing the amount of carbon to reduced slightly as the structural margins can be reduced slightly. Is this correct?
The world is full of contrarians, he makes some points, but only some, which is why we should all carry our BS detectors, mine was pinging.
That video is extremely straight forward. If your brain hurts when trying to understand it, you should leave composite construction alone.
Excellent presentation from a person who actually knows what they are talking about, and yes, those principles are directly applicable to windsurfer construction, in the right contexts.
Sailquick saidSelect to expand quote
Massive stiffness is something I actually don't want in my windsurfing boards!
Andrew, I have to disagree with you a bit here. Using the core polystyrene foam as a shock absorber doesn't make good engineering sense, it's not really suitable for that job.
If the sandwich flexes, the core foam will fatigue and compress a bit, leaving you with negative rocker under the feet. Exactly where you don't want it. The boards lift moves aft behind the rider, forcing the nose down, and increasing wetted area. The next stage of course is collapse of the foam and delam.
Guess it depends how long you want the board to last?
And as I said earlier, if the carbon cloth is laid on the bias it doesn't add to the longitudinal board stiffness any more than the fiberglass.
If the ride is too harsh you can always experiment with different foot pads.
Select to expand quoteracerX said..
Interesting video, and responses are even more informative and interesting...
My FS board has glass, carbon kevlar, wood, then finally carbon laminate for its deck (from top to bottom), and the deck is pretty tough, the rest is pretty fragile.
How does this all apply to masts? I understood <100% carbon mast has a similar amount of carbon as a 100% mast, but use the extra glass to improve the durability, and maybe allowing the amount of carbon to reduced slightly as the structural margins can be reduced slightly. Is this correct?
My ancient 70% killwell matrix 5s, have all the carbon running along the mast for tensile strength and the 30% glass around the mast for compressive strength, and to hold the carbon in place.
What I don't understand is how the old 30% carbon masts worked? I don't understand that at all.
Select to expand quotesailquik said..
That video is extremely straight forward. If your brain hurts when trying to understand it, you should leave composite construction alone.
Excellent presentation from a person who actually knows what they are talking about, and yes, those principles are directly applicable to windsurfer construction, in the right contexts.
Have to agree with you here Andrew, I learnt a few things from it, didn't realise how good s glass is and how bad kevlar is in compression.
Select to expand quotedecrepit said..
Sailquick said
Massive stiffness is something I actually don't want in my windsurfing boards!
Andrew, I have to disagree with you a bit here. Using the core polystyrene foam as a shock absorber doesn't make good engineering sense, it's not really suitable for that job.
If the sandwich flexes, the core foam will fatigue and compress a bit, leaving you with negative rocker under the feet. Exactly where you don't want it. The boards lift moves aft behind the rider, forcing the nose down, and increasing wetted area. The next stage of course is collapse of the foam and delam.
Guess it depends how long you want the board to last?
And as I said earlier, if the carbon cloth is laid on the bias it doesn't add to the longitudinal board stiffness any more than the fiberglass.
If the ride is too harsh you can always experiment with different foot pads.
I agree with your disagreement, also the more the board flexes, the more speed is being scrubbed off, stiff = fast.
One of the reasons you don't see the plastic boards of the 80's anymore, they were slow, too much flexing, but they lasted a long time. Shock absorption should be done with the foot pads alone, one of several reasons they have improved over the years with laminated pads.
Select to expand quoteMastbender said..decrepit said..
Sailquick said
Massive stiffness is something I actually don't want in my windsurfing boards!
Andrew, I have to disagree with you a bit here. Using the core polystyrene foam as a shock absorber doesn't make good engineering sense, it's not really suitable for that job.
If the sandwich flexes, the core foam will fatigue and compress a bit, leaving you with negative rocker under the feet. Exactly where you don't want it. The boards lift moves aft behind the rider, forcing the nose down, and increasing wetted area. The next stage of course is collapse of the foam and delam.
Guess it depends how long you want the board to last?
And as I said earlier, if the carbon cloth is laid on the bias it doesn't add to the longitudinal board stiffness any more than the fiberglass.
If the ride is too harsh you can always experiment with different foot pads.
I agree with your disagreement, also the more the board flexes, the more speed is being scrubbed off, stiff = fast.
One of the reasons you don't see the plastic boards of the 80's anymore, they were slow, too much flexing, but they lasted a long time. Shock absorption should be done with the foot pads alone, one of several reasons they have improved over the years with laminated pads.
I'm not talking about the floppy soft plastic boards at all. I am referring to the difference between a well made non carbon sandwich and the same type with heaps of carbon. Big difference!
I am well aware of the difference even the slightest negative rocker can make in an out of shape board. You definitely don't want that to happen, but good sandwich construction with wood and/or S Glass should prevent it. I like your strategy of laying the Carbon fibre on bias if that has the effect you describe.
I have a ten year old Isonic wood that has had an absolute pounding all it's life. It is still 100% sound and the rocker is still as new. It is still my go to, all round board in it's size. The harshness of the full Carbon boards is body breaking and out of control in comparison.
Comfort, control and confidence = fast.
Decrepit, reference your Killwell C70 Matrix 5
Is it constant curve? Are they any good? For an ol one piece that is still in use. I rig aerotech n gasstra nitro fine on this ol mast.
Select to expand quoteImax1 said..
Interesting video,
I agree. He never mentions windsurfing, so it's clearly not a critique of how current windsurf boards are built. It is, however, helpful for someone who makes occasional board repairs. Fixing a nose with some glass layers for better impact resistance, and a carbon layer on top to match the looks, seems reasonable at first. Not that I ever did that, but I'd now definitely shy away from that, since it only adds weight, not strength.
I also found the numbers about tensile strength interesting. I think they explain the well-known difference in impact resistance: glass can stretch more, absorbing and distributing the load.
So for a nose repair of a carbon board, I'd be tempted to use only glass instead of carbon. Stiffness should not be much of an issue in the first few centimeters of the nose, impact resistance often is. Is there a problem with this approach?
Yes sanding Kevlar is crap but cutting it is easy. Just run tape where you want to cut and cut through the tape and cloth. I tend to use cheap scissors which last a good 6 mths
He didn't mention Basalt, which sits in between S-glass and Carbon. Stronger than S-Glass but has similar properties than S-Glass , not brittle like carbon, so if you want the matrix to be similar to S-Glass but stronger use Basalt.
Select to expand quoteolskool said..
Decrepit, reference your Killwell C70 Matrix 5
Is it constant curve? Are they any good? For an ol one piece that is still in use. I rig aerotech n gasstra nitro fine on this ol mast.
Yes constant curve, In my opinion one of the best masts ever made.
But bear in mind I haven't tried many, mine are over 20years old!
They have been pole volted into the reef, leaving the board dangling in the air.
I've lost track of the booms and harnesses that have been completely trashed in various stacks over the years, but the masts just keep going on.
Bugs, "Phil Smith" designed them when he was Hot Sails New Zealand.
When the sailing comunity first switched to carbon from fibreglass, a lot of masts were snapping mid race, because they had to reduce wall thickness so the masts wouldn't be too stiff. So Bugs had the idea of going back to the old original 46mm mast diameter and increasing wall thickness. Trouble was at the time it was only ancient mast extenders, and chinook extenders with the top and bottom shims removed, that would fit the masts. So they never really caught on.
But you have a treasure there, don't throw it a way.
Select to expand quoteboardsurfr said..
>>> Stiffness should not be much of an issue in the first few centimeters of the nose, impact resistance often is. Is there a problem with this approach?
In my opinion stiffness is only an issue aft of the mast, I only use carbon in that area, mainly under the sandwich so it's protected from impact.
I certainly would never do a nose repair with plain carbon. I do use carbon/kevlar under glass, and that seems to lessen nose damage significantly
Select to expand quotekato said..
Yes sanding Kevlar is crap but cutting it is easy. Just run tape where you want to cut and cut through the tape and cloth. I tend to use cheap scissors which last a good 6 mths
Good one Craig I'll try that next time.
Select to expand quotedecrepit said..kato said..
Yes sanding Kevlar is crap but cutting it is easy. Just run tape where you want to cut and cut through the tape and cloth. I tend to use cheap scissors which last a good 6 mths
Good one Craig I'll try that next time.
Ot
kevlar tricks...
A trick we use in RC modelling is to blunten scissors by running them past a belt sander at 90 degrees. Cuts Kevlar really easy - pretty well stuffs the scissors for anything else
ive also seen multiple layers of Kevlar cut with industrial cutting fabric cutting wheel - imagine a oversize Olafa disk in an angle grinder. Cut through Kevlar into a waste sheet of polystyrene
info go in this thread...
www.rcgroups.com/forums/showthread.php?795224-Sharpening-Kevlar-Scissors
Sanding kevlar...
we sand exposed Kevlar with fine wet and dry used wet ie 400-600 gets a very smooth finish
we also firm up frayed Kevlar that has been trimmed in a laminate with superglue before sanding
cheers Jeff
Select to expand quoteboardsurfr said..Imax1 said..
Interesting video,
I agree. He never mentions windsurfing, so it's clearly not a critique of how current windsurf boards are built. It is, however, helpful for someone who makes occasional board repairs. Fixing a nose with some glass layers for better impact resistance, and a carbon layer on top to match the looks, seems reasonable at first. Not that I ever did that, but I'd now definitely shy away from that, since it only adds weight, not strength.
I also found the numbers about tensile strength interesting. I think they explain the well-known difference in impact resistance: glass can stretch more, absorbing and distributing the load.
So for a nose repair of a carbon board, I'd be tempted to use only glass instead of carbon. Stiffness should not be much of an issue in the first few centimeters of the nose, impact resistance often is. Is there a problem with this approach?
The issue we had with it was that it is factual, but Imax posted wondering if it means carbon boards are worthless.
From what I can see, we answered that, not critiqued the video itself.
The posting of his second video was helpful.
There is a problem with your approach, albeit technical only, if one uses too much glass. Making the nose way stronger will just cause the whole thing to snap off at the area where old meets new, when hit next time.
Select to expand quotejirvin4505 said..
A trick we use in RC modelling is to blunten scissors by running them past a belt sander at 90 degrees.
I buy the serrated on one side dressmakers scissors at Spotlight that are "guaranteed to never blunt" and lifetime guarantee.
Years ago when I was cutting heaps of Kevlar for building whitewater racing kayaks. you could get very expensive 'kevlar shears' from the fabric suppliers. They were no better than vastly cheaper 'stay sharp' scissors that came with a sharpening sheath in any supermarket. Cut a few inches - sharpen - Cut - sharpen.. etc.
I like the tip about using tape. I had never come across that before in any literature, or from any of my network of fellow kevlar workers. I will try it if I ever have the need to cut Kevlar again. 
There's an assumption in his video which no one appears to have questioned. He says the carbon adds no strength after it breaks. But who says the carbon is going to break? The carbon does add stiffness to the total construction, and if the design does not subject the carbon to forces that will break it, then it will continue to do so.
The takeaway point is that the carbon will fail first under excessive loading, so the additional carbon layer is giving you extra stiffness, but not additional strength or toughness. Be aware of it.
Maybe the phrase 'Carbon Reinforced' is misleading...perhaps 'Carbon Stiffened' would be more appropriate, not leading you to thing the carbon is making it stronger.
Select to expand quoteHarrow said..
Maybe the phrase 'Carbon Reinforced' is misleading...perhaps 'Carbon Stiffened' would be more appropriate, not leading you to thing the carbon is making it stronger.
Good point. Maybe they also should color the carbon fibers blue to make this more obvious
