SchobiHH said..

GasHazard said..

SchobiHH said..
This is such a ridiculous discussion. Toe In is totally overrated with windsurf boards. I have a physics and math background and I have some insight about the physical principals.

1. You do not want to have 0 AOA, because then no fin generates lift
2. The flow sideways of water is just 1-2cm deep (called boundary layer) the rest of the fin still goes through still water. That is why Bouke sells his magic twist fin.
3. Because of these little angles little more or less simply doesn't create noticable drag. Thats a physical principle. Everybody knows this studing that subject. The drag only starts with higher AOA.
4. The reason why surfers have it is because they do certain different moves other than windsurfers can do where there is potential benefit but not with the radii we windsurfers turn.

But believe what you believe.

BTW you can start a discussion about sanding the bottom of the board. This also is one of this irrational myth in the windsurfing community.

I think you blew it on point no 1.
All your fins should have the same effective angle of attack all the time. Zero is the default because boards are symmetrical. When you're sailing you point your board at the required angles of attack for your fins.

That is the wish but not what I was trying to say, I simply wanted to say that you need an AOA for the fin to work. There will be no same effective AOA for all fins because the fins are going through different water depth and with it the AOA changes. Also leeward are windward fin are different. So you always have a compromise. The question is, is the effect dramatic or neglectable? I have this discussed with some aerodynamics professor who also is a windsurfer a while ago and he clearly agreed with my master knowledge on that subject that this is on the neglectable side. Anybody else stating the opposite should have real physical arguments.

With your "master knowledge" how many prototypes have you built? How many boards?.. How many fins? What is your level of wave sailing, could you test your prototypes properly even if you had made them. This is the REAL difference between You & Bouke or Ola H. ... you will figure this out one day when you get out of school & into the "real" world... Until then maybe use a bit more humility when discussing the actual application of science.

SchobiHH said..

The diagram below shows the correlations between drag / lift vs. AOA. If you can read it you know what I am talking about. But you have have a different opinion on it, because your whole sales story is based on it.I don't want to discuss this with you. That is already obvious from your picture of the airfoil app and your argument that you can see this in any picture of some CFD picture that any physical and mathematical argumentation is pointless. Just one point your fin is ridiculous 20x10cm in size. In single Fin terms a 24cm single fin. But using this information calculate backwards the drag of a typical thruster which is 1/3 in size and then having the effect of the boundary layer also only to 1/3 of the deepth. Then as a result you have 1N force of drag which is the equivalent of 100g in gravity. If this is not neglectable I don't know what is. Especially if nobody really knows what the right angle should be. Assume that you have a toe in so that the AOA is 0 at the base, then if you consider that 2/3rd of the fin flow not in the boundary layer then therefore with the wrong AOA which should be 2N of force so eventually it is bad to have a toe in which is 0 at the base, so what is then the right angle? But you have found the holy grail. You promote your twisted fins. Congratulations! And you can measure forces of 1N. Again congratulation. Because nobody needs them because nobody can feel 1N. But I forgot, you have these nice colourful CFD pictures. Your CFD arguments are in my opinion silly and show only one thing that you do not have the necessary respect for the complexity of the physics that is related to it. None of it is conclusive but merely shows nice colourful pictures. It might have been possible to discuss this with the original creators of that work. But that you assert to be able to judge the meaning of it without the academic background tells everything. Finally I have to answer to the silliest of sentences I have read wrt to argumentation. "Just look at what lengths they go in F1 to improve the aerodynamics to gain one second. For sure the driver cant feel one second but it can be measured. Just that we cant measure it like that, does not mean it isnt there." EXCACTLY, the F1 would never invest a cent in it if they couldn't measure it. Because then they don't know if it is even there. But you know that it is there.

How come all boards with paralel symmetrical fins ALL have small side fins? And trifins as a result need a big centre fin, pretty much eliminating the advantage of a multifin. How come people on quads or trifins are complaining it feels draggy even with small side fins? How come people get that straight lining effect when using bigger side fins or at higher speeds? I use science as a guidance but sure double check this constantly with practice and feedback of people. The amounts in Newton is irrelevant, it was just about showing the difference between having zero AoA and 2 degrees that gives about double the amount of drag. This is just a simple program and not as accurate as real life but it is an indication and that profile is very similar to hat I use. I dont remember the exact diagram of the profile I use and there are loads of different profiles with different diagrams. Plus, like Ola said as well, one other really important aspect is that if you have zero AoA without applying foot pressure, this is the best starting situation to enter any turn, you have a neutral starting point. That is all about FEEL. From a neutral point, it is easiest to enter a turn as the fins will allow the board to initiate the turn with just light pressure and from there the harder you push, the harder the fins push back, all fins the same amount in a natural way so nothing weird happens when one fin leaves the water. This is the problem the customer from Chile encountered when he went from single fin to quads. The fins were not behaving natural in a turn and he got the straight lining effect just when wanting to tighten the turn, causing him to fall between board and sail, just as described by Boardseeker. A proces we went through years earlier. This is something very good riders can get used to because they will learn when this happens and are prepared to react accordingly. Most pros, who will simply need to ride what he is given, will do that, their bosses may not want to hear something is wrong. But that is less the case with average skilled wave riders who are paying for their gear, which is the vast majority, including myself. And I get loads of feedback from such riders, like the customer from Chile or the guy with his pyramid but besides that on an every day basis, fx from rental customers, sometimes people whom have never even heard of Witchcraft so they try completely unbiased. So I tried to get the fins neutral BOTH for the feel, turning behaviour and drag and CFD was a good guidance to do this. The way our fins are now simply feel very natural and low drag, as a result we can use 3 equalish sized fins which have the advantage over 4 fins to offer less drag, similar turning and better predictability and adaptability. And opposite of the straight lining effect, when the outer fin leaves the water when wanting to tighten the turn, the board reduces drag even more and reacts by tightening the turn, just how it should be.

SchobiHH said.. Finally I have to answer to the silliest of sentences I have read wrt to argumentation. "Just look at what lengths they go in F1 to improve the aerodynamics to gain one second. For sure the driver cant feel one second but it can be measured. Just that we cant measure it like that, does not mean it isnt there." EXCACTLY, the F1 would never invest a cent in it if they couldn't measure it. Because then they don't know if it is even there. But you know that it is there.

Hmmmm, I wonder who is being silly here.....according to you better not try (invest) anything because you can?t measure it. First of all, they simply CAN measure much smaller improvements than we can. And secondly even if they would not be able to measure small differences, it should be clear to anyone with enough common sense that there ARE differences and once you get enough small improvements, at some point, the total amount of improvements becomes clearly visible by the eye or feel. So good thing not everyone listens to you eh? Sorry for being sarcastic but I did not start saying stuff like "ridiculous" or "silly".

And nowadays you can measure more things if youd want to using GPS and other sensors for highth, g-forces, spin rates. Back in the day I tried that with a shadow box but that thing wasnt reliable enough. Now you do have more reliable devices but by now weve got so much more practical experience that we know we are close even without such testing. And to do it correctly, you?d need to measure wind strength and angle simultaneously and even then there can be variables that can influence the results. Maybe I?ll do it one day but I am not too keen now. Being nerdy is OK when you are not on the water but once you are out there you just want to have fun, right?And no, I do not have an academic back ground, I learned to think for myself. I know enough academics to know that is not always the case with them..........

Bouke-Witchcraft said..

SchobiHH said..

CAD is fun. CNC is not. It is quite difficult to index the board properly on the machine.I have seen assymetrial and to thick or thin boards all coming from the CNC.

Yes that is true. Since you seem to know a bit about this, maybe you could invent a system to position the board accurately? Maybe you could develop a CAD program that calculates the positions of the vacuum suckers and then have a positioning tool at the back for the X and Y axis (to the 0.1mm) and then you only have to position the nose for the Y axis. That would be really cool, then it would be a piece of cake to index a board, all boards come out the same and it takes 10 mins to turn a board around. Oh, wait, we already have such a system..... Sarcasm off, shall we be respectful to eachother again now?

You start the fight. I just mentioned the the topic is overrated and physical reason shows that the effect is very likely neglectable. Also experience support my claim, because there are so many different toe in configurations out there and still good boards.

But you show me some simfoil data to explain to me that I am wrong. I have no problem if somebody has an opinion on it, you have a lot of experience and you have many people who like your boards. That is fine and you can be proud of your achievements. But this is not enough for you, you come to every forum tell everybody that you have found the holy grail. And that you have scientific result. But you have not found anything. Some other people have done some scientific work, but none of their results is available to question. And then you imply that you have scientific arguments. But you do not know anything about the science behind your pictures and tools nor can you measure anything nor can you scientifically argue. A reasonable discussion is senseless. BTW I checked the current simfoil. Something is wrong with your setup. The reynolds numbers are way higher in water The Cl/Cd numbers not match that of proper profiles. The stall simulation with which your data seem to be derived might be inappropriate according to some other sources for profile data, which I have checked it against, etc... I would be fun to discuss this with someone really able to grasp the physics behind it. But it just ennoying to talk about this, if the opposite side is not able to derive the scientific conclusions but merely shows the remaining results of the orignal creators. Your unwillingness to accept that you can not face a scientific discussion about the topic tells me all. Why not stick to what you know best building boards for happy customers, and not tell others that their science knowledge is wrong, i.e. don't step into a terrain, where your position is just silly.

^^ I'm interested in that as every CAD bottom has a kink and hand shaping makes a smoother curve.

SchobiHH said..

You start the fight. I just mentioned the the topic is overrated and physical reason shows that the effect is very likely neglectable. Also experience support my claim, because there are so many different toe in configurations out there and still good boards.

But you show me some simfoil data to explain to me that I am wrong. I have no problem if somebody has an opinion on it, you have a lot of experience and you have many people who like your boards. That is fine and you can be proud of your achievements. But this is not enough for you, you come to every forum tell everybody that you have found the holy grail. And that you have scientific result. But you have not found anything. Some other people have done some scientific work, but none of their results is available to question. And then you imply that you have scientific arguments. But you do not know anything about the science behind your pictures and tools nor can you measure anything nor can you scientifically argue. A reasonable discussion is senseless. BTW I checked the current simfoil. Something is wrong with your setup. The reynolds numbers are way higher in water The Cl/Cd numbers not match that of proper profiles. The stall simulation with which your data seem to be derived might be inappropriate according to some other sources for profile data, which I have checked it against, etc... I would be fun to discuss this with someone really able to grasp the physics behind it. But it just ennoying to talk about this, if the opposite side is not able to derive the scientific conclusions but merely shows the remaining results of the orignal creators. Your unwillingness to accept that you can not face a scientific discussion about the topic tells me all. Why not stick to what you know best building boards for happy customers, and not tell others that their science knowledge is wrong, i.e. don't step into a terrain, where your position is just silly.

Show me any brand that has done any research apart from Steve s speed channel testing. Any stuff like with the 4wfs or otherwise different angles, let alone CFD or under water filming. That is what gave me guidance where to go, from there we made prototypes on our CNC machine and then we tested, which straight away gave very good results so we were on the right track. At first I used foilSIM to get a rough idea as it works much faster than CFD which takes days of calculating a simulation. And with the simple screen shots it is easier to show what more or less happens than with the CFD results which are far more detailed. And off course I do not show all of the CFD results, just some images that give a rough idea without showing the exact angles. The program we used even gave suggestions for improvements. But in the end, the proof is in the pudding. This guy here literally said the difference was unbelievable and his improvement was visible from one day to the next, if the Reynolds number was wrong or not. That is where you are over doing it.

SchobiHH said..

I am rather interested to improve the curves of the bottom of the boards. Because the current "standard" of CAD programs, aka Shape 3d, lacks the ability to properly design the curves of the bottom. Too many bottoms I have seen are from a curve point of view "off". I have done my first boards with this improvement algorithms, and I am quite happy with the results. I started with a known bottom and board to have a good comparison. It was astonishing for me to experience how much already subtle chances in the contour of the bottom influence overall performance of the board. Now I start to move away from conventional contours and wisdom, and it will be interesting to explore this terrain. As this like most characteristics and opinions about performance on a windsurf board is subjective this is all my personal view on it. I am not a shaper and know where my limits are, but I have a very respected shaper as a friend. I just provide mathematical models and feed his knowledge and wisdom into my optimization algorithms. That is what an engineer should aim for. Create proper tools for the experts.
I know only one other person who has a similar approach, OlaH. What wonder, as there is a similar scientific background. But this is something I just do for fun, and I do not plan to commercialize it. I was frustrated to see that everybody tells you how great CAD is, but in reality the tool overwhelms the users and actually doesnt enable one to have good control about the curves and therefore about the contour of the board.
CAD in windsurfing for most people I know of still is used as if design of a board would be done by hand. So in the end, still the same conceptual mistakes are done and no real improvement comes with CAD and the possibilities of computer modeled design are not exhausted. I prefer the term to model vs. aided. because this makes the maturity of the design process clear. The computer can not be of great aid if you do not change your way of thinking and working. The crafting of a board is an engineers process and not that of an artisan. Still after 40 years of windsurf building boards the way boards are developed hasn't changed much. As you mentioned F1, there it is the same, in the beginning the magicians were artisans now they are engineers.

Now that is something we agree on. I tried these various shaping programs that are available on the market and could not design the board that I wanted. The bottom curve but also the outline, bottom shape and rail shape were difficult to get even close to be smooth. But then I remembered a dutch student from the Technical Uni in Holland who was studying ships engineering, had shown me a program once he had made for himself as a hobby shaper, which worked differently, much simpler really, only with smooth curves and only length wise. In fact it is hard to make it not smooth. So I contected him and we got together with another student from that Uni who was into CNC machines and we got together to develop a system that would design the boards how I wanted to but also do as much as possible by CNC. It offers me various mathematical curves with different flows (but always continuous curves) for the rocker line plus also various b-spline curves to be able to change twist it more for surf boards for example. And it offers various ways to change the flow in changes in the bottom shape and has various rocker, rail rocker, outline and rail shape analyses tools to indicate the flow of the curve or the changes in curvature. I can move the cross sections through the board. Plus a 3D view with different ways to see the shape, including the foot strap positions and boxes. I can also simply scale the board in length, width and thickness seperately to make 2 the same boards but one bigger and one for higher winds for example.Then I can design the inner build up, sandwich thicknesses and taper off the PVC towards the nose, reinforcements, inserts and finally the CAM part for the CNC machine where I can indicate the parameters of the machine, the tools and define the tool paths.In order to reduce waste, it calculates the template for the hotwire to cut the blanks in a close tolerance, it has an automatic positioning system for the vacuum suckers and the blank, it cuts the outline, the bottom shape, the reinforcements, the finboxes after the bottom sandwich, the rails, the deck, the deck sandwich fold out is calculated, taking the elasticity of the PVC into account to cut a minimal amount of cut outs to wrap it around the rails, the deck reinforcements and the deck inserts. Finally I can generate the g-codes for the machine. For example below are the G-codes for the fin boxes. They are actually calculated to the 0.001mm exact...... This kind of accuracy cant be achieved in foam off course but it calculates it that way and the machine has no problem with it. Takes 5 minutes to mill the fin boxes.

You start the fight. I just mentioned the the topic is overrated and physical reason shows that the effect is very likely neglectable. Also experience support my claim, because there are so many different toe in configurations out there and still good boards.

But you show me some simfoil data to explain to me that I am wrong. I have no problem if somebody has an opinion on it, you have a lot of experience and you have many people who like your boards. That is fine and you can be proud of your achievements. But this is not enough for you, you come to every forum tell everybody that you have found the holy grail.......


hello... your tone behind the screen is a bit loud... calm down. have you tried the fins with pretwist? They are giving you the opportunity to try to improve your carving and get out of your boring 2+2=4 idea...I don't think your formulas justify putting the boxes straight.
I am testing in the water and surfing those changes are really noticeable... especially in trifin (which is not the same as thruster) single fin + stabilizers. try and enjoy, leave math for work...

santi4 said..
You start the fight. I just mentioned the the topic is overrated and physical reason shows that the effect is very likely neglectable. Also experience support my claim, because there are so many different toe in configurations out there and still good boards.

But you show me some simfoil data to explain to me that I am wrong. I have no problem if somebody has an opinion on it, you have a lot of experience and you have many people who like your boards. That is fine and you can be proud of your achievements. But this is not enough for you, you come to every forum tell everybody that you have found the holy grail.......


hello... your tone behind the screen is a bit loud... calm down. have you tried the fins with pretwist? They are giving you the opportunity to try to improve your carving and get out of your boring 2+2=4 idea...I don't think your formulas justify putting the boxes straight.
I am testing in the water and surfing those changes are really noticeable... especially in trifin (which is not the same as thruster) single fin + stabilizers. try and enjoy, leave math for work...

santi4 said..
You start the fight. I just mentioned the the topic is overrated and physical reason shows that the effect is very likely neglectable. Also experience support my claim, because there are so many different toe in configurations out there and still good boards.

But you show me some simfoil data to explain to me that I am wrong. I have no problem if somebody has an opinion on it, you have a lot of experience and you have many people who like your boards. That is fine and you can be proud of your achievements. But this is not enough for you, you come to every forum tell everybody that you have found the holy grail.......


hello... your tone behind the screen is a bit loud... calm down. have you tried the fins with pretwist? They are giving you the opportunity to try to improve your carving and get out of your boring 2+2=4 idea...I don't think your formulas justify putting the boxes straight.
I am testing in the water and surfing those changes are really noticeable... especially in trifin (which is not the same as thruster) single fin + stabilizers. try and enjoy, leave math for work...

He doesn't have to calm down he's just passionate. It's refreshing to see here.

Bouke-Witchcraft said..

sheddweller said..

In theory there is no difference between theory and practice, in practice there is.

An engineering approach is wack in some fins and go try it.

I can feel the difference in my board when changing the toe angle of the side fins. It is noticeably different to me. I have done a fair bit of comparison and I even did some blind ( ISH) testing of it with friends. We and me can tell the difference.

So you stick to running your numbers and scratching your head as to why your theory fails when it meets reality, I will do the very cheap thing of throwing some fins on the board and finding out FOR SURE what works and what doesn't.

Lets put it this way: Theory should be the same as practice, however if it is not the same, it is the theory that is wrong, not the practice.

Still it is not all that hard. When I tried in 2005 with the 4wfs, it was noticably both faster and better turning with toe-in. And because it was faster, it was clear it MUST be because the water under the board flows outward. Logically because the board puts pressure on the water and the water wants to escape this pressure. It was also clear that at some depth under the board, this outward flow would go less. So the fins should need a twist but at the time I didnt know yet how to figure out how much and how to do it. When I was in Tenerife in 2006 when Boards were testing boards there and they had a Witchcraft as well, I had a chat with the head tester Ian Leonard about the fins. At the time the Witchcraft was the only trifin on test. He was surprised by the performance of the board, both for going up wind as well for turning. I explained the toe-in to him and right away he said: I get that but should the fins not have pre twist because the effect will disappear going deeper?........I said yes but I dont know how much yet. That came in 2010 with a student who had a CFD program. And in 2015 I had another student with a much better program. Those nice and colourful images were computer generated but pretty realistic, with spray, drops and air bubbles and all. Pretty much the same as the real life under water footage I had. It may still not be 100% like it is in practice but we are getting closer.

And yes, you do not NEED toe in. All anyone ever NEEDS is to sleep, eat, drink and take a dump. Boards without toe in also work. The 295 long Mistral Hookipa also worked, people had fun with it. But now we dont use it anymore. And in 10 or 20 years we will not be using boards without toe in anymore. And once people have figured out that with toe you can use bigger side fins, quads will also disappear.

"..quads will also disappear.."-wow ! man, you must be on some real quality stuff...

sheddweller said..

I mostly agree with you, my comment was directed at schobihh.

I will add ( with a little bit of insider Info) that aero and hydro dynamics are very very complicated, so complicated that F1 teams spending millions on it often get it wrong and that's for cars racing around a track, which is a hideously simple scenario compared to the complexities of a sailing/ windsurfing environment.

So you can use a CFD platform to inform yourself and help make guesses and broad brush stroke generalisations but it is not going to give you detail that you can trust.

Testing will though, and it does, as you demonstrate.

Yes and no, if you look at F1 cars, they are way more complex in shape and so will the aerodynamics be as many of these parts will also influence the flow behind. So if you change the front wing, you may need to change everything behind.

With our CFD we looked at 4 standard situations when wave sailing:
1: Going DTL without side ways pressure. Which we did at 6, 8 and 10 m/s
2: up wind (to check if all fins do a similar amount of work and there is not too much asymmetry),
3: a longer bottom turn with all 3 fins in the water (which is not far off situation 1)
4: a tight turn with the outer fin out of the water. This is especially the situation where more toe helps, with toe, you feel an excelleration and you turn tighter. So fx for smaller on shore conditions when you go a bit slower, over doing it a bit on the toe can be good fun and the board will keep speed easier.

And to get back to rockerlines, in the 80?s at school we learned that a parabolic curve is the best curve to guide the flow of a fluid. I thought that it looked roughly like the rocker line of a board so started drawing parabolic first on scale and then in full size on a sheet of plywood to find a (part of) a parabolic curve that would be similar to existing boards. Boards were always designed with a 3 part rockerline: scoop, flatter planing area and tail kick. to to turn. But I felt this was wrong, you use nearly the whole board to get planing and also to turn. So where in marketing they say: "It turns better because of the tail kick" they forget to add: "and it planes less" And the other way around for a flat mid section. What counts is the total amount of curve in the water. And then to get the smoothest behaviour, a continuously gradually changing curve must be better both for planing and turning (behaviour). Nowadays you still see some boards with a tail kick but more and more have pretty smooth rockerlines, some even match mine exactly. See here the rockerline analyses of a side shore wave 81. The distance from the red line to the dotted line is the amount of curvature, so from back to front the amount of curvature gradually reduces but even in the tail there still is some curve.

Brent in Qld said..
Dumb'n it down further, I like twinnies. Have other good boards but a good twin fin set up is the ducks guts for me.

What current board would work well as a twin?The small Evil Twins and Nuevos were great ,the former being a revelation for me.But the faster kode twin not so much to my liking.

Found this info on the internet
"Arrogance is characterized by having an exaggerated sense of our importance or abilities. Luckily, there are a few clues that can help us to spot arrogance.

First, arrogant individuals often believe that they have nothing to learn from others, so they act like know-it-alls. They fight tooth and nail to be right and to show that others are wrong. As a result, they don't listen to other people's views.

Confident people, on the other hand, have no problem listening. They're aware that they don't know everything and are happy to learn from others.

Arrogant people also like to talk about themselves. A lot. They brag about their achievements, skills and abilities, and often ignore those around them. In meetings, for example, arrogant people generally seek the spotlight. Consciously or unconsciously, they make others feel less important. They might use condescending language, talk over people, or display body language that shows a lack of interest in others."

Dude you said in 10yrs everyone will be using your massive discovery - but you made it 15 years ago and been talking about it here for 5 to10. Arrogance ? Well, somewhat if you say that when we all wake up to your idea then quads will go away.

I still have an issue with NO sailors on the PWA using twisted assy toed fins even though they do use different board shapes to us (and work out and train heaps) .... so that tells me immediately what is far more important for a waveboard. If the $$$ and glory doesn't bring your inventions to the spotlight after 15yrs I dunno what will. In any pro sport endeavour the pro's use what really works.

As I said, fkn awesome that you spent all this money on research and build great boards and even better share the results - truly thats great - but you lost me when you said you change toe by 0.1 deg . So not a full degree - 0.1deg - which is 0.197mm of toe different on a side fin. That is marketing BS that some might fall, for but aussies are famous for having a sensitive BS meter. Really, a grain of sand in the box changing toe in, can be felt?

Check the MW sails thread lol. Rider5 does not to show the proof - the guy with the extraordinary claim needs to provide extraordinary proof.


Now: tough boards - hell yes you do that well. They're great.

Mark _australia said..
Dude you said in 10yrs everyone will be using your massive discovery - but you made it 15 years ago and been talking about it here for 5 to10. Arrogance ? Well, somewhat if you say that when we all wake up to your idea then quads will go away.

I still have an issue with NO sailors on the PWA using twisted assy toed fins even though they do use different board shapes to us (and work out and train heaps) .... so that tells me immediately what is far more important for a waveboard. If the $$$ and glory doesn't bring your inventions to the spotlight after 15yrs I dunno what will. In any pro sport endeavour the pro's use what really works.

As I said, fkn awesome that you spent all this money on research and build great boards and even better share the results - truly thats great - but you lost me when you said you change toe by 0.1 deg . So not a full degree - 0.1deg - which is 0.197mm of toe different on a side fin. That is marketing BS that some might fall, for but aussies are famous for having a sensitive BS meter. Really, a grain of sand in the box changing toe in, can be felt?

Check the MW sails thread lol. Rider5 does not to show the proof - the guy with the extraordinary claim needs to provide extraordinary proof.


Now: tough boards - hell yes you do that well. They're great.

Bravo Mark !!!

That was perhaps a case of more stable mono over stretchy xply (then) and not caring about longevity
They used the stable and fragile sail

So it's not the same. Boukes fin designs have no downside. They make you turn soooo much better and in wavesailing that wins yeah?