www.surfline.com/surf-news/surfboard-fins-dummies/63557

All similar observations can be applied in wavesailing.Most important in my opinion is fin area and flex then you can add the tweaks.
Can't say I've ever experienced a scary loose twin before much more scary on a board thats to stiff.

SchobiHH said..

"in the 80?s at school we learned that a parabolic curve is the best curve to guide the flow of a fluid. "

So tell me what is a "parabolic curve".

Also where is it stated that your "magic" parabolic curve is the best for a planing hull?

I think you know what a parabolic curve is.....And I did not say that a parabolic curve is the best for a planing hull, read above what I said. I just said that I tried it at the time, now 40 years ago, CAD didn?t exist yet. And it did work better as the usual method at the time: Making a 3 stage rocker: Scoop, planing area and tail kick. Because you use the whole board for everything.Nowadays I use different curves, not parabolic but still a continuous mathematical curve. And I said that nowadays you see a lot more curves like this. Surfboards usually still have a tail kick as they do not have to plane without being on a wave. But also some wave boards still use tail kick. For wave boards in some special spots for wave riding tail kick can also be good but in general it is not the best for an alround do it all wave board.

SchobiHH said..

What is the sense of a sentence like "What counts is the total amount of curve in the water".

Yes, that was probably hard to understand without an explanation, sorry. For any given situation, for both planing and turning, what is most important is the total amount of curve in the water. For turning you want more, for planing less. Secondly is how the curve is distributed. Since, when you turn harder, you have more rail length in the water than when planing, it makes sense to make the curve continuously increase going forward. Hope that makes more sense now.

SchobiHH said..

All curves I have ever seen in CAD surf board shapes are G1 continuous and therefore "continuously gradually changing" so not only your curves.

Yes, off course shapers have improved their curves over the years. Did I say different?

SchobiHH said..

"Where in marketing they say: "It turns better because of the tail kick" they forget to add: "and it planes less"
Isn't it all about the right compromise. But you imply that again you are the one who found THE right curve. All other curves are inferior. So much arrogance is preposterous.

There have been various times such claims were made, and they are right, tail kick makes a board turn better. But for example, have a look at the promotion videos of the Fanatic quads over the years, knowing that these shapes were quite different from year to year. There also have been "revolutionary" shapes that disappeared again the next year or even after half a year were discounted big time. I think that for most people this is nothing new.

SchobiHH said..

You throw around terms without meaning. You can not really express what you do but sound like the wisdom master.I only see an imposter.

And at the same times you imply that you really are the only person who is able to build proper boards.

So you are actually bashing the whole industry and insult all the other shapers out there.

I think you are making unfounded accusations. It seems to me you have some ideas stuck in your head and find it difficult to accept new information and see your ideas thrown over. It is fine to have your own ideas but dont bash other ideas without having tried it with an open mind.

And gents, to be clear, with what ever board and fins you have, don?t let this spoil your fun on the water. It will work but keep this in the back of your head and when you get the chance give it a try.

Bouke-Witchcraft said..

I dont know if my science is "pseudo" science.

That is exactly the point, you are not able to judge it, so don't use it.

And I of course know what a parabolic curve is. I start to think that you don't. And there is no reason why it should be "special" But for you it is of no interest if what you say or not is true or not.

Your behaviour is that of a conspiracy theorist. All the others are stupid, only you know the truth. Arguments are irrelevant.

I already get emails from people in this forum telling me that they are happy that I point out, what nonsense your spreading and that you are high jacking the discussion to kill every others voice who doesn't agree with your ideology.

SchobiHH said..

Bouke-Witchcraft said..

I dont know if my science is "pseudo" science.

That is exactly the point, you are not able to judge it, so don't use it.

And I of course know what a parabolic curve is. I start to think that you don't. And there is no reason why it should be "special" But for you it is of no interest if what you say or not is true or not.

Your behaviour is that of a conspiracy theorist. All the others are stupid, only you know the truth. Arguments are irrelevant.

I already get emails from people in this forum telling me that they are happy that I point out, what nonsense your spreading and that you are high jacking the discussion to kill every others voice who doesn't agree with your ideology.

Y=X2 is a pure parabolic curve but that is far too progressive for a wave board so at the time, in full scale I think I used Y=X2/300. It does not let me do the square sign. I dont even know what is the exact name of mathematical curves I use now. The programmer made it how I explained to him how I wanted to be able to design the curve and I can adjust the progression and flow with a few variables. That is all I need to design the boards how I want to. The mathematical name is irrelevant to me.

I think I am able to judge if, that what the various students found with CFD, is matching practice quite well and the underwater footage we did. You are not able to judge that as (as I mentioned before) I only showed a very small amount of what we did. Yet you claim you are able to judge that. With the "nice and colorfull" CFD images, you can move through all the layers, you can show pressure and flow directions and speeds. With the underwater footage in slow motion with airbubbles in the water passing, we could very well see the direction of the flow in real life and also the tell tales on the fin and also the fin itself is a tell tale by looking at the twist and that was all matching very well by eye. And simply testing showed very quickly we were on the right track. As you call me an imposter, it would be fairly easy for example to go through the images on the Witchcraft facebook page and you will find the guy with the Pyramid and his name so you can ask him personally. I havent spoken to him for half a year at least. You could for example also ask the customer in Mauritius who send me his GPS data. His name is on there and he is on FB. Both paid in full so have no commercial interest.

The last CFD program was something very advanced I was told by the student. It is or was used by Airbus for example and it also had a modus to indicate where improvements can be made in the design. He had a "student license" for it, he said the normal license costs 500,000 Euro/year or so IIRC. That student was also a very smart guy. 2 years later he was the head of a naval architect buro in France with 25 engineers under him. I also have other clients who are specialists in such fields and who keep me informed.
If you blame me for being ahead of others who havent done such research, well then I am very sorry but are you not blaming the wrong person? Do you want things to improve or not? Why dont you ask other shapers or fin makers if they have done such research and their findings? As far as I know they have not and I am pretty sure they would have let us know. But yet you attack me time and again??? I think youve got some things mixed up here. Besides, you seem to get quite wound up for something that has no importance according to you. Take it easy.

We should all be sent a set of promotional twisted fins, then the science could be settled.*

* medium confidence due to high uncertainty of data and bias of the authors.

While I agree with rocker trumping everything why start the thread. Initially you were asking why production boards don't have toe in when it is so much better. Now it only makes very subtle difference. I mean wtf. Are you also saying that there is no difference between tri and quad.

What's your connection to witchcraft?

well... al recognizes less that there is a difference... we have already achieved something hahaha...
the wave boards today works very well...thank goodness...there is nothing wrong with improving sensations and putting toe in depending on what conditions it works for me... curiously I have goya and quattro production boards with straight boxes and custom with 2? toe in being the same shaper... that's why I know they know how to turn their design better... I think that with a wave board you'll look for that, right?
I wouldn't mind having a relationship with bouke at all... all my respects to him. I think it does a good job...it's good to try new things to see if they work for you...it's okay if you make a mistake...you might be surprised...
if you're curious...i like to sail single fin in summer freewave light(no waves at home) rarely in twin fin...with strong wind quad if i can.(in pozo izquierdo no dude...there I do not look toe in)..on shore thruster most days ...(depends on the wind) trifin is my prefered configuration now

Bouke-Witchcraft said..

...If you blame me for being ahead of others...

There is nothing more to say. I only feel pity.

santi4 said..

While I agree with rocker trumping everything why start the thread. Initially you were asking why production boards don't have toe in when it is so much better. Now it only makes very subtle difference. I mean wtf. Are you also saying that there is no difference between tri and quad.

What's your connection to witchcraft?

well... al recognizes less that there is a difference... we have already achieved something hahaha...
the wave boa rds today works very well...thank goodness...there is nothing wrong with improving sensations and putting toe in depending on what conditions it works for me... curiously I have goya and quattro production boards with straight boxes and custom with 2? toe in being the same shaper... that's why I know they know how to turn their design better... I think that with a wave board you'll look for that, right '?
I wouldn't mind having a relationship with bouke at all... all my respects to him. I think it does a good job...it's good to try new things to see if they work for you...it's okay if you make a mistake...you might be surprised '...
if you're curious...i like to sail single fin in summer freewave light(no waves at home) rarely in twin fin...with strong wind quad if i can.(in pozo izquierdo no dude...there I do not look toe in)..on shore thruster most days ...(depends on the wind) trifin is my prefered configuration now

this is entirely the point. It depends on what you are chasing. Do you wanna turn more or do you wanna go faster.. are your conditions dtl, onshore or bump and jump. , Exactly why some boards have toe and some don't.

we said it about 5 pages back.
boukes not trying new things. He has a cognitive bias that prevents him from doing that. he is so caught up in the world of witchcraft he excludes information that doesn't support his view point.

the Bernd video doesn't support his view point or statements. I'd suggest bouke is the last person on earth I'd ask to design me a board. Could you imagine if I asked for a twin what the response would be, or if I asked for a tri without toe.

i can promise you the people I get to do boards for me aren't limited in their ability to think in the abstract and enjoy the process of collaboration.

Mark _australia said..
Bouke you have been saying for 15yrs that its scientifically proven and showing all your modelling. The science proves it all you said.

When a physics guy showed yesterday some of your basic numbers were very very wrong, you said the science doesn't matter its the feel.

Every time somebody questions, you post a pic of guys busting out big moves - and that is not proof. Maybe you are right but aussies have a sensitive BS meter and this talk of 0.1deg being felt is just marketing rot.

All we know is toe out is bad, so I do a couple of little things on my sidies and the boards work. 90% of customs - same.

Do you have shares in MW Sails.

The numbers the physics guy was talking about was not what we were using. Only the very first images of FoilSIM had these numbers, but those images just give a very rudimentary indication of what for example the AoA or camber does. After that we continued with other far more sophisticated software that works completely different. What you do is take the CAD design of the board shape together with fins and then set that in various situations. I do not know how such software works, I think you will have to ask the programmers but maybe they will not give this information. That is why I said that it is irrevelant if the Reynolds number in those very first images were wrong as we did not use the Reynold number during the whole of the rest of the process. One CFD calculation of a situation takes 2 days on a regular fairly potential computer. Then we went through the outcome, changed things accordingly and did a new calculation. Then we made some fins on our own CNC machine and gave them to Will to test. That was 2010, I was already using 2 degree toe in since 2005. Those fins were with Naca profiles. After that I got these fins produced in China. From there we have been testing small variations by adjusting the toe on the MT fins for example, for a while we were molding our own fins so I could adapt the flex and twist in horizontal and vertical directions independently (which did not make any noticable difference and was loads more fragile) and in 2013 I found a nice little camera to do under water filming. In 2015, I had another student with the latest software and we redid this whole CFD process. Now we could also compare the findings with the underwater footage and the student fine tuned the fins according to these findings with a different profile to the Naca. We had been going through a database of foils and had found another that can handle a bit wider range of AoA.

I understand that in Australia you hardly ever get to see a Witchcraft as we do not have a world wide distribution and a limited production capacity. And as a result this information is all new to you and I can imagine it is all a bit much to process all of a sudden. You may not know much about the north of Fuerteventura either as we do not have a PWA competition here. Rene Egli who organises the freestyle and Slalom PWA in the south has negotiated exclusivity for the PWA on Fuerteventura. But here in the north it is quite different than Pozo or El Medano. We have about 15 different wave sailing spots within a 20 min drive all around the north shore, all of them for different wind directions, swells or tides. We sail on average 50% port and 50% starboard tack. Most of these spots being point breaks with a channel. 90% of groundswells come from the NW, which do not reach Pozo or el Medano. Plus the volcanic reefs here are quite efficient in picking up swells. When we get a 13 second 2.2m swell it is mast high. With a rare 20 seconds and 4m swell double mast. I remember the first day in WA and there was a 22second 6m swell forecasted, I thought wow, that must get really really big. But then at Scarborough on the beach, the waves were like 1.5m and you saw huge waves breaking on the horizon. The continental shelf in WA filters out a lot of the bigger swells. And also we are the first stop for the wind swells created by the summer trade winds blowing along the Moroccan coast. When Pozo has 2m waves, Glass Beach is 4m. Our cross on jumping spot is Punt Blanca in the NW. Winds are usually light here but with the point breaks that is no problem and even better. Most guys just have 2 sails and use the bigger 80% of the time. We get around 100 to 150 wave sailing days per year with on average a high wave quality. That all combined takes a toll on equipment and basically you can?t sell rubbish to locals. Some 8 years ago an Italian started an RRD rental centre here close by but he went bust on damaged equipment, he was selling new sails to locals for 200? but after a while still nobody wanted them. He then moved to el Medano. My first year here in 1993 I broke 9 SDM masts and the year after 12. So I got Powerex RDM masts from the US. I had seen them on the Boat show in D?sseldorf in Germany in 1988 and understood the physics behind it. At the time I was the first in Europe starting to import them. Everyone who saw them said that cant work. But the first ones lasted 2 years. And now all wave masts are RDM. I also soon started experimenting with Dyneema (which was a dutch invention) because I was repairing my board nearly every week.We make around 60 boards per year and at the moment have an 8 months waiting list. We sell the vast majority in Europe where Holland is our biggest market with me being dutch. You see everywhere that chauvinism plays a part, In Italy you will tipically see more RRD, in France more Exocet or Tabou, in Sweden more Simmer and in Australia more Severne or Starboard. In Holland you have Wijk aan Zee, one of the best wave sailing spots in Holland due to the dam of the port of Amsterdam up wind reducing the current and cleaning up the waves. Due to the density of population of 17-20 million people within a 2 hour drive, it is probably the most frequented spot in the world. On a good day you may see 300 wave sailors out. Also for many western germans it is the go to spot. There and on other dutch spots, Witchcraft is one of the main brands seen and no one calls it BS. But, besides the Canary Islands off course, we also sell boards (and sails) to Germany, the UK, Belgium, France, Spain, Italy, Scandinavia, Greece and occasionally some boards to the US or Chile. The guy in Chile (the Ezzy dealer there) especially came over in 2011 to test boards before ordering some. Witchcraft is hardly ever featured in magazines either. Only the UK magazines have done some articles on our innovations between 2007 and 2018 or have been testing boards or sails. Years ago I had some guys of the dutch magazine visiting the island and they were stoked, wrote a cool article and then said: it will cost you 2000? to publish it...... After the last time I gave a Haka ST 90 to Windsurf.co.uk, the test editor wanted to buy it but I needed it back in rental as I already had bookings for it and no time to make another. But the tests got more and more meaningless, I tried to get them to give scores to make it more clear what the differences are between the boards or sails. But they said they did not want to have to hassle with the various marketing managers over a poor score, so I stopped giving gear to test. The test editor of windsurfingukmag.co.uk, bought a Reaper that he also uses for sail testing and we gave him a set of used sails to use for board and foil testing. But that magazine died as well and he now runs a foil shop.But if you are open minded and into technical stuff, you may find our blog interesting: witchcraft.nu/new-blog/

Bouke-Witchcraft said..

Gestalt said..

santi4 said..

While I agree with rocker trumping everything why start the thread. Initially you were asking why production boards don't have toe in when it is so much better. Now it only makes very subtle difference. I mean wtf. Are you also saying that there is no difference between tri and quad.

What's your connection to witchcraft?

well... al recognizes less that there is a difference... we have already achieved something hahaha...
the wave boa rds today works very well...thank goodness...there is nothing wrong with improving sensations and putting toe in depending on what conditions it works for me... curiously I have goya and quattro production boards with straight boxes and custom with 2? toe in being the same shaper... that's why I know they know how to turn their design better... I think that with a wave board you'll look for that, right '?
I wouldn't mind having a relationship with bouke at all... all my respects to him. I think it does a good job...it's good to try new things to see if they work for you...it's okay if you make a mistake...you might be surprised '...
if you're curious...i like to sail single fin in summer freewave light(no waves at home) rarely in twin fin...with strong wind quad if i can.(in pozo izquierdo no dude...there I do not look toe in)..on shore thruster most days ...(depends on the wind) trifin is my prefered configuration now

this is entirely the point. It depends on what you are chasing. Do you wanna turn more or do you wanna go faster.. are your conditions dtl, onshore or bump and jump. , Exactly why some boards have toe and some don't.

we said it about 5 pages back.
boukes not trying new things. He has a cognitive bias that prevents him from doing that. he is so caught up in the world of witchcraft he excludes information that doesn't support his view point.

the Bernd video doesn't support his view point or statements. I'd suggest bouke is the last person on earth I'd ask to design me a board. Could you imagine if I asked for a twin what the response would be, or if I asked for a tri without toe.

i can promise you the people I get to do boards for me aren't limited in their ability to think in the abstract and enjoy the process of collaboration.

About the Bernd video. First off all, Flikkas have some toe-in, I have measured some. Secondly, IIRC that board was especially shaped for that comp so it may have had even more toe-in. Just like Nic Baker won Baja once on a board that was especially shaped for that comp. It looks similarish to the board Kauli was using in PP in 2007, short, wide in the middle and loads of rocker. These boards are hardly sailable in other conditions or by other sailors. Third, in such clean cross off shore conditions, it is much easier to keep speed on a board with high rocker.

When people order a custom board, the customer does not have to decide the shape, I want to know what they want the board to do. How they want it to perform, for example in comparison to other known shapes. Depending on the customer we can talk about how to achieve this but not everyone knows the finer details of shapes and in the end I am responsible and I give guarantee on the shape as well. If a customer has special wishes, indeed it will depend on if I think it will work or not whether I will take on the order. I have a waiting list and do not want to waste my time on what I think will be a suboptimal board. For example I will not make a quad as I know my trifin will be better. I have made some twin freestyle boards in the past and I can see why Philip K?ster is riding twins in Pozo for his slidey freestyle moves. So in such a case I would make a twin. Last year I also made a twin freeride board for shallow and choppy waters with a fairly strong rip. That was a bit of a challenge to get the trim adapted to the twin so I fitted it with extra plugs and a longer mast track than I normally do.I may make a trifin without toe but on the condition the customer gets fins without toe and my pretwisted fins with toe to test against eachother. That is easy to do. But I have never had any such request.

Yawn.

I'd buy a Flikka long before I'd buy a witchcraft. For starters they work with a range of fins

Bouke-Witchcraft said..

I understand that in Australia you hardly ever get to see a Witchcraft as we do not have a world wide distribution and a limited production capacity. And as a result this information is all new to you and I can imagine it is all a bit much to process all of a sudden.

Yes sorry I live in a backwater where windsurfing is never seen and no development happens here. We are cognitively limited and can't process all this information over such a short 15yrs that you have been educating us.

I'm out.

Rango said..
Open minded but won't make a quad.

I'm done.

I think that should say "can't"

I've played around with fin angle on quads quads CAN be improved with different fin angles specific to quads. They can't be improved using the same angles used in thrusters.
No I'm not going to waste my time explaining my ideas trials and results, I'm happy with what I do for my own boards, how they feel to me and selfishly that's all that matters to me.
It's all about me me me me me ... Ha ha

"Cognitive bias" I love it.

^ Almost, but not quite. Bourke produced examples of his technical research that are convincing unless you think he faked the whole thing. And from what some have written here they seem to be burdened by baggage that qualifies their opinions in a less than flattering way.

GasHazard said..
^ Almost, but not quite. Bourke produced examples of his technical research that are convincing unless you think he faked the whole thing. And from what some have written here they seem to be burdened by baggage that qualifies their opinions in a less than flattering way.

it is not faked. But it is meaningless in the hands of a non expert. Everbody with some decent knowledge can produce this colourful pictures. But to make them convincing there is much more to it some nice little pictures. And what makes it worth is, that Bourke throws smoke candles where ever he can. Decent research would result in a research paper, which explains what had been done and on what scientific basis the experimental setup has been developed. As this was only a student during I don't know how many weeks he spent, work, I highly doubt that he was able to produce proper research results. Unfortuantely. I would have loved to read what had been done, and how this could have been further developed. But it seems that the only reason why this had been done is to use it as marketing material and not to get any closer to the "truth". At least I have not read anything that convinces me that it is different.

SchobiHH said..


it is not faked. But it is meaningless in the hands of a non expert. Everbody with some decent knowledge can produce this colourful pictures. But to make them convincing there is much more to it some nice little pictures. And what makes it worth is, that Bourke throws smoke candles where ever he can. Decent research would result in a research paper, which explains what had been done and on what scientific basis the experimental setup has been developed. As this was only a student during I don't know how many weeks he spent, work, I highly doubt that he was able to produce proper research results. Unfortuantely. I would have loved to read what had been done, and how this could have been further developed. But it seems that the only reason why this had been done is to use it as marketing material and not to get any closer to the "truth". At least I have not read anything that convinces me that it is different.

I think you are maybe a bit behind the times with this.
FEA is now a standard design tool for non specialist engineers. They use it daily and they use it daily without the underlying mathematical understanding of the programs. They probably touched on the underlying maths in a couple of lectures as undergrads but that's about it. BUT the key is they do not solely rely on it, and it will go out to specialists in the field for critical parts, or specialist areas and most importantly of all functional testing of physical items. FEA ( inc fluid flow) modules are included in programs like solidworks, which is a farily low budget design suite. I think Delft University will certainly have the most expensive full on Software, with lecturers fully conversant in its use. My experience of such places is that the lecturers helped out a lot with these sort of interesting "fun" student projects, and particularly when the project is in collaboration with an industrial partner, like Bouke. So i would not expect the results to be completely micky mouse.
CFD is much more complex than basic FEA, but the trend is broadly similar. The tools are getting much easier to use for non specialists. The difficulty is the non specialist has no idea of the underlying assumptions or of the gross simplifications necessary to model an extremely complex environment.
But still i would say t is useful to test ideas, particularly in the case of windsurf fins where it is trivial and cheap to full scale test the results and verify. This is ( or should be) the overriding engineering approach when using it, be sceptical of the results and , verify verify verify.
also Toed n twisted n canted fins isn't cutting edge science, it isn't even new, so i dont see why anyone would be doing research papers on it- a product development project for an undergrad sure, but research papers? really?