Select to expand quotebubbas said..AlexF said..
I always wonder when I read the discussions about toe in why a guy like Keith doesn't use it on his Quatro and Goya shapes.
Seems to be a reason and I'm sure it's not that he's willing to use only the second best solution for his boards.
I think KTs own boards, as well as the other team tiders boards, have toe in. At least all the quatro custom boards I have seen have some toe in, a little more than 1 degree. Boxes on production boards straight. I dont know why the difference, maybe they dont thrust cobra?
Yes, the Quatro custom boards that I have measured when we had them in for repair had 2 deg toe-in. The production dont. No idea why.
Select to expand quotestonny said..
Can anyone explain to me why quad fin setups are considered slow, draggy and planted on a windsurfer yet super fast and lively on a surfboard ?
Simple answer: Toe-in. Not just on the side fins but also on the trailing fins.
Select to expand quoteBouke-Witchcraft said..SchobiHH said..Bouke-Witchcraft said..
I can see why a guy like Koster likes twin fins as they are easy to break out when doing skaty moves on sloppy waves. Trifins and quads have more grip due to having more fin area on the rail. But most boards have small side fins and thus trifins need to have a big centre fin. Quads have more drag due to having more fins. Trifins or thrusters with three similar sized trifins are at least as loose and grippy. I use for example 3 x 12.5 or 12.5+14cm under an 80L, 13.5+14 under a 90-95L or 14.5+15.5 under an 105L. But when you have bigger side fins, it becomes more important they are set up correctly. The water flow under the board is directed from the centre outward so the further away from the centre, the more toe-in you need. But this effect is the biggest directly under the board and diinishes over the length of the fin. We use 2? toe-in and then the fins have another 2.5? toe-in in the base. The fins then twist back to pretty much zero toe-in at the tip, depending on the size of the fin. This may not seem much but water has a lot of power. We just can?t see it.
You can see the same principle on the wings of wind turbines, propellors or our sails: The angle of attack changes over the length of the foil thus the foil should twist over its length accordingly.
Going down a wave without lateral pressure of the sail, in this situation you do not want any of the fins to give lift to reduce drag and to help initiate the turn:
Does this sound complicated? Yes, there is a LOT more to it then just a centre fin. But this is what it is, it simply is what happens because of physical laws. The same physical laws that allow us to windsurf in the first place and if you want to do it right, there is no way around it. The first planes also flew but we still learned a lot more after that.
OMG. So many colour pictures. Do you know what CFD stands for: "colourfull fluid dynamics". That is the quote of a professor for fluid dynamics. I.e. CFD is nice to illustrate behaviours. But never is a proof apart from a real experiment.
That means. The CFD simulations need to be tested against "towing tank" experiments for example. Then you can calibrate the CFD and then the CFD predictions are to some degree meaningfull. I don't see how you could have done a real life test like a towing tank or similar for windsurf boards.
Regarding "that are physical laws". As a physicist with a university degree having discussed the topic with some real experts, i.e. professors, one thing is for sure. The reason why yours and also the the exact opposite approach works is that the effect is neglectable at most minimal. So is just only psychology or even marketing?
Well first of all, in spite of what your professor says, CFD nowadays is ahead of towing tank testing, which is far from the real full size stuff out at sea and as a result, test results are not reliable. Nowadays you can set the sea state, wave heighth and length and period, even various through eachother, like you can have out at sea. The guy who did this CFD research for me in 2015 got a super high grade for his work and he now runs a naval architecture design agency in France with 25 engineers and experts under him, pretty clever guy. And I know quite a few more experts in this field, students on internships and their professors, former interns plus a few of my customers have high positions in marine research institutes. Nowadays, many things are developed even just using CFD including wind turbines and airplanes. Simply as it is more accurate.
As for practice testing, in 2005 I had a few boards with the 4wfs, which allows you to turn the fins within a minute. Within a day testing in clean light wind conditions we figured out that about 2? toe-in was not only turning better, it was also faster.
Then, there are those who have gone from one day using paralel fins to my pre-twisted fins the day after. "Amazing" is what the last one said, I can give you his phone nr if you want.
But is it that hard to understand what happens under a board? When you were a kid, didn?t you jump in puddles and the water would fly everywhere? Now if you would let a board float in a pool and you would land vertically on it? All the same thing, the water wants to escape the pressure we apply on it, just when we are planing, there is a big forward component in the movement but there still is a sidewards component as well. And anyone can imagine that if you are 1m under water the water is not pushed away anymore. When in 2007 I had a board in the test of Boards magazine, I explained their head tester Ian Leonard why a board needs toe-in, he figured out right away that fins would actually needed to be twisted as well. He promised me to keep it to himself.
Then if you are a fan boy of this or that shaper since many years, I can understand that it may be hard to realise you were wrong and for some people this may lead going into denial even if the facts are staring right at them. For sure there is a name in psychology for this phenomenon. From your forum name I figure you are a german from Hamburg? I just had a long time customer from Hamburg in today picking up his new flex tail. And we were chatting about all the fin designs I had over the years and he said the first red and black pre twisted fins in 2010 were big leap forward, these RTM fins were just fragile when hitting bottom.
This was a prototype flex tail with those fins. This one had adjustable flex through airpressure but it was too hard to keep the airchambers sealed. Some ideas are good in theory but it should also be practically doable and durable.
Sorry, but your remark about towing tanks clearly shows that you do not understand the intrinsic relationship between the experimental proof and simulation algorithms. The only reason why CFD is working so good now for naval boats and wind turbines is that the CFD was calibrated with wind tunnels and towing tanks. And this is why I say, that your CFD is at most of qualitiave value but never of a quantative one. But of course for marketing it always sells good to have colour pictures which show some highly sophisticated magical pseudo-science. And I mean pseudo science because it is not validated scientifially. Therefore it is not a proof but only a hypotheties nothing more. But how can the customers tell? They can not, because you need to have a science background to understand . As from what I read, you can not tell the difference either.
I am not saying that what you say is wrong, and clearly the water under the hull runs not only from nose to tail but flows sideways but as you already found out the layer of water where this happens is not very deep. Therefore you came up with your twisted fins. BTW for this you do not need CFD but only some simple science logic. But what I say is that you are over exaggerating the effect that the toe in has wrt to drag. The difference between 0 and 2 degree is minimal, especially with the normal side fins of 10cm. So that mere mortal will not tell you the difference. Of course you will say different, but that is clearly biased.
Select to expand quotesprayblaze said..
I never thought that fin selection is as complicated as brain surgery- who needs that and even if true-so what ? I have tried twins, trusters quads. Not to make things complicated I have picked quads(THE ultimate multifin sensation) imho. Watching Brawzinho and Levi destroying Pozo and Hookipa on production boards -Marcilio on quad and Levi quad/tri is enough said for me, a mere mortal, regarding the evergoing production vs. custom dilemma. Merry X mas to everyone and let this Covid nightmare remain in 2020!
Do you really think braw and Levi sail production boards at Hookipa?!
The shapes they use are way more radical. That being said, at least braw's shapes are just highly tweaked versions of productions. So ideally his hookipa board will have similar looking turns at hookipa to his turns in crap waves on a productions
Select to expand quoteBouke-Witchcraft said..SchobiHH said..Bouke-Witchcraft said..
I can see why a guy like Koster likes twin fins as they are easy to break out when doing skaty moves on sloppy waves. Trifins and quads have more grip due to having more fin area on the rail. But most boards have small side fins and thus trifins need to have a big centre fin. Quads have more drag due to having more fins. Trifins or thrusters with three similar sized trifins are at least as loose and grippy. I use for example 3 x 12.5 or 12.5+14cm under an 80L, 13.5+14 under a 90-95L or 14.5+15.5 under an 105L. But when you have bigger side fins, it becomes more important they are set up correctly. The water flow under the board is directed from the centre outward so the further away from the centre, the more toe-in you need. But this effect is the biggest directly under the board and diinishes over the length of the fin. We use 2? toe-in and then the fins have another 2.5? toe-in in the base. The fins then twist back to pretty much zero toe-in at the tip, depending on the size of the fin. This may not seem much but water has a lot of power. We just can?t see it.
You can see the same principle on the wings of wind turbines, propellors or our sails: The angle of attack changes over the length of the foil thus the foil should twist over its length accordingly.
Going down a wave without lateral pressure of the sail, in this situation you do not want any of the fins to give lift to reduce drag and to help initiate the turn:
Does this sound complicated? Yes, there is a LOT more to it then just a centre fin. But this is what it is, it simply is what happens because of physical laws. The same physical laws that allow us to windsurf in the first place and if you want to do it right, there is no way around it. The first planes also flew but we still learned a lot more after that.
OMG. So many colour pictures. Do you know what CFD stands for: "colourfull fluid dynamics". That is the quote of a professor for fluid dynamics. I.e. CFD is nice to illustrate behaviours. But never is a proof apart from a real experiment.
That means. The CFD simulations need to be tested against "towing tank" experiments for example. Then you can calibrate the CFD and then the CFD predictions are to some degree meaningfull. I don't see how you could have done a real life test like a towing tank or similar for windsurf boards.
Regarding "that are physical laws". As a physicist with a university degree having discussed the topic with some real experts, i.e. professors, one thing is for sure. The reason why yours and also the the exact opposite approach works is that the effect is neglectable at most minimal. So is just only psychology or even marketing?
Well first of all, in spite of what your professor says, CFD nowadays is ahead of towing tank testing, which is far from the real full size stuff out at sea and as a result, test results are not reliable. Nowadays you can set the sea state, wave heighth and length and period, even various through eachother, like you can have out at sea. The guy who did this CFD research for me in 2015 got a super high grade for his work and he now runs a naval architecture design agency in France with 25 engineers and experts under him, pretty clever guy. And I know quite a few more experts in this field, students on internships and their professors, former interns plus a few of my customers have high positions in marine research institutes. Nowadays, many things are developed even just using CFD including wind turbines and airplanes. Simply as it is more accurate.
As for practice testing, in 2005 I had a few boards with the 4wfs, which allows you to turn the fins within a minute. Within a day testing in clean light wind conditions we figured out that about 2? toe-in was not only turning better, it was also faster.
Then, there are those who have gone from one day using paralel fins to my pre-twisted fins the day after. "Amazing" is what the last one said, I can give you his phone nr if you want.
But is it that hard to understand what happens under a board? When you were a kid, didn?t you jump in puddles and the water would fly everywhere? Now if you would let a board float in a pool and you would land vertically on it? All the same thing, the water wants to escape the pressure we apply on it, just when we are planing, there is a big forward component in the movement but there still is a sidewards component as well. And anyone can imagine that if you are 1m under water the water is not pushed away anymore. When in 2007 I had a board in the test of Boards magazine, I explained their head tester Ian Leonard why a board needs toe-in, he figured out right away that fins would actually needed to be twisted as well. He promised me to keep it to himself.
Then if you are a fan boy of this or that shaper since many years, I can understand that it may be hard to realise you were wrong and for some people this may lead going into denial even if the facts are staring right at them. For sure there is a name in psychology for this phenomenon. From your forum name I figure you are a german from Hamburg? I just had a long time customer from Hamburg in today picking up his new flex tail. And we were chatting about all the fin designs I had over the years and he said the first red and black pre twisted fins in 2010 were big leap forward, these RTM fins were just fragile when hitting bottom.
This was a prototype flex tail with those fins. This one had adjustable flex through airpressure but it was too hard to keep the airchambers sealed. Some ideas are good in theory but it should also be practically doable and durable.
Forgive me bouke, but the bit I struggle with here about your bigger front fins x medium back fin and your flextails etc is this: why has nobody else thought of it? You're so insistent that your way is the best, that everybody who tries it is blown away, so how come word hasn't reached KT's ears? How come braw, Levi etc and all the worlds best sailors haven't tried your concepts and been blown away by them?? I'm not saying you're wrong, because I'm no expert whereas you seem to at least do a good job of sounding like one, but it just seems to me to be the height of arrogance to sit there and say, "I'm right, everybody else is wrong and/or deluded".
Select to expand quoteSchobiHH said..
Sorry, but your remark about towing tanks clearly shows that you do not understand the intrinsic relationship between the experimental proof and simulation algorithms. The only reason why CFD is working so good now for naval boats and wind turbines is that the CFD was calibrated with wind tunnels and towing tanks. And this is why I say, that your CFD is at most of qualitiave value but never of a quantative one. But of course for marketing it always sells good to have colour pictures which show some highly sophisticated magical pseudo-science. And I mean pseudo science because it is not validated scientifially. Therefore it is not a proof but only a hypotheties nothing more. But how can the customers tell? They can not, because you need to have a science background to understand . As from what I read, you can not tell the difference either.
I am not saying that what you say is wrong, and clearly the water under the hull runs not only from nose to tail but flows sideways but as you already found out the layer of water where this happens is not very deep. Therefore you came up with your twisted fins. BTW for this you do not need CFD but only some simple science logic. But what I say is that you are over exaggerating the effect that the toe in has wrt to drag. The difference between 0 and 2 degree is minimal, especially with the normal side fins of 10cm. So that mere mortal will not tell you the difference. Of course you will say different, but that is clearly biased.
Well I know people who have explained the relation ship and said that the results that towing tanks nowadays are giving are more off than CFD. And we did CFD over the past 10 years in 3 diffferent projects using different programs and each time the result was very similar with less than 10% differences. Besides, what you havent seen is the under water footage in slow motion. You can see by tiny airbubbles in the water at which level the water flows in which direction. Which happens to be very similar to what CFD has given. And like you say yourself, that it must be more or less like I say, so even if CFD would be 50% off, the result is still better than doing nothing. As shown before, the difference between 2 and 0 degrees is that the drag is increases 3 fold. Indeed with 10cm fins in the total amount it is not that much even if still noticable. However you then are limited to 10cm fins. I am not. I have 5 different sizes of side fins, from 10.5 to 15.5 for 130L wave boards. That means that with the fins being asymmetrical, I need to have 10 different fins in stock just for the side fins alone. 12.5 and 13.5 are the most frequently used sizes. Just came off the water at Majanicho, 22knots cross off shore and 2-3m waves. 5.0 Slayer (was a bit big on the wave with the wind being a touch too off) 95L flex tail and 14+13.5 fins.
Select to expand quoteRuaraidhK257 said..Bouke-Witchcraft said..SchobiHH said..Bouke-Witchcraft said..
I can see why a guy like Koster likes twin fins as they are easy to break out when doing skaty moves on sloppy waves. Trifins and quads have more grip due to having more fin area on the rail. But most boards have small side fins and thus trifins need to have a big centre fin. Quads have more drag due to having more fins. Trifins or thrusters with three similar sized trifins are at least as loose and grippy. I use for example 3 x 12.5 or 12.5+14cm under an 80L, 13.5+14 under a 90-95L or 14.5+15.5 under an 105L. But when you have bigger side fins, it becomes more important they are set up correctly. The water flow under the board is directed from the centre outward so the further away from the centre, the more toe-in you need. But this effect is the biggest directly under the board and diinishes over the length of the fin. We use 2? toe-in and then the fins have another 2.5? toe-in in the base. The fins then twist back to pretty much zero toe-in at the tip, depending on the size of the fin. This may not seem much but water has a lot of power. We just can?t see it.
You can see the same principle on the wings of wind turbines, propellors or our sails: The angle of attack changes over the length of the foil thus the foil should twist over its length accordingly.
Going down a wave without lateral pressure of the sail, in this situation you do not want any of the fins to give lift to reduce drag and to help initiate the turn:
Does this sound complicated? Yes, there is a LOT more to it then just a centre fin. But this is what it is, it simply is what happens because of physical laws. The same physical laws that allow us to windsurf in the first place and if you want to do it right, there is no way around it. The first planes also flew but we still learned a lot more after that.
OMG. So many colour pictures. Do you know what CFD stands for: "colourfull fluid dynamics". That is the quote of a professor for fluid dynamics. I.e. CFD is nice to illustrate behaviours. But never is a proof apart from a real experiment.
That means. The CFD simulations need to be tested against "towing tank" experiments for example. Then you can calibrate the CFD and then the CFD predictions are to some degree meaningfull. I don't see how you could have done a real life test like a towing tank or similar for windsurf boards.
Regarding "that are physical laws". As a physicist with a university degree having discussed the topic with some real experts, i.e. professors, one thing is for sure. The reason why yours and also the the exact opposite approach works is that the effect is neglectable at most minimal. So is just only psychology or even marketing?
Well first of all, in spite of what your professor says, CFD nowadays is ahead of towing tank testing, which is far from the real full size stuff out at sea and as a result, test results are not reliable. Nowadays you can set the sea state, wave heighth and length and period, even various through eachother, like you can have out at sea. The guy who did this CFD research for me in 2015 got a super high grade for his work and he now runs a naval architecture design agency in France with 25 engineers and experts under him, pretty clever guy. And I know quite a few more experts in this field, students on internships and their professors, former interns plus a few of my customers have high positions in marine research institutes. Nowadays, many things are developed even just using CFD including wind turbines and airplanes. Simply as it is more accurate.
As for practice testing, in 2005 I had a few boards with the 4wfs, which allows you to turn the fins within a minute. Within a day testing in clean light wind conditions we figured out that about 2? toe-in was not only turning better, it was also faster.
Then, there are those who have gone from one day using paralel fins to my pre-twisted fins the day after. "Amazing" is what the last one said, I can give you his phone nr if you want.
But is it that hard to understand what happens under a board? When you were a kid, didn?t you jump in puddles and the water would fly everywhere? Now if you would let a board float in a pool and you would land vertically on it? All the same thing, the water wants to escape the pressure we apply on it, just when we are planing, there is a big forward component in the movement but there still is a sidewards component as well. And anyone can imagine that if you are 1m under water the water is not pushed away anymore. When in 2007 I had a board in the test of Boards magazine, I explained their head tester Ian Leonard why a board needs toe-in, he figured out right away that fins would actually needed to be twisted as well. He promised me to keep it to himself.
Then if you are a fan boy of this or that shaper since many years, I can understand that it may be hard to realise you were wrong and for some people this may lead going into denial even if the facts are staring right at them. For sure there is a name in psychology for this phenomenon. From your forum name I figure you are a german from Hamburg? I just had a long time customer from Hamburg in today picking up his new flex tail. And we were chatting about all the fin designs I had over the years and he said the first red and black pre twisted fins in 2010 were big leap forward, these RTM fins were just fragile when hitting bottom.
This was a prototype flex tail with those fins. This one had adjustable flex through airpressure but it was too hard to keep the airchambers sealed. Some ideas are good in theory but it should also be practically doable and durable.
Forgive me bouke, but the bit I struggle with here about your bigger front fins x medium back fin and your flextails etc is this: why has nobody else thought of it? You're so insistent that your way is the best, that everybody who tries it is blown away, so how come word hasn't reached KT's ears? How come braw, Levi etc and all the worlds best sailors haven't tried your concepts and been blown away by them?? I'm not saying you're wrong, because I'm no expert whereas you seem to at least do a good job of sounding like one, but it just seems to me to be the height of arrogance to sit there and say, "I'm right, everybody else is wrong and/or deluded".
Sorry but how should I know? I can think of various reasons but that would still be guessing. The best is to ask them.
Select to expand quoteBouke-Witchcraft said..RuaraidhK257 said..Bouke-Witchcraft said..SchobiHH said..Bouke-Witchcraft said..
I can see why a guy like Koster likes twin fins as they are easy to break out when doing skaty moves on sloppy waves. Trifins and quads have more grip due to having more fin area on the rail. But most boards have small side fins and thus trifins need to have a big centre fin. Quads have more drag due to having more fins. Trifins or thrusters with three similar sized trifins are at least as loose and grippy. I use for example 3 x 12.5 or 12.5+14cm under an 80L, 13.5+14 under a 90-95L or 14.5+15.5 under an 105L. But when you have bigger side fins, it becomes more important they are set up correctly. The water flow under the board is directed from the centre outward so the further away from the centre, the more toe-in you need. But this effect is the biggest directly under the board and diinishes over the length of the fin. We use 2? toe-in and then the fins have another 2.5? toe-in in the base. The fins then twist back to pretty much zero toe-in at the tip, depending on the size of the fin. This may not seem much but water has a lot of power. We just can?t see it.
You can see the same principle on the wings of wind turbines, propellors or our sails: The angle of attack changes over the length of the foil thus the foil should twist over its length accordingly.
Going down a wave without lateral pressure of the sail, in this situation you do not want any of the fins to give lift to reduce drag and to help initiate the turn:
Does this sound complicated? Yes, there is a LOT more to it then just a centre fin. But this is what it is, it simply is what happens because of physical laws. The same physical laws that allow us to windsurf in the first place and if you want to do it right, there is no way around it. The first planes also flew but we still learned a lot more after that.
OMG. So many colour pictures. Do you know what CFD stands for: "colourfull fluid dynamics". That is the quote of a professor for fluid dynamics. I.e. CFD is nice to illustrate behaviours. But never is a proof apart from a real experiment.
That means. The CFD simulations need to be tested against "towing tank" experiments for example. Then you can calibrate the CFD and then the CFD predictions are to some degree meaningfull. I don't see how you could have done a real life test like a towing tank or similar for windsurf boards.
Regarding "that are physical laws". As a physicist with a university degree having discussed the topic with some real experts, i.e. professors, one thing is for sure. The reason why yours and also the the exact opposite approach works is that the effect is neglectable at most minimal. So is just only psychology or even marketing?
Well first of all, in spite of what your professor says, CFD nowadays is ahead of towing tank testing, which is far from the real full size stuff out at sea and as a result, test results are not reliable. Nowadays you can set the sea state, wave heighth and length and period, even various through eachother, like you can have out at sea. The guy who did this CFD research for me in 2015 got a super high grade for his work and he now runs a naval architecture design agency in France with 25 engineers and experts under him, pretty clever guy. And I know quite a few more experts in this field, students on internships and their professors, former interns plus a few of my customers have high positions in marine research institutes. Nowadays, many things are developed even just using CFD including wind turbines and airplanes. Simply as it is more accurate.
As for practice testing, in 2005 I had a few boards with the 4wfs, which allows you to turn the fins within a minute. Within a day testing in clean light wind conditions we figured out that about 2? toe-in was not only turning better, it was also faster.
Then, there are those who have gone from one day using paralel fins to my pre-twisted fins the day after. "Amazing" is what the last one said, I can give you his phone nr if you want.
But is it that hard to understand what happens under a board? When you were a kid, didn?t you jump in puddles and the water would fly everywhere? Now if you would let a board float in a pool and you would land vertically on it? All the same thing, the water wants to escape the pressure we apply on it, just when we are planing, there is a big forward component in the movement but there still is a sidewards component as well. And anyone can imagine that if you are 1m under water the water is not pushed away anymore. When in 2007 I had a board in the test of Boards magazine, I explained their head tester Ian Leonard why a board needs toe-in, he figured out right away that fins would actually needed to be twisted as well. He promised me to keep it to himself.
Then if you are a fan boy of this or that shaper since many years, I can understand that it may be hard to realise you were wrong and for some people this may lead going into denial even if the facts are staring right at them. For sure there is a name in psychology for this phenomenon. From your forum name I figure you are a german from Hamburg? I just had a long time customer from Hamburg in today picking up his new flex tail. And we were chatting about all the fin designs I had over the years and he said the first red and black pre twisted fins in 2010 were big leap forward, these RTM fins were just fragile when hitting bottom.
This was a prototype flex tail with those fins. This one had adjustable flex through airpressure but it was too hard to keep the airchambers sealed. Some ideas are good in theory but it should also be practically doable and durable.
Forgive me bouke, but the bit I struggle with here about your bigger front fins x medium back fin and your flextails etc is this: why has nobody else thought of it? You're so insistent that your way is the best, that everybody who tries it is blown away, so how come word hasn't reached KT's ears? How come braw, Levi etc and all the worlds best sailors haven't tried your concepts and been blown away by them?? I'm not saying you're wrong, because I'm no expert whereas you seem to at least do a good job of sounding like one, but it just seems to me to be the height of arrogance to sit there and say, "I'm right, everybody else is wrong and/or deluded".
Sorry but how should I know? I can think of various reasons but that would still be guessing. The best is to ask them.
Humour me, Bouke, and expand on the various reasons you can think of! ;)
Select to expand quoteRuaraidhK257 said..Bouke-Witchcraft said..SchobiHH said..Bouke-Witchcraft said..
I can see why a guy like Koster likes twin fins as they are easy to break out when doing skaty moves on sloppy waves. Trifins and quads have more grip due to having more fin area on the rail. But most boards have small side fins and thus trifins need to have a big centre fin. Quads have more drag due to having more fins. Trifins or thrusters with three similar sized trifins are at least as loose and grippy. I use for example 3 x 12.5 or 12.5+14cm under an 80L, 13.5+14 under a 90-95L or 14.5+15.5 under an 105L. But when you have bigger side fins, it becomes more important they are set up correctly. The water flow under the board is directed from the centre outward so the further away from the centre, the more toe-in you need. But this effect is the biggest directly under the board and diinishes over the length of the fin. We use 2? toe-in and then the fins have another 2.5? toe-in in the base. The fins then twist back to pretty much zero toe-in at the tip, depending on the size of the fin. This may not seem much but water has a lot of power. We just can?t see it.
You can see the same principle on the wings of wind turbines, propellors or our sails: The angle of attack changes over the length of the foil thus the foil should twist over its length accordingly.
Going down a wave without lateral pressure of the sail, in this situation you do not want any of the fins to give lift to reduce drag and to help initiate the turn:
Does this sound complicated? Yes, there is a LOT more to it then just a centre fin. But this is what it is, it simply is what happens because of physical laws. The same physical laws that allow us to windsurf in the first place and if you want to do it right, there is no way around it. The first planes also flew but we still learned a lot more after that.
OMG. So many colour pictures. Do you know what CFD stands for: "colourfull fluid dynamics". That is the quote of a professor for fluid dynamics. I.e. CFD is nice to illustrate behaviours. But never is a proof apart from a real experiment.
That means. The CFD simulations need to be tested against "towing tank" experiments for example. Then you can calibrate the CFD and then the CFD predictions are to some degree meaningfull. I don't see how you could have done a real life test like a towing tank or similar for windsurf boards.
Regarding "that are physical laws". As a physicist with a university degree having discussed the topic with some real experts, i.e. professors, one thing is for sure. The reason why yours and also the the exact opposite approach works is that the effect is neglectable at most minimal. So is just only psychology or even marketing?
Well first of all, in spite of what your professor says, CFD nowadays is ahead of towing tank testing, which is far from the real full size stuff out at sea and as a result, test results are not reliable. Nowadays you can set the sea state, wave heighth and length and period, even various through eachother, like you can have out at sea. The guy who did this CFD research for me in 2015 got a super high grade for his work and he now runs a naval architecture design agency in France with 25 engineers and experts under him, pretty clever guy. And I know quite a few more experts in this field, students on internships and their professors, former interns plus a few of my customers have high positions in marine research institutes. Nowadays, many things are developed even just using CFD including wind turbines and airplanes. Simply as it is more accurate.
As for practice testing, in 2005 I had a few boards with the 4wfs, which allows you to turn the fins within a minute. Within a day testing in clean light wind conditions we figured out that about 2? toe-in was not only turning better, it was also faster.
Then, there are those who have gone from one day using paralel fins to my pre-twisted fins the day after. "Amazing" is what the last one said, I can give you his phone nr if you want.
But is it that hard to understand what happens under a board? When you were a kid, didn?t you jump in puddles and the water would fly everywhere? Now if you would let a board float in a pool and you would land vertically on it? All the same thing, the water wants to escape the pressure we apply on it, just when we are planing, there is a big forward component in the movement but there still is a sidewards component as well. And anyone can imagine that if you are 1m under water the water is not pushed away anymore. When in 2007 I had a board in the test of Boards magazine, I explained their head tester Ian Leonard why a board needs toe-in, he figured out right away that fins would actually needed to be twisted as well. He promised me to keep it to himself.
Then if you are a fan boy of this or that shaper since many years, I can understand that it may be hard to realise you were wrong and for some people this may lead going into denial even if the facts are staring right at them. For sure there is a name in psychology for this phenomenon. From your forum name I figure you are a german from Hamburg? I just had a long time customer from Hamburg in today picking up his new flex tail. And we were chatting about all the fin designs I had over the years and he said the first red and black pre twisted fins in 2010 were big leap forward, these RTM fins were just fragile when hitting bottom.
This was a prototype flex tail with those fins. This one had adjustable flex through airpressure but it was too hard to keep the airchambers sealed. Some ideas are good in theory but it should also be practically doable and durable.
Forgive me bouke, but the bit I struggle with here about your bigger front fins x medium back fin and your flextails etc is this: why has nobody else thought of it? You're so insistent that your way is the best, that everybody who tries it is blown away, so how come word hasn't reached KT's ears? How come braw, Levi etc and all the worlds best sailors haven't tried your concepts and been blown away by them?? I'm not saying you're wrong, because I'm no expert whereas you seem to at least do a good job of sounding like one, but it just seems to me to be the height of arrogance to sit there and say, "I'm right, everybody else is wrong and/or deluded".
Don't waste your time trying to reason here. Bourke used to do exactly the same thing with the now defunct UK forum. He came in regularly on any discussion vaguely related to board construction, "windsurfing theory", pseudo-scientific tests he performed, three-fins indeed ... bad mouthed everybody else in the industry, bullied anybody on the forum who dared to object to his theories.
The worse was that after a while the forum started to divide in two camps, the pro-Bourke and the anti-Bourke, and it frankly became unbearable. I hope this does not happen here because Seabreeze is quite a gem of civility.
I said it before and I say it again: nobody else in the industry shows up in the forum: no big guys, no medium guys, maybe some small business does but just to announce a new board. And so it should, for obvious reasons.
Yeah, another toe in thread!!!!
If I was a low volume board producer and made my own fins I could afford to have 10 different side fins in stock as Bouke-Witchcraft says he does. If I was a larger volume producer and had to make 100's of fins, have my importers and shops around the world stock spares in 10 different sizes then thats a lot of money tied up in stock. Much easier for everyone to have fewer shapes and sizes. There might be a small but noticeable difference in performance of fins with toe-in but for a large volume producer is it worth it?
I believe Ola at Simmer does toe in on their production boards. He also posts (or did previously) on the UK forum.
I own a Simmer Quantum with around 1 degree of toe and the board is fast for a waveboard but still very turny. I've gone to a set of asymmetrical K4 fronts with another degree of toe and speed hasn't suffered one bit plus it grips in turns even better.
Running large (12cm) 2 degree Ezzys on the front of my Quatro is a setup I've used in marginal conditions with a lot of success. Again loads of drive out of turns without taking speed hit. I'd like to try it with some smaller rears to see how surfy it could be. The rear fin boxes are quite far back and I tend to prefer fairly upright fins.
Select to expand quotePhilUK said..
Yeah, another toe in thread!!!!
If I was a low volume board producer and made my own fins I could afford to have 10 different side fins in stock as Bouke-Witchcraft says he does. If I was a larger volume producer and had to make 100's of fins, have my importers and shops around the world stock spares in 10 different sizes then thats a lot of money tied up in stock. Much easier for everyone to have fewer shapes and sizes. There might be a small but noticeable difference in performance of fins with toe-in but for a large volume producer is it worth it?
You could also see this the other way around, with more volume, surely it should be easier to offer a bigger range?
Select to expand quoteGrantmac said..
I believe Ola at Simmer does toe in on their production boards. He also posts (or did previously) on the UK forum.
I own a Simmer Quantum with around 1 degree of toe and the board is fast for a waveboard but still very turny. I've gone to a set of asymmetrical K4 fronts with another degree of toe and speed hasn't suffered one bit plus it grips in turns even better.
Running large (12cm) 2 degree Ezzys on the front of my Quatro is a setup I've used in marginal conditions with a lot of success. Again loads of drive out of turns without taking speed hit. I'd like to try it with some smaller rears to see how surfy it could be. The rear fin boxes are quite far back and I tend to prefer fairly upright fins.
I had loads of discussions with Ola on toe-in and board shapes on the boards.co.uk forum. As far as I know Ola uses 1.8 degree. Which is close to my 2 degrees. I also think to remember that Steve said the asymmetrical K4 fins need minimum 3 degrees. My guess is that asymmetrical K4 fins would still be a bit better with 4 degrees or even a bit more. I have them in my SUPs. I have tried 5 and 6 degrees and that still works fine, better turning and faster in smaller waves, just getting a bit twitchy on bigger waves. People are far too scared of using toe-in. That is probably what I am trying to say here in the first place. And with minituttle fins and a good pair of hands, not that hard to try. Just grind the opposite corners of the fin base so it can turn inside the box, spread some wax in the box and fill the created open corners with resin. If you do not like it, you can simply reverse it. There is no loss of strength. Ideally on a quad you should also do this with the trailing fins but they are usually slot or US box so much harder to impossible to adapt. But starting with the side fins will give an idea of what it does.
I was quoting toe per side that I measured. So probably 1.8 total? Then the Ezzys add another degree total I believe.
I'm running that particular board usually as a thruster. It's great very well powered in onshore conditions.
I think the Quatro I have measured a little toe in the boxes. Could be a measurement error since MT is so small?
Looks like K4 is now offering their symmetrical fins with toe as an option. Might be faster than the fully foiled Ezzy (which are also quite massive).
No, I think it was 1.8 degrees per side but maybe he uses different angles for different shapes. Like surfboard shapers are doing as well, an often seen guide line with surfboards is to have all fins pointing at the nose, so a 5?8" short board has more toe-in than a 8 foot gun. This is a good guide line for windsurf boards as well for asymmetrical fins. There was a thread on the surfing forum Swaylocks saying: "No toe-in? OMG no wonder it has no drive".
In general speed differences between windsurfing and surfing are small. At higher speeds, the sail actually starts to drag unless the wind is side off and is accelerated on the wave face. The main difference is that we need to go upwind as well so the downward fin needs to work the other way around as well and a flat sided fin is not good for that. That is why I give camber rather than making one side flat and K4 does something similar. The bottom line is, it will free up your boards, it will turn better, keeping speed better through the turn (in surfing referred to as "drive"). It will also allow for bigger side fins and a smaller centre fin on trifins and you will get a turny faster board. Even in flat water sailing it will work: Here a board with 4.5 degrees toe in on the pre twisted side fins and a single fin board:
Looks like the symmetricals are offered in 1 degree toe for slotbox only.
Except for a very specific 7cm which they say is for making a Quad very twin-like and basically a personal indulgence for the producer.
Interestingly enough they don't recommend the Ezzy asymmetricals for a tri-fin setup of close to equal sizes. Whereas you are a pretty big fan of them.
No mention of running them on a balanced quad.
Their most recent additions aren't available with toe which is interesting.
Also very interesting is that their production techniques could easily produce twisted fins (much easier than G10) yet they don't offer any.
I'm unsure how much I want to do the heat and twist on a decent set of fins or how accurate I'd be.
Looks like this entire thread was hijacked by stupid thruster toe-in arguments. Bouke, make a board with 5 fin boxes and I'll buy it. lol
