OK it’s been 20 days, What is the unlocked mystery?
So many angles, so many variables! When you work with fin angle you increase drive with less angle, however you have to also take fin cant into consideration. A balance between the two can make or break a board. I have used approx. 1/8" tow in on many boards and adjusted the cant for snappy little fishes or the longer mini guns (up to 7’) Fin placement is also a huge factor. If the fins are set farther apart (front fins to rear fin) they tend to draw turns out farther than if they are close together as in the “MR” supa twin.
Rocker, curve in the tail outline, tail width, will all have direct effect on how everything flows together.
I look forward to BB’s post to this “mystery”
Sorry guys
I am really swamped and haven’t had time for a long sit down fin discussion.
Soon I will get a break and we can banter fin ideas around.
Ok then, why not set all three fins straight no toe, no cant. then use rocker in the board to turn? Fins create drag right? rocker is the major magic thing that loosens up boards right? Work more on rail design and rocker? Toe and cant if you want to slow a board down, which might not be a bad thing sometimes?
-Enquiring minds
Aloha Ron
Glad to hear all is well with you and that you have enjoyed your boards all these years!
To explain my fin positions, I first need to define my underlying surfboard design philosophy. I don’t expect any of this to be a revelation to anyone, I just need to lay some ground work even if it is common knowledge, so that my fin angles make sense.
Firstly, we have to begin with an issue that on Swaylock’s is often confused, misunderstood or ignored. There is a huge difference between making surfboards for a living and making them for a hobby. It is not about the quality of the work or how much money changes hands but rather how much that money effects the survival of the surfboard maker.
Things that are relevant to commercial surfboard makers simply aren’t as relevant to the hobbyist. This is not a “we” are better than “you” issue from either side. It is just a recognition that there are issues that are more important to each builder, depending on what kinds of needs he is trying to fill. And when you are trying to support a family on the income from building surfboards things will often be excruciatingly relevant. While these same things simply won’t be that important to the hobbyist.
For example, making surfboards commercially requires fairly high volumes. To sustain these volumes the commercial builder needs to have a high customer return rate and also a steady flow of new customers. To achieve this, requires a high degree of consistency. And this consistency must cover all aspects of the business. Accessibility, delivery, quality, price, financial stability, performance and image, are just a few of the factors that must all be consistently controlled so as to deliver, to the customer, a predictable value for their investment. The higher the price the more consistent the perceived value of the product has to be.
So…most everything I do in surfboard design and building is focused on creating consistency. The whole goal of my development of MCS (Measurement Controlled Shaping) was for the purpose of guaranteeing consistent shaping outcomes.
We all recognize the immense amount of variables that make up a good surfboard design and how difficult it can be to not only figure out what they are, but then actually arrive at them the way you expected in the finished product. My fins and placements fit right into this. There are some things in making surfboards that are easier to control than other things. Fins are one of those things. Because of this, I have been able to create a kind of controlled yet auto adjusting fin placement that is highly adaptable to a broad range of boards and use.
Here are some of my observations and how they apply to the system I use.
Toe In facilitates turning, like sticking your hand out the window of a moving car. When the board is on the rail, the inner fin Toe In is pointing up. This causes the tail, like your hand, to lift upwards in the direction of the angle of the toe in.
Toe In, combined with a narrow nose and a wide point behind center, assists this by creating a distinct fulcrum point around which the board will tilt and turn as the inner side fin lifts the tail up and outward which drives the nose in a rotation in the opposite direction. The more Toe In the more this action is activated, assuming there are other complimentary features built into the boards design.
The asymmetrical foil of the side fins generates a downward lifting force in the opposite direction of the Toe In’s lift. This tempers and controls the radical lifting force generated by the Toe In angle of the fin. While the Toe In lift, rotates the board around the wide point fulcrum, the asymmetrical foil helps to keep the fin imbedded into the water stream exiting across and out the back of the board.
Because of these issues above, I found it necessary to develop a system for arriving at Toe In angles that took these issues into consideration in an automated and consistent way. That way, I would be free to concentrate on other less predictable areas of board design and shaping.
Rob, your 3 guesses are actually all correct. I only slightly alter fin positions and angles and generally do so in a progressively predictable way as it relates to the board, the way the rider surfs and the waves he will most be surfing.
The longer the board, the less toe in angle, even if the fins are still pointed to the nose. Jimithesaint, was right with his analysis on this point. Glad I could help with your outline cutting technique.
Faster, more lined up (as Greg mentioned) and bigger waves requiring longer turns and high speed trims tend to desire more parallel side fin positions. Additionally, these kinds of waves all tend to require longer, narrower tailed boards. Longer boards (not longboards) usually get progressively narrower tails as they get longer. Therefore, toe in, becomes more parallel to the other side fin and stringer as tails get narrower.
Like establishing the center of the board as the point from which to consistently reference rockers from, I use the nose of the board simply as the reference point for fin toe in. I never measure the distance between the leading edge and the trailing edge to establish toe in angles, which is often common in the industry.
In making Quivers of boards for the same customer, like Rob in New York, I am trying to create a consistent and predictable segue between boards that isn’t upsetting to the rider. Depending on other factors, I often keep the toe in very similar between boards so that the lifting forces energizing the turn are similar and I let the auto adjusting factors mentioned above temper it as it should. In other words, another surfer of different size and style that surfed elsewhere might get fins from me that were all pointed 1” off the nose rather than at the nose like Robs were. The nose is an absolute point of reference only. Not all fins point there on all boards.
Kitesurfer’s comments were interesting. A kite board functions at much higher speeds but also wants to slip sideways and having the fins too big and parallel puts the angle of attack all wrong as the water is moving more crosswise to the board than one might expect requiring more toe in to get the AOA right. The toe in on a surfboard has more to do with turning than what it does on a Kite Board where the fins also function like a sailboat keel to prevent sideways drift. The curvy template on your Kite board might require more Toe In than a kite board with a more parallel template.
And yes, I don’t always point them to the nose. I regularly vary them for specific conditions. I measure this by “inches + or -” from the nose. + is over the nose. – is before the nose. I changed the fins on many boards, many, many times so that I could determine the real effects of fin placement and not get it confused with subtle changes in the hull design. There is no other way to do this then changing the fins on exactly the same boards. Remember, this was at a time when there was no established norm or standard for where multiple fins should really go on surfboards especially ones built for Hawaiian conditions. I even tested existing single fins by cutting off the single fin and turning them into trifins. I learned a lot as it was a very creative time and there was great rider feed back and of course my own surfing to confirm it.
Haavard, your calculations were great. But to be accurate you need to calculate a reciprocal drop in tail width, as boards get longer. Say about 1/16” narrower tail, per inch of board length or about 1/32” movement toward the stringer per fin beginning at about 6’8” or so. You also need to calculate for the fins moving up about a 1/8” for every 2” of board length. Now try those calculations again.
You wondered about keeping the angle accurate when installing the fins. To keep the angle accurate you draw a line on the foam and set the inner flat edge of the fin exactly along the edge of it. This works regardless of the fin attachment method and allows you to see that the fin is placed properly.
Meecrafty, I don’t understand your Planer/Photo question. If rocker is the issue, and I agree it is a major foundational one, why do you feel that showing a shaper with a planer throws anyone off the scent. Isn’t rocker shaped in with the planer? At least that is how I shape it into the board. I never use the sanding block or hand plane to create rocker, I only use them to clean up the planers tracks. I can assure you that there isn’t some kind of media conspiracy that is trying to throw anyone “off the scent”. Just maybe, a picture of a shaper holding a wimpy sanding block doesn’t communicate a macho enough image! Ha!
You need to ease up a bit Meecrafty, there may be no mysteries left for you to figure out anymore, but that doesn’t mean others like Rob aren’t excited about their new discoveries and the associated reasons for their existence. Just because something seems to be a long time standard to you, doesn’t mean the reason for its existence is understood by everyone. Consider this, if consistently making good surfboards WASN”T still a mystery to most board builders, there wouldn’t be such things as MAGIC boards now would there! Lastly, I don’t know how “standard” my “to nose” refference system actually is. Many shapers I know still measure the difference between trailing edge and leading edge to establish their toe in and that is fine. Heck some shapers still measure board lengths along the deck rather than the bottom which produces 2 different lengths.
More soon
wow !
Thanks for that Bill !
Now , Q.2 …
how do you arrive at what degree ‘cant’ you will have your fins at , assuming a lot of your boards have glass on fins ?
For example, do you vary the cant with the length of the board increasing also ?
cheers !
ben
Aloha Ben
Good question Ben but I didn’t even finish the first question and responding to everyone’s comments….
Oh well, here goes about Cant or Tilt.
Yes, I vary the cant on all my boards relative to the bottom design, riders abilities, and waves the board will be used in. But I don’t use an auto adjusting formula as I haven’t stumbled on to one that is easy to use and gets it right for 90% of boards.
Multi fin boards have many advantages that single fins don’t. One of the most significant is the hydroplaning effect created by the outward tilting of the side fins. This hydrodynamic lift can be huge, like a fire hose blasting up on the bottom of the board in between the fins. Creating a kind of ball bearing, swively, looseness and maneuverability, that when directed out the back of the board generates great thrust.
Consider a surfboard with a flat bottom. Traveling at 10 mph, the amount of wetted surface, that is needed to plane or lift 175 pounds might be (I am guessing for the sake of discussion) say 4 square feet. More wetted surface will generate more lift, but there is a downside to it.
Due to surface friction with the water the wetted surface creates resistance or drag. Hence the use of the term “wetted” surface. The dry surface has little effect by comparison so we won’t discuss it here. Consuming all the energy generated by the 10 mph of thrust, toward only lifting the 175 pounds, is necessary to create a minimal surfing experience. But using more of it for scooting the board ahead faster would be much better. But most of the energy is used just to lift the 175 lbs rather than move the board ahead. Finding a way to fix this is our goal. Assuming the wave stays the same and the riders weight stays the same, we have a big challenge on our hands!
If we could reduce the wetted surface, it would reduce drag and increase speed and speed would increase lift. And this would free up energy to scoot the board forward. But if we reduced the wetted surface, it wouldn’t support the 175 lbs at 10 mph and we would somehow have to increase the speed to support the same 175 pounds or the board would bog down. Since our sample weight is a static amount we can’t change it. And using a common, smallish, mushy wave as our sample standard is typical of common waves around the world that don’t have much extra energy or speed to impart to our formula. Still the sample wave we are riding may have more energy hiding somewhere such that we could go faster than 10 mph, but the drag and lack of liveliness from the required wetted surface is holding us back from finding it.
If we could increase the lifting force of the wetted surface we might be able to make the wetted surface smaller, reducing drag and increasing speed, which would increase lift and then we could further decrease the wetted surface, etc, etc. As you can see, exponential returns are available from this
Most waves don’t allow for extended straight trims. Nor do most surfers think that is particularly fulfilling. So surfboards are intended to turn, not just trim along straight. Because of this, rocker was introduced into the flat shape of the wetted surface to assist in turning and the board fitting into the curved shape of the wave. Rocker releases some of the water pressure building up under the board, that causes the lift we need. Rocker then, reduces lift and in so doing, increases drag. Normally this would cause a necessary increase in wetted surface to compensate for the loss of lift and planning speed. But since rocker increases maneuverability, the surfboard can now be placed in places on the wave where there is more energy. This extra energy can offset the drag caused by the increase in rocker as long as the surfer is good enough to take advantage of it by putting the board in more powerful positions on the wave. Of course, these positions are more critical so he must be good enough to handle it. There is no gain in planning speed or lift if you are just getting pitched over the falls! Ha!
We have now seen that gaining more lift from more wetted surface area, doesn’t really work as it causes more drag. So there has to be a better solution. Getting more lift by shaping the wetted surface into a more efficient absorber of energy is one solution. That is why most surfboards today incorporate some kind of Concave in the bottom. The concave traps the water and forces it to release rearward, were it will do the most good in maintaining lift and generating speed. This works great but took a long time for surfers to be able to handle these highly rockered, heavily concaved boards. Their superior lift and maneuverability allowed the wetted surface to be lessened by making the boards narrower. This made them faster and more maneuverable which in turn allowed them to be made even thinner and more narrower. Eventually, this process led to boards that were too eccentric for the average surfer in average waves and we are thankfully, seeing a retreat from super thin and narrow boards being sold to average surfers in average waves.
Another way to increase lift and decrease wetted surface is through the fins. On single fin boards the fins add very little lift that can be translated into a reduction in wetted surface. The same is true of most any amount of fins if they are mounted vertically or square to the bottom but when the side fins on a tri fin are tilted or canted outward from vertical, varying amounts of lift can be generated from the fins, depending on their cant, foil and size. Canting them out from vertical turns the side fins into hydrofoils or lifting wings. This is highly advantages as lifting wings generate exceptional lift with very little increase in drag. The more they are canted out, the more wing like they become and the more lift they can generate. The only problem is, is that when you turn the board on the rail and need some kind of keel effect (fin area) to prevent the board from slipping sideways, the heavily canted fin won’t be straight up enough in the water to effectively resist the forces trying to push it sideways through the water. Angles of attack, foils and fin shape can effect this but having too little surface area will not create enough lateral resistance to prevent the board from drifting sideways.
So a lot of cant or tilt is good for generating lift and making the board faster in trim positions. Another advantage of a lot of tilt is that the outer fin will release earlier and easier, allowing the board to be rolled up onto the rail more easily. But too much tilt on the side fins won’t allow them to hold well under hard turning situations causing the board to spin out or drift and loose forward thrust. A good holding board needs to provide enough return force to match our outward turning force on the tail to have it not slip sideways and waste this energy. It needs to force that energy into being released out through the back of the board causing forward “thrust”, hence the name THRUSTER…!
If we look at the same 175 pound rider going 10 mph we can generate about (guessing here) 25% more lift by canting the fins out to their maximum and we can do this without increasing the wetted surface or increasing drag allowing us to make overall narrower boards that have less wetted surface and drag. But realistically, the maximum tilt for lift and speed in trim, won’t allow us a secure lateral resistance and hold during hard turns, so the amount of lift we can get and still have good holding is probably more like 15%-20%. Other factors like bottom shape, rail thickness and hardness and rocker all effect the bite of the board in the water and its holding power or lateral resistance to side slipping. Combining all these things together properly will allow us to gain the maximum lift and thrust with minimal loss in holding power.
GENERALLY speaking….On a flat bottom board, the amount of fin tilt or cant is ideal around 5-6 degrees. And depending on the amount of Vee Bottom or Concave, this number would be adjusted a couple of degrees in either direction. And depending on the surfer and his abilities and needs, these numbers would also be adjusted. For example, a semi gun for larger waves that are not steep and are softer breaking might allow more cant in the fins, while a hollow powerful wave could use less cant. On the other hand, the size of the surfer and how hard he can push on the board could throw the numbers off a couple of degrees.
It is very important to remember that good surfboards…. dare I say Magic ones…. Are a very delicate combination of specific blends and compromises that all total up to a singular, exceptional, performance level, that exceeds the expectations or abilities of the surfer such that the board always blows his mind or at least meets or beats his expectations. Knowing how to combine and blend a near infinite amount of unique features into combinations that consistently perform above the customer’s expectations is what makes some surfboard makers better than others.
great stuff bill
thanks so much
you make it sound sensible mate
that one should go in the resources i reckon
can’t wait for the one on toe-in…
wow again Bill !
[ I concur with Silly !! …this stuff belongs in the resources …under ‘fins’ or ‘cant’ , or ‘toe-in’ .]
Related to the above mentioned toe and cant of fins , I’m just interested to hear your take on 3 and 5 fin bonzers in bigger hollow surf …have you ridden [m]any , and what were your thoughts on the “feeling” [fins , thrust , holding power… or otherwise] through turns ?
… thanks !
ben
[I hope this isn’t ‘out of line’ with your train of thought ]
This was a 7’6" five fin bonzer.
I don’t like bonzers on big waves. I have tried a fair number of boards in conditions like these, and still find a thick reverse vee thruster with glassed on fins and reduced chord length rail fins (with normal toe-in) is by far my most comfortable set-up. By far the most egregious problem for me is inadequate rocker (far too common still), but having a rail fin with 4 degrees cant or less is still pretty important to keep that rail fin hold. Plus, on waves like these, I tend to push really hard on my front foot on the drop and hope for the best, and bonzers tend not to like that riding style…if I make the drop with the bonzer I need to shift my weight all the way back to turn, on a thruster it is a lot less work for me.
Quote:
that wave
u got big gonads blakestah
im impressed
id have a chocky in my wettie
Wow Dad! (yes, it’s Rozi and I joined swaylocks just to give you this message.) I’ve never realized, after all these years of watching you from the stool in your shaping room, what making boards took. It was just something you did and were good at. After reading your explanation of the “mystery”, I’m convinced you’re a genius.
[=Blue]Roslyn, you Crazy daughter… now your embarassing me! But thanks for the love.
I miss you
Love Dad
You are a lucky man.
wow bill that was extremely informative and put into understandable terms! it’s one thing to know something, but it’s another to try and explain it! mahalo
[=Blue]Aloha 96731
Thank you! And welcome to Swaylocks… pretty cool isn’t it!
Hi Bill,
Life’s always playing tricks, ha!
Thanks again for sharing your experience with us.
Aloha Jeff
Howz it going down in Brasil?
My daughter is heading your way this month. Her friend is down there heading up marketing for Nike and she is going to hang out with him for awhile
Quote:
Aloha Ben
Good question Ben but I didn’t even finish the first question and responding to everyone’s comments….
Oh well, here goes about Cant or Tilt.
Yes, I vary the cant on all my boards relative to the bottom design, riders abilities, and waves the board will be used in. But I don’t use an auto adjusting formula as I haven’t stumbled on to one that is easy to use and gets it right for 90% of boards.
Multi fin boards have many advantages that single fins don’t. One of the most significant is the hydroplaning effect created by the outward tilting of the side fins. This hydrodynamic lift can be huge, like a fire hose blasting up on the bottom of the board in between the fins. Creating a kind of ball bearing, swively, looseness and maneuverability, that when directed out the back of the board generates great thrust.
Consider a surfboard with a flat bottom. Traveling at 10 mph, the amount of wetted surface, that is needed to plane or lift 175 pounds might be (I am guessing for the sake of discussion) say 4 square feet. More wetted surface will generate more lift, but there is a downside to it.
Due to surface friction with the water the wetted surface creates resistance or drag. Hence the use of the term “wetted” surface. The dry surface has little effect by comparison so we won’t discuss it here. Consuming all the energy generated by the 10 mph of thrust, toward only lifting the 175 pounds, is necessary to create a minimal surfing experience. But using more of it for scooting the board ahead faster would be much better. But most of the energy is used just to lift the 175 lbs rather than move the board ahead. Finding a way to fix this is our goal. Assuming the wave stays the same and the riders weight stays the same, we have a big challenge on our hands!
If we could reduce the wetted surface, it would reduce drag and increase speed and speed would increase lift. And this would free up energy to scoot the board forward. But if we reduced the wetted surface, it wouldn’t support the 175 lbs at 10 mph and we would somehow have to increase the speed to support the same 175 pounds or the board would bog down. Since our sample weight is a static amount we can’t change it. And using a common, smallish, mushy wave as our sample standard is typical of common waves around the world that don’t have much extra energy or speed to impart to our formula. Still the sample wave we are riding may have more energy hiding somewhere such that we could go faster than 10 mph, but the drag and lack of liveliness from the required wetted surface is holding us back from finding it.
If we could increase the lifting force of the wetted surface we might be able to make the wetted surface smaller, reducing drag and increasing speed, which would increase lift and then we could further decrease the wetted surface, etc, etc. As you can see, exponential returns are available from this
Most waves don’t allow for extended straight trims. Nor do most surfers think that is particularly fulfilling. So surfboards are intended to turn, not just trim along straight. Because of this, rocker was introduced into the flat shape of the wetted surface to assist in turning and the board fitting into the curved shape of the wave. Rocker releases some of the water pressure building up under the board, that causes the lift we need. Rocker then, reduces lift and in so doing, increases drag. Normally this would cause a necessary increase in wetted surface to compensate for the loss of lift and planning speed. But since rocker increases maneuverability, the surfboard can now be placed in places on the wave where there is more energy. This extra energy can offset the drag caused by the increase in rocker as long as the surfer is good enough to take advantage of it by putting the board in more powerful positions on the wave. Of course, these positions are more critical so he must be good enough to handle it. There is no gain in planning speed or lift if you are just getting pitched over the falls! Ha!
We have now seen that gaining more lift from more wetted surface area, doesn’t really work as it causes more drag. So there has to be a better solution. Getting more lift by shaping the wetted surface into a more efficient absorber of energy is one solution. That is why most surfboards today incorporate some kind of Concave in the bottom. The concave traps the water and forces it to release rearward, were it will do the most good in maintaining lift and generating speed. This works great but took a long time for surfers to be able to handle these highly rockered, heavily concaved boards. Their superior lift and maneuverability allowed the wetted surface to be lessened by making the boards narrower. This made them faster and more maneuverable which in turn allowed them to be made even thinner and more narrower. Eventually, this process led to boards that were too eccentric for the average surfer in average waves and we are thankfully, seeing a retreat from super thin and narrow boards being sold to average surfers in average waves.
Another way to increase lift and decrease wetted surface is through the fins. On single fin boards the fins add very little lift that can be translated into a reduction in wetted surface. The same is true of most any amount of fins if they are mounted vertically or square to the bottom but when the side fins on a tri fin are tilted or canted outward from vertical, varying amounts of lift can be generated from the fins, depending on their cant, foil and size. Canting them out from vertical turns the side fins into hydrofoils or lifting wings. This is highly advantages as lifting wings generate exceptional lift with very little increase in drag. The more they are canted out, the more wing like they become and the more lift they can generate. The only problem is, is that when you turn the board on the rail and need some kind of keel effect (fin area) to prevent the board from slipping sideways, the heavily canted fin won’t be straight up enough in the water to effectively resist the forces trying to push it sideways through the water. Angles of attack, foils and fin shape can effect this but having too little surface area will not create enough lateral resistance to prevent the board from drifting sideways.
So a lot of cant or tilt is good for generating lift and making the board faster in trim positions. Another advantage of a lot of tilt is that the outer fin will release earlier and easier, allowing the board to be rolled up onto the rail more easily. But too much tilt on the side fins won’t allow them to hold well under hard turning situations causing the board to spin out or drift and loose forward thrust. A good holding board needs to provide enough return force to match our outward turning force on the tail to have it not slip sideways and waste this energy. It needs to force that energy into being released out through the back of the board causing forward “thrust”, hence the name THRUSTER…!
If we look at the same 175 pound rider going 10 mph we can generate about (guessing here) 25% more lift by canting the fins out to their maximum and we can do this without increasing the wetted surface or increasing drag allowing us to make overall narrower boards that have less wetted surface and drag. But realistically, the maximum tilt for lift and speed in trim, won’t allow us a secure lateral resistance and hold during hard turns, so the amount of lift we can get and still have good holding is probably more like 15%-20%. Other factors like bottom shape, rail thickness and hardness and rocker all effect the bite of the board in the water and its holding power or lateral resistance to side slipping. Combining all these things together properly will allow us to gain the maximum lift and thrust with minimal loss in holding power.
GENERALLY speaking….On a flat bottom board, the amount of fin tilt or cant is ideal around 5-6 degrees. And depending on the amount of Vee Bottom or Concave, this number would be adjusted a couple of degrees in either direction. And depending on the surfer and his abilities and needs, these numbers would also be adjusted. For example, a semi gun for larger waves that are not steep and are softer breaking might allow more cant in the fins, while a hollow powerful wave could use less cant. On the other hand, the size of the surfer and how hard he can push on the board could throw the numbers off a couple of degrees.
It is very important to remember that good surfboards…. dare I say Magic ones…. Are a very delicate combination of specific blends and compromises that all total up to a singular, exceptional, performance level, that exceeds the expectations or abilities of the surfer such that the board always blows his mind or at least meets or beats his expectations. Knowing how to combine and blend a near infinite amount of unique features into combinations that consistently perform above the customer’s expectations is what makes some surfboard makers better than others.
Bill,
I know your mostly a fan of concaves, but most everything I surf and sell are domed bottoms. What type of fin cant do you suggest on these types of bottoms. I do sell some concaves, just not the majority.
Thanks in advance.