To All I know this is taking a pretty big bite but I’m hoping there will be some opinions how about different foils, & templates and fin combinations affect board performance. In order to be objective I think we should pick 3 different boards to start with and then discuss how we think different fins and set ups will affect how they ride. If you think we can make better choices then these go for it. I know the sky is the limit and tail configuration will play its part as well so we’ll have to agree on a tail for each board and I’m leaving that one open. The choice will not be easy but I think it best to start by submitting these three with the following general specs. Taking one at a time will probably be best so lets pick one to start and it doesn’t have to be any of these. (6’2"x18.5"x2.5") because so many ride small light boards 7’8"x21.0"x2.875") as a good middle of the road hybrid size 9’2"x22.5"x3.0") to include longboards, which I feel it would be a mistake to omit. I realize this is a very basic approach and that it’s nearly impossible to discuss surfboard design so generally and that some will reject this thread as an impossible one. But I want to offer it as food for thought as I’m constantly playing with different fin combinations and find that they can make a huge difference in how a given board performs in different conditions. Thanks to fin boxes we now have this luxury; back in ‘68 you just glassed something on that you though would work and that was that. Good Surfin’, Rich
Here are some of the basic concepts of fin set-ups on mid-length and longer boards, and how they affect performance. Shortboards are for someone else to explain… What I build are a “Thick Base - Fully Foiled Fin”. It is a smooth, loose-feeling fin, that turns tight and releases well. With a fully foiled fin you can use a deeper fin with out the drag you would feel with a conventional fin. The reason is that a foiled fin releases water efficiently and a “flat” fin creates turbulence drag. My personal favorite is: depth 10",rake 10.5",width of base 5",Thickness at base 1.125". It has an 1/8" glass core, laminated to that is 1/2" Baltic birch plywood on both sides, foiled, glassed. The theory behind the “Thick Base - Fully Foiled Fin”…George Greenough had perfected the high-aspect, laminar flow fin, a development, which made him literally the fastest man in the water. The key lay in constructing a fin which could harness the wave’s energy without generating drag-inducing turbulence along the trailing edge of the fin as it moved through the water…Laminar flow basically is over a very narrow range. Water only goes back an inch and a quarter or so before breaking into turbulent flow. So the fin must be narrow. Look at any high-performance fish and you’ll see my fin is basically the same - it’s the same plan and foil shape as a large tuna…you’ll notice their tail is very narrow and quite high. With that kind of fin by the time the turbulence shows up in the water the fin has already left it behind. Hence no turbulence to affect performance. Another great fin is a “Liddle Flex Fin”… Greg Liddle’s theory:“I cannot emphasize enough how important it is to have a flexible fin or fins. The fin allows the board to behave appropriately. To trim at high speed with little effort. To maneuver smoothly and particularly to release during down the line high speed turns. A rigid fin with the inappropriate foil will not make this happen with these boards. The board will pivot awkwardly and die out of a turn with no forward acceleration. It will feel wrong to the initiated.” “It is essential that the fin have this particular type of flex, not a soft bending over flex, but a high tension flex that bends concave and gradually into the base of the fin. It lets power on and off even and smoothly resulting in a high speed and flowing style of surfing.” Another good fin is the “Wingnut Long-Rake” fin made by Rainbow Fin Co. is a fairly deep (10") fin medium stiff with plenty of rake and not too much tip. It’s a good fin for longer, driving turns. I took a stock “Wingnut” and re-foiled it so that it had a lot of tip flex. I like it!!! Smooth sweeping turns and extended trim are more difficult with many of the contemporary multi-fin boards. These boards often have a “stage-y” feel that is more suited to those who prefer “triple-pump” bottom-turns. The tri-fin set-up is only “faster” if it is pumped or rapidly turned from rail to rail. In straight-line trim the tri-fins are just so much drag. Some of the more progressive tri-fins have other design features, such as accelerated rocker, thin volume or narrow planshape that adds more drag, and requires even more energy from the surfer’s to fully use the leverage and projection of the tri-fin design. A “2 + 1”, or a “single fin with training wheels”, is a larger single fin in a center box, supplemented with smaller, Thruster-like side fins set on the rails. The most common set-up is a center fin box holding a 6" to 8" single fin. Side fins are sometimes glassed-on, but FCS plugs are common. The center fin is sometimes placed further up in the box, serving to narrow the “wheelbase” of the combined fins to give the board a looser rail-to-rail feeling. To summarize, the single-fin seems best suited to those who want to trim, glide and perform smooth sweeping turns. A single fin is stable yet pivotal. If you enjoy more energetic surfing, go for a multi-fin, with the “2 + 1” being a reliable compromise. I hope this has been of some help, and that you enjoy experimenting… Paul Jensen
To All>>> I know this is taking a pretty big bite but I’m hoping there will be some > opinions how about different foils, & templates and fin combinations > affect board performance. If I may add a specific question regarding drive on a 2+1 setup- Taking a board like the midlength mentioned above, with fairly flat and wide round pin with slight V between the side fins as a neutral example. As I understand it the side fins provide lift and allow a turn to be initiated more easily than with a single fin. A center fin with a wide base will have more drive, while a cutaway or narrow base will be looser. Now, is it the width of the base of the center fin that has the greatest effect on drive out of turn, of do the side fins influence that as well? (will a board with a narrow center fin lose drive if the side biters are removed?). Wondering if people switching between a single fin and a 2+1 generally use a different center fin for each setup, especially when using a cutaway or similar fin on the 2+1. Hard to test without many fins to play with and no waves. Thanks for any insight.
Here’s an article I wrote a while back and is posted over at www.wetsand.com Surfboard Fins Get No Respect 1/27/01 Surfboard Fins get no respect! When you walk into your favorite surf shop and get all googley eyed over the masterpieces in the racks, it’s not the fins you’re drooling over. Think about it for a minute though. What is a surfboard, but a summation of hydrodynamic surfaces. Just as an airplane generates lift from its wings and control from it’s tail; your board’s bottom generates lift and affects speed. But, it’s your fins working together with rail and bottom contour that most influence the feel of your board when turning. And let’s face it how many short boarders straight-line the waves they ride. Few surfers really understand how fins affect the way their board rides and leave all the specifics to someone else. Rail and bottom contour assist fins in performing their function. But, what really influences the way your board turns is the combination of several important fin factors. No wonder so few surfers pay attention to the “Fin Affect”. It’s f’n complicated! But, today, as the form shape of surfboards goes through finer and finer adjustments, the biggest gains you can make to your board’s performance have to do with your fins. The predominant factors that influence your “Fin Affect” are: 1) Foil Shape- the curvature from leading edge to trailing edge as it changes from base to tip. 2) Template shape- The combination of depth, width, and rake that make up the profile outline of the fin. 3) Placement- which incorporates how far the fins are from the back of the board, how far apart they are from one another, toe and camber. 4) Stability and flex. Let’s discuss each of these and how changing them will affect the way your board performs. Foils are surfaces that affect lift and drag. If you notice an airplane wing has a flat side on the bottom and curved side on the top. The path of least resistance is the bottom side. It takes more effort (drag) to flow around the curved top surface, so more air flows under the wing than over. This creates high pressure under the wing. The air that does flow over the wing separates from the wing at the apex of the leading edge of the wing and creates a low-pressure area. This difference in pressure forms the force (lift) that allows the wing to go up. The more curve a foil has the more drag it induces over the curved surface. Which means that a foil with greater curvature will have more lift at lower speeds. The problem is that at higher speeds that additional drag will develop turbulence and stall the flow across the foil. The exact same scenario occurs under water with side fins. The big difference is that instead of lifting your tail out under water; Side fins orient the curved surface so that they actually pull your boards fin and rail down into the water. This gives you hold when cranking a nasty slash. Consequently, thicker more curvy foils for slow waves and flatter more fine foils for high-speed waves. Template shape has to do with how the fin looks in profile. An over simplification would be deeper, rakier & wider fins provide more control. But, the more profile you have the more fin you drag around. So, you have to optimize the combination of the three so that it is loose enough for your conditions. Yet, tight enough to not get too squirrelly on you. Other factors that figure into requiring more or less of these three variables are: 1) Type of wave: steep and heavy or slopey and fun. 2) Surface conditions: Choppy and irregular or clean and smooth. 3) Rider Size: Big and heavy or small and featherweight. 4) Rider Style: Subtle and flowing or Extreme and radical. Each of the first considerations requires more fin template area and each of the second work better with less. Placement has traditionally been left to convention. Simon Anderson set a benchmark twenty years ago for approximate location. Each shaper has their own personal preference for each of the “models” they make. But, there are subtle differences in most boards and in all riders. Otherwise why would custom boards be in such demand. And remarkably as little as an 1/8" movement fore or aft in either or both the center fin or the side fins can have almost as much effect as going from a rakey 4 ¾" fin to a vertical 4 5/8" fin. If you move your fins closer together they act looser and if you spread them further apart they get tighter. Toe is the amount of angle the base of your side fins are pointed in towards the center of the board relative to the leading edge and trailing edge at the base. Camber is the amount of angle the body of your fin is set at relative to an imaginary horizontal plane perpendicular to your stringer. Both affect the angle of attack that your fin foils experience as they flow through the water. More angle forces more water flow around the outside plane at lower speeds. The net affect is that it becomes easier to initiate turns on slower waves. To much angle at higher speeds increases turbulence and drag. Finally, stability and flex are crucial to making this all click. If you have a deeper fin you can get away with more tip-flex and not wash out. The benefit of tip flex is that it dampens or smoothes out some of the bite in direction changes. The down side of tip flex is that if you get too much tip flex it will wash out. Base stability is crucial to a good set of fins. If a fin moves around at the base it will set up turbulence. Turbulence generates drag and disturbs the lift, which keeps you fins holding. So it is slow and out of control. If you like a more pivoty board you would do well to try a stiffer set of smaller more vertical fins. Prior to eight years ago the only options a surfer had to muck with all these variables was to grind his glass-on fins off and install a slightly different set in a slightly different location and record the differences until they found the optimum. Not very likely. So, with the exception of a few elite pro’s, we all lived with what we were given. Now with the advent of removable fins (i.e. FCS, Future, Lock Box, OAM and O’Fish’l) you can at least muck with the first two “Fin affect factors”. But, if you want the ability to dial in your board with all four factors you have got to try the newest competitor to the fin system market Red X /Excel. Tom O’Keefe
guys…i can’t say enough how much i appreciate the responses. very insightful and it’s clear that you have given this much think time(to my(our)) benefit. i just found this url, so, i will be reading more. Q:i cannot figure out why some would want to have added foil to a fin? it figures that one could add control/stability by fin placement and size, yet keep the foil down(thinner). maybe there are too many variables for me;-) thanks! rod>>> Here’s an article I wrote a while back and is posted over at > www.wetsand.com>>> Surfboard Fins Get No Respect 1/27/01>>> Surfboard Fins get no respect!>>> When you walk into your favorite surf shop and get all googley eyed over > the masterpieces in the racks, it’s not the fins you’re drooling over. > Think about it for a minute though. What is a surfboard, but a summation > of hydrodynamic surfaces. Just as an airplane generates lift from its > wings and control from it’s tail; your board’s bottom generates lift and > affects speed. But, it’s your fins working together with rail and bottom > contour that most influence the feel of your board when turning. And let’s > face it how many short boarders straight-line the waves they ride.>>> Few surfers really understand how fins affect the way their board rides > and leave all the specifics to someone else. Rail and bottom contour > assist fins in performing their function. But, what really influences the > way your board turns is the combination of several important fin factors. > No wonder so few surfers pay attention to the “Fin Affect”. It’s > f’n complicated!>>> But, today, as the form shape of surfboards goes through finer and finer > adjustments, the biggest gains you can make to your board’s performance > have to do with your fins. The predominant factors that influence your > “Fin Affect” are:>>> 1) Foil Shape- the curvature from leading edge to trailing edge as it > changes from base to tip.>>> 2) Template shape- The combination of depth, width, and rake that make up > the profile outline of the fin.>>> 3) Placement- which incorporates how far the fins are from the back of the > board, how far apart they are from one another, toe and camber.>>> 4) Stability and flex.>>> Let’s discuss each of these and how changing them will affect the way your > board performs.>>> Foils are surfaces that affect lift and drag. If you notice an airplane > wing has a flat side on the bottom and curved side on the top. The path of > least resistance is the bottom side. It takes more effort (drag) to flow > around the curved top surface, so more air flows under the wing than over. > This creates high pressure under the wing. The air that does flow over the > wing separates from the wing at the apex of the leading edge of the wing > and creates a low-pressure area. This difference in pressure forms the > force (lift) that allows the wing to go up. The more curve a foil has the > more drag it induces over the curved surface. Which means that a foil with > greater curvature will have more lift at lower speeds. The problem is that > at higher speeds that additional drag will develop turbulence and stall > the flow across the foil. The exact same scenario occurs under water with > side fins. The big difference is that instead of lifting your tail out > under water; Side fins orient the curved surface so that they actually > pull your boards fin and rail down into the water. This gives you hold > when cranking a nasty slash. Consequently, thicker more curvy foils for > slow waves and flatter more fine foils for high-speed waves.>>> Template shape has to do with how the fin looks in profile. An over > simplification would be deeper, rakier & wider fins provide more > control. But, the more profile you have the more fin you drag around. So, > you have to optimize the combination of the three so that it is loose > enough for your conditions. Yet, tight enough to not get too squirrelly on > you. Other factors that figure into requiring more or less of these three > variables are:>>> 1) Type of wave: steep and heavy or slopey and fun.>>> 2) Surface conditions: Choppy and irregular or clean and smooth.>>> 3) Rider Size: Big and heavy or small and featherweight.>>> 4) Rider Style: Subtle and flowing or Extreme and radical.>>> Each of the first considerations requires more fin template area and each > of the second work better with less.>>> Placement has traditionally been left to convention. Simon Anderson set a > benchmark twenty years ago for approximate location. Each shaper has their > own personal preference for each of the “models” they make. But, > there are subtle differences in most boards and in all riders. Otherwise > why would custom boards be in such demand.>>> And remarkably as little as an 1/8" movement fore or aft in either or > both the center fin or the side fins can have almost as much effect as > going from a rakey 4 ¾" fin to a vertical 4 5/8" fin. If you > move your fins closer together they act looser and if you spread them > further apart they get tighter.>>> Toe is the amount of angle the base of your side fins are pointed in > towards the center of the board relative to the leading edge and trailing > edge at the base. Camber is the amount of angle the body of your fin is > set at relative to an imaginary horizontal plane perpendicular to your > stringer. Both affect the angle of attack that your fin foils experience > as they flow through the water. More angle forces more water flow around > the outside plane at lower speeds. The net affect is that it becomes > easier to initiate turns on slower waves. To much angle at higher speeds > increases turbulence and drag.>>> Finally, stability and flex are crucial to making this all click. If you > have a deeper fin you can get away with more tip-flex and not wash out. > The benefit of tip flex is that it dampens or smoothes out some of the > bite in direction changes. The down side of tip flex is that if you get > too much tip flex it will wash out. Base stability is crucial to a good > set of fins. If a fin moves around at the base it will set up turbulence. > Turbulence generates drag and disturbs the lift, which keeps you fins > holding. So it is slow and out of control. If you like a more pivoty board > you would do well to try a stiffer set of smaller more vertical fins.>>> Prior to eight years ago the only options a surfer had to muck with all > these variables was to grind his glass-on fins off and install a slightly > different set in a slightly different location and record the differences > until they found the optimum. Not very likely. So, with the exception of a > few elite pro’s, we all lived with what we were given. Now with the advent > of removable fins (i.e. FCS, Future, Lock Box, OAM and O’Fish’l) you can > at least muck with the first two “Fin affect factors”. But, if > you want the ability to dial in your board with all four factors you have > got to try the newest competitor to the fin system market Red X /Excel.>>> Tom O’Keefe
guys…i can’t say enough how much i appreciate the responses. very > insightful and it’s clear that you have given this much think time(to > my(our)) benefit. i just found this url, so, i will be reading more.>>> Q:i cannot figure out why some would want to have added foil to a fin? it > figures that one could add control/stability by fin placement and size, > yet keep the foil down(thinner). maybe there are too many variables for > me;-) thanks! rod Think of foils as wings. High Speed Jet Air Craft have very fine shallow foils because the velocity of the air flowing across the wing exagerates the lift component (i.e. minimize drag and still gain lift). Then think of a crop duster with very full foils. They produce lots of drag to produce lift. But, they are not expected to deal with alot of speed.
Hello, I need some advice. I’m doing a science project on the shape of surfboard fins in relation to the drag generated. I need to choose on variable to change in the design of the fins (Rake, Hieght, Base length, Thickness, ect.), but this variable needs to affect the drag of the board so that I can get results. So what so you guys think I should do, what single variable greatest affects the drag of the board?
Hello, I need some advice. I’m doing a science project on the shape of surfboard fins in relation to the drag generated. I need to choose on variable to change in the design of the fins (Rake, Hieght, Base length, Thickness, ect.), but this variable needs to affect the drag of the board so that I can get results. So what so you guys think I should do, what single variable greatest affects the drag of the board?
I would guess fin height.
There are some classic threads here on Sways.
Thickness.
I’m no expert but I do have one board that absolutely sucked with the same FCS fins I’ve used for ages. I’d almost given up on the board. I bought a set of fins that were bigger and with less flex and the board was instantly transformed into a great board. There are just too many variables. Size, template, flex, toe, cant, rail shape, board outline and bottom contours all have to align like stars in the sky to make a good board.
A few fin threads I dug up recently:
http://www.swaylocks.com/forums/fin-theory
http://www.swaylocks.com/groups/more-fin-theory
you’ve got your hands full with this subject. please don’t start any arguments. and good luck.
Drag increases as a function of velocity squared.
What is the anticipated velocity range of your board? Speed affects drag differently for different shapes.
The board we would probable attatch the fins to is a 9 foot long board with very little rocker.
After noticing a thread on the above topic here’s my take on it. But firstly , I’m not wanting to stir the pot here. Depending on HOW any ond each of us rides a surfboard, I believe, is a major factor in how we consistently perform out there in the water - regardless. But all this is subjective opinion. Never the less, as far as fin configuration and board design has affected me - here’s what I’ve noticed after making and riding boards with just about all the fin configuration anyone could. To some degree this is and was a futile exercise of course because as I’d hope we would all agree, it is the overall total design of the board that might affect it’s performance and handling - the operative word here as far as I have found it being - might. Recently I watched a YouTube video which demonstrated 3 Bing board models varying greatly, the first being a , yes - 3’11" " converted " boogie board. Bottom line what I noticed was that the three of them when it really came down to it, all performed very similarly in every way. But even here , these boards were all ridden in very similar wave conditions - small to medium height. So therefor the first very determining factor on this issue might well be that board " performance " is very really tested in the very different environments of small to medium size wave height and power as opposed to BIG. Literally, it may well be that that is the cruncher here.
Secondly I’ve very often asked myself is it really my board that " goes faster or slower " - or is it the power of the wave coupled with the wave positions I place myself in that is in control here ?
Thirdly, simply compare the greatly differing surfer performance styles of for example Kelly Slater, Mick Fanning as opposed to the other “school” - Ellis Erickson, Alex Knott etc. Very different " floats for boats " here.
In the end for me being of the latter after having surfed twin fins, tri fins and quads, I now gleefully ride a single fin and most definitely always will. Whether it’s 2’ waves or 6’ my single fin goes just great every time.
I now believe it’s best just to have one good board that really suits me as opposed to a quiver for varying surf conditions. " Less is more " as the saying goes. But for each and every one of us - it all depends.