Hey,
I see all the fancy fin talk happening, but I have a few basic basic questions. In standard surfing terms… on a head high wave, how does the placement, toe-in and cant of the side fins affect performance?
Thanks!
Randy
Hi Randy,
i have experienced the effects of these movements. Simply put, toe-in & out affects the water flow & speed (straighter the fin the faster the board), splay/cant affects the sensitivity of the board from rail to rail (more splay more sensitive & easier to turn), and moving the front fins up & down will make the board hold more or less off the bottom & top turns whilst moving the centre fin up increases the boards responsiveness.
regards
surfrat
Okay I’m going to take stab at this but more in hopes of receiving reassurance or correction from a pro.
Cant – More will provide lift, getting you on plane faster, and help with the angle of attack when turning. Its downside would be instability at higher speeds.
Toe - Will provide a tighter turning arc, and help provide more lift. Downside again would be instability at higher speeds, in addition to drag, and tracking problems.
Alligment: Forward will loosen the board - back will stabilize and settle.
Best,
HerbB
Rail fin cant. more cant is more lift in turns, and less drive. Less cant is more drive and less lift. Impacts on planing and paddling are quite small.
toe-in. A very sensitive parameter. More toe is more drag going straight, and smaller radius through turns, and more drive through turns. Generic toe is 1/4" on a 4.5 inch base, this is about 3 degrees. Almost all boards fall between 2 and 5 degrees of toe in (except a few fish toed across the nose which may hit 6 degrees).
Placement. The fore-aft span of the rail and tail fin translates to hold in turns. You have two points, each providing hold, in a line. The further apart they are, the more stable the board will turn. It will also slow the turns down somewhat. If you move the whole cluster forward, the board loosens, if you move the whole cluster back, the board stiffens in turning.
Okay, seems to make sense…
Except, I’ve heard that many pros (long and shortboards) prefer their fin cluster further back than what you’d find on an everyday surfer’s board. Wouldn’t this stiffen things up? Or, have I simply heard somebody’s mistaken theory?
As far as toe-in, I’m measuring two points… the leading edge of the fin is 1/4 to 1/8 of an inch closer to the stringer than the trailing edge… Is this correct?
Now, how can I measure cant? What angles are “normal?”
Thanks!
Hi there,
i really feel that if one moves the fins all back (cluster) you don’t really make your board looser, if one spreads the fins apart ie: front fins forward 1/8" and back fin back 1/8" of it’s original position you can feel a dramatic increase in hold and drive (sacrificing looseness).
Regarding toe-in, you are correct.
Regarding splay, you can measure that using a set square from the base of the fin to the stringer and the distance from the set square to the fin represents the splay/cant.
An average is 5 degrees, but this varies from 4 deg to 6 degrees depending on the amount of concave on your board, generally speaking the more splay the bigger the fin base should be to counteract the loss of drive.
surfrat
Just how straight is any thruster going ?
If a thruster is going straight is there any weight or displacement over either rail ?
Are you using the rails of a thruster while going straight ?
Is using the rails THE critical performance requirement to effectively ride a thruster ?
If a thruster is going straight is the kinetic energy from all the components of design ever going to escape it’s potential status and realize any amount of it’s potential energy (speed, power, and maneuverability) ?
Interesting that most boards are rarely used to their full potential.
How many surfers are really TURNING their thrusters on rail and how many surfers are just STEERING their boards around to change directions ?
The answer is apparent when you examine the acceleration (or lack of acceleration) of the board when the rider engages the rail in the face of a wave.
That’s why we see so many surfers with too much volume in their boards (from length, width, or thickness) for the conditions their surfing. When a surfer reduces the volume of their boards to an “optimum volume” (enough foam to sustain, support, and yet still control the board through the whole set of maneuvers it performs) the fins FINALLY come under the critical demand that will display their performance characteristics.
Under less than this “critical demand” thruster fins bleed off their performance and increasingly provide nothing more than lateral stability
Obviously optimum volume will vary with the requirements placed on the board by the surfers size and skill and the conditions the board will be used in.
That said, it’s really cool to take advantage of the performance characteristics of your fins with foil and placement. Lower volume boards seem to respond very well to minimum toe and cant. Reducing toe and cant yields greater projection and the reduced volume (with other design features) maintains maneuverability.
When surfing a board with more volume than required by the surfer and conditions more toe and cant will be required to keep the board from riding like a 18 wheel truck on a tight Formula I Grand Prix course.
Thus fin basics vary by yet another set of variables.
hi, the comments regarding how much rail used on a thruster is indicative of all the variables in play when not only shaping a board but also when every surfer surfs one. The interesting thing is, is that every surfer surfs differently, and as i see it more boards are being shaped off computer shaping machines today than ever before providing consistent bottom curves that don’t push water and fin placements that have been tried & tested, what makes those boards go even better will be the surfer’s ability to extract the boards potential by surfing the board where it was designed to: ie: back foot should be between the front & back fins, front foot roughly half way up the board. Interesting to note, only one potential variable can change after a board has been bought by a surfer, the fin set-up.
That being the case, surely fin systems and their ability to change positions to suit surfers requirements has a hidden “added-value”?
Trucker,
The answer to you question is a rather obvious yes. Why else would we be dicussing the variables at length?
Good Surfin’, Rich
trucker …youve heard a few mistaken theories…
moving your fins forward or rearward as a package ,will move the area where you have to focus your weight to turn your board …
fins forward stand further forward to turn …
fins back stand further back to turn …
obviously some boards are gonna get ugly if your standing right on the tail to try and turn them…
some boards will get looser if the fins are further back , coz the shape will require weight further back to get a decent turn…
other boards will get stiffer with the fins back …
all variables count…
increased cant , will increase drive with some rockers and increase drag with others…
increased toe will increase drag with some foils and decrease drag with other foils…
the only real hard and fast rule ,when moving front and back fins further appart , it will increase drive and stiffness…
all variables count…
if you add in one area you have to take in another ,otherwise the final equation is unbalanced…
regards
BERT
""Except, I’ve heard that many pros (long and shortboards) prefer their fin cluster further back than what you’d find on an everyday surfer’s board. Wouldn’t this stiffen things up? Or, have I simply heard somebody’s mistaken theory? “”
Yes with the same fins it will stiffen the board’s action.
Toe-in is the direction of the fin in realation to the fore and aft mid line of the board. When the fins are aimed across this line regardless of how much they are toed-in. More toe-in gives more grab.
Cant is the angle off of vertical.
Do consider searching the archives here. They are full of the answers to questions like these in great detail.
Mahalo, Rich
Cool, thanks…
So many variables to consider!