Forums > Stand Up Paddle General

Multi Year Fin Experiment on "no Toe"(straight) Fins

Reply
Created by jarvisIan A week ago, 8 Jul 2019
jarvisIan
29 posts
8 Jul 2019 3:54AM
Thumbs Up

In 2015 I bought a JP 8'6"x29" 113 liter Surf Pro, and I loved it. The board was fast and performed amazingly compared to all the other boards I had ridden. I then bought the 8'2"x28" 103 liter Surf Pro, and it was awesome, but a little too small for choppy, windy, or wetsuit days. At this point I had become affiliated with JP, but they didn't have a board that was between the 8'6" and the 8'2", but it was allowed that I ride Imagine as they were distributed by the same company.
The Imagine 8'4"x 28 ? 102 liter Impact was more stable than it's dimensions would suggest and became my "anything but perfect" wave board. The problem was that in anything else than powerful, juicy waves it was too slow...just like most of the other boards I had ridden. A lot of boards seemed to slow for average wave conditions. The JP boards all come with "straight fins". Straight fins means that the fin boxes in the board have "no cant" and more importantly, "no toe". This is why the JP's are so fast. They have similar shapes and bottom contours to other popular boards, but the fin boxes are set up without "Toe in".
The Experiment
So, I liked the Imagine, but it was too slow in anything but juice. I thought, why not put straight fins in it, and fix the problem. I was worried that I'd ruin the board's performance, so I decided to put a ProBox fin system in that would allow me the latitude of some R&D. The Probox system without it's plastic inserts allowed me to mold fin bases with different degrees of "Toe" and "cant" and to see what effect it had on the board's performance.
The experiment was a quick success, and the Imagine transformed into a fast, high performance board that worked in all kinds of conditions. I rode that board for two years playing with different fin set up's until I decided on what seemed to work best for 90+% of wave conditions I encountered from Hatteras to Maine. "No Toe", but a couple degrees of Cant.
When I say 90+% I am referring to waves that are head and a half and smaller. I have had several larger days both on Hatteras and in New England, and on those waves "No Toe" fins were too fast. I turned an 8'7" Stun Gun, a classically slow and controlled board, into an out of control, bouncing bronco on a double overhead day at the Hatteras point. When it gets big, a bit of "Toe in" helps slow and control the board. I should have known this as I never liked the JP's in bigger surf, they were too fast, and hard to control. This all makes a bit of sense when you realize that "straight fins" aren't a new concept. Fish surfboards, originally designed in the 70's came with straight fins. They were designed to turn small waves into fun. There are also a couple of companies, one in Australia, the other in Hawaii that make adjustable fin boxes for just this reason. Changing fin set up's can really change a board's performance, changing the "toe in" can radically turn a sluggish board into a fast , weak wave ripper.
Smart Friends
After doing all of this and starting to think about other ways to accomplish the same result without installing new fin boxes, I mentioned this to a couple of engineers that had been working on fins in their spare time. One of them created the fastest sup race fin ever flow tested, the other, literally, works for NASA. I told them what I had found with years of experiments, and they looked at me and said; "of course". "Toe in" is the idea that water does not run straight back, but instead is pushed outward and back as the board displaces water. While this is true, it is not constant, meaning that the amount water that is displaced varies with the weight of the rider, the width of the board, the bottom design of the board, and the speed of the board.
Sups are much wider and higher volume than surfboards, so using the same "toe in" formula creates a board with an unnecessary amount of drag.

Fin Box Designs and Experiments

Instead of changing fin boxes in boards to accomplish a "no toe" set up, I started grinding the bases on fins, and remolding them to fit back in boxes, but without the "toe in". By remolding fins with a "reverse toe" angle I could neutralize the angle of the boxes that were installed in most boards. After measuring the angles of boxes of many boards it seems most have the same angle with a few drastic outliers.
I managed to make a few FCS sets of fins, but if not done perfectly, they are weak, and easy to snap. The Futures style base has been the best option for my experiments, and has proven strong enough to remold, and I have been running experimental fins in boards with these boxes for a couple of years.

Production

With each set of fins taking more time, energy and material than any market would support I wondered how hard it would be to have a batch produced. I asked a couple of small board manufacturers some questions, and found a popular fin manufacturer in Asia. It took some emailing back and forth as I found out that they use the same molds for everyone's fins and just change colors etc. However, after about six months of casually emailing and only about the amount of money it costs to buy a new sup, I have produced a small batch of fins.

If you ride a thruster set up and want to make your, Futures based, board go faster, and perform better in average conditions, I, humbly, suggest you give these fins a try, and it's a lot cheaper than buying board after board, or installing new fin boxes. I had a friend create a small, free website. I, literally, stand to make tens of.tens of dollars on this whole thing. If I sell through these, I'll make straight rear quads, and maybe some different sizes. Here's a link to the humble site:
riptidefins.com/

DHUPEDNORTH1
WA, 61 posts
8 Jul 2019 11:41AM
Thumbs Up

"so using the same "toe in" formula creates a board with an unnecessary amount of drag"

I notice you don't refer to whether, or not, your side fins (with toe or not) are flat foils or 50/50 foils (or something else). Basically all shortboard and longboard ('performance') fins use flat foils as side fins with a toe of close to 3.5 degrees or so historically based on Simon Anderson's original thruster set up. However, I have seen both flat foils and 50/50 foils as SUP side fins.

My understanding of physics in this area is when it comes to 50/50 foils as side fins with any toe, you would be correct. They will largely produce additional, unnecessary drag overall slowing the board down and removing the toe will reduce drag and speed them up.

With side flat foils though I do not see how this would be the case (except at slow paddling speeds but not while riding any reasonable wave at speed). This a well researched area but briefly, a flat foil, like a plane wing will generate an area of lower pressure above the curved surface relative to the pressure below the flat surface of the foil. The current theory (also held by NASA on their website) is that molecules travel over the curved surface at a much faster rate than along the flat surface, and according to Bernoulli's Principle, as the velocity of a fluid increases, the pressure exerted by that fluid decreases. Therefore, a lower area of pressure is created above the curved surface of the foil and the result is lift in the (perpendicular) direction towards the area of lower pressure. This is how planes stay in the air, hydrofoils maintain a boat above the water, and SUP foils work (+ inclined angle of attack).

Simon Anderson was the first (publicly anyway) to recognise that if you give the flat foils toe a bit towards the stringer you have a net lift or 'thrust' (albeit small) in a net forwardish direction (i.e. slight angle forward off perpendicular - hence the original "thruster" name for this fin set up). The downside is the more toe, the increased drag as you turn the fins against the water moving toward it. Anderson found a compromise at about a 3.5 degree or so toe where the thrust (lift) in a net forward direction provided more effect than the added drag against the toed fin in a net rear direction with shortboard sized fins.

Anyway, as I said, some SUPs I've noticed use 50/50 foils as side fins on a slight toe (which I would remove and just use a large centre) so your fins would provide less drag over these by removing the toe and speed up the board. Also, as you say, due to the different SUP board sizes v fin sizes used, it is possible the toe angle may not be quite right for SUPs atm and just following the shortboard setup may not be exactly correct. I'm not sure exactly where I sit on this but I would be curious to see some CFD (or even the more costlier water tank) modelling on SUP bottoms and the interaction with their fins. Either way, well done for trying new things - i love innovation - the more the better.

colas
3243 posts
8 Jul 2019 1:50PM
Thumbs Up

Select to expand quote
DHUPEDNORTH1 said..
The current theory (also held by NASA on their website) is that molecules travel over the curved surface at a much faster rate than along the flat surface, and according to Bernoulli's Principle, as the velocity of a fluid increases, the pressure exerted by that fluid decreases. Therefore, a lower area of pressure is created above the curved surface of the foil and the result is lift in the (perpendicular) direction towards the area of lower pressure. This is how planes stay in the air, hydrofoils maintain a boat above the water, and SUP foils work (+ inclined angle of attack).





Actually, this is a common misconception.
The lift of a wing is provided just by mass reaction, just like rockets: The curve and angle of attack deviates the water or air downwards, thus applying a downwards force. and in reaction the wing is subjected to an opposite upwards force. It is not the acceleration of water that creates the lift, but its change of direction.

Hydrodynamics are tricky, which makes real experiments like the ones of jarvisIan so useful, and whose results are confirmed by the experienced shaper I spoke with. He also told me that surfers and the surfing industry is unbelievably ignorant of fin topics, most surfers just choose the fins by their colors or sponsored rider and this makes it nearly impossible for superior fin designs to get traction on the market. (But I hope Quobba can become the exception that confirms the rule).

jarvisIan post is quite interesting however. I only have FCS boxes in my boards, and the only commercially available fins are for Future boxes (*), but I will try to see if I can manage to butcher some twin fins to reduce the toe in angle on my small wave SUP... or maybe have twin boxes installed in supplement to the thruster/quad ones, but with no toe in.

(*) riptidefins.com/

Kami
1376 posts
8 Jul 2019 3:03PM
Thumbs Up

My dime would like to say that fins do make glide in the right direction the planning area first and then the rest of the board. So they have to be able to dig in the water to find some resistance and drive the rail and planning area in the direction you want to go.
For a modern shortboard with a narrow concave bottom, fins are concavely foiled like Nexus from FCS are and also are the complementary planning area of these tiny hulls of 5'8" and can be settled with toe around 3.5? and some cant as well. Have in mind that Toe is for manoeuvrability and Cant for carving ability.
So for a SUP with has a large planning area which is impossible to bury the whole planning area and therefore fins, fins must be settled the more parallel to the rail as possible up to the outline and widest point of the board and square to the bottom shape. So No toe and a slight cant to have the tip of the side fin in line with the outline /rail of the board.

Jarvislan, your fins are a good idea for me? good job ;-)

BTW, bottom plan shape is a heavy parameter to settled fins because if the bottom is convex it will really need no Toe because the board would be loose. In the case of the concave bottom where the board would be stiffer , it would need some toe...
The meanest things to say about Fin settlements is that the fin base has to be in the direction of the water flow

SRrat
WA, 230 posts
8 Jul 2019 8:20PM
Thumbs Up

Toe in and cant is something I too have been pondering .
Have recently bought a board finned like a NPJ Duo, two double foiled largish fins set a fair way back , parallel to the stringer and set much closer to it as well. Feels fast and loose , it's early days yet but I like it.
The hold advantage of fins closer to the rails with perhaps a drag reduction?

Put a quad set up in my SUP. Naish single foils up front and double foiled small arc fins in rear. Was only with the rear quads in place did I notice the front to fins had different cant angles, side to side. Managed to improve it some with a small plastic shim on the offending side.??
Jarvislan' s system might have made it a simple adjustment. I probably need to reset the plugs(favs).
Same board is a little slow to get going on smaller waves, almost an extra paddle and a small pump??
Cheers

jarvisIan
29 posts
8 Jul 2019 9:22PM
Thumbs Up

DHUPEDNORTH1,
My fins are, basically, AM2's, so they are flat foiled on the inside.
The hydrodynamics behind what makes a fin more efficient is a science that few have actually had the equipment to run tests upon, myself included. I have a couple of engineer friends that have created what they say is the "most efficient" foil (Fin) possible, and I may help them produce it in time, when they are ready. Their educated opinion is that the current flat foil fins are closer to the mark than 80/20 or 50/50 foiled fins that have been produced. In other words, flat foil hit the tree, but missed the target, but 80/20 and 50/50 are completely off the mark. My main cohort, Keith McCulloch of CNC fins is the guy who created the NSP race fins that have been very successful is sup racing. He has other associates that I have met and exchanged ideas with that are also involved with fin development.
This whole project came about after enjoying the engineering successes of JP boards, and realizing that most boards (of similar shape) were slower in comparison. The fin and angles I have come to favor come from trial and error testing. I've spent a lot of time grinding, and remolding fin bases at different angles. The sets I had made should create a 0 degree toe angle in most boards. Though it is funny when you really start paying close attention to the measurements, you'll find fin boxes out a 16th, or even an 8th of an inch on some boards, so perfection isn't that easy to obtain. However, fear not, my favorite board was produced with fin boxes that are visibly out of sync with each other, and it is still my best board.

cbigsup
354 posts
8 Jul 2019 11:59PM
Thumbs Up

I had the interesting experience of testing some no cant no toe protos in my Infinity RNB 8'5". Quads.

Immediately noticed the board paddled faster and was much quicker in small mushy waves.

Not quite like a twinnie, but way more fun than the stock
thruster setup.

I refuse to give them back!

Best of luck Jarvis!

DHUPEDNORTH1
WA, 61 posts
9 Jul 2019 11:19AM
Thumbs Up

Select to expand quote
colas said..

DHUPEDNORTH1 said..
The current theory (also held by NASA on their website) is that molecules travel over the curved surface at a much faster rate than along the flat surface, and according to Bernoulli's Principle, as the velocity of a fluid increases, the pressure exerted by that fluid decreases. Therefore, a lower area of pressure is created above the curved surface of the foil and the result is lift in the (perpendicular) direction towards the area of lower pressure. This is how planes stay in the air, hydrofoils maintain a boat above the water, and SUP foils work (+ inclined angle of attack).






Actually, this is a common misconception.
The lift of a wing is provided just by mass reaction, just like rockets: The curve and angle of attack deviates the water or air downwards, thus applying a downwards force. and in reaction the wing is subjected to an opposite upwards force. It is not the acceleration of water that creates the lift, but its change of direction.

Hydrodynamics are tricky, which makes real experiments like the ones of jarvisIan so useful, and whose results are confirmed by the experienced shaper I spoke with. He also told me that surfers and the surfing industry is unbelievably ignorant of fin topics, most surfers just choose the fins by their colors or sponsored rider and this makes it nearly impossible for superior fin designs to get traction on the market. (But I hope Quobba can become the exception that confirms the rule).

jarvisIan post is quite interesting however. I only have FCS boxes in my boards, and the only commercially available fins are for Future boxes (*), but I will try to see if I can manage to butcher some twin fins to reduce the toe in angle on my small wave SUP... or maybe have twin boxes installed in supplement to the thruster/quad ones, but with no toe in.

(*) riptidefins.com/


Sorry but going with Newton's 3rd law and suggesting Bernoulli's Principle is a misconception is just wrong (and NASA and I imagine most engineers and physicists in thermodynamics agree with me as my understanding is just from their research and results). Plus, lift still provides effect (allows planes to fly) when the angle of attack is minimised (thus, Newton's is a lesser force acting on lift than Bernoulli - or to get more benefit from Newton's 3rd law requires a much greater increase on drag with a greater angle of attack to improve downward force).

The following excerpt from the PhD thesis by Dr Anthony Livanos (credit to him and I hope he sees this as helping educate the surfers and not plain old copyright) provides a great description of forces on surfboard fins. I recommend those interested in fin fluid dynamics reads at least part of his thesis as there are also some great pics and CFD modelling which is quite interesting (and no, I am not Anthony) [docplayer.net/10812958-Computational-fluid-dynamics-investigation-of-two-surfboard-fin-configurations.html]

"Lift forces:There are quite a few explanations of lift published in resources and available on the internet. Unfortunately, theories are mis-applied and lead to incorrect theories being widely accepted. Theories of lift have been the source of many arguments. The primary reason for this is people choose to believe either a Newtonian point of view, or a Bernoullian point of view.

Incorrectly applying Bernoulli's theory leads us to the theory which is known as the "equal transit time" or "longer path" theory. This theory states that foiled bodies are designed with the upper surface longer than the lower surface in order to generate higher velocities on the upper surface because the molecules of gas on the upper surface have to reach the trailing edge at the same time as the molecules on the lower surface. From Bernoulli, pressure of a fluid is inversely proportional to velocity. The incorrect theory then invokes Bernoulli's equation to explain lower pressure on the upper surface and higher pressure on the lower surface resulting in a lift force. The correct theory of lift is based on 'flow turning' and is actually a combination of both Bernoullian and Newtonian views.

When a body is immersed in a moving fluid, the fluid flows around it, with varying velocities depending on shape, size and drag factors. This variation in flow velocities causes variations in pressures. Integrating the pressures over the entire body, not just the top side, equates to the total hydrodynamic force acting on the body. This hydrodynamic force is comprised of lift, perpendicular to the flow direction, and drag, parallel to the flow direction. This makes the basis for the Bernoullian part of lift.

The Newtonian part is based around Newton's third law of action and reaction. Since this hydrodynamic force is acting on the solid body, the solid body must also be acting on the fluid with the same force. This force acts to 'turn' or deflect the fluid. So in essence, both Bernoulli and Newton are correct.

Factors affecting the generation of lift are grouped into two categories; Object and Fluid. In relation to the object, shape and size will affect the generation of lift. In terms of a fin, this relates to the fin's foil, thickness, and camber. Overall plan form shape will also affect the lift generated. Plan form of fins can vary in terms of rake and depth. The discussion of how these factors affect the fin are not relevant as the testing is only being done on two sets of fins, with shape and size being constant.

Hydrodynamic forces are definitely proportional to surface area of the fins. The Coanda effect is definitely an important consideration in regards to analysis of forces on foiled bodies. The Coanda effect states that a moving stream of fluid in contact with a curved surface will tend to follow the curvature of the surface rather than continue to travel in a straight line. Relating back to the theory of lift, this effect would essentially aid in 'turning' the air, thus creating more lift. Certain foils would lead to a more pronounced Coanda effect and consequently more lift.

With regards to the fluid factors, properties such as viscosity, mass of fluid and velocity of the fluid relative to the immersed body all contribute to the generation of lift. The velocity of the fluid is constant for both trials, but it is known that higher velocities correlate to larger hydrodynamic forces. Fluid viscosity and velocity in terms of surfing are all dictated by the waves and oceans. Since these are constants, other factors must be optimised to achieve greater lift performance.

The Thruster setup derives its name due to the fact it provides a forward thrust. This thrust comes from the two side fins. The overall lift force on the fin is biased slightly forward on an asymmetrical fin to begin with due to the foil. Increasing the Toe-In angle increases forward thrust to an extent, until the fin reaches a stall angle. At this point flow separates from the fin and reduces the lift dramatically.

Since the Single fin setup is only one fin, with no Cant or Toe-In, it will be producing less lift as opposed to the Thruster setup. The Thruster setup will be providing more lift, but also has increased drag, consequently reducing the lift."

colas
3243 posts
Tuesday , 9 Jul 2019 12:45PM
Thumbs Up

DHUPEDNORTH1... your quote just says exactly what I had summarized. It is the "flow turning" that creates the lift by mass reaction. And of course the only way for a fluid to exert a force on a fin is via changes in pressure, obviously.

jarvisIan
29 posts
Tuesday , 9 Jul 2019 7:00PM
Thumbs Up

Well, the good news is that "straight fins" are, no doubt, faster than" toe in" fins on the boards I've experimented upon.
The other good news is that one of the PHD's I've conferred with is, actually, a NASA engineer and flow expert who is involved with fin development as a hobby. He confirmed that "no toe" fins would, "of course" be faster especially in a sup, and then went on about the variables that included: Speed, foil shape, foil type, width of board, volume of board, bottom design of board etc. Mike is a polite, and courteous man, but even so, I could tell he was a man only interested in absolute scientific perfection. In one conversation at a dinner, he and Keith, both engineers, were having a chat about current production fins. They both talked of the inefficiency of currently available fins, and agreed that there seemed to be very little science applied in their design. Mike has developed some very efficient fins, and has tested all manner of shapes, designs and angles with the equipment at his disposal. He asked some questions about the manufacturing process, and what I had found in my little experience, so all we can hope is that he and Keith decide to go ahead and let the rest of us try some of their designs.
Mike openly spoke about what the most efficient fin design looks like, Keith talked about some of his designs that are similar but with practical modifications. It is exciting stuff, and I hope to be testing some of them in boards soon. For now, the AM template, flat foil is the industry standard. If guys like this throw in we'll have some very efficient and interesting options.

Piros
QLD, 5475 posts
Wednesday , 10 Jul 2019 7:27PM
Thumbs Up

I was onto the no cant or toe few years back . I even brought out fins with no cant . Stop doing it due to factory issues I'm China. Still have a few in stock .

jarvisIan
29 posts
Wednesday , 10 Jul 2019 7:04PM
Thumbs Up

Piros,
I bought a set of your fins! I don't remember them being "no toe" though, Am I wrong?

Piros
QLD, 5475 posts
Thursday , 11 Jul 2019 1:56AM
Thumbs Up

Yes that's right the where zero cant and the JP boards were zero toe .

colas
3243 posts
Friday , 12 Jul 2019 5:19AM
Thumbs Up

Select to expand quote
jarvisIan said..
He confirmed that "no toe" fins would, "of course" be faster especially in a sup



I find this "of course" quite suspect, because he seems to suppose that water flows in a straight line over a SUP hull, which is definitely not obvious. For instance Experiments with windsurfing boards by Witchcraft showed that the water was deflected to the sides, the amount depending of the tail shape, hull bottom, speed... and the depth: water was more deflected near the hull. Witchraft then made "twisted" fins, with more toe-in at the base than the head to better fit the water flow.

jarvisIan
29 posts
Friday , 12 Jul 2019 7:03AM
Thumbs Up

Correct Colas, but the majority of the surface area of the fin was straight because the water effected by the board and moving outward was only near the bottom of the board. That's why straight fins are faster. It's not that they are "twisted" and perfect, but that they better match the water flow than do fins with "toe" . This is even more true with sup's as they are wider than windsurfing boards, and moving slower, thus pushing less water outward, and all the way out to those fins which in relative terms are very far from the center line of the board.

colas
3243 posts
Friday , 12 Jul 2019 2:06PM
Thumbs Up

Select to expand quote
jarvisIan said..
This is even more true with sup's as they are wider than windsurfing boards, and moving slower, thus pushing less water outward,


Again, be careful of what seems "obvious". For instance, Witchcraft found the opposite, the water was more deflected on the side at slower speeds.

Here is an article about Witchcraft "twisted fins":
windsurfermag.designunltd.co.uk/magazine/twisted-windsurfing-fin-witchcraft-flow-optimised-multifin-thruster/?params=Mjd8MzY3fDA=

Alas, neither the Witchcraft nor the Future "Twisted" fins seem to be available anymore. I guess there is no market for good fins, very few people buy fins, and only based on the looks, not the actual performance. I hope that Quobba (and C-Drive) can overcome these odds.

jarvisIan
29 posts
Friday , 12 Jul 2019 7:05PM
Thumbs Up

Colas, I recently had that conversation with Keith of CNC fins in reference to some prototypes he and Engineer Mike had developed. I took one look at them and said; "surfers may not buy them because they look different". Keith agreed and there is talk of trying to do the best they can from a hydrodynamic standpoint while still making it appear like a familiar outline. I hope they release both, but it's risky.
As for "no toe" fins, it's really easy to test, I've been doing it for a couple of years. "No Toe" fins, in sup's is faster. It's obvious when you take a board that's a bit slow, and put "no toe" fins in that the board is simply faster, and performs better. I have tried this experiment on a lot of boards, and from several different manufacturers.
Here's a photo of an early prototype set of fins being re-cast, I'll bet Cbigsup recognizes the fins in the mold.




colas
3243 posts
Friday , 12 Jul 2019 9:23PM
Thumbs Up

Select to expand quote
jarvisIan said..
It's obvious when you take a board that's a bit slow, and put "no toe" fins in that the board


Well, we agree. I was warning about saying "obvious" just on the looks of things, as opposed to actual tests - like you did, nice setup!

jarvisIan
29 posts
Saturday , 13 Jul 2019 2:18AM
Thumbs Up

Thanks Colas. The project has been fun, and I'm very pleased with the performance. I only had 100 sets of fins made, and they're trickling out the door. I haven't shipped any to Australia, but I'm sure that could be sorted out if anyone down there would like to try a set, and doesn't want to muddle through the process of creating jigs, and molds.

cbigsup
354 posts
Sunday , 14 Jul 2019 10:06PM
Thumbs Up

Select to expand quote
jarvisIan said..
Colas, I recently had that conversation with Keith of CNC fins in reference to some prototypes he and Engineer Mike had developed. I took one look at them and said; "surfers may not buy them because they look different". Keith agreed and there is talk of trying to do the best they can from a hydrodynamic standpoint while still making it appear like a familiar outline. I hope they release both, but it's risky.
As for "no toe" fins, it's really easy to test, I've been doing it for a couple of years. "No Toe" fins, in sup's is faster. It's obvious when you take a board that's a bit slow, and put "no toe" fins in that the board is simply faster, and performs better. I have tried this experiment on a lot of boards, and from several different manufacturers.
Here's a photo of an early prototype set of fins being re-cast, I'll bet Cbigsup recognizes the fins in the mold.





Jarvis, Did you make all 100 sets the old fashioned way in that gadget?

jarvisIan
29 posts
Sunday , 14 Jul 2019 10:25PM
Thumbs Up

Ha ha no CB, I sent a set to Asia, had them make a mold, and then had them make a small batch. I, even, put up a web site so folks could grab a set. They make my slower boards faster. I like to run them with a slightly smaller center fin on most boards.
riptidefins.com/





Subscribe
Reply

Forums > Stand Up Paddle General


"Multi Year Fin Experiment on "no Toe"(straight) Fins" started by jarvisIan