Doug, of Wavegrinder Surfboard Fins
I designed the Wavegrinder longboard fin with with performance longboards in mind. My idea was to create a fin that has high lift and low drag–a fin that behaves like a larger fin in terms of producing adequate side force, but without the large size and excess drag of a larger fin.
When I first tested prototypes of what morphed into this surfboard fin, I tried some designs with winglets and others without. I was amazed at the difference the winglets made–especially because they’re so small. I know this in part because while surfing some of my prototype designs the winglets broke off (Dang! There goes another $250!) Also, I tried larger winglets and smaller. On some prototype designs the winglets were too big, and the board rotated right out from under me. So I ended up with this design, and loved it. I had lots of surfers try it. And thy told me the same things I had thought about the fin, so I felt like I was really onto something. So I out it into production.
The Wavegrinder longboard fin.
Some of the feedback I got from surfers I’ve posted on the testimonials page. Surfers have bought it for lots of different boards, and have reported excellent results. Surfers use the Wavegrinder fin on performance longboards, classic longboards, guns, single-fin shortboards, and standup-paddleboards. I’ve also had folks buy them for kiteboards, windsurfers, singler-person submarines, and for unmaned drones. Pretty cool.
I wanted to make a fast and maneuverable surfboard fin. A sports car of fins. I started with a blank slate, not thinking that he fin should look like all other fins. In fact, I wondered whether other fins were wrong because they had failed to evolve over the past several decades, whereas other things like airplane wings, boat keels, spaceships and car spoilers all had sprouted wings or winglets. Existent fins, I figured, looked pretty much like the fin I had had on my board in 1984. I had one focus in mind–to create a fin with high lift and low drag for better rides. Hopefully this will push the sport, and lead to other out-of-the-box thinking.
Wavegrinder longboard fins should be placed about two inches further back than ordinary fins
The chief features of the Wavegrinder surfboard fin with winglets that distinguish it from other surfboard fins:
- Hydrodynamically engineered, and CAD designed from lessons learned from NACA, NASA, Boeing, America’s Cup and NASCAR
- NACA double-zero foil shape (to prevent stalling during turns)
- High aspect ratio planform (upright and narrow to maximize lift per square inch of surface area)
- Low sweepback angle (rake)
- Short fin base (to decrease interference drag while maximizing fore-and-aft adjustability in the fin box)
- Bulbous forward fin projection at the fin base (to minimize interference drag like ships’ bows)
- Cutaway at the fin base (to decrease interference drag)
- Lexan polycarbonate (the same material used in bulletproof glass and fighter-jet canopies)
- And, of course, winglets (to inhibit stalling during turns, and to make the immersed surface area more efficient)
NACA double-zero foil section minimizes stalling
Specifications:
- Surface area: 30.54 square inches
- Height: 9.25 inches
- Color: cobalt blue only, as shown, at present
- Price: $65 US
The spot marked “center of area” is the spot at which the lift force works.
Wavegrinder longboard fin's winglets.
The WG is a high-aspect-ratio fin.
Wavegrinder longboard fin.
Wavegrinder longboard fin.
The WG has a wide range of adjustments.
Wavegrinder fin fits most standard fin boxes.
I have a 2+1 setup on a 7’6 performance long board. Is the wavegrinder meant to be ridden as a single fin pushed way back on the board and if so is it designed to “pump” down the line as a single fin due to it’s design?
Zane–
Well I don’t mean to be cute, but the WG is meant to be a high-lift, low drag fin (given its planform shape, its NACA foil section, its winglets, and its other features discussed on this site) with a wide range of adjustability (given its short fin-base length). But because of these features, many or perhaps even most find that they can dispense with their asymmetrical and toed-in side bites, and thus can increase their performance. Although both removing the side bites and moving the center fin back might seem counterintuitive, we recommend that you try this, and if in doubt, move the WG further back. Then return to your previous setup, and compare in some sets, one then the other setup, to see the differences in performance.
Typically side bites have about 13 square inches of surface area, depending on the fin, and are toed in, so you’ll lose quite a bit of drag when you pull toed-in side bites off the board. But you’ll also lose the lift (or “hold” in surfing parlance) the side bites provide. So the remaining center fin needs to make up at least somewhat for the lift lost by the side bites. Given the high-lift features of the WG, we believe it makes up for the lift lost by removing sidebites, and does so with the drag of a 30.54 square-inch fin. It behaves as a larger fin, providing good “hold” (lift), while minimizing drag.
Once you’ve made the changes, probably you won’t feel the need of pumping the board, which personally I feel is a byproduct of drag enhanced by toed-in fins, but instead you’ll notice slippery speed and snapping out of turns. I did, which is why I pursued this project, and many or most who’ve bought the fin have said the same thing.
But you might try these steps, and then provide feedback once you’ve got some definitive impressions.
Doug.
Do you have an idea when the FCS style fin will be available?
If you’re talking about a small thruster that fits the FCS system, we have some beta versions available. They’re a bit tender and a bit too small, so we’re not advertising them at the moment. But contact us va email if you’d like to purchase some of these at reduced cost and check them out, while they last. We’re looking for funding for the next generation fins, but just aren’t there yet.
I guess it will be a while before you have fins for shorter boards that just have the FCS style plugs
Just bolted the wg to my 9′ Mal. In short, loosey goosey has been turned into a guided missile. Love it. Well done guys.
Question – if I wanted to try the wg ‘system’ on a short board, would the thruster set up better, or could i go the larger single fin. I am keen to try the single fin on a shorter board.
Ian
As a general rule, one high-aspect fin is better than 2, 3, 4 or five low-aspect fins. This is why biplanes evolved to monoplanes.
High-aspect foils have more lift and less drag per unit of surface area. This drag reduction also is why sailboats have evolved from low-aspect square rigs with many masts fore and aft to a single, very tall mast with a high-aspect sailplan.
Many shortboards use a 3-fin setup (or 4 or even 5), typically three 4.25-inch fins, which generally have a bit more than 13 square inches per fin—or 39 square inches for the 3-fin system. Each square inch causes drag, of course.
And in a multiple-fin system, much of the combined area is the in place where it is least effective, at the root or base of the fin, where each of the fins attach to the board, as contrasted with the tip. The tip of the fin, foil, wing or sail has less interference drag (drag caused by the hull) than the location where the fin, foil, wing or sail attaches.
Thus state-of-the art sailboats have sails with squared off sails at the top, becaseu they want to devote much sail area to the tip for a given length of mast height (and also because of rating rules), thus devoting a lot of sail area at the tip, away from sea level, away from the boat, and up in the less-interrupted flow of air. (See AmericasCup.com). Note that the WG’s squared-off shape–devoting area to the tip as opposed to the base–also is similar to the Red Bul airplanes’ wing shapes (Red Bull air race photos).
Intuitively we know about interference drag. For example, on a windy day, you get low to the ground where the surface friction of the earth slows down the wind, while as we go higher, to the flagpoles, buildings, and planes flying above, the breeze gets progressively stronger. This is because of the friction of the earth that slows the wind at the surface–it’s called a wind gradient.
But nonetheless, most fins put a lot of area where is least effective at producing lift–at the base rather than at the tip.
Each of the typical fins within a typical 3-to-5 fin system have a root or base fore-and-aft length of several inches per fin, about 3.5 inches each, for a total of about 10.5 inches in a 3-fin system. By contrast, the single WG has a fin base of 4 inches. Thus the WG has 60 percent less of the inefficent root or base length. This reduction in root length, by the way, is why there are cutaways, both in our fin and others.
Similarly, and analogizing again to current boats compared with square riggers, square riggers have a sail plan that is much lower and also longer fore-and-aft as compared to modern tall, narrow, high-aspect designs.
Thus compared to the common 3-fin system of 39 square inches of surface area in a low-aspect, 3-fin system, our WG is 30.54 inches—and like the state-of-the art sailboats and airplanes referenced, is high-aspect, to increase lift and to decrease drag per unit of skin friction/surface area. And much of the WG area is at the tip, like the squared-off modern sailboat sails, the place where the winglets are placed.
So, if you put in 3 fins like everybody else, you’d have 39 square inches with a combined fin-root length of 10.5 inches, whereas with our fin, which might look big by contrast, you’ll actually be shaving off (39 – 30.54)/39= 22 percent of the total fin surface area, and shortening the fin-root length by (10.5 – 4)/10.5 = 65 percent.
Fins are not magic-no matter what all the promotional mumbo jumbo says. The WG isn’t magic either. Fins only do two things—they create lift and they create drag. The question is how much of one and how little of the other. And they ignore the effects of the board, or of other fins in a multiple-fin system. Most companies say this is a nose-rider, that one is for long-drawn-out turns, another is a pivot fin, and blah, blah, blah. Then people believe it and buy lots of funky shapes.
But overall, we recomend decreasing fin surface area, and decreasing fin-root length, up to the point that the board becomes too loose–then adjust. Our WG was designed with this reductionist philosophy in mind, and we amped up the lift the fin generates with winglets and other attributes to generate enough power (lift) with minimal drag.
Hopefully this answers the question?
Doug
Thanks Doug,
I think every ‘angle’ of that question was covered. Will be getting a custom shaped short board and fitting a WG. Can’t wait. One more question for the Shaper – what is the best bottom contour to get the maximum out of the WG? Single concave, double, twin V, etc? Look forward to your response.
Ian
Well I am not a board shaper, so don’t really feel that I can give an educated answer. I have some ideas, but nothing I’d want anybody to rely on.
hi,
Iwould like to use the fin on my wind SUP a Quatro 11.4 that has a 2+1 set up with fcs system side bites .
question :
can I use them for sailing in 5-15 mph ,
will they hold up ,
can I get ta thruster set for the fcs side,
thanks for your reply in advance ,
Aloha ,Joe
I believe the longboard fin would work fine. But I suspect that our 1st generation (2010) beta edition small thrusters would be too lightly built for the loads of sailing SUP. We have designed a set for possible kiteboarding use, but they’re not ready yet. And yes, we still have some first-generation thrusters for sale at half price, while they last–$11 apiece. Shoot me an email and I can send you a paypal invoice for some if you’d like.
Doug,
I have previously purchased the longboard fin. I may be interested in also trying the thrusters as side bites along with the wave grinder single fin as a 2 +1. What do you think?
The answer depends on what you want or prefer. More fins will add turning ability/resistance to turning by adding lateral surface area and thus producing more side force. You might want this additional side force if you are a bigger guy with a bigger board or with softer rails or flatter rocker, for example. But of course adding more surface area adds more drag, which will slow you down. The drag of the side fins’ surface area is a result of not only the additional surface area, but also of the typical toed-in orientation of side bytes–they are not both oriented toward the path of travel; the are angles in at the front, which helps if only one is immersed, but this is a relatively small percentage of the time spent surfing. Have you already tried scooting your WG longboard fin all the way back in the box? Something you might try if you’ve not already done so. Try this, five waves or so, then go back to the original placement, and test the difference.