Discussing Wavegrinder scientific fin design

I also have one of these wavegrinder single fins but only surfed it once or twice a few years ago before putting it away and being distracted by my own fin creations. it might be time to revisit it again and give it a fair run in the right board and right waves.
If someone wants to buy a 5.7" thruster FCS set I will happily pay 1/3 of the cost to get one of the fins. Or I’m happy to buy the full set myself if there are two others who will take a fin off me for 1/3 of the cost each.

makes me happy to see those willing to be open minded discover the same wonder of fun I have found in my own trials
that little skinny fin holds its own if you have the right board

I rode it again in the 9’7", in the very middle of the box, and once again I really liked the feel, and the fin location further forward was easily noticed and appreciated. Previous location was about 7/8" inches from very back of the box.

Waves were clean and waist to belly high max or so, with many smaller ones ridden. I rode it at two different reefs paddling distance apart and even snagged a mysto set wave halfway across which aided the transition from one to the other.

Near the end the session, I was going right and rebounded off a left coming at me and then angled left, going left, and felt the fin wobbling in the box right off the bottom in the flats.

Once back outside I checked it and the fin had spit out the Aluminum foil tape I had adhered along the fin base upto the screw, to tighten it in the box, and it was wobbling pretty badly. I kept feeling it wobble on subsequent waves, mostly when in the flats and then beginning another turn, flexing the fin, and cut the session short as it felt really weird when it started vibrating and kept spitting out more tape and getting even looser.

One thing I had not noticed before, is that there is a small scallop in the foil, just above the base of the fin where it resides in the box. About 8mm tall and corresponds to the little jutting forward piece and the cutout at the rear of the fin. I assume it is to reduce the interference drag. I’ll see if I can photograph it properly.

I think once I find its sweet spot in the box, I will make the base of the wood fin I plan on making, the full length of the box itself, perhaps with two screws and plates.

I really liked how it glides seemingly frictionless across mushy flat sections and makes it easy to carry momentum. Other ride characteristics i noticed today were as reported before, yet it was easier to turn with the fin farther forward. There is still something about it on my forehand which feels kind of weird, usually at the end of a hard bottom turn. I don’t know how to describe it but it is kind of like the nose does not want to go back down to the face of the wave. Like the winglets are a little too happy sucking the tail deeper when it is sunk during a hard bottom turn, but I do not feel this on my backhand, and I can certainly put more into my backhand bottom turns. I did not notice this on my smaller longboard that has less tail rocker.

Whan paddling fin first across the shallows, there is very little tendency for it to try to track left or right. Very easy to steer paddling the board backwards and only really feels weird when going over a wave in that orientation. Usually I flip the board around once there is no risk of it hitting reef, but being so easy to steer backwards, I just flipped the board around when fully outside as it did not feel totally unnatural.

I’m sold.
I can’t find any detractions other than that forehand hard bottom turn weirdness, which I can probably anticipate and perhaps negate in the future, in either of these two boards. It does not fit tightly enough in my worn stretched finboxes, no Idea about how it would be on a new fin box.
The fin is faster, looser and will not bust loose even rail grab pig dogging from too deep on my backhand in 2/3 trim where I can pretty much disengage my old fin at will. The confidence after riding it 3 sessions on 2 different boards is up, way up.

Even with the winglets digging on my bigger heavier more tail rockered board, it is noticeably faster.

What I wonder about now, is how the stiffer version would compare. The only thing which might be called a detraction is one can’t really feel the fin, like one’s tires are under inflated during a turn, but it goes where it is pointed and goes there fast, and It has never lost traction where I know my regular fin set up would have done some drifting before recatching.

I still can’t believe it is noticable when paddling, but it is. Also when going over a wave, letting the white water pass under the hull while climbing the board. The passing wave just lets go of the board faster and reaccellerating across the turbulence after the wave, is also more rapidly accomplished, making me even more of a paddling menace. This extra advantage comes with a small increased measure of guilt, but crowds have been light mid day when i have gone out, and it is more of a longboard type of wave with only a very few guys who ride HPSB at this size.

I really want to try it again in my smaller longboard in overhead waves, but that could be a ways off before that happens again, but I am not letting it go until that happens or my own wooden copy is finished.

I think I am putting my current project on hold while I start making my own out of wood. No intentions to make them for anyone else. I’d charge way more than 64$ anyway.

I honestly do not think I will ride a traditional style fin in either of these two boards again, if given a choice.

I no longer really care that it does not look right, because, itfeels right.

I really like how detailed your ride reports are.
You have convinced me that some people, aka as good surfers, can indeed tell the difference between fins. I was a bit doubtful about that, born out of my own lack of surfing skills no doubt. I only got into surfing at 29, so I don’t have too much of a chance to get any good at it. Feels the same though I’m sure when I sometimes manage to do a good turn or make a steep drop or get a long ride etc.
But I cannot differentiate the effects of slightly different fins on the background of difficulties caused by my own mistakes. Sometimes I get what feels like a great ride, sometimes I blow every wave in a session. A very ‘noisy’ background to test fins against.
Yesterday I surfed with the WG2 fin at Kirra on low tide, only got one short wave, too sucky and fast for most surfers, let alone me. The board did not do anything unexpected and did not hinder my surfing further than my own limitations did. It was a pain to get the fin to not wobble in the box, and that’s a brand new board. With three cable ties underneath the fin it was nicely stuck in the box. I’d want to fix that more permanently if I ride this fin more often. I only get short windows of opportunity and don’t want to spend 5min fiddling with the fin before going surfing.
Anyhow, thanks again wrxsixeight, for you detailed ride reports. Much appreciated.
I don’t mind at all if you keep the fin longer and make a wooden version of it. I don’t think it would take any profits from the manufactures of the WG fins. If this fin is as good as they claim, then the price is cheaper than you can make one yourself, unless you already have all the equipment and you do not count your time as a cost. (Of course, if the fin is rubbish, the same applies! HAHA! But so far, I still have not seen a single negative ride report of this fin).
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I’m trying to get my printer to work, I have some annoying issues with it at the moment, it’s useless for fin printing because it introduces a weak layer or several in every fin. If that was not the case, I’d be certain I could send you a BLEF adaptation of this fin for testing soon, but at the moment I’m getting nowhere fast with this printer.
I received a very promising new filament called bioFila which might be great for fin printing if it lives up to the advertisements. Stronger than regular PLA, not melting in a hot car, not warping during printing, no problems not sticking to the print bed (but sticking too well), but still made from renewable materials and ‘biodegradable’ (if your compost heap gets really hot).

Find a Cheyenne Horan star fin and try that as a comparison. They come up on eBay fairly often.

there’s so much more out there to explore so get cracking










I do enjoy experimenting with fins, and was intrigued when I started switching fins when FCS first came out in the 90’s, and could easily notice the slight difference a little more or less fin rake depth or size made to the board.

This WG2 fin, the difference between it and my regular fin set up is vast. I wonder what other differences there are between the wg1 and the wg2 other than the lower winglets on the WG1, and what other refinements are in the works.

The boards I am using them in are well known to me in all sorts of conditions. My 9’7" has been my favorite longboard since the summer of 2003. The 9’3" pintail was made in September or October of '97 after hurricane swell Linda when my shortboard could not paddle fast enough aganst the current to get me where I wanted to be. I almost let the 9’3" break in half or perhap thirds back in 2011 when I tried it with a smaller 8" fin, and was blown away at how much better it surfed. I had always been in the big honking single fin mindset on a longboard, upto that point.
I then laid unequal length tapering cedar strigners along each side of finbox on the super thin tail, and Inlaid some cedar planks over the stringer top and bottom with glass over and under for the I beam effect. I also made the 8" carbon haloed zebra wood fin for it at that time and my first wave after the rebuild I started laughing maniacially as I was afraid the extra weight and much reduced flex would have killed the board, but it felt even better.

Later on I added fcs plugs behing FU box and loved the extra hold and drive of the inline trailer, especially on forehand cutbacks. The wg2 fin in this board is amazing. Hard to imagine any other fin riding better but I thought the CF haloed zebrawood fin with trailer was as refined as it could get, and the wg2 simply eclipses them in speed and maneuverability, and honestly feels like cheating.

5 proboxes are going into my next short board/speed egg, and I will definitely be trying everything which I can get my hands on, or make for them, but I might have to support wavegrinder and buy a set if I can ever get my financial act in order as making wood fins is time and labor consuming better spent making money instead.

I know nothing of 3d printing, What is the flex and strength like on your results?

I admit I was kind of afraid the WG2 fin wobbling so excessively might cause it to break. I’ve had other wobbly fins but they never started chattering noticeably as this one does in a loose box when trsansitioning from one rail to another. I have a friend with a star fin and i put it in my 6’8" and it wobbled so badly I never even tried it.

I’ve got two layers of blue masking tape on each side of of the WG2 fin right now and it fits tightly in the center of the 9’7"'s box, but for how long? I hope my lower back loosens up as i want to ride it again today, the buoys have risen slightly, the winds are light. If it does not I will be making dust instead. I found a leftover piece of Zebrawood large and thick enough for two 1/2+ inch thick WG2 copies.

Regarding flex of 3D printed fins, they are not as stiff as fibreglass fins, but not as flexible as the Wavegrinder fins. I does depend on details, material used and what carbon rod inserts are used.
First approximation of the layout of carbon rods for the bumpy front edge WG fin shown below. I’m waiting for the rods to arrive, seems to me that they are cheaper than the arrow shafts I used initially, and due to multiple smaller sizes I can fit many more tubes into a fin.
I’m quite confident they do not snap off easily with the carbon rods, but real world testing is required.

I’ve used the solid carbon rod thing in wood to reinforce base. i was wetting out strands from unidirectional roving and just hanging it and when hard enough,epoxying that into predrilled holes only a few inches deep in the wood base. I previously used SS screws, but they rusted when encapsulated in epoxy. The carbon has not broken.

I surfed it again in some really choppy slightly increased S hemi swell and once again really liked it. I had the lineup to myself as it was choppy and got windier as I walked to the sand.

I was able to bust the fin loose on a late steep drop rail gabbing on my backhand and digging my whole left arm into the wave, and it reengaged buttery smooth. It was not even a concern that it happened, or that it was going to renegage smoothly, When side slipping, I was in full confident control and that is not a feature of my regular fin set up on my backhandm ut is predictable but when it reengages I can fall backwards if not anticipating that. When the WG2 fin got traction again the accelleration began again smoothly.

One one tiny right I tried to make a section way infront of me just to se if I could. I set the line in full trim and it just held speed across such a flat section there didn’t even seem to be a wave, then as I approached the section started accellerating again and I was in disbelief that I connected it and was still going.

I think this fin is really suited to traditional style longboarding, but every time I’ve wanted to ride the roof and land a floater it allowed that too.

At one point I saw two dolphins surface and dive slowly in perfect unison, one just in front of the other. They had some lighter grey on the base of both dorsal fins with darker tips, kind of a different than usual shape more triangular. I kept looking in the direction they were swimming to make sure they were dolphin and never saw them surface Again. I got spooked and took a wave in.

After wave fizzled, i did the prone thing, cutting as steep as I could to the left to get closer to the trail. Can notice it here too. harder angle can be maintained with more forward speed. When it gets really shallow I sink one rail just so fin does not cut as deep and possibly hit the odd piece of reef at low tide. Often the board loses all forwrd drive and whatewater pushes me to beach. The WG 2 kept going for longer.

Then I started to make some dust and drew up some shortboard size fin templates. not sure how flexible I want the SB fins. I can run the tight Cedar grain up and down for stiffer or fore and aft for flexier.

I managed to fix the wobbling problem of the WG2 fin by filing off 0.5mm on the plate side of the screw hole. Now it’s 12.5mm instead of 13mm thick, and flatter. No longer need any zip-ties under the fin to stabilise it, it’s fine with just the screw and plate now.

I think I would need to file off 1 to 2 mm off the underside flat where plate resides, before fin base would be touching the bottom of the box. Then the center of the box is still loose enough for 2 layers of blue masking tape on each side.
I don’t know If it is wise to file 1 to 2mm, perhaps more, from the polycarbonate fin tab’s underside just so it fits better. Perhaps if it were mine I would, but it will goto someone else at some point.

Right now the WG2 is 1/2" forward of dead center in my bigger longboard, with a zip tie underneath, and the blue masking tape being spit up from the sides of the front of the fin.

I’ve gotten a few more surfs on it. Still really like it, but I have still having difficulties transitioning out of my harder frontside bottom turns. It feels very unpredictable when the fin gets loaded hard with the tail sunk deeply, then unloaded quickly. Sometimes there is a squirt, other times just a slow
squishy centering feel and trying then trying to reset the rail after somethingunexpected happens, and several times just falling on the board so as to not lose it as I rarley use a leash lonboarding
The ability of this fin to allow a quick pivot to throw the nose up on top of a folding section of white water, then coming over with it and accellerating out of it is a very unique feeling. It is just that initial hard frontside bottom turn exit transition which is causing me issues.

I did drag around some seaweed when paddling at one point. It was obvious when i hooked it and started draggin it.

Carbon tubes and rods in various sizes have arrived and only a small adjustment to one of the holes is needed. The test fin without winglets printed quite well on the second attempt, using bioFila Sun filament. But at 32.5hrs print time it will take a while before I get around to print another one. Maybe on the weekend I’ll print the tubercled version, now that I know the holes for the tubes are correct. This material (and the way to print it) is much more expensive than the standard PLA, but I hope it needs no filling with resin and it will be safe to leave in a hot car.
Most sizes of the carbon rods are available as hollow tubes and as solid rods. The solid ones are heavier and stiffer, so it might be possible to adjust flex of a fin by changing the rods.
I’m still tweaking the optimal rod lengths for the tubercle version, before starting to print. It seems the water tightness of the bioFila material might be better than the other filaments I used before. No apparent air leaks when I suck on the fin, the hollow tubes seem to hold vacuum well for a little while (as judged by the tounge stuck to it method).
Maybe some tubes could even be left empty to increase flex further, if needed. If this works out well, then I’ll send a fin to wrcsixeight with a set of different carbon inserts to play with, to find what effect the flex pattern has.


I settled on this distribution pattern for the carbon rods for now. Maximum amount of rods that can be fitted in the fin without getting nearer than 0.9mm to the surface, then some rods shortened to prevent any straight potential predetermined fracture lines.
I think it is probably over-kill wrt strength, but better safe than sorry. One can always remove rods until the fin snaps off, or make a more finely tweaked fin later on if this one surfs well.
The printer is now running to make this fin, with changed settings, so I expect less than 24hr print time. Unless something goes wrong, which it often does…

I had a great time with this fin today!
Got one of the longest waves I ever have, and definitely the longest since I’ve been using the Trace logger over a year ago.
Then, while walking back to the carpark, Cheyne Horan asks me to stop and let him have a look at the fin. He was checking the surf, probably about to go out with a student of his surf school. Cheyne was wondering if the fin came with the board, HAHAHAHA! I was, as usual, surfing a McCoy Nugget, and Geoff is sort of allergic to other fins in his boards. Geoff is always ready to elaborate that the Winged Keel fins by Ben Lexcen and Cheyne Horan do not work well in his boards.
Anyhow, I told Cheyne that I’d only surfed the fin (and the board) a couple of times, but got some of the best waves of my life. And, that the only thing I could say for certain about the fin is that it humms. I said somethinng like " I think I need to sand the trailing edge a bit sharper to stop the humming", and Cheyne replied that it’s usually due to some beading at the trailing edge, and he promptly found a raised ridge along the trailing edge.
So now I can claim that the fin was fined-tuned according to advice from Cheyne Horan! Whoahahaha! ROTFLMAO.
And I got my longest wave on it on the same day.
All I can really say about the fin is that it did not hinder the boards performance. I did get around four slow to very slow sections before the wave reformed, as you can see by the colour gradient in the Trace line. And I did do a few turns, even if the Trace claims that there were no turns on this wave. It did not feel phenomenally different from a Gullwing fin or the Wavegrinder fin, or a Gull-Whale fin.
It was holding well on steeper parts of the wave, pivots well, accelerates nicely in bottom turns. And did not fall out of the box, without being screwed in.
I’ll sand it lot better at the trailing edge and see if that gets rid of the humming.


Cool happenings.

I’ve only a had a few more sessions since last posting on the WG-2 and still have some issues when ending a hard frontside bottom turn I have not yet worked out. A few times on top turns the same weirdness has been observed but the really noticeable factor is it holds, and it is looser and faster, there is just the weirdness when I feel like the fin is really bent over hard, but only on my forehand. Backside I can load the fin with everything I got on a bottom turn, and there are no weird surprises.

My lower back has decided to not play so nice with my desires to not feel pain or make weird faces and noises when trying to stand straight, and this week my Vehicle needed some overdue attention, so I missed a bunch of waves I otherwise would not have.

I am hoping to have my friend, who is a better shortboarder than me but a similar ability longboarder rider try the WG-2 fin for a session or 2, on his Lb and render his opinion. I have a 2 other friends who I feel could give a good ride report on the fin, but they are not members here.

I’ve made little progress on my own Zebrawood WG-2 copy other than cutting it out, or on the cedar/glass panel I made big enough for 5 shortboard fins.

I’m very happy to see you’re having so much fun building fins with finfoil !

Did you tell Cheyne about finfoil and all the cool stories how you 3D printed the fin and the issues you encountered? Or was it just a very short talk?

It was really just one minute. He was keen to get into the water.
I’m not even sure it came across that I made the fin myself. Cheyne and the other guy there (I don’t know who he was) then got distracted by the ‘Nowacs’ and the Trace recorder on the board. And the board itself is nice to look at, too.
The biggest McCoy Nugget available, due to blank restrictions: 8’4’’

In the parking lot, I pulled The WG2 from my bigger LB and put it into my smaller LB. I had to modify my tape which allows it to not wobble so much in the box, and was unable to slide the fin as far back as I wanted leaving it about 7/8" farther forward than the last time I rode it in this board. Rather than fiddle with it I decided to try it a where it stopped.

I rode it at a reef that sometimes makes it feel like one is pullng a sea anchor behind them, and the first wave I knew the fin position was off, like the sweet spot got a lot bigger and a lot duller. Also the ‘drag free’ feeling was kind of absent on many parts of waves where I was expecting to glide effortlessly across a flat section to reach a steeper section. I do not attribute this to the fin location in the box, more so the wave, and my previous expectations of its speedy qualities.

Also this board is not very fast being a gunny pintail with old school soft rails. it was also shorter period windswell with very little grunt.

One impression I got was that the fin in this position in the board, at this wave during turns, liked being turned with the Board flatter in the water, relying more on fin than the rail.

I did really try and replicate that hard frontside bottom turn to unweighting weirdness I notice on my other board several times, but other than feeling the fin flexing a lot, it did not cause the board to buck or resist the resetting of the rail afterwards like on my other board at the different reef.

This fin in this board is likely an inch or more deeper than it needs to be. Such a thin narrow pintail does not need this much fin, although the WG2 total fin area is significantly less than my usual fin combo on this board. The wood wg2 I make for this board will only be 8.25 deep instead of the wg2s 9.25…

A few people on the beach commented on the weirdness of the fin, thinking the winglets were for a foil type of lift to keep tail higher as opposed to capturing tip vortices to increase hold/ reduce drag.

I had a few turns initialted slower and flatter, frontside and backside where I only started pushing hard after fin was loaded and redirection already fully underway, and the accelleration back to the pocket was rather profound. A very unique and unexpected feeling, that kind of made me think of a pilot banking a plane on its side, then slamming on the afterburner. Twice I got way too far out in the flats to continue the wave smoothly. It seems once one gets this fin set and loaded and is reapproaching the pocket, it just wants to hold that line and accellerate.

I do really like this fin, in the two boards I have tried it in, for my more traditional style of longboarding. Not sure how much of that is Novelty of such a different feel, nor how this fin design will translate into multifinned applications. My 6’8" speed egg has a FU box I am thinking of trying it in as a sidebitless single when it gets chest high +.
I also have another 9’6" old school board that i can try it in. That 9’6" board initially was very unimpressive with the fin I initally used in it, which in retrospect was an ugly outline and poorly foiled, being one of tmy first, but a thicker more upright fin changed that impression greatly and go got one of the best barrels I ever got on a longboard, on the west coast at least.

I really want to try this fin in more conditions/ boards. Novelty or not it is a unique feeling that is kindling a bit of stoke.

Time for some more testing.

Thank you for your detailed ride reports, much appreciated!

Appreciate the opportunity to test drive this fin. Thank you.

Conditions just now were similar to yesterday, with a touch more size and grunt and consistency with less chop, and I surfed the same stretch with a few more people, but overall not more than 10 today, and 4 yesterday. Most were on mushy wave fishy type shortboards waiting further out for the larger sets, and I was mostly hangin further in in to get the inbetweeners, when it was not my turn at the peak. Rides were long so I spent much time away from the pack with a high wave count, most of which would have been unridden.

Very much liked the fin moved further back, and it could go back another 7/8", which I need to try as well.

I am questioning the flex of the fin more and more, whether it is excessive or part of the reason I like it as much as I do. While not feeling too big, I also felt again that it really is more fin than needed in this smaller longboard, and am wondering if going even smaller than 8.25 deep is warranted on the one I plan to make for even less drag.

This smaller LB sometimes will get stuck in a track and that is really no different with this fin and the times I screwed up the wave were more bad surfing than any fault of board or fin but there was some unexpectedness which definitely contributed.

There were a few times again today where I expected the extra speed this fin seems to allow, but without the hoped for result, but this particular wave seems to do that occassionally on every board Ive ridden there. I tried to get a better longboarder than myself to give it a go, but he was on a sub 6’ board which would have issues floating me, and I was kind of done near that point.

I had two forehand waves where I did the late swing, sink tail and single paddle take off into stalled, waiting for the wave to throw then buried an arm to slow and leverage/pivot and the fin did break loose, but in a very predictable manner and reengaged quickly when I wanted it to, and is very noticeable in comparison to the fin I usually use in this board.

My last wave was a runner I caught on the paddle back out, that I had to straighten and prone out on. I kept the rail buried to make some distance down the beach and am again surprised at the steep angle, and how far I can get up on the 9’3" in the prone position, without the fin busting loose.

In considering my reports on ths fin, This smaller Lboard weighs at least 18.5lbs and I’ve yet to wear a leash using this fin. The last two days would have likely had consequences to fiberglass had I lost it, so there was a bit of holding back in regards to finishng the wave with a lip bash or floater, and some of the late ‘possible’ drops were not taken.

My bigger longboard weighs ~25lbs and has not had a leash attached since late 2014.

BOth boards have a speed governer in third gear at about 7500 rpm due to rocker and soft tail. No fourth gear. Overall this fin is noticeably faster upto ~6500 rpm, but I do not yet know if that redline has been pushed up past 7500. Need more wave to know.