I’m curious what is the design intent behind the “comb” looking fin?
Also, how does it feel when surfing? It looks like it would create too much drag.
The tubercles are biomimicry of Humpback Whale pectoral fins. Scientific study has shown these features to create less drag and allow for higher angle of attack before stalling.
I can’t say for sure what it feels like to surf yet, but Mr. Mik and WRC68 spent a long time testing them a while back. It’s all pretty well documented here (3D printing large surfboard fins - General Discussion - SWAYLOCKS) if you have time to read it.
I have heard something along the same lines of this but in comparison, humpback whales travel relatively slow compared to their size(on the order of 10+mph), versus a human surfing at 15 to 25 mph.
I read a lot of MR MLK’s posts but I didn’t see a lot of actual test results from surfing. (I only read through 14 of the 35 pages of his thread)
Also I think that this fin design would only hold usefull for a single fin and not the side fins for either a twinny, thruster or quad. (Only my opinion, but I may be wrong)
One design aspect that I do agree with is the high aspect design. I have made a high aspect ratio center trailer fin for a little twinny fish that I regurlarly surf and it feels amazing. Creates just enough hold with minimal drag .
Reynolds Numbers (an equation used in engineering to predict/compare fluid flow) comparably for the Humpback whale size and speed, and surfboard size and speed, should be close enough for similar effects, and benefits to be realised.
In theory all surfboard fins would profit from such a design feature, but the effects would most easily be felt on larger single fins.
The G-Whale-7-FRR OS design is now published toward the current end of that long thread. So anyone can make one if s/he wishes.
I can now pop one out and have it ready to surf in less than 24hrs. Can also make them thinner or thicker or shorter or longer.
The fin shown on the printer above is an attempt to make a nice complex pattern without using more than necessary of the more expensive filament and without sacrificing strength. The print head clogged after many hours of repeated manual filament changes about 90% into the print. I managed to partially dis-assemble the hotend and used a thin carbon rod to get it going again, without a layer shift!
I think one of the main effects of the tubercles is that the stall is forgiving. A straight high aspect ratio fin has an even better lift to drag ratio, but will stall in an instant without any chance of recovery.
Due to the different chord lengths between tubercles and valleys, stalling will occur gradually. Stalling also occurs later, at a higher AOA but I don’t know why.
I imagine the fin stalls either at the tubercles or the valleys first, don’t know which. I may be completely wrong about the mechanism.
I love the MrMik’s Gwhale fin tuburcle fin in my traditional longboard.
Never going back.
I’ve not yet ridden in in my 6’8" double bump round pin. He has happy test pilots in quality waves on performance singlefins.
I have cut down broken G-whale fins to ~4.5 inches deep, from before MrMik redesigned the base for maximum carbon bars and made it ridiculously strong and reliable. I have ridden these as rail fins and center fin, but they are 50/50 foil. Sometimes they felt great, other times, at slower speeds, drifty and imprecise.
I keep riding them as center thruster fins.
They need to be further back on the tail. Way too loose if they are stuck in the same location as a raked fin
They can catch ones leash when paddling at the peak to get as deep as possible, sit… spin buoyancy assisted take off, until one gets used to counteracting that possibility.
It’s loose and fast. But still plenty of thruster feel, not a twinny with stabilizer feel. Its definitely does not feel draggy, ever, unless it is dragging the leash.
I dont have any fcs2 boards, but I modified a broken Gwhale fin to fit fcs2. Worried that 90% of lateral load on rear fcs2 tab would break the fcs2 plug, the test pilot rode it in a board he hated, and did not care about if it broke the finplug. It did not in the few sessions he had on it. He said the fin was fast and loose and ‘weird’. Could not elaborate on ‘weird’ and stressed he hates the board. He still has the fin. I’m hoping he gets a new fcs2 board and gets to feel it out more, soon, but life is in the way.
I dont have any Futures boards, but I modified a Gwhale fin to fit the center box. It is a bit less deep than the one I made for FCS2. I messed up the trailing edge where it overhangs the box, but should be good enough to test. I have No test Pilot for it.
The purple fin in my board is a modified version of MrMik’s A-whale fin. Its a good 1/2 inch deeper than the 0.5 Gwhale fins I’ve been using here. I just moved its (probox) tab forward ~15/16 inches, and only surfed this super high aspect ratio deep thruster combo once, in mediocre conditions. It did not suck. Very much looking forward to trying it in better quality.
WAO’s got some very impressive looking curved CNC’s turbucle rail fins made from Padauk, that make me drool. Hopefully he posts them in this thread.
Had the machine cut these out this morning. I think the wood is oak, I’m not sure it was unlabeled in my scrap bin. Total time cutting was approximately 30 minutes a side. I may start doing two finishing passes one horizontal and one vertical to leave an even smoother surface finish. The base also looks weird because it broke out before it cut all the way through. It just needs to be sanded and trued up. Also tossed a whale engraving on it for fun. I can see how Mr. Mik ended up with a ton of fins. Its difficult to keep myself from tinkering with the processes to try and get a better end product, every test ends up with a mostly good fin.
Drool is the best form of compliment 
wrcsixeight I am busy right now with work and the board, but when it is finished I will make a set of quads dedicated to this board. I could machine some fins for you at the same time, but it could be in a couple of months. I don’t want to send you something that is goint to break, so either I will have gotten hold of some G10 by that time or may be you could reinforce the bases yourself with glass cloth. If you are using the proboxes the big tab is strong already and with some glass it would last for a longtime.
Also I’d rather design some fins specifically for one of your boards. With all the fins from MrMik that you tested you must be the guy that has riden the most tubercled fins on the planet ! So you must have an idea of which work for you and your boards. I mean in terms of number and depth of the bumps. We could start from there. Also I would like to use a chord length at the base and a depth that you like already. We could try adding tubelcles on your shark template and curve them as well. Lots of possibilities. And lastly you would have to choose which board you want them for so that I can design them according to the toe-in angle of your boxes and tail rocker.
There’s time to think about it, just throwing ideas.
Amazing offer! I’d love to try some deep tubercled rail fins in my 6’11". My 6’8" uses fcs1 plugs and now is really only used if the 6’11" is in drydock.
The only ones I’ve tried as rail fins were the 50/50 foils that I modified from the top half of MrMik’s Gwhale fin. I was thinking of modifying a few, more making them deeper, with the tabs farther forward and trying them again as rail fins.
I’ve modified fcs1 fins with carbon bars in between the tabs for probox, but these fins basically do not flex, have a 70/30 ish foil, with too sharp a leading edge, did not impress me the one surf I had on them post modification, and I’ve lost interest in such templates:
Hey, thats a sperm Whale, not a humpback! The Former has no tubercles on its pectoral fins.
Kidding, Looking good. Perhaps that is White ash or maple, but does not look like oak to me.
You gonna glass it? The first Gwhale fin MrMik sent me, when i tried it and was Like HO Leee F!!, it was printed from really rotationally flexible filament which had interlayer adhesion issues. When these layers separated, and with no backup Gwhale fin, I dremelled grooves in it across the layers, inlaid carbon fiber and glassed over it with some 1.43oz cloth. I was worried I screwed it up, but it was still magic.
I like the Whale!
Either you are a much more nifty CAD designer than myself, or you added it manually.
How did you do it?
I’ll have to ask my wife about the wood. It was one of her cut offs.
The whale was the first picture I found on Google that looked some what like a humpback and not too cartoony. I do wish I had done it a little differently, but it came out ok.
I actually don’t plan on fully glassing them. Earlier tonight I painted on a couple layers of resin with no glass. I figured it should be strong enough and waterproof enough to test. If it goes well and I like it, I have some nicely figured wood I can use to make an awesome one. Until then working out the kinks in my process.
Grabbed a picture off of Google. Isolated the black outline and converted it to a vector. Used the vector to generate a tool path for the router with a V-bit. It’s all done in aspire which is the cam I’ve been using. It even has an option that compensates for the surface of your 3D model.
I have a few minor bugs to fix with the tool paths, but when I do I’ll make you a nice one with the whale on one side and “Gullwhale by Mr. Mik” on the other. It will be your signature fin, just like the pros.
Wow, indeed much more nifty than my ruimentary OpenScad skills! I was wondering how you could tell a tool to follow the undulating surface to cut the whale, butobviously there is a way!
Haha, I really wish I had a better answer, but it is literally a check in a box. The software does the rest.
Nope, there is a better one!
Here is what I wrote yesterday in response to a private enquiry:
Finally “finished” with this batch. Hopefully get to test them in some surf this weekend. I found out the solid wood one is cherry.
Looks great!
I think you will find it very tricky to get the flanged fins to fit, using the bases you put on them.
A fraction of a mm position difference for the roll pin and it will not work as intended.
Will be interesting to see if wood is strong enough. The weak points are the fore screw extension and possibility for the whole fin snapping off where it leaves the box.
I would use M3 stainless steel bolts and nuts, to leave more wood on each side of the screw, and make custom plates. And use 2 plates instead of 1.
If you add an aft screw and M4 grub screws to the bottom, then you get a perfect fit of the flange on the box.
Okay