There are many interpretations possible when doing biomimicry designs. As a side project I am modeling a series of ocean animals inspired fins (thanks for bringing penguins to my attention btw), while trying to stay as close to reality as possible. I'll only allow myself to smooth the planshape to remove particularities that are variants among different specimens and design a better foil while respecting the original thickness. This is not a project to do revolutionary fins, but just to play with sticking various animal flippers and wings under your board. Plus it's pretty and a good study exercise.
I chose another picture (there's so much variations between species and individuals) and designed a thruster set. Went for the 7" depth suggested by wrc68, which gives a base of just above 3". Made two 18% foils, one symmetric and one cambered, that looks really thick on a fin but I let nature do the design for this project. Curved the side fins just a bit (about 1/2" from straight line), 7 degrees cant, and added some twist toward the tip. The leading edge has 3 degrees less AoA toward the tip, meaning less lift, less tip vortex and somewhat delayed stall.
PS: wrc68, if you gave some thoughts to the tuberced (curved?) thruster set you wanted we could start designing it. I didn't get G10 yet, being carefull with money because of the lockdown and delayed payments from clients until India's borders open again.
We Are One
Those look pretty sweet. Very close to what I was trying to draw on cardboard. I was looking more for a obvious break in leading edge outline half way up with a super subtle tubercle.
I was going to look for different breeds of penguins online, see what i could find, see if I could get my printer to work and get something printed up in the 6.5 to 7 inch deep range. I lost my round tuit though.
I very much like the idea of the rail fin tip having 3 degrees less AOA. I've an acquintenance who rides some fins with that feature, and swears by them.
Regarding tubercled thrusters fins. I do not really know where to start. The 50/50 gwhale fins cut to 4.5ish inches deep, are too weird as rail fins, and are my only experience trying tubercled rail fins, and they were so love/hate, the few surfs I tried them in.
I want very High aspect ratio but 'some' raked tip area, allowed to flex slightly.
I also am fretting more and more about big old tubercles catching and not releasing the leash, not only when getting into waves, but when actually falling losing the board and using the leash, I think the leash will be able to rip fin/ finplug out of the board. Leash shedding ability is becoming more of a consideration for my shortboards.
On my LB I have never used a leash with a tubercled fin so it was never an issue, but on either SB or LB, I have a tendency to paddle deep as I can at oncoming wave, sit and swing the tail into wave, and do the buoyancy assisted take offs, and the leash is very obstinate about getting wrapped around the tubercled thruster fin doing this.
Not sure the whole leading edge 'needs' tubercles either, perhaps just closer to the base, or if all three thruster fins need them.
Man I feel like I missed something. When did whales turn into peguins? Just kidding, WAO and WRC you guys are like a couple of mad scientist. Let me know when you two start a fin company. I'll be the first to invest!
I spent my free time this week making this fin. This is just a sneak peek and not finished so don't be too harsh. It's also meant to be a show piece more than anything.
MrMik and WAO are the scientists, I'm just mad.
One also has to consider that penguins will not fall onto the pointy end of their wings.
But surfers will occasionally fall onto their board's fins, and they use leashes.
The Dea-Weeder fin was my first attempt to make a tubercled fin that does not catch a leash or seaweed. It's tip is too pointy for safety though, maybe it can be rounded without causing issues.
The G-Whale and Albatross-Whale fins are rounded everywhere.
I wonder if a fin with smooth leading edge, but undulating surfaces would have some of the attributes of tubercled fins, but without the leash catching effects.
I really need to glue the carbon bars into the G-Whale fin that has WAO's smooth surface structure and find out if it surfs much different from the one with finFoil-generated undulations.
I could try to overlay a tubercled fin with a finFoil-undulating tubercled fin so that there are no actual serrations at the leading edge, but the Gullwhale fin without tubercles also catches the leash, albeit half as often.
The deaweeder is a good fin, its just not as quick or loose or forgiving as the GWhale.
It's way better than my regular dol-fin while feeling similar during turns with that forced longer turning radius, while being quicker too.
The Deaweeder cut in half with a probox base is my current favorite thruster center fin, and part of that is it will not catch and hold my leash on the swing late buoyancy assisted takeoff, but it also feels like it has more squirt/projection on the bottom turn than the top half of the Gwhale. It's not as loose but that's not a factor with my HAR 'sharky' rail fins with their extreme pivoty tendencies. It's also not as fast when on open face with good speed already, and able to pump for even more speed. The 0.5 Gwhale fin in such a situation with the sharky rail fins, make my board a freaking rocket. My issues are just getting enough speed in weaker conditions to where the board and fins come alive.
Breaking my 'minimum chest high' before shortboarding rule has been enlightening, and frustrating.
I finally got some good waves on my lumpy spitfire fin. It is significantly different than anything I've surf so far. It will definitely take some getting used to. I had it in a 9' x 24" x 4" longboard that is my daily for smallish days. Surfed diamond head cliffs and it was shoulder high sets, kinda windy, but great day overall. The good news is it's fast and trims awesomely. Just pick a line and you go. The bad news, it's seems to be unturnable when it gets going. It seemed to be impossible to break the line once it got going. I think I can move it back further in the box to try and loosen it up.
On the note of boxes, just curious if anyone has connected 2 bahne boxes together in a line for a super long box? It was a random thought I had as I was looking at my fin placement.
As far as biomimicary, I was thinking about either a quad or twin set of sea turtle keels using the turtles back flippers. I added a picture.
I dont see it as being easy to sink the rail of a 24 inch wide, 4 inch thick edged 9 footer at speed to turn, regardless of the fin used, but a low drag high aspect ratio fin will not slow down the board as quickly when initiating a turn, or through a turn, compared to standard fins. The standard raked fin adds a lot of confidence through turns, much like having more effective brakes do when approaching an intersection/hairpin turn at too high a speed.
The WaveGrinder WG2 felt like it was tracky to me. The faster one was going, the more the fin would dictate when and where and how hard one could turn. With the Fin being much less draggy, the extra speed was even more hard to deal with, and I'd have to begin the turn and wait longer than normal before I could really engage the rail and then push progressively harder, and then once engaged and turning down the face unexpected accelleration would begin again and a locked in tracky feel would resume.
The tubercled harftub fins with teh same aspect ratio, were devoid of this tracky tendency, but not as quick either, and the first Gwhale felt as fast or faster than the WG2 for ~85% of the wave.
I've not ridden the WG2 since, even in the weakest of conditions where it was previously the obvious choice. MrMik also sent a PLA WG2 clone, and I broke the winglet and replaced it with a hardwood winglet, designed to 'dig' a bit less than the original, and this one was even faster. Later on I saw it is slightly higher aspect ratio too. I am not sure that the different winglet angle or the higher aspect ratio or the being stiffer factor made it obviously faster, especially midface or lower but I do believe the winglet angle's in relation to the tail rocker is paramount to where on the wave face it works best.
Generally moving the fin back is not going to loosen up the board, make it easier to turn, unless your back foot is on the deck directly atop the fin or behind it, which is unlikely on a 9 foot squaretail 4 inch thick longboard at speed. Moving it up in the box should also move the sweet spot up slightly and make it somewhat more controllable at speed.
You are likely going to have to get your front foot closer to the rail to turn it at speed on such a board with such a low drag fin or really stomp on the tail to sink it and slow down first. more back foot pressure batman.
I put mild consideration into extending/doubling a singlefin box on my first HWS, but then decided I would just locate it for a single fin and the thruster fin could hang off the end of the box as much as required. I actually still put it a bit farther back than required, as I wound up liking it best with the thruster fin moved abnormally forward. but I never wedged the single fin all the way forward either.
The boxes do not flex very well with the tail, I'd not want to join two, even if the joint was heavily reinforced.
I'm not the best surfer by any stretch. So that doesn't help things. The monster that is my longboard desperately needs to go on a diet and will probably get reshaped once it has enough dings and dents. It's still pretty new looking though.
The fin I had been using was a "high aspect ratio" version of a standard fin mostly foiled by hand and what felt right. It had similar problems when I first rode it, but nowhere near the speed. I shoved it all the way back in the box and it was a lot more manageable. I'll try shoving the lumpy spitfire forward next chance I get. Scratch that I want to give it another go in decent surf before I start changing variables. I also have a 7' 4" that I plan on trying it in one of these days.
I'm going to have to look back through Mr. Mik's thread because I don't remember which fin the WG2 was.
I've tried both the fcs1 wingletted offerings 5.7 deep and 4.8" deep. The smaller one was OK in thruster position, still had that locked in tracky feel.
The Winglets really need to align with tail rocker and wave and riders style
When dialing in the harftubs, gwhale fins, I was bringing a screwdriver/ fin key out with me and when the board felt too loose move fin back slightly, too slow to respond to input, move it forward. Found the thinner version of the Gwhale liked to be farther forward than the fatter version.
The ball spring plungers allowed for easy movement, but my worn/stretched fin boxes would eject it way too easily.