I’ve tried the tether thing and found that the string I used was way too thin. The forces involved when a fin comes out during surfing are enormous and you will probably lose the fin anyway. It might even do damage to board while flapping around on the tether.
What kind of board did you use the GullWhale fin in?
I think I have the fin strength issues sorted, finally.
Of course, fatigue issues due to repeated heavy loading of the fins and effects of salt water exposure need to be assessed over long-term real-world use.
The fore and aft screw plates ends are now so tough that I can hit the fin hard from fore or aft, until either the 3D printed screw plate breaks, or the fin moves in the box, or it simply hurts too much. And that is even after I drilled holes for the set screws on the bottom of the fin tab, and screwed in the grub screws. I was a bit worried about that, but it appears the carbon fibers arranged strategically in the fin and base are doing their job.
The purpose of the grub screws is to allow easy adjustment to different depth fin boxes, so that positive contact between fin tab and bottom of the box is easily achieved without sanding the fin tab. And it can be adjusted for use in other boards, or a different position in the same box. The same Allen key works for the grub screws and the screw plate screws so only one tool is needed.
Some results of using a dual screw plate system were unexpected, but all are most welcome:
The screw plates can serve as safety release mechanism to reduce injury risk and risk of damage to the fin box / board during fore or aft impats to the fin. The severity of an impact required to pull the nut through the printed material can be modified, even by the ‘end user’.
The fin position can be changed easily while in the water. Unfortunately, that will not work with wrcsixeight’s worn boxes. But with a new-ish straight box, the screws can be loosened a little bit and the fin can then be whacked fore or aft to move it. The screws do not lock the fin into the box like the roll-pin + screw plate variety does, therefore the screws do not need to be completely removed before the fin can be moved.
There should be less wear to the fin box, because the fin gets inserted right where it stays. No pushing in of a roll pin and then dragging the fin in the box.
The screw plates can be left in the box when the fin gets removed (even with boxes that have an entry slot at the end of the box).
Insertion of the screw is much easier, because the plate ‘funnels’ the screw toward the thread.
Different colours make the plates easily visible in black or white fin boxes.
The thickness can be adjusted so that the plates move in the groove with a bit of friction, so they don’t fall out, even if you don’t screw the screw back in after fin removal. This can also help to mark the optimal position once it has been found.
Awesome to hear the new base design is as strong as hoped, and I very much like first version of the printed screw plates you sent.
The screw ‘Funnel’ makes threading the screws into the plates much much easier than regular stainless plates, and I have done so with the board in its side, up side down and right side up without the curses I have been prone to emit when doing the same with standard the stainless plates and screws. The super low profile of the head of the screw is aesthetically pleasing, and the fine tuning of the depth of the fin in the box via the grub screws should make it much more universal with less end work on the user’s part requiring no sandpaper and much trial and error to get the tabs flush with the hull for minimum drag.
The Only issue I can forsee with dual screw tabs is for the person wanting the fin to be at the very extreme ranges of the box, and they could saw off the screw tab on that side of the fin, and install a roll pin, but I personally am over the whole roll pin thing as I see ideal, as absolutely Zero Wobble between the base of the fin and the finbox, and achieving this ideal is nearly impossible with the roll pin, especially on a worn/stretched box.
Regarding the location of the fin in the box, I’ve been liking the GW fin, my favorite fin, dead center in my finbox which puts the trailing edge of the fin at 7.5 inches from the tip of my 9’7" x 23 x 3 round pin.
Many months ago MrMik sent me 3 Silpoxy Gullwhale fins, which were printed hollow and stuffed with epoxy saturated spider silk. One was 12mm thick at the base, the others 11 and 10mm.
I snapped the 12mm one the first session kicking the board up ond over a closing out wave on my backhand. Upto that point the fin felt magical. I did not try the 11 or 10 Mm versions as they too would surely snap.
But recently, due to the fact that I love this GW design so much in my longboard, and only having the one original one sent, which suffered structural issues but which i reinforced, I made my own carbon rods, and drilled holes from base of fin up into fin, as deep as 5 &7/8" deep, and inserted 5 of them of unequal lengths into the bases of the 10mm and 11mm silpoxy GW fins.
I installed the 10MM fin in my board, in the usual dead center position of my fin box. I was having issues with it. It felt like it was stiff, like it was resisting and delaying my desires to turn the board, and like I was getting stuck in turns, and off balance often. it felt like the fin was too far back in the box, but it was in the same position I have ridden and loved the 3 other GW fins.
Next session I moved this 10mm Silpoxy GW fin forward 3/4 inches in the box, and it felt magical. Granted I never moved any other GW fin this far forward but never felt the need to as they never before felt stiff, but this 10Mm fin moved forward 3/4 inches, the very first wave i just Knew…, and my confidence in the board with this fin in this location just continued to grow the whole session and I had an absolute blast and left the water giddy despite the crowd whose strategy seemed to be to follow me around as closely as possible. While I cannot say for sure that the thinner fin felt any quicker, at no point did I think it was draggy, and I had a few cutbacks, and one roundhouse cutback on my backhand which simply felt incredible considering it is a 25Lb 9’7" traditional longboard with softrails in the tail.
I was thinking the GW fin thickness sweet spot would ultimately reside in the 13 to 14mm thickness range on my longboard, so this 10MM was a surprise, as was the fact that it felt stiff in the regular location which felt best with the other GW versions, but simply magical moved up 3/4 inches in the box.
I am hoping my homemade carbon rods endure. My primal instincts are to horde these fins and create a shrine to the gullwhale god.
The drill bit I used was 3/16" x 6 inches long, and I had to sand my CF rods down to fit. The carbon rods MrMik employs are ‘pultruded’ and at 5mm diameter and significantly stiffer than my homemede versions, even before I sanded mine down to sub 3/16", from thicker than 5mm.
I have as yet, the 11mm Silpoxy gullwhale fin to try, and the ‘EL Twistolero’ version, but I am going to keep the magic 10MM silpoxy in my board for a while before installing those.
Thank you MrMik for all the fins. These GW fins are making my sessions on my 9’7" significantly more enjoyable in every aspect, and as far as dragging seaweed and kelp, well avoiding paddling through it / going around it, and clearing the fin is simply another skill to be learned, and when i do drag Kelp or grass, it has to be a significant amount before it feels as dull and listless as my traditional raked 9 inch longboard fin.
I have 4 GW fins cut down to size to fit in my Proboxes, with carbon rods reinforcing bases, ready to try in my 6’11’ as a thruster with two different size center fins, when there is a solid chest high+ swell, which I consider the size requirement to get off my 9’7"
I can certainly appreciate the desire to have a fin that snaps as I’ve just had a fin box ripped out of my board from a smack. Any break is annoying (!) but I would rather it was the fin than the board. Thankfully it was the tail end of the trip so only a few days lost.
The Fin-Tune System
I have made good progress in the last couple of months or so:
The first lot of fins shown will likely remain unfilled, because as soon as I had printed them, they became outdated by further improvements to the inner reinforcing structure of the fin. The system for these unfinished fins is rock-solid and a reliable fallback option in case the next, even better version turns out to be yet another flop. It has too many parts, complicating assembly, and is therefore expensive and time consuming.
The newest system is very advanced because it offers variable flex, achieved by a carbon reinforcement system that is adaptable. If that will be a viable solution as an offer to surfers, remains to be seen. It is certainly a great option to test variable flex in the same fin. It also allows to re-use the same carbon parts in a variety of fins, reducing development costs by a fair bit. Post-3D-printing manual handling time is also reduced significantly.
With this method, I managed to make a GullWhale-7-S-75% fin, meaning that the thickness is 75% of the hitherto used mean thickness. It’s quite thin compared to other large single fins, but I can hang my entire body weight on it (close to the base, not the tip!), or hit it hard from fore or aft without breaking the screw plate projections off the fin base. I think the strength is close to what is required to start ripping boxes out of boards, but I might be wrong. In any case, it has to suffer a significant impact before this fin breaks. I have surfed it only once so far, in crowded, hip- to shoulder-high and glassy conditions. I think I heard a whining noise on the first (and biggest) wave during a hard bottom turn, but otherwise I found nothing wrong with the fin. It felt very fast a couple of times, but I really did not get much opportunity to test it, there were just too many people in the water. The whining noise may be due to the carbon reinforcements rattling around a bit, because they are not yet glued in. At this ‘thinness’, the fin feels too flexible in hand, even with the maximum amount of carbon parts inserted. I expect that the fins at the thiner end of the spectrum will require the carbon to be glued in, while the thicker ones might be able to remain ‘adjustable’ by the end user.
Surf testing by wrcsixeight with a GW-7-S-91% Silpoxy fin have been most promising, showing that the speed of paddling and surfing is noticeably increased with a thinner fin. That ‘Silpoxy’ fin build method was already known to be prone to snapping off, so wrcsixeight resorted to manual drilling holes and inserting home-made carbon reinforcements, but it still snapped off eventually, after many good waves. There was apparenly very little or no loss of drive or maneuverability, just a small reduction in forgiveness, when compared to the 100% thickness fin.
I am a follower of Geoff McCoy’s philosophy that surfing is hard enough as it is, and that the equipment used should be as forgiving as possible while still achieving high performance standards. So I will distribute the 100% thickness GullWhale fin version to new test pilots.
However, the lower limits of fin thickness shall be further explored by wrcsixeight. A variety of fins are nearly ready for shipping, including 100%, 90%, 82.5%, 80% and 75% thickness versions.
I hope to get the ‘Fin-Eye’ camera operational soon, I would prefer to surf (or tow-surf) each fin to collect camera footage prior to shipping. That might help enormously with analysis of what does not work well, and why not.
The story of the 3 silpoxy GullWhale fins, one 12mm thick, one 11, one 10mm.
Mr Mik printed these hollow and stuffed them with spider silk saturated with epoxy. When installed in my Hollow longboard, and flexed, they resonate differently than all other fins, and for longer.
I rode the 12mm first at a break I call Invisibles, though that is not the name it is known by. It is so fickle, and when it does break, it can be better than the mainpeak, yet few if anybody ever bothers to move down, as if it is invisible, and I often have it to myself or with one or two other guys at most.
Anyway I had it to myself on such a day, 30 guys out on main peak with boards and bodies flying everywhere, me by myself at invisibles, and the 12mm silpoxy fin was feeling magical, Quick loose lively, and one wave number 12 or 14 or so, I had to straighten out, then bottom turned to kick the board up and over the wave, as I wear no leash, and the fin sheared off cleanly, right at the base, right at the juncture of fin base and finbox.
So I decided there was no point in trying the 10 or 11mm Silpoxy versions as they too would surely snap.
I had other GW fins, one 11mm hybrid version, an another with a red filament which had interlayer adhesion issues that I reinforced with carbon and glassed over. The Hybrid was a solid performer, but did not seem to have the magic flowing feeling that the red GW or the 12mm silpoxy fin had. Eventually it broke from hitting sand, braking the fin tabs off, ( I was able to recover the broken portion) and I was down to only having the red GW fin I trusted and not having a backup was filling me with anxiety, as these fins have made longboarding so much more fun I do not want to ride anything else.
So I got a 1/8" 6 inch long drill bit, and a 3/16 thick one, and drilled into the bases of the 10 and11mm silpoxy fins, Inserting 5 carbonfiber homemade rods at differing depths to bridge the base.
Honestly I’ve been leaning towards thick fins for a while and expected the 10mm fin to solidify this mindset. I recently have made a rail fin for my shortboard that is nearly 12mm thick. I was expecting that experimenting with different thicknesses that somewhere between 12 to 14mm would be the sweetspot with the GW fin.
At first I put the 10mm in the dead center of my finbox, as I had all the other GW fins. The first surf with the 10mm fin it felt very quick paddling, but up and riding felt stiff, like it was having issues coming around, responding to input, like it was too far back in the box. I was frustrated enough that I cut the session short and was ready to write off the 10mm as being too thin, but then decided to give it another go, but move it forward in the box 3/4 inches, and the next session the board and fin combo went unreal.
Simply paddling it was noticeable there was less drag, paddling at a hard angle to get into waves I was out of position for, and paddling south with NW wind chop and up and riding the fin was crisp and very quick. Multiple sessions on subsequent days on it had me loving it more and more. As hard as I could push it it simply held, and projected, and I was rewarded with speed and increasing confidence.
The board and this fin just felt incredible together. Best fin yet I thought after every wave ridden.
But then on my tenth or 11th session, one left, my backhand, I kicked the board up and over and the board flew to the north more than I thought it should have and I saw the fin laying over at 45 degrees. Nooooooooooooo!!!
2 of my homemade carbon bars snapped off cleanly, and the fin broke off at and just under 2 other bars, and the 5th had a large stress crack just above where the bar ended.
So the next day I put in the 11mm SilpoxyGW fin. It too is a wonderful fin, but it does not have the speed, that highly engaged feeling. When it is locked in and I push with everything, I am not rewarded with that same speedy projection. And I can tell when paddling from A to B and paddling into a wave. It is not as slippery. It is displacing more water.
I’ve had 3 sessions on the 11mm Silpoxy now, both with many very fun, and long rides, and I very much like the 11mm, a top 3 fin for sure, it is slightly smoother during turns slightly stiffer, yet more forgiving than the 10mm, but does not have the same reward when pushed as hard and when walking forward to trim, the accelleration of th 10mm is just not there and the max speed for the conditions, seems a bit slower.
Previous to the 10mm snapping I asked MrMik for even thinner versions.
Thicker foiled fins preventing separation of flow at higher angles of attack, makes perfect sense.
Well, something about the high aspect and/or the turbucles of this GW fin design, seems to prevent this occurring, and I think ‘how thin is too thin’ with this fin design needs to be determined. I have one Lacewood traditional shaped fin that went OK, which I snapped and rebuilt significantly thicker, then it went very well had me very firmly in the thicker is better camp.
I’d never considered the displacement of the fin before, just that thicker in a straight line has to present more drag, but whether that drag as noticable at traditional singlefin longboard speeds was the question, in my mind.
The 10MM feeling so much more slippery than the 11mm was unexpected. I was reluctant to actually say for sure the first few sessions, as I did try the AW fin in between, and a different board, but when the much loved 10mm snapped, and the next day I put the 11mm fin in, I knew when paddling out, and the first wave, the 10mm was quicker, crisper, had more torque and horsepower to tap, as well as more glide.
I did not lose the 10mm fin, the PLA only broke on one side. I will cut it down and transform its base to fit Probox or FCS1 with carbon reinforcing rods through the bases. I already have 4 cut down GW fins that I used in my 6’11" and they too feel very good, but one day I was having issues at very slow speeds where it felt like they were not gripping properly. I’ve never liked 50/50 foils as rail fins though and even 70/30 or 80/20s foils seem to lack crisp and positive projection of a flat sided rail fin. I was rather surprised the first 2 sessions with these fins felt so good, as many of he waves I had fun on were thigh high, and usually I do not bust out a shorter board until it is solid chest high or above.
Anyway, I need to give Hans a shout out too. His Finfoil program made it possible for MrMik to design this fin, on which I am having soooo much fun. This fin and its predessors have me questioning so much about traditionally accepted surfboard and fin design. The whole raked tip thing I now see as just drag and resistance to turning. My expectations of how some design tweak would affect the ride and how it did actually affect the ride have at times been at opposite ends of the spectrum.
Gonna go ride the 11mm silpoxy GW now even though I know it too is destined to break the carbon rods. Waves are weak but I know I will have fun. I’m just going to kick out on my backhand with less force as it seems that is when i can shear off a fin the easiest.
Thanks for the detailed reviews, invaluable!
I just want to clarify one thing: I did not use ‘spider silk’, although that would be extra-cool!
It’s just ‘mulberry silk’ from incorrectly named ‘silkworms’, which are the grubs of a domesticated flightless moth which eats mulberry leaves.
Wrong thread.
I think I have finally nailed it regarding a feasible production method that is not too time consuming, but produces a strong fin.
The latest fin is 87.5% in thickness compared to the previously used (100%) thickness, but much stiffer and much stronger.
Compared to the super-thin 75% thickness fin, this new 87.5% thickness fin has 66% more carbon reinforcements in the base.
I have also refined the filament choices used to 3D print the fins, so that flex and toughness are concentrated where needed, and cheaper filament is used where possible to keep costs more reasonable. The trailing edge and the fore and aft screw plate projections are printed from much more expensive material.
Screw plates and edge protectors have been further improved, the cable-tie is now integrated into the trailing edge cover so it does not get lost.
It’s taken 27 months, a lot longer than I thought, but I think I have now achieved what I set out to do in July 2017:
“I’m going for the holy grail of making a complex shape centre fin so that it can be accurately reproduced with high strength, low weight, and minimal waste of materials. Maybe even good looks…”
So maybe I’ll manage to get something else done now, like surfing more!
Its about bloody time : ) well done
Quite the journey! Interesting to follow and very impressive!
Love the cover - such a good idea.
Agreed 
I’ve now towed my underwater camera behind 6 different fins on my 9’7" traditional longboard, and the other day decided to use my traditional raked fin that I used in it for the first 14 years of riding this board.
It felt SO draggy, and slow, in some of the larger conditions I have towed the camera behind any fin in, although it did feel solid and stable through turns, but I was also entering and exiting those turns at a noticeably slower speed than all the other fins used. It was such a bummer when I saw a beautiful shoulder lining up, and then peeling off without me, knowing that the Harftubs, Deaweeder, or Gullwhale fins would have allowed me to easily acquire the speed to stay in the pocket.
The video footage shows a markedly increased presence visible tip vortex compared to other fins, but not as much as I expected to see.
The draggy feel just paddling from A to B, and paddling into waves, was at least 20% more pronounced than the other fins towing the camera. It necesitated an extra paddle or 3 to ensure I was properly into the wave.
Some portions of some waves using MrMik’s fins, I was fearful the camera attachment ripped off the fin, as I could not feel it back there, but with the traditional fin that draggy feel was always there.
I am basically Never riding the traditional fin in my LB, ever again.
This G-Whale-7-SL fin is ready for surfing less than 24hrs after the 3D printer started to make it.
I sent a fin just like it (but different colours and logo’s) to wrcsixeight today and could not stand the thought of not having one ready for when I get to surf next.
Making slight changes to depth, thickness or chord length would only add a couple of hours or so to the production time.
Hans, if you think this fin might be suitable for wind-surfing, or if you surf single fins, I’d be pleased to send you one as a thank you for your fabulous finFoil program! Without finFoil, this would have been impossible.
Thank you!
Thanks Mik!
I’d be excited to try it on my longboard (without sail).
You think they’re strong enough for windsurf boards? Think about 40-80kg force at the outline’s centre of gravity.
I do not have windsurf boards with US box anymore, but I can fit it in an adapter after some drilling.
I’ll send you an email.
Oooops…something went wrong…
These covers are handy to keep the fin happy in any chaotic backpack or van, as long as the temperature stays below 50C.
Designed to be courier-resistant, but that is a tough gig.
The sides of the fin are still exposed a bit, but they would be much more easily repairable than the leading edge or trailing edge.
I hope to avoid all one-way packaging except for the minimum demanded by the courier or post office.
The shipping container is the storage container, and the tool box, and the spare parts box.
Nothing to throw away except for the postage bag itself.
The photos show an outdated version, as usual, it’s after all several hours old!
I think there is space left for a piece of diamond-studded nail file, instead of sand paper.
Biggest problem: Some people will cut the cable tie before engaging their brain…but it is an integral part of the design and will likely last for many years.
