McCoy Gullwing fins are special case of high aspect ratio BLEF fins, with a single bump. That's why they work so well and are so forgiving, and that's probably one of the reasons why Geoff insists that a single fin board outperforms multi-finned boards for most surfers in most conditions.
I have no reason to doubt Geoff McCoys judgement on boards and fins, I surf only McCoys because surfing something else usually results in a wasted session. And I found my sweet spot for single fin Nugget size at the top end of the Nugget size range. I have a few between 7'11 and 8'4'', each a bit different from each other and designed for different scenarios, while being so similar to each other that I do not have any problems adjusting between them.
I tried a Cheyne Horan / Ben Lexcen winged keel a couple of times, and I did feel a difference, an unexpected squirt of acceleration at times, but it simply made surfing harder because that needs extra effort to control. But other than that, I've stuck with McCoy Gullwing fins in McCoy boards.
When I came across Roy Stewarts BLEF fins a few years ago, I made a drawing of a tubercled Gullwing fin and asked him if he could make me one. I named them Gull-Whale fin and sent Roy a snap in Gullwing fin so he had a good template to work from. Roy designed some bumps onto the Gullwing fin and had it printed on an industrial 3D printer using polycarbonate.
Unfortunately Roy and Geoff did not get along with each other, surprise, surprise.
I could never quite convince myself that the Gull-Whale fin outperformed the Gullwing fins, but I used them almost exclusively, because they were so light and were certainly no worse than standard fibreglass Gullwing fins. Roy claims the Gull-Whale fins are a good deal better than the original McCoy Gullwing version, and he is probably right. Better foil, more consistent than hand foiled fins for starters, and then there's the bumps. But, they tend to snap off eventually.
McCoy Gullwing fins are now also machine foiled and accordingly very consistent.
Back to the flash of insight about McCoy Gullwing fins being single-tubercle high aspect ratio fins: Particularly the Straight Tip Gullwing fin, see screenshot below:
I'm spoiled, I surf McCoy Nuggets with Gullwing fins, and I prefer the 'straight tip' variety all the way forward in the box, unless the waves are large (3-4m faces is my max so far), and then I prefer the standard Gullwing fin in the recommended position, i.e. trailing edge 18.5cm from the tail, not quite at the aft end of the box. I might put the Standard Gullwing fin at the very end of the box when I surf waves sized at the very upper edge of what I can handle. Once I did use the 'Extended tip Gullwing fin' in my 7'11'' Nugget (specifically designed for large waves instead of a 'Gun'), and I did not like it much, it felt a bit hard to turn. But I don't get to surf waves that big often enough, the feeling of 'hard to turn' might just have been the g-forces involved at high speed, because I logged my personal fastest surfing speed that day, 45.5km/h. It could have been because of the extra drive supposed to be provided by the extended tip fin, too.
Screenshot taken from McCoy website: http://www.mccoysurfboards.com/mccoy-fins
I rode MrMik's printed version of the WG2 yesterday after getting it to fit nicely in my larger wood longboard the evening before. It took some time with a reduced speed belt sander 50 grit, a razor and 220 and 320 wet paper abrading until it fit so the leading tab was not above the level of the fin box and also tapered the trailing edge much closer to the level of the board as well. I am using the roll pin and finplate, although the BSPs would likely retain this fin in this board as long as until there is an impact from front or rear. I am not that trusting yet, but this fin in this board is a mucvh better fit than the harftub9/blef in the guppy.
It is stiffer, slightly heavier with a different foil and some differences in the base shape and has the base to tip striations as surface texture.
Here is a copy and paste from the PM I sent him.
"I rode the wg2 copy in the bigger board. I have to keep in mind that it has been a long while since I rode this board. In between I was riding the 'without magic' 9'6" board , and mostly the guppy.
The waves were about waist high at best, NW wind swell and some very seldom Southern Hemi sets, and occassionally the combo set which was quite peaky and bowly and perhaps lower rib cage height on the drop. There was a little rip pulling through the middle of the break and my first few waves I was having difficulty keeping the nose up. I've also not surfed in a week or so and the last surf was on the guppy with the harftub9. I was mostly going against the grain going right on the S hemi sets and going left on the shorter period NW wind swell. Crowd was not really a factor.
The fin and board felt stiff, like the fin was certainly too big. The polyC WG2 in this board is noticeably looser. It could also be faster, but for the times I had my line set and was trying to simply maintain momentum to catch up to the next little pocket some ways ahead. When doing this this fin accellerated, tapping into some energy inside the wave I did not know existed. I likely was able to get more speed on such a small gutless section of wave, than ever before.
At these undeserved speeds, the fin felt absolutely locked like it would resist any instant input for a direction change. It was both exhilirating and scary, scary as the water was so shallow that going that fast would not leave much room for penetration, and on the inside on the rights, there is some possible exposed 'reef' to make a mess of whatever gets put down first.
Turning, it felt sluggish and more like a traditional raked fin in the slow comearound. On a few lefts I got that weirdness that the WG2 had only on the rights after ending a bottom turn, Like the fin was loaded and I was trying to disengage the rail and the board bucked, and it was either fall off or fall on the board. I opted for the latter and most times was able to maintain direction and regain my feet.
While I thought the WG2 and the harftub9 were extremely pivotal with harfy9 having a serious edge, this felt lacking in todays waves with the wg2 copy.
The fin felt large, and stiff. I am actually surprised it felt so different being the same overall size.
While feeling stiff and too large, (is that a 'that's what she said' joke or what') it was still looser and faster than my traditional raked fin set up with or without inline trailer.
While I liked the fin, the original WG2 felt faster and looser in this board. It really could have been the waves, my lack of surfing for a week or so, and remnant memories of the HArfy9 fin in the smaller lighter longboard which was just so loose and predictable and confidence inspiring."
The main two test vehicles business ends are below. I've not actually used the PU/PE cedar epoxy hybrid( guppy) with the trailer wavegrinder fin which is part of a quad set that another swaylocks member mailed to me for testing.
23 hours after that session my impressions of how it felt are largely the same. It felt like a much bigger fin than it is and closer to my regular raked fin inline combo, during turns. When milking tiny waves trying to connect to a impending section of open face to form a ways ahead, NO fin has really come close to matching the straight line energy milking ability of this fin on this board or pretty much any longboard I've ever ridden, but perhaps some very flat 60's bings and ricks. I seriously have never gone so fast on such a tiny wave over such shallow water and was genuinely fearful of falling awkwardly and just hoping for an safe exit. Most of th etimes I tried to reach that way down the beach impending section and arrived at open face in full trim and the accelleration there was also surprising, but only very slight corrections could be made to the line taken.
A am still surprised just how different this fin felt compared to the Original Wavegrinder WG2 polycarbonate fin, as the planshape is the same.
When we get some more solid swell in the chest high plus range I will try the stiffer quad Wavegrinder fins in my thruster. My impressions of these are the larger fronts, visually appear to be too deep, and the smaller quad fins appear too small to be the sole rail fins. I had previously drawn a few templates from pictures and got the rake angle wrong. The ones I drew were much more upright.
It seems the fins have been molded to sit slightly above the board. Likely as the fins are dual foiled, the cant cannot be shaped into the hull fin interface. I would have to shave about 1MM from the bottoms of the tabs to get them to sit flush with the hull on the railside ede of the fin. As these are not my fins I will not fine tune them to my board. Tuning these fins to fit absolutely flush with the deck, would likely require shaving 2mm or slightly more from bottoms of tabs and then some off the area inbetween the tabs on the ~6 degree angle. These stiffer quad wavegrinders visually appear to be ABS rather than polycarbonate
How important this zone is to interference drag is an unknown to me, and regarding surface texture, I have no personal comparisons, but my opinion is for smooth being less draggy than rough. The rough printed wg2 copy and the smooth WG2 would be the closest direct comparison, and there is the differences in foil and flex, weight to consider as influencing variables,. along withthe fact that no two waves are the same and 'feelings', are not scientifically quantifiable
Sanding the PLA 3d printed fins requires not generating much heat. Or perhaps sacrificing a belt or piece of sandpaper to melt a section, then simply razor off the melted 'flashing' from edges of fin and then perhaps, sandpaper. Not sure of the correct term for the melted plastic which wraps around the back and sides of the fin when I did get it too hot. I've not wetsanded beyond 320, and this has left the deep rich light gathering blue color of the PLA, with a white haze on the surface.
I'll update this thread when I get the ride report from that one excellent surfer to whom I lent the original WG2fin to, and my own ride reports of it, or MrMiks printed version, I am more interested in riding the turbucle fin/ blef/ harftub9, and the other two fins MrMik sent which should be flying across the pacific as I type. I am also hoping to get on the shortboard with the wavegrinder quad fins and i will report my impressions of those in this thread, but the turbucle fin reports might be in another thread as they only share the high aspect ratio as Wavegrinder fins and nothing else.
When I get the original WG2 back, I will send it forward to the next swaylock member, whomever that might be.