How much drag does a fin contribute to overall surfboard drag?
Is a 5%-8% reduction of the fin-drag component significant to overall performance relative to the average surfer?
Can fin performance be adjusted more simply/effectively with overall fin plan shape, foil profile, sweep angle and flex?
If the above mentioned ‘Back to the future’ drag reduction COULD be implemented in a fin, then it would of course be applied to the entire surfboard. And it would / will be a surf-foil.
Anyway, I better stop giving a running commentary while I read. But I am so enamoured with how applicable it is to fin designs, and what a good crash-course through the relevant sciences, so here is another quote from
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EFFECT OF LEADING EDGE TUBERCLES ON
AIRFOIL PERFORMANCE
By
Kristy Lee Hansen
https://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwji19LX8LvVAhUFFpQKHaCLB7IQFggoMAA&url=https%3A%2F%2Fdigital.library.adelaide.edu.au%2Fdspace%2Fbitstream%2F2440%2F79211%2F8%2F02whole.pdf&usg=AFQjCNG8wevJcNr2BSWqaFfMU8Xl9v2x0A
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“Some of the devices discussed in Sections 1.6 and 1.7 were originally motivated by
biological observations, indicating that despite the differences between vehicle and
animal propulsion there are various adaptations that are mutually beneficial. Some of the
adaptations inspired by nature are: riblets (shark skin); trailing edge flaps (bird feathers);
compliant coatings (dolphin skin) and slots (pheasant, split tail of the falcon, layered
feathers of certain birds). It is instructive to return to analysis of the Humpback whale to
develop a brief understanding of its behavioural characteristics. Subsequently, an
explanation can be formed concerning the reason that tubercles evolved over time and
became an integral part of the flipper leading edge.”
Humpbacks corral their prey with small diameter nets/circles of bubbles.
Tight turning offers an advantage.
Re , Stonys comment #121 how much drag does a fin contribute to overall surfboard drag ? Is a 5-8% reduction of the fin drag component significant to overall performance relative to the average surfer ?
Whatever is happening on the wavegrinder fin ( re, drag ) is significant enough to be immediatly noticed by those that use it ( wrcsixeight ) even when just paddling .
#107: wrcsixeight wrote:
“…it did not have the same drag free feeling of the WG2. It was not quite as fast…”
“It just lacked that almost astounding drag free acccelleration speed…”
gbzausa wrote:
“Whatever is happening on the wavegrinder fin ( re, drag ) is significant enough to be immediatly noticed by those that use it ( wrcsixeight ) even when just paddling .”
WG2 with or without tubercles?
I was referring to the effect of adding tubercles to fin designs.
Benefits of tubercles may be planshape, aspect ratio, sweep, velocity and flex specific?
The turbucled fin I am reporting on, has the same high aspect ratio and general outline as the WG2 fin, but for the turbucles, and there are NO winglets on the turbucled fin, which I called the BLEF fin in previous posts.
If the WG2 fin’s speed is a 100, the regular raked fins I was using for years previous are about a 75, and the turbucled fin is about a 90, in terms of straightl line speed and accelleration to that speed.
My longboards are limited in top end speed due to soft old school rails and rolled bottoms, so my observations are from 1st through 3rd gears to about 7500 rpm, there is no 4th gear. The polycarbonate WG2 achieves those high rpms in third, the fastest.
I so want to try this high aspect winglet fins in a multifinned shorter board. At the minimum I can see the center fin being a serious upgrade. 50/50 side fins… I don’t know.
The turbucled fins turning radius is significantly less, as it is loose, and still faster than my traditional raked fins that I made myself. If I was in placebo mode, then I would want my own fin to outperform these weird looking high aspect designs. It can’t, it does not.
I doubt I’ll ever use my raked fins again in these longboards.
I’ve never made a cent in the surfboard industry, and never will. I’d love it if Wavegrinder threw me some cash or free shortboard fins for my honest review, but I expect nothing.
I am just thankful to MrMik and wavegrinder for their efforts. MrMik buying the WG2, sending it to me, then hooking me up with two 3d printed fins, mailing them half way across the world… well, Cheers, I feel honored, and enlightened.
Once I get the WG2 fin back from that local ripper and post his review/thoughts, I’ll send it off to the next Swaylockian who wants it.
Another snippet from that most interesting thesis about tubercles on airfoils:
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“In summary, leading edge tubercles allow the flow to remain attached on the suction
surface of an airfoil up to higher angles of attack. This leads to an increase in stall angle
and hence, higher maximum lift coefficient. In addition, complete stall occurs much more
gradually with tubercles since different spanwise sections stall at different angles of
attack. There is minimal effect on drag with the presence of leading edge tubercles at low
angles of attack. At higher angles of attack, however, a larger lift coefficient could be
achieved at a lower velocity with the presence of tubercles and thus there would be a
corresponding reduction in drag.”
You might like these links. Some journal references too.
https://asknature.org/strategy/flippers-provide-lift-reduce-drag/#.WYXnBYTyu70
https://www.technologyreview.com/s/409710/whale-inspired-wind-turbines/
https://www.researchgate.net/publication/15547901_Hydrodynamic_design_of_the_humpback_flipper
http://www.dtic.mil/get-tr-doc/pdf?AD=ADA613124
It seems like cetacean pectoral fins with tubercles should be more prevalent.
Is there another variable to consider?
Span? Planform?
quote:
“I believe the nodules do two things, one that has been proven, one that has not,” says Paul Bieker, one of Oracle Team USA’s core designers and a principal at Bieker Boats in Seattle, which has successfully employed nodules on some designs. “The proven effect is an increase of the maximum lift angle of attack, i.e. a more gradual stall. The non-proven effect is the rotating turbulence from the tubercules creating ‘fences’ along the suction side of the foil [on boats with a single rudder], which may delay ventilation.”
Since Rambler 88 carries twin rudders, says Bieker, the primary benefit here is a boat that’s a touch more forgiving on the helm, albeit at a price. “There’s a small drag penalty at normal sailing angles of attack,” Bieker says. “For this reason, I don’t expect nodules to proliferate in grand prix sailing.” Time will tell how they serve Rambler 88."
endquote.
Source:
http://www.sailmagazine.com/boats/design-and-technology/tech-talk-rudder-nodules/
" a more gradual stall" While I’ve only had the BLEF fin out twice, I believe this is a key component in the ‘predictability, reliability, and responsiveness’ that were quite apparent right off the bat.
I am not really following the ‘creating fences’ reference
The BLEF fin does not have the same turbo factor as the WG2, but is still faster than my traditional raked fin, and it turns way better. It just felt so incredibly solid I am eager to get it out again in different conditions, like some windswell where smaller pockets exist and a shorter turning radius is more appreciated.
Before trying these high aspect ratio fins I had no idea just how much resistance the rake has to turning the board. The lack of any sucking sounds from the tail on my soft railed LB’s during the seconf half of a turn, so far, with the BLEF, is really saying something, in my opinion.
MrMik’s first try with tubercles seems to really be onto something, in my opinion.
4 years ago Hans wrote:
“If you’d like to reduce the drag, consider high aspect ratio foils. Due to relatively small tip vortices, high aspect ratio foils induce less drag. (think of gliders (sailplane) and formula windsurfing fins).”
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.
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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.
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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.
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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.
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Unfortunately Roy and Geoff did not get along with each other, surprise, surprise.
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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.
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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.
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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.
quote:
“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."
endquote
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.
I found the patent for the Wavegrinder fins.
A great read, unlike most other patents regarding various abstruse fin inventions.
https://docs.google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US20070093154.pdf
from the article you linked:
“There’s a small drag penalty at normal sailing angles of attack,” Bieker says. “For this reason, I don’t expect nodules to proliferate in grand prix sailing.”
how often is a surfboard operating outside of normal angles of attack. and, probably most importantly, for how long?
are you sacrificing down the line speed just to squeeze a little more out of your snaps?
“only very slight corrections could be made to the line taken”
inefficient foils and cavitation can be your friend!
This is very true, but could also be likened to a parachute being the friend of a skyjumper. Have we as surfers become dependent on fin drag?
Yesterday I rode mr Mik’s high aspect turbucled version of the WG2 on my bigger longboard and my Mind is blown. The Wavegrinder WG2 fin pretty much does not want to stall, seemingly ever, and is superfast, but the turbucled fin seems happy as a clam in any part of the wave I have been in. But does not have the WG2’s rather insane speedy qualities.
Applying lots of back foot pressure and stalling hard to stay in the pocket, the WG2 bucks and feels weird, but the turbucle fin is a dream, allowing me to feel the round pintail like never before while waiting for the wave to feel bottom and stand up, and then removing backfoot pressure the transition from stall to accellerate is seamless, and I was completing rides trying hard to not to not start laughing maniacally as I was kicking out.
The waves were fun, but the feel of the board with this fin was unreal.
The ONLY detraction I can find with the turbucled version, it that it is a kelp and sea grass catcher. Even with this detraction, I would still glass this fin into the board and never bother with any other fin ever again within it. I plopped it into the center of the fin box and have not tried moving it fore or aft, as I can’t really fathom any additional improvements to the feel of the board with this fin, at this point.
And when i run over a larger piece of kelp, and start dragging it along with me nearer the tip of the fin, What it feels like, is pretty much exactly the same as the regular raked fins i have been using in these boards since 2003 and 1997 respectively and all previous old school ( pre '67) longboards back to 1984 or so, that taught me how to longboard when the waves were too small for a shortboard.
At least in traditional style Single fin longboards, surfed more traditionally, the high aspect fins work very well, and the turbucled version is mind boggling in its responsivness, crispness, and forgiving nature. My bigger LB weighs close to 25 Lbs, but this fin makes it respond as if 10 Lbs lighter. The high aspect ratio makes it apparent just how much resistance there is to directional changes with a longer raked traditional fin, and I do not miss that resistance, at all, not with the turbucled version, though the WG2s weirdness at the end of a hard turn bottom or top or during the second half of a turn was something to contend with that i never quite figured out when and why and how to counteract it. The turbucled version has NO weirdness at these times.
I bet the fin could also be shallower, and thus even faster and looser. A slightly underfinned board is obvious, An overfinned board less so. My thinner round pin or pintail boards are nowhere near underfinned with these 9 3/8 inch deep fins, yet they do not feel overfinned either.
Mr Mik has shrunk a turbucled version down to 83% for me.
I can’t wait to try it.
Since most of these fins seem to be tested on longboards, is there any noticeable difference in noseriding?
Regarding nose riding, My smaller longboard is a poor noserider as it was not intended to do such things, but my longer one is much better, yet is far from a design where A lighter weight person could perch there for the whole wave posturing and thinking they are ripping. Noseriding is enhanced slightly, as in the board seems more stable when cross stepping fore or back, with a bit more control when in the mostly uncontrollable zone when father than 2/3 up the board. The extra speed of these high aspect ratio fins seems to shorten the time one can remain forward on the board and a faster backpedaling could be required.
There have been a few times when up in this area I expected to bog the shoreside rail while stuck in a track, only to not have it occur. Planning for a fall which never occurred has left me in strange positions to try and continue the wave smoothly. Probably look like a kook. Oh well but better than a fall and long swim.
They are definitely not a detraction in any way to noseriding, so far as I have noticed, but my days of trying to get as close to ten toes over as possible every time the wave allows, are long gone.