The Visible Fin Tip Vortex... Underwater Video

Towing a camera attached to several fins has shown the occassional presence of a visible tip vortex, usually visibly  present on the second half of  harder turns, but it will show up after kicking out of a wave at speed and turning the board back to sea paddling too.


When passing through turbulent water from the previous wave the fin tip appears to collect the bubbles and funnel them into a more visible tip vortex, like shown in the photo below, but there are examples of the visible tip vortex occuring in cleaner green water too.


Its not hard to understand how already present bubbles get captured and combined into the visible tip vortex, But:


How do these bubbles form several inches below the water surface in near clean green bubble free water? Separation of flow vs cavitation… I though the true definition of cavitation could not really occur at surfboard speeds, that enough energy could not be created to form a void.


I’ve not uploaded any video to youtube or similar at this point but plan to, soon.

I’ll search some more videos for examples of clean green water visible tip vortex and take screen shots, the photo below was just convenient to attach at this time

Always thought this strange anomaly was caused by poor finishing of the foil.

Perhaps a slight humming under stress…

I think you’ll find there’s not enough energy involved for it to be cavitation.

Seemingly clean, green, bubble free water will stil have microbubbles suspended within it.

The fin tip vortex will create enough turbulence to mix these microbubbles together to the point where they begin to coalesce and become large enough bubbles to be visible.

That’s my theory and I’m sticking to it.

Having just rewatched most of the video I captured last year, searching for good examples of vortices, I realized that no tip vortex is visible in clean green bubble free water on my feet at speed. So I will eat some crow and retract the comment that they were happening in clean green bubble free water during hard turns.

The two fins below are  my traditional wood dol-fin, hand foiled in 2003, and imperfect. I used to love it.

Second  photo is mr mik’s 3d printed smooth turbucle free gull wing fin. Which should be a Naca or Eppler foil 

These 2 fins are the easiest to find visible tip vortices, and they are pretty much visible only with bubbles already present, to coalesce.

Other fins I have videoed from this angle, are much higher aspect ratio, with turbucles, and the visible tip vortices are much rarer and shorter lived and the line of bubbles is straighter and thinner.


Some of the longest lasting vortices are present on my final ride in, when I have gotten to my belly and angle hard up or down the beach, partially slipping the fin sideways.


If any tip vortices are happening in bubble free water on hard bottom turns they are hidden by the rod holding the camera a set distance behind the fin.


I’ve almost gotten things prepared to tow the camera behind a multifin shortboard.  I suspect the towed in rail fins will have lots of visible tip vortices. Hoping water clarity cooperates for better video. Should be interesting viewing, if not very informing.

The yellow fin is an early version of Mr Mik’s G-whale fin, and it has more hold and much less drag than the bigger wood dol-fin under it.  

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First youtube upload ever, for me, Guess I only saved it in 480p when i edited it, it records in 1080.  I am however digging youtube’s 0.75 speed option setting, I’d only seen  rides at full, 1/2, and 1/4 speeds previously.


At about 00:17, check out the ring bubble which passes by the fin on the left.  I have captured about 10 of these on video. I ‘think’ the concave in the nose of the board captures  a piece of chop just so, and propels it downwards.


Those  4 and a half minutes of catching/riding those 11 waves, were captured in 42 minutes from the time I paddled out, to when I got back to the beach.





Tip vortex?     Just because you don’t see it, doesn’t mean it’s not there!         Tip vortices occur in clear air, on aircraft wings, all the time.      Air and water behave in much the same way, despite the difference in density.

Wow, you are really putting in a lot of effort! 

Watching videos of fins in action is still messing with my head. Some fin movements seem to be opposite to what I would expect. 

If I was surfing more often, then maybe I’d stick in some poorly designed fin and check if the video footage is much different, regarding tip vortex. But I’m very short of time at the moment, and I am still surfing almost evey fin before I send it to ‘beta testers’ for want of a better word. And every surf session is kind of sacred, I don’t get enough of them to use bad fins! 

The purple/yellow Gullwing fin with smooth leading edge might not have a proven foil. I cannot find it in my records at the moment, when did I ship it? There is probably a post with a photo and maybe more info, somwhere earlier in this thread, not sure. I printed a few Gullwing fins with a foil that I concocted. Is it concave between the thickest part and the trailing edge? If so, then it’s one of those. That foil might be sub-optimal. 


Correct. The tip vortex is always there when a fin is creating lift, but not always visible. It will be visible more often when there are more bubbles in the water.

(Wrcsixeight is of course well aware of this fact.)


The earliest photo I took that I can find of the smooth purple gullwing fin you sent is from November 29 2017.  On its base, whose whose screw tab and roll pin area I was reinforcing with roving, in indelibel ink might indicate  a build date of August 14 2017.

I believe it was a white earlier version of this fin that you sent that has the concave on the trailing edge.  That fin’s tip broke off as i was showing someone in the parkng lot just how flexble it was.  I fixed it making it stiffer, and then it  was mailed off to a swaylockian who mailed me some wavegrinders, when I returned them.

I liked how both these purple  gullwing fins felt during turns.  Both were better than my regular dolfin, they were just nowhere near as quick and loose and precise as the G-whale fin.  Even though I relocated the roll pin higher on the base I did not achieve base flanges  flush on the hull of any of these thick flanged fin bases.  Unlike the GW fin in my board right now.

I had made that specific ‘universal’ camera rod so it could fit onto any fin I did not mind drilling holes into, and tried a bunch of different fins in following days, but none since.

I’ve made a new camera rod that should capture better video, and have lower drag. I hope to employ it soon in clearer water and different light angles.

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Sometimes the G Whale  turbucles drags kelp, sometimes they cut it. I ran into this piece on the drop. Video is at 1/2 speed.

Thin Tip vortex becomes visible on left and crosses the tow rod when kicking out on this right, at ‘river’.


Looks like most of these videos i edited a while back, I  saved in low resolution, looks way better on my laptop than on youtube.  

Pretty cool video. - I find the water off the bottom of the board more interesting. 

Care to show a shot of the camera and fin hook up? 

I would be interested in trying something similar with some hotcurls (finless)

I’m sorry - can’t resist.  What if you eliminate the tip?  

Was unaware of the ‘spiroid wingtip’

Seems counterintuitive that something tacked onto the end of a wing reduces overall drag, rather than increases it.


Don’t know how relevant it is to surfing, unless perhaps one only surfs in one direction on a rifling pointbreak.


I have a WaveGrinder WG2 fin with the winglet.  The winglet’s angle, when it aligns with a certain board’s tail rocker on a certain part of the wave face, is very fast and loose. I was very surprised with it when i tried it, and been on the high aspect ratio fin kick ever since.

  My LB with much less tail rocker was quite happy with the WG2, my LB in the videos that has much more tail rocker, was less so unless the tail was very high up in the wave face.  The WG2 fin would seem to also seem lock onto a track and accellerate and dictate the line taken.  Thrilling often, but equally frustrating at times.  The high aspect turbucle fins do not track and seem happier than pig in feces in just about anywhere on the wave face. 

As I collected videos I decided the camera needed to be deeper, as bubble laden turbulence would often come across the deck, hit the water on opposite side, submerge, and slap the camera. Perhaps the decks of surfboards  need edges on the tail for cleaner release and less drag.

Earliest videos with the camera at a shallower depth it was getting smacked around much more often than in the video posted, and also felt draggier.

I don’t know how this  behind and under the board type of footage could be collected with a finless board without some way of keeping the camera near a certain depth and distance behind/under the board and prevent it from spinning wildly.

 I fear a shortboard  center fin is not deep enough, when I get around to trying that, but my 6’8" has a single fin box and fcs plugs for sidebites, but I fear the leash and its ability to shear off the camera and or fin. 


As far as the camera itself, how I attach it to the rod, and fin, at what angle and distance, that has also evolved is still evolving, with lots of thought and time and labor expended to better the view and security, and decrease the drag. 

I am not really willing to post it for all the world to see.  There are clues in the videos themselves as to how it is attached to the fin.  


No worries man. Appreciate the insight. 

If you might be willing to point me in a direction of the camera. You can pm me. If that is g14 classified no problem. No pressure. I’ll track something down and work it out. 

Cool video nonetheless. 





This is such a cool camera angle. I felt the same way watching your footage as I did the first time I watched a clip of a wave shot from a drone’s-eye-view. I’d love to see what a wave looked like from this angle at a clear, clean, hollow, overhead reef break. 

What a cool post. What I wonder: forgive me if I missed the answer: what did it feel like to surf with a camera attached like that?

I could be delusional, but I always surf with fin keys in my sleeves (2 because I’ll often accidentally drop one while making a change), and moving (say in a quad set up) a fin by 1/8 of an inch or so seems to produce noticeable changes as soon as I start paddling the board again.

What kind of camera set-uo was this, and what was your experience of having it attached & dragging? You mentioned you changed the set-up, so presumably it was to reduce some drag? The differences between a board that planes/trims well and one that doesn’t seems to be fairly small.

None of this is to overlook how potentially useful this kind of experiment is or could be.

The mere presence of the visible bubble vortex is interesting to me. Any time the fin is loaded, there is a tip vortex occurring, mostly invisible in clear air or water, and only sometimes does the fin have the ability to coalsece, and perhaps enhance, those bubbles, into one longer trailing visible spinning bubble getting dragged from the fintip.

When it happens, where, for how long, how it changes with different fins wave periods and sizes, water clarity, sun angle…, the strength of my coffee…

All can affect the appearance, and timing  size length duration of that spinning fin tip bubble.

Is a shorter thinner stretched spinning bubble mean the fin is better?  I think it means there is less drag. Is that always a better thing?  Certainly not. If it were then perhaps rockerless finless and parallel sharp rails is the future.

It’s been said many times drag is control, but what if the control is as good, for less overall drag?

Airlines are wanting to save fuel with wingtiptip vortex reductions, but there are likley advantages to a shorter wingletted wing providing the same lift for the same overall drag too. My comments about a rifling pointbreak and the spiroid winglet relevancy, were singlefin minded mode, apologies.  Some wing(lets) foils are obviously intended to lift efficiently only in one direction, unless angle of attack  dictated otherwise. 

Perhaps some spiroid winglet on each rail fin would not be irrellevant.

The ‘tipless’ mirror fin prybar tail board is genius, I wonder how it feels underfoot.


  What  would  fin templates  and foils  evolve into IF for some reason the goal were to design a fin that always has that  long wide bubble attached to the fin’s tip for the whole ride?   Say surfing at night in a red  tide and the longer  and brighter the trail of blue or green phosphoresncence won you the supermodel nymphomaniac as the week long prize?

What about the fin that was seemingly always immune to the possiblility dragging along that visible, spinning bubble yet also kept the board from spinning out when angling parallel to shore or redirecting quickly, or seeking a steep angle higher on the wave face?

Does the bubble allow the water spinning around it to spin faster and break off earlier, perhaps the opposite and later? Perhaps the vortex  becomin visible  is Akin to when a car’s tires start breaking loose and squealing when cornering at high speeds.  Kind of be better if the tires did not start squealing, if one was being chased down/ timed. 

Is the ulitmate Happy medium a dol-fin style  template, or something else? 

 Its Opinion, either way, not fact.


As far as how it feels when surfing with the camera on the fin, I know its there, but rarely did I have issues keeping ahead of the wave. Me and this surfboard together are toying the 250LB /113KG range.

 No doubt a lighter surfer/board combo would feel the drag of the camera more. I’ve  always preferred heavier boards, and not just from a durability aspect.

The waves I’ve towed the camera, have not been rifling waves either.  Chest/neck high at best, and the in video posted conditions were barely waist / belly high after the drop.  Turning is, if anything, easier with  some degree of  slower entry speeds, and the camera rod drag has to assist twisting the fin rotationally, as well as assisting flex laterally too, to some degree.

 Honestly it still Feels pretty natural, just overall slower, sometimes much more than others.  I’ve had some rides where I swore the camera ripped off the rod or the rod from the fin, as I could not feel it anymore and was cursing as i was kicking out getting ready to search underwater for it.

 I’ve had some other rides where it felt like I was dragging a huge piece of kelp or lots of seagrass on the fin or camera or both, and sometimes  saw them on video later, sometimes saw no visual reason why it felt draggy, when watching the footage captured shortly after while the rides are fresh in my mind. Be great to have above water footage too.

 I do fear losing the board more with camera attached, since I use no leash riding this board, and the leash might shear the camera from the board if it were used.  Just Getting another camera is not desirable and neither is losing the footage acquired to that point. The sandblasting on the inside in shallow water has not yet obviously dulled the lens, but I do try and limit the sand exposure, and the board hitting sand after losing it has not yet occurred. Close, but I did not hit ‘record’ properly that session.  Shame, as it was likely the best conditions I videoed in.

 Paddling obstacles  and oblivious beginners are given a wider than usual berth or a louder grunt, but I have encouraged drop ins from  a select few whose skills and temperment I trust, to hold a high line as I try and catch up and pass. No takers so far.

Some potential rides where perhaps I too late to make the drop, I opt out of instead.  The camera is most noticeable when paddling at/toward an oncoming wave, then swinging its tail around and into the wave for the buoyancy assisted take off. The swing occurs much slower, feeling way more resistive, and the initial buoyancy assisted paddle does not get the same initial shoreward squirt, until the camera falls in line.

The longboard in the videos has a limited top speed with lots of tail rocker and soft rails off the tail but the top end speed does not feel significantly reduced with the camera in tow. 


I am not willing to share the specifics and evolution of how I am recording this field of view, at this time. 





I think you’ll find that drag at the fin tip does not equal control, or any increase in control.

The less of a “bubble stream” that your fin tip produces means that your fin tip vortices have been reduced and your fin is therefore more efficient.

Fin tip finlets (Horan Starfin/Wavegrinder) are one way to “contain” the fin tip vortices created by the high pressure side to low pressure side “spillover” at the fin tip during turning. “Flat” finlets at the fin tip is another design which will reduce the pressure differential between two sides of the fin at the fin tip and reduce said “spillover” and resultant vortices.