Dorsal Fin plan shape (from Dolphin resource pic)

I decided to copy the outline of the dolphin dorsal fin from the resource post made earlier today–mostly for a distraction, but also curiosity. I’ve attached some screen grabs of the outline–If you use Adobe Illustrator to make fin templates I can send you the actual .ai document. Otherwise, I can email you a PDF, but they are too big to attach at their actual size.

I estimated from the picture that the fin depth was about 5", depending of course on where the bottom of the fin was determined to be (you can see how I cropped it from the blue lines). 5" depth x 8.25" base–sounds like a fish keel to me.

If you look at the front view of the dorsal fin, in the resources section, you can see just how thick the fin is. It’s really much thicker than I had imagined. The other thing I noticed was how ‘flexible’ it looked. Does anyone know what the flexibility of the dorsal is like and if dolphins have any control, as in muscular control, of the fin. I imagine that the fin is just cartilage. Any experts? The third picture is of a dorsal fin that looks quite flexible, but doesn’t answer the question of control.

I seem to remember a fin design by Mike HYNSON, back in the '70s, that was an actual copy of a dolphin’s dorsal fin. Was it a FU or a WAVE model? Anyone remembers that or, (even better) actually rode with one? And if so, maybe you could tell what it was like?

Are you talking about Mikes production dolphin fins, made of glass filled lexan, kinda thick and FU box?

We tried them…worked fine, kinda lifeless, added not much, but did nothing really wrong, except maybe for critical section dropouts. Wasn’t flexible enough, we surmised, and not the best for super pivot turns.

Now before you post pics of how quickly a dolphin can turn, bear in mind your surfboards doesn’t have additional fins, are stiff as a board, and operate solely on the surface of the water with only the muscular control of the surfer.

Picture number 2 looks like it would work nicely on a twin fin, or any wide tailed twin ie, Lis fish.mike

Mike Hynson circa 1974…I think he was across the street from the esteemed Mr. Barnfield…

I had one on a 6’ 8" dove tailed David Nuuhiwa with the downrailed nose…sorry Chip, no pix. It walked away from me after an all day surf in San Onofre as I slept beside the now empty spot.

Back then it “rollercoastered” well and I loved how it hummed…serenading me across the wave…apparently didn’t know the words. Gil

Picture didn’t load or I screwed up. Sorry, I’m running late and have to leave now…search Dolfin at

I ran the search but came up empty. Please post the pic when you find the time.



try this link:


I’m curious about the setup, and approximate dimensions of the Hynson production fins you tested. Did you run it as a single?

I picture them as alternatives to fish keels as rooster suggested. Or maybe as the center fin on a widowmaker. Probably not a fin for a thruster (not even a scaled down version).

About how long ago were the tests?


Is this the Hynson you’re talking about?


I seem to remember a fin design by Mike HYNSON, back in the '70s, that was an actual copy of a dolphin’s dorsal fin. Was it a FU or a WAVE model? Anyone remembers that or, (even better) actually rode with one? And if so, maybe you could tell what it was like?

you’re on the ball, billy , one day we gotta meet and swap “Surfer” mags , I reckon !

the ad had the dimensions in it too , I recall .

give me a few days …it’s ‘mal’ adjustment day tomorrow , for me [glossing the deck…wish me luck !!]

cheers !


The design for the fin came from “Dolly”

at the San Diego Sea World facilty. Mike got permission to take detailed templates from the fin and Bill Bahne had the fin design molded from lexan. I had one in a 6’10" diamond tail from the era and it held in amazingly well for it’s lack of height. The thickness of the foil was about 7/8" to 1 inch thick.

I found the Hynson dolfin on Thanks Native_Customs.

Hynson’s looks more upright and has a smoothe curve on the leading edge. Maybe similar rake, but definitely more like a classic single fin overall. The copied dolphin fin looks more like a delta fin/keel.

I wonder what the variation is between individual dolphins in the dimensions of the dorsal fin. And noone has touched on the flexibility and control a dolphin has on its dorsal fin.

Yep, those guys are on the ball !!!

Did ride loose, easy turning, overly smooth, but never a sense of real security when things got hairy…

Those days, except for a few experiments by certain “wierdos”, every board was a single fin if the fins were longer than 6".

My I thought was 7.75, but that was a long time ago to remember…

Yeah, super thick and curvy foil seemed very unobtrusive on the board…

I had one on a weird pintail with heavy dome v in front of the fin going dead flat behind the box. Best tube rider I ever had…no hint of drift or slip. Goes to show ya; you never know what is going to work well with a given board shape until you try it.

Still have my Hynson Dol-Fin and used it for a couple of months this year on an 8-1 diamond tail - as a single fin - and it still has merit as a functional fin design in my opinion.

Though shallow @ 6" with a base meas. of 6 1/2" the area more than compensates for the lack of depth. It is thick - just shy of 1" at the thickest spot of the foil out to about 1/4" very near the tip. Very little flex at all - VERY little. It’s really about placement with this fin as an inch either way can make all the difference in how it rides/holds. Haven’t tried it as a 2 + 1, but would think it could be fun, especially on a longboard (9’). It’s original use for me was on a 7’ pocket rocket when it first came out - got one of the tubes of memory at Tarantulas with it so I could never part with the fin - or the board.

“Dol-fin” , eh ??

…and here’s a coupla others from that era , too …

I prefer the invisi fin

When I consider that the purpose of the dolphin’s dorsal fin is to maintain directional stability and at the same time facilitate ease in directional change (Look at the broad leading edge, calm foil and overall thickness) I think to myself why do I want a fin like this on a surfboard. The thing I look for in a performance single is one that will give drive and this one does exactly the opposite. It has about as neutral effect on drive as any one I can imagine.

The dolphin drives with it’s tail and pectorals so shouldn’t we look more closely at this part of the anatomy when we consider how it relates to surfboard performance?

Just thinking out loud, Rich

Agree absolutlely.

We just couldn’t understand how unstoked we were after trying those fins, even thos they were hyped in the mags.

Much better were RalphEhni’s long sabre shaped fins with a base width around 3.75" and lengths from 9.5 to 13.5". Those fins were low drag, super fast, and projected long distances out of each turn.

46 layers of 4oz, Ralph was our glasser also.