A Modest Epiphany; Fins are Energy Transducers

General Discussion
21

Craftee,

Good post, but without trying to be a smart arse, in my humble opinion, Fins are NOT the engine or power source. I put it that the real source of power is created by a combitation of the movement of WAVE action, GRAVITATIONAL FORCES generated in decending a wave and the interaction of the SURFER riding a FLOTATION DEVICE whose bouyancy keeps the rider on the wave/water surface and travelling in a direction perpendicular to the energy source.

One does not need a fin to CATCH or RIDE a wave. Witness Derek Hynd riding his wide variety of FINLESS surfboards with far greater result than probably 80% of surfers on the planet.

So if fins are not the power source, why do we need them and why are they so important?

Back to the race car analagy however, as it is the very basis of what has some very relative aplication to the physics of riding a wave.

Put the best driver in the best aerodynamic and performance tuned car with the most powerfull engine and it all means nothing if you aint got traction, drive, grip etc because that is the intersection whichshit happens.

TYRES are THE most VITAL component of a racecar and FINS are the TYRES of a SURFCRAFT. No FINS, NO RESPONSIVE DRIVE, RESTRICTED DIRECTION CONTROL IN TURNING, NO ABILITY TO HARNESS ADDITTIONAL RESPONSIVE SPEED…NO SURFING IN A FORM/STYLE CONSIDERED NORMAL (whatever that is…ie ASP standards. Derek rips but I can’t see him or anyone else, winning on a finless board the way he did ring ‘finned’ boards as a top ten surfer way back in the eightes). Shit , it has nothing to do with ‘real surfing’ as anyone who witnesses Derek’s ‘advanced surfing’ will only bag it thru jealosy and because it is so free and innovative that they either could never do it or are too shit scared to even give it acknowledgement. It is truley entertaining,

So before this good and healthy debate goes too far, I humbly suggest one should agree or disagree on the TRUE ROLE PLAYED THE FIN/FINS.

As only then will the debate have any true foundation from which to base so many ‘expert assumutptions’ that permiate this website.

Surfboards are volumetric flotation devices and their respective shape plays but a small part in a range of dynamic forces too great to comprehend in a society that holds shapers as ‘gurus’ and measures the creativity of riding waves as a subjective mathematical number that fuels shareholder value in a multi-million dollar corporate race for brand recognition by companies that have not spent a cent on the development of surfboards and what makes them work.

22

Hi Craftee,

I respect your opinion. I think you discovered something I discovered too when playing with fin materials.

I think it has to do with flex and twist of the fin. The stiffer the fin the more push it will give you.

I think Greg is good in adjusting the fin outline to reach the right flex pattern.

G10 is a stiffer material with better flex and reflex properties as polyester and glass.

Especially the reflex is what gives you the push.

Not loosing energy that is stored in the flex.

Like the twang in compsands.

Wish I could try a Griffin board once too…

Too far away and poco dineros…

Soul

23

Likewise good post.

IMHO, fins work like sailboat sails. Sails convert the earth’s wind energy into kinetic energy of the boat. Sure you can glide a finless craft along a wave, but it is nearly impossible to take a standard surfboard and really POWER a board/rider on a wave without fins.

In the left sided video, watch Tom Curren’s ride and ask yourself if that TRANSFER of energy, from wave to surfer and from surfer to wave, is possible without fins.

http://www.aspworldtour.com/2007/videogal.asp?rView=&r9Sys=&rEventName=Billabong+Pro+J%2DBay&rEvent=jbay06&rwhere=J%2DBay+South+Africa&rwhen=Jul+2006&rXLSFile=2006mcevt06.xls&rCode=72000&rDay=8

Onward…

24

I have a longboard skateboard.

While standing on it, I can push my weight from side to side, without moving my feet, and in doing so I can propel myself up modest hills.

What is the energy transducer?

What is the power source?

Completely analogous physics apply to pumping a thruster through a bottom turn. If you feel the squirt you know the board is generating acceleration through the turn, is doing so via the fins, and is capable of converting push from your legs into forward motion of the surfboard to further optimize your capture of the energy of the wave.

If I fix the trucks on my longskate, I can no longer propel myself forward.

If you surf on a finless board, OR EVEN RIDE ONE WITH FINS ALL PARALLEL TO THE STRINGER, you cannot convert energy from your legs into forward motion. No squirt.

This “squirt” is an additional basis of control in interacting with the wave at the highest performance levels. In waves up to slightly overhead, you cannot watch a single ride by a professional in which he does not use this simple maneuver. In smaller waves, such as those recently broadcast at Mundaka, riders like Taj were generating speed via pumping multiple times on each wave in rapid succession.

25

Onward…Ho!

My point is that Fins are not THE POWER but the only way to TAP into the power.

Like I said before, they are the most vital ingredient to HARNESSING POWER and CREATING SPEED , DRIVE etc,

The relevance of fin design and the corillation to performance surfing so far outweighs the relevance of "board’ design is is almost a mute argument.

I guess it is a fine point between our respective positions in that regardless of the actual power source, fins are the quintessential hub of generating a resistant force that when activated equates to what we as surfers call speed and power.

26

The bottom is the more dominant resistant plane, but the whole thing is about synergy between the fins and bottom, how the surfer works them against and with each other. Pretty dodgy using a racecar/skateboard analogy IMO, but there are fluid flows–the main diffs are that tires/wheels don’t manage fluid flows, the skateboard doesn’t interact with airflow to any meaningful extent, and the car has its own power source–pretty elemental differences.

OBP, you’re right about the thing going in the direction of less resistance, but the thing is the resistance. Maybe I misunderstood you but I think that’s true and I see you could be saying that.

Blakestah, you haven’t tried to shape a board that would work without fins, youre not interested in other types of fins, not even a quad.

Craftee, I agree with the spirit of your original post. I think we just missed the Nobel thing for you this year. Maybe next year.

BTW, guys, buoyancy and lift are NOT the same.

"The relevance of fin design and the corillation to performance surfing so far outweighs the relevance of “board’ design is is almost a mute argument.”

I don’t want to say that’s ridiculous, but that’s ridiculous.

27

Hi Blakestah,

I like your analogy to the skateboard. It explains the principle of the forward motion of pumping. What I’m trying to say is this. Pumping works fine on a dry road, but when it gets wet the trucks have a more limited holding power, losing energy to friction by sliding sideways. This is what’s happening if the fins don’t give back the energy you put in them.

And for the other guys trying to comprehend, imagine a wave moving in the tarmac, if you go straight you go the same speed as the wave, steer sideways, you go faster, and now start pumping up and down the wave bump, you surely don’t want your trucks to slide, imagine what can happen if there is a lamppost in the way…

BIG HEADACHE.

Catch a wave for me?

Greets Soul

28
Quote:
If you surf on a finless board, OR EVEN RIDE ONE WITH FINS ALL PARALLEL TO THE STRINGER, you cannot convert energy from your legs into forward motion. No squirt.

Liddle style hulls have fin parallel to stringer and generate huge squirt (hmmmm). Of course they do flex a lot which during the flex makes them no longer parallel to stringer. Did I answer my own question?

29

OBSERVATION: The original Lis Fish had fins with NO toe-in, and NO cant, (parallel to the stringer) and exhibited plenty of SQUIRT ! Hmmmmm.

30

My primary point and dispute with the original post is that it is not the fins that are propelling your forward. They are, for the most part, allowing you to control the direction of your forward motion.

The thrusters Ive been riding for 25 years accelerate mildly out of bottom turns. My revised 5 finner makes those thrusters feel slow in comparison. This board accelerates out of bottom turns like its got a bigger motor. I have been struggling a bit missing properly timed top turns cuz Ive been outrunning them. I take it, from your responses, you dont thrust your board. Cruisy standup types riding dated setups could never understand what Im feeling with this board. I really dont know what you ride or your style preference. But its safe to say, that our opinions are all relative.

31
Quote:
OBSERVATION: The original Lis Fish had fins with NO toe-in, and NO cant, (parallel to the stringer) and exhibited plenty of SQUIRT ! Hmmmmm.

There is a nuanced divide between very very rapid acceleration and squirt??? A soft, finless, surfmat can at times accelerate so rapidly it sure feels like squirt to me…

32

Tom Curren will look better and surf better on an outdated 1970 plug than your average or slightly above average surfer riding the most up to date equipment. The proof is he went out in a heat on that very thing and did just that a few years ago. The point? Talent will pretty much out perform any board or any system.

If Kelly could clone himself and ride two different boards …now that would be something. Surfing is mostly a feeling. There is no set right or wrong with whats fun.

33
Quote:
Blakestah, you haven't tried to shape a board that would work without fins, youre not interested in other types of fins, not even a quad.

My interests in new designs have focussed solely on maximizing speed through a bottom turn on waves from 18 inches to overhead. I could not find a quad that could do this comparably to the SurfTrux, or even to a thruster…the key being, referring to the turn only.

I already handled what happens when you are not deep in a turn. And beat the thruster design in the bottom turn itself.

A bunch of the prototypes were single fins, and they were designed to get the most out of a bottom turn too…

Some grumpy old shaper told me that the key to performance surfing all lay in maximizing the speed through the bottom turn, and everything else paled in comparison. You get - maintain - and control your speed via the bottom turn. All major performance surfing design changes since 1976 largely served this one purpose. At least to a first approximation.

And that was the purpose I sought to serve, as well. I did not think quads could beat a thruster or SurfTrux in this regard - I think they are an inferior design for this purpose.

Its entirely possible I am wrong, but I have my reasons…and I just watched the best surfers in the world compete on rather small waves in several contests in a row, and none of them are riding quads, either. And performance surfing is their only goal.

I FULLY admit this is not the be-all and end-all for everyone in surfing. And the journey is most of the destination when it comes to testing and evaluating new designs. Just my choice. But it aligns pretty well with talk on squirt and generating speed.

34

Good post Blakestah. I still think singles are the fastest. Thrusters work also…but I think they must be worked harder to get the same result as singles. Obviously…“most” singles struggle to go rail to rail as loosely as thrusters prior to reaching max speed.

35
Quote:

But hey I’ll tell you guys what Ive done. Ive been riding a Griffin5 fins style setup with cheap plastic molded fins. I replaced the rear three with custom made G10. If you had blindfolded me and told me I was riding a new faster better board I would believe you.

Been wiggling plastic thingies in the back of my board. One idea we came up with is that they change cant under load, so you may start with 4 degrees and end up with 6 or more under load. As we know, more cant equals less drive.

Those plastic thingies also don’t “snap” back to give the fun of flex - they’re just sloppy, washing off speed and allowing the tail to drift around - probably why I like 'em - I’m not good enough to ride a board with real direction ;<

Herbert Simon and many other bright people have had good things to say about models. Models are simply tools for thinking. You can think of maps as models, or pictures of flow dynamics. They are things we use to allow use to simplify real world systems - to better comprehend them. Don’t fall into the trap of thinking models are the real world. As Bernard Roy says, “The map is not the territory.” If a model helps you and others see something in a new light, then it has value. This fins as “secondary” initiators model has proven its value in that regard.

36

Fixed to a point, the quad is a tad later than a thruster at providing transitional leverage from large powerful rail to rail moves. A pulled tail will help engage the opposite rail’s rear fin more quickly than a wider tail quad, especially if the fins a located closer to the rails than the stringer/centerline on the wider one. Craftee likes these 5 fins maybe because they have that centerline fin early engagement thru tranistion as well as rail drive which the quads deliver due to more lift and drive they produce by having and extra fin (or even two) burried when on rail. But hard to say without seing the board, the waves and the surfing. Perception is so relative, more so with all the variables of designs and conditions. A board is just one big bilaterial fin.

37
Quote:

Its entirely possible I am wrong, but I have my reasons…and I just watched the best surfers in the world compete on rather small waves in several contests in a row, and none of them are riding quads, either. And performance surfing is their only goal.

Blakestah,

Don’t know much about right and wrong, but wasn’t Kelly riding a quad in at least one of his heats? He was interviewed on the beach with one at least (I was only listening at that point), right before one of his heats…maybe on Wednesday or thereabouts?

Also, with the right flex fin, a single can give some squirt as well, as it is pumped to generate speed. They also give speed out of the bottom turn.

So Craftee, is it the material more than the fin setup? The fin setup is of course very important too, but it sounds like it really lit up when you put the different fins on.

–BCo

38

The G10 is stiff…direct transfer of lift energy; no dissapation due to flex, conservation of energy… all drive.

39

"…I think the signal got lost in the noise.

There are only two sources of energy in surface gravity waves: gravitational potential energy (PE) of the wave changing the surfer’s height and the kinetic energy (KE) of the water movement. The total amount of energy is PE+KE-Friction. Without friction the net amount of PE+KE would be fixed. With friction it decreases, eventually resulting in the end of the ride as the wave energy is dissipated on the beach.

The goal of the surfer is to harness the vertical and horizontal motion of the wave towards the beach into transverse motion across the wave face. This requires a controlled amount of drag. This is similar to the way a keel of a sailboat supplies a large amount of transverse drag to limit the sideslip of the sailboat from the wind forces on the sail and facilitate the forward thrust along the keel direction. Unlike a sailboat a surfboard fin is located near the end of the board, but the rail runs the length and can be dipped in the wave face to help convert some of the energy of the wave into motion across the wave face. Any drag from the board will reduce the available energy a bit, but with skill the loss can be offset by acceleration along the wave front. The wave has far more energy than the surfer can dissipate, so the drag isn’t a big factor unless the surfboard stalls or cannot outrun the curl.

The fin isn’t an engine, nor is just a source of drag. It’s a highly directional controllable drag. The comment that it’s a transducer (or words to that effect) is a better description, as a transducer is a mechanism or device that converts one kind of energy to another. In this case it’s converting potential energy and kinetic energy of the wave into kinetic energy of the surfer in a direction perpendicular to the wave’s motion."

Science Dept.,

MVG Fin Systems Research Lab

I have been making nearly exact replicas of the FCS G5

with CF/coremat/epoxy molded construction so every fin is practically the same size. They are very stiff, tough and light, weighing in at around 50 grams per fin. That makes them very good conductors and transducers of energy as the energy is transfered and not lost to absorbtion by the fin. I can not vouch for the attachment system. I suspect that is an energy sink.

As a reference point,

1 pound = 453.59237 grams, or 9 fins = 1 pound.

Mark

40
Quote:
If you surf on a finless board, OR EVEN RIDE ONE WITH FINS ALL PARALLEL TO THE STRINGER, you cannot convert energy from your legs into forward motion. No squirt.

That’s simply not true. I don’t need an engineering degree to know that I pump single fin longboards down the line all the time. Its all in the leg drive.