The science of flex with Professor Marc in het Panhuis

Stu Nettle
Swellnet Dispatch

How much do you know about surfboard design? Like, really understand why your surfboard does what it does?

If you’re like me, board design can be a fog of emotion and spin. On the one hand, there are people whose design explanations are a songline of feelings and impressions, artistic yet imprecise, and then there are those prepossessed to marketing, who tell the customer only what they want to hear. Close the sale and caveat emptor, OK?

Which isn’t to say there aren’t some people who know why certain features work, but it’s a recognition that design progression has been an inexact science. Most of us stumble along in the dark, perhaps making the occasional discovery but we’re largely ignorant of the physics.

This state of affairs provides fertile ground for Professor Marc in het Panhuis of the University of Wollongong. “Just call me Marc,” says the good professor when I meet him, though with 170 published papers, 4 patents, and a doctorate in Physics his academic title has been well-earned.

Originally from the Netherlands, Marc started surfing twelve years ago. “My wife got me into it. She bought a board and I thought, well, since we have a board I’ll try surfing.” A dozen years later he’s still fizzing with beginner’s zeal, he surfs everyday, presides over the local boardriders club, and he’s focussing his intense curiosity on the mysteries of surfboard design.

I meet Marc at the University of Wollongong’s Innovation Campus. It’s a modern building, all glass and polished metal. Quiet too. Studious people walk the hallways. Yet his office more closely resembles a teenage rumpus room with surfboards and fins strewn about the place. Marc explains that some of the boards are his, yet most of them, there were fourteen in the cubicle, were part of a recent experiment concerning fin design. That story will appear on Swellnet next week.

Given a choice he’d completely deconstruct a surfboard and test every aspect of it. “There’s just so much I don’t understand,” says Marc. But for now he’s finding the overlaps with his academic skill set, namely materials science, and this has brought him to question flex in surfboards.

Marc recalls speaking to a shaper about a new board and being asked if he wanted carbon strips in the tail. “What do they do?” asked Marc. “Oh well, they….help,” the shaper replied meekly. No doubt the shaper was discovering, as I now was, that Professor Marc asks a lot of questions.

“When shapers talk about flex, what do they mean? Where is the board flexing? Through what plane? What is good flex and what is bad flex? It is all shrouded in mystery,” concludes Marc. However, it's a mystery he intends to solve.

We walk out of his office and upstairs to the second level of the building where he hands me a set of safety glasses, and then we open a swing door and enter a white-walled lab. Inside it’s busy, the bench tops are crammed with machines and equipment of indeterminate nature - I can’t name then, couldn’t even say what they’re used for. Yet in the corner is a form I recognise, a shaped foam blank, but it’s sitting inside another machine I can’t identify. “It has no name,” says Marc of the apparatus, “I had to get it custom built especially for this purpose.”

Pensive expression fixed, Professor Marc peers deep into the mysteries of flex (Paul Jones)

The Flex Machine - I think I just named it - is effectively two sets of pads that can grip a board at various positions along its length. The rear set can also twist the board. All of it is built upon a solid metal base, its heft belies how precise the construction is. After all, it’s required to measure in microscopic increments.

To demonstrate, Marc simply presses the nose down and lets go. The blank shudders like a bow then falls still again. “When I’m testing, I place sensors on the board at regular intervals and I apply standard engineering equations to work out what the spring constant is. The higher the number, the faster, or less flex there is in the board.”

The machine is only new and without a body of work to draw upon Marc’s experiments are beginning on the ground floor. He’s testing anything he can to begin filling in the blank spots: good boards, bad boards, boards with a standard stringer, even boards with those carbon strips that help.

But none of it means a thing unless he also includes some field research - otherwise known as surfing. “I’m going to test a brand new board,” says Marc outlining one planned experiment, “then give it to a surfer and tell them to surf it ten times, bring it back and then I’ll test it again.”

“Who knows,” says Marc with a shrug, “Maybe there’s a use by date on boards: good for 300 surfs.” It’ll be just one of many experiments he conducts on the Flex Machine.

The accepted wisdom is that old boards 'die' because water seeps in through microscopic cracks in the laminate and adversely effect the foam. Is this the premise he's working on? "Nothing is assumed," says Marc, "The answers will come from the testing."

And it’s not just standard materials like PU foam and polyester resin that interest him. Marc gets particularly animated when he mentions a new family of materials recently developed by NASA. “Auxetic materials are new, their structure is such that they get stiffer as you flex them,” explains Marc.

When you stretch auxetic foam it gets thicker, not thinner. The more force you put on the material the stiffer it becomes. It also, at least theoretically, can never break. Auxetic polyurethane foam has already been manufactured and it has the potential to shake up surfboard construction.

Auxetic polyester foam gets thicker when strain is applied

There are many shapers currently working to harness flex and if they thought auxetic foam was impressive, Marc has something to top even that.

Most flex tail surfboards are built by joining two materials of differing properties, usually carbon fibre affixed to fibreglass. However, with his background in materials science Marc sees a better way of achieving the same result. Gradient materials are substances that start as one material and then continuously transition to become another.

“For example,” says Marc, “we’ve made materials that go from soft and squishy, like a gel you put in your hair, up to hard plastic.” There are myriad applications for such materials from industrial uses to prosthetics, great advances for humanity, but it’s surfboards we're talking about now. A stringer built from gradient material could be rigid at the nose and gradually become more flexible towards the tail leaving no stress points along its length.

While gradient materials and auxetic foams currently exist, it may be a while before they can be applied to surfboards. For now, Professor Marc is working with what we have, foam boards laminated with polyester or epoxy resins, and there's enough mystery and enough confusion to keep an eager scientist like Marc occupied for a long while yet.

I bid Marc farewell, but not before pulling a flex tail board from the back of my car for him to test. He eagerly puts it under his arm, rubs his hand over the smooth carbon tail, smiles broadly, then heads back inside to the laboratory.

Read more from Flexi Week:
Mitchell Rae's Flexible Trajectory
The Road to Firewire and Beyond

Comments

derra83's picture
derra83's picture
derra83 commented Wednesday, 11 Jul 2018 at 9:37am

The auxetic foam sounds incredible till you see it works when stretched, but boards dont break from being stretched.

stunet's picture
stunet's picture
stunet commented Wednesday, 11 Jul 2018 at 9:54am

My assumption...yeah I know, I know...is that the herirngbone-type structure of auxetics (see Google image of auxetics if that dosn't make sense) wouldn't run lengthwise but at 90 degres to that.

Auxetics are being used in helmets and safety devices to lessen impact, so that's not a typical stetch scenario either.

derra83's picture
derra83's picture
derra83 commented Wednesday, 11 Jul 2018 at 11:02am

Ok thanks Stu.

sharkman's picture
sharkman's picture
sharkman commented Wednesday, 11 Jul 2018 at 1:24pm

question Stu , did torsion come up in the conversation as Johnny's does ?

x

stunet's picture
stunet's picture
stunet commented Wednesday, 11 Jul 2018 at 1:29pm

Yeah it did. On the flex machine mentioned above, Marc can also set and measure the torsion. However, he's only in the data gathering stage of the research. The actual findings - i.e what is good or otherwise - is yet to come.

sharkman's picture
sharkman's picture
sharkman commented Thursday, 12 Jul 2018 at 1:54pm

Is Marc working with a Hyrdrodynamics expert at all?

x

stunet's picture
stunet's picture
stunet commented Thursday, 12 Jul 2018 at 1:55pm

Not that I know of. Why?

sharkman's picture
sharkman's picture
sharkman commented Friday, 13 Jul 2018 at 9:17am

because the Hydrodynamic Scientists have already done most of the work on Flex and Torsion , my USA stringers, Appelcore, have torsion and flex readings per square Cm.....just sayin don't need to re-invent the wheel!

x

zenagain's picture
zenagain's picture
zenagain commented Wednesday, 11 Jul 2018 at 10:32am

great reading.

Watashi wa metabo oyagi desu.

sanded's picture
sanded's picture
sanded commented Wednesday, 11 Jul 2018 at 11:40am

Really enjoying "Flex Week" Thanks Stu!

The Shaper's picture
The Shaper's picture
The Shaper commented Wednesday, 11 Jul 2018 at 1:29pm

Interesting opening comments there Stu and of course interesting subject. It does seem like there is always lots of superficial information and even hype around various design concepts but as you say the proponents rarely divulge much real technical depth. I guess this can be simply a matter of keeping "proprietary knowledge" proprietary . On that point I note that the professor has not shared any findings. As a designer I place very minor focus on the concept of flex for one specific reason. The current broad emphasis on flex is looking for something that Flex as concept can't deliver. Its looking for a spring. A kinetic propulsion out of turns. While I don't dispute the fact that flex produces that particular twang feeling on the exit arc, which is what people are all in love with, my problem is, that energy, is STORED ENERGY, which means that it MUST be removed from another point in the arc, which is obviously the entry arc. That means a split second of reduced propulsion which is of course "a delay" while you load the spring. The good Doctor can probably provide an equasion for this I am sure.. I also want to say here that my comments in no way are meant to undermine the work of Mitchell Rae .. Mitchell is in my estimation a true master.

Lanky Dean's picture
Lanky Dean's picture
Lanky Dean commented Wednesday, 11 Jul 2018 at 10:19pm

"Proprietary knowledge" ?
I think the comment should read " lack of proprietary knowledge".

The surfboard industry was created by teenagers in backyards.
Some shapers have no idea the difference between core materials. Read dhd "Eps Epoxy" saga.
Carbon tail strips " it just works".

Extensive lack of material knowledge.
Complete lack of educating generations of craftspersons about the materials they are using.....

" Proprietary knowledge".

The Shaper's picture
The Shaper's picture
The Shaper commented Friday, 13 Jul 2018 at 11:33am

point is, they think it is. Whether its of value to anybody else is debatable. The big guys clearly know a bit more than they say.

sharkman's picture
sharkman's picture
sharkman commented Saturday, 14 Jul 2018 at 8:58am

actually the current crop of the Big Guys, know a lot less than they think . and they know it!
In the last few years , carbon tail patches , fake carbon stringers , same old designs spruiked up with fancy names , no design break throughs , very little new technology , and now the whole idea of Flex without torsion , it's all pretty Neanderthal , and plagiarism from another era.
to Design you need to know fundamental hydrodynamic theory, so you have an actual technical basis for designing and not just dreaming up shit that sorta trys to sound intelligent...yes Epoxy-core , Vertical Intergrated Flex , Sustainable surfboards that break easily etc, so much bullshit and mediocrity , no wonder surfing is just a former shadow of itself !

x

bigtreeman's picture
bigtreeman's picture
bigtreeman commented Sunday, 15 Jul 2018 at 9:55am

centripetal force, f=mv squared/r
a body following a curved path, the force is orthogonal to the motion of the body and towards the fixed point of the instantaneous center of curvature of the path.
grab a bit of that force in the flex and release it when the body stops following the curved path
or as uncle Frank would say excentrifugal forz
https://www.youtube.com/watch?v=IglQbP-M7_w

Go well,
Colin

stunet's picture
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stunet commented Wednesday, 11 Jul 2018 at 2:40pm

No doubt the confusion/misinformation may partly be explained by shapers holding their cards - their proprietary knowledge - close to their chest, however I also see a lot of conflicting info come from shapers.

An example: In the last few years there's been a fetish for the one board quiver, or something of the sort. You know, a board that can do everything: that has drive and manouvreability, loose but stable, strong but light etc. and I dont think it's in the customer's interest to read such nonsense.

A lot of longtime surfers want to learn but they despair at the complexity. Part of it, I guess, is knowing what is marketing guff and what isn't. Yet it also doesn't help when even shapers can disagree on what works and why. I've seen as much here on Swellnet. So if there's no consensus from the shapers, what chance the punters?

RE flex tails and stored energy: lemme throw a little curve ball at you. The carbon flex tail I dropped off with Professor Marc had a subtle reverse rocker at the tail (see photo below). Theoreticlly, as soon as it was moving and had my weight on it, the energy would be stored. Do you also think at some point the energy was lost?

I'm not too sure but you've got many more years in the field than I do.

PS: The board went great by the way.

Lanky Dean's picture
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Lanky Dean commented Wednesday, 11 Jul 2018 at 10:27pm

"Loose but stable, strong but light"
LOL .

blindboy's picture
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blindboy commented Wednesday, 11 Jul 2018 at 3:34pm

In my analysis there are three sources of energy available. Gravitational potential, kinetic energy from the wave itself and energy from work done by the muscles. If the extra energy necessary to deform the flexible material comes, as I think is distinctly possible, from the extra work done by the muscles, then flex has enabled an overall increase in kinetic energy. More broadly I can't see that science has contributed much to surfboard design. To materials obviously, but its contribution to design itself is much more dubious. The mechanism of surfboard evolution has been just about pure Darwinian selection. Not natural, artificial. A shaper makes various changes to an existing design, like mutations in living systems, most either make no difference or decrease performance, but from time to time a variation is made that noticeably improves performance and it is reproduced widely, again with minor variations, most of which either make no difference or decrease performance, but from ......... Well you get the picture.

CryptoKnight's picture
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CryptoKnight commented Wednesday, 11 Jul 2018 at 4:00pm

There's another angle to view the picture from too. Along the lines of Grand Prix, or high power race car compared too the family jalopy.

'Suspension setup in a racecar is hard as compared to soft in a normal car. Hard suspensions help handling and provide good feedback to the driver. It also enables the driver to move the car confidently since the car handles to his expectation. Needless to say, as the name suggests, the ride quality is “hard”. You will feel most of the uneven road surface and your backside will be sore after a few mins. Soft suspension is tuned towards comfort and offers a plusher ride. While passengers get a comfortable ride, the car handles in a manner which isn't confidence inspiring. Also, body roll occurs on a much larger scale.'

When I exclusively rode epoxies, I loved that instant reaction and feedback, that stiffness, no loss of power at all. Once when Toddy and I swapped boards, and he was on a glassed up, heavy stringer pu, it still felt like surfing a rolled up, wet newspaper. Sloppy in comparison.

Reaction times of race car drivers are nothing like bloggsy's. you can train the thing on top of them crafts... so they can drive them high performance things... believe it or not... in a nutshell.

150 odd mill... Lebron... just sayin...

The Shaper's picture
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The Shaper commented Wednesday, 11 Jul 2018 at 4:15pm

Totally agree with you Stu, on conflicting points of view. In the financial markets, well any market for that matter, its what actually makes the market work. Some think its going up others think its going down, some are just.. buy the bloody thing and hold it. My point is that in many ways its perspective. The surf industry doesn't have a very professional approach to R&D in general so we find that ideas are often tested in the public realm. So the market get un finished concepts which are still actually theories being being marketed due to the intense need for point of difference in a very crowded space. On top of that this knowledge is accumulated at different rates. Truth is proportional to the % of perception assigned to it. So I may know something but not everything and the piece that I don't know has quite a bearing on the bit that I do. Just like your example above ..........it will certainly work no doubt about it .....the designer has adjusted a variable to an extreme in order to try to minimise the F factor (force) required to move the spring, so he is very aware of what I am saying, however I think he has engaged another principal ........... but its still a spring any way you look at it ........I am referring to a physics principal basically the force required to move the spring away from K.... I think it is .....its constant........that's the bit I wish was not there cause if it was not there we have a free energy ride. ..........I went through all of this years ago dealing with fin flex and the like. Its same inescapable physics principal any way you care to see it. ........ I have some more to add to this Stu but time has caught me ........love the thread though hope to get back to it.........a bit later. cheers............

dangerouskook2000's picture
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dangerouskook2000 commented Wednesday, 11 Jul 2018 at 6:54pm

Energy is neither created nor destroyed. It simply changes form. For example, when the energy is stored its called potential energy. Release this and it becomes kinetic energy but it has not been created or destroyed. Some of it will come out as friction which creates heat another form of energy and possibly sound if it makes a noise through the water. You're right the energy has to come from somewhere, in Stu's board's case the slight reverse rocker which when going forward will compress the flex pad due to the water pressure thus storing the energy to be released later. Problem is, Stu, that in order for the water to compress the flex pad it must come at a cost. The cost probably being a loss of speed due to extra resistance. Probably not even noticeable in the grand scheme of things. I guess its the old conundrum of perpetual motion and the reasons why it doesn't exist. Not on planet earth anyway.

Lanky Dean's picture
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Lanky Dean commented Wednesday, 11 Jul 2018 at 9:51pm

Dangerous kook2000,
Very insightful.
A+

blindboy's picture
blindboy's picture
blindboy commented Wednesday, 11 Jul 2018 at 4:42pm

Shaper, I stand by my position that your analysis of flex being unable to deliver extra KE is wrong. Any response?

stinkweed's picture
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stinkweed commented Wednesday, 11 Jul 2018 at 5:06pm

In any turn you are decelerating in one direction and accelerating in the other. If you can store energy from drag during deceleration, and release it in the second half of the turn, the net energy may be same as without flex; but with flex, the difference in speed between entry and exit from the turn will be reduced as you "bounce" out. I would imagine this is quite a useful tool in a surfers toolkit. Not sure what the downsides of flex are though in performance in other situations (if any). (Also 'prepossessed' -> 'predisposed' (I'm a pedant)).

Bad Oyster

The Shaper's picture
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The Shaper commented Wednesday, 11 Jul 2018 at 9:53pm

Blindboy I dont deny that there is a release of additional energy on the exit arc. I have stated that. My question is regarding the overall net effect when you consider the delay ( when I say delay we are down to split seconds these days) required to load the spring with the energy that is released a split second later as you exit the turn. So we have the fan pointing at the sail yea it kinda works......... I do a LOT of R&D and I have found over the years that I have to be very careful about the conclusions that I draw because often there are several options. Sometimes its takes weeks of thought to really pinpoint a cause and effect. When working with test riders I say "only tell me the problem; what you can't do" I don't want them giving me solutions because they will get it wrong or move me away from the base line I am working with.. A wrong conclusion means that I become stuck in a loop. (unless its proportion related of course) For instance a tri fin set up has 100 variable combinations. So if you rode a board where the combination was incorrect you would say that was a bad board or if you did not know better you might say that Tri fins don't work at all. What I am saying is that we often think a board goes great because it has a particular FEATURE where in reality it goes great because the fundamental basics are in tune with the underlying fundamental requirements. So I submit to Stu that he actually has a good board and that it would probably go just as well if the tail was solid. I understand that people are passionate about this, some want to make money from it, I jumped into the thread because I like a good conversation, but also because I think people deserve a measured point of view. At speed Water stores energy. The energy is already there (foils prove that) my mission should I accept it, is to find the most efficient ways of capturing as much of it as possible. Flex may be in the mix to a minor degree but personally I don't think its the holy grail of propulsion that some may want it to be.

blindboy's picture
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blindboy commented Wednesday, 11 Jul 2018 at 10:51pm

I agree that flex is not the holy grail, but would suggest that the key difference between surfers rests in their ability to maximise the energy input from their muscles. This is achieved in two ways. The first is timing or judgement. The second is speed of movement. The first you can learn, the second not so much. Flex is simply one way that design can assist. My guess is that most surfers are simply not skilful or quick enough to gain much from it, but at the elite end ...... a very different story. As for the design process, I really believe in the evolutionary process I described above. If that is true, all you have to do is watch, listen and have deep enough knowledge to know, when you recognise it, which feature has caused the noticeable improvement.

The Shaper's picture
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The Shaper commented Thursday, 12 Jul 2018 at 12:55pm

Blindboy , again I agree with most of what you have noted. However (don't we hate that word) The work and conclusions that myself and others came to in the 90s centered on the effect of flex on the reaction of the platform (surfboard) to the input from muscles as you put it. So in practical terms, a few milliseconds of delayed response from my surfboard in certain situations (lets face it we have all experienced that) is the difference between me getting around a section and not, or tucking in and getting creamed. Where fins are concerned in those days the elite demanded high rigidity in fins (all were glass) now that has been watered down by marketing, primarily of FCS combined with their sponsorship dollars and generational change. Not criticising just observing. My point here is immediate transfer of energy results in immediate response. Other more advanced applications are still striving for lightweight rigidity for immediate energy transfer. Hey if I am wrong which am on many occasions according to my wife..........we will all be bouncing around on pogo like craft at some point. Look I have put forward a detailed practical reasoning based on a physics principal and a whole bunch of evolution as you put it, from a different era. If the guys who are promoting this care to put up the same detailed technical explanation of how they have overcome that issue I am all ears?

stunet's picture
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stunet commented Thursday, 12 Jul 2018 at 1:07pm

@The Shaper,

A quick anecdote that may or may not be pertinenet: A curious observation from riding the carbon flex tail for a few weeks was that I got much more 'propulsion' from backside bottom turns than frontside bottom turns.

Really had me wondering. The board is symmetrical, no funny business there, so why the difference?

I figure it's my body. That going frontside I was somehow absorbing weight through my knees/hips/ankles in a way I wasn't while backside. Hence the board (meaning the flex tail) took the weight and released it when I unweighed at the end of the turn.

Point being, much of the arguments around rigid vs flex are fuzzy, considering your body bends and absorbs energy too.

crg's picture
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crg commented Thursday, 12 Jul 2018 at 1:59pm

That's interesting Stu. I'd imagine the pressure on your frontside has two fulcrum points - the toe joint and the ankle joint as the pressure is directed back up from the water into the leg via the toes. Backside the pressure is straight into the heel and directionally into the tibia/fibula and knee without the fulcrum points creating a dissipation of the pressure and subsequent flex. Maybe? Just thinking out loud.

stunet's picture
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stunet commented Thursday, 12 Jul 2018 at 2:07pm

Pretty much what I was thinking too, crg.

Less 'suspension' during heelside turns as force is applied through the heels.

ljkarma's picture
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ljkarma commented Thursday, 12 Jul 2018 at 4:06pm

With respect, it aint rocket science. You were riding, I believe, a FLEX TAIL.
Forehand surfing is mostly front foot driven so weight and pressure are toward the middle of your board.
Backhand is nearly all about back foot pressure applied as far back as possible and preferably over the fin if it is a single or over the leading edge of a thruster's rear fin. This allows you to push and pivot off the resistance the fin provides hence more critical /verticle turns can be performed backside (especially on a thruster).
So whatever spring/kick/flex response you experienced (or thought you experienced, as I am sure you have no measurable data that could substantiate your experience) was simply placing much more pressure over the Flex Tail produced some resultant 'give/bend'.
Now as has been correctly articulated in previous posts, that 'give/bend' resulted in less drive/forward speed which probably allowed you to turn more easily and felt good.
I am very respectful of Mitchel and anyone making artistically and creative masterpieces but the physics needed to give one a propulsive forward 'whip' or 'boost' sees me as a complete sceptic until proven by scientific and empirical data to the contrary.

The Shaper's picture
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The Shaper commented Thursday, 12 Jul 2018 at 5:59pm

Cheers Stu, I would have to credit the difference to front foot back foot pressure difference between your front side and back hand surfing. That's consistent with what little I see in the rocker profile that you displayed. This balance can vary to some extent in different conditions but more importantly some boards will cause us to vary that balance often with out knowing that we do. Sometimes this can explain why we are comfortable on a certain style of shape, or not. I can tell the difference watching because I know what to look for. I think Ilkarna (sorry I can't see the spelling) made a similar comment below. There is a good conversation in this but its for another day.

morg's picture
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morg commented Thursday, 12 Jul 2018 at 8:50pm

Sorry to drift off topic but I’m curious if this frontside/backside body mechanics and weighting also has something to do with why some guys have difficulty riding twin fins on their back hand.

The Shaper's picture
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The Shaper commented Friday, 13 Jul 2018 at 7:16am

most certainly. Compensation can be made adjusting variables but even so a heavy back foot surfer will never be comfortable on a twin fin.

morg's picture
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morg commented Friday, 13 Jul 2018 at 1:46pm

Thanks for that clarification, gives me something to watchout for :)

blindboy's picture
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blindboy commented Thursday, 12 Jul 2018 at 4:24pm

I am pretty much an empiricist where design is concerned shaper. What works, works. Explanations without data are all very well but far from conclusive. I have no problem accepting that there might be some slight delay in accelerating out of a turn due to flex in the tail, but the key word is "might". Milliseconds are pretty difficult to measure in that situation so I would be watching the overall performance and listening to what the surfers had to say before deciding it was a problem. A lot of these questions should be able to be answered by mounting the appropriate sensors on a board and linking them to a video system. If anyone has made a serious attempt to do that, I haven't heard about it.

stunet's picture
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stunet commented Thursday, 12 Jul 2018 at 4:33pm

"A lot of these questions should be able to be answered by mounting the appropriate sensors on a board and linking them to a video system. If anyone has made a serious attempt to do that, I haven't heard about it."

Stay tuned for next week's story...

blindboy's picture
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blindboy commented Thursday, 12 Jul 2018 at 4:46pm

Looking forward to it Stu!

ljkarma's picture
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ljkarma commented Thursday, 12 Jul 2018 at 6:06pm

I agree 'what works works', my comments should have been divided into two parts, my fault.
First was aimed at answering Stu's confusion as to why backhand and forehand gave him different sensations. To which the physical difference provides the most logical explanation.
Secondly I question the "propulsion" aspect of Stu's experience simply because the whole thing is just so subjective. I am not saying Stu did not feel the difference forehand to backhand, but think about the variables at play on any one wave and what was he trying to do on the wave that resulted in a feeling of propulsion.
To answer BB re mounting sensors linked to video vision, an 'pressure' experiment has been done using a high degree of technology and by the design team behind the now defunct Solomon Score boards. A more extensive experiment into board flex/torsion/twist was in the pipeline (not by Solomon but partially sparked by their experiment) but never saw the light of day for reasons I won't go into.
The problems associated with trying to measure a range of complex design, construction and performance aspects are massive hugely expensive if one wants serious reliable data.
I also look forward to the next chapter and really hope it provides data that can be used to create some bench marks to build upon by an industry that has always struggled to do any form of meaningful R&D.

stunet's picture
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stunet commented Thursday, 12 Jul 2018 at 6:12pm

Hey LJ,

I can assure you the feeling of propulsion, of getting to the lip quicker than I anticipated, wasn't imagined. It wasn't a lone experience either, but happened on many backside waves over a two week period.

Sure, it can't be quantified, won't be documented in a journal of repute, but 35 years of surfing tells me I felt something I don't normally feel.

Subjective, yes, but to my mind real.

ljkarma's picture
ljkarma's picture
ljkarma commented Thursday, 12 Jul 2018 at 7:14pm

well I respect your position as both a surfer and journo Stu and don't doubt for a minute your experience. But I am not a subscriber to blind faith and it would help if there was some more descriptive information about your approach and findings with your flex week surf sessions.
Like exactly what equipment are you riding/testing and what methodology are you applying.
I am assuming it is at least one of Mitchel's flex tails, but is it only one, dimensions, fin set up and how different is the board to the regular board you would ride in the conditions you experienced the propulsion. Any photos or video or someone assisting/observing?
Not trying to be a dick, just trying to understand the playing field so we can relate.

blindboy's picture
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blindboy commented Thursday, 12 Jul 2018 at 9:31pm

Now you mention it I have a vague recollection Solomon doing some research. I agree this is an incredibly difficult area in which to collect meaningful data ...... which is why I think, at this stage anyway, design has very little theoretical basis and that situation is likely to persist. If I was seriously involved I would concentrate on formalising the evolutionary process. Some designers have been using it for years because they were temperamentally inclined to put the feedback from their surfers ahead of their own ideas. In fact, looking back, those who have stuck to fixed ideas have tended to either be left behind or have been restricted to niche markets. No names but you could take a guess.

The Shaper's picture
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The Shaper commented Thursday, 12 Jul 2018 at 6:22pm

milliseconds or what ever mean something when you think you should reach a certain point but just seem to fall short of it and you just got clipped.
The problem that we have have in loading sensors onto board s at this point is getting exact base line comparisons in the face of all the variables at play. So as you say we have come a long way based on "experiencial" research. Wave pools will help. We are getting to the point now though were millimeters and milli other things are of great importance if we want to truely push the boundaries. You can completely change the way a board goes by painting a lick of resin here and there and blending it in. So getting two hand glassed and sanded shapes precisely the same requires a considerable effort. That's what is required to obtain an accurate baseline for measuring forces. I look forward to this material Stu is preparing to publish.

blindboy's picture
blindboy's picture
blindboy commented Thursday, 12 Jul 2018 at 9:41pm

This is the age of big data and at some point in the future designers may have enough data to work from a theoretical basis but, for the indefinite future, the best approach has to be to keep an open mind, listen and watch. The science of turbulent flow, for example, is far from complete (I think there is a million dollar prize for a definitive mathematical proof of the currently used equations).

blindboy's picture
blindboy's picture
blindboy commented Friday, 13 Jul 2018 at 10:27pm

I think this shows the current state of our understanding. And yep, there's a million bucks on offer if you can prove the equations.

https://www.quantamagazine.org/mathematicians-tame-turbulence-in-flatten...

indo-dreaming's picture
indo-dreaming's picture
indo-dreaming commented Wednesday, 11 Jul 2018 at 5:17pm

Sounds cool but when do we get to see some results from this machine?

Ignore button is ON for Crypto knight

(Really no point entering into any discussion with such a sad bitter abusive old man, so go ahead bait and abuse me all you like)

stunet's picture
stunet's picture
stunet commented Thursday, 12 Jul 2018 at 9:44am

Hey Indo,

Not sure when the results will come out, however they will all be made public. Next week I'm running an article on Marc's fin experiments, and he's putting the results in an open-access science journal. There'll be no hording of knowledge, rather it'll be publicly available for people/companies to use it as they please.

sanded's picture
sanded's picture
sanded commented Monday, 16 Jul 2018 at 1:14pm

Hey Indo/ Stu

I can attest to the results being published which I think is a good thing, I just had a great convo with Marc about testing some of our Australian made surfboard cloths and Hybrids and also testing the most common imported cloths (which go through a different treatments) to see the difference , first thing he said was if it was ok to publish in open-access journals , which we are happy for him to do!

CryptoKnight's picture
CryptoKnight's picture
CryptoKnight commented Wednesday, 11 Jul 2018 at 11:24pm

'but would suggest that the key difference between surfers rests in their ability to maximise the energy input from their muscles. This is achieved in two ways. The first is timing or judgement. The second is speed of movement. The first you can learn, the second not so much.'

I like it. Technique. Speed. Strength. Power. Flex, flexibility. Drive. Performance. Durability. Glutes. Train 'em. Don't ban 'em.

Nah, nuthin's better than a scientific, highly developed, cutting edge craft, piloted by a dud in boardies!!! In a nutshell!!!

Shave ya head by all means, not ya glutes but!!!

tamtu's picture
tamtu's picture
tamtu commented Thursday, 12 Jul 2018 at 9:12am

Great article!

I'd be happy with a subscription price increase if we get more stuff like this :)

morg's picture
morg's picture
morg commented Thursday, 12 Jul 2018 at 8:42pm

It would be great to know what difference design flex and reflex could make to a surfboard for average Joe. Really good surfers are aware of the subtleties in their boards where as your average punter tends not to be. A lot of competent surfers may not be aware of the flex in their surfboards or may not turn with enough force to make or feel a difference. An example would be that cruisy surfer who can't get it together on the latest and greatest thruster, but has a great time on a fish or Malibu. I know a few guys who are a bit like that with different surfboard fins. To them the fin either works or it doesn't, and if they try a few similar ones they are at a loss to be able to make a genuine comparative judgement.

Mango Carafino's picture
Mango Carafino's picture
Mango Carafino commented Thursday, 12 Jul 2018 at 10:43pm

More STAR TREK bullshit about the magical surfboard construction.

CryptoKnight's picture
CryptoKnight's picture
CryptoKnight commented Friday, 13 Jul 2018 at 8:53am

'even so a heavy back foot surfer will never be comfortable on a twin fin.'

You've obviously never been down in the desert. A back foot lej used to love stompin' on his MR twinnie tail, and squaring up at bombs.

Then of course, Dane. You gotta have some measurable legs on top of the foot, but, on top of them crafts.

By all means, measure and test, and scientifically understand to the nth degree, the minute variables to test and construct the world's greatest boardies... and crafts, now that stupe and bent have chucked the lid off the box. Peepin' out Pandora's box. Surely now, outside the box, in full view of the world, with all them other, stinkin', foul', inferior, dumb arse useless, breathless, 'thletes (compared ta surfees... outside the box), ya gotta bring some 'thletin stuff, from inside Pandora's box out to the table(s), and scientifical charts and stuff.

Back foot stompin' ya reckon. Not hard to test.

Please, please, please go easy on our extremely tiny 'lympic surfee 'thletes, on them scientifical extremes... and crafts!!!! Please, the poor little blighters... please, please don't push em to the max!!! Boardies forever!!!??

But wait... before ya go scurrying back into the box, again, and permanently, scientifically Bumax Ultra the lid shut...

CryptoKnight's picture
CryptoKnight's picture
CryptoKnight commented Friday, 13 Jul 2018 at 3:34pm

OOOOOOOOHHHH NNNNNOOOOOO!!!!!!!??!!

Well, it was bound to happen. It seemed like a great idea, hurlin' the lid off the box, and peepin' out. But, opening Pandora's box is a double edged sword. Testin' and chartin' and recordin' and measurin' and flexin' everything in sight can bring immense joy, but, OOOOOOHHHH NNNNNOOOOO!!!!!!!!

As you can see, the International Olympic Committee has blocked the Swillnuts!!! Banned 'em!!! And simultaneously sent a message to slattseys's pond!!! Bent flunked the follicle testin'!!!!? Its kango's and co's worst nightmare come true!!! The riff raff, the bludgers, are still fuckin' up surfin'!!!

Leave our 'elite' 'thletes, 'these kids', alone!!!! They won't be submittin' to ya farken', stinkin, useless, loser tests!!! And it is possible to get that unbelievably tiny, ('we make jockeys look like brick shithouses') completely naturally!!! Its enough to make ya reach for the ayahusca!!! Leave our kids alone!!! Damage control... Rosie!!!!!!???!

JoeBlowin's picture
JoeBlowin's picture
JoeBlowin commented Saturday, 14 Jul 2018 at 5:00am

Friend of mine down Collaroy way bought a board in the late 70's called an "inside out flexi flyer", was supposed to be the latest thing. It paddled like a dog and basically sunk at the tail due to lack of foam in the tail area. What I have learned from surfing about 4-5 days a week and making my own boards for the last 10 years is, (I started surfing 44 years ago by the way, didn't catch many waves then because Sydney's beaches were crowded and the water was full of thugs) that the most important thing is catching a wave in the first instance. Most people will struggle to catch a wave if the board paddles like a dog. Most people should not be buying boards that professional surfers use, as pros compete with only two people in the water and are much fitter than the weekend warrior. I make a board using Bernoulli's principal to shape the rails as I surf a very steep break. My accuracy in shaping is average, around 1/16 of an inch. I have experimented with a few rockers and find that there is one rocker that works brilliantly on just about every size board, great paddle power, great early lift from the concave, great rails that grab the steepest face and it flies across the face of the wave quicker than any short board out there, thanks to a double concave and V that releases the water brilliantly. 6 and 4 on top and 6 on the bottom, no idea about it's flex. I'm no expert when it comes to making boards. But I do know you have to catch a wave and plenty of waves on more than few days to really test and feel a board and the wave is such a variable. How are you going to make something so subtle in to something so tangible, when there are so many variables for the majority of surfers? Would be okay if you used Slater's wave pool, but not really viable for most people I would not think. Plenty of old blokes catch plenty of waves along the Gold Coast because they are not sucked in by the marketing of a new product and choose a little more volume over marketing. I would think more volume would mean less flex, but I'm no physicist. Are we over analysing?

The Shaper's picture
The Shaper's picture
The Shaper commented Saturday, 14 Jul 2018 at 7:40am

EXACTLY Joe. More volume is an increasing trend for the average surfer so where does that leave flex. We have to face it the "high performance" market, as we like to think of it, is a very small corner of the universe. Lots of comments in that direction on this thread. Stu throwing up articles like this stimulates a bit of interest and conversation either way and its interesting to see what people are doing. Dude that pays good money just wants it go forward turn and not bog in flat spots.

stunet's picture
stunet's picture
stunet commented Saturday, 14 Jul 2018 at 8:57am

I don't doubt that assumption - i. the average surfer just wanting something easy to paddle - however, while anyone can read them, these articles are aimed just that bit higher, at lifelong surfers who care about surf design, history, and culture, who want to improve their skill or just sharpen their knowledge.

The results don't have to be literal, even if it only gets those readers thinking about their boards in a different way then I'd say it's worth it.

Appreciate all your input too, Shaper. I learnt a lot from your posts.

ljkarma's picture
ljkarma's picture
ljkarma commented Sunday, 15 Jul 2018 at 12:11pm

I trust your forthcoming piece about fins will not be just another version of the story in the mainstream Sunday papers today titled, "Surfers hang ten with 3D printed fins", about the dear prof Marc's new "crinkle cut fins and how they 'tested ' them at macaronis having "we had a ball" and "it was quite constructive"
Well of course you had a ball playing with fins a Maccas (at whose expense BTW) and to able to conclude it was constructive is mindblowing stuff that make the moon landing look boring.
And of course there is the not too subtle mention of commercialising the "crinkles" and the joke claim that this is the first time "research and data on how different fins perform".
Look forward to reading SN take on what appears to be a commercially driven hoax.

ljkarma's picture
ljkarma's picture
ljkarma commented Sunday, 15 Jul 2018 at 12:11pm

I trust your forthcoming piece about fins will not be just another version of the story in the mainstream Sunday papers today titled, "Surfers hang ten with 3D printed fins", about the dear prof Marc's new "crinkle cut fins and how they 'tested ' them at macaronis having "we had a ball" and "it was quite constructive"
Well of course you had a ball playing with fins a Maccas (at whose expense BTW) and to able to conclude it was constructive is mindblowing stuff that make the moon landing look boring.
And of course there is the not too subtle mention of commercialising the "crinkles" and the joke claim that this is the first time "research and data on how different fins perform".
Look forward to reading SN take on what appears to be a commercially driven hoax.

ljkarma's picture
ljkarma's picture
ljkarma commented Sunday, 15 Jul 2018 at 12:11pm

I trust your forthcoming piece about fins will not be just another version of the story in the mainstream Sunday papers today titled, "Surfers hang ten with 3D printed fins", about the dear prof Marc's new "crinkle cut fins and how they 'tested ' them at macaronis having "we had a ball" and "it was quite constructive"
Well of course you had a ball playing with fins a Maccas (at whose expense BTW) and to able to conclude it was constructive is mindblowing stuff that make the moon landing look boring.
And of course there is the not too subtle mention of commercialising the "crinkles" and the joke claim that this is the first time "research and data on how different fins perform".
Look forward to reading SN take on what appears to be a commercially driven hoax.

The Shaper's picture
The Shaper's picture
The Shaper commented Monday, 16 Jul 2018 at 12:19pm

Thanks Stu, yes I get that.
I love design and I love working with people who also appreciate it and respect the considerable effort that goes into it, a rare thing in these days when the craft is treated as a commodity by the broader market. So I appreciate what you are trying to achieve here and of course the comments of all those who contribute whether they agree or not. Keeps it interesting.

blindboy's picture
blindboy's picture
blindboy commented Saturday, 14 Jul 2018 at 9:03am

Here’s one “dude” who wants a hell of a lot more than that. The trend to increased volume also needs to be seen in the context of the demographics. My observation is that people are sticking with standard sized short boards much longer than they were 10-15 years ago. There is always a trade off between paddling power and volume but the advantages of adding volume are generally over stated. If you are a weak paddler or lack positional sense in the line up you can add a lot of volume for a very small increase in wave count.

JoeBlowin's picture
JoeBlowin's picture
JoeBlowin commented Sunday, 15 Jul 2018 at 6:20pm

I agree that volume is not the ultimate. I've watched this guy on what looks like a 10' mal about 25" wide at D'bah and Snapper. He's only light and fit looking, but he can't catch much. The board is just too big. First thing I told my son he needed to do when learning to surf was, paddle, paddle and paddle. Doesn't matter how much volume you have, if you can't paddle you won't catch a wave. What I do believe is that a little more volume, does get you in position quicker when the bombs come in, but still doesn't mean you will catch the wave all that much faster. But the funny thing is, you can never see how fast your board paddles in comparison to others because you are laying on it. But you do know it's working when people keep saying, "Fark! I didn't think you'd get on that."

Ash's picture
Ash's picture
Ash commented Monday, 16 Jul 2018 at 12:41pm

A little more volume can get you on the wave earlier, which is a huge advantage. That alone can buoy confidence, alleviate frustration from hurried take offs and help to set up the next bit earlier.

batfink's picture
batfink's picture
batfink commented Sunday, 15 Jul 2018 at 1:15pm

Great thread. Enjoyed everyone's input, even the ones suggesting that more data will get them somewhere. That's a road without end, too many variables and what works in one case will not work in another.

Alas, as in life, we are all alone. Have to work out what works for me where I surf, but these discussions are great signposts along the way.

Joe blowin, I have come to similar conclusions that extra foam is good up to a point. Has lo be a good paddler for your fitness and body type and rocker seems to be the other key variable apart from foam.

And if Stu was feeling the flex on his backhand I'd be taking that as gold standard data and work back from that.

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