board flex v. fin flex inter-relationship

General Discussion
21

i like flexi board with stiff fins

but im in to the idea of stiffer rails ands deck too at this stage and flexi bottom

flex in my opinion is loss of energy or untransfered energy. it needs to engineered to bounce back

however a bouncing ball never bounces back higher than the height it was dropped from

and im pretty sure even a recurve bow would lose energy on its return

so to me its about

tension

stored energy

and return with as little loss as possible

rate of return

four factors that are very important but completlely irrelelvent if your not a very good surfer.

so stiff fins for me always

thats why i hate plastic finsystems

they flex to much and you need to baby the board through a bottom turn

22
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For me, none of the above. I prefer zero flex in the board, and zero flex in the fin. That way I'm assured that what I feel the board doing on a wave is a result of the shape and contours I had created, and not some variable over which I had little or no control.

A good analogy I like to use is a longboard skateboard.

Imagine how it would ride if the trucks had no flex. Then imagine how it rides if the trucks have flex. The rider rapidly acclimatizes himself to the flex, and uses it to his benefit. Surfboards are no different.

The real test for this comes not in words on swaylocks but under your feet on a wave. I’ve logged hundreds of hours of surf sessions on my fins, and am confident that few would choose a rigid system over a rotating system if they had the same test riding experience.

You can say that flex always represents lost energy, and to a certain extent that is true. But flex in toe-in ALWAYS represents lost drag, and that is 100% true for singles as it is for the rail fin systems. The finbox has been engineered to provide stiff resistance from the inside rail fin in a turn when you need it, and the least resistance possible when you are in between rails, when you don’t need it. You will never go rail-to-rail faster on a three fin board.

23

A longer skateboard is a good analogy. Take those flexible, responsive trucks and combine them with sensitive, resilient wheels and deck. Add a long, fast course and an experienced rider. Enhance frictional interfaces, i.e. bearings, shoes and deck, wheels and course. Tune it all to function in synergy. Weight and unweight, generating more speed and control than possible with rigid equipment and technique. The result is greater than the sum of its parts.

To those who know how to exploit it, tuned flex represents STORED energy. Consider all the sports equipment incorporating flex that would be nearly (and laughably) useless if they were rigid.

The ocean is a fluid medium, and most of the creatures that live above and below its surface incorporate flexiblity for efficient survival. Observation of nature often inspires emulation, and the creation of craft with similar function.

24
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and does flex in the tail do as much good for a single fin as it does for a thruster ?

Flex in the tail works well with a singlefin, but works more efficiently using a fin setup with horizontal area . . . . which a thruster has.

Horizontal area drives provides drive when the board flexes vertically, like a dolphin tail.

Vertical area is like a a fish tail, and fish flex in the horizontal plane.

The reason why a flexible board uses vertical rider movment more efficiently when it drives through a horizontal underwater fin surface rather than just by using the planing surface of the bottom of the board is that (all else being equal) an underwater foil has a better lift drag ratio than the planing bottom, and so it transmits the energy more efficiently.

25
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??? I don’t know. I’d be willing to bet, however, that flex in a finbox or fin provides an order of magnitude more benefit than flex in a tail. Just a hunch.

Board flex is a way of transferring the bodily movement of the rider into forwards thrust.

The majority of rider effort is vertical relative to the board, and this vertical movement is more efficiently transmitted into thrust via a vertically flexing board (like a diving board ) than it is via a horizontally flexing fin.

.

26
Quote:

For me, none of the above. I prefer zero flex in the board, and zero flex in the fin. That way I’m assured that what I feel the board doing on a wave is a result of the shape and contours I had created, and not some variable over which I had little or no control.

Bill Thrailkill

Shaper since 1958

today i was surfing fun head high down the line right hand point waves …

i was riding a 9 footer , the board was longer than the wave was high , yet i was able to go square off the bottom crack the lip and hook it around to have the nose pointing back to the white water near the bottom then square off the bottom turn and get ready for another one …

alot of crew in the water wanted to see what i was riding and came and asked questions , because its not everyday you see 9 foot of length getting jammed into and springing out of 6 foot of space …

im assured that what i feel the board doing on a wave is the result of the structure and even tho it has no obvious bottom contours , they appear at the needed times under pre determined loads …

all of which are variables i have full control over …

welcome to the next generation …

but it had to start somewhere and we all thank guys like yourself Bill for making it happen …

Bert Burger , not a shaper , but a creator of wave riding equipment , designed to change shape …

B is the closest of the multiple choices …

regards

BERT

27

…good stuff Bert !

glad you’re getting waves …was that at the superbank, or somewhere south perhaps ? I bet you’re glad to have a really good testing ground for your designs too…

was the 9’er a mal , or a more pulled in , gunny design ?

with wood glassons ?

I bailed up a guy here yesterday with one of your boards , a 7’2 with wood glassons that he had bought 2nd hand [$400] at Ross’s . He was really enjoying it . It as in really good nick.

Bert have you made any single fins with the ‘surfburger’ technology ? any with a flexible fin ?

I’d be interested to hear your take on that, please …would it be worth doing [for a one off for you or a mate ] , or not ?

cheers !

ben

p.s. - what is the shortest surfburger you have ridden on the goldie and elsewhere , so far ?

28

…good stuff Bert !

glad you’re getting waves …was that at the superbank, or somewhere south perhaps ? I bet you’re glad to have a really good testing ground for your designs too…

(currumbin) , i think west oz was a way better testing ground in regards to waves , the goldy is way better in respect to marketing …

was the 9’er a mal , or a more pulled in , gunny design ?

(this was it , 9’-2" x 22 1/2 x 2 1/2 )

with wood glassons ?

(not glass ons on this one , i was using the chunkstas i made a few days back with the fcs fit , this board is a demo kicking around the shop …)

I bailed up a guy here yesterday with one of your boards , a 7’2 with wood glassons that he had bought 2nd hand [$400] at Ross’s . He was really enjoying it . It as in really good nick.

Bert have you made any single fins with the ‘surfburger’ technology ? any with a flexible fin ?

( you can see one of my own singles floating around in these pics , its essentially a surfburger , or the prelude to the new surfburgers , with the original construction techniques …)

yes the fin flexes , but not a great deal , just a standard plywood fin …

I’d be interested to hear your take on that, please …would it be worth doing [for a one off for you or a mate ] , or not ?

cheers !

ben

p.s. - what is the shortest surfburger you have ridden on the goldie and elsewhere , so far ?

(6’-4" , my original magic carpet from west oz , goes even better over here …)

here comes another pic of a local grom surfing a 5’-8" surfburger (blake ainsworth)

(say hi to ross for me , tell him that finally he may get some boards from me soon , maybe early next year, feb, march or so …

regards

BERT

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29

All i can say is that is a hot looking mal!!!

that… and… Dam im jealous

Catchya

Ant

30

(say hi to ross for me , tell him that finally he may get some boards from me soon , maybe early next year, feb, march or so …

will do …

Do you have a shot of that 5’8 board please ?

what sort of dimensions ? tail shape ? what fins ?

It looks fun to me

cheers !

ben

31

na sorry chip . no pics on the 5’-8" …

its basically a stock standard nev shape about 18" wide i think by 2 thick , with h2 fcs , which apparently make it work best (which incidentally are similar to my regular foils for smaller crew and which the rocker and flex were designed to work in combination with )

its a stock outline rounded square …

heres another pic of blake and the board from a different angle …

regards

BERT

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32

nice !!

do you have a digital camera now Bert ?!

And tell me , is the bottom of that 9’2 airbrushed ?

…one of Nev’s guys , or vicco Josh , perhaps ??

nice to see some artwork on wood boards !

cheers !

ben

returning to the flex theme of this thread …are the young blokes getting some flex out of their 5’8"s ?

…what has their feedback been so far ?

And , are the fins also flexing noticeably , did they comment ?

33

do you have a digital camera now Bert ?! (had one for a while , couldnt do any informative style posts without one )

And tell me , is the bottom of that 9’2 airbrushed ? (no , its a digital print vacuum formed into the skin , we can digitally customise any artwork , print and form into the skin , i just went to look for some insane designs josh did for kelly , but i couldnt find them , i guess they never got sent to this computer , hey josh !!! if your out there tonight , reckon you could show chip that design of kelly coming out the barrel ???

…one of Nev’s guys , or vicco Josh , perhaps ?? (that particular design was picked off a site that has a data base of designs , like clip art )

nice to see some artwork on wood boards ! (not as much wood in these , wood where it counts and some new ingredients where it doesnt )

cheers !

ben

returning to the flex theme of this thread …are the young blokes getting some flex out of their 5’8"s ? (yes , some very direct comments on flex by a few of the young team guys , things like "it comes off the top like a slingshot " "it snaps out from under the lip like a rubber band "

comments that were new to me , as ive had plenty of my own to describe the boards over the years ,but these were fresh comments from crew new to the technology )

…what has their feedback been so far ? (the feedback has been mindblowing on all levels , i dont want to quote all the comments because it will look like im talking it up …but weve had team riders hating each other and fighting over who will get the small amount of team boards available so far …)

And , are the fins also flexing noticeably , did they comment ? (no flex built into the fins , at least not on purpose (fcs)…

regards

BERT

34

thats a cool photo bert

the angle of the balsa makes it look like a huge concave(optical illusion?)

or is that the flex your talking about

35

Here ya go Chip!

And a couple more of my favourites, just for fun. There’s loads more but its getting late…

Speedneedle

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36

(no , its a digital print vacuum formed into the skin , we can digitally customise any artwork , print and form into the skin

I wanted a closer look …hope you don’t mind , here it is again , only lighter …

…WOOHOOOOOOOOO !!!

ben

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37

I especially love the ‘silver bullet’ one …would I be allowed to post 'em up on the " let’s see some artwork " thread, Josh ?

38

Bert,

I have found that “full control” over most things in life, is an illusion at best. Though like “freedom”, it is one of the fondest possessions of our imaginations. I’m as firm in my belief, as you are in yours. Both of us have a basis of our experience to refer to. For the kind of surfing, or style of surfing I’m interested in, zero flex works best for me. Others may have different opinions, or experiences, and approaches to the same questions or problems for which they seek a solution. Cause and effect isn’t always what out senses tell us it is. You and I can agree to disagree without any difficulty.

39
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im pretty sure even a recurve bow would lose energy on its return

well if you are saying just the pull back and release then almost all( you also have to take into account the spring of the wood of the energy is transfered from the bow to the arrow, but the arrow loses it’s energy as it travels.sinew backing, similar to fiberglass lamination has been used for centuries,if not millenia by bow makers to improve the snap and cast of the bow.

I would bet that it’s not so much as that a board flexs it is how and where. if say the last 6 inches of the nose are flexible does that really affect the turning radius as the last six inches of the tail? and if the board has alot of snap that would really drive you right out of turns where as if it kind of and slowly flopped back it would be crappy creating a spongy turn.

futher more i think blakstah has it right with the stiff fins that rotate. blakstah have you tried the rotating side fins in a quad yet?

40

Ok given that this thread is about the relationship between board flex and fins, can anyone explain to me how it is possible for a vertical flexing motion to provide drive through a vertical fin ? I can’t see how it is possible, any drive provided by a vertical flexing motion must be through a horizontal surface, and thus a board which only has vertical fins really cannot be a means of transmitting board flex into forwards drive VIA THE FINS.

Forwards drive from rider energy transmitted through board flex, in a board with vertical fins only, must be obtained via the only horizontal surface available. . . . the bottom of the board, the fins can’t have much to do with it.

Of course, as I mentioned previously ( Apologies for the repetition) even though board flex can only provide drive through the fins if the fins have horizontal area, fins setups with horizontal area include any multi fin setups with cant, thus including bonzers, thrusters, quads and so on.

I wonder if the reason why the best ‘performance’ multi finned shortboards are always built to flex is because they have so much more to gain from flex because of their horizontal fin area than do single fins and other no horizontal area setups?

comments ?