nice comment … shape what your customers need to help them in their quest for enjoyment…but dont shape them what they want ,coz most surfers dont know whats good for them…if a customer wants a board you know wont work for him or hes been misinformed dont do it, better to never build a bad board …dont forget you the shaper are always to blame …thats where all this knowledge comes in handy ,the more you learn and understand the better success ratio you get … regards BERT hey halycon ill send you an email …you sound like a real switched on dude…
NACA/NASA doing planing hull testing: who’da thunk it. However, searches of http://ntrs.nasa.gov/ ( the NASA reports server ) and http://naca.larc.nasa.gov/ ( the NACA tech reports server) for ‘planing hull’ produced mostly either studies of deep vee bottomed stepped hulls ( similar to the cited report) , completely immersed flat plates, airship hull studies ( dirigibles, mostly ) and stuff like landing characteristics. Then there was http://naca.larc.nasa.gov/reports/1948/naca-tm-1139/naca-tm-1139.pdf ; a mathematical treatment, though mostly concerned with theory. http://naca.larc.nasa.gov/reports/1954/naca-tn-3233/naca-tn-3233.pdf - similar, though also concerned with applicability. Note that while these do deal with lifting surfaces treated as flat wings ( wing undersides ) I dunno that these are applicable to hulls of a very different aspect ratio, curved plate form and curved water surfaces which, while perhaps almost conforming to hull curve, strike me as they’d involve some considerations explicitly not covered here. While these are peripherally useful, more on-point information is obtainable such as http://naca.larc.nasa.gov/reports/1936/naca-tm-795/naca-tm-795.pdf ; Similitude in hydrodynamic tests involving planing. The problems of using models in planing tests are addressed. If one passes from the model to a hull of linear dimensions n times greater, the speeds are connected by the law of mechanical similitude. The normal forces given by the hydrodynamic equations (perfect fluid) also follow the law of dynamic similitude (Reech’s method) and are multiplied by n(exp 3). A series of tests were performed and the actual results were compared to theoretical results. Quite useful, I’d imagine, in designing one’s tests and scaling the results. http://naca.larc.nasa.gov/reports/1958/naca-tn-4294/ ; Effects of nose shape and spray control strips on emergence and planing spray of hydro-ski models - interesting, as these are most similar to surfcraft hulls. However, the loading is considerably greater than would be encountered in surfcraft, give or take handboards. Still, useful and may shed some light on variations in surfcraft design. Here’s a beauty: http://www.nap.edu/books/NI000511/html/ Twenty-Fourth Symposium on Naval Hydrodynamics at the National Academies Press. A veritable cornucopia, structural stuff too. Lots more, though not limited to naval/marine stuff by any means, at http://www.nap.edu/ …only problem is, well, remember the definition of a dullard: someone who can look up just one thing in an encyclopedia. This site is dangerous. Thanks for the pointer. Good stuff. doc…
Wayull, another advantage of a camera is it gives the girlfriend something to do at the beach, besides reading cosmopolitan and coming up with new ways to blow one’s hard-earned dough. Multiple plusses. Luders Bands - been a long time since Mat Sci 101, had to look it up. Interesting, is this kinda like treating the resin as a homogeneous item independant of the cloth matrix or treating it as a system with strain elongations in the resin before the tensile limit of the cloth is reached? Or am I misunderstanding? I’ve seen a number of tri-axial cloths, don’t recall the weights, but I suspect that the carbon tape approach might be best, not constrained by the cloth characteristics at all and it can be added later as need be or desired. Putting it on top of cloth also gives a better bearing surface. Have to think about what kind of patterns would work… also, glassing on the bias might have some interesting results, the 45 degree orientation you mention, though that’d take what, 12’ wide or more rolls of cloth to do a 9’ board… impractical. A ‘don’t raise the bridge, lower the river’ thought. If it’s difficult to tune your tensile characteristics, approach it in another way, by tuning the compression characteristics. Corrugations of varying depth and profile in a stringerless board, rail to rail, that could ‘accordion’ to give you the desired flex. Glassing it would be a beyotch, vaccum bagging would mebbe be the only way, sanding and polishing bloody impossible ( vac bagging again sounds good) and you’d need a full length deck pad…hmm. Prolly not economical to produce or even close, but interesting to think about. damn, this is fun.
Bert, KR, hope you guys don’t mind me combining replies here. I’m in agreement that there’s a hell of a lot of empirical, experiential knowledge out there, the thing is that it’s all kinda anecdotal; “I tried this and it did that” with not a helluva lot of understanding of the ‘why’ of it. Testing what’s known, learning and explaining it, that’s kinda important, y’know? Getting some kind of understanding so that we can maybe go beyond what’s known. The mass of theories of wavecraft design we have now, well, you’ve all heard them, and half of them are kinda questionable, to be kind about it. I’m of the opinion that the incremental, one variable-at-a-time changes Bert’s insisting on are the only way that any real understanding can be gained. Full size tests would involve hundreds of boards, almost identical, which would get horribly expensive, let alone how the devil one would get reasonable readings of data that could be organised in a meaningful way. Though the snap-in sections KR mentioned ( damned good idea, that, and not just for tests ) has some very interesting possibilities. Dunno if anybody is familiar with this, well, other than Herb and me, but the really high end gun shops used to have what was called a ‘try-gun’, where the expert at the shop could adjust it to a perfect fit for you and then have your custom shotgun made just right for you. How about a try-board, with different rails, tails, fins and so on that you could adjust a little and let the customer, with some advice and fine tuning from the surf shop guy, see what worked for him. Testing methods…yeah. Straight-line tank tests are fine for simple straight line drag, but how the devil to do tests on how a board turns and get useful information out of it? And there’s others. Very complex problem. KR has brought up something important: you name it, somebody has tried to surf it. Anything this side of a cinder block ( and if somebody has surfed one of those, I don’t wanna know about it) , you can find somebody that’s not only surfed it but they will happily tell you that it’s the best thing to happen to surfing since cold beer at the beach. Trick is finding what really does work better. So many boards sold ( and ordered) are based on what pros are successful with and the average Joe Jamoke will be miserable with. And the pros can surf damned near anything effectively (coming next year, the Slater Model cinder block, with five holes in it and organic concrete) but it doesn’t help the rest of us any. Sure doesn’t help me; they don’t have an over-50 bald gimpy fat man division with world champ signature models. So, somebody comes into my shop, looking for a new stick. He wants something just like the pros use ( he’s wrong, of course) and I have an idea of what I think will work best for him ( and I’m probably wrong too ) and then there is what actually will work best for him…and that’s the tricky part, we don’t know yet what makes a surfboard tick in a systematic way. argh…it was easier, being a monkey beating on a typewriter at random. Oh well… got plenty to think about…
im starting to see a common line of thinking here…i see it out on the street as well, just because some people dont understand something doesnt mean everyone doesnt understand it…one of the things i do for a hobby is play with fast cars nitro funny cars to be precise …these things do 300 plus mph they can go from 0 to 160 mph in 1 second and will do the quarter in 5 seconds…if doing modifications to the body for a little more down force or changing the angle of attack on the rear wing …im tellin ya my maths needs to be right coz if i make a mistake peoples lives are at stake …i hear people say stuff like "who really knows " its just trial and error ""or yea he just got lucky "now as smart as the mechanics are ,the dynamics of whats happening with the body at 500 kilometers an hour is out of there grasp ,but just because i dont fully understand the fuel mix or what timing the magnitos need to be set up at or what fuel pressure needs to run because of atmospheric conditions …and so on doesnt mean that no one knows … you guys are looking for numbers and data and something tangible to understand, and its like trying to understand the dynamics of any extreme sport down hill skiing or any number of sports dependant on equipment the real knowledge of whats happening is in the hands of the people doing it …it exists but unfortunatly not everyone will get a chance to even gain access to the knowledge…theres guys out there that consistently produce good boards for a variety of different people and different needs …they have gone out there and experienced it …and they know ,they know whats going on …but the problem is people who dont understand cant tell the difference between the fat penguin and real performance equipment …and you dont know whos telling the truth and you want numbers to help you to understand …and the words trust me just arent quite enough… where am i going with this ???i dono but i do know that all the proof in the world still wont satisfy some people…no matter how obvious it is…and how simple you can make it for them …its just out of there grasp… regards BERT
Tank testing is a great idea in theory BUT… the dynamics involved in actual wave riding make it difficult at best to apply. An example might be taken from paddle boards - an unlimited class paddle board might haul ass on flat water but put it in choppy tight interval ocean conditions (with the same paddler) and a stock board can beat it.
I’m loving this discussion, so many interesting objectives and observations that I can’t not add my comment. Like aircraft wing cross-section aerofoils, hydrofoils have already been scientifically calculated and are available, if you know where to look, and/or have the right contacts. Some of these have been computer enhanced and are available in a variety of chord percentages, symetrical and also asymetrical, very suitable for multifin side fin application. Any qualified engineer worth his salt (pardon the pun) will tell you that flat sided foils are not dynamic. What I’m trying to say is that science knows the density of air and water, and due to years of scientific R+D have calculated proven foil shape characteristics for these densities. Some are designed for efficiency at high speed, some low speed, some for planing and others for displacement. Some are designed for a nuetral reaction under stress, while others for positive reaction, more active or reactive. The choice and outline design of any of these depends specifically on the user and intended use. The theoretical way in which a fin works going through water is much more constant and calculable than the way the board rides on the surface. Some fin profiles will allow great speed but will start to lose laminar flow at very slight changes in angle of attack. Others will allow a wider range of angle of attack before losing that laminar flow, making it have perhaps slightly slower top speed, but being very manouvrable at lower speeds without losing efficiency. In surfing terms, big wave riding, tow-ins etc being more high speed, general wave riding more low speed. Sure you can do a lightning fast slash off the top, but the tail of your board is almost stationary, just pivoting. The surfboard itself opens itself up to a whole different set of rules, governed primarily by its rider. When flying out on an open wave face you have a planing hull, then, when stalling for the elusive barrel you are using displacement. Then as you set your rail into the face to get grip you are using the board as a foil to bite the water. Then comes the intricasies of combining the correct amount of grip using the foil with the right amount of displacement to keep you inside the barrel coupled with the right amount of planing for speed to get you out. This is also where a correctly designed fin system is needed to keep the board in the wave face and travelling in a forward direction, if that’s what you want. That’s why my understanding is that boards are designed using personal experience, which you could call natural science, and the fins can be designed using science. That’s also why a good boardmaker can manufacture a fully functional board for particular people, taking into account height, weight, wave preference and experience. There are so many variables, board size, shape and configuration, and fin size, shape and configuration. And just as important, we must never forget every surfer has incredibly complex individual characteristics. I’d really like to hear a lot more of other peoples ideas on this subject. Greg.
Have any of you seen the movie “A Beautiful Mind”? Which one of us is going to come up with the “Original Idea”? All aspects of surfing can be measured mathmatically. The static aspects are easy, the dynamic a bit more difficult and the combination of the the two attainable. Add the metaphysical and come up with a formula that can be varified and the result will necessarily be real and objective inovation in surfboard design.Until this happens we are destined to contiuous cycles of retro. What the surfing world (the realm of people who ride waves) needs, or any other world for that matter is thinkers not just feelers. I ponder wheather or not Rodin’s sculpture has just finished an intense surfing session?..
your not a mathematician or you wouldnt be preaching at least 3 years of college mathematics and physics(hard shit) to alot of shapers, and thats 3 years only if your very gifted and can actually apply the stuff. Unlike boats and jet planes with cockpits and standardized controls --works the same for everyone. A surfboard mostly defies that kind of analysis. Will this be a Kelly Slater , Shaun Thomson, or Sunny Garcia type of board??? all different styles middle (front and back), front rider, tail rider, etc.
Ahh, back from my epoxy mission. My new insight after stepping away and re-reading all this incredible generation on this thread, I am wondering what will come of it all. Words, with lots of thought behind them. It’s good to know that others are into testing; I have chosen empirical methods (more fun). I am supportive of taking field data and reproducing it in the workshop and analyzing. Testing is expensive. So, I propose some ideas for a “poor man’s” field test. I mentioned Luder’s bands before because I knew that torsion was going to me a major issue of surfboard behavior. I also realized that a huge part of the feel of a high performance surfboard is that it acts like a spring. This spring behaves in several measurable modes. The Luder’s bands is in reference to a project I was working on as a structural engineer/designer. The project was a classified upper stage booster for the U.S. Space Program. Imagine a 20 foot diameter cylinder made out of stainless steel skin thinner than a dime. NO internal structural beams; just a giant pressurized soda can. The prototype was subjected to many kinds of load. The most revealing was twisting the “can”. Bands appeared, spiralling like a candy-cane at 45degree angles. These bands are regions of stress (Luder’s bands are areas that did not polish well, bad for thermodynamics in space and bad for the cosmetics of polished DC10 fuselages at our other Division). Fast-forward to my true passion, surfboards. I came across this self adhesive foil sheeting, remembering the twisting booster wrinkles, I stuck sheeting over the (first time) bottom of a 6’1" tri and my fried and I grabbed the ends of the board. Sure enough, wrinkles appeared almost at 45’s in spite of the board not being cylindrical in cross-section. TORSION. As a joke I decided to try and surf the board to see if the foil would stay on. Well, to my surprise, wrinkles left CREASES in the foil. I was shocked at the possible loads and deflections it may have taken to do this; or, was it a hydrodynamic effect? Several more sheet experiments (on the deck side as well (no hydro effect)) showed the stresses were most likely due to deflection. We tried to twist a board that much on land but could not reproduce the same pattern and amplitude. Then I realized the the board was ALSO bending straight off the tail. Voila, enough slack appeared in the foil to allow a wrinkle to leave a permanent crease/fold/mark. Stress visualization! On a whim, I took 1" wide uni-directional Carbon tape and glassed it into the deck of my board. I tried to follow the load lines at opposing 45degree angles. I knew that Carbon resists tension (like glass) AND resists compression (UNlike glass) which is why I only did it on the deck; reversal loads would be soaked up by the dual-acting Graphite Tape. Taping the bottom would be redundant and less effective due to the dual-action and physical shape of the board. The board had a completely different behavior. It sprang out of bottom turns and was much more “dashy” on the water; kind of crisp like some styros. About this time I was prototyping a water based resin that was very (at that time) “stretchy”. Shapes that I knew worked were boggy, like riding a soft surfboard and having a nose rail randomly catch. I carbon taped a couple of boards at 45’s and the boards went unreal but only during certain moves. Down-the-line speed was higher/different like a swordfish breeching with only its’ tail driving in the water. Anyways, soon after I was distracted with other works so I never had the chance to isolate what was still not perfect vs. what was now going unreal…I know this “feel” is tuneable with various load line patterns and Carbon tape widths. This relates to my comment about Doc’s “muscle wires” laid throughout a surfboard.
see gw is the type of person im talking about in fact alot of you guys have a clue and it came mainly from going surfing…but also an understanding of the principles involved .i agree with tb i think every aspect of board design is measureable ,in fact alot of the stuff i did to measure and calculate design aspects .i already new from experience and the numbers just reinforced what i already knew to be true ,it also took away some of the doubt and helped me to under stand the differences especially at different speeds… plus one shapers comments on flex do not surprise me at all …when we watch slow mo of the green machine (thats our funny car)taking off the whole thing flexes right before your eyes but you never notice when watching in real life…when i first started working on the body it would come back after a run with hell fractures in it and i would be thinking "wow how far would it have to bend to fracture like that ???"when i saw the slow mo footage i was blown away… yes we can get the numbers … whos paying???who will benefit??? regards BERT
I give Paul Cole the same credit. He shapes with 40 years of surfing and design experience the ocean is his test tank. Over 3000 boards that just kept speaking to him untill he worked it out…I have to say this guys hes a real beliver of the “Sink experiment” taps knives and teaspoons and watch the flow characteristics. And yes he too belives the flow properties can be quantified, in the course of designing and refining the FP Paul did the flow calculation with two IBM 128s and crashed them. Now hes not going to say how he got the figure but the answer IS “0” you guys ponder that,I cant explain it. Hey if Paul hasnt done it, maybe one of you can? ---------------------------------------------------------------------------------------------- WARNING WARNING WARNING “TE rave is in no way endorsed or are the opinions of FP and subsiduarys…” The kinetic energy of the wave and the effect gravity has on the object on the incline will over weigh the equation somewhat. So the latent energy available if used effeciently will leave the equation over balanced in favour of nature. The board being the thief of energy will try and over balance the equation to its favour. The wave energy is also being absorbed by the water density, elastisity of the seafloor atmosphereic pressure and no doubt more variables like surface tension and molecular charge states… So its board against nature a continuous cycle of transfers of energy from abunance to deficiet to the next allways trying to balance its self but never succeeding(thank goodness). Ok an answer as ZERO would make me think that the equation is balanced but what does that mean? Has Pauls board not effected the water at all? Of course it has, so why the ZERO? Well the reason might be…god its late and I should go to bed. http://www.geocities.com/wunderboyi/ninetysixpercent.html
Thanks, FDR was right I’m not a mathematician but John Nash was. I used the analogy to push a point. I have been shaping surfboards since 1968 and surfing since 1958. I have been privileged to be very close to some of the truly dynamic benchmarks and watershed moments in surfboard design. I was not responsible for any of them. What I did do however is experiment both physically and mentally on a quest for a desired result. I realize that the desired result is somewhat subjective. I still stand by the claim that “All aspects of surfing can be measured mathematically. The static aspects are easy, the dynamic a bit more difficult and the combination of the two attainable. Add the metaphysical and come up with a formula that can be verified and the result will necessarily be real and objective innovation in surfboard design”. I wonder, are we at a place in design that is about tiny incremental improvements ad infinitum or is there a quantum break somewhere? My thoughts on “0” are these. 1. We know at least by employing empirical evidence that it would un”reason”able to arrive at zero. Believing that flow properties can be quantified and not quantified at the same time and the same relationship can’t be true. 2. The number of variables that the 128 could calculate was exhausted. At this point I am only arguing from a theoretical point, but even at its most rudimentary and primitive state surfing is still an effect of a cause. Before there was surfing there was no surfing. Is there another quantum leap? Yours in opening doors and passionate about wave riding, TB
Cheers !!! I applaude the open mind, the meta physical is the last thread left in physics to be unravelled…Although the Russians worked it out some decades ago…Western Quantum theory is on the very edge of tripping over it… http://www.geocities.com/wunderboyi/ninetysixpercent.html
Good discussion about using real math and data in board designs. From what I’ve picked up over time, the problem comes mainly from the difficulty in measuring the effects of certain design elements of a board with so many variable in the mix, such as how a particular fin configuration/type affects drag on a board or the resistance a particular rail type offers on a particular type of wave on a given axis. But, I have found a paper written in the 70s by surfer Michael Paine for a BA in Engineering in Australia that goes into some of the mathematics in the (somewhat) measurable parts of surfboard hydrodyanmics. Not being any where near well-versed enough to understand most of this paper, I figure I’d put it up to see if anyone else can make heads or tails of it. Also, if anyone has any hard data or more information on the hydrodynamic effects of fins or rails, whether it be any theoretical or known principle or hard data, it would help me and everyone else I’m sure a lot. http://www4.tpg.com.au/users/mpaine/thesis.html#flume1
hmmmmm- perhaps morey was n to something years ago with his air-lift boards…
Yeah I read the thesis about a year ago. If I remember correctly, it is mostly concerned with design aspects for planing in a straight line with no treatment for turning, paddling, etc. Naturally the solution he came up with was a board that would plane, but good luck getting it into the wave in the first place. The paper was informative and had a coherent treatment of the basic physics, but a much more complex follow-up is required. If I had the time I’d see who wants to take a stab at it with me, but I don’t have a lot of dynamic model writing experience, and I have a dissertation to finish or my wife will break my legs. -Chad