Hi guys, I’m hoping I can spark up some more discussion about the hydrodynamic theory of surfboards.
So far from reviewing threads I understand that most people consider the generation of lift to be one of the most important points. At low speeds this means hydrostatic lift, buoyancy and trying to “push” less water. At high speeds this means hydrodynamic lift, form drag and planing, etc.
It all seems to make great sense, but to me once you’re up and planing its simply the board travelling over and partly in the water. To me this suggests that its more about helping the water pass under and around the board from A to B as easily as possible, and related to this is the syndergistic effect of rocker, bottom contours, fins and fin placement, and the tail shape. This all seems to get a hell of a lot more complicated when you add in turning and different angles of waves…it seems a lot has to do with how much a board can “dig” into the wave and turn either by dragging in the water, or by other means.
Does it sound like I’m on the right track or am I overanalysing things? Arg!
Yes - you're not off track but it would be much better to just go surfing. What you're asking is like the centipede on it's back in a ditch trying to figure out which foot goes first.
I could give you about ten different text books to help you out on your general topic. However most of the books i’ve looked over are complex. Yes in the case that your talking about its cut and dry, lift and drag but thats a static situations. When your actually surfing there is every factor in the world which creates a dynamic situation. I’ve only taking fluid mechanics so far so i have nothing to really discuss but my professor is also the advisor for the surfboard shaping club i created at my college. We are going to be looking at this a little bit be he said even he has trouble with part of it. Its not a cut and dry science. But im just an 4th year engineering student with one more year for my double bs in Electromechanical engineering. Emphasis on the BS haha.
haha, thanks for the heads up. Letting me know that an engineering academic who advises the surfboard shaping club has trouble understanding the dynamics of surfboard design is all I need to know. That was far more useful that every single one of the previous flippant and dismissive comments.
What I find confusing about surfboard design is how many conflicting opinions you can find when trying to read about a specific topic. For example for “whats faster, a concaved or flat bottom?” everyone had a mixed opinion. I have done a fair share of sorting through specific comments to help my understanding, but seeing as there is a lot of intuitive and try-and-see reasoning out there, its hard not to end up swimming in it all.
Okay, here is a specific question for the others who don’t like vague ones - What do you think would be the fastest board possible (that still has some ability to be turned by the rider to respond to the wave to some degree)?
well the reason its called hydrodynamics, is because every situation is completely different (and the water is moving). Concave maybe be fast for some one heavy thank flat because there more of a mass to move. Thats why so much of surfing is trying new boards out and just finding out what is good for you. When i bought my first new board, i went through three different boards before i decided on one. Not to mention the wave makes all the difference. For example for a big wave, you want your board to be fairly stiff. But even then yes the surface you ride on is the same density, but every wave is a little bit different. Surfing would be dull if it was called hydrostatics. (hydrostatics is a science, but is more about ship design i believe i may be wrong.)
To answer your question you need to answer some more of mine?
Each board has a million factors every inch of the surface area of a board is a factor however we can neglect most of those and come up with the most key factors. Key factor i see are the the curve distance between nose and tail, the cant of the fins has a large play on wither you want to throw big turns or little turns. Also the tail of the board plays a part in how the water flows out from under the board and you can use that to your advantage with different shapes. For example a swallow tail is looser however you can turn more abruptly. ect ect. My favorite board to ride for versatility is the Rusty Dwart. I am a 5-fin lover. If surf is small pop the quad if surf is bit rock the thurster. DWART stand for Double wing and round tail. the Round tail gives it a straight. the round tail is grate for holding in the pockets, how ever you loose it in the flat sections a bit. pin tail is for guns pretty much. Makes the board a straight shooter. ect ect your can google tail shapes to figure out the diffrence.
How big are the waves your surfing? Because every board is slower or faster on different surf.
Small waves - go with a wide fat fish of some sort. The Fishcuit is a sick board to check out. However as soon as the surf gets big its useless.
You want flippant and dismissive? This is flippant and dismissive: You ask a question, I tell you to put Kevin Casey in the search box and press go. Did you do that? Probably 5 years worth of back and forth regarding surfing hydrodynamics by some of the more creative physics/engineering types familiar with surfboards. There's a lot of BS in there too. Probably too much work for you to decipher one from another though...
And lighten up… What Lee said - “flipant…” ??? I’ll say this then, "Dude, lighten up, as has been pointed out here… “Were only talkin’ about pool toys…” Ha!
In all seriousness, you've already figured out that there are any number of opinions on each aspect of board design. Get a loyal Greg Liddle hull rider together with a rider of concave bottomed 5-finners and watch the sparks fly. Beware of test tank/chalkboard/mathematical theorists.... what makes sense on paper doesn't always pan out in the water.
One of the most famous of the textbooks on the subject might be the Lindsay Lord book on the Naval Architecture of Planing Hulls. Again, lots of theory but in actual practice, the stuff that works under YOUR feet on real world waves might not fit the mold.
Avoid 'paralysis by analysis' as in the case of the previously mentioned centipede. Your best information will come to you via direct feedback by riding as many boards as you can get your hands on in as many different conditions as you can.
Keep track of what works for you. I.E. measure rocker with a standardized method. Keep records of your outlines and thickness profiles. Also note what fins work for you and where they were placed on the boards.
I have a copy of an excellent primer book by George Orbelian. He has already taken a ton of detailed measurements of various semi-current board models and lays it all out there for anyone interested. His writing on design theory is as good as anything out there. One of the famous magazines hired him on as a design consultant with his own column several years back.
Dave Parmenter has also done some nice work on board design including specific measurements and feedback on each design.
Contact me via PM and I can let you borrow the Orbelian book. IMO it will get you farther faster than Lord's book or the one by James Kinstle. Or you can just buy a copy of your own.
Get a Jeff Alexander Gemini. Beware that it is patented if you’re looking to do more than ride it.
Greg Griffin makes some very interesting 5 fin boards that are fast and controllable.
Maurice Cole is doing very interesting things with deep concaves right now.
All different designs, all fast.
But I ask you… what do you mean when you say “fastest board possible”. There are so many ways to generate speed on different parts of the wave. Every wave has a speed threshold that you probably can’t go past, and the size and shape of the wave matters as well. Some boards can trim or glide faster than others, but then they may not get as much speed from turning as others.
The book is "Essential Surfing." It turns out I have two copies. One is signed to me by George who ended up having to put up with me on a surf adventure several years back. He, his wife Marsha, his two twin sons, and I were passengers on an airplane ride to Baja. It just worked out that way.
If I don't hear from Capt Caveman pretty quick I'd be happy to send you the extra copy. Just PM me your mailing address if you don't have a copy yourself.
It really is a good book on surfboard design and construction. Even if it is a bit dated at this point (mine is third edition, 1987), the data is still valid IMO.
Yeah i just asked my school to order that book and the surfboard design book. I also asked for a surf science book. I’ll let know how good the surf science book is.
