You do too much typing.
The blend is a blend of features that work together.
“…too much typing.” Is that like too many words? They said Mozart used too many notes. Hmmm.
Why not collect all the components, put them together and then use the way the water should flow to make them work anyhow…
Isn’t that the tru spirit of invention?
At least that’s the way I like to think.
Sometimes you get a board that takes more time to find out how it works,
but that’s the way to learn to surf and shape better,
just a humble Soul thinking…
That’s how this thing came to life, couldn’t do without it anymore
2006 Soul & Power 5’5 Superturtle 2
Greetz from
soul
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Also fun is to imagine subtracting gravity from a surfer surfing an actual wave.
Impossible. . . subtract gravity and waves cannot be ridden !
without gravity the wave would push the surfer upwards and he would keep going, and going, upwards.
ocean waves wouldn’t exist without gravity though, so we don’t have to worry.
Its the weekend. During the week I do to much shingle popping, nail banging, ditch digging and raking. It a personal thing, I need the balance, especially since there aren’t any waves today (at least to speak of.)
Kevin
PS
If this thread bothered you, you’ll want to avoid my next one “Surfing the Force.”
Plane off the crust and hmmm yourself, Bill.
Funny, Roy. Rather a critical factor ain’t it, the gravity.
I’m with surfding – empirical evidence shows that having a flat bottom isn’t conducive to many high-performance surfing styles, at least as currently presented by the modern surfboard.
It seems that having less going on would reduce waste/inefficiency, I agree with KCasey on that, but the flat-bottomed boards I’ve surfed (and I’m just an average surfer) didn’t offer the level of control I get from modern boards (shaped by competent shapers, IOW, not me).
Perhaps a flat bottom needs to be coupled with other mods to the equipment (radical new fin design/placement, board design, hydrofoils, trailing impeller arrays, who knows) to have the best of both these worlds?
i always thought that reduced surface tension where flow may be exausted, increases speed
you know when you float a pin on some water and drop detergent behind it, the pin shoots off.
maybe your right, and it doesnt have much effect flows that large/turbulent.
people insist that a 40 grit finish has more drag then say 600 grit
and you can feel the difference in speed
i havent really seen/felt any evidence which is why some of my personal boards are sanded to 40 grit
okay re your thoery
if you want water to exit away from the rail quicker!
a hard edge all the way makes sense (or perhaps a lMcoy loaded dome design )
a very stiff rail
and very slight single concave if any
as much volume as possible (while alowing the rider to bury it on bottom turns)
and some degree of lift at the rails and tail
what about a bottom surface that is dynamic like a conveyor belt
only it conveys water???
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My whole opinion of board design changed one day when I watched skimboarders slip into waves, and surf them. Skimboards are bottoms - a rail on a skimboard is where the bottom ends, as is the tail. Prior to the experience, this was not the way I had been thinking about surfboards. Like many (perhaps not you), I saw surfboards as a bunch of components somehow blended together - the way customers sort of ‘component shop’ for a board, “I want a really pointy nose, oh, yeah some nose rocker, oou, oou some nose concave too, and I’ve got to have a triple concave, with wings, yeah I need wings, and dude, a swallow tail, definitately a swallow tail. Oh, yeah, flip the tail, that just looks cool. And maybe a little fishy too, so I can surf small days.” These ‘components’ don’t work that way, and its not my impression that enough appreciate this simple fact. (That was an exaggeration. If someone actually did ask for all those things, they would, in my opinion deseve to get them, so I’d recomment giving it to them, prepaid in full of course.)
Well this has been an entertaining thread!
Hey Kevin,
Regarding that skimboard enlightenment you had…did you think about rocker at all? If you didnt, then you dropped the brainy ball.
What if you could have variable rocker on a surfboard?
Thats what contour does for you.
got enlightenment?
ps-good thread!
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i always thought that reduced surface tension where flow may be exausted, increases speed
you know when you float a pin on some water and drop detergent behind it, the pin shoots off.
maybe your right, and it doesnt have much effect flows that large/turbulent.
people insist that a 40 grit finish has more drag then say 600 grit
and you can feel the difference in speed
i havent really seen/felt any evidence which is why some of my personal boards are sanded to 40 grit
Hi Paul, I confess to riding a 40 grit (actually 36 grit) board at present. . . The idea being that if the sanding is done approximately fore and aft a micro groove effect happens. . . I am under the impression that all those tank tests done with 400 /600 grit etc were done with random orbital sanding or similar, sanding fore and aft is a bit different is that what you are doing? I did 36 grit then 400 grit. . . following the theory that laziness is the fastest route to the truth ? 
That surface tension bizzo is interesting, try some coconut oil (cheap at Binn Inn) on your fins and bottom it is definitely slippery as it dissolves in water. .
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They said Mozart used too many notes. Hmmm.
‘They’ were musically challenged though, Mozart wins.
have you ever watched those little bugs on a pond
they shoot around like mad
they use there leg or something to break the surface tension in the water
and ride it
amazing
i remember watching them for hours
how long would the coconut oil last on the bottom of a board do you reckon roy?
re. sanding
no, i just kind of go pretty randomly
some times i go to wet 60 diamond grit and that makes a pretty smooth surface
but basically outward to the rails more of a diagonal really
ill try the fore and aft thing
anything in the name of lazy!
Hey Roy,
About fore and aft. I sailed with my professor about two summers ago and one of the things he had to do with the hull of his boat was to sand it fore and aft with some fine (I don’t know the grit) sand paper. He says it cleans up the hull from the slimeys and makes it go faster in the water. Any sailors know about this trick?
Cheers,
Rio
I worked for several years at a boat builder specializing in ocean racing sailboats. We did the heavy sanding with big blocks (2 sheets of sandpaper), fore aft and 45 degrees. Finer grits we always sanded with random orbital sanders and then by hand with wet sandpaper ( a messy job with graphite filled water dripping down your arms and into your face). No fore aft. It was more about getting a fair shape and some race bottoms had zero sanding marks, fore aft or otherwise.
About the surface tension- it was either during the last America’s Cup or the one previous that they were experimenting with a rough finish. The idea was that the surface would “grab” a film of water (known as the boundary layer) and then that water becomes the bottom. Not sure if they’re still doing that though.
On the board I’m working with now I’m putting an all flat bottom, but that is because I’m vac bagging and am not sophisticated enough to do a Bert style contour mat. When I searched "flat bottom " on the site to consider it merits or demerits I did find this quote- from Bert himself,
“I always end up back at flat coz it’s a reliable, all purpose bottom that handles the widest range of conditions.”
If you want a little (or a lot!) of background on Kevin’s thoughts, head to the Archives and search “Rocket Science”. Unfortunately, Kevin’s great graphics have not stood the test of reformatting. If you can toss out your preconceived notions of how a surfboard works, and try Kevin’s explanations, you’ll find that the truth will set you free. Engineering and science are often counter intuitive. His use of planing theory on a surfboard essentially explains why somethings work and others don’t on a board…
Welcome back Kevin.
Kevin, in your SK titled propulsion you depicted the wave as having a flat face. If in fact the wave did have a flat face and the board did ride on it with both rail running as you depict then a flat bottom board with be the call. I believe that since the face of the wave is an ark, then a board with a lot of belly fits into the wave better. Also as we all know our board do not ride flat on the face of the wave infact once we are up and going down the line less then half of one side of our board is in the wave. I do not think we should look at skim boards, airplanes, or sail/motor boats when we are talking about waves, and riding them on a surfboard. Skim boards are made to run on the little bit of water that runs along the top of the sand, which is very flat. Airplanes go through the air not the water, and boats go much faster then surfboard, so different rules are in place for them. We as surfers/board builders need to make up our own rules. Kevin you have spent a lot of time thinking about this, and put down your thought very well. I would love to hear your thoughts on belly. TK AL
I agree.
I’ll ask for your patience regarding my illustrations. I chose to start simple, with the intention of adding complexity slowly. For example, in my next post I was going to give the plank some rear rails, and argue what impact they would have on the resultant force and lines of maximum pressure and spray root, then rocker, etc. And you’re absolutely right about the shape of the wave face and the relationship of the board to the wave. So, please don’t hesitate to alter the diagrams, and hopefully post them.
Also I agree with you’re analysis of skimboards as they were originally used, but the new breed of skimboarders have taken skimboarding a lot farther. They now, literally slip right into the shore break and surf it - as in, on the face of the wave. Watching their 3 to 4 sec rides is a real lesson in minimalist surfing - it appears that all you need is a bottom.
Also, I agree with you about the ‘gravity’ sports, hull design, water skiing, wake boarding, skateboarding, etc. The dynamics of all these sports do overlap with surfing to a degree, but surfing is unique among them in that the power source -i.e. the means of propulsion, comes from the interaction of the bottom of the board with the flow of water in the wave. In surfing, role of gravity is quite different than in ‘gravity’ sports, and the other sports you mention. Surfing can be, but usually isn’t a sleigh ride.
I’m not exactly sure what you mean by ‘make up our own rules’, my guess is that you meant ‘discover the rules’. If so, I agree. But physics is physics, and finding out how other related phenomena work can usually tell you a lot, if only that such and such thing is not important. Stavitsky’s treatment is a good departure point, especially visually, and with respect to some language. Stavitsky did not try to apply his analysis to surfing. Nor am I other than as a departure point.
As for belly, it’s a term that really requires explanation. It’s sort of a way of describing the effect of forward and rear rocker without much in between. Some people see belly, others see rockers and ‘flat sections.’ The term also tends to come with the baggage that ‘there’s more than usual’. If you mean surfboards with no discernable ‘flat’ section, or ‘flat’er section then let me know, a picture of a cross section would help (if you’ve got one.).
In general however, assuming that what you meant is ‘no discernable flat section’, belly, like rear rocker, has a way of adding curvature to the rear rails, and can therefore have a real impact the way a board handles turns. The other impact ‘belly’ (in this usage) can have, in my opinion, is on power generation.
Like too much rear rocker, for that matter like too much of just about anything, too much belly, has a way of giving a surfboard a sweet spot – the board does ride well from any other position, or strange things start to happen like popping fins when you shift around a little. In my world, the only times I tend to see a lot of ‘belly’ (as defined above) is on semi-guns and modern competition longboards (and possibly old surfboards) The objects of the application are slightly different in either case (aside from old longboards), but it’s still tends to be about rear rail curvature (turning) and power generation.
I’d love to take this further. A diagram would be nice, if you’ve got one, or could make one.
Kevin
Do you mean a bottom design that gets rid of the exhausted flow, or the spent flow?
Yeah, I don’t know about something that would require a power source, but optimizing the effect through design is a great idea, a really important idea. as far as I’m concerned. So far, the easiest way to do it seems to be by placing nothing in its way.
But hell, go for it.
Kevin
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Also, I agree with you about the ‘gravity’ sports. . . . The dynamics of all these sports do overlap with surfing to a degree, but surfing is unique among them in that the power source -i.e. the means of propulsion, comes from the interaction of the bottom of the board with the flow of water in the wave. In surfing, role of gravity is quite different than in ‘gravity’ sports, and the other sports you mention. Surfing can be, but usually isn’t a sleigh ride.
Kevin
There is very little difference between a sleigh ride and a wave ride. . . a wave is a sloping surface and so is a mountain. … . they both interact with the bottom of the vehicle, and both are ‘gravity’ sports . . . the means of propulsion in both cases is gravitational potential energy, the difference between the two is in the way that gravitational potential energy is imparted to the vehicle. . . in surfing the ‘mountain’ is constantly moving upwards relative to the surface of the earth, but the direct means of propulsion remains the same as if the mountain was not moving.