I like your explanation Hal, too bad that T.E has to slink around an hock his wares unwanted at every turn. Lets ignore him. P.s i’m in S.C i might have you make me a fin. I’ve never had a costom fin and the prospect is exciting.
Whew, that was a lot… Here it is in plain physics: Energy in = energy out plain and simple. The less energy the board transfers to the water, the faster the board. imagine a board cut in half at the concave. the numbers represent the energy loss to the water for each small unit area of the bottom of the board. The s represents the stringer, r represents the rails perfectly flat board: r1 1 1 1s1 1 1 1r - total energy lost= 8 fastest (if you could surf it) less rocker board: r5 5 5 5s5 5 5 5r - total energy lost= 40 faster concave rocker: r7 6 5 5s5 5 6 7r - total energy lost= 46 fast more rocker: r7 7 7 7s7 7 7 7r - total energy lost= 56 slower Simply running down the line: flatter is faster http://www.berlin-gmbh.com/
Dale`s right. No question- concave can be much faster at warp velocities. The problem for stiff boards is control. In the old days it was easier to end up going faster in bigger choppy waves by shaping lots of convex into a board. All you flat bottom believers should take a close look at some of the fastest tow-in boards. Wake boards too. Those old hydroplane builders have had it going on for decades. Concave is happening.
eddie eddie eddie…id love you to come and experience warp speed with me .every year for the last 15 i go to a place in our northwest dessert area here in oz, it took me 7 trips to this place to work out how i was gonna come out the end of a churning ,triple lipping,ledging ,coral bottomed ,15 second barrel section…you guessed it, flat is fast,i been so deep at this place that everything goes dead silent…all you hear is your rail gently lapping the water as all sound is blown out in front of you …every year i would take a full quiver for the first few years i couldnt get out of the barrel…just got deeper and deeper and gone…so after trying all the various configurations…all the flat bottoms i have surfed there have never let me down…there are so many ways of regaining control and changing the performance characteristics of your board with out comprimising speed…tails ,rockers ,rails,outlines,fins,…you want to gain the most,lose the least…crunch the numbers…it can be done…
Bert, I’m always looking for descriptions of our experience in the tube. Most attempts fall short, and while no words can describe the experience some come close. Your description is up there with the best of them. I’m saving them. Thanks, Rob Olliges
after some of my posts .a few of you may get the feeling im against concaves…far from it ,like gw and halycon mentioned ealier different curves for different waves, so many waves are so different, thats the exciteing thing about traveling and surfing the challenge of conquering new waves with the equipment that you have designed for it and the learning that comes with it ,the knowledge you gain is priceless ,but regardless of what works where and why with who on it .flat is still fastest .and if one wave calls for maximum down the line speed to make the pit so be it …while other waves require you wash off speed to get covered .or hang high off the take off to get slotted so you need something to hug the face right off the mark without sliding to the bottom or falling off the face …every wave has as own set of rules to get the best out of it ,i have really enjoyed this thread so far and im really stoked that others out there have the same passion as me for refining and surfing there equipment in the quest for understanding and a little excitement along the way… regards BERT
I think this thread will only serve to confuse some people Flat may be faster However concaves and channels lower entry and exit rocker Throw in hard or soft rails fin configurations outlines foil overall board displacement surfers ability ect. And you will see that there are many ways to achieve a desired effect No one particular board is the best at anything. Shape what works for yourself
Want to go fast? To all flat bottom believers: “the fact is if you look at pictures of people riding paddle boards down the face once theyre really going down the face only the very back of the board is really touching the water on the drop. That is the business end, we put all the horsepower right where youre standing with a full concave and they really do work. They do go faster.” Dick Brewer - www.juicemagazine.com/DICKBREWER " I’ve got a lot of opposition and ridicule about concaves. Over the years, people have often rubbished them. Then they go and ride one, and they come back in and they’re all over you like a rash. Because concaves really do work. They’ve been a quest for me. I’m still experimenting with concave technology because it’s the most exciting development to happen to surfboards. There’s a lot of subtlety involved in them. Even a lot of shapers don’t understand the blending of fluid dynamics that is happening with these boards. Balancing the concaves, developing the thrust while still maintaining control over the board is the challenge." www.outerislandsurf.com/ Mitchell Rae interview “Guns and Semi Guns… J. Blair shapes very soft rails into the catch zone and puts an accelerator right under your feet at the sweet spot. There is a slight concave in the nose and an extremely slight double barrel concave through the belly of the board. The secret to making these gunnier boards turn is moving the fins up further. " surfingsports.com/dick brewer concave tow-in boards “Dick evolved into the Nineties… continuing shaping Dick Brewer Surfboards to try to satisfy the demand on the North Shore. His boards were still setting the “cutting edge” trends with his subtle concave, and single/flat/double-barrel bottoms. Surfers all over the world longed for a Brewer.” www.towsurfer.com/ The History and Story Behind Dick Brewer “Nowhere else in surfing is design as important as in tow surfing. The difference between a good board and a bad board in giant surf can mean the difference between life and death. As Mike Waltze put it: “We all knew from windsurfing speed trials that if you want to go fast, you have to expose less surface area to the water.” That meant riding smaller boards. Kalama remembers Hamilton coming back from Oahu with an 8’2” shaped by Dick Brewer that showed everyone the potential. “We all took a look at this 8’2” that was 16 inches wide, concave bottom, thruster and went, ‘No way. It’s too narrow.’ I think even Laird had some reservations about it. But we took it down the coast to this other place that was about 10 feet. Laird caught a couple of waves and then came in and said, ‘You’re not going to believe it. You’re not going to believe the speed you will get on this board.’ And I said, ‘Whatever.’ So it was my turn, and I got a wave that looked like it was going to close out on me. But two pumps later, I’m around this section and I’m going, ‘Holy shit.’ The board was incredible. It was so narrow and gunny, but it was super fast and you could cover a lot of ground. I’m not sure whose idea it was to make it that narrow. But I think you have to give credit to Dick Brewer for really going way outside the boundaries.” www.kenbradshaw.com/ Farewell To Arms
Arden, These are grand references. Thanx for posting them. No matter where we look in nature things that have great straight line the length ratio increases in relation to width up to a point that becomes nonfunctional. Quickness and turning depend in more filling out the width ratio. Balance is the key but where concaves fit into the picture is really the question at hand. There are some glitches in what I offered above. But clearly there is a place for them in the modern surf-craft performance picture. I have a board that I’m thinking about scooping the whole bottom out to bring it to life cause it’s kinda heavy and needs more lift to get going. I’ll keep dreaming and after I do some shaping I may embark on the project. Off to the fin shop, Rich Mahalo, Rich
some of the latest Brewer tow-in boards – being ridden in SERIOUSLY large surf – have very substantial deep (over 1/2 inch) concaves in the tail section. If you don’t think those guys are going fast and in need of control, think again…
What can I say guys…Check it out and build one you will find FP very balanced design… http://www.geocities.com/wunderboyi/ninetysixpercent.html
I’m with Halcyon, thanks for all the stories and input. Stories of the boards and waves people have ridden, and their experiences, are something I will never come close to. Barrelling WA or grinding Hawaii, even one foot gutless wind-slop. Boils down to having the right board for the right job, then matched with the guy riding it. I lived at St.Leu for a few years, and the boards I made myself to match those waves ended up being place specific. On the best west swell days you needed controllable manouverability to stall yourself into the bowl, but controlled accelleration to get you out, of what winds into, a fast, almond shaped barrel. Those particular boards loved it, and the slim design included a light double concave, combined with rolled vee, among other things. A friend of mine borrowed one once and got some memorable stand-up backside tubes, one main reason being he was about the same height and weight as me. But those boards didn’t go that well in other waves. They showed glimpses when the wave shape was right, but generally a bit frustrating. Hence, work began on another board with different characteristics, and off we go again.
The real recent Brewer tow in boards are super short (under 6 ft.), very narrow and have basically a full length deep concave at around 1/2" depth. Rails are very hard almost all the way through, except for a little softer right at the front entry point. These boards are glassed super heavy, usually triple 6 oz both sides, with big thick stringers for strength. Weight is intentionally heavy to cut the effects of chop at very high speed. The only caveat on this type of design is that it is a dedicated tow in board only and as such is totally free of any flotation requirements dictated by having to paddle or drop in. Therefore, the translation to conventional paddle in boards is not as direct as it would seem. Also, the speeds that these boards operate at are not acheived in normal surfing. It’s almost like Formula 1 race car technology. Eventually, the race car innovations make it into your average passenger car, but usually the form is substantially different than what was first used because the basic application differs so much from racing. Gotta admit, it’s cool to look at and speculate on, though…
I have an old Cypress Garden laminated Slalom Water Ski that might fit the ticket for tow in.
Send photos after you get back from hitting Teahupoo and Jaws on the CG stick…
“It would seem to this humble observer that less wetted surface means more speed. A concave pulls the center section of its facet up off the wetted surface. This causes ventilation and makes the facet more slippery in the center and bite harder at the edges and by not having as much water contact leaves this given facet with less directional stability than a flat surface of equal weight.” I am only a college student with limited shaping experience, but it would seem to me that concaves create more wetted surface. In order for the concave to actually lift from the surface of the water (ventilation) the concave entry would have to be extremely steep. No concave boards I have seen are like this. The so called “lift” surfers claim to feel when riding concaves seems to be due to the increased (pseudo-width) surface area under their feet, providing more resistance to sinking. Play with me here. I’m sick of hearing everyone’s personal (including my own) explanation of why concaves are good. Haven’t there been any scientific studies on this to come up with a definitive answer?
Hey Losos, “It would seem to this humble observer that less wetted surface means more speed. A concave pulls the center section of its facet up off the wetted surface. This causes ventilation and makes the facet more slippery in the center and bite harder at the edges and by not having as much water contact leaves this given facet with less directional stability than a flat surface of equal weight.” That’s a tricky one I know. You’re right in saying that on two bottoms with the same external dimensions the surface area of the one that is concaved is greater than the flat one ~ that’s uncontestable. However a ventilated surface isn’t as wet and an unventilated one. This idea is what causes some high-speed boat hulls to hydroplane. It’s one method of achieving speed and reducing drag. Such a bottom rides higher in the water and less of the bottom touches the water because of the air that is trapped between the bottom of the craft and the water surface; as a result there is less resistance between the bottom and the water surface because as it moves the area under it becomes aerated. I hope this make sense. Of course some real scientist out there may has something to say that will shoot this postulation full of holes (-; Glub, Glub, Rich
what tastes better…apples or oranges? There is no way to separate 1 design element in an equation. we surf different. One design likes flat, another likes concave. This is the final word. You can all go home now.
tw - wouldn’t that be an easy answer to all of this. No wave is like the last and to each his own, but it is agreed that concaves, flat bottoms, and all other bottom contours behave in their own unique way. There IS a best, no question. The difficult part is that determining which one is the best is subjective to wave shape and the overall features of the rest of the board. What I’m trying to find the answer to is the following: what is it that essentially makes concaves work with one design and not the other? Halcyon - thanks for trying to clear things up for me, but I still don’t understand how the ventilation occurs in a gradual-entry concave no more than an eigth-inch deep. I could see the pressure being less in the center of the concave than it is at the rails (therefore substituting less drag at the stringer for more in the rails), but how can the center of the concave be less wet when the entire concave itself is submerged? Just to make sure we aren’t confusing things further by having two separate concaves in mind, I’m imagining a single double concave starting at the mid point and tapering off through the fins. Does this change anything?
Does anyone have a copy of SolidWorks that they could try testing out bottom contours with? An animation would be an excellent resource to Swaylocks and I know the new version comes packaged with COSMOS FloWorks (a computational fluid dynamics library). It would be great to see what is really going on down there.