I may be right, I may be wrong but it seems I remember the "Speed Bead" as one of Tom Morey's brainstorms? He wrote an article about using various techniques to deflect water flow resulting in less wetted area which, in theory, resulted in more speed. He proposed using silicone sealant, wire beads inside folded tape, etc as methods to build speed beads. A sharp edged strake or even vee apex might accomplish the same thing but I'm not sure the original premise (less wetted area = more speed)is even valid. My recent experience with bigger boards would lead me to believe that MORE planing surface might increase speed. Proper rocker and contours are important. For what it's worth, both of my 10' Skip Frye gliders have nice speed and glide in smooth conditions but are so flat in rocker that in bigger waves with any kind of chunk, they can get squirrely and slap happy. A 9'6" Eaton with frontal belly, moderate nose rocker and exaggerated tail vee right through to the tailblock has not had those problems even in bigger waves. When being pushed through a bottom turn, the Eaton seems to utilize the tail rocker and exaggerated vee to rock back and bank. Shortening the length of board in water (for maneuverability) but allowing enough rail to penetrate and maintain control seems to be the result. That's just my take. Here's a pic of the Eaton Vee - it measures out at about 1/2" right at the tailblock.
Hey John - what's the fin set up on that Eaton? One thing you can say about him, he's not afraid to push the envelope. Does some wild Zingers w/ huge double concaves in them (glasser's nightmares...) I've ridden some Eatons that I liked, and others that I couldn't get comfortable on... I think that on a wide (and or big/heavy) board, a bit of tail v is going to allow easier initiation of turns -- whereas shallow V further up on the board has the opposite effect, more of a control feature (thus good on guns)...make the board track a bit. Same feature can have the opposite (instability vs. stability) effect depending on placement..
The lift from planing is strongly dependent on bottom contour. Even with cars, we know this - flat bald tires will hydroplane, whereas rounded tires require much much higher speeds. Bicycles never hydroplane because their tires are rounded. A half inch of Vee will decrease lift in that portion of the board by a lot, and distribute weight more in the middle, and less concentrated on the rails. My impression is that overall lift dominates resistance to motion on a surfboard - another way to think about it is minimizing the water you displace as you flow through it. Longboards increase wetted area but usually decrease resistance - they have more lift. I doubt there is much speed increase at all in moving away from a flat bottom (not that I dispute benefits to various Vee or concave shapes - just that lift and speed are not among them). http://www.blakestah.com/fins/
Hey Speedbeads could well have been invented by Morey. The first samples I saw in '68 were on the bottoms of Dick Keating's boards. Front wheel of my road bike planes right up around 45mph, with weight back. Front wheel of my RM125 planed at 3rd gear middle of powerband, weight back. Mainly, we need to clarify what we mean by "SPEED". It could be to make a slog board go faster in knee high waves. It could be to make a gun board go faster at Mavs TOH. More important, it could be to make a gun board DROP IN EARLIER at Mavs TOH. Kinda hard to measure. Assuming both surfers take off at exactly the same spot and kick out exactly the same spot, who is going faster....the guy who trims across the middle of the wave, or the guy who bottom turns into off the lip combos, with a roundhouse thrown in for good measure? I say the second guy, but most surfers say the guy who covers the least distance for the time goes faster. The first guy. See, gotta quantify.
the first tow boards were designed with concave taken from the skurfer with the guy working with brewer at the time.cancave works at high speed!
blakesta, the reason rounded tires hydroplane less is because they have a higher psi on the smaller contact patch. Not because they are round. wide flat tires will hydroplane more because they have a lower psi.
Keith - In photo, 3 3/4" O'fishl sidebites trailing edge 14 1/2" up with a 4 3/4" trailer in a standard long box 6" up. Also has worked well at head high+ Stables in Ventura with a single 7 1/2" cutaway and in double overhead+ with same cutaway + sidebites at Morro Rock. The board has seen better days but IMO, a great utility board and still a decent rider. Other dimensions: 16 3/4" nose, 13 1/2" tail, 23" wide.
makes sense, some tail v on a 23" wide board, w/ a fairly narrow tail...
Erik, Your 25+ years of surfing experience should tell you more than anyone else can about what works best for you. Its oversimplifying things to think there's one right answer for bottom contours, rockers, etc.(I make this mistake all the time). I vote for the flat bottom because its your first board and keeping things simple may work best. I think that as the volume of a board decreases relative to the riders size you can add concave to give it "lift" or conversely as the volume of a board increases relative to the riders size you can go into vee(s) to help control the extra volume. The waves you'll be riding will dictate whether you need concaves for "lift" or vee(s) for control as well. If you go with "flat rocker" than you may not need concave (or much concave) which is in effect lowering the stringer rocker even more. Some people put salt on every meal and some people put pepper. Find out what tastes best for you. Good luck and have fun.
wow, lots of good things going here. I was reading about the tire hydroplaning on the water. The key aspect to see here is aspect ratio. Aspect ratio is the span of a wing divided by its chord length. So a wing 20 feet across that is 5 feet from leading to trailing edge (direction of flow) has an aspect ratio of 4 to 1 (20 feet across the flow / 5 feet with the flow). A couple of Aspect Ratio facts: higher aspect ratio lifting bodies (a sailplane wing) are very efficient, it produces very little drag for the lift created. The slender wing provides little time or distance for the passing air to go turbulent (turbulence equals drag). The drawback is that higher aspect ratio lifting bodies are usually unstable; sailplane wings are very susceptable to stall. Back to the tire: it might be hard to explain this w/o pics but imagine the footprint of the tire on the water as having an aspect ratio. I am envisioning a footprint kind of oval shaped. A long slender 10-speed tire has a chord length in the direction of motion that is greater than the width of the footprint (from left to right). This is not efficient so it does not lift well but it is stable. If we go with a wider tire, or even flip the ratio to something like a steam roller wheel (pretend it weighs the same as the bike) we get a high aspect footprint. If the footprint is the SAME AREA as the tenspeed footprint, it will lift with more efficiency BUT it is inherently unstable. Flow could break down while in motion and the hydroplaning would momentarily cease and start back up again. Kind of a dipping motion. (The bike tire could also be inflated or deflated to change the aspect ratio; keep in mind that the footprint AREA would change as well). NOW, let's look at a surfboard. Focus just on the wetted area. (Just cruising along at Waikiki to make this easier). The wetted area of a planing surfboard has an aspect ratio. As expected the long slender aspect ratio of a standard longboard is a LOW Aspect footprint (Stable, but susceptable to turbulent flow along its' length). Theoretically, the most efficient footprint would be a HIGH Aspect ratio. (Remember this is WIDER than it is LONG with respect to flow direction). I see something like a super wide fish, say 28" wide that is incredibly short (in wetted area; the board could be long so you could paddle). At speed, the wet footprint might be only 1 foot long(nose-to-tail) and over 2 feet across (rail-to-rail). Like the sailplane wing this would be very efficient (lots of lift given the area) but very unstable (you're bound to eat it quickly). With this understanding some key elements appear. First, there is an optimum low drag aspect ratio for a given surfer/situation. Second, there is an aspect ratio that is controllable. Bottom contours mess with the effectiveness of the aspect ratio. "Hot" areas can be created that produce higher lift and "cold" areas that produce drag. The best solution for the next board you make is up to you, the shaper/designer. The bead described is another way to maintain Laminar flow. Mr. Morey was fully aware that devices such as "trips" and "vortex de/generators" can bring smooth flow along the length of a board. I calculated the flow along the bottom of a board has the POTENTIAL to start going turbulent (bad) in as little as 5 inches of flow distance. (Visualize a dam overspilling and the water is smoothly pouring down the concrete surface nice and clear and at some time the water starts to turn into "boiling" water, still falling, and eventually ending up as a froth just before striking the bottom of the spillway; the boiling is turbulent and is dragging, skidding slower over distance) To reduce the bad turbulent flow a crosswise piece of narrow tape can be placed every few inches (I tried built up resin pinlines) along the part of the board that is most often wetted. This works. Instead of crosswise "trips", patterns such as reverse Chevrons promote Laminar flow. This is fun to try on existing boards. I eventually found that certain bottom contours will promote laminar flow others reduce it. Watch water flowing over a smooth stone in a brook or down a sluice; interesting. Lastly, Vee off the tail will allow a rider to do a "wheelie" or kickstall; that's easy to see. As the name implies the wheelie eventually results in a stall. Well, take this situation and roll it over on its' side. Board up on rail, sideways wheelie, takes more time to get to the stall. A skillful rider disguises the stall with a swing of the nose and shifting weight back up on the board... Remember all that was mentioned is ignoring a lot of other elements such as rail shape, rocker, foil, fin lift/downforce, and flex which as you know play a large part in finding good answers for you...