What are the advantages/disadvantages of more/less nose rocker…what are the advantages/disadvantages of more/less tail rocker? It would be a huge help if someone could explain this to me. Thank you
I had to throw this together. There are sure to be errors and ommissions. When a solid surface planes on the water, less front-to-back curve means less resistance to speed. Surfboard rocker serves three purposes: 1)Provide optimal planing speed on a curved wave surface 2)Provide a curved surface to turn on 3)Provide drag and lift for controlling wild vertical conditions Surfboards have to fit into curved wave surfaces. Surfboards also have to plane at a wide range of speeds. With surfboards, only about the rear 60% contacts the water at average trim speed, so tail rocker is the important rocker. Hull resistance gets especially bad when rocker causes a sharper angle to the water surface at “entry” where water first touch board. A board turn pivots about the entry area. You need to stand, and your fin(s) should be, a reasonable distance behind the entry pivot in order to control and throttle turns, and to resist surface chop. Faster planing speed moves the entry point back, so you’ll have less board surface in the water. You’ll also have a shorter turning pivot, even though the faster speeds require a longer turning pivot. Tail rocker and tail outline curve work together. If you’re trying to catch large fast breaks: You need a little less rocker to match greater speed with a flatter wave surface. Since speed will move the entry point back, you need a longer narrower tail, and reduced tail rocker. The combination will move the entry point forward again. You have the same rail contact for control, while maintaining a reasonable moment between rider/fins and entry point. If you’re trying to catch small hollow waves: You need more rocker to match slower speed with a more curved wave surface. You need a fuller tail outline to plane at slower speed. You need rocker progression (flat entry with increasing stern rocker). Rocker progression reduces entry speed resistance, and increases lift and control in gutless waves. Measure nose and tail rocker by placing your board or blank on a flat surface, balanced on the center point. Measure nose and tail rockers from the surface to the tips. Adjust tail rocker up or down from 2.9% of board length. Nose rocker? Shape in enough nose rocker to keep from pearling while you learn, or when you drop in out-of-control. If you’re shaping a noserider, make the nose rocker pretty flat. You’ll be standing up there. There are lots of theories about nose rocker, but they all come down to personal preference. Adjust nose rocker up or down from about 25 degrees off the horizontal.
Nice design summary. Thank you for posting it. Patrick Shannon
Yes, nice job on the explination! Thank you very much! I guess it would be better to go with less nose rocker and get more waves…and adapt my drop in to not pearl the nose. Thank you!!!
Noodle, great explanation. Could you elaborate on these paragraphs, specifically what ya mean by entry area?>>> A board turn pivots about the entry area. You need to stand, and your > fin(s) should be, a reasonable distance behind the entry pivot in order to > control and throttle turns, and to resist surface chop. Faster planing > speed moves the entry point back, so you’ll have less board surface in the > water. You’ll also have a shorter turning pivot, even though the faster > speeds require a longer turning pivot.>>> You need a little less rocker to match greater speed with a flatter wave > surface. Since speed will move the entry point back, you need a longer > narrower tail, and reduced tail rocker. The combination will move the > entry point forward again. You have the same rail contact for control, > while maintaining a reasonable moment between rider/fins and entry point. thanks, m
Noodle, great explanation.>>> Could you elaborate on these paragraphs, specifically what ya mean by > entry area?>>> thanks, m Shapers refer to “entry” as the area across the bottom of a surfboard where surface water first contacts the board when the board is planing. Water doesn’t compress. When a hull planes, it only rides on the water after pushing forward a volume of surface water in the entry area. So the entry area is where drag concentrates. Surfboards are designed to plane at a wide range of speed. Slower planing speed allows water to strike the hull farther forward. As the surfboard planes faster it rises higher out of the water, and less of the hull contacts the water. The entry area moves back toward the stern. Powerful surf adds board speed. Board speed causes the board to ride higher on the water. Higher on the water means the entry line, the area of greatest hull resistance, moves back toward the tail. The idea in powerful surf is to move the entry line forward again. Think of driving a tow motor (fork lift) where you steer with the rear wheels. Now think about steering a tow motor which had a wheelbase which shortened, and tires which shrunk as you sped up. You’d wreck that sucker the first time you accelerated. At 25 mph a 180 lb rider on a 9-6 longboard will have X square ft of his board hull contacting the water. If the board is wide the entry line could be 5 ft up the board. Narrow the board, and X square ft of surface contact would require that water enter the board farther forward. Then flatten the rocker. You will increase the surface contact area and move the entry line farther forward.
I agree with everything Noodle explained. A thin down rail up front combined with a narrow nose also contributes to a more forward entry line as the water flows over the rail a bit more. As usual, it’s impossible to isolate a single component. It’s all gotta flow.
Noodle and John, I acknowledge and appreciate your patience with my request and the prompt response. m