I’m starting a new thread in the hopes of getting some feedback on the current movement of incorporating snowboard design into surfboard design. Please see the thread, Passive Flex? started by me, particularly my response to Dale’s comments. At the moment the movement seems to be about the template, basically incorporating a convex rail into the design. I think this misses the point. Its about flex, and changing the template will only take you so far, actually not very far considering the materials currently used to make surfboards. I’ve heard the arguments about turning radius, that the convex rail enhances turning etc. but, and I may be alone here, but I don’t see it. I’ve got to admit though, that I’ve never tried a board with a convex template, and there’s a good chance that I’m missing something (regretably, it happens a lot.) Y’s convex rail board is interesting, and it does seem to attempt to structually incorporate flex (see his stringer design.) And it would appear that these boards are becoming more popular, which more often than not a good indication that somebody got something right. Still, given the way people surf, the general need to do what is contrary to what the water and wave want you to do, I have a hard time buying into the design (particularly given the wetted areas of a surfboard, when its actually being surfed.) Perhaps somebody has some insight into to this new application.
I’m starting a new thread in the hopes of getting some feedback on the > current movement of incorporating snowboard design into surfboard design. > Please see the thread, Passive Flex? started by me, particularly my > response to Dale’s comments.>>> At the moment the movement seems to be about the template, basically > incorporating a convex rail into the design. I think this misses the > point. Its about flex, and changing the template will only take you so > far, actually not very far considering the materials currently used to > make surfboards.>>> I’ve heard the arguments about turning radius, that the convex rail > enhances turning etc. but, and I may be alone here, but I don’t see it. > I’ve got to admit though, that I’ve never tried a board with a convex > template, and there’s a good chance that I’m missing something > (regretably, it happens a lot.)>>> Y’s convex rail board is interesting, and it does seem to attempt to > structually incorporate flex (see his stringer design.) And it would > appear that these boards are becoming more popular, which more often than > not a good indication that somebody got something right. Still, given the > way people surf, the general need to do what is contrary to what the water > and wave want you to do, I have a hard time buying into the design > (particularly given the wetted areas of a surfboard, when its actually > being surfed.)>>> Perhaps somebody has some insight into to this new application. The problem with using sidecut to turn is that you have to turn it from the same place every time. Thats fine when you are buckled into a snowboard or a ski that’s about 6 feet or shorter in length. Put it on a 9’+ surfboard and I agree; it is useless. Put sidecut on a 6’ surfboard, you are still going to have to stand in the middle to use it. All of the quickness of a modern thruster will be lost, so what’s the point. If you like long radius turns on mushburgers with no possibility of pivoting off the lip or round cuttys, then maybe this is the way to go. Newbs
The problem with using sidecut to turn is that you have to turn it from > the same place every time. Thats fine when you are buckled into a > snowboard or a ski that’s about 6 feet or shorter in length. Put it on a > 9’+ surfboard and I agree; it is useless. Put sidecut on a 6’ surfboard, > you are still going to have to stand in the middle to use it. All of the > quickness of a modern thruster will be lost, so what’s the point. If you > like long radius turns on mushburgers with no possibility of pivoting off > the lip or round cuttys, then maybe this is the way to go. Your assuming that a snowboard with a single stance can only do long radius carves? Didn’t you forget about the flex? Since your stuck on snowboard you can even move your center of gravity beyond the endpoints of the stick. A snowboard with weight forward turns quick(Throw-you-out-of-balance-quick). Lean back and you get long turns(just have a look at the beginners laying on, the tail, they’re always going straight
). regards, Håvard
At the moment the movement seems to be about the template, basically > incorporating a convex rail into the design. I think this misses the > point. Its about flex, and changing the template will only take you so > far, actually not very far considering the materials currently used to > make surfboards. I’ve been ranting about this a few times, but I’ll repeat it briefly. A convex shape like a snowboard/ski creates pressurepoint to flex from. when you put a snowboard on an edge it bends in the middle due to the shape of the rail. A surfboard at speed or a snowboard with the shape of a regular surfboard would not have any such pressure point and it would not flex much, no matter what pressure you apply. The pressure is just distributed over the surface of the board. Maybe a template with canards in the front and rear of the board would work? Maybe a hydrofoil?>>> I’ve heard the arguments about turning radius, that the convex rail > enhances turning etc. but, and I may be alone here, but I don’t see it. It works on skies and snowboard(possibly it’s the key to turning in powder) and even on waterskies without flex. regards, Håvard
I’ve been ranting about this a few times, but I’ll repeat it briefly. A > convex shape like a snowboard/ski creates pressurepoint to flex from. when > you put a snowboard on an edge it bends in the middle due to the shape of > the rail. A surfboard at speed or a snowboard with the shape of a regular > surfboard would not have any such pressure point and it would not flex > much, no matter what pressure you apply. The pressure is just distributed > over the surface of the board.>>> Maybe a template with canards in the front and rear of the board would > work? Maybe a hydrofoil?>>> regards,>>> Håvard Interesting. And, for the most part, I agree. There’s something else going on here, and I suspect my views on this might be controversal (but I don’t think I’m alone.) I see surfing as planing, and for the most part the lessons learned by marine engineers about planing can be applied to surfboard design. This is actually very important when considering flex. Not to mention, design in general, from noseriders, to template, to overall rocker considerations, in general. The fact is that for a flat planing surface (with a small angle of attack) the pressure distribution under the surface is not uniform (see diagram below, ref. Hydrodynamics of High-Speed Small Craft, by Lawrence J Doctors), it has a well defined maximum, which can be adjusted by both static design, and say, by surfing technique - by changing parameters, like angle of attack. (see diagram) Snowboard dynamics is not about planing (I’ll love to read arguements that take a contrary view.) I’m not sure that there is a specific name given to the dynamics, other than skiing. The diagram below is not a surfboard, and really doesn’t reflect the extremes of attack angle that arise during surfing; they can be quite dramatic. Still the diagram does serve to aid in understanding some of the effects we seem to deal with, in particular those of nose rocker. And even more fun, the classical noserider arguments. If, for the moment, you accept the diagram as an an aid to explore what might be going on under a surfboard, then consider where the refered to stagnation line (the point of maximum pressure) might be when a fellow is noseriding. Or how it might move as he starts walking around on his board (especially if his board has a pronounced rocker), shifting his weight (or does a fellow move as to be just a little behind it at any time? A better position to control what’s going on?) Analyzing longboard design using these arguments is great fun because there is so much board to analyze, but similar arguments apply to shortboards, especially in tail rocker considerations. So, back to flex… A structure with too much flex would actually work against the surfer, as the pressure exterted by the stagnation line would tend to result in an even greater angle of attack (a negative feedback, the board yielding to the pressure), and in addition increasing drag. It would be real balancing act to get it right, especially if it was passive flex, i.e. with no way for the surfer to control it, other than by weight position. Given our current tools, I don’t think such a board is possible. (Prone and kneeboarders are different, the coupling is greater between the surfer and board.) Strap the surfer in, and things do change though. Any further ranting would be in bad taste, the topic needs a new thread. But as I mentioned, in general, I agree. However, I beleive the importance of flex, given the current limits of the technology and the uncoupled nature of stand-up surfing, is limited as a design tool. (By the way, the term Spray Root in the diagram, refers to where the white water (or spray) shoots out from under the board when surfing. This water flow is critical, in both its volume and direction. A surfer noseriding often has a whole lot of it tumbling out from under the nose, which makes sense given where the stagnation line is likely to be. (Changing the direction of water reguires force, i.e. its where the energy to noseride in part at least comes form, Newton’s Third law kind of thing.) At the same time a fellow going straight down the line often has a neat spray eminating from a large part of the bottom in the direction out of the wave, indicating a more distributed stagnation line.
Interesting. And, for the most part, I agree.>>> The fact is that for a flat planing surface (with a small angle of attack) > the pressure distribution under the surface is not uniform (see diagram > below, ref. Hydrodynamics of High-Speed Small Craft, by Lawrence J > Doctors), it has a well defined maximum, which can be adjusted by both > static design, and say, by surfing technique - by changing parameters, > like angle of attack. (see diagram) The problem with boat design vs. surfboard design is that we don’t have any propulsion other then gravity(and possibly pumping). Furthermore we want to go as fast as possible and still be able to turn on a dime. With a rigid board with rigid fins to achive these goals we have to compromise the design. Boats solve it with adjustable fins or propulsion. This is hard to achive on a surfboard. Flex might be one way of solving this problem.>>> Snowboard dynamics is not about planing (I’ll love to read arguements that > take a contrary view.) I’m not sure that there is a specific name given to > the dynamics, other than skiing. Check this out(I’m so lucky to find this picture again): http://www.playboard.no/bilde_arkiv_default.asp?ID=261 It sort of proves that you can carve water with a flexible snowboard with sidecut. And I do believe that snowboarding in powder is very much related to fluid dynaimcs. If it’s sidecut or flex or none of the above that make it possible to turn in powder I don’t know. actually it might be the force found in the angle of attack thinking. I have a few plans for some experiments tho.>>> The diagram below is not a surfboard, and really doesn’t reflect the > extremes of attack angle that arise during surfing; they can be quite > dramatic. Still the diagram does serve to aid in understanding some of the > effects we seem to deal with, in particular those of nose rocker. And even > more fun, the classical noserider arguments. [snip] I think it’s very interesting for noseriding. Also for what’s going on in a turn. If the board is moving sideways, this would propably meen that there is higher pressure on the spray side, no?>>> So, back to flex…>>> A structure with too much flex would actually work against the surfer, as > the pressure exterted by the stagnation line would tend to result in an > even greater angle of attack (a negative feedback, the board yielding to > the pressure), and in addition increasing drag. It would be real balancing > act to get it right, especially if it was passive flex, i.e. with no way > for the surfer to control it, other than by weight position. You can also apply force by pushing with your legs or by doing a turn (which pushes back) if the design allowes it. That’s the beauty of the snowboard design. I totally agree that too much flex would slow a board down, but todays shortboard are already overrockered. The main benefit of flex(coupled with some kind of template working with it and finely tuned) IMHO would be less drag(or less angle of attack if you’d like) without sacrificing turning ability(more rocker when you need it).>>> Given our > current tools, I don’t think such a board is possible. (Prone and > kneeboarders are different, the coupling is greater between the surfer and > board.) Strap the surfer in, and things do change though. Strap in surfing is a totally different game, but it doesn’t really help flex the board(much anyway).>>> Any further ranting would be in bad taste, the topic needs a new thread. > But as I mentioned, in general, I agree. However, I beleive the importance > of flex, given the current limits of the technology and the uncoupled > nature of stand-up surfing, is limited as a design tool. Agree, however with a little bit of thinking outside the box it might revolution standup surfing.>>> (By the way, the term Spray Root in the diagram, refers to where the white > water (or spray) shoots out from under the board when surfing. This water > flow is critical, in both its volume and direction. A surfer noseriding > often has a whole lot of it tumbling out from under the nose, which makes > sense given where the stagnation line is likely to be. (Changing the > direction of water reguires force, i.e. its where the energy to noseride > in part at least comes form, Newton’s Third law kind of thing.) At the > same time a fellow going straight down the line often has a neat spray > eminating from a large part of the bottom in the direction out of the > wave, indicating a more distributed stagnation line. Same as noted through a turn, how can we use this to our advantage? Or are we already? regards, Håvard PS. Where did the p in 1/2pvsquared come from?