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#1
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Board flex and fast powder turns
I gave some thought to why it's easier to turn quickly in powder on a
flexy board.... There are 3 components to turning on a snowboard: steering, edging and pressure. In powder edging doesn't apply, so that leaves steering and pressure. In a wide open bowl you can make long drawn out turns just by steering – pointing the board in the direction you want to go. You don't need to use your knees to apply pressure – you can descend with you knees bent at a fixed angle. But for quick turns you need to use pressure created by active extension of the legs. Two things need to happen to make a quick turn in powder: 1) The board needs to come to the surface 2) The momentum of the board and you needs to change direction Flex helps with both of these. Imagine standing with your board flat on hardpack and jumping. If you don't ollie, you get the board off the ground by developing upward momentum in your upper body and using this to pull up your legs and board. It's hard work! Ollieing uses the flex of the tail as a spring. This helps generate upward momentum in your upper body but also applies an impulse directly to the base of the board to push it off the ground. I think the same sort of thing is happening due to the flex of the board in powder: leg extension is storing energy in the base of the board (due to bending) which then helps to push the board (and you) both upwards and towards the new direction of travel. You can feel the same thing when carving where the spring helps to unweight the board for the edge change. Comments? Mike, Arvin, Phil, Neil, anybody? Iain Looking forward to hitting Kirkwood soon! |
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#2
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id wrote:
I think the same sort of thing is happening due to the flex of the board in powder: leg extension is storing energy in the base of the board (due to bending) which then helps to push the board (and you) both upwards and towards the new direction of travel. You can feel the same thing when carving where the spring helps to unweight the board for the edge change. I don't think it's anything that complex. Powder turns are basically banking off the snow. When you flex the board, it makes a rounded shape against the snow and that helps it come around. Long, curved noses are a big factor, too - when you lay it over, the curve of the nose helps bring it around. I think the nose is probably the most important part of the equation, especially in really light powder where even noodly boards aren't flexing much. Stiff boards can't be flexed unless you can get an edge into something, and they usually have shallower noses, so they tend to go straighter. To get them around requires more muscle, more up and down like you do with old skis. My theory, anyways. Neil |
#3
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Neil Gendzwill wrote:
I don't think it's anything that complex. Powder turns are basically banking off the snow. When you flex the board, it makes a rounded shape against the snow and that helps it come around. Long, curved noses are a big factor, too - when you lay it over, the curve of the nose helps bring it around. That sounds right. Nose flex should increase lift at the nose and help turn the board. But I think for really fast turns, e.g. ducking through the trees, then the spring of board is important - like a jump turn. The mechanism you describe is analogous to the carve where the edge on the snow determines the turn radius and you turn continuously and smoothly. So I agree that the flex will help the smooth continuous turn; but I think it's also critical for the very fast, discontinuous jump turn equivalent. I think the nose is probably the most important part of the equation, especially in really light powder where even noodly boards aren't flexing much. The flex will be determined by the force the rider is applying to the board. When going straight this will be the rider weight. When turning, it's a combination of rider weight and G force. In light snow you'd need to travel faster to get the same G force through the turn and hence the same board flex Stiff boards can't be flexed unless you can get an edge into something, and they usually have shallower noses, so they tend to go straighter. To get them around requires more muscle, more up and down like you do with old skis. So I think you're saying that a stiff board will turn very slowly unless you use the up and down movement; a more flexible board will turn more quickly without the need for up and down movement. I would add that flexible board plus the up/down gives very fast turns. My theory, anyways. Thanks, Iain |
#4
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(it must be that time of year..)
I think you're probably about right. Turning in powder is *not* all about banking off the snow. Banked turns are possible in open glacier terrain, and for those board flex is much less relevant. Even on open glacier most experienced people don't turn that way most of the time. I think I'm probably particularly fussy about board flex as I ride hard boots & bindings. What flex I feel comes from the board. In tight-radius turns on a glacier in knee-deep or better powder there's a great deal of leg action. I don't think it's "up unweighting", but there's a lot of down unweighting and the legs work. Without a lot of experience you'll find most people need to stop a fair bit - the reason is that a lot of work is being done. It takes more effort for tighter radius turns. That work's being done on something, and I reckon it's working against the board flex in the snow. It would be interesting to examing the profile of a trail through the snow, although you could just video a rider from the side.. In the trees.. flex matters more because you're generally doing tight turns. That's all there is to it. What I'm not sure about is how the board flex and camber work with the tail flex, which is obviously related but slightly different. Add in tail shape and you have something interesting to model. Nose shape: I don't think that this is particularly important. I've ridden a range of boards with radically different nose shapes in bottomless and the only thing I'd say you need is a reasonable amount of stiffness plus a decent size. phil |
#5
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I gave some thought to why it's easier to turn quickly in powder on a
flexy board.... Easier but definately not better. On a smooth powder surface with no ruts a slightly shorter firm board is sportier. Compare it to driving a Porsche vs. Cadillac. My prefered ride for powder is a Volkl Anthrax 160 cm. with a 24.7 cm. waiste. og |
#6
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On a smooth powder surface with no ruts [...]
I think we may be having trouble with terms here. The "surface" of the powder is irrelevant 'coz you're in it, not on it. I think we're talking about "bottomless" powder, not just fresh snow at a resort, which is not all that different from pisted snow, assuming you're turning with good style. |
#7
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On Fri, 10 Dec 2004 13:45:30 GMT, id no@id allegedly wrote:
Two things need to happen to make a quick turn in powder: 1) The board needs to come to the surface 2) The momentum of the board and you needs to change direction I won't pretend to know anything about fluid dynamics, but have you considered factoring information in from surfing, or even windsurfing on a short board. The boards are small and sit under the water with the rider's weight. When they get planing they come to the surface. Both types of boards have high noses allowing for deep carves. And a surf board (not sure about a windsurf board) has some flex in it although not that much. As a windsurfer, you may be able to draw information from your experiences. - Dave. -- The only powder to get high on, falls from the sky. http://www.vpas.org/ - Snowboarding the worlds pow pow - Securing your e-mail The Snowboard FAQ lives here - http://rssFAQ.org/ |
#8
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Thanks, Phil!
In tight-radius turns on a glacier in knee-deep or better powder there's a great deal of leg action. I don't think it's "up unweighting", but there's a lot of down unweighting and the legs work. I think the up and down unweighting become the same thing if you're making turns in quick succession. Down unweighting comes from flexing the legs - but you won't have ridden far with straight legs so the extension will have been just before the flexing. So upwards momentum will already have been generated prior to flexing. Without a lot of experience you'll find most people need to stop a fair bit - the reason is that a lot of work is being done. It takes more effort for tighter radius turns. That work's being done on something, and I reckon it's working against the board flex in the snow. It would be interesting to examing the profile of a trail through the snow, although you could just video a rider from the side.. Good point. You could tell a lot from the trail. Sadly I don't think I have the mental strength to study a trail when there's virgin powder close by... Iain |
#9
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Switters wrote:
I won't pretend to know anything about fluid dynamics, but have you considered factoring information in from surfing, or even windsurfing on a short board. The boards are small and sit under the water with the rider's weight. When they get planing they come to the surface. Both types of boards have high noses allowing for deep carves. And a surf board (not sure about a windsurf board) has some flex in it although not that much. I think Phil's point is relevant he with powder you're generally in it not on it. Surfboards and windsurfers have two sources of flotation: displacement (like a boat) and planing. In your surfboard example the flotation due to displacement is not enough to float the rider when stationary - you need additional displacement flotation from the rider himself being under water. Once you're moving you get additional hydrodynamic lift (planing) and actually less displacement flotation as most of the board comes out the water. I don't think the flex contributes much to turning a surfboard As a windsurfer, you may be able to draw information from your experiences. In a normal carve turn there's no unweighting - actually the weight on the water will increase due to loss of lift from your sail. Alternatively you can go for complete unweighting - jump gybe - where you use the sail to get airborne. That makes for a quick turn but you tend to end up stationary - board in the water, not planing. No chance of linking jump gybes! Iain |
#10
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id wrote:
I don't think the flex contributes much to turning a surfboard Do surfboards flex? They look like rigid structures to me, but I don't surf. Neil |
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