Dave Kruger wrote >This means that somebody on a surf ski working his/her butt off paddling to >maintain a surfing position on a wave in the middle of a wave train will >eventually be riding on the leading wave of the train ... which will soon >diminish, leaving the paddler to seek out another large crest to ride. >I think I have noticed this effect trying to maintain a surfing position on >small stuff, too, but can't be sure of it. Anybody else experienced that? I've noticed this on my local (actually in my back yard) river. In the spring the wind blowing against the strong current creates tight-coupled waves of 1-2'. By accelerating on the face of steep ones, I can surf upstream for 20 yds or so, but then the wave just goes poof. I though for a while they were passing me or I was passing them, but they really just disappear. You can see that by watching from shore. Because the waves seem to be bow-shaped and staggered rather than straight washboard lines across the river, I can some times move laterally from the steep leading edge of one bow across a lower shoulder to the leading edge of the next wave upstream, and thus prolong the ride. At least that what it feels like. Waves look more like ^ ^ ^ ^ ^ ^ ^ than like ____________ ____________ ____________ Whether that's a function of their being wind formed, or as John Winters points out, their compound and/or translational nature, I don't know-- unfortunately, in a fit of generousity, I gave my Bascom away. Clark Bowlen *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced/forwarded outside PaddleWise without author's permission Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
John Winters wrote: <SNIP> >>Maintaining equilibrium speed generally requires using a fair amount of energy and one has to paddle pretty hard to surf non breaking waves. If you do not paddle you cannot surf non breaking waves. Breaking waves present a different problem and one has to work to avoid being swept ahead at the translational speed of the breaking wave crest which exceed twice the wave speed (or, if into these things, work to maintain an ideal position on the breaking wave face. You may have noticed how short surfing lasts in deep water waves. Because waves come in different sizes moving at different speeds the large surfable waves resulting from the merging of two or more waves disappear as the faster wave moves past and the wave size diminishes right out from under you.<< <SNIP> Dave Kruger responded: >That's true enough. However, there is a more fundamental reason one can not surf a deep water wave indefinitely: the leading wave of a packet of deep water waves (aka a "wave train") will eventually feed its energy into the wave following it. The net effect of this is that the packet of energy travelling as a group of deep water waves travels at a speed smaller than the speed of an individual wave.< <SNIP> The wave group travels at 1/2 the individual wave's speed. This is most obvious when surfing on a packet of waves radiating from a moving boat. You can start riding one of the last rideable waves and soon you are deposited out in front of the entire wave train with no more waves to ride (at least without waiting for the wave group to pass you by again). Both John and Dave are right about why you might loose that big wave you picked to ride in deep water. It probably was bigger than the rest because it was really two waves superimposed on each other traveling at slightly different speeds and or in slightly different directions. In either case the higher crest is short lived and the waves will soon leave the paddler in an area where the crest and trough are canceling each other, making for a much smaller waves or even (if perfectly matched) canceling out the wave altogether. I disagree with John's statement: "If you do not paddle you can not surf non breaking waves." It depends on the steepness and size of the wave. While I'll admit that surfing without paddling is fairly rare with deep water waves in the wild (at least for any distance). There are times that good if short rides can be found. However there are many places where a deep water wave is steep enough to ride (once you have put in the effort to catch it) without further paddling. A boat wake made by a heavy hull pushing its hull speed can often be ridden for a long way if riding on a crest behind the boat (transverse wave). If you are going the same direction as the boat this wave is being continually created for you and so you don't run into the problem of waves speed vs. wave train speed that you do if riding the diverging crests or the interference pattern of steep waves where the divergent and transverse waves intersect (leaving the most visible V of a wake at an angle of 19 degrees 28 minutes from the centerline, the crests of these steep interference waves move away from the line of the boat that created them at an angle of 54 degrees and 44 minutes). Another situation that creates non breaking waves steep enough to ride is when the waves are moving against the direction of the current. A standing wave at the bottom of a chute on a river or waves (or swell) running into a tidal flow are examples. When the current is running out from Deception Pass, WA at 5 to 8 knots and some ocean swell has moved up the Strait of Juan de Fuca there can be some real nice big steep riding waves that ever so slowly move upstream as I carve back and forth on them by leaning my kayak one way or the other......sheer bliss. Not only are these waves steep enough to surf without paddling but you can even use the paddle as a rudder (or a rudder) to control the kayak and the added drag is still balanced by gravity. I may be missing something here, but I fail to see how the transitional wave (breaking soup) can travel faster than the deep water wave crest that created it. Or even much faster than the speed of the slowed and steepened breaker that created it moments before. Just how and why does it suddenly pick up any extra speed much less "exceed twice the wave speed" as John says. I have a found a formula that calculates the speed of a translational wave (soup) that is based on the waves height and the depth of the water below it. (speed in ft/sec. = sqrt (wave height + water depth) x 32) (multiply the result by .59155 for speed in knots). While this may make it appear that speed is independent of the parent wave's speed and size, it is obvious that the size of the initial wave is going to determine how high a soup can be. The speed (depends on wavelength) and the wave height of the parent wave will determine into how deep of water the wave breaks. I'm not sure yet how the soup's height relates to the height of the deep water wave (or the height of the breaking crest) but from my experiences surfing I'd say that the transitional wave height is far smaller than the breaking crest height (I'd guess about 1/2 as high as the breaking crest--couldn't find this info in "Waves and Beaches"). Since a wave breaks in water about 1.3 times its wave height and a deep water wave won't get any higher than 7 times its wavelength without breaking this will put an upper limit on the heights and water depths to plug into the formula above. Got to run so I'll try to look this up later. Comments anyone? Oh yeah, can we please stick to kayaking and such here and get off the politics and race thing, please. Matt Broze http://www.marinerkayaks.com *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced/forwarded outside PaddleWise without author's permission Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
Matt Broze wrote: > John Winters wrote: > <SNIP> > > Breaking waves present a different problem and one has to work to avoid > > being swept ahead at the translational speed of the breaking wave crest > > which exceeds twice the wave speed (or, if into these things, work to > > maintain an ideal position on the breaking wave face. > > I may be missing something here, but I fail to see how the transitional wave > (breaking soup) can travel faster than the deep water wave crest that > created it. Matt, I think Winters is referring to the *breaking* wave crest, **as** the wave turns into a breaker, and you are referring to the resulting transational wave ("the soup") -- he is talking apples and you are speaking oranges. The top of the breaking crest moves forward (momentarily) faster than the lower part of the wave -- a feature which disintegrates quickly to form soup. In any case, I wonder how well-developed good theories are for soup, it being a rather disturbed, turbulent state (re: formula you quote below). > Or even much faster than the speed of the slowed and steepened > breaker that created it moments before. Just how and why does it suddenly > pick up any extra speed much less "exceed twice the wave speed" as John > says. I have a found a formula that calculates the speed of a translational > wave (soup) that is based on the waves height and the depth of the water > below it. (speed in ft/sec. = sqrt (wave height + water depth) x 32) > (multiply the result by .59155 for speed in knots). While this may make it > appear that speed is independent of the parent wave's speed and size, it is > obvious that the size of the initial wave is going to determine how high a > soup can be. The speed (depends on wavelength) and the wave height of the > parent wave will determine into how deep of water the wave breaks. I'm not > sure yet how the soup's height relates to the height of the deep water wave > (or the height of the breaking crest) but from my experiences surfing I'd > say that the transitional wave height is far smaller than the breaking crest > height (I'd guess about 1/2 as high as the breaking crest--couldn't find > this info in "Waves and Beaches"). Since a wave breaks in water about 1.3 > times its wave height and a deep water wave won't get any higher than > 7 times its wavelength Matt: you mean ** 1/7th ** its wavelength, don't you? > without breaking this will put an upper limit on the > heights and water depths to plug into the formula above. -- Dave Kruger Astoria, OR *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced/forwarded outside PaddleWise without author's permission Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
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