Joan wrote: >>Which reminds me of a question I asked this weekend, and nobody really had an answer: if the bow goes through the wave instead of up and over, wouldn't you maintain speed better? (Mine goes up & over, & it seems to me that it slows me down, but I'm not really sure...)<< When we get done arguing blade feather, wide vs. narrow (blades and kayaks), paddlefloat vs. reenter and roll, Swede form vs. fishform and rudder or no rudder we sometimes get down to this. So here is my take on it. The rocking and slamming caused by heave/dip motions can add considerable extra resistance to a hull. Sea Kayaker Magazine tested five sea kayaks in both calm water and directly into 8" high waves that were 16.6 feet long. (Note: 16.6' long waves travel at about 5.5 knots -- the wave speed (in knots) is equal to 1.34 times the square root of the wavelength (in feet)). The kayaks traveled into the waves at 3 knots. There was no wind. The waves increased the average resistance (the actual resistance varies as the waveform passes) by about 1.5 times for the kayak that did the best and up to 2.3 times for the kayak that did the worst. While these may seem like small waves my videos show that most of the kayaks plunged enough to put their bows under at times. (Note: Randel Washburne in his book The Coastal Kayakers Manual (page 26) does a good job discussing the pros and cons of a lifting vs. a knifing bow when paddling into head seas. Unfortunately after pointing out how both extremes slow a kayak, he suggests the wrong conclusion when he says: "Perhaps the worst is a compromise design that does neither well.") I would like to suggest instead that the best is probably a compromise that avoids the problems at either extreme. I once talked to a paddler who had just sold a kayak that both knifed into the waves with its' fine bow and then lifted quickly due to a broad flat midbody. He usually paddled at the front of a group. He complained that whenever his group paddled into head seas everyone, right down to the weakest paddler, would pass him as he struggled with his wet and hobby-horsing kayak. He was extremely frustrated by his kayak that: 1)Buried its bow into waves (adding to its wetted surface friction and pushing a greater volume of water aside). 2)Tilted its' bow up steeply as the wave crest passed (the more the kayak angles upwards--and the flatter and wider the hull is--the blunter the angles at which the wave crest pushes back against the hull and therefore the more the wave will slow the kayak). 3)Slammed down hard on its' wide flat bottom after the wave crest passed (increasing friction with the added water pressure during the sudden--energy dispersing--direction change, and jarring its' occupant into wanting to decrease his speed even further to lessen the severity of the next slam). Yes, perhaps the worst is not the compromise but the kayak that both knifes into and then rises too quickly to the waves, thereby suffering the problems of both extremes as this paddlers kayak apparently did. 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/ ***************************************************************************
Can we add another dimension to this discussion of surf and sea kayaks by asking opinions on the relative performance of hard vs. round chined boats? My Pintail provides an "interesting" ride in surf --- good, but not ideal --- but I haven't yet figured out what my new CLC North Bay is likely to do in larger seas. (Wow, that's where this thread started! Sorta.) Jack Martin *************************************************************************** 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/ ***************************************************************************
At 09:45 PM 7/19/00 -0700, Matt Broze wrote: >Joan wrote: > >>>Which reminds me of a question I asked this weekend, and nobody really >had an answer: if the bow goes through the wave instead of up and over, >wouldn't you maintain speed better? (Mine goes up & over, & it seems to >me that it slows me down, but I'm not really sure...)<< > >When we get done arguing blade feather, wide vs. narrow (blades and kayaks), >paddlefloat vs. reenter and roll, Swede form vs. fishform and rudder or no >rudder we sometimes get down to this. So here is my take on it. > >The rocking and slamming caused by heave/dip motions can add considerable >extra resistance to a hull. Sea Kayaker Magazine tested five sea kayaks in >both calm water and directly into 8" high waves that were 16.6 feet long. >(Note: 16.6' long waves travel at about 5.5 knots -- the wave speed (in >knots) is equal to 1.34 times the square root of the wavelength (in feet)). >The kayaks traveled into the waves at 3 knots. There was no wind. The >waves increased the average resistance (the actual resistance varies as the >waveform passes) by about 1.5 times for the kayak that did the best and up >to 2.3 times for the kayak that did the worst. While these may seem like >small waves my videos show that most of the kayaks plunged enough to put >their bows under at times. Ok. So, what would you do to change the design to reduce the amount of bow plunging? *************************************************************************** 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 wrote: > Yes, perhaps the worst is not the compromise but the kayak that both knifes > into and then rises too quickly to the waves, thereby suffering the problems > of both extremes as this paddlers kayak apparently did. > Let me compare my two boats in lifting vs. knifing. (Solstice GTS and Mariner Express) Both are good compromises but the GTS biases the compromise toward knifing, with some lifting; while the Express biases toward lifting, with some knifing. For going in to waves and weather the GTS is superior. It doesn't dive at all and neither does it pound; nor is it any wetter than the Express. The Express generally lifts but does pound somewhat as it comes down and I end up slightly wetter as it does so. The GTS is smoother and more efficient than the Express in these conditions. (The Express is better in other conditions.) An old model Solstice that I tried, prior the the GTS, had much less flare in front and was awful into the waves (also awful down wave). Superficially, this old model did not look that different from the GTS but the performance difference was striking. Jerry *************************************************************************** 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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