Explanations for the carving given here are OK, but they donīt give a full account of why when you lean, the boat turns. If lower resistance to the water would be the answer then the shorter side would move faster and the larger curvature side would move slower because it is longer and deeper. That would mean turning in the opposite direction to the one observed. I have wondered about this subject also, and have come to a conclusion, that may be added to other reasons. In order to visualize the effect better I put my kayak on the floor tilted, and looked at it from front and back. Placing the kayak sideways one can see that in the inner turn side the stern is tilted from vertical but also moves sideways from the center axis and is lifted. The outer side water sees the stern as moving away and more water has to come in to fill the gap as the boat is moving. The inner side stern deflects the water coming on its side. In other words the outer stern is pulled due to the void of water generated as the displacing big mass on that side moves forward. On the inside the water coming straight along the boat is bounced by the "tilted with respect to vertical" stern. This creates a pushing force on the in side and a pulling force on the out side. The small difference, among other things account for the boat turning. In similar fashion, once the boat starts to turn, just a little bit, then incoming water faces the outside bow, pushing it, (as if it wanted to bow to broach), but the inside bow as it moves forward and slightly turning, leaves a void that must be filled with water. Therefore there is a pulling force on the inside bow and a pushing force on the outside bow. These two small forces together make the boat turn. The effect is there in the stern all the time, but in the bow it takes a little bit of turning before the effect occurs. That is why sometimes leaning is not enough to get started turning and a little push is needed. Just a small sweep stroke is enough to get going. The effect is small but effective, and that is why paddling on one side, even tilted counteracts the turning force with ease. It seems to me that the longer the bow and stern the more noticeable the effect is. In white water kayaks it happens also but it has to do more with the hull turning effect that one does with the legs. Of course a small sweep stroke makes a quick turn because there is no mass far away that has to move sideways against the water. The more rocker and shorter it is, the faster it turns with a sweep stroke, but the better defined deep stern and bow will give a better turning by leaning. Best Regards Rafael. At 10:23 a.m. 03/12/01 -0500, you wrote: >At 3:03 PM -0800 12/2/01, Scot Hume wrote: >>I'm trying to understand why rocker makes a boat turn >>easier. My current idea is that if a boat drafts 6 >>inches all the way along, a sweep stroke or other >>force such as a wave has 6 inches to work against at >>the end of the boat. However, if there is rocker, the >>power of the sweep stroke is pushing against only a >>couple of inches and it takes less force to move the >>bow on a pivot point back near the paddler. Is this >>correct? >> >>Also, when a kayak is leaned with the right knee, does >>the boat turn because the water on the right side has >>a longer path and thus the left side is able to move >>quicker through the water so that the boat ends up >>turning to the right? > >Anything sticking into the water is going to resist moving through it. >When you try to turn the boat you need to overcome the resistance of the >water to allow you to turn. Because the ends are farther away from the >center of rotation they create a larger moment arm to create more >resistance. Rocker reduces the area at the ends of the boat, thus >decreasing the resistance. > >Leaning the boat can have many different effects depending on the design >of the boat, but one effect is almost universal regardless of the kayak. >Because kayaks get narrow towards the ends, when you lean the boat you >give it more rocker and more rocker makes it easier to turn (see above). > >Nick >-- >Nick Schade >Guillemot Kayaks >824 Thompson St >Glastonbury, CT 06033 >(860) 659-8847 >*************************************************************************** >PaddleWise Paddling Mailing List - Any opinions or suggestions expressed >here are solely those of the writer(s). You must assume the entire >responsibility for reliance upon them. All postings copyright the author. >Submissions: PaddleWise_at_PaddleWise.net >Subscriptions: PaddleWise-request_at_PaddleWise.net >Website: http://www.paddlewise.net/ >*************************************************************************** *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Mon Dec 03 2001 - 17:46:43 PST
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