I am trying to more deeply grok the data Sea-kayaker provides in its boat reviews. In particular, I am trying to make sense of the KAPER output, and the Righting/Heeling moments. I have a good background in physics, so I understand the science involved. But I have problems relating how a boat feels to this data. What I would like to find is the KAPER data and the Righting/Heeling moment curves for boats i know. In particular, the Plastic Aquatera Sea Lion kevlar Seda Glider feathercraft Khatsalano I can find some of this in back issues of sea kayaker, but not all of it. Do any of you have pointers I might use to find this data on-line? --Tim *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Tim wrote; >I am trying to more deeply grok the data Sea-kayaker >provides in its boat reviews. In particular, I am >trying to make sense of the KAPER output, and the >Righting/Heeling moments. > (SNIP) Stability and resistance data are used in relation to boats one has experienced. For instance, if you have paddled an XYZ kayak and like its stability then any boat having similar stability will probably appeal to you. If you have paddled a boat and know how it feels from a resistance standpoint then any boat with less resistance will probably feel faster and vice versa. The numbers are only important in comparison to other boats. One should not expect light bulbs to pop on when differences are small. Also keep in mind that people are not reliable measuring devices and their moods, physical health, experience, change in paddle, weather, companions and a whole host of additional outside influences will affect ones opinions. Stability and performance data are only two pieces of information and personal perceptions don't always agree with them. Even though the data is quite reliable (KAPER has been shown to be accurate within a range of +/- 5% which is quite good for such things) it still may not agree your personal opinion. Some basics. Stability - The greater the area under the stability curve the better. This is a measure of dynamic stability. The greater the heel before the righting arm diminishes to zero the better. This is called the "range of stability". The greater the heel at which the righting arm peaks the better since this is a good measure of what is called secondary stability. The steeper the stability curve the higher the metacentric height and hence the initial stability. High metacentric heights are associated with a quick motion in waves and increased danger of capsize in beam breaking seas. Resistance The average sedentary North American can produce 0.07 hp for a protracted period of time. A quick calculation (velocity in feet per second times lb. resistance divided by 550) will reveal the hp at any given speed from the resistance information. A weaker than average person will want a boat that has low resistance at lower speeds so they can cruise more efficiently. Stronger than average paddlers will want boats that are more efficient (relatively lower resistance) at higher speeds to take advantage of their strength. My web site has a fair amount of design information on it . There is a page devoted to KAPER (http://home.ican.net/~735769/kaper.htm )and one to general design information (http://home.ican.net/~735769/shape.htm ) These are non-commercial pages so you will not be inundated with a sales pitch. Cheers, John Winters Redwing Designs Specialists in Human Powered Watercraft http://home.ican.net/~735769/ *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
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