I received two inquiries concerning my post about the N-K SpeedCoach: (1) Please elaborate on speed thru the water vs. speed over the bottom. Answer. The difference between the two speeds is caused by current and leeway. The impeller only sees how fast water is moving past it; it has no idea how fast current might be running and does not measure the transverse speed. That is, you could be paddling at 2 knots with a 3 knot current while the wind is blowing you sideways at one knot. You are really moving at something like 5.1 knots, but the device will only register 2 knots. (2) What are the spring and drag devices like? Answer. They all operate on this principle: If you tie a string to a say a steel nut and drop the nut and string over the side (holding the other end of the string), the pull on the string will increase with boat speed (I think with the square of the speed). The item with which I am most familiar (having one) is the Knotstick. See: http://www.knotstick.com/ $33.95 at Defender Inds. (1-800-628-8225). This item will probably create around 4-5 oz. of drag at kayak speeds, which may be too high. There is no reason why it couldn't be scaled way down to give 1-2 oz. and still work. Ken Cooperstein *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Thanks for the posts about the SpeedCoach, it sounds really neat. Sorry to be dense :-) but what do you mean when you said " it gives speed/distance thru the water and not over the bottom"? -----Original Message----- From: Ken Cooperstein <cprstnc1_at_optonline.net> To: paddlewise paddlewise <PaddleWise_at_lists.intelenet.net> Date: Thursday, December 24, 1998 6:48 AM Subject: [Paddlewise] Odometer for a kayak >I have the N-K SpeedCoach (I also responded in RBP). > >I bought it for my rowing shells, where I have the full set up: >magnetic pickup under seat (for stroke rate), fixed impeller on hull >with transducer inside boat. It is very accurate after calibration. Of >course, it gives speed/distance thru the water and not over the bottom. > >For kayakers and canoers, N-K makes a different magnetic pickup that >derives stroke rate from paddle movement. Also, the stroke rate >circuitry can be completely abandoned and the unit set to figure out >stroke rate from the surges it sees in impeller rotation. > >I have found that the fixed impeller unit is a pain on boats with simple >bottoms without fins -- like Alden Ocean Shells, canoes and kayaks. You >like to pull these up on the beach. This you can no longer do with an >impeller glued to your hull (without taking precautions). So for these, >I use the trailing wire impeller, which works equally well, and has the >additional advantage that it can be used on any [slow] boat including a >sailboat. > >By using velcro and simple clamps, it is easy to move this device from >boat to boat. After all, no matter how many of these little boats you >accumulate, you are only using one at a time. > >Competitors need these devices to monitor their performance. I use mine >to ensure I am rowing/paddling efficiently and getting a good workout. > >If all you want, however, is a distance log, then I think you are better >off with a GPS. > >If all you want is boat speed, then one of those spring-type devices >with a string and plug are the simplest and cheapest. They are used by >sailors and are pretty accurate in the 3-5 mph range. > >Ken Cooperstein > > >*************************************************************************** >PaddleWise Paddling Mailing List >Submissions: paddlewise_at_lists.intelenet.net >Subscriptions: paddlewise-request_at_lists.intelenet.net >Website: http://www.gasp-seakayak.net/paddlewise/ >*************************************************************************** *************************************************************************** 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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