Hi all, I have read some interesting thoughts in the paddle sizing discussion, but there are two subjects I really miss. One is the difference between force and power. The other is the difference between force and efficiency. As a touring paddler I am not interested in how much force the paddle can deleiver in the water, I am interested in the optimum efficiency (in terms of power in - power out) of the entire boat- paddler-paddle system. To focus on the paddle: A paddle does slip in the water. If you do a very simple approximation on a normal paddle (not a wing paddle) then some typical values for a Blade size: 0.15 x 0.3 m (6" x 12") are: Force Slip speed (paddle with respect to the water) 5 N 0.3 m/sec 50 N 1 m/sec 500 N 3 m/sec The values are calculated using momentum theory. Compared with the speed of the kayak up to 3.5 m/sec (7 knots) the slip of paddles is significant. In a first approximation slip is proportional to the square root of blade area (again, not for wing paddles). The question is: does this slip influence the efficiency of the paddle? Actually, I do not think that this is necessarily the case. A larger paddle wil have a bigger wake, but probably with a somewhat lower energy density. So effincy will probaly not differ wildly. The slip of the paddle, however, does directly influence the efficiency of the paddler-paddle combination. From the viewpoint of biomechanics, muscles can deliver an maximum amount of power for a given contraction speed. A different (higher) contraction speed has the muscles operate at maximum efficiency. The optimum contraction speed for both settings depend heavily on the person. A very well trained sporter usually operates at hihger contraction speed. This can be seen easily for cyclists, as they have finely adjestable gearing. A touring cyclist uses lower contraction speeds (lower RPM) than a profesional cyclist. And during sprints (=maximum power) professional cyclist tend to use a lower RPM than on long distances (=maximum efficiency). In chosing the right paddle size (that is blade area and length) you can match the gearing you use to the kind of paddling you do. Large blade, long paddle= high gearing. Examples: Slow boat: smaller gearing to keep your muscles at speed Sprint: use larger gearing Another way to adjust your gearing is to change your forfard stroke. A wide sweeping stroke has a higher blade speed than a high angle racing stroke. I think the best way to achieve an efficient stroke is to chose a paddle you like, stick with it and learn to adapt your stroke to the paddle, the boat, the conditions and your own condition. The major difference between paddles is not just blade size or length, it is handling. For example: I like a long narrow blade because it is easy to control blade angle, and ( for the paddles I have tried) they tend to flutter less than wide blades. But this is, of course is a very personal opinion, only valid for myself. Just for what it is worth, greetings, Merijn ****************************** Merijn Wijnen Vinkenhofje 8 5613 CN Eindhoven The Netherlands Tel.: 040-2939991 (job: 040-2650539) Fax: same as tel., call before sending or try twice E-mail: Home: merijn_at_music.demon.nl Job: m.wijnen_at_ind.tno.nl Web-site: http://www.music.demon.nl *************************************************************************** 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 Fri May 11 2001 - 05:24:01 PDT
This archive was generated by hypermail 2.4.0 : Thu Aug 21 2025 - 16:30:42 PDT