For those interested there is a short discussion of hull speed and length and how it relates to paddlers in the FAQ section of our website. Somebody who wants to get into this in more detail should go to the DOWNLOADS section where they can download a spreadsheet I did based on a method John Winter's came up with to estimate drag. You can change many of the characteristics of a kayak important to drag on this spreadsheet and see how they effect the total drag and the breakdown of drag due to friction and that due mostly to wavemaking (and graphed curves as well). Also many of the sea kayaks that Sea Kayaker Mag has tested have their parameters included in the spreadsheet (all in one place for comparison). I once calculated how fast a strong paddler could paddle a very narrow lightweight 100' long kayak. If I recall correctly it was 1.5 knots. The same paddler could push an 18' kayak about 6 knots. The theoretical hull speed (using 1.34 times the sq. root of the waterline length commonly used--but 1.4 to 1.5 is probably more accurate for a narrow kayak)of a 100' kayak would be 13.4 knots. The FAQ's quickly explains why the facts don't always support the longer is faster "common knowledge". Here is what I wrote for Sea Kayaker back in 1998. They may have edited it some, I don't recall. It has come to my attention that some paddlers are comparing kayaks using the drag calculations all the way out to six knots (6.9 miles per hour). When I originally proposed taking the results out to six knots it was so a comparison could be made between kayaks in an all out short sprint. I still think it valuable to include the drag calculations from 4.5 to 6 knots even though these speeds are rarely achieved in a loaded sea kayak. However, from this issue on we will include a caveat with the drag calculations that states “Note: Three pounds of drag is common for a fit paddler at cruising speed. Only a few can work against five pounds for long distances, see Vol. 15, #2?, p? for more details”. If you think the speeds are a little slower than you travel remember that the calculations are for a 150 pound paddler with 100 pounds of added “gear” weight and we are using knots (not miles per hour--1 knot = 1.1516 mph). If we were to remove 100 pounds of “gear” weight the kayaks speed would increase about 3/10 or 4/10 of a knot for any given drag. What follows is a description of what each pound of drag means to a paddler with 250 pounds plus the kayaks weight (for a total weight usually over 300 pounds). Note: Horsepower is resistance times speed. HP=.003069 x Drag (pounds) x Speed (knots) Pounds of drag. What it means to a paddler Horsepower required at typical speeds 1. Easy paddling for almost anybody .006 HP _at_ 2 knots 2. Most paddlers can overcome this much drag for long distances .019 HP _at_ 3 knots 3. A fit and efficient paddler can overcome this drag for several hours .0325 HP _at_ 3.5 knots 4. A strong expert working hard can withstand this drag for many hours .05 HP _at_ 4 knots (Note: doubling the speed to 4 knots increases the drag about 4 times but requires 8 times the horsepower) 5. A recreational racer can move a narrow sea kayak for several hours .07 HP _at_ 4.5 knots 6. A good recreational racer can move an average sea kayak for an hour .08 HP _at_ 4.5 knots or a good rec. racer in a long narrow kayak at 5 knots for an hour .09 HP _at_ 5 knots 7. Good recreational racer moves a slow kayak 4.6 knots or a fast one 5 .1 HP _at_4.6-.11 _at_ 5 knots 8. Good recreational racer pushing a long narrow kayak for up to a mile .13 HP _at_ 5.2 knots 9. Top recreational racer in a very long and narrow kayak for up to a mile .15 HP _at_ 5.5 knots 10. Top rec. racer in a kayak designed mostly for racing for up to a mile .175 HP _at_ 5.7 knots (Sea Kayaker’s very strong expert (DM) appears to generate about .166 HP for one mile going all out) 11. Olympic kayaker in Olympic kayak (198 lb. total--not 300+) for 3 hrs. .22 HP _at_ 6.5 knots 16. Top Olympic competitor in Olympic kayak for 1000 meters (198 lb.) .40 HP _at_ 8.1 knots 17.6 Top Olympic competitors for 500 meters (198 lb. total wt.--not 300+) .525 HP _at_ 9.7 knots 19. Greg Barton in a 19’ fast sea kayak (~260 lb) for a few hundred meters .46 HP _at_ 7.9 knots 25. Olympic champ in an Olympic kayak for less than 10 seconds flat out .90 HP _at_ 11.7 knots (Note: Olympic kayak drag from tank tests done in 1970’s and reported by Andy Toro in Canoeing: An Olympic Sport, thanks to Greg Barton for finding the Olympic kayak results) Matt Broze http://www.marinerkayaks.com *************************************************************************** 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 Tue May 15 2001 - 10:10:42 PDT
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