John Winters <jdwinters_at_eastlink.ca> wrote: >>>>>Peter wrote; > Tank tests will not allow for the relative movement of the hull > of 3 or 4 knots over the water, Why? > which will very significantly affect the > flow over the blade, unless you have the water in the tank moving several > knots aftward relative to the paddle. How?<<<<<<< First I'd like to thank Peter Chopelas for the very clear explanation of how a paddle blade works in the water several days ago. We have been around this bend before but I think Peter did an excellent job this time in explaining lift and drag and their causes and relative importance in a way I could understand it. I too have questions concerning the suitability of a tank of standing water for adequately representing a paddle stroke in a moving kayak. Possibly if the tank is big enough so that the paddle and the water flow and vortexes coming from the paddle aren't being effected by the sides and bottom (or ends) of the tank a simulation could be done if the paddle is only moved with the same force it is under during a normal paddle stroke rather than the hard strokes during a fast acceleration that a paddler next to a tank is likely to actually simulate. A paddler next to the tank is more likely to simulate the tug-of-war victims than the cruising paddler. Maybe you could mount the paddler (or mechanical paddle machine) on tracks with adjustable drag and have it move as the paddle is worked in the trough. Matt Broze 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/ ***************************************************************************
"Matt Broze" <mkayaks_at_oz.net> wrote: > I too have questions concerning the suitability of a tank of standing water > for adequately representing a paddle stroke in a moving kayak. Possibly if > the tank is big enough so that the paddle and the water flow and vortexes > coming from the paddle aren't being effected by the sides and bottom (or > ends) of the tank a simulation could be done if the paddle is only moved > with the same force it is under during a normal paddle stroke rather than > the hard strokes during a fast acceleration that a paddler next to a tank > is > likely to actually simulate. A paddler next to the tank is more likely to > simulate the tug-of-war victims than the cruising paddler. Maybe you could > mount the paddler (or mechanical paddle machine) on tracks with adjustable > drag and have it move as the paddle is worked in the trough. This will not be quite what you are looking for, Matt, but it is a step in that direction: Dedicated sportfishers have used underwater videocams for many years, very effectively, to detail and document the relative attractiveness of various lures (and their action) to salmonids and other finny creatures. A videocam could be affixed behind a kayak's stern (how's that for one hell of a draggy skeg!), and streamline contrast fluid could be introduced from small nozzles on the ends of wands placed ahead of the paddle to detail at least some of the manifold wondrous phenomena people think occur around paddles. (As a one-time airfoil experimentalist -- built two wind tunnels as a teenager -- I am a full-blown skeptic of anything but empiric study of foils in fluids.) No tank needed, and no concern about edge effects therefrom. Outfit the paddler with monitoring to measure VO2 max, effort, respiration rate, etc, and maybe you'd get somewhere on the question of relative "efficiency" of various paddles. There must be some demented university physiologist or biomechanician who could be convinced this was worthwhile. I've certainly done sillier things as research, and gotten paid to do them ... oh, oh, I'm letting secrets out. Bad chemist. Back to your test tubes, Dave. -- Dave Kruger Astoria, OR *************************************************************************** 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/ ***************************************************************************
On 10 Sep 2004 at 22:20, Dave Kruger wrote: > I've certainly done sillier things as research, and > gotten paid to do them Me too - except I discovered how hard it is to get quantitative information from video cameras underwater (tank tests of icebreaker hulls in frozen towing tanks). Qualitative is easy (ooh - look what happened!), but getting numbers is another story. I also spent a fascinating afternoon with a fellow in a warehouse next door to a towing tank in CA where they (years later) did Titanic filming in between research. I was consulting with the towing tank owner and he introduced me to the definitely-off-the-wall neighbour with his head in the clouds and feet in Hollywood. He did special effects work for anyone as well as technical film work for scientists and engineers. In his free time, he made monster movies (?!?) He showed me all his gadgets, widgets and thingies, many military surplus, to make films that could be _measured_ to get real data in the towing tanks. That was in 1981 and computer technology would make a lot of it easier today, but it's still a big task to use a camera to get real data in the water. Also, big bucks. Hey, I'd do it if someone has the money... :-) Mike *************************************************************************** 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/ ***************************************************************************
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