Nick, that's the kind of clear explanation I wanted to see. Thanks Matt Broze -----Original Message----- From: Nick Schade <schade_at_guillemot-kayaks.com> To: paddlewise_at_lists.intelenet.net <paddlewise_at_lists.intelenet.net> Date: Friday, May 28, 1999 7:48 AM Subject: Re: [Paddlewise] Pro's and Con's of the "Swede Form" >At 9:31 PM -0700 5/27/99, Matt Broze wrote: ><snip> >>>(SNIP) >>John said: >>>Boats do not climb their bow waves nor do they cut through them. Boats >>>create their bow wave. Regardless of where it lies on the boat the first >>>wave created (called a pressure disturbance) is the bow wave. I know I >>>sound like a broken record on this but ................ >> >> >>Of course the boat creates the wave but that wave sure looks to me like a >>hill to climb that is bigger than the hill that would have to be climbed to >>reach planing speed if one started from a position where the wave hadn't >>already been formed. I am well aware that true planing is beyond human power >>except with the use of hydrofoils (at least at the present time and into the >>forseeable future). > >I have used words to the effect of "climbing its own wave" to describe what >is happening at hull speed myself because, although I knew better, I did >not understand it well enough to come up with a better explaination. As >much for my own benefit as anyone elses, I am going to try again. > >We tend to think of the waves as creating, or being the source of drag, >when they are really the visible evidence that drag has already occurred. >When a hull moving through the water experiences drag, it is due to the >water applying a force to the boat. This force is sapping energy from the >boat. For energy to be conserved, the water must increase in energy. In >other words the water is put into motion by the drag of the boat on the >water at the same time the boat is being slowed down by the drag of the >water on the boat. > >The energy put into the water by the boat must go somewhere. Some of it is >lost in frictional heat in turbulence where the water molecules rub against >each other and heat the water slightly. The rest of it produces waves. If >there was some other way to disipate the energy the waves would not appear, >for example if fish were imparted kinetic energy and got squirted out of >the water, or if little propellors hooked to generators absorbed it all. >Even if the waves never appear, the drag still would have occurred. Once >you see the waves it is too late, the damage is done. > >When John says "Boats create their bow wave.", it sounds a little obvious. >We didn't think evil demons were doing making them. But, what it means is >that the boat can not avoid the wave. If there is a lot of drag the wave >will be big. If the boat can power its way through the drag and get into >another drag regime, the wave will change. If the drag diminishes, the wave >will diminish. You can't climb over the wave because the wave is basically >innocent. The wave is a side effect, not a cause, of drag. > >This is not completely true because the changing wave shape can change the >flow of water around the boat and this can change the drag, but it is not >really the wave itself creating the drag. Drag is from friction and >viscosity. > > >Nick > > > > >Nick Schade >Guillemot Kayaks >10 Ash Swamp Rd >Glastonbury, CT 06033 >(860) 659-8847 > >Schade_at_guillemot-kayaks.com >http://www.guillemot-kayaks.com/ > >>>>>"It's not just Art, It's a Craft!"<<<< > > >*************************************************************************** >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/ ***************************************************************************
This archive was generated by hypermail 2.4.0 : Thu Aug 21 2025 - 16:32:59 PDT