PeterO wrote, > A couple of us were wondering if fixing the rudder in this "dead ahead" > manner would increase the hull's limiting speed, or whether it's >really > the cockpit to bow length that tends to govern a kayak's hull speed? In > other words would removing the rudder slow the boat down >on a calm water > surface with negligible wind or current. This type of rudder only affects the wavemaking resistance if it effectively increases the waterline length. In most cases they lack sufficient volume to have much effect. (I am not familiar with this boat so cannot say what happens to it specifically). There is a technique for determining effective waterline length but I wince every time I use it particularly in the stern where the buttock slope may be more important. One other note, the waterline length is not a speed limiting factor although it does affect wavemaking resistance. Confusing? The so called "hull speed" is not a limit. It is just a point where the wave created by the boat equals the effective waterline length. At this speed wavemaking resistance may be at its maximum but one can usually go much faster. Cheers John Winters *************************************************************************** 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/ ***************************************************************************
Thanks John and Matt for the explanations. Until now I had only heard the term hull speed used to describe the dimishing returns for paddling effort as boat speed increases. I certainly appreciate your description of contributing factors. The end of the hull adjacent to the rudder doesn't taper to a sharp edge but is several millimetres thick and a sliver of deck also overhangs the rudder so removing the rudder might produce the separation drag that Matt mentioned. Perhaps the optimal strategy for combining manoeuverability with speed is to allow the rudder to move freely with no control from the feet, rather than simply remove it. Fixing it in the "dead ahead" position sounds as if it would produce the best speed at the expense of manoeverability on flat water. In practice I've crossed the cables and press the rudder hard over with the leg thats not pushing the deck at the same time as edging. Of course most of the time this is pretty academic but in the event of a cable failure in a race it could be worth thinking about. (Our 110km Hawkesbury Classic is coming up in a week or two!) John, your technique for determining effective waterline length was intriguing - I googled Professor Inverbon's dissertations but couldn't find anything that sheds any further light:~) All the best, PeterO *************************************************************************** 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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