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Kayak and Canoe Design Bulletin Board
Re: racing kayaks
Posted By: Nick Schade In Response To: racing kayaks (Berkeley C.)
Date: Friday, 9 July 1999, at 1:22 p.m.
Hull speed is not a hard-and-fast speed limit. It typically marks the transition from displacement to planing, but even this line is fuzzy. Hull speed is the speed through the water where the wavelength of waves going that speed is equal to the waterline length of the boat. This usually corresponds to a distinct increase in the drag of on the boat.
Prior to reaching hullspeed, most of the drag comes from friction of the water moving along the hull. A larger wetted surface area will typically have more drag at lower speeds. In other words, a theoretically faster boat can be slower at low speeds for a given exertion than a "slower" boat. You need to overcome the low speed drag before the improved high speed drag makes any difference.
It is also possible that your Tracer only seems faster than your Valhala. Have you done time trials?
> I'm building a CLC Patuxent 19.5 for open water racing primarily, but I
> also paddle a Valhala racing surf-ski, a Pygmy Osprey, and occasionally a
> Tracer flat-water racing kayak. I'm trying to figure out the various
> dynamics that go into speed. One thing that I'm unclear on is the concept
> of hull speed. As I understand it, hull speed is directly relative to
> waterline length. The Tracer is the shortest of the boats I paddle,
> accelerates the fastest and has similar top speed characteristics to the
> much longer Valhala. Why is that? Or am I not yet a strong enough paddler
> to realize the speed potential of the Valhala?
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