Builders' Forum Archives
Re: Weather Cocking Thoug
Posted by LeeG on Jul 30, 2006
One more thing to add into that mix is how those forces change when the kayak is leaned. You could have two kayaks with the same degree of weathercocking paddling forward but one responds to a lean and the other doesn't.
The one that doesn't "unhook" the ends on a lean will be quite unpleasant without a brute force correction like a skeg or rudder.
I made a CLC northbay and it had some of that "front keel" as you describe it. It had moderate weathercocking and strong broaching that a lean really couldn't correct for very well. An adjustable or permanent skeg would reduce weathercocking but it did nothing for the lack of response for turning or broaching as the bow is a much more significant lever down a wave than the stern. It's obvious to anyone using the paddle as a stern rudder when going down a wave or in a ruddered kayak fighting the broach by forcing the rudder. The forces required to balance out the buried bow are enormous. There's no way a few square inches of skeg 5' back will compete with a square foot of bow 8' forward.
On my own version of a "18'x21"" s&g kayak based on the Northbay the angle of the entry was increased (less keel) and the rocker increased assymetrically with some changes in the cross section. At that point I realized how much the pre-glued sheer clamp confined the entry to a narrow range of possibilities as the thick sheerclamp could not bend like the 4mm ply. The computer program didn't configure 3/4" cypress in the final result so the angle of the bottom panels near the ends had a different/flatter rocker than what appeared on the computer. As you said the shape of the ends among other things affect weathercocking/wave handling.
The result was a kayak with the slightly less weathercocking but MUCH more response on a lean and less tendency for the bow to broach. The result was a more maneuverable kayak with an acceptable amount of weathercocking that a lean could compensate for. It was possible to paddle from point A to point B without just putting more effort into one blade.
It's a funny thing, for example the first Necky Elaho was the first skegged Necky kayak, everyone liked it because it would respond well on a lean. Except it weathercocked a bit much. Ok,,so it got a skeg but here's the odd part,,it really didn't stop the weathercocking, it reduced it but primarily just made the kayak stiffer tracking. Paddling with the skeg down and slight weathercocking was more irritating than having more weathercocking and the means to correct it with a lean/sweep. In that boat the hull was still the problem. And now the boat is sold with a rudder.
Some weathercocking is nice, if you're being blown down wind it's nice to have some of that wind pointing you slightly upwind, the important part is to be able to control it, by skeg, rudder or lean.
In Response to: Re: Weather Cocking Thoug by Dave Houser on Jul 29, 2006