Boat Building Forum

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Re: Hard Chine Shape
By:Shawn Baker
Date: 6/29/2001, 1:28 pm
In Response To: Re: Keel Rocker? (Craig Bumgarner)

: Can you offer quantities to the variables that contribute to edge steering in
: a hard chine sea kayak? Beam/Length ratio? Deadrise? Rocker?

The shape of the hard chine of the boat makes a huge difference. "Rocker" in the chines makes the boat turn faster. At first, I thought that more rocker in the chines (more swoop up at bow and stern...even more than the keel) made the boat carve better, but that's counter-intuitive. When you edge the boat to the right to carve left, that shape should make the boat want to carve right....

So...I think it's the fineness that it causes in the ends. Where the chines stay in a plane with the keel, it generally gives the boat fuller ends. When you edge the boat, less of the ends come out of the water. With finer ends, an edge picks more of the keel and ends out of the water, and a sweep or two gives you more turning effect.

I actually think a higher beam/length ratio would make the boat carve better, but then it's harder to get the boat up on edge with a beamier boat.

Rocker makes a definite difference, as do the shape of the ends. Boats with plumb sterns don't maneuver nearly as well as those with more overhang...even if the overall shape of the rest of the boat is nearly the same. It's a small area, but it's way out on the end of the boat, and an extra little triangle of keel hanging down makes the boat track like feathers on an arrow.

I would think that less deadrise would let the boat carve better, but I think that factor is secondary to the shape of the chines, keel rocker, beam, etc.

Most of my opinions are from experience, but I'm not a boat designer, and haven't had the benefit of being able to paddle highly similar designs side-by-side to be able to compare single variables. I would guess that some of the skinboat builders (Harvey Golden comes to mind) would be able to come up with much clearer rationale.

But this stuff sure is fun to experiement with and talk about. No offense to beginners, but don't pay a lick of attention to any of this discussion. Don't let these opinions sway you in the choice of your first boat--we're talking about very subtle nuances here that don't make a huge difference until you've got a few miles under your butt...er..boat.

Shawn

Messages In This Thread

Keel Rocker?
Craig Bumgarner -- 6/29/2001, 11:29 am
Re: meet you in "design" *NM*
LeeG -- 6/29/2001, 11:40 am
Re: Keel Rocker?
Shawn Baker -- 6/29/2001, 11:35 am
Re: Keel Rocker?
Craig Bumgarner -- 6/29/2001, 12:43 pm
Re: Hard Chine Shape
Shawn Baker -- 6/29/2001, 1:28 pm