Having read your post about your adventures with your Prijon Barracuda I offer this link, googled OTW to something else:
http://www.kayakforum.com/cgi-bin/Design/index.cgi/noframes/read/2198
there is a notable designer from Guillemot Kayaks responding and another post which gave me a lot of insight into the effect of waves on chine.
Other kayakers who have kayaked both hard and soft chine boats are invited to discuss/compare any perceived differences. Not to start a “which is better” argument, only to understand how others experience the differences, particularly in active water.
The designer’s reply is correct as far
as it goes (waterline width, and height of center of gravity), but it is strange that he does not discuss what the hull does ABOVE the chine. Whitewater boats can be very flat-bottomed, but that does not affect resting stability. What does affect it is how the sides of the boat are flared above the chines. If the sides flare outward, the boat is likely to have good initial stability. If they flare inward (tumblehome), the boat may have little initial stability. A hard-chined boat with straight up-and-down sides is likely to have limited resting stability, and may feel “twitchy” when side currents work those flat sides.
It is mainly what happens when the boat starts to tip that determines initial stability. This is true whether a boat has marked chines like my Necky, or only vague chines like my Phoenix c-1.
Thanks, but I don’t have a Barracuda.
I have paddled cooldoctor1’s Barracuda a couple times, though.
I’ve also never discussed hard and soft chines, but I may take a look at the link that you provided.
Thanks for thinking of me 
From my experience
I don’t see much difference from how a hard chine hull handles rough conditions compared to a round hull. I see many other hull features that effect a kayaks performance. A kayaks volume, rocker and shearline can make a bigger difference in how a kayak handles rough conditions. The only thing that a hard chine seems to really do is turn a kayak when leaned and some hard chined kayaks do this more than others.
you knew I would “chine” in
– Last Updated: Nov-28-07 10:27 AM EST –
Sorry about that.
In my limited experience, owning both a hard chine and rounded hull boat, I find some differences. Biggest one is the one Don mentioned, carving turns. Also, it might be subjective but I find my greenlander more "grippy" and "twitchy" in rough water; the pintail just wants to slide around. Obviously they have dramatically different rocker also. I wonder how a q-boat might compare to the pintail.
So have you been out on the water lately?
Stability
– Last Updated: Nov-28-07 11:26 AM EST –
I own a Chesapeake 24" wide hard chine kayak from years back and my 21" Outer Island is more stable in primary and secondary. I also have two 20" and a 19" hard chine kayak. The 20's are decent primary for a seasoned paddler and the 19 is a rolling kayak (wether you want to or not).
My personal (unofficial) take is this: I find hard chine boats are very sensitive to the amount of "V" shape of the hull. If the hull bottom is relatively flat, they seem similar to a soft chine boat of equal dimensions (like Betsy Bay's). But the slightest V shape and they seem to loose inititial stability dramatically. They tend to teter you back and forth whereas the soft chine boat is cradled on it's sides by the water more. Plus I find the secondary on soft chine more gradual and reassuring. The 2ndary on the hard chine seems to kick in quite a ways over no matter how flared the sides are.
As far as carving turns. My 24" carves great which is normal for a wide HC boat. The narrower ones carve about the same as a soft chine.
I don't know if you were only interested in short play boats, but that's my experience with long ones.
Flare and Stability
The shape of the boat above the water does effect stability, however, it has very little impact on initial stability.
This of course depends slightly on how you define “initial stability” but to me it makes sense to have “initial” refer to how much effort it takes to tip the boat just a little bit. Say one or two degrees.
When the boat tips just a little bit, all that really matters is the shape of the water plane (i.e. the waterline perimeter) and the location of the center of gravity. At small angles of tip, the water plane does not change much regardless of the shape above or below the waterline.
The problem with this kind of discussion is someone will always give an example of a two boats, one with a chine, one without, or one with flare, another with tumblehome. They will then compare the two boats directly. Saying one has more or less initial stability.
Unfortunately, the boat that has a chine may have flare, or in may have rocker, where the one without may have a high seat and very pinched ends. So, instead of comparing one design characteristic of one boat with one different design characteristic of another boat they are actually comparing two completely different boats and attributing all the differences to only one design characteristic.
Any two boats with exactly the same waterplane shape and exactly the same center of gravity the initial stability will be the same regardless of chine style or the degree of flare or tumblehome. They may diverge quickly in their stability characteristics, but if you just tip them a little bit they will be nearly identical.
For more discussion about this you can read:
http://www.guillemot-kayaks.com/guillemot/KayakStability
somehow your name & cooldoctor’s
got entwined w. the Barracuda. My mistake. Hopefully the discussion is worth it anyway.
Being primarily a whitewater kayaker,
I relate “initial stability” to what happens if the boat is tipped maybe 10-15 degrees, while “secondary stability” is what I hope comes into play when a cross current tries to throw me on my ear. Your definition is as good as mine, probably much better for your purposes.
Because whitewater boats are into a flat-bottomed “planing hull” fashion phase, lots of paddlers assume that a flat bottom means firm initial stability. I happen to own an old WW kayak that is very flattish across most of its under-surface, but has very little initial stability, because the sides can inward. I have a very elliptical c-1 that firms up quickly when tipped 15 degrees, because with little rocker, its sides bite like invisible sponsons as they are pushed into the water. Stability certainly depends on a number of design factors. If one wants to design a boat that is flat-botomed in cross section and have it feel stable, one had best attend to the shape of the sides, among other things.
long boats the focus
of my interest (altho hearing from the WW people was good too, thanks, I just got a old school Pirouette SuperSport and no time to play w. it yet).
Jay, I get exactly what you mean by the water cradling a soft chined long kayak and having to “feel” more on a soft chine for the infinitely gradiated over-the-edge position. Have managed to oops myself over the edge of the Fuego practicing high braces and stationary sculling, but that happened only twice in hours of freshwater practice. I give more credit to the boat than me for that.
I’ve been thinking about this since I sat in a P&H Bahia in late September. A beautiful boat that suits a good paddling partner very well. He proudly offered me a trial and it was the first time I felt the tippyness of a narrow kayak in a negative way. Normally I love slender beams. (Bahia runs 21 on beam and is def hard chine with a very steep and narrow V running a good length of the hull).
It just felt to me like it was going to lay on one side or the other when it wanted to - and this was calm water. It wasn’t a solid balance like a foot on a balance beam, more like a foot balancing on a football 
Just off this initial impression (and I’m not saying the kayak should be judged on it) it wasn’t too confidence-inspiring to think about handling the Bahia in quartering seas or other textured water. So this has led me to more thinking about all the factors that contribute to stability, esp. secondary.
Thanks all for the good comments.
Initial Stability
If you look at comparison of different hull shapes in the article mentioned above: http://www.guillemot-kayaks.com/Design/ConstWL.gif
you will see that it is at angles of heel above 10 degrees that the varied hull shapes start to diverge, but even at 20 degrees they are still within the same ball park. Only above that do they really vary in ways that would be perceptible to a casual test.
You could extend the range of “initial stability” out to higher angles, but I think you start to stretch the definition of “initial”
With very low volume boats where even a slight lean can cause the deck to submerge, stability can drop off very quickly while still in the “initial” zone, but I stand by my contention that cross-sectional shape of a boat has very little impact on initial stability. Most of the perceived differences can be accounted for by other design factors.
You may have a boat with a certain design feature that has a certain stability factor, but that does not mean that the feature accounts for the factor.
Agree with JB and FF…
The Prijon Barracuda is chined, in a sense, certainly not rounded hull, and it is v-ed. It is extremely unstable initial stability, esp as FF states, in quatering seas. I have had it with Puddlejumper on Lake Bloomington in 30 -50 mph winds and I thought I’d be a swimmer for certain, and I am fairly adept now at paddling. So, I concur totally with Jay B’s explanation and Friendly’s experience.
I will state that this factor should be a major consideration when buying a boat, as two vessels each with a 21 inch beam (like my Nordkapp RM versus the Cuda) can have a truly different “feel” for stability.