it’s a subjective term
Semantic point but I think you're talking about "stability". "Twitchy" and the sysnonyms I mentioned are all subjective REACTIONS to a boat's stability. I'm thinkinkg twitchiness depends on paddler experience, as well as size and weight distribution.
I'm sure one could quantify stability and the differences in stability between the same kayak loaded or unloaded.
Twitchyness?
First time I paddled my CLC many years ago it was twitchy, for 5 minutes. First time in my Artisan Millenium, it was twitchy, for 2 minutes. My surf ski embodies twitchyness, and becomes twitchy if I tense up. Which I rarely do! My Summersong was never twitchy!
tippy vs. twitchy
When I think of a narrow boat or one with not much initial stability I think of it as tippy. I often find hard chine boats twitchy. For me it's when a kayak doesn't want to sit solidly on the water and wants to teeter from side to side. I usually experience it in hard chine boats because some are designed to carry a certain load and if it doesn't sink deep enough it seems to float too high and never sits solid on the water. I have been in narrow hard chine boats that are tippy and wider ones that are twitchy. I can usually adjust to tippy OK but dislike twitchy boats that teeter from side to side.
Silhouette?
I really liked demoing one but when stationary it sort of felt like that.
That’s what I meant
You can definitely measure the torque required to lean a boat “x” degrees and with “y” load on board (load distributed in some defined way of course). A boat that feels more “twitchy” to a particular person than some other boat WILL require less torque to make it lean by some amount. I was ignoring the fact that an the comfort level regarding this attribute will vary from one person to the next, but not ignoring the fact that any individual’s tolerance to “tippyness” will invariably be judged in the context of some other desirable attribute of the hull. Fair enough?
Feeling twitchy?
Paddle harder.
(A simple but effective solution. The leverage gained from a vigorous and balanced forward stroke can make up for a lack of initial stability.)
Sea Kayaker stability curves
I can pull the last one - it is around here somewhere - but I believe the stability curve labels are more about resistance to heel. Not twitchiness. I have seen reviewers use that term, but I find it fairly meaningless compared to more specific parts of the review where they talk about how the boat behaved in specific maneuvers.
I did not say that what someone perceives as twitchiness is irrelevant, just that it is a matter of individual tolerance and comfort. If moderate twitchiness - whatever that is for someone - can overwhelm or ruin the rest of their paddling experience, it is a boat to be avoided. But there are many who are fine with that, as indicated by some of the replies above. In that case, other factors come to the fore.
I have experienced boats that I would call twitchy myself, and it has not always been about predictable behavior. It at times has been a matter of how the boat responds to waves from odd directions for example, where the same boat shows much smoother behavior to most dimensional water. This is not the kind of thing that I expect to see measured on a stability curve.
For that matter, neither is what jaybabina is calling twitchiness below. A stability curve for a hard chined boat may not capture that tendency of the hull to not sit quietly. The curves may only be reliable on how the resistance develops after the boat has hit its first chine.
Some Yes. Some No.
My cohorts and I are primarily road bike people who sometimes kayak. 95% of our kayaking is day trips laden with little more than lunch. We don’t use road bikes as vehicles for camping trips and seldom use kayaks that way. Boat makers need to keep us in mind.
lively, tender
Thank you. Twitchy strikes me as the term many paddlers use the first time they are in a boat with less primary (and possibly directional) stability than they are used to paddling.
I own 4 sea kayaks. The one (Nordkapp LV) with the lowest primary stability is also the liveliest, most responsive, and the fastest especially in dimensional seas.
The Nordlow, however, requires one is on top of one’s game. So, I often paddle my Romany or Aquanaut instead. I find the current fad of boats which are boxes at midships to feel rather dead in the water. I prefer boats that feel as if they are moving with the water.
Yes easier to edge
I’m a novice here, don’t have all the technical terms down. To me, the Nordlow is easy to edge. The easiest of any kayak I have owned or paddled.
I would see people edging their boats way over, and could never seem to do that comfortably with the Tempest 165 or 175’s I owned. I tried several boats, including an Avocet, Cetus, Aquanaut, and some of the Northshore boats, and they were about the same. Then I demo’d the Nordlow. And bought it.
I guess I thought the Nordlow had more secondary because it was so much easier for me to edge. Effortless. But I guess that’s not really secondary.
Edging my Tempests, I guess it was the secondary that was pushing back. The Nordlow does not do that. it will go where you put it, effortlessly. The flip side is that it will equally effortlessly go back the other way, even when you’re past the point where a boat like the Tempest would not recover.
I have always felt more comfortable in the Nordlow, more so than any other boat, EXCEPT when I let my self think this is SUPPOSED to be a twitchy boat, so there must be something I’m missing here which is going to get me in trouble.