Some kayaks are twitchy, think Nordkapps. Some are not, think Cetus. Other examples of each abound.
Often, but not always, one can get used to twitchiness. But it seems to me there is no inherent advantage to twitchiness. You can get the same quick response, performance, etc., in a less twitchy boat. Does anyone actually prefer more twitchiness to less?
Some kayaks are twitchy, think Nordkapps. Some are not, think Cetus. Other examples of each abound.
Twitchiness or tenderness in a boat is not something anyone really likes. It is something to deal with in exchange for a high level of secondary stability.
Some racing type boats have a very narrow beam which also contributes to twitchiness.
Adding equipment acts as ballast and can help settle some of these boats down a lot.
No one likes twitchy, many seek it
You can't get the same performance and responsiveness in a non-twitchy boat vs. a twitchy one, if both are maximizing their potential. If one is twitchy for the twitchiness sake and stupidly designed otherwise, yes, a less twitchy boat might outperform it in most situations. The idea is that a twitchy boat is optimized for speed and efficiency within certain conditions and skills and a less-twitchy boat will never be as good in these same target conditions (it might be in other, less favorable conditions).
As mentioned, twitchiness is a side effect of low wetted surface. The idea is to minimize resistance in the water by having a rounded hull with minimum wetted surface. If you also build flare, you will get higher secondary stability. If you do not have flare, the boat will be twitchy all the way until you flip.
Cetus and Delphin for instance emphasize solid primary stability and also give added secondary. Nordkapp is much more rounded bottom and thus less primary, so it feels twitchy. It also does not have huge amounts of secondary, so it is more efficient, as long as you can keep it upright comfortably.
If you could have non-twitchy and efficient at the same time, everyone would do it. Can't, so the different designs optimize for different uses (conditions and skills). I might be faster in my twitchy V10 surf ski on flat or moderate swell than I would be in a less twitchy beginner's boat like the V8. but might be faster in the V8 if I paddle in a confused chop and clapotis.
Another aspect is that a good "twitchy" design like the Nordkapp will remain quite agreeable in confused waters, while a boxy and not twitchy design like the Delphin could bounce around a lot more. Up to a point the Nordkapp will be faster and more efficient to paddle and the Delphin will be slower. However, a point comes where the twitchiness of the Nordkapp might be too much for the paddler to handle and they would tire quick in it, slow down, or capsize, where the same person in the Delphin might be just fine and thus be faster and less tired at the end (but those would have to be extreme conditions beyond the comfort zone of the paddler in the Nordkapp, yet within their comfort zone in the Delphin)...
This is basically the same question phrased differently. There is a lot of good discussion on the pros and cons of low primary stability.
But Kocho basically summed up the whole thread.
Cargo - ballast - gear
Boats are for transporting stuff and far too many
demo a boat completely empty - i.e. high twitch factor
That’s good… but this is a case
where just looking at a hull may not predict what it will do. I have an old Phoenix c-1 with a rather elliptical bottom, and you would think it would be twitchy. But it isn’t. It is a bit loose around dead center, but firms up very predictably as it tips.
What’s interesting in the whitewater world is that paddlers keep looking for flat bottoms and sharpish chines, even in creek boats. Such boats should tend to be upset by turbulence or crosscurrents more that elliptical creek boat hulls, but some paddlers prefer them. Examples where makers are offering what some paddlers want are the new Jackson Karma and the revised Pyranha Burn. The latest river runners continue to offer flattish bottoms and sharp chines.
It appears that “new school” hulls with flat bottoms and sharp chines continue to offer something by way of control potential that ww paddlers want to have, even though inevitably, a new school hull will be more susceptible to upset in turbulence than a conservative, roundish hull.
It’s kind of like what drivers have sought in a Porsche, over the decades. The sucker may spin out if pushed too far, but drivers want the control it offers, up to the limit.
Kocho wrote: “You can’t get the same performance and responsiveness in a non-twitchy boat vs. a twitchy one, if both are maximizing their potential. "
Well compare the Cetus LV at 17’5” by 21.25" to the Nordkapp at 17’6" by 21.0"; very close dimensionally. Yet the Cetus is not twitchy at all, in fact confidence inspiring, while the Nordkapp LV is quite twitchy. I don’t see any performance area where the twitchier Nordkapp loses out. Someone might just like the Nordkapp better, but that is another question.
I'm guessing the Phoenix has plenty of flare above water to give it the solid stability on edge. Have not paddled / seen one, just guessing. It is probably also a wide (by kayak standards) hull.
A roundish hull, especially with a lot of rocker usually translates to deeper draft and a craft that gets pushed around by cross currents and waves more. Creek boats are an example. The river runners with flatter bottoms and less rocker tend to slide over currents (with minimal to no edging applied) so they are unaffected, until you edge them to engage the rails/hard chines.
A round bottomed Perception Pirouette or a Dagger RPM I think are more affected by cross currents and eddy lines turbulence than a flatter bottomed Dagger Axiom or a Jackson Zen for instance, as long as you keep the flat bottom boat flat (edge it, and it tracks straight and gets grabbed by the current to assist in turning or getting out of a hole).
Similar for the P&H Delphin vs. the WS Zephyr in moving water: the rounder deeper V on the Zephyr makes it more "twitchy" on center but with good secondary on edge. The Delphin is more solid on center and with also good secondary. But currents affect the Zephyr more than they do the Delphin. The Zephyr is smoother on choppy wind waves... The Delphin can engage the rear and front rails with edging, the Zephyr does not have them...
Based on reviews …
The Nordkapp LV has higher top speed (important when fighting currents) and lower wetted surface (important for efficient paddling). As long as one is paddling the Nordkapp in conditions where they don't feel the need to brace much, it will be more efficient/speedy than the Cetus, I believe. You might get tired quicker and develop better paddling technique and core strength in it though :)
Both great boats, the Cetus (MV) I think is the one I would pick between he two for most situations if I had a choice and it was a bit lighter. The Nordlow is a more challenging boat that only pays dividends in special cases for experienced paddlers and might be too much to handle in other situations. So yes, I agree with you that a boat like the Cetus line, that is reassuring and not twitchy but still performs well, would be a better choice for most in most situations.
If speed isn’t important . . .
. . . I can’t think of any good reasons FOR ME to have a twitchy hull.
Non-twitchy hulls have always been fast enough for all the various types of paddling I have done, including open and decked whitewater, seakayaking, flatwater open canoe, and outrigger canoeing.
Of course, twitchiness is as much a subjective as an objective phenomenon. With experience, hulls become less twitchy. My current stable hull might have been my younger self’s twitchy one.
Until with age, everything becomes more tremblesome again.
A friend of mine who owns a Nordkapp LV, among other boats, is vaguely thinking of the Cetus LV precisely because he thinks it is faster. (Less rocker on the Cetus?) I have no opinion myself other than that any difference in speed is likely to be minimal and undetectable.
Stiff and twithcy
As Glenn has pointed out there comes a time when twitchy is no longer tolerable. The supple youngster compensates for twitchy with smooth quick body movements. The old guy can no longer move quickly or smoothly and will be, at best, uncomfortable with twithcy; at worst he’ll be wet. Finally, rigor mortis sets in, you lay him out in the bottom of the boat and twitchy does not matter.
not just speed
Twitchy, to me is just a pejorative way of saying “easy to edge”. Flat bottom boats like the Delphin or Cetus take more paddler input to put on edge. The Nordkapp is much easier to edge with your butt. I think “twitchier” boats allow a more intuitive body-boat connection, but every good thing has it’s extremes, and at some point that “easy to edge” feel may turn into “too hard to keep upright”.
Twitchy is not a hull characterisitc…
Speed (oops - hull resistence) to accelerate, cruising speed and degrees of heel are oft-measured hull characteristics. Twitchy is in the eye - and butt - of the paddler.
Seriously, twitchy only matters if it is so severe that the paddler can't get comfortable in the boat. But making it more important than the total package will stop you from experiencing a lot of very nice boats.
The sweetest ride in our basement is probably the twitchiest, which makes it a poor choice of boat on days when we are not on our game. But on days when everything is clicking, it is a fast, responsive wholly enjoyable boat to paddle.
I have to ask - why the focus on the Cetus? There are a lot of boats out there which are on the more comforting side. I respect the P&H boats, even have one for my main ride, but I have to wonder if this a troll for a kayak company?
at the local races, a guy who paddled an Olympic K1 tried out a friends V12 and sat on it like a rock. I could barely stay in the V12 when I demo’d it.
How many people do we see on here saying “I have a penobscot and think its unstable. recommend a stable canoe for me” I always laugh at those. But just to echo your point, stability is in the butt of the beholder. I know as I have gone towards lower stability boats they keep feeling more stable all the time. My next boat is going to be a V10, so Ill take another step down the stability ladder, until it feels stable…then who knows…
I agree, it’s a subjective quality and mays say as much or more about the paddler as it does the boat. As willi mentioned, load or freeboard can make a difference as well.
Celia wrote: “Speed to accelerate, cruising speed and degrees of heel are oft-measured hull characteristics…”
Twitchiness is also a measureable hull characteristic. See the Sea Kayaker stability curves, for example.
Celia wrote: “Seriously, twitchy only matters if it is so severe that the paddler can’t get comfortable in the boat…”
This is not true. Even moderate twitchy can be moderately undesirable. Twitchiness may not be the most important aspect, but it might have moderate importance.
Celia wrote: " I have to ask - why the focus on the Cetus? …"
Sorry, I did not intend to focus on the Cetus, just an example. The Tiderace Xcape or Xcite are very similar examples, and relatively un-twitchy.
Yes, that’s it.
Those words mean the same thing, and they definitely ARE a characteristic of hull shape, and one that could be quantitatively measured if one wanted to. The point has already been made that a “twitchy” hull (or tender, tippy, whatever) has other characteristics that may be desirable for certain purposes.
The Phoenix hull has little flare
above the water line, especially with me in it. It always surprised me how stable it feels, more stable than my Hahn, which was roundish but with more rocker. The Phoenix did have that problem with roundness, because it didn’t ferry well and raising an edge to confront oncoming current didn’t work.
You’re right, flatness and edges are a good thing once one knows to edge the boat to help water pass under. After a while, it seems to happen most of the time without thinking about it.