Is there a discussion or article anywhere that goes into detail on rocker and its impacts on a kayaks capabilities?

If so, can somebody point me to it?

If not, can folks dump their knowledge & thoughts here?
- How much is enough? too much?
- when do I want more? When less?
- rocker comparisons of popular fishing SOTs (WS, OK, LL, etc...)

Thanks!

That's a big topic with many subjective elements. If you only paddle flat water, you don't need any. If you spend a lot of time in the surf, you'll want a lot. More rocker decreases the speed benefits of length (less of you're kayak is in the water).

The new Hurricane Phoenix 16 was recalled shortly after its release because of complaints by outfitters who said that it didn't paddle very well due to too much rocker.

In addition to what Santiago said, too much rocker will keep a kayak (and canoe) from tracking straight.

Here is a decent place to start if you want to get some basic info about design:

http://ftlauderdaleyakfishingclub.org/yakdesign101.html

( another hit Jimbo, compliments of RR)

also, read excerpts from The Shape of the Canoe by John Winters... its been called the "Bible" of Yak and Canoe design.

To be even mentioned with the great John Winters is a compliment, thank you. I do want to say this about rocker, or any other individual design factor, and that's this:

It's hard to generalize from any one factor.

Rocker is no exception. Here you have read that rocker is not needed in flat water, also that rocker slows you down. Yes and no. Rocker aids in turning, and sometimes it's harder to turn in flat water. Rocker helps in turning - something we need in all conditions.

Technically rocker does shorten waterline length, and technically this affects speed - in perfect (read non-existent) conditions. In real world conditions we are constantly being knocked off course and being able to correct (turn) efficiently may increase your speed.

So it's really hard to generalize. One must look at a design as a whole - can it be lean turned and how does the hull design promote or retard turning? Hard to say. Each kayak is different. Does it have a built-in skeg? How do the sponsons engage the water? How quickly? How much windage in the design? Ad infinitum.

Frankly, I find most rec designs, the kind you're probably considering have too little rocker (in general). They also tend to have built-in skegs, and large engaging sponsons.

In real world, often rough conditions, rocker is a good thing. The Scupper Pro/RTM Tempo is one of the few designs with really decent rocker and is a great all-around design. The RTM Disco has excellent rocker and is a very, very fast and exceptionally seaworthy design.

But still I hesitate making any blanket statements. Winters promotes less rocker than most designers, yet his designs are very well respected performers.

The bottom line is that rocker is one of many considerations. Kayaking is a learning experience and you will find yourself growing everyday, changing your opinions.

Well stated Jimbo, I hoped that you might show up with some comments.


A snippet from Ocean One Kayak's website:



As far as hull shape is concerned, a full waterplane and higher volume stern and bow sections are yet another design feature I felt was very important to incorporate into the kayaks in order to qualify them as 'seaworthy'.
Waterplane refers to the shape of the hull where it intersects the surface of the water (at ANY draft of depth!). Its shape affects the volume at the ends of the kayak and thus contributes to stability, buoyancy, performance in waves as well as safety. You may have noticed that many kayak designs have a distinctly slender or 'pinched' ends (top kayak in the picture below) with the middle of the kayak 'bulging' out. This may give the design a certain aesthetic appeal but it contributes nothing to its seaworthiness.




As a wave passes under the kayak, under some conditions, the middle of the hull is 'out of the water' and the stability and buoyancy of the kayak literally hinges on the bow and stern sections which are now sitting in the peaks of the wave (picture below). Submerged low volume tips do not provide buoyancy or stability and the kayak will feel tippy and unwieldy. Full waterplane shifts the internal hull and deck volume toward the tips which enables the bow and stern to ride over the waves rather than slicing through them.




This issue also goes beyond stability and the inconvenience of a bucket of heavy sea water landing in your lap. Buoyant bow with a rocker (curvature of the keel at the bow) reduces the tendency of a kayak to 'broach' in following seas. This means that when you paddle with the waves coming at you from your back, and when the wavelength of the waves is about 1 to 1.5 times the length of the kayak waterline(LWL), the bow buries itself in the wave trough (while the stern is over the peak and out of the water) pivoting the kayak sideways and flipping it.







The Double, Storm, and the Expedition have full waterplane and high volume ends for that reason. The volume associated with full waterplane has otherwise no influence on speed because it is largely 'out of the water'.

High performance cruising and touring kayaks on the open sea also require a long waterline for speed, good directional stability as well as paddling comfort. The shorter the kayak, the more it yaws (turns left and right) with every paddle stroke. A lot of paddling energy can be wasted on course correction alone not to mention the frustration when this goes on and on. A longer kayak is said to have a larger Longitudinal Inertia (Il) or resistance to this motion.
A long hull has also a larger submerged 'lateral plane'. This gives it a bigger bite in the water to resist turning while the kayak is upright. Leaning the kayak on its side, changes the shape and size of the plane which allows the paddler to turn and maneuver.
The same goes for pitching (rocking back and forth) in waves. A kayak with longer waterline and waterplane passes over shorter waves without being caught in them and 'rocking' with them. The long distance between the paddler and the tips of the kayak creates an effective arm (lever and moment) to lift the bow out of the water with less effort, giving you a much drier ride in waves than in a shorter kayak.

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I hoped that my cut and paste would include the graphics from the site as well... good visuals at the website. The piece I post talks about more than just rocker, but all aspects impact each other in someway, so its a good little read.

quote:

Originally posted by RiverRaider:
Here is a decent place to start if you want to get some basic info about design:

http://ftlauderdaleyakfishingclub.org/yakdesign101.html

( another hit Jimbo, compliments of RR)

also, read excerpts from The Shape of the Canoe by John Winters... its been called the "Bible" of Yak and Canoe design.

I have to second that recommendation. Capt. Jimbo's site is probably the best place to answer design question like that. Beware the the over simplified answers (including mine).

A-W-E-S-O-M-E info folks - very glad I asked!

quote:

Originally posted by Socrates_thinks:
Frankly, I find most rec designs, the kind you're probably considering have too little rocker (in general).

I own a Heritage Redfish 14' and it seems to me like it is at the low end of rocker for rec kayaks (complete guess). It gives me some concern over surf launching/landing and big-water-worthiness (flat water is much more of the norm for me, but I'd like to try the ocean and feel confident in my chances). I'm contemplating things I might want to be different in my next boat, and since (lack of) rocker seems to be the most exaggerated feature on the redfish I thought I start contemplating there.