Rocker curves

General Discussion
1

Widely considered the foundation of board design.

How many types or categories of rocker are there?

Continious,

2 stage

3 stage

any others?

What are the pros and cons of each one?

Seems most modern boards (i see on the rack) have some variation of a continuous curve.

What do you guys like to shape? Any preferences?

How much?

Me personally i like a somewhat continuous curvy rocker sort of a toned down version of the norm in the 90s…my 6’8" has 2 1/2" at the tail after the concave…how about you guys?

Adjustments…how much do you have to add or take away before you can feel a difference? 1/16? 1/8? more?

Any idea on how stringer rocker relates to rail rocker when using concaves or vee? Seems the rail rocker is the most important but how much does the stringer rocker factor in? Any thoughts?

2
Quote:

Widely considered the foundation of board design. …Mmmm, I start with the template, not the rocker…

Seems most modern boards (i see on the rack) have some variation of a continuous curve.

…Because sudden changes in water flow/direction cost energy, which can be hard to regain. We have mostly only the height of the wave to work with, we’re energy limited.

Adjustments…how much do you have to add or take away before you can feel a difference? 1/16? 1/8? more? …Depends on how sensitive you think you are. I propose that most of us could not differentiate between two boards with as much as 1/2" overall rocker difference, partly because waves are so different from each other, you never get to duplicate a ride. Besides, boards with different rocker usually have other differences also - it’s never “other things equal”.

3
Quote:
Quote:

Widely considered the foundation of board design. …Mmmm, I start with the template, not the rocker…

Seems most modern boards (i see on the rack) have some variation of a continuous curve.

…Because sudden changes in water flow/direction cost energy, which can be hard to regain. We have mostly only the height of the wave to work with, we’re energy limited.

Adjustments…how much do you have to add or take away before you can feel a difference? 1/16? 1/8? more? …Depends on how sensitive you think you are. I propose that most of us could not differentiate between two boards with as much as 1/2" overall rocker difference, partly because waves are so different from each other, you never get to duplicate a ride. Besides, boards with different rocker usually have other differences also - it’s never “other things equal”.

Maybe if i rephrase that first part to most important?

1/2inch strikes me as quite a bit…even 1/4 is noticeable to me…everything else seemed to measure the same.

4

Hmmm…anyone else want to take a swing at this?

5

This is a really interesting question - someone like bert or greg should know - please enlighten us amateurs.

In my experience - I think i can feel an obvious difference at 1/4" at the tail -

Is the move toward continuous curves just fashion or do they create less turbulence?

6

A 1/4" will be noticable anywhere along the average wetted surface…under your feet…“overall” is likely not noticable.

How’bout “dual-continuos” and “dual-staged”…on moderate/deep concave boards, stringer and rail rockers differ. I recently borrowed a CI Flyer for evaluation and it was a very enlightening experience…looking at the profile, the board has heaps of rocker but when looking at the stringer its very relaxed and smooth…speeeeed and maneuverability in one neato package.

Al Merrick makes some insane boards.

7

I downloaded the rocker specs from “Essential Surfing” into a mathematical program to attempt to see what mathematical form rockers tend to take.

The first thing to notice is that curvature is anything but constant. There’s a lot of curve at both ends, and the boards are comparably flat in the middle. There’s a little more than twice as much front rocker as rear rocker.

That was the consensus shapers came to a few decades ago. Boards are curved at the ends, and not in the middle. And the rear is much less curved than the front.

I tried polynomial fits for front and rear rocker. They are at least third order fits, a 3d degree polynomial is adequate. They could also be hyperbolic - I kind of liked the idea of hyperbolic fits (where the rocker asymptotes to a fixed slope), but the reality is that it is just a fairly simple curve. There was not really enough data to determine if the curvature decreased at the very end (as though it were asymptoting), or not.

1/4" in the rear will be quite noticeable. The front probably would take 3/8" or 1/2" to make a clear difference, sometimes the nose just gets flipped a little more.

Merrick led the way with a lot of rocker as Slater was the dominant pro surfer, using 1/4" or 1/2" more than the standards of the time. But, if you have a 1/4" deep front foot concave that flattens through the tail, that effective adds 1/4" to your rocker as seen by the rail/tail combination (the points of contact in the turn). So the numbers can be misleading.

8

outline is the least important, the best of outlines will be sunk by a poorly engineered rocker

9

jim first , your comment could be reversed and equally applied…

for me 1/8 and im liking more or less …

but it depends on how you spread that 1/8 …

if you put and extra 1/8 in the last 3" of the tail ,it would be much more dicernable than 1/8 that was blended from the centre to the tail…

you would feel both , but the first one more…

i agree about merrick…

he has a real handle on design . plus hes got the business package as well…

when i was younger i was led to believe , you had to change rocker to make your board tighter or looser…

i dont belive that anymore…

ive had boards where i increased the rocker and they got stiffer??? yea work that one out???

it comes back to the blending of all the variables to set it up with a theme…

a good small wave board needs all the variables focused on small waves…

same , a big wave board , needs all the variables focusing on bigger stuff…

when you get your variables mixed up …

you can end up with a dog , that doesnt work in big or small stuff…

its a very safe to use clean continuous curves , that slowly accelerate or straighten , depending on the application…

as a general rule , the fastest part of your board is the flattest…(provided the other variables are tuned in), so if you want speed while standing up front , put the flatter part there…

if you want speed while standing on the tail , move the flatter region there…

but always keep it clean and flowing…

i just chucked a pic in of a bunch off different rockers…

i sent a guy a rocker pic of his board in an email, i just cut it out of this photo,these were the rest on the racks…

i think theres only 2 boards on the rack with the same rocker, coz they share a common theme…

regards

BERT

just a few more pieces …

10

This essay with illustrations is a brief overview of rocker options in surfboard design.

http://www.naturalcurvesboards.com/html/designhtml/rocker.html

The reference to “hybrid” rockers is not to be confused with the rocker of a “hybrid surfboard.”

Concaves and vees are a result of varying the curves and placement of those curves in “bottom or stringer rocker” and “rail rocker.”

Generally, I prefer continuous rockers in longer boards and staged rockers in shorter boards - the continuous rocker seems to help longer rail lines fit in and turn tight in the pocket - the staged rockers seem to add the speed and projection required for maximum performance from shorter boards.

Certainly, both rockers may be modified (adding some flatter curves to a continuous rocker profile or smoothing the transitions of a staged rocker profile) to enhance and upgrade the performance of a board.

11

Hey Bert can you give us some insight into your rocker design like the differences between those rockers pictured and their application? From looking at that picture I really like the profile of the longboard and the 2 boards below it 4th one looks really flat and the last 2 at the bottom look like the have quite a bit of rocker.

12

“Merrick led the way with a lot of rocker as Slater was the dominant pro surfer, using 1/4” or 1/2" more than the standards of the time."

well actually i think it was webber and herring that lead the way there, kelly was just the better surfer! and mr merrick being the astute businessman/ designer too saw the benifits quickly of gregs extremes in rocker and toned them down enough for contest waves!

13
Quote:

“Merrick led the way with a lot of rocker as Slater was the dominant pro surfer, using 1/4” or 1/2" more than the standards of the time."

well actually i think it was webber and herring that lead the way there, kelly was just the better surfer! and mr merrick being the astute businessman/ designer too saw the benifits quickly of gregs extremes in rocker and toned them down enough for contest waves!

I think your right about Webber

14

interesting…i thought more people would have taken a swing at this thread shrug

15

I personally agree with Jim; I think there are 3 things that affect about 75% of a board’s performance (length, rocker and fin(s)). The rest is fine tuning and personal preference.

There are infinite possible rockers. I’ve found that a continuous curve is the most difficult to shape properly, is user friendly, forgiving and perfect for boards that you want to turn quickly, need to bleed speed or surf in bumpier conditions. They don’t trim or drive as well in lined up conditions and need to be on longer boards or pumped to get down the line.

Staged rocker (to me) is a number of flats connected by shallow blended curves. This kind of rocker defines sweetspots or gives a board an accelerator. (These are the rockers that are most outline sensitive). They’ll trim and drive but can be pretty quirky to turn. These have been the hardest boards to surf for me, but once you get them wired, they’ll fly!

By mixing them up you can pretty much get anything kind of performance you want. Do a bad job and like Jim said, you’ll have dog.

I use fairly flat staged rockers because I surf short boards in pretty glassy reef surf up to maybe 1.5Xhead high. 4-5 inch nose rocker with 1.5 to 1.75 inch tail “lift” with the last .25 inch about 4 inches up from the tailblock.

I’m pretty sure a good surfer would be able to feel .12 to .25 inches of rocker in the tail, 1 inch in the nose and maybe .5 inch more curve in the middle of the board. But they would really feel the difference more by moving the “breaks” or acceleration transitions up and down the length of the board.

My experience would say that the stringer rocker is going to affect how a board paddles, catches waves, and makes drops more than the rail rocker. (a little kick at the tailblock really eases the steep drops but too much will act like an anchor) But the rail rocker is the key to how a board turns.

To me, the ideal board would have a flat rocker for paddleing and catching waves but would flex .25 inches at the tail on a steep drop, roll it up on edge and the rail rocker would flex about .5 inches over the last 1 to 1.5 feet. Whooooooooweeeeee.

…If it gets to be too much, you can blow up a mat and have auto adjust rocker…

16

Yes great post.

Quote:

I’m pretty sure a good surfer would be able to feel .12 to .25 inches of rocker in the tail, 1 inch in the nose and maybe .5 inch more curve in the middle of the board. But they would really feel the difference more by moving the “breaks” or acceleration transitions up and down the length of the board.

I agree…

Ive made 1/8in adjustments in the tail rocker and seemed quite noticeable to me

Generally when looking at a shortboard off the rack i.e. a Merrick or similar board you can see from the break near center a fairly smooth acceleration towards the tail then another accleration somewhere between your feet or just before the fins and another between the fins.

Im wondering how moving those acceleration points affect performance?

17

To me, the location of the “breaks” or changes in the curves are the key to modern tri-fin high-performance boards. The locations are probably as significant as moving fins around. I’ll bet that, before the shaping machines, that is why you had “magic” boards; puting those breaks in exactly the same spot by hand is pretty tough stuff without rocker jigs…except maybe for LeeDD ;D

18
Quote:

……

My experience would say that the stringer rocker is going to affect how a board paddles, catches waves, and makes drops more than the rail rocker. (a little kick at the tailblock really eases the steep drops but too much will act like an anchor) But the rail rocker is the key to how a board turns.

To me, the ideal board would have a flat rocker for paddleing and catching waves but would flex .25 inches at the tail on a steep drop, roll it up on edge and the rail rocker would flex about .5 inches over the last 1 to 1.5 feet. Whooooooooweeeeee.

…If it gets to be too much, you can blow up a mat and have auto adjust rocker…

Here’s another example of “auto adjust rocker” lying somewhere inbetween a mat and a conventional board.

It’s my present small wave shell-type kneeboard – “Cypselurus II” (it’s vintage 1993–but following the same basic concept that I’ve used since 1969). The planform is illustrated in the upper view of the attached pic. It’s pretty rectangular (to maximize the wetted area and minimize induced drag in weak/slow waves); hard edges all the way around (again maximize planing efficiency); slight bowl in the nose (reduce edge-catching tendencies), side-to-side dead flat in rear (concave or convex curvature would interfere with the flex); and a twin fin (only forward half of the fins glassed to bottom to minimize interference with flex).

The middle view of the attached pic shows the “stringer” and rail rockers when riding “down the line”. Both are progressively decreasing from front to back, and essentially dead flat at the rear of the board. In short, in this configuration the board is almost fully optimized for speed (within the constraints of small/slow waves).

With the nearly parallel rails and broad tail, the board would normally be resistant to setting up and executing carving turns, and hard turns would require considerable weight-shifting by the rider. This problem is mitigated by introducing rocker into the rear portion of the board when turning by allowing the tail segment of the board to flex and “roll up” the rail–as illustrated in the bottom view in the attached pic. This flex results in reduced dynamic lift from this portion of the board, reducing the effort required to set up the turn and automatically shifts the center of lift of the wetted area of the bottom of the board forward (again assisting in the execution of the turn).

Note that the “stringer rocker” remains essentially flat both when racing across the face of the wave, and when carving a turn. Note also that the pressure on the bottom of the wetted area is always positive, so that loss of planing efficiency is minimized even when turning and rail rocker is present (not always the case with static rail rocker).

The shape of the rail rocker, and the “spring” constant(s)" of the flex is(are) determined by the planform and thickness of the foam/glass overlays, and by the fiber orientation, cloth weight, and number and planform of the layers of glass on the tail area (the central “stringer” area being quite stiff). The flex shown in the bottom view requires considerable loading, so that the rail rocker is minimal or negligible when trimmed for speed. In general, the desired degree of flex is related to the size of the waves to be ridden.

MT

682×633 86.4 KB

19

Whoa!!! I wouldn’t want to go over the falls with that tail whirling around like a rotary lawnmower. Are you using the tail cut out to keep the stinger rocker stiffer? Or does it serve some other purpose? Glad to see the Skunk Works are still up and running…

Are you flexing the mid section (the red area) too. It looks spooned.

20

Thats interesting…how thick is that tail section and what is it made out of to get that flex?

That tail section does look dangerous of you got clipped by it…

So how does it ride?