Can someone explain what my favorite rocker is called? I perfer to shape my boards with Type A Rocker (see sketch).
I hear terms like natural rocker and progressive rocker, but I’ve never been certain what those terms mean, or what my favorite style rocker (Type A) is called.
I don't know the "lingo" per se, but looking at your drawing, it doesn't look like a consistent radius throughout. To me it looks more like a portion of an ellipse than an arc of a circle, because the curve seems to wrap more toward the nose. I have seen longboards with a very consistent arc from tail to nose, and some where the upward curve is tighter in the tail instead of the nose.
It would be interesting to see if there is a consistent terminology to describe rocker. I kinda doubt it, based on the fact there is really not even a consistent methodology to measure rocker.
Anyway, I consider rocker a key element of surfboard design, so I'm always eager to learn more about the way different shapers approach the subject.
I little background on how I started using this rocker…
I measured a lot of windsurfers and measured some surfboads by a famous shaper who is also famous for windsurf shapes. I found one thing they all had in common. Type A rocker.
I confirmed the constant radius arc by taking measurements of these boards, then redrawing in my CAD software. There was a defined single radius arc from the middle to the tail. The middle to the nose, was a different story. There it was an increasing radius arc, typical of an ellipse.
There is often an accelerated curve towards the tail. A tail flip. I was doing them for a while, but there is too much of a projection loss. You can flip the board vertical, but you won’t get very high, because you loose too much speed off the bottom.
A good stable fast board has a steady curve out the back, with just a slight acceleration. maybe 1/8" in the last foot. Any more than that is detrimental.
Rocker is the utmost important figure in the equation, outlines are a dime a dozen, fin placement is a very close second, almost a tie for first and rails a lowly third.
I get so f’n amazed to watch someone stand a board up and say, “bitchin shape”, when I see gazillions of boards coming at me on the highway and the f’d up rockered ones stand out like a sore thumb.
Tinker would tell me about John Peck’s rocker, “Peck’s boards bottom rocker is a curve from a giant circle, no matter where he stands on the board, the water hits it at the same angle, no one sweet spot”.
Just about every shaper / designer, does about the same noserider rocker, flipped tail, close to the end and a reduced nose rocker for ease of glide.
The short boards are inner changable, with only minor variations in the outlines, rockers, foils, the parameters of what makes one work well are so narrow, that there isn’t much room to be on a tangent.
I use Rooc Rocker for all of my surfboards...........Right Out Of Catalog......
At 5 boards per year I'll never get to Jim's level. Do you study the Clark and U S blanks rockers? It's all out there on the internet. You can't test drive in CAD. Build em ride em. I have an extra heavy board that is working good and A board that I thought everything was perfect that is a dog. I moved the fins forward 1.5 inches on one board and it went from dog to good. When I stopped trying to build the perfect magic surfboard things got better and more fun! Your type A rocker came from a famous shaper. I bet he had a blank in the Clark line up!
Now you’ve done it.
Opened one BIG can of worms.
This is heady stuff.
You have NO IDEA how heady until you pull up the “Rocker Apex” thread.
Good luck, bring along some aspirin once Bill (Barnfield) and I kick into the fray.
Happy 4th everyone.
lol…understand and create rocker is only for crazy people…normal people just copy the good ones…lol
But horsemouth, that would be like watching T.V because you can’t read??
A couple of years ago I shaped 2 identical boards, each with 2.5" of tail rocker. One was like rocker B, the other like rocker A. Rocker A was faster and all around sweeter. Now when I encounter rocker B, I fix it and make rocker A.
To my other question, what does progressive rocker mean? Marketing BS or something real.
good analogy…Jokes aside, my litle experience on tail flips is that you need to compensate it in other part of the design…They are great for aerials…perfect with very low entry rocker…Straighter tail curves IMO asks for more entry so you still have your nose free for climbing to the lip…I also love tail flips for hollow waves late take offs…there is no good or bad…endless possibilities…thats why I said its for crazy people…lol…there are no words or numbers to translate the multidimensionality of a wave…
A. Continuous
B. 3 stage
C. Blended
D. Is John's (Pecker) Spherical maybe?
OK, I watched the interview. And noted Roy's comments as well =). The video seems typical of what results when there is no real standardization of terminology. I could be wrong on this, so feel free to correct me.
First of all, he talks about "spherical rocker", and Roy uses the term as well. But unless a board were an extreme hull, I don't see the rocker being a portion of a sphere, I see it being an arc of a circle. A circle is a geometric shape in 2D. A rocker is a geometric shape in 2D. A sphere could be described as a circle spun around an axis so that it inhabits a third dimesion. But any cross section of a sphere is a circle. So a "spherical rocker" is just a fancy way of saying his rocker is an arc of a circle, with a consistent radius.
Then he talks about having an inch more rocker in the tail, but an inch less in the nose. But as Surfding has pointed out, choosing different reference points can make the exact same rocker sound radically different. IIRC, rocker descriptions for the CNC will have equal measurements front and back, with the location of the apex being the difference, whereas old school methods will have a greater mesurement in the nose.
So, taking the picture of rocker A in the first post, and tilting the board forward until the nose and tail are equal distances from the tabletop, could make it sound like you've added rocker to the tail and taken it out of the nose - when all you've done is move the apex location for reference purposes, and haven't altered the rocker at all.
Above is a picture Barnfield posted in the rocker apex thread. http://www2.swaylocks.com/node/1009636
Stretch is an experienced, qualified shaper that makes great boards. But his descriptions of rocker, to me, seem vague and (maybe purposely) a bit confusing.
He talks about the face of a wave being a "perfect curve" - what does that even mean? Breast augmentation plastic surgeons like to use the term, but geometrically speaking, does such a thing as a "perfect curve" even exist? Malaroo? In addition, is the curve of a breaking wave always consistently the same? I say it can't be! Waikiki vs Teahupoo, for example.
He talks about a flatter curve through the mid section as being a better rocker for down the line surfing, and a continuous arc being better for vertical surfing. That sounds logical to me. The old flat longboard logs with almost no rocker seemed to trim pretty well down the line, but the constant turning up into the lip and back down the face seems to require a more modern, consistent radius rocker. Whether that's because of the curve of the wave's face, or the need to constantly be turning, I don't know. Maybe a combination of both?
Always good to hear what an experienced shaper like Stretch has to say, and everyone has to interpret and draw their own conclusions. But getting back to the initial question, is there a consistent terminology to describe rocker, I would say no. But I'm guessing the CNC will have, or is having, the effect of forcing shapers to quantify rocker in more exact terms.
It would be nice to take descriptions of rocker out of the smoke and mirrors realm, and into the realm of measureable geometric curves. At least for talking purposes, if nothing else. Some way of quantifying a description of a curve into something more useable than "more rocker in the tail but less in the nose".
I don't see rocker as the be-all do-all of surfboard design, but IMO it is one of the most critical aspects, and I doubt I'll ever agree that rocker doesn't matter once you throw rails tails fins and channels into the equation.
description of rocker is what i have had the most arguements over, you can have the tip numbers the same and have radically different lines along the bottom.
The straight edge along the bottom, 3 different people can come up with 3 different measurements on the same board, where exactly is it in relationship with dead level ?, the most accurate would be bottom down on a true flat surface, letting the board itself find its own true center, then measure the tips.
Carl Olson and I had a disagreement on what are the numbers of a 12 footer I do, I said I have no idea as to what the numbers are, he said I couldn’t get a good riding board without knowing the numbers. After shaping a gazillion boards, you look at the bottom curves and know what is going to move through and across the water is a clean friendly manner.
I have a bottom rocker temp for the SWT’s, in the beginning I used it on each board, but soon realized that when I picked it up, it was going to fall on those points anyway, as that was the way I shaped the first ones and liked the way the tail flip and long nose rocker played out.They were all glued to the same rocker each time, only when a radically different blank of extreme thickness is used and the rockers have to be adjusted to compensate for the extra center thickness or the bottom will be more curved. So much for the rant, time for meds
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description of rocker is what i have had the most arguements over, you can have the tip numbers the same and have radically different lines along the bottom...
Carl Olson and I had a disagreement on what are the numbers of a 12 footer I do, I said I have no idea as to what the numbers are, he said I couldn't get a good riding board without knowing the numbers. After shaping a gazillion boards, you look at the bottom curves and know what is going to move through and across the water is a clean friendly manner...
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Yes that's true - tip numbers are just two reference points along a continuum with a potential for infinite reference points - at least every 6" or so would be more meaningful.
I'm a visual person, having trained as a graphic artist, so despite not having shaped a gazillion boards, I use pretty much the same method as you do for determining rocker, and have had good success. Probably helps too that I pay close attention to the rocker on other boards, created by shapers who have shaped a gazillion boards.
I make it a point to study rocker shots whenever someone posts pics on the internet. Some of the surfboard companies have template and rocker shots of all their models, which I find invaluable. Also, blank catalogs (sure the rocker on a blank may not be the exact rocker of a finished board, but its gonna be close, thats the point of putting the rocker into the blank).
The advantage of the shaper who works with rocker daily, hand or cnc, is that he can tweak a rocker to learn how slight variations affect performance, whereas the garage hack like me isn't doing enough boards, or (in my case) getting out on my boards often enough, to distinguish between minute variations. But thats OK, because if I could make those small improvements in the board as a shaper, I probably wouldn't know the difference anyway, as a surfer, LOL.
My idea of a progressive curve is a smooth curve where the radius gradually decrease/increases along its length, some examples would be cissoids, elipses or even french curves, I think these type of curves are very important in regards to fluid flows.
I’ve watch Jim’s shaping videos and seen the end product and although I haven’t seen one close up I’d bet that you won’t find any humps or bumps in Jim’s rockers, where the rocker changes radius he makes sure the changes are ‘progressive’ and smooth, this ensures no sudden detours for water to either dam up or release from. The water gets from nose to tail in the most efficient manner possible for the required functionality of the rocker (Hope I’m right in my observations of your work Jim 
)
This is why I like Malaroo’s geometry theories and methods, have a look at how he produces the initial rocker and how the final rocker is produced, nice constant, smooth and progressive curves.
In the nose a progressive curve (raduis increaing gradually from nose to centre) should help the board get up on plane better/faster, once the water starts to ‘climb’ the nose curve it gets easier and easier until it is finally on plane. The water doesn’t have to climb and then run into the transition from nose to middle board rocker, it’s all smooth.
Similar thing with the tail only think more about release/suction, faster progressing curves towards the tail = more suction while softer curves help the water along the tail and off the board smoothly.
If you surf hollow waves you can use a bit more aggressive tail and nose rocker as the water does follow the curve of the wave face to some extent making the ‘matched’ wave and rocker radii cancel each other out (i.e. no penalty for more rocker like you would get the same rocker in fuller waves)
Of course with my limited experience that’s only my interpretation of a good rocker and it may be all wrong.
I have an idea for measuring rocker, at least as a way to document it so it can be replicated and templated, I’ll knock up a drawing and post it soon.
Mick.
Here’s my method of measuring rockers for documentation/duplication.
This method requires no special tools although it wouldn’t be hard to make up a special straight edge if you did this on a regular basis.
The beauty of this is it’s simplicity and consistency, you only need to find the middle of the board over the curve, set out your packers, place straight edge and measure.
If you really think that having the packers that far apart is excessive you must have a real funky rocker in the middle of your board, if so put them as close together as you like as long as they are equal and at least some distance apart to produce a good tangent with the middle of the board.
Packers made of angle iron would be ideal.
p.s. yes, that should say ‘identical’, it’s been a long day 
There is definitely a lot of (infinite?) curves to choose from.
Parabolas, ellipses, spirals, strophoids, hyperbolas, cardioids, limacons, astroids, nephroids, deltoids, cycloids, strophoids, tractrix and catenaries to name a few types. You can also make new ones.
I've noticed there are some java apps that will generate the more studied curves (just plug in your basic parameters and they will produce the curve in most formats for CAD, or plot the raw graph numbers.
Edit: It is interesting comparing different curves to known rocker shapes. I'm not sure if shapers are aware they are close to or using a particular curve or curves. I guess someone like D. Brewer, with his A grades in calculus, has explored a range and knows roughly what his contours are (rails, deck, bottom etc.)
I think of rocker and foil in similar terms… In shortboards, rocker curve changes from apex to both ends, but the changes are at different rates. Same with foil, where the nose ends up thinning to zero, while the tail thins to, well, something greater than zero. Move the apex fore and aft, and the rates of rocker acceleration and thickness flow change yet again.
I think the term progressive rocker addresses the cange in curve… the acceleration from a larger raidus curve in the middle to tighter radius curves toward the ends. If you take your planer and make an end-to-end pass at a continuous speed starting with it full open, then close it to zero at the apex, then open it up to full at the other end, you’ve just tightened the radius of the whole board in a continuous curve. But if you start with it full open and close it quickly at first, then more slowly as you approach the center, you’ve “accelerated” the rocker… changed it’s curve in a “progressive” manner. I refer to that change in curve as “flip” in the nose, and “kick” in the tail. They all have to come together with no bumps or abrupt changes in curve, and they have to blend into the different rockers of the board… stringer rocker, rail rocker, and deck rocker (foil).
I’ve had great success with this approach for different types of boards and different types of waves, changing the amount of acceleration and where the acceleration starts. But I rarely use a continuous curve in shortboards anymore, even “retro” type boards.
