Staged vs continuous rocker.

Mr J

Michael Peterson status
Aug 18, 2003
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Thanks for the clarification. I guess I would have called that "planing" rather than lift , but a quick google says it is lift.
But now your apex term is confusing me. Is that where you perceive the rocker changes more drastically? Would staged rocker have two apexes? Also doesn't rocker apex change position depending on where you're standing on the board, like Mr. J mentioned above? Would you call your rocker continuous or staged?

In pedagogical terms, you need to create some "scaffolding" for us slow learners...
Greg, is right that no foil is involved - foil normally means dual lifting surface of top and bottom (which as you said Bernoulli's equation can be applied). As mentioned earlier our boards have a single lifting surface so they plane. Both foil and planing hull produce lift - upward force.

Regarding your direct question to Greg asking him if his boards have staged rocker - direct questions rarely yield a direct answer from our guru, but occasionally I do ask them! I asked that question before and I could tell from the indirect answer that Greg's rockers are what we could call staged in the tail. I had framed the question referring to one of the rocker shots he posted which strongly suggested this. I don't know how Greg does his tail rocker in shape3d, but this is how I have done 3 of my annual builds. The first pic is showing the default control point which shape3d will provide when designing from scratch. The "red" handle (not highlighted) at the end can be pulled up or down to get a certain rocker number then then the blue handle which is highlighted can be pulled up or down to adjust how gradually the rocker rises as it reaches the tail. That alone can produce variations of what I would call continuous curve.

The second pic shows how I have added an additional "elbow" control point to produce a stage. There is just a very slight bend in the elbow, but mainly the middle red handle pins the rocker at that point allowing the default end handle to keep the end stage flatter than it would normally be. I don't add such elbow control points in the nose entry section and would be surprised if anyone else does, but I don't know that for sure.

Other ways of staging is to have continuous rocker at the stringer, but stage the rail rocker by pulling the edge down into a deeper concave in the front fin region, but we know Greg doesn't do that. I did a bit of that on last years build and did not like the result i.e did not ride well for me.
DefaultTailControl.png
Staging.png
 
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Mr J

Michael Peterson status
Aug 18, 2003
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Reducing the apex reduces the lift in that area .

Entry angle on my boards reduces as it nears the center to none - the the exit begins ! ;-)
llilibel regarding your question of what that means and your suggestion of two apexes on board that was staged in both nose and tail, we can use the word apex however we want because we are not scientists, however unless we choose a common definition we will get confused when talking to each other. So in traditional rocker stick shaping and virtual 3d shaping the apex is at the mid point along the boards length (regardless of how the curve is distributed).

So what I think Greg means (in response to you saying concaving the middle can produce a "speed box") is that by reducing the curve at the middle point i.e the apex then the angle of attack in the nose section is reduced, the lowered angle of attack reduces lift in the entry section. Increased angle of attack is increased drag, which can lower speed, so that's where things get wooly and shapers use their intuition to decide how much. So I think Greg would be using the nose entry control handle to get what he believes to be the optimum balance of entry lift and "release of pressure" towards the apex to reduce drag towards the centre of the board. "then the exit begins" is I believe a humorous statement of the inevitable!
 
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Mr J

Michael Peterson status
Aug 18, 2003
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I have little to no understanding of this with surfboards but I have experience with wakeboards. I liked three stage rocker on wakeboards cause I rode steeper wakes and it translated to my riding style better. continuous rocker seemed to be better suited for mellower transition of boat wakes (manufacturer speciifc).
... .
I like staged tail rocker because it is an easy way of designing a board with a more "turny" feel without making it feel like a high rocker board. High rockered boards turn well but require powerful waves and/or continuously putting the board on rail and weighting/pumping to keep up the speed. Would you say that you have a lively wakeboarding style to make use of that "turnyness" from the stage in the tail?

This years annual build is both high rockered and staged! Its great in the powerful open ocean beachbreak and I am incredibly happy with it, but its not a good all round board. For every day sheltered cove conditions I always reach for my local custom - I have looked at it and not come to a conclusion on whether the tail is staged or not and don't know what the shaper intended. All I know it goes great from grovel to overhead!
 

Senor Sopa

Billy Hamilton status
Mar 11, 2015
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1) All curves have a tangent, this can also be called "apex". Rotate the rocker all you want, there is still always a horizontal tangent, somewhere.

2) One of Newton's laws, "Every action has an equal and opposite reaction". Know this, the foil on the surfboar is the sunken rail. The fin just allows the tail to bite deeper. The water bending around the rail is huge component of the "lift/hold".

3) Water is incompressible. For surfboars, the changing direction of the water flow is our action. For airplanes, the air is actually changing pressure. We don't do that, we redirect the flow. Water is relatively thick, small changes in flow provide lots of force. Do the spoon trick, or put your finger on the end of hose. You can feel how strong water is.

4) The only release is at two spots. Sharp angles and when the water can't handle the radius change. Turbulence can actually help prevent release, this is the golf ball stategy with dimples.

5) The Law of continuity. The water at the surface of the boar is going the same velocity as the boar. When the concave changes the direction of water flow ever so slightly, do the math, how much actual volume of water is redirected? That's your lift right there baby. F = d(MV)/dt = (V*dM/dt) + (M*dV/dt) => Bernoulli and friends.

000 posted a pic recently that show how much of the rail and bottom is actually engaged when just trimming. Fins are a small compared to the amount of surface area of the board itself.
 

PeterDj

Legend (inyourownmind)
Jul 11, 2018
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I think of continuous vs staged is the number of splines needed to make the shape. In more nerd talk its a piecewise polynomial curve. Less pieces would make it more continuous vs. more pieces makes it staged. Mathematically, they are all "continuous" otherwise it would have breaks in the curve. I guess a stepped hull is really the only non-continuous surfboard like the spyder fireball.
 

Mr J

Michael Peterson status
Aug 18, 2003
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1) All curves have a tangent, this can also be called "apex". Rotate the rocker all you want, there is still always a horizontal tangent, somewhere.
As discussed here and elsewhere you can consider the apex to be anywhere you want, but it will be only meaningful to you. For the purpose of comparing different rockers from different shapers/manufacturers a convention must be used.

2) One of Newton's laws, "Every action has an equal and opposite reaction". Know this, the foil on the surfboar is the sunken rail. The fin just allows the tail to bite deeper. The water bending around the rail is huge component of the "lift/hold".
that's a good point, when we do a deep turn we do have a little bit of top lifting surface from water wrapping the deck, so it could be argued that the submerged rail of the board is a little piece of foil. However I have looked down at my feet on a number of occasions and the water that wraps onto the deck is not very much. I don't think the water wrapping provides much hold because sharp rails grip better than rounded rails.

3) Water is incompressible. For surfboars, the changing direction of the water flow is our action. For airplanes, the air is actually changing pressure. We don't do that, we redirect the flow. Water is relatively thick, small changes in flow provide lots of force. Do the spoon trick, or put your finger on the end of hose. You can feel how strong water is.
At below subsonic speeds air is considered to be incompressible, therefore the same fluid dynamics equations derived from Newton's physics can be used. e.g reynolds number. The equation for lift on a simple foil has density, velocity and area, but not viscosity. So on face value it would seem that the extra force from water is the density rather than thickness. What is interesting is that the reynolds number which can be used to predict flow separation (the turbulence you mention below) uses kinematic viscosity which is a ratio of dynamic "real" viscosity to density. The kinematic viscosity of air is greater than water. Which I think might mean we get more real viscosity per gram with air - I don't really understand this stuff though. I might be talking nonsense.

4) The only release is at two spots. Sharp angles and when the water can't handle the radius change. Turbulence can actually help prevent release, this is the golf ball stategy with dimples.
Yes I agree about release happening from getting the fluid to turn tight corners - that's the usual definition which I think Greg uses for rails, but Greg also has his own additional definition of release to mean pressure reduction, or pressure release - if I understand him correctly. This has confused me a lot!

5) The Law of continuity. The water at the surface of the boar is going the same velocity as the boar. When the concave changes the direction of water flow ever so slightly, do the math, how much actual volume of water is redirected? That's your lift right there baby. F = d(MV)/dt = (V*dM/dt) + (M*dV/dt) => Bernoulli and friends.
that's above my intellect grade :D

000 posted a pic recently that show how much of the rail and bottom is actually engaged when just trimming. Fins are a small compared to the amount of surface area of the board itself.
(y)
 

ehiunno

OTF status
Dec 27, 2019
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I think of continuous vs staged is the number of splines needed to make the shape. In more nerd talk its a piecewise polynomial curve. Less pieces would make it more continuous vs. more pieces makes it staged. Mathematically, they are all "continuous" otherwise it would have breaks in the curve. I guess a stepped hull is really the only non-continuous surfboard like the spyder fireball.
These days I'm all about the non-differentiable rocker curves
 

casa_mugrienta

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Apr 13, 2008
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This has gotten too complicated for me.

I just wanna here stuff like rode X from shaper X and it felt like dung

or

rode X from shaper X and it was sick

or

if you want to rip ride X
 
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Sharkbiscuit

Duke status
Aug 6, 2003
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This has gotten too complicated for me.

I just wanna here stuff like rode X from shaper X and it felt like dung

or

rode X from shaper X and it was sick

or

if you want to rip ride X
$.02

I think you are making a point of going to good spots plus you can go midweek midmorning.

Lots of people with 9-5 M-F have a limited option set. It could be kinda mushy (most of North Florida, Central Brevard County), or has some steepness but is walled (South Bay, Palm Beach, Cerrado House and Sebastian Closeout).

You probably want something flat for the former and something mostly flat with some tail flip for the latter.

If you are surfing Blacks, Lowers, 56th, Silver Strand, Duranbah, hell even Smyrna or Ponce or some of the peaky spots in the Gulf, maybe continuous rocker is the go, because the lip line tapers nicely and there's a pocket peeling down it.
 
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PeterDj

Legend (inyourownmind)
Jul 11, 2018
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These days I'm all about the non-differentiable rocker curves
Actually, I think there is something to this. Most of the surfing/planing is done back at the tail and around center of mass of the person. The front quarter of the board is used during paddling and trying to drop into a wave. So why does it need to be continuous other than for esthetics? I'm thinking go high rocker in the nose with double concave to add lift and damping impact of chop, then a sharp kink to flat all the way out the back with slight rocker in the tail. I don't have the skill to craft a prototype of this, and the cfd software to simulate is super expensive. But, if you look at planing boat hull designs, this is pretty much what they do.
 
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rowjimmytour

Tom Curren status
Feb 7, 2009
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Actually, I think there is something to this. Most of the surfing/planing is done back at the tail and around center of mass of the person. The front quarter of the board is used during paddling and trying to drop into a wave. So why does it need to be continuous other than for esthetics? I'm thinking go high rocker in the nose with double concave to add lift and damping impact of chop, then a sharp kink to flat all the way out the back with slight rocker in the tail. I don't have the skill to craft a prototype of this, and the cfd software to simulate is super expensive. But, if you look at planing boat hull designs, this is pretty much what they do.
Check out Stretch and beak "buzz" nose models and rocker and more recent 5150 nose and rocker and bottom :shaka: :shaka: concave.


 

One-Off

Tom Curren status
Jul 28, 2005
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So much to unpack here.

First regarding apex=tangent. A tangent on a circle can be be anywhere on the circle. So I'll use Mr J's standard that apex refers to the center of the board. So what GiGi is referring to as apex is acceleration of rocker/angle of attack? (Mr. J is now my official GiGi translator).

And regarding the lift (planing) on the bottom (rocker) of a surfboard, it's the opposite of a foil's lift? It's pushing up against the convex surface instead of pulling on the convex surface? So it's really a totally different animal.

Stretches 5150 reverse channel...hmmmm... to me looks like water flowing over that will release, create turbulence and make the rail harder to engage. But I'll trust the anecdotal evidence of anyone who has ridden the board.

I wish someone would tape some of the red yarn they use on sails to the bottom of a board and then film under water. I remember someone on Swaylocks did it with a clear piece of plexiglass in a pool just to get an idea (Gdaddy?), and it was interesting. Most of the water went at an angle up (that becomes spray off the rail). But at the deepest part it was angled down. I think the yard would look like asymetric fishbones, if that makes any sense.

1622156613069.png
 
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PeterDj

Legend (inyourownmind)
Jul 11, 2018
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So much to unpack here.

First regarding apex=tangent. A tangent on a circle can be be anywhere on the circle. So I'll use Mr J's standard that apex refers to the center of the board. So what GiGi is referring to as apex is acceleration of rocker/angle of attack? (Mr. J is now my official GiGi translator).

And regarding the lift (planing) on the bottom (rocker) of a surfboard, it's the opposite of a foil's lift? It's pushing up against the convex surface instead of pulling on the convex surface? So it's really a totally different animal.

Stretches 5150 reverse channel...hmmmm... to me looks like water flowing over that will release, create turbulence and make the rail harder to engage. But I'll trust the anecdotal evidence of anyone who has ridden the board.

I wish someone would tape some of the red yarn they use on sails to the bottom of a board and then film under water. I remember someone on Swaylocks did it with a clear piece of plexiglass in a pool just to get an idea (Gdaddy?), and it was interesting. Most of the water went at an angle up (that becomes spray off the rail). But at the deepest part it was angled down. I think the yard would look like asymetric fishbones, if that makes any sense.

View attachment 111380
I think the reverse channels will add lift while in rail, but in the flats the tail will plane faster since there is little rocker. It does get bumpy in critical waves. Stretch showed me a clip of Eimeo in Teahupo testing the 5150 and it looked like a wild ride. It's designed for the high flyers where you do want lift in the tail rails to pop massive 8 foots airs like Nathan. I have a Tomo vanguard that has slight nose channels, and i think does add lift and help prevent pearling a little. But, if the board is designed to be 5'5" then I don't think preventing pearling is really a design priority, most of the design is to reduce drag and add maneuverability.
 
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sdsrfr

Phil Edwards status
Jul 13, 2020
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*Critters Toy Co (not Toy Critter)

I would suggest their Dickbender model.

It has plenty of rocker and a girthy foil yet slides in easy.
Nah. They’re in the hipster space.

who is ripping off t-low files and getting away with it by using some pop out alt tech. Think Hayden Shapes, but they’re already established.

Someone smaller and up and coming.
 

PeterDj

Legend (inyourownmind)
Jul 11, 2018
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I like this board Ryan Burch made for Dane with the nose channel. I don't care that the board itself is asymmetric, but adding some value to the nose design seems to be an area of neglect in boards. Too bad the video doesn't show Dane paddling into the wave. I hate the feeling of hitting brick wall when trying to paddle for the wave, like the nose it just in the way especially on choppy days. Seems like the nose channel doesn't hinder Danes massive turns either.