Author Topic: Need rocker curve for a 12'6  (Read 10670 times)

Henrik F

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Need rocker curve for a 12'6
« on: October 18, 2013, 03:49:37 PM »
Hi!
I need some advice on rocker curve for a 12'6 raceboard. It is mostly going to be used in flat to choppy conditions. No pintail, 12'6x26".

Thanks

Henrik F
crosswater.se

55NSup

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Re: Need rocker curve for a 12'6
« Reply #1 on: October 19, 2013, 05:14:40 AM »
Henrik,
Ive been reading everything I can about board design. Theres no definitive curve, there are too many variables. I suspect that many things work well and regular joes like us cant tell any differences.

I designed the 16-5 im building in Shape 3D and found that submerged volume and center of boyancy in relation to rocker curve was critical to get a clean waterline. What I mean is that the payload is equal to sumerged volume, and if you have too much or too little weight the waterline and submerged rocker vary a lot. For example, if you are heavier than calculated in design, the tail will be below WL. That will be really bad on square tail. So rider has to move forward over CB to lift tail. This in turn increases submerged volume forward and the engaged rocker. Lighter rider has to move back, lifting nose. Both situation can be bad for performance and is changing the WL.
Granted that this is very theoretical and assuming dead flat conditions.

Ive not read of any objective controlled experiments On same  boards with varied rider weights of 25-30 kgs.

Relatively Flat rocker with sharp entry, rounded rails all the way back. Id say a Bark competitor 26 wide, narrower tail, rounded rails all the way back, less tail rocker would be a good board. Bark has negative rocker along centerline in bow. My Bark plows and digs heading into chop, I suspect it could use a bit more nose volume.
Pin tail will be fastest.
I. Paddled my friends 2013 Fanatic 14 x 25 in total glassy. Right after paddeling 10 k on the 12-6 Bark. Like MTB compared to road bike. 

Henrik F

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Re: Need rocker curve for a 12'6
« Reply #2 on: October 19, 2013, 08:36:20 AM »
Henrik,
Ive been reading everything I can about board design. Theres no definitive curve, there are too many variables. I suspect that many things work well and regular joes like us cant tell any differences.

I designed the 16-5 im building in Shape 3D and found that submerged volume and center of boyancy in relation to rocker curve was critical to get a clean waterline. What I mean is that the payload is equal to sumerged volume, and if you have too much or too little weight the waterline and submerged rocker vary a lot. For example, if you are heavier than calculated in design, the tail will be below WL. That will be really bad on square tail. So rider has to move forward over CB to lift tail. This in turn increases submerged volume forward and the engaged rocker. Lighter rider has to move back, lifting nose. Both situation can be bad for performance and is changing the WL.
Granted that this is very theoretical and assuming dead flat conditions.

Ive not read of any objective controlled experiments On same  boards with varied rider weights of 25-30 kgs.

Relatively Flat rocker with sharp entry, rounded rails all the way back. Id say a Bark competitor 26 wide, narrower tail, rounded rails all the way back, less tail rocker would be a good board. Bark has negative rocker along centerline in bow. My Bark plows and digs heading into chop, I suspect it could use a bit more nose volume.
Pin tail will be fastest.
I. Paddled my friends 2013 Fanatic 14 x 25 in total glassy. Right after paddeling 10 k on the 12-6 Bark. Like MTB compared to road bike. 
Thanks 55NSup
It's a lot to think about there. Could you explain more around the round rails compared to sharp ones? Even though it doesn't concern the rocker question :)

Henrik F
crosswater.se

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Re: Need rocker curve for a 12'6
« Reply #3 on: October 19, 2013, 07:30:27 PM »
When you really understand surfboards or standup boards you'll understand that the design can't be compartmentalized into one design element or another. The rocker, foil, outline rails, etc are things that are learned with experience. The way only a very seasoned shaper can determine. They can just LOOK at a board and determine the value of the shape.

 One rocker profile will be completely wrong with an outline or foil that was not designed to be compatible with it.
Boards:

 
8-10 x 31 Egg
8-11 X 32 Double wing Fangtail Tom Whitaker
8-6 X 30 1\2  Inbetweener Tom Whitaker
8-4 x 30 Hyper quad Tom Whitaker (wife's now)
8-4 X 31 1\4.  Round (wide) Diamond Tail Quad Tom Whitaker
 9-4 X 30 1\2. Swallow Stinger Quad Tom Whitaker (ex wifes now)
10-0 Brusurf for teach

55NSup

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Re: Need rocker curve for a 12'6
« Reply #4 on: October 20, 2013, 12:49:43 PM »
Im an amateur. Yes, so many interdependent variables.
I studied yacht design 30 years ago by working through a mail order course a former boss and boat builder / racer loaned to me. Lots of manual drawing and calculation of prismatic coefficients. Figuring out CB and Center of resistence.
When I started designing a board in Shape 3D the knowledge came back and by playing around with the variables and you get an idea of the cause and effect.
The problem is - all of its theoretical. I have no idea what the real life effect is on the board in real conditions.
All I Could do was Design a board with good prismatic coefficients, correct Center of boyancy and displacement for my weight. The plan form, sections and waterline slices looked fair. Thats where I ended up.

Then I made plan and profile templates for hot wire. Rest is shaped by hand and only looking at 3D on computer for visual reference. I deviated from the design based uopon what my eyes told me. I could not follow 3D accurately any way. It will really interesting to see how it paddles.

55NSup

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Re: Need rocker curve for a 12'6
« Reply #5 on: October 20, 2013, 01:00:46 PM »
Here it is more complete.

Pierre

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Re: Need rocker curve for a 12'6
« Reply #6 on: October 23, 2013, 01:47:53 PM »
55N is not wrong, but there must be a relation between rocker,immersed volume,width and shape ofboard andpaddler level,,, furthermore if stem is immersed like barks noserocker is less...
I drawn a table in a post about one design board... http://www.standupzone.com/forum/index.php?topic=17446.15
more or less for an average standard race board 12,6

 WIDTH AND DEPTH OF RACE BOARD LENGTH 12'6" FOR SAME CHARACTERISTICS ACCORDING TO SIZE AND WEIGHT                             
L   1 inch = 2.54 cm            SKILL FACTOR ABOUT 2                 
   Masse  Kg       50   60   70   80   90   100   110   120   
   SIZE m                             
   1.50   breadth=   58.3   61.3   64.0   66.5   68.9   71.0   73.1   75.0   
      depth=   4.7   5.4   6.0   6.6   7.2   7.7   8.3   8.8   
   1.60   breadth=   59.5   62.6   65.3   67.9   70.3   72.5   74.6   76.6   
      depth=   4.6   5.3   5.9   6.5   7.0   7.6   8.1   8.6   
   1.70   breadth=   60.7   63.8   66.6   69.2   71.6   73.9   76.1   78.1   
      depth=   4.5   5.2   5.8   6.3   6.9   7.4   7.9   8.4   
   1.80   breadth=   61.8   65.0   67.8   70.5   73.0   75.3   77.5   79.5   
      depth=   4.4   5.1   5.7   6.2   6.8   7.3   7.8   8.3   
   1.90   breadth=   62.9   66.1   69.0   71.7   74.2   76.6   78.8   80.9   
      depth=   4.4   5.0   5.6   6.1   6.7   7.2   7.7   8.1   
   2.00   breadth=   63.9   67.2   70.2   72.9   75.5   77.9   80.1   82.2   
      depth=   4.3   4.9   5.5   6.0   6.5   7.0   7.5   8.0   
   2.10   breadth=   64.9   68.3   71.3   74.1   76.7   79.1   81.4   83.5   
      depth=   4.2   4.8   5.4   5.9   6.4   6.9   7.4   7.9   
                                 
   US measures                             
   WIDTH AND DEPTH OF RACE BOARD LENGTH 12'6" FOR SAME CHARACTERISTICS ACCORDING TO SIZE AND WEIGHT                             
   1 inch = 2.54 cm      2.2 Lbs=   1 kg                     
   Mass  Lbs --->      110   132   154   176   198   220   243   265   
size ft   in                             
4   11   breadth=   23.0   24.1   25.2   26.2   27.1   28.0   28.8   29.5   
      depth=   1.9   2.1   2.4   2.6   2.8   3.0   3.3   3.5   
5   3   breadth=   23.4   24.6   25.7   26.7   27.7   28.5   29.4   30.2   
      depth=   1.8   2.1   2.3   2.5   2.8   3.0   3.2   3.4   
5   7   breadth=   23.9   25.1   26.2   27.3   28.2   29.1   29.9   30.7   
      depth=   1.8   2.0   2.3   2.5   2.7   2.9   3.1   3.3   
5   11   breadth=   24.3   25.6   26.7   27.8   28.7   29.6   30.5   31.3   
      depth=   1.7   2.0   2.2   2.5   2.7   2.9   3.1   3.3   
6   3   breadth=   24.8   26.0   27.2   28.2   29.2   30.2   31.0   31.8   
      depth=   1.7   2.0   2.2   2.4   2.6   2.8   3.0   3.2   
6   7   breadth=   25.2   26.5   27.6   28.7   29.7   30.7   31.5   32.4   
      depth=   1.7   1.9   2.2   2.4   2.6   2.8   3.0   3.2   
6   11   breadth=   25.6   26.9   28.1   29.2   30.2   31.1   32.0   32.9   
      depth=   1.7   1.9   2.1   2.3   2.5   2.7   2.9   3.1   
in this table depth is immersed depth of board... this is not rocker, rocker is a curve conventionally measured from board center but with differents radiusesofcurvature..., deepest point may not be at center, stem may be immersed or not... thes are the arcans of naval architecture.I did some explains in topic : http://www.up-shack.com/assets/up/addce43fe2ea6433f9ddfb0b8b1ffa4c.pdf but sorry if you need a translator ( pages 4-7)
good luck.
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Henrik F

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Re: Need rocker curve for a 12'6
« Reply #7 on: October 23, 2013, 09:11:56 PM »
55N is not wrong, but there must be a relation between rocker,immersed volume,width and shape ofboard andpaddler level,,, furthermore if stem is immersed like barks noserocker is less...
I drawn a table in a post about one design board... http://www.standupzone.com/forum/index.php?topic=17446.15
more or less for an average standard race board 12,6

 WIDTH AND DEPTH OF RACE BOARD LENGTH 12'6" FOR SAME CHARACTERISTICS ACCORDING TO SIZE AND WEIGHT                             
L   1 inch = 2.54 cm            SKILL FACTOR ABOUT 2                 
   Masse  Kg       50   60   70   80   90   100   110   120   
   SIZE m                             
   1.50   breadth=   58.3   61.3   64.0   66.5   68.9   71.0   73.1   75.0   
      depth=   4.7   5.4   6.0   6.6   7.2   7.7   8.3   8.8   
   1.60   breadth=   59.5   62.6   65.3   67.9   70.3   72.5   74.6   76.6   
      depth=   4.6   5.3   5.9   6.5   7.0   7.6   8.1   8.6   
   1.70   breadth=   60.7   63.8   66.6   69.2   71.6   73.9   76.1   78.1   
      depth=   4.5   5.2   5.8   6.3   6.9   7.4   7.9   8.4   
   1.80   breadth=   61.8   65.0   67.8   70.5   73.0   75.3   77.5   79.5   
      depth=   4.4   5.1   5.7   6.2   6.8   7.3   7.8   8.3   
   1.90   breadth=   62.9   66.1   69.0   71.7   74.2   76.6   78.8   80.9   
      depth=   4.4   5.0   5.6   6.1   6.7   7.2   7.7   8.1   
   2.00   breadth=   63.9   67.2   70.2   72.9   75.5   77.9   80.1   82.2   
      depth=   4.3   4.9   5.5   6.0   6.5   7.0   7.5   8.0   
   2.10   breadth=   64.9   68.3   71.3   74.1   76.7   79.1   81.4   83.5   
      depth=   4.2   4.8   5.4   5.9   6.4   6.9   7.4   7.9   
                                 
   US measures                             
   WIDTH AND DEPTH OF RACE BOARD LENGTH 12'6" FOR SAME CHARACTERISTICS ACCORDING TO SIZE AND WEIGHT                             
   1 inch = 2.54 cm      2.2 Lbs=   1 kg                     
   Mass  Lbs --->      110   132   154   176   198   220   243   265   
size ft   in                             
4   11   breadth=   23.0   24.1   25.2   26.2   27.1   28.0   28.8   29.5   
      depth=   1.9   2.1   2.4   2.6   2.8   3.0   3.3   3.5   
5   3   breadth=   23.4   24.6   25.7   26.7   27.7   28.5   29.4   30.2   
      depth=   1.8   2.1   2.3   2.5   2.8   3.0   3.2   3.4   
5   7   breadth=   23.9   25.1   26.2   27.3   28.2   29.1   29.9   30.7   
      depth=   1.8   2.0   2.3   2.5   2.7   2.9   3.1   3.3   
5   11   breadth=   24.3   25.6   26.7   27.8   28.7   29.6   30.5   31.3   
      depth=   1.7   2.0   2.2   2.5   2.7   2.9   3.1   3.3   
6   3   breadth=   24.8   26.0   27.2   28.2   29.2   30.2   31.0   31.8   
      depth=   1.7   2.0   2.2   2.4   2.6   2.8   3.0   3.2   
6   7   breadth=   25.2   26.5   27.6   28.7   29.7   30.7   31.5   32.4   
      depth=   1.7   1.9   2.2   2.4   2.6   2.8   3.0   3.2   
6   11   breadth=   25.6   26.9   28.1   29.2   30.2   31.1   32.0   32.9   
      depth=   1.7   1.9   2.1   2.3   2.5   2.7   2.9   3.1   
in this table depth is immersed depth of board... this is not rocker, rocker is a curve conventionally measured from board center but with differents radiusesofcurvature..., deepest point may not be at center, stem may be immersed or not... thes are the arcans of naval architecture.I did some explains in topic : http://www.up-shack.com/assets/up/addce43fe2ea6433f9ddfb0b8b1ffa4c.pdf but sorry if you need a translator ( pages 4-7)
good luck.

Thank you so much! Your link is brilliant and yes, I need a translator for most of it but the pictures and tables gave a lot of information too.

Henrik F
crosswater.se

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Re: Need rocker curve for a 12'6
« Reply #8 on: October 25, 2013, 05:37:45 PM »
Experience is the key to much of shaping, IMHO....this comment coming from a very inexperienced shaper (me :-))  But what has worked for me is taking my best shot at a shape, then critiquing the results by paddling the shape and trying again.  The second 12-6 I did was ALOT better than the first...but I'm an "eyeball" shaper with no experience with the numbers and  I've always been a learning by doing type person...and have made a fair number of mistakes in the process....but I've had a heck of a lot of fun!

Henrik F

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Re: Need rocker curve for a 12'6
« Reply #9 on: October 25, 2013, 09:07:05 PM »
Experience is the key to much of shaping, IMHO....this comment coming from a very inexperienced shaper (me :-))  But what has worked for me is taking my best shot at a shape, then critiquing the results by paddling the shape and trying again.  The second 12-6 I did was ALOT better than the first...but I'm an "eyeball" shaper with no experience with the numbers and  I've always been a learning by doing type person...and have made a fair number of mistakes in the process....but I've had a heck of a lot of fun!

Beautiful boards you've got there!

Henrik F
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Re: Need rocker curve for a 12'6
« Reply #10 on: October 25, 2013, 09:39:53 PM »
Thanks.  The one on the left is the newest shape.  It's roughly 12 kg done as a hollow wood.  4mm ply frame and a +- 4mm paulownia skin.

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Re: Need rocker curve for a 12'6
« Reply #11 on: November 24, 2013, 10:23:53 PM »
The rocker varies on weight and width. The Naish LE at 23" wide has and needs a ton of rocker to have the tail release for 175 lbs. For 12'6"X26 and a rider at 120 lbs  the rocker is around 2 1/2 inches nose and tail. Add width, subtract rocker.
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Henrik F

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Re: Need rocker curve for a 12'6
« Reply #12 on: November 25, 2013, 10:27:08 AM »
The rocker varies on weight and width. The Naish LE at 23" wide has and needs a ton of rocker to have the tail release for 175 lbs. For 12'6"X26 and a rider at 120 lbs  the rocker is around 2 1/2 inches nose and tail. Add width, subtract rocker.

Thanks!

Henrik F
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Re: Need rocker curve for a 12'6
« Reply #13 on: November 25, 2013, 10:34:17 AM »
Thanks, Bob.  I'd never thought of the trade offs quite like that.  Very useful take.

 


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