Author Topic: Rocker for narrow or wide race boards ?  (Read 2342 times)

willi

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Rocker for narrow or wide race boards ?
« on: February 28, 2018, 07:44:55 AM »
Hoping no questions are stupid --
I shaped a 24' x 12.6 and it is as quick as I thought it would be -- copied rocker (nose / tail) from several other race boards / I used a wide tail for stability
Wanting to build a wider board with round rails for the nasty Key West race this April and am not sure if the rocker should be more or less for a board say 29" wide with a wide tail &
flat bottom >>>  as I find hand shaping a concave challenging

any input would be appreciated

aloha

willi

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Re: Rocker for narrow or wide race boards ?
« Reply #1 on: February 28, 2018, 10:54:43 AM »
Stupid complicated. So many variables.
Just talking flatwater (no bumps) distance shape:

Length effects how well the board tracks and how it much it glides relative to weight. So a longer board will paddle a straighter line and typically glide better. Longer boards can have issues with side wind.

Width effects speed a stability. Narrower is faster and less stable.

Rocker effects speed and stability. Less rocker, more speed. We are just talking flatwater.

Rail shape effects speed and stability. Rounder rails create less drag, but reduce initial stability.

Board shape /outline effects speed, stability and glide. A sharp pointed nose to a sharp pointed tail is quiet, fast, and unstable.

Volume distribution effects everything. The force applied to the board from the paddle through your feet to the board will cause the board to bob, dive and turn. The extra volume in the nose offsets the force applied by you. There is and area forward of center referred to as "Recovery Volume". How much and where that goes depends on a lot of other variables.

Bottom shape effects stability, and tracking. Adding a concave or channel or groves I'm not convinced effect speed directly. Boards with more 'V' in the bottom tend to 'foot steer' more than flat bottom boards.   
 
The question is always how to balance these for your perfect Flatwater board.

You seem to have found a good balance of these with your current board.

Now add rougher 'open water' conditions. Lots of questions come into play regarding swell frequency, wind chop, refractory chop, typical wind direction for your area. Flatwater entry or through the surf entry and exit? For racing, are there a lot of buoy turns?

Sometimes I'm thankful for being out on a wider board with a little more rocker because of bad conditions. I'm able to maintain a cadence and a relatively good pace. Once I get to sheltered flatwater the lack of speed really is noticeable. There is no such thing as a great in all condition board.
It's not overhead to me!
8'8" L-41 ST and a whole pile of boards I rarely use.

FloridaWindSUP

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Re: Rocker for narrow or wide race boards ?
« Reply #2 on: February 28, 2018, 01:04:23 PM »
Willi, I'm looking forward to the Key West race, too. One thing that it has a lot of is poorly-lined up diagonal downwind. In those conditions (or any downwind conditions, really) boards with wide, square tails can misbehave and buck you off. So counterintuitively, for real rough water with upwind/downwind components, you might want to do a narrow pintail instead of a big squared-off tail. More width and volume further forward in the board can compensate for the loss of stability from the pintail. It's the Fanatic Falcon / Starboard Ace philosophy, where the nose to tail outline of the board is like a teardrop or the cross section of a fin. When going downwind the pintail kind of dips into an overtaking wave and gradually accelerates you to the speed of the wave without suddenly upsetting the board trim. The tail dipping-in effect also helps the nose of the board climb over chop going upwind. The combination of soft rails and narrow tail keep it settled when a wave hits it diagonally.

Everybody who tries my 14x27.25 Fanatic Falcon says it makes rough water / downwind conditions stupidly easy compared to any other allwater or downwind board that they've tried. I would strongly recommend copying the Falcon for your Key West board. Or if you want to do a dugout, copy the Ace, but I think flat deck is simpler.
14x23 Riviera RP
14x27.25 Fanatic Falcon
11'8 Exocet WindSUP
10'4 Angulo WindSUP
...and a bunch of windsurf stuff

burchas

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Re: Rocker for narrow or wide race boards ?
« Reply #3 on: February 28, 2018, 05:38:22 PM »
The way I went about it was designing the board around the pre-determined volume range.
For my last project I chose to subscribe to the very low volume type of boards.

Based on many boards I've tested, I found that the low volume boards offer amazing stability
and mostly unaffected by the elements (wind and chop) compared to high volume boards thus
allowing you to maintain narrow outline without sacrificing a lot of stability.

So my ocean board is 16'x25" @ 253 Litters (bottom surface is actually 22.5 inches at its widest point).
I chose to go with hybrid deck (see Mistral Equinox style). That put me almost at the waterline when
riding the board, achieving 2 key features, increased stability and extra leverage on the paddle as I
could shorten my paddle by about 2.5 inches which helps with performance even further.

Last piece of advice, pay extra attention to fin box placement which will be determined by tail rocker
width and volume. (consider adding the Larry Allison 4 fin setup for increased stability in rough conditions).

Good Luck!
in progress...

willi

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Re: Rocker for narrow or wide race boards ?
« Reply #4 on: March 30, 2018, 07:17:45 PM »
Guess I left things unfinished as I needed to do some more research on tail width and looking at Blackfish and Starboard see there is some tail width there represented as helping stability.
Finished Key West 3 times and feel a good stable board for that race & others would make the last leg more manageable.

I had shaped a 12.6 x 29 with a very wide tail ( Not shown) just to see how it would behave and feel in some junky waves. It wasn't as fast as my 25" wide tail but was very stable and after a 3 hour paddle my legs had some life left in them.

I took some pictures of my 25" x 12.6 - weighs about 22 pounds and was glassed with basalt & a layer of 6.6 ox s cloth. I think if the rails were a little rounder they would not get slapped around by little chop (the next one will have more volume and rounder bow.)
A little concave would I guess be better - not easy for me to hand shape - so I just left the bottom flat.

welcome comments so I can learn ']

aloha




« Last Edit: March 30, 2018, 07:19:20 PM by willi »

 


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