Author Topic: Optimal width of a downwind board  (Read 15360 times)

yugi

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Optimal width of a downwind board
« on: May 28, 2015, 11:32:15 AM »
For windsurf boards, kite boards, wakeboard, boats, even skis too, we all know a wider surface picks up onto a plane quicker. All have evolved to shorter and wider. Downside, like surfboards, being they bounce around more at speed. A gun shape cuts through rough better.

Yet the crop of 27” wide downwind 14’er are faster than the 28” or 30” wide ones. 26” faster too and racers are on 24” or even less. Could be the shape of course.

Obviously a narrower board is more optimal for paddling with a shaft held vertically (looking from front or back). There’s that.

I’ve always been interested in where the optimal blend of this tradeoff lies. In another thread it was suggested the new Bark downwind board was tested in narrower than 28” but wasn’t faster. Anyone have access to any real data on this? I’m sure there are plenty of opinions. Optimal width would be depend on rider height and weight of course.

Personally I like the new boards coming out with bottom optimized for planing and stability so one can take them  narrower overall. I'm also a fan of hard rails right to the tip. At least love the ones I've ridden with these.
« Last Edit: May 28, 2015, 11:36:55 AM by yugi »

yugi

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Re: Optimal width of a downwind board
« Reply #1 on: May 28, 2015, 11:37:31 AM »
I'm guessing the sheer size of SUP boards plays a factor. Less surface equals less drag.

supuk

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Re: Optimal width of a downwind board
« Reply #2 on: May 28, 2015, 10:30:47 PM »
What I have found is that by going narrow the board stays glideing a lot longer and faster so connecting bumps easier. We were dw on 24" (actually measures 24")all last year and going back onto a 26" felt so stable.

PonoBill

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Re: Optimal width of a downwind board
« Reply #3 on: May 28, 2015, 11:17:11 PM »
The fast paddlers with low weight, high power to weight ratio, and lots of talent will probably go even narrower. At some point they'll go backwards with this, but that's probably below 20 inches. If nothing else you move the hull speed limit up. A 210 inch board (17'6") that's 20 inches wide is at the "magic" ten to one limit where the bow wave generated is so weak that the hull rides over it relatively easily. Skin friction is high, and it takes a powerful, high cadence paddler to keep the hull moving beyond the hull speed limit. Paddlers on super narrow boards need to decrease friction every way possible, like Jeremy Riggs, cutting his rudder down to a stub, but they will actually see a difference from these changes because they aren't bumping into a hull speed limit that overwhelms skin friction. Some new rudder shapes and probably new hull contours will push this forward. A board like this should be possible to paddle at 8-9 mph and hold 14-15mph in glides.

I have the math for this someplace--might actually be here on the zone somewhere. I did a bunch of work on it when I was playing with the Penetrator in 2009  http://www.standuppaddlesurf.net/2009/07/09/penetrator-run-with-pono-bill/  The penetrator was 572cm (225 inches) and 22 inches at the waterline with my weight on it. Took a lot of power to make it go, but it felt linear. With Jeremy on it, it was a rocket.
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DavidJohn

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Re: Optimal width of a downwind board
« Reply #4 on: May 29, 2015, 12:42:53 AM »
I'm guessing the sheer size of SUP boards plays a factor. Less surface equals less drag.

Yes but too much less = more drag..  :)

headmount

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Re: Optimal width of a downwind board
« Reply #5 on: May 29, 2015, 02:39:32 AM »
I think there's more than top end speed that goes into the calculation of what works best for downwind.  There's a lot of time when were sticking our paddles in to brake so we don't go too fast and out ride the trough.  Handling has to be a huge factor. 

Downwind is rather vague term that only entails wind direction but wind speed, currents, and crossing swells or lack of, determine much of the detail of a run.  Details that have different demands on a board.  A light V2 17' Bullet is wider (28") than the current norm but with a variety of conditions this would be the optimal width IMO.  Sure, other boards might go faster in ultimate conditions but even here on Maui, considered one of the premier DW spots in the world, there are many days when there are as many as three or four different zones, each offering their unique challenges.  You can go from hero to zero real quick.

I have a V1 (17) which is about 1.5 inches narrower than V2 and I've come to like it because it's been my horse for more than a few years. But recently I've done some runs on a light V2 (17) that a friend of mine bought from Conner.  I like the lower nose rocker and the comfort on this board.  Comfort means you can really go after every glide, contrasting with my V1 where I sometimes feel I must wait till everything is set up just right to dig hard.  The new V3 17 seems even more fickle to me  with that set up.  But if you're a powerful paddler (I'm not) then those issues become less.  So I would guess that optimal width has a lot to do with the paddler's abilities.  Kalama and Jeremy are pushing widths that makes many uncomfortable but they're definitely A-team..  Remember when you're going ten to 30 miles, fatigue happens.  Livio who is also A-team, loves the V2 at 28"  Here he is (on a 28") toe to toe with Danny Ching.  Who looks more comfortable on take off?
« Last Edit: May 29, 2015, 02:44:17 AM by headmount »

PonoBill

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Re: Optimal width of a downwind board
« Reply #6 on: May 29, 2015, 07:31:04 AM »
I would probably agree if my V2 were anywhere near light.
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headmount

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Re: Optimal width of a downwind board
« Reply #7 on: May 29, 2015, 09:27:37 AM »
Oh and Danny is on a V1

PonoBill

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Re: Optimal width of a downwind board
« Reply #8 on: May 29, 2015, 09:54:37 AM »
Yeah, I kind of forgot to include the notion "optimal for whom?".  My 30" 11'11" SIC is optimal for fun in the gorge. What a great board. You have to work to fall off it. I do, but it's mostly because I'm trying nutty stuff. Not a lot of glide, but so much fun that who cares. As long as there isn't a crowd waiting for me to get to the end for the ride back to Viento it's great. The perf4ect shuttle board.

Now all we need is some wind. After 7 striaght days of epic downwind the river is a lake and it's 80 degrees. Nice for paddling OC6, and I need to get my race car going anyway.
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photofr

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Re: Optimal width of a downwind board
« Reply #9 on: May 29, 2015, 10:10:47 PM »
My take on it is a simpler one:
You can go narrow (24" for your DW board) and this is great fun when everything is aligned perfectly, and the DW run is relatively short (7 miles or less). In this case, narrow is super fun, if you can handle the stability or lack thereof. The speed increase of a 24" board is noticeable on DW.

You can go wider (like 27") and immediately find the board a little more sluggish, but after 2 hours, you don't have to worry about stability as much and you just don't get as tired. When the conditions aren't aligned perfectly, the slower and wider board on flat water will actually be much faster on your rough DW.

The most important aspect of speed vs. width is, to me:
Narrower boards will tend to give you an increase in speed.
Technique, Endurance and muscle mass will give your 3 folds in speed increase - and add a little more safety / margins or error.
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Off-Shore

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Re: Optimal width of a downwind board
« Reply #10 on: May 30, 2015, 02:19:46 AM »
My take on it is a simpler one:
You can go narrow (24" for your DW board) and this is great fun when everything is aligned perfectly, and the DW run is relatively short (7 miles or less). In this case, narrow is super fun, if you can handle the stability or lack thereof. The speed increase of a 24" board is noticeable on DW.

You can go wider (like 27") and immediately find the board a little more sluggish, but after 2 hours, you don't have to worry about stability as much and you just don't get as tired. When the conditions aren't aligned perfectly, the slower and wider board on flat water will actually be much faster on your rough DW.

The most important aspect of speed vs. width is, to me:
Narrower boards will tend to give you an increase in speed.
Technique, Endurance and muscle mass will give your 3 folds in speed increase - and add a little more safety / margins or error.

I agree with you completely. In a groomed run where everything is lined up you can go narrower. But add time and you will tire quicker than a wider board. Certainly board shape is a factor but for me the SIC bullet 14v1 or v2 at 27.25" wide is optimal for all conditions. I've tried the SIC F14 at 30" and it feels real sluggish. I've also tried downwinding a Starboard Race 14' at 25" wide and it was fast and fun but I fell when being hit from the side by ocean swell. At 5'11" (180cm) and 180lbs /82kgs, I think 27.25" to 28" feels perfect.

Fast forward to 2.00 to the start of the downwind run on this 25" wide race board and watch how much the board wobbles around (and the ocean swell that comes in from the left results in two falls)
http://youtu.be/ShlhgYWfSME
« Last Edit: May 30, 2015, 02:34:37 AM by Off-Shore »
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UKRiverSurfers

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Re: Optimal width of a downwind board
« Reply #11 on: May 30, 2015, 03:37:36 AM »
Its worth noting that a board riding a bump is not truly 'on the plane' :)

To be truly planing it needs to be overtaking its wake.
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DavidJohn

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Re: Optimal width of a downwind board
« Reply #12 on: May 30, 2015, 04:48:07 AM »
Its worth noting that a board riding a bump is not truly 'on the plane' :)

To be truly planing it needs to be overtaking its wake.

I'm not sure.. Yes you can ride a bump and not be planing.. but you can also be fully planing on some bumps IMO..  :)


UKRiverSurfers

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Re: Optimal width of a downwind board
« Reply #13 on: May 30, 2015, 05:11:49 AM »
That just depends on where the wake is DJ..

Of course, as with everything there is always the exception to the rule ;)
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Area 10

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Re: Optimal width of a downwind board
« Reply #14 on: May 30, 2015, 06:58:00 AM »
Its worth noting that a board riding a bump is not truly 'on the plane' :)

To be truly planing it needs to be overtaking its wake.

I'm not sure.. Yes you can ride a bump and not be planing.. but you can also be fully planing on some bumps IMO..  :)
Well, certainly you can do what I call "surge-riding", which happens quite a lot with raceboards that don't plane easily - you are definitely getting a push but you are sitting high on the bump and going at the same pace as it. But what I think of as downwinding is an experience that is pretty much indistinguishable from surfing: the board is moving far faster than the bump and this allows you to plow over the bump in front and into the next trough, and so on. The board feels loose and free, and is throwing up spray at the sides and you need your foot over the fin to move it around to avoid poking the nose into the bump in front. So I don't know if that is what you'd call planing, but that is what I'm aiming for in my downwinding. You can connect bumps by turning and following the direction of the troughs, or you can do it by getting so much momentum up that you are skipping over them, and that's when the real excitement happens, to my mind.

 


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