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 Post subject: Re: Float - Length vs width vs rocker vs camber...
PostPosted: Mon Oct 31, 2011 12:12 pm 
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Joined: Fri Jul 09, 2010 10:44 am
Posts: 46
The engineer in me loves this, haha. :thumpsup:

YEGsplit wrote:
Did somebody say math?

What we're talking about essentially is the coefficient of lift. From my perspective, a snowboard sliding down a hill is a lot a wing flying through the air, or a surfboard planing in the water. Obviously, there are differences but I think as a first approximation is a good starting point for discussing the variables touched on here: lift (L), velocity (v), area (A).

L = p/2*v^2*A*C

So basically, lift varies with the square of the velocity, and linearly with the area (therefore length) of the board.

In the above, C is the coefficient dependent on the angle of attack of the wing and some other physical constants, and p is the density of the medium the wing is flying through.

What I would derive from this is that area (and therefore length) is important, but not as important as speed. I'm going to get a lot more lift out of riding 5% faster than I am from riding a 5% longer board. If I'm more comfortable riding a long board, then that's the best of both worlds - I'll get tons of lift. If I'm not comfortable with a longer board (shame on me, I know), then I'm better off riding a shorter board faster.

As always, for more info the wikipedia is awesome:

http://en.wikipedia.org/wiki/Lift_%28force%29

http://en.wikipedia.org/wiki/Lift_coefficient

Now, this is a first approximation, there are probably a whole ton of very subtle fluid dynamic arguments regarding angle of attack, turbulence, drag, blah blah blah. But I would say this is a very good guide for this argument.


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 Post subject: Re: Float - Length vs width vs rocker vs camber...
PostPosted: Mon Oct 31, 2011 1:03 pm 
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Joined: Wed Jul 07, 2010 7:44 pm
Posts: 417
Location: Cupertino, CA
This is an interesting topic. You simply cannot debate physics for planing characteristics, edge hold, swing weights, etc. but I think a lot of the discussion can be focused around location and type/depth/slope angle of snow typically being ridden as decision making variables in what length of board to choose, regardless of style of riding. However, the rocker profiles have added a level of complexity to the decision making process and have influenced my choices.

When I was growing up on the east coast, I rode boards in the 143cm (jib phase) to 154cm range. For 99% of the time this was sufficient. On the east coast, you're typically riding shallower snow pack, lower slope angles on average (in general, there are plenty of exceptions), tighter trees (necessitating tighter turning boards) and powder days are majority 1' or less. Even a very wide 143 “lunch tray” had enough float for me on a 1 foot day riding way in the backseat and burning my back leg like an egg in a frying pan.

When I moved west to Tahoe 15 years ago, it quickly became apparent how limiting the lunch tray was on steeps, deep powder >2 feet days somewhat common, more open trees where you can increase speed, let alone anything in the alpine where you can really hit the throttle. My “long board” of 154cm quickly became my “short board” and my long board grew to 166cm at its largest (for reference, I am 5'6" (167cm)). I learned to spin and hit larger features on the 154cm and my short board size slowly crept up through the years to what I considered an optimal 157-158cm. A 156cm was great for more freestyle oriented riding, but gave up a little on the freeride side of things. At the same time a 159cm was incredible for freeriding but gave up too much in swing weight for my preferred freestyle riding. So it seems Iike I bounce between the 157-58 size with no detriment to my riding style – albeit a lot less spinning @ almost 40, but I can still bust a 3 or muster up a 5 or maybe even a 7 when I’ve got my groove on. Consequentially, my powder boards have been mostly in the 164 range, but narrower for my size 8 feet – very big for a guy my size. Planing was always great and I never had a problem in tight trees.

With the advent of rocker profiles and different shapes, I’ve found my powder boards are now migrating down in size to be only a few cm’s larger than my freeriding boards. My split is a 162cm and I probably could go 1-2cm shorter next time. My powder board this year will be a 160cm, while my freeriding board is a 158cm – pretty damn close, although the shapes, flex, width (wider on the pow board), rocker (all are cam-nose rock) and sidecut length (longer) are all different that what I historically rode.

I still ride the east every year, but it will be a shorter-radius 157 DIY that will be used exclusively there to do it all, as its characteristics lend itself to the range of conditions and types of riding I will encounter there.

Interestingly, my wife has already achieved parity among her boards. Perhaps the differences are smaller as you decrease in size as well, with shape, rocker and flex accounting for all the differences.


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 Post subject: Re: Float - Length vs width vs rocker vs camber...
PostPosted: Mon Oct 31, 2011 1:09 pm 
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Joined: Wed Jul 07, 2010 7:44 pm
Posts: 417
Location: Cupertino, CA
YEGsplit wrote:
Did somebody say math?

What we're talking about essentially is the coefficient of lift. From my perspective, a snowboard sliding down a hill is a lot a wing flying through the air, or a surfboard planing in the water. Obviously, there are differences but I think as a first approximation is a good starting point for discussing the variables touched on here: lift (L), velocity (v), area (A).

L = p/2*v^2*A*C

So basically, lift varies with the square of the velocity, and linearly with the area (therefore length) of the board.

In the above, C is the coefficient dependent on the angle of attack of the wing and some other physical constants, and p is the density of the medium the wing is flying through.

What I would derive from this is that area (and therefore length) is important, but not as important as speed. I'm going to get a lot more lift out of riding 5% faster than I am from riding a 5% longer board. If I'm more comfortable riding a long board, then that's the best of both worlds - I'll get tons of lift. If I'm not comfortable with a longer board (shame on me, I know), then I'm better off riding a shorter board faster.

As always, for more info the wikipedia is awesome:

http://en.wikipedia.org/wiki/Lift_%28force%29

http://en.wikipedia.org/wiki/Lift_coefficient

Now, this is a first approximation, there are probably a whole ton of very subtle fluid dynamic arguments regarding angle of attack, turbulence, drag, blah blah blah. But I would say this is a very good guide for this argument.


:thumpsup: and your theoretical speed limit is defined by the terrain you ride and the relative density of the snow. The steeper the slope, the speed limit goes down proportionally as well, also necessitating increased edge length/hold in addition to lift/float.

Don't forget also that shapes like a Hovercraft, Fish, etc. all increase area without length by increasing relative width.


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 Post subject: Re: Float - Length vs width vs rocker vs camber...
PostPosted: Mon Oct 31, 2011 3:44 pm 
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Joined: Thu Nov 20, 2008 9:10 pm
Posts: 1411
Location: UT
I ride a 195 because its fast and its fun! Most of my riding is in trees and it doesn't bother me in the least... The 195 does make for a long day if the skin track has lots of kick turns... My resort board is a 180 and both are swallowtails... I prefer the ride of swallowtails in all conditions (ice is not a condition, ice is suck)... I will be trying out a 163 Arbor converted to a swallowtail this season simply for the ease on the skin track...

Question:
Can anyone explain why the majority of skiers aren't rocking shorter boards? (I'm not trying to perpetuate an argument, I've just always wondered why)

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Experts tell me I'm not a serious rider; riding boards that are too long with the incorrect boot and binding setup and I'm not having fun...


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 Post subject: Re: Float - Length vs width vs rocker vs camber...
PostPosted: Mon Oct 31, 2011 4:05 pm 
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Joined: Mon Sep 19, 2011 6:37 pm
Posts: 167
Location: Calgary
Snurfer wrote:
Question:
Can anyone explain why the majority of skiers aren't rocking shorter boards? (I'm not trying to perpetuate an argument, I've just always wondered why)


www.skis.com wrote:
With the advent of shaped skis, the typical length of skis has changed. Years ago, skis for men stretched from 175cm to 205cm and beyond. But now close to 80 percent of men’s skis fall in the 155–175cm range


As for snowboards, last season i tried out a 174 camber splitboard, for me it was brutal to ride, I much prefer a shorter 158 reverse camber board in powder @ 6'0 190lbs, but maybe I like to ride a little faster

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 Post subject: Re: Float - Length vs width vs rocker vs camber...
PostPosted: Mon Oct 31, 2011 6:18 pm 
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Joined: Thu Nov 19, 2009 9:16 am
Posts: 496
Location: Salida, Flagstaff
Oh wow, this is still going on?

I'm getting a 210, mostly for back-country spins.

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Craig Kelly is my co-pilot
195 Glissade Big Gun
187 Donek Custom Split
181 Venture Storm Solid and Split
173 Rossi Race DIY Swallowtail Split


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 Post subject: Re: Float - Length vs width vs rocker vs camber...
PostPosted: Mon Oct 31, 2011 7:16 pm 
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Joined: Sat Apr 04, 2009 10:32 am
Posts: 556
Location: Rawesome, BC
This thread comes to mind....



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 Post subject: Re: Float - Length vs width vs rocker vs camber...
PostPosted: Mon Oct 31, 2011 7:41 pm 
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Joined: Mon Sep 19, 2011 6:37 pm
Posts: 167
Location: Calgary
@ 3:40...forget Travis Rice...Danny Strasser!! :bow:

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 Post subject: Re: Float - Length vs width vs rocker vs camber...
PostPosted: Tue Nov 01, 2011 3:50 am 
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Joined: Sun May 08, 2011 9:57 pm
Posts: 62
Location: Christchurch, New Zealand
Even Shawn Farmer rocks the long boards so they got to be good. :wink:
He even uses riser pads under the bindings..

Check out his quiver.

http://www.youtube.com/watch?feature=pl ... MYnoe9sqCo

Farm F*@#kn Fresh man!


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 Post subject: Re: Float - Length vs width vs rocker vs camber...
PostPosted: Tue Nov 01, 2011 7:04 am 
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Joined: Wed Mar 23, 2005 8:51 am
Posts: 636
So I'm no expert surfer, but why is it that all of the pro surfers ride short boards? Even on big waves, they went shorter once they started towing in. Seems like they figured something out, like the fact that float is not the sole determination of ride quality.


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 Post subject: Re: Float - Length vs width vs rocker vs camber...
PostPosted: Tue Nov 01, 2011 8:21 am 
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Location: Salida, Flagstaff
Here's a cool video clip about AK Bommers - big ol' AK-grown long boards (some with 16" wide shovels!!): http://vimeo.com/4383866

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Craig Kelly is my co-pilot
195 Glissade Big Gun
187 Donek Custom Split
181 Venture Storm Solid and Split
173 Rossi Race DIY Swallowtail Split


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 Post subject: Re: Float - Length vs width vs rocker vs camber...
PostPosted: Tue Nov 01, 2011 8:30 am 
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Joined: Fri Jan 15, 2010 2:01 pm
Posts: 796
Location: Colorado
shredgnar wrote:
why is it that all of the pro surfers ride short boards? Even on big waves, they went shorter once they started towing in.
The longer surfboards were to assist in "dropping in" on big outer breaks, as well as stability at high speeds. With the advent of "tow-in" they no longer had to "drop-in". Shapers then could work on making a smaller, faster, stable board that was specifically designed for "tow-in".

What this has to do with splitboarding, I don't know :scratch:

Keep in mind that:

Speed = Float and More Speed = More Float

Its a core Bruce Lee principle: "Speed = Power" :ninja:

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 Post subject: Re: Float - Length vs width vs rocker vs camber...
PostPosted: Tue Nov 01, 2011 9:32 am 
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Joined: Wed Nov 30, 2005 3:32 pm
Posts: 358
re surfboard lengths going down, pro surfboards have been going down in length for two main reasons: 1 easier to control and faster to spin in the air, easier to spin after landing a reverse air etc. both of which have become staple moves on the tour and 2, you can carve a tighter turn arc with a shorter board so you can fit more dramatic looking turns into smaller waves, or you can through tighter turns on a smaller piece of water when there are warbles or bumps in the face of the wave.

What is so different about shorter surfboards in the last 4-8 years is that boards have actual buoyancy, meaning part of their lift is from the thickness of the board and the thickness of the rail and surfboard fish-inspired boards are actually wider like 19-20 inches than the old standard 6 foot board which was usually 18 and change for the average 150-165 pound person.

So-called fish snowboards were never made wider, just shorter and marketed themselves on the success and popularity of the resurgence of fish style-inspired surfboards.

The only real examples of a parallel in the snowboard world for fish style shorter surfboards would maybe be the lib tech banana hammock at 31 cm in the middle and definitely the board that Huck Pituee just showed us in his TR. Maybe if you weigh 150 and used to ride a 24.5 waist board, the hovercraft at 26 is a wide floaty board for you, but not for anyone 190lbs already riding a 26cm board. Remember 1cm in width = about 10 cm in length.

Maybe we can jump start the folks with the cad files to post how many square cms a board has, just like many surfboards surface area and volume stats are now available from the shaping programs. I found that the old voile ST 178 had about the same surface area as a 165-168 without a tail cut out, not counting the upturned tail of the standard board.


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