A Really Stupid Question

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A Really Stupid Question

Postby The Thinker » Sat Feb 16, 2013 11:45 am

May I ask a really stupid question?
Well, another one!

Why does a board travel forwards?
I understand trim and balance and I'm fairly sure center of gravity is involved, but is there a explanation (that can be phrased simply) that explains the relationship between the leveling of the board, the place you stand and the resulting direction of travel?

For the life of me I can't come up with one.

Claerly an unriden board will turn side on in the surf or simply be passed by the wave. The rider needs to be forward of the boards centre of axis but too far forward and the nose dives. The axis of turning is in three dimensions / directions but the center of gravity is a point (albeit it a constantly changing one). I assume that there must be an area / sector of the axis's that the centre of gravity must be in (or within certain bounds) in order for a forward direction to be maintained.

If I am the only person who worries about this stuff please feel free to quietly ignore me :-)

TT
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Re: A Really Stupid Question

Postby Philchapman » Sat Feb 16, 2013 8:09 pm

I think you might be looking for the "sweet spot". Find the sweet spot, and it will all make sense.
Human beings have yet to see the true value of the sweet spot.
The sweet spot is the Dao. :wink:
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Re: A Really Stupid Question

Postby The Thinker » Mon Feb 18, 2013 6:08 pm

Thanks Phil,

I know' where' the sweet spot is, what I have become (mildly) obsessed with it 'Why'.

There must be a relationship between balance and momentum. At some point the center of gravity must pass a point that determines whether the board tracks forward or stalls.

I find this swimming in my mind thats all.

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Re: A Really Stupid Question

Postby Philchapman » Thu Feb 21, 2013 11:12 am

I like the question. As to "why".... well I'm pretty sure it would be impossible to come up with any kind of scientifc/mathematical formula that fits all people on all boards on all waves, or even one person on one board on one wave. Too many variables to calculate. I could be wrong about that though.
Any thoughts where to start???...... Rider weight, board weight, board shape, wind direction and strength, wave power/steepness (including height and wave interval), rider positioning on the wave, what you had for breakfast.... etc., etc....
I'm happy enough with "catch the wave as it breaks, fall forward with gravity, lean left or right to turn".
That, and "try not to fall off".
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Re: A Really Stupid Question

Postby Black » Thu Feb 21, 2013 11:42 am

I seem to remember a surfing film that shows a blackboard full of equations and it says something like; it takes a whole blackboard of equations to describe what a surfer does by instinct.
So even though you may find some formulas, it really doesn't help you surf, that has to be done by feel. As Phil says, catch, turn, don't fall and enjoy!
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Re: A Really Stupid Question

Postby Philchapman » Thu Feb 21, 2013 12:00 pm

Aha.... I just "Knew" it had something to do with angular momentum! :lol:
http://mag.digitalpc.co.uk/Olive/ODE/ph ... w=ZW50aXR5
The key phrase that stuck out at me was "unconscious masters" in the last paragraph. Thing is, we don't "know" the ins and outs of it intellectually, and if we tried to work it out when surfing we'd fall. Instinct and unconscious processes seem to play a large part in "how" we surf, know how to adjust weight/move our feet to keep in trim, etc. All interesting stuff though!
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Re: A Really Stupid Question

Postby MrMik » Fri Oct 31, 2014 8:12 pm

Philchapman wrote:Aha.... I just "Knew" it had something to do with angular momentum! :lol:
http://mag.digitalpc.co.uk/Olive/ODE/ph ... w=ZW50aXR5
The key phrase that stuck out at me was "unconscious masters" in the last paragraph. Thing is, we don't "know" the ins and outs of it intellectually, and if we tried to work it out when surfing we'd fall. Instinct and unconscious processes seem to play a large part in "how" we surf, know how to adjust weight/move our feet to keep in trim, etc. All interesting stuff though!


The link does not work any longer, not sure where it was pointing.

Here is an article that shows how complicated it really is: http://www.hiper08.unina.it/cd%20hiper% ... iviero.pdf

When the link stops working, search for some part of :
SURF HYDROMECHANICS
Carlo Bertorello & Luciano Oliviero,
University of Naples “FEDERICO II”, Italy
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Re: A Really Stupid Question

Postby Black » Fri Oct 31, 2014 10:54 pm

Ah yeah Italy, that great knowledge base of surfing. :?
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Re: A Really Stupid Question

Postby Philchapman » Sat Nov 01, 2014 7:38 pm

http://www.hiper08.unina.it/cd%20hiper% ... iviero.pdf

If that was all a load of made up mumbo jumbo, would anyone know or care? Great bed time reading. I nearly went into a coma just scanning through it.
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Re: A Really Stupid Question

Postby MrMik » Sat Nov 01, 2014 9:02 pm

Here is one that is much more easy to digest: http://uncw.edu/phy/documents/grissom_06.pdf

:-D
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Re: A Really Stupid Question

Postby MrMik » Sat Nov 01, 2014 9:20 pm

And this one:

http://www.konfluence.org/AJP_Surf.pdf

Even an unconscious surfer can catch a wave, if given an opportune push. But a skilled surfer
apparently taps into a limitless reservoir of energy. Here we argue that the extra energy comes
from hydrodynamic lift – the turning of a flow.
This article starts with a review of the speed and height of surf waves, and compares the energy
budget from wave motion and falling down the wave with the observed GPS speeds of some
surfers. We then describe how hydrodynamic lift of the surfboard can provide extra thrust to
propel a surfer to high speeds in the frame of motion of the wave.


Navier-Stokes.png
Navier-Stokes.png (3.65 KiB) Viewed 64 times

(1)
Equation (1) is the famous Navier­Stokes equation of fluid dynamics. It is the equation
describing the physics of ocean waves. It can be written down, but not so readily solved. The
mathematical challenge is that equation (1) is non­linear; there are no general simple solutions as
there are in other areas of physics, such as planetary motion.


In other words: Surfing is more complicated than rocket science! :lol: :lol: :lol:
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Re: A Really Stupid Question

Postby Black » Sat Nov 01, 2014 9:27 pm

Hmm, that article has piqued my curiosity - it does sound interesting.
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