energy man
you just harness it
and ride it
ride sounds waves with your mind
catcha beam of light
simple
its majic
it just is
its obvoiusly flat where you guys are at!
dont spend to much time wondering why and how a clitoris works
just find it
and lick that sucker
What if, by understanding it better, you could harness its power more effectively? Kevin?
Do some research on something that really matters, will ya?
Because I don’t think anyone on this WEB FORUM is getting TOO MUCH of dat kine power.
Right on silly… You guys need to surf more.
In my 42 years of surfing I’ve seen many techno guys theorizing about this and that, but a good surfboard is subjective. Make and ride lots of them, see what works, and follow that path.
You can sit in front of your computer writing and debating your latest thesis, or you can go surfing. Some of the world’s best surfers have no clue what makes their boards work, yet they rip and have fun.
Surfing isn’t pure science. For me, it’s about the “feeling” of being in control. I’m not looking for the fastest or most efficient board on earth, just the one that allows me to be where I want on the wave. Different waves require different kinds of equipment. Sometimes I want to go fast, and sometimes I want somehting that won’t outrun the wave.
I’ve got about 30 boards in my garage, a few in So Cal, and a bunch more in Hawaii. I show up at the beach with at least a couple. Instinct and experience allows me to pick the right board for the conditions every time.
No matter how much thought you put into it, you’ll never be able to make the “perfect surfboard” because it’s different for eveybody. The best surfboard is the one that makes its rider smile the widest.
energy man
you just harness it
and ride it
ride sounds waves with your mind
catcha beam of light
simple
its majic
it just is
its obvoiusly flat where you guys are at!
dont spend to much time wondering why and how a clitoris works
just find it
and lick that sucker
Fair enough, but it makes me wonder why you are hanging around on a physics thread if all you want to do is lick and enjoy.
And don’t tell me not to think. . . . it’s my head !!
.
You can sit in front of your computer writing and debating your latest thesis, or you can go surfing.
Guess what ? . . … . . one can do BOTH. Surprise !
(Though I think Kevin’s particular theory of this flow is an upside-down cloud of gas, it is kind of symptomatic of surfing, isn’t it, that a few guys will always show up on these threads just to say (after they’ve read any of it? One wonders…) “Hey you guys knock it off in here!”)
Anyway, it’s an upside-down theory that tries to supplant gravity and the wave as the prime movers, and as such, as Roy says, bunkum.
And the stream coming out of a faucet stays a stream and accelerates
because
of …
G
R
A
V
I
T
Y.
True,
Just as a special treat for silly et al I calculated 
(while having my morning coffee) that the truth content of the statement “gravity is the enemy of movement” is 16.33 %. . . . .
So the deal is that it’s a riddle, or a quiz, and I will send a bar of wax to the first real Bloke (or Blokess ) who can correctly describe how I figured it out.
Clue: There are many dimensions.
Cheers
Roy
Sorry that’s 16.66% my mistake
:
Flow Considerations
The next time you have the opportunity, watch which way the stern wake tends to break as a motorboat passes. It may not even break, but if it does it breaks away, or out from the centerline of the path in which the boat is traveling. (By the way, if the boat is slowing it will sometimes break towards the boat, please keep this in mind, see below.)
This doesn’t seem to be the case on the wake trails for surfboards, see photo. The wake on the waveside of the wake breaks towards the centerline of the path in which the surfer is traveling, whereas the wake on the beachside breaks away from the centerline, see photo. The question is why? Actually, this may not be an issue for you at all, which is understandable, but I believe it tells you a lot about the flow under a surfboard and so, it’s interesting to me.
A Little Bit About Breaking Waves
A wave breaks when an upper portion shears off because it is moving faster than a lower portion. Simple, but it will do.
The Flow Under A Surfboard
Of course I’m going to assume my hypothesis regarding what makes surfboards go, see initial post above.
When the water hits the bottom of the surfboard (see Dynamics – The Trim Equation for a rough feel as to the general direction that this occurs, or my above initial post) it then moves off to the sides, tail or forward –i.e. towards the rails, some towards the beachside rail, some towards the waveside rail, and some towards the tail, (which is usually in the waveside direction, but not always), and of course sometimes even forward ahead of the board. How much in any direction will depend on a lot of factors, but that’s not the issue here, just that it does.
When the water hits the bottom of the board it looses momentum. The change in momentum results from a change in velocity (its mass doesn’t change), and unless there is a lot of friction between board and water, its not so much the change in magnitude that matters, as is the change in direction, (but fins will impact the magnitude, so there could be a significant reduction in the magnitude too.) As it moves off to the rail, in particular the waveside rail (whether off to the rail proper or towards the tail) the water then moves back into the wave. But its moving differently that the water in the wave now, and you get a shearing effect. You will often see a budging above the waveside rail as a result of this effect, though its usually not that apparent unless an awful lot of water is involved.
But this shearing effect is often very apparent in big tube shots. In fact, its almost always apparent in the wake trail behind the surfers in such shots, see photo. Look at the trail of disrupted water that this surfer is leaving behind; the water above the trail is breaking into the wake path, similar to the way the wave is breaking, and the water below the trail is breaking away from the centerline, also similar to the way the wave is breaking, see photo.
The water moving off towards the beachside rail, is usually is seen as spray (root spray, see Dynamics – The Trim Equation.) but it need not be. Often the angle in which it is send is such that it reveals its change in velocity in the wake trail, the wake again breaking in the direction of the wave, in this case away from the centerline.
Of course a complete analysis at this point would involve factoring in the motion of the board relative to the water in the wave, but even so, unless it’s a really really good design, a lot, and exactly how much depends on an awful lot of other things, of the water is directed towards the rails.
Anyway, if nothing else the analysis is consistent with my hypothesis with respect to what makes surfboards go, but I’m sure others will have their own interpretations. Once again nothing has been proved. In fact, I suspect most will find this just a little too bizarre to accept, or even consider. Hopefully though, some might search though endless number of surf photos on the Net and find some contradictions.
Kevin
In general, I think that your theories have not taken buoyancy into account.
Just something to consider.
Great.
There is a hydrostatic term, however its not what makes surfboard go. And I won’t be getting into it. If you’d like to, please do.
Thanks,
Kevin
Your latest post seems to be just a long winded way of saying “this is what the spray coming off a surfboard looks like”. … . plus some vague stuff about assuming your hypothesis but not proving it. . . .
What, if anything, are you trying to say ?
:
lmao 
nah it was just a cop out really
its out of my depth
so i must succumb to excuses
and childish taunts
im off to the lick thread
but why???
Putting aside whether or not you buy into all this or not.
I don’t know if it would help, but check out the wake his hand is producing. His hand is not interacting in the same way as his board. Also, if you are able to find pictures of the initial (just after release) moments of tow in surfers you will see that their wakes are different, but then change to the kind I describe above. Wakes are also different on some of those maneuvers that are literally burning up kinetic energy, when the surfboard is skimming across the face of a wave like a water skier who’s just let go of the rope.
As I wrote, it proves nothing, but its not inconsistent with the notion that the flow under the board is hitting the board at a high angle from underneath and moving outwards towards the rails, tail and nose. This is quite different from just viewing the flow as moving from nose-to-tail (and designing for it as a result.)
On my budget, you take evidence where you can get it.
Kevin
Look at how fast the flow under this guy’s ski is! Maybe we should be building our sufboards MUCH narrower?!
Seriously–if the argument is that the upwave flow is the predominent force of propulsion in surfing, let’s look at some common sense evidence…
Any crestward flow is northbound
Where does he end up versus where he started?
Which propulsive force is dominant? Wave’s overall motion
Gravity’s pull is down.
Does he go with flow or gravity to stay in wave?
Again, after his ride, which force netted him his gain? Gravity.
Add results of 1) and 2)
If less than, your argument is moot.
If the same as, your argument is moot.
If more than, I’m looking forward to paddling out next time.
we must be harnessing the kinetic energy of the wave through water pressure on the bottom of the board
how else is it transfered to the rider?
all this energy is transfered across the ocean form molecule to molecule
until it reaches the bottom of of your board (in the form of water pressure)and you harness it and change its direction
use it for sideways/forward propulsion
by saying its all gravity
negates the freaking existence of the bloody wave
Can someone help the gentleman subtract gravity from the equation?
Or perhaps explain how gravity aids the surfer in applying pressure to the water?
Not at all Silly.
It’s like this. . . in order for the wave to apply pressure to the board there has to be a OPPOSING FORCE. . . … . in the case of vertical water movement this opposing force is constantly supplied by gravity. . . however in the case of any horizontal water movement the only opposing force available is the inertia of board and rider. . . and it is not possible for this inertia to act as an opposing force when the board and rider are travelling beachward at the speed of the wave front, because this beachward movement is already faster than the horizontal water movement and thus there is no opposing force. . . . when a board is in trim it is travelling towards the beach with the wave front and is thus already going horizontally faster than the any horizontal water flow. . . .
So we are harnessing the kinetic energy in the wave. … namely the upwards movement of water . . … . this produces pressure on the bottom of the surfboard by opposing gravity !!!
It’s really easy to understand, actually. . . just try pushing a billiard ball horizontally with another billiard ball . … . there’s not much pressure between the balls once they are travelling at the same speed. . . and NONE if the one you are trying to push is rolling away faster than the ball which is trying to push it!
Now try pushing a billiard ball upwards. . . .HMMMMM, constant pressure due to the opposing force of gravity.
Kevin’s visual ‘evidence’ of pressure is almost entirely evidence of pressure due to the force of gravity opposing the water in the wave
Unless there is an opposing force it is impossible to redirect that force. . . so any horizontal water movement is only able to move an object (once inertia is overcome) in the direction it is travelling in. . . towards the beach, and it can only do it at a speed which is LESS than that of the speed of the wave . . . in other words it doesn’t explain down the line surfboard movement OR the fact that a surfboard and rider move fast enough to stay with the beachward movement of the wave.
To conclude, under the influence of horizontal water movement in the wave by itself, surfing would be impossible .
Get it yet ?
.
Some good points Roy but a few too many words … the anti-gravity crowd is bound to float back in here and try to selllllllll yyoouuuuuu sssssome mmmmmorrrrre offff ttthhhheeeirrrr gassssssssss
(Can we just go ahead and let Gravity be the primary force? No? The planing-down-wave thing is so temporary… as a matter of fact, since Gravity is ubiquitous and a prime mover–yes it is Kevin–and thereby facilitates life as we know it, I daresay Gravity is akin to the other G-word… yes, and the lot of you Gravity-skeptics are heathen and heretics–you can’t do a thing without IT, boys)
Yes, too many notes
Here’s some lovely mind bending gravity stuff.
What is gravity?
http://www.faqs.org/…part4/section-5.html
Amazing how gannets can surf ocean waves via the updrafts in offshore breezes which flow over the wave. . . definitely no beachward horizontal movement there, in fact it’s all going out to sea !. . . and yet they can surf much faster down the line than I can… . . using G G G Gravity !!
.
Hey, I’m sorry if I haven’t read everything in detail, but it gets cumbersome and boring.
just one thought: have you noticed that snowboards spray too during turns? but that snow wasn’t moving before the snowboard hit it.
I wonder how, all of a sudden, a mass of water frozen into flakes decides to start moving so that, hitting the bottom of the snowboard at a right angle, it can propel the rider down the mountain.
there must be some kind of magic…
