Nah, Kevin no objection to the prod.
You didn’t answer my answer though.
Kevin, would you mind encapsulating your theory of this (these) flow(s) again (in less than 20 words) for the guys who weren’t here last year, or have dropped the thread on your argument?
I’m trying to quit this thread, BTW, just so you know.
How about 23. (The first word is a contraction.)
It’s the total flow impacting the bottom of the surfboard and the respective orientation of the bottom, that makes a surfboard go.
(See my above post to Kenz for a little more detail, search on Dynamics so see more.)
You’re free, my friend.
kc
It’s the total flow impacting the bottom of the surfboard and the respective orientation of the bottom, that makes a surfboard go.
Got it. So the flow up the face makes all the surfboard’s motions possible.
So obviously, right: Why is that guy going the opposite direction of the flow? If the flow is the propellant, and not repellant.
Second question: How do skydivers track across the sky? Because the air is rushing up at them all the time, the crazy guys? (http://www.youtube.com/watch?v=63CwsiAqLcA There’s a lot more–just search “wingsuit” on youtube)
My guess is, its my lack of attention to gravity that’s brought us here - once again.
Gravity’s role is that of counter force to the flow, which a surfer/surfboard uses to get in and stay in the way of the flow. And yes, the motion need not be in the direction of the flow, given a respective orientation of the bottom, the force can result in both a horizontal component and vertical component of motion. In fact if the orientation is suct as to sufficiently reduce the vertical force from the flow, you’ll start dropping. And yes, the upper limit to acceleration to dropping is that which can be obtained by via gravity (approximately, 32 ft per second squared, or 9.8 meters per second squared in most locations.)
Yes, skydivers do drop, because the flow is usually not sufficient to raise them, but hey, make a jump and foolishly pass over the wrong cliff, overhang, or dune and you’ll climb. In fact, attend one of those skydiving schools were they throw you into the flow from a big fan, you’ll climb there too.
You indicated you wanted out, so let me help you a little - gravity is very important. Without gravity things would be very different, for one thing there would be no water waves to surf.
In surfing the acceleration from gravity is the upper limit of acceleration during a vertical drop. That is. you can skim down the face of a wave like a flat rock if you orient the board correctly. But gravity does not limit the horizontal acceleration, nor upward vertical acceleration until you’ve left the wave, as it does in the classical gravity sports, for in surfing you have the propulsive force which is a result of the flow interacting with the bottom of the surfboard, and it is quiet possible to accelerate horizontally in surfing without climbing or dropping, not so in the classical gravity sports, such as snowboarding and skateboarding. It also possible to climb as fast as the flow interaction will enable you to climb.
Are we getting closer to at least understanding each other?
kc
Added as an edit
At some point, please consider doing what you have asked me to do. I understood the request for the twenty word limit to mean ‘keep it short’, so I’ll ask the same.
kc
I have never not understood your theory/argument.
Then it’s your turn. See my request, added as edit in prior post. Be brief, I won’t pepper you with questions. I understand - you want out.
kc
Edit: Spelled brief. breif? Made the correction.
My apologies, but I went right past your comment about the tracks left by snowboarders.
Here’s the problem, given the nature of the movement of water in a waveform, the tracks the surfer is leaving only make his trajectory look like he’s running downhill. Perhaps this changes nothing as far as you are concerned, but the distinction is important.
kc
I covered it. Newtonian spray (standard downwash off any planing surface–see plane photo I linked to at NASA) off the penetrating (inside) edge of the bottom, outside fin blocks the spray, and you know the rest.
EDIT: He is running downhill, on a renewing grade, as I said before hundred times or so.
FURTHER EDIT: A wise friend with several million years of dust on some of his shoes ; ) suggests this:
" I’m not so sure your “constantly renewing grade” isn’t the same thing as Kevin’s “flow”. It might be a matter of perception…"
I’m pretty happy with that.
So, tit for tat? Please consider taking a shot at my request above (post to Janklow) regarding 'reading wakes' - if you're so inclined. I know I'd be interested.
First, I don’t think it’s realistic to make a lot of assumptions from a photograph of a moment in time. A low resolution one at that.
But basically what I see is displacement creating a wake, not unlike a boat wake. Why is it just on the shore side and not on the ocean side? Because there is open air on the shore side which allows the displaced water to splash out. On the ocean side there is a big wall of water that does not allow the same kind of splashing out. In fact, the ocean side rail is submerged in water. There is no air. To get a wake similar to the shore side there would need to be air.
Now as to what is happening and what will happen, it’s impossible to tell from this or any photo. But I will say this, it’s important to remember that the wave is both lifting and moving forward at the same time.
I’d like to know if you have made the trek down to the beach and observed some real waves in motion. There are a lot of tests you can do by going out in the water and observing how the water moves around your hand or a piece of wood. I think this might give you some insight on what you think is going on in the photo.
Shore break is good because there is a lot of power and you can get right in there while standing on the sand and see what is happening. Growing up at The Wedge, I did this a lot. Shore break is a lot like a wave like Teahupoo in some ways. The shore stops the bottom part of the wave almost completely, and the top part (over vertical part) keeps going. I’m telling you this because you will observe that an observed object on the bottom part of the wave almost doesn’t move upward at all. However, the top (over vertical part of the wave) shows a very fast movement in actual water particles moving forward.
This is something you really have to observe in real life, not from a photo. Go out in the waves and experience it. In deep water you can actually feel the waveform lifting you, but you can also feel the movement of the water particles moving in a circle. In shallow water where the wave breaks you feel something entirely different. Don’t take my word for it, go to the beach and tell me what you see and feel while out in the waves.
I have always thought it would be cool to put a 20' diameter by 50' concrete pipe in a skate park that you could skate into and out of. But not just statically sitting there but on rollers so that the pipe would rotate slowly and allow skaters to gain altitude inside the pipe and be able to absorb energy for use that they wouldn't normally have. If the shape and tilt of the pipe could also be altered all kinds of cool stuff could happen inside.
I actually had an opportunity to do something like this in the 80’s. We skated an abandoned funhouse tunnel. Granted it wasn’t very big in diameter, maybe only 10’, but it was skateable. But when we turned on the rotation it wasn’t skateable at all in the traditional sense. It was very hard to pump against the counter rotation side, and the pro-rotational wasn’t fast enough to pull you up.
It’s pretty interesting, because when we rode it a little differently it felt similar to a wave. If we put our boards more sideways the friction would move us up the transition of the pipe until it would get too steep and the wheels would lose traction and slide out. But if we angled it down slightly we could carve it down to the bottom before getting too high up the transition and sliding out. And there was a sweet spot where you could kind of hold a line while kind of half rolling, half sliding.
It was a lot like surfing in some ways, you know, some sort of energy lifting you up and gravity pulling you down.
Well I’ll be damned…
Thanks. I’ve been to the beach, and I’m aware of the trajectories of the water particle in waves. You should try and visit the beach too, and familize yourself with some wakes as they are actually produced - so wouldn’t have to risk a guess.
Thanks again,
kc
Thanks. I've been to the beach, and I'm aware of the trajectories of the water particle in waves. You should try and visit the beach too, and familize yourself with some wakes as they are actually produced - so wouldn't have to risk a guess.Thanks again,
kc
I will go tomorrow and see if I’m missing anything.
being a former student of what I think is this subject back in 1974-1979 it seems that you might be trying to reinvent the wheel as over the past half a century I’m sure the dynamics and studies about all this have been put down as part of some grad students way of encorporating their play into credit towards a masters or phd…
Seems like spending a little time in the research libraries of Woods Hole, Scripps, University of Miami at Coral Gables or the University of Washington(where I labored) would turn up all the material you are looking for you to put togethor the models you are building if it hasn’t been built already. Plus there’s a multitude of tenured professors at each one of these schools as well as across the country and around the world or even within the Naval Research Lab that can answer these types of questions better than a bunch of garage builders here on swaylocks…
Here’s a couple writeups of others who tried to document/explain the same thing
maybe you’ve seen them before maybe not…
http://blackmagic.com/ses/surf/papers/wavephysics.pdf
http://topex.ucsd.edu/ps/energy.pdf
http://entertainment.howstuffworks.com/surfing.htm/printable
http://users.tpg.com.au/users/mpaine/thesis.html
sometimes some of these questions raised remind me of the discussions held with the feinstein inspired brainiacs in my math classes on choas theory and other esoteric forms of writing weird symbols on a chalk board versus the discussions held with the engineers populating my applied physics classes. Maybe that why I react the way I do when I see such similar “lets put a box around the world” talk.
As a scientist in school I used to believe one could explain everything with the laws of nature and appropriate mathematic models until I entered the world of business and started dealing with people and money versus calculations.
Surfing and growing up on the beach taught me the same thing(even though I refused to listen as a youngster) as every nuance behind every wave(and everything in nature) is different from the next no matter how similar they appear from afar. The greatest surfers are the ones that understand and can adapt their skills on the fly based on feel, vision, and anticipation.
Sure equipment and its design plays a part as does some basic understanding of physics but obtaining an instinctive feel to stay with the flow of your environment as it dynamically changes around you is what makes the great ones great no matter what and where they ride… They used to call it balance and timing but I bet its related to alot more than standing on a piece of foam.
don’t mean to insult but realistically I almost positive there’s better answers to these questions you can obtain elsewhere than here in the garage…
Oneula,
Though I’m not sure what your post was about, it did sound as though you don’t like reading this kind of thread. So why risk getting yourself upset? It’s a big forum, lots of other threads to read – have a ball.
kc
Well-said, Kevin, but I think this is key: you get what you pay for–when you inject yourself and your interests into the culture, you don’t get to tell people not to respond to it–they have the same right you do. You are after all taking up space on the front page. There may be some editorial response, and oneula’s isn’t out of hand.