There’s been a lot of talk (maybe too much talk - at the risk of stimulating another free U2 album) about forces and speed lately. Possibly the surf’s been flat.
So, When you go air (not something I get right very often, LOL), do you go faster or slower? Why do you think so?
I suspect it’s going to be like a Brontosaurus theory http://www.youtube.com/watch?v=cAYDiPizDIs
Now you’re just being counterintuitive. Lol
The wave is your source of energy. The instant you lose contact with the wave, gravity and air resistance slow you down. That is my intuitive opinion.
I dunno, when pitched from the lip in larger waves it seems I hit the bottom faster then on a controlled drop…lol
Nobody listens to me, but I experimented with catching air before many surfers I heard even tried. Skateboard r guy’s caught air all the time…one day I had a crazy idea! I think my friend talked of catching air. Anyway, I decided to give it my all…I couldn’t find anyone to surf, so I paddled out on my six four fish twin fin in two foot perfection…so four to five foot faces…
Here’s EXACTLY what I did: catch wave, generate gobs of speed, crank it very tight off bottom - aiming almost straight up! And ollie it… this sent my entire torso in flight! I was sailing in the air in slowmotion…and I noted the wave passed me by,…and splash! This scenario happened ten more times…at this point, I almost called it quits. But I gave it one last shot, and this time, I flipped the tail around w rear foot/leg in full ollimode…splash down! I actually made it!!! But I think I only flew 1’ out of my wave. Not bad for 1980-81’ I think? And I was a nobody. Well, I wasn’t a nobody,.I was a teen who got sucked into a surf gang. That’s just how it was.
Answer= SLOW…R …RRRRRR!
I doubt anyone here does airs on any sort of regular basis.
swaylocks is too full of verbose , theorist, arthritic old farts , for [m]any of us to be able to even attempt that sort of shenanigans .
you might be better off emailing jordy smith or mick fanning or most any of the top level pros .
But my guess is …
…they would be too busy actually DOING them … rather than wanting to theorise and ANALyse the ‘velocity’ involved perhaps , eh ?!
Ha ha, Chips-N-fish!
I do air all the time of the flatulent variety!
me too
does it go faster or slower though ?
you could power a city by the amount of hot air unleashed on THIS website , at times …
I wish I could pull airs more regularly to get some sort of quantitative assessment.
When you release the board from the drag of the wave…
Must be faster when you are falling. Board supported by air must be faster than board supported by water.
Take-off for air - released from drag, but cut-off from power source and going up, so probably slowing.
Horizontal flight. Well, if you want to make a section you go over it, right? My secondhand take is that going air is the way to cover a huge amount of ground fast. Just feels slow because your focus has narrowed and you’ve slowed time down, like in deep tube rides (or big wipeouts, LOL).
I’m sure we could derive equations from first principles, but I’ll just concentrate on building boards that can take to the air (no tail flip?), yet can still handle late late drops.
I used to do airs all the time but as I approached 30 years old I tore my acl twice in 12 months. I pop them every now n then but only in weak surf. You slow down in the air, the only time you really go faster is when you hit the lip wrong or late and it blasts you out to the flats which is how I wrecked my knee.
https://swaylocks7stage.s3.us-east-2.amazonaws.com/s3fs-public/IMG_19662583850690.jpeg
https://swaylocks7stage.s3.us-east-2.amazonaws.com/s3fs-public/IMG_19626200768881.jpeg
getting air is the modern version of kicking out
a wave is not like a static concrete pool
never seen anyone get air just to go faster its more of a stalling move
it seems to be primarily a punctuation if anything
the only the air move to generate speed is when its free falling straight down due to gravity in an air drop like at shipsterns, wainea or pipe
but you’ll notice instant accelleration once the fins/rail have made contact again
much more acceleration than the airdrop.
just my personal observations no physics involved
It’s not totally analagous, but when I was a kid and crazy about BMX racing, the rule was to keep your tires in contact with the track as much as possible (and pedaling of course). Once you lose contact, you’re losing speed and wasted energy going vertically instead of horizontially.
The question just reminded me of that scenario.
exactly. same applies in skiing/snowboard racing.
I like Bill’s intuition and he is correct. This situation is similar to e.g. a moto-cross bike; Once the tires lose contact with the ground, decelaration occurs. The exception to this would be if the vehicle (surfboard, cycle, car, body, etc.) were going slower than terminal velocity (32 ft/sec/sec) and then entered a free fall for a distance that allowed it to reach terminal velocity (or a speed greater than it was originally traveling). For a sky diver, 99% terminal velocity is reached after a free fall of 15 seconds. Long story short, it ain’t gonna happen on a surfboard even on the most massive of waves.
See “The Decelerating Wave-Form”.
The moment you leave the top of the wave, you’ll actually be traveling faster then the wave itself. The reason for this is that the wave is slowing down (decelerating) as it shoals (and/or breaks), see my post “The Decelerating Wave-Form”. This means is that whatever forward velocity you have (forward here being in the direction the wave-form is moving) when you leave the wave will be greater than that of the wave immediately after you leave the crest. This is why you can get air, and still have a chance of coming back down on the face. (Even if there’s some wind resistance, etc.)
As an example, say you’re in a car and your traveling at a constant velocity. You’re a passenger (wearing your seat-belt of course) and you’re tossing a ball straight up (say 5 or 6 inches up) and then catching it as it comes down. The ball will come right back down into your hand. That’s because the ball, when it left your hand was traveling at the same forward velocity as you and the car, and there was nothing to slow that forward velocity down during its round trip back to your hand. But if immediately after you threw the ball in the air, the person driving stepped on the brakes (decelerated the car and you) the ball would appear to travel forward and miss your hand on the way back down. In fact, the ball’s forward velocity did not change, yours did, in this case, because you decelerated.
The same sort of thing is happening when you get air, but here the wave is decelerating and you are the ball.
Also, its an interesting exercise to estimate the vertical velocity of surfers that get air. All they are doing is trading kinetic energy for potential energy. So if you can estimate the height above the wave crest they travel, you can estmate the vertical speed at which they left the wave. Lets say you figure they traveled about h foot above the crest before they started to drop back down, then v = ( 2 g h )^(1/2) will give you an estimate of their vertical speed, where g is 32 ft per sec squared. It’s crude, as it doesn’t account for air resistance, and other possible effects, but likely accurate enough.
So, you esitmate the height to be 3 ft, then v = ( 2 x 32 x 3 )^(1/2) = 13.9 ft per sec (9.5 mph).
Cool question.
The only way you can gain speed is if you land lower then you where you took off to launch. Think of jumping off a cliff into the water. As long as it is a pretty high cliff you are going to hit the water falling faster then when you jumped up.
Otherwise if you land at the same vertical height or higher you are definitely going slower.
i.e. the formula that KC wrote.
On another note, KC you have me thinking here. My instinct from surfing, not launching airs:) but popping over the wave on a quick exit, tells me different. They wave is definitely losing energy, but in the short amount of time people are up in the air for, i.e., maybe a second, it does not seem like the wave is losing enough speed to make a difference.
I pulled up a couple of videos on youtube of the pros landing big airs, and it seems they are pushing off the top of the wave to propel themselves faster then the wave in the “toward the beach direction” i.e. perpendicular to the wave. Also a bunch end up landing on top of the wave, or rotating the board to land it.
http://www.youtube.com/watch?v=ch8jLKJqMBk
Anyways good food for thought, gotta go surf…
Your interpretation that they seem to be pushing off the top, and my suggestion as to why they stand a chance of coming back down on the face (the decelerating) are not incompatible.
Never having pulled off an air, so I could easily be wrong, I just don’t see the kind of postural changes taking place that would indicate a push at the point of leaving the wave. But again, I could easily be wrong.
As for whether or not the amount of deleceration matters…
The actually degree of deceleration will depend (a lot) on bottom topography, a more rapidly changing one, where the water depth is changing rapidly (getting shallower more rapidly) will produce a more rapid deceleration. (Successfull “airs” on mushballs are rare.) But if you watch the direction in which they are traveling transversely (say, towards the shoulder or towards the curl) then I’d argue that there is a greater chance of comming back down with the wave being a greater distance behind them if their initial transverse direction is towards the curl, which is decelerating more rapidly. (So if you are trying to get air on a mushball, just make sure your headed towards the curl when leaving the crest (or lip), it might improve your chances of pulling it off.)
Derivation aside (if you like I’ll provide one), the following should give you some feel for the amount of deceleration that is possible. The formula is approximate,
(Change in forward velocity of wave-form) = (1/2) * square-root(g / h) * (change in water depth h),
where g is 32 ft per sec squared. If we measure everything in feet and seconds, the formula approximates to,
(Change in forward velocity of wave-form) = 2.8 square-root(1/ h) (change in water depth, h)
So, for a gradual bar, going from a depth of 10 to 9 foot (in one second), the above gives a change in the velocity of the wave of -.89 ft/sec. ( about -0.6 mph)
But for a more rapid change, going from a depth of 10 to 5 foot (in one second), the above gives a change in the velocity of the wave of -4.5 ft/sec. ( about -3 mph)
In the first case, the change would appear virtually imperceptible to the observer, and maybe surfer too. But in the second case such a deceleration is unlikely to go unnoticed by the surfer, or at least felt by the surfer. Whether or not he realizes that the wave is decelerating is another matter.
Under more extreme cases when the wave runs over a deep ledge, or reef the wave can almost appear as if it stopped and simply 'jacked". (Please consider keeping this in mind the next time you or you see someone upon take off seem to loose all contact with the face - or be seemingly ‘launched’.)
That said, I’ll like to take a small degression.
Implications for design.
The amount of deceleration, as mentioned in my post “The Decelerating Wave-Form”, is different for different regions of the wave - greatest near the curl, less so out on the shoulder. Which suggests there is a transition from greater to less, moving from curl to shoulder. It then follows that if you’re moving transversely across the face, that different sections of your rail are also experiencing different decelerations. In particular, if your tail is closest to the curl, the forward wetted rail (farthest from the curl) is experiencing less of a deceleration than the tail section of the rail (and tail itself).
But as also mentioned in the post “The Decelerating Wave-form”, the upward flow on the wave-face is also different, this time greatest in the curl region. So it follows that this upward flow is also different in the tail region than on the more forward regions of the rail.
I won’t continue with this here as its not the topic of the post, but it did seem to be an opportunity to offer up some numbers and introduce design into the discussion, though admittedly, probably unnecessarily. There’s also the other fact that a total of zero people have actually read my post “Rails Plane” (which probably should be telling me more than I care to take from it). But when you start putting this all together in the context of design, you wind up with a curious approach to rail design. based on what is actually happening. That rails can operate as hulls, but require an asymmetric treatment -i.e. an asymmetric hull approach. Which was going to be a follow up post to “Rails Plane”, which would have likely met with the same faith as the original post, so I thought I mention it here - totally selfish, my apologies.
Cool stuff KC. The point I am trying to make is that they do not need the wave to slow down to make the landing on the airs.
It is undisputed that the wave is slowing down. You are correct, no argument.
The thing is the surfers are controlling where they land, watch some people do airs or watch a bunch of youtube. They are purposely landing in a good spot by controlling their board on the takeoff. Look up one of the instructional videos on how to do a basic frontside air, they tell you to target a soft spot and not land in front of the wave. They are pushing off from the tail.
for example go to the following link and look at 1:02
http://www.youtube.com/watch?v=p0nJ5-SvieU
He is trying to some funky trick and is messing up the timing and lands behind the wave. In particular, the wave is slowing down, but it is a third order effect compared with the amount of control the surfer has over where he lands( with the exception of me, I will most likely land behind the wave on my ass.)
I am not the physics police or anything, but I am little OCD and haven’t been surfing as much so I get cranky:)
Otherwise the The Decelerating Wave post was pretty neat.