BINGO ! The waves you ride, have more energy than the waves in Kentucky.
The math and physics are simple Mr. M, regardless of geophyscial position on this planet.
The velocities I posted are consistent with those reported by Bgreen and LarryG earlier in this thread. Angle A is consistent as well.
https://www.swaylocks.com/comment/376204#comment-376204
https://www.swaylocks.com/comment/376206#comment-376206
https://www.swaylocks.com/comment/376207#comment-376207
Hi Bill, from what I can gather your friend’s boat speedometer would have been measuring speed through the water. Since the water in wave is also moving forward to a certain degree I think you could probably add that speed to the across the water speed. So in conclusion I think you probably were traveling as fast as you thought you were.
Velocity vectors for Wave Speed (C), Transverse Velocity (Vtrans) and Maximum Velocity (Vmax) – viewed from above wave.
What a lovely board Mik !
I was hoping it was th single fin that gave you the speed.
Your vector is correct in showing how Vmax is derived from a forward velocity and a transverse velocity. The problem with your method of calculating Vmax is that velocity derived from gravity assumes a starting velocity of zero. This would be accurate just prior to the first bottom turn of a wave. Once you turn and drive off your bottom turn, you go back up to the lip and now you have a higher starting velocity (Vo) that is now kinetic energy to be added to the potential energy of the wave (wave height * gravity * surfer mass + 1/2 surfer mass * Vo^2). Now rinse and repeat as long as the wave runs and you’re only limited by air/water drag (this would be a calculated terminal velocity). This is how speed is generated via pumping. It’d be interesting to calculate how fast pros go on smaller waves where the wave velocity is very low but they can utilize fins and human motion to generate velocity.
Another way to visualize is to remove the wave speed and think of it only as a stationary endless quarter pipe with a skateboarder pumping down the line. Obviously Vmax is greater than mgh in this case. Kinetic energy can be generated via pumping by the skateboarder.
I have said the same Pretzel – i.e. what we used to call the “roller coaster” approach to riding a wave.
But now, I’m not entirely convinced that is true. The question is how much shoreward velocity is lost once you have returned to the crest/lip of the wave. Second, wave height has dropped by the time you have made the first re-entry. I suspect pumping has greatest impact when surfer speed has dropped below Vmax.
Certainly, there is a terminal velocity due to water drag.
But on big waves, there is little or no pumping. It is pretty much a single drop. So, I am mostly looking at maximum sustained, straight track velocity.
If you measure the rider angle relative to the direction of wave motion, you can readily determine surfer velocity based on wave speed (C).
This is what mtb said in an earlier post. (But I am thinking drag may negate this):
https://www.swaylocks.com/comment/376216#comment-376216
EDIT:
Also I think LarryG’s points regarding GPS measuring of pro-surfer velocities are good ones. It is likely the GPS measurements are artificially high due centripetal/centrifugal acceleration being inaccurately measured as velocity increases.
Yeah, a very special board. Hand shaped to surf similar to my favourite type of board, but to be especially at home in waves that are too big for my comfort zone. I have only surfed it twice so far. I used the McCoy extended tip Gullwing fin, but the 45.5km/h top speed was because of the wave size, and because no-one got in the way for once.
I think that a single fin (at least a good one) certainly helps to reach maximum paddling speed so one can make it out the back, and then to get on to a wave in the first place. I think a single fin probably also allows higher top speed to be achieved while racing along the face, but I’m less certain about that.
However, the top speed of the surfer is predominantly dependent on how much energy is provided by the wave. So even an untalented surfer like myself can get quite fast on big waves, but it takes expert skill to extract the maximum of speed out of any size wave.
There are many waves that will spit you out, or push you at a faster rate than what you get riding the wall. I really enjoy that burst of speed whenever I get to experience it.
Question… if you throw a rock down from the top of a building, will it fall faster than if you just drop it, or will it hit the ground faster?
Unfortunately the Trace does not use open source software, so assessing how much it gets wrong is more difficult. However, the results I get appear very believable. If you know of a better device, let me know and I’ll use that to collect data.
I have tested the repeatability of the Trace’s data collection and analysis by mounting 2 Trace devices on the same board, and they produced virtually the same results.
The surf session with the top speed of 45.5km/h can be viewed here: http://surf.traceup.com/stats/u?uId=628632&vId=23417 Unfortunately the website does not show the speed variation during a wave, but the phone app does.
Waves 3 and 4 reached speeds of 20.8km/h and 26.1km/h. See how short and straight the ‘waves’ were? i don’t have video footage, but I am quite certain that these were waves that I did not manage to catch. So I had to get faster than 26km/h to even get into the waves on that day. It shows that the speed gained during the drop is in addition to the speed required to even enter the wave. Alternatively, they might have been wipe-outs, but I don’t think so.
The screenshots from the Android phone app show coloured lines ior the individual waves, the colours indicating where the maximum speed occurred.
Wave 5 shows that the max speed does not have to happen on the initial bottom turn. In fact, there may not even be a bottom turn, particularly on bigger waves.
The ‘Wave 12/13’ screenshot is from the previous days session and also demonstrates that the speed maximum does not always occur during the initial drop. Note that the wave was 145m long, and the speed maximum was around the middle of the wave. More session data for that day here: http://surf.traceup.com/stats/u?uId=628632&vId=23328
.
**Here is one more simple ‘proof’ that maximum surfing speed cannot be limited by free fall speed: The existence of aerials. **
If the kinetic energy of the surfer was only obtained from falling in earths gravity field, then it would be impossible to reach any positions higher than the initial position. I know from personal experience that it is entirely possible to be catapulted several meters higher than the wave. In my case it is usually an undignified emergency exit to avoid a closeout, but you can watch any modern surf movie and see repeat offenders, blatantly breaking the ‘laws of physics according to Stoneburner’, and landing with control, just for fun, to do it again and again.
Depends how you define “fall faster”. It will hit the ground in less time and at a greater velocity if you throw it down. It will fall at the same rate though (gravity). There’s relatively simple kinematic equations that explain.
The rock leaves your hand at an initial velocity, then when it hits the ground it does so at the velocity due to gravity (gravity * height) PLUS the velocity when it left your hand. If you just dropped it Vo would be zero, thus it would hit the ground at simply gravity * height. So it falls (aka accelerates) at the same rate (9.8 meters per second squared). The velocity at the ground would be faster if thrown and it would reach the ground in less time.
Unless the building is so high that the stone reaches terminal velocity.
Imagine dropping a table-tennis ball and then whacking another one downward from the same building using the racket.
The ball whacked would initially be faster than it’s terminal velocity, then slow down until it falls with it’s terminal velocity.
The dropped ball would accelerate until it reaches the same termninal velocity.
They would both hit the ground with the same speed, but the whacked ball would arive a little sooner.
Early this morning, Brett/Surffoils and I discussed my calculations via email. Brett commented, “I think that explanation makes it clear what you mean.” So I am posting that explanation here.
As always, “Accept. Reject. It does not affect me.”
A day or two after calculating wave speeds for Brett’s hydrofoil thread, it occurred to me that the physics of maximum surfer speed are incredibly simple. They are directly related to the speed of an object sliding down a frictionless inclined plane or free-falling from the same initial height. After the object has dropped or slid to the bottom, the final velocity is identical for both free-fall and inclined plane. So, I compared final drop/slide velocities with wave speeds for various wave heights and realized that final falling/slidiing velocity is the maximum speed a surfer can reach on a big wave.
After that, ride angle and transverse velocity calculations were simple.
Yep. There are some difficult parameters to quantify, e.g. the classic debate over “pumping.”
To begin sliding down a wave face, surfer shoreward velocity must first equal wave speed (C), net velocity = 0. Essentially, a surfer’s initial velocity (Vo) at the top of a wave for take-offs and/or re-entries must = C. (Relative Vo = 0; surfer shoreward speed minus wave speed equals zero).
To return to the top of a wave after a drop, surfer shoreward speed has to drop below wave speed C. Then by the time the surfer is back at the top, he/she must be at wave speed C again to begin sliding down the face. So, the roller coaster approach (pumping?) does not add additional starting speed for each new drop. Again, maximum velocity is related to wave height.
Finally, my values are very close to those of LarryG – independent results substantiating one another. Our results were based on similar and/or related equations.
Because my method is simple, it increases my confidence about the findings.
I have consolidated my posts at the following link:
Well of course I continue to reject your conclusion, because it is still wrong.
Your statement that the physics involved are incredibly simple, combined with the fact that your conclusion does not coincide with real life results, does indeed make the situation very clear: You thoroughly misunderstand something and you are over-simplifying.
Your theoretical model fails to explain the real world results.
Apparently you thought I was postiing in reponse to you Mr. Mik. Sorry for the confusion. My post #114 was not in response to post #113, or any of your comments.
It is a general post for clarification, prompted by a comment made by Surffoils during an off-forum discussion.
However, the initial/starting velocity (Vo) portion of post #114 does relate to Pretzel’s post #107.
You choose to ignore the evidence presented and continue to claim that you found a very simple solution to a very complex problem?
Here is another simple way to show that Stoneburner’s conclusion about maximum achievable surfing speed is wrong:
Watch the video of the 2011 Pro surf event at Snapper rocks and note the size of the wave faces: https://www.youtube.com/watch?v=1GkO_MFjuUw The video shows highlights of the entire event from start to finish, and some of the largest waves must surely have been included in the footage.
That is the event in which they measured the top speeds achieved by some top professional surfers, according to this article: https://www.surfertoday.com/surfing/5126-top-surfers-check-speed-and-distance-in-a-wave One sentence seems particularly noteworthy to me: “The benchmark can be set in the 45 km/h mark, in the near future, experts say.” I have no idea who the ‘experts’ are and how they estimate that the limit will be around 45km/h, but it just fit’s so nicely with my own result of 45.5km/h. I suppose there is an absolute ‘speed limit’ because of the exponential increase in wind resistance and drag forces at the board/fin/water interface. Unfortunately the video link to more details about the speed measurement does no longer work. https://www.surfertoday.com/videos/5125-analyzing-maximum-speed-in-surfing
Then use the splat calculator The Splat Calculator - A Free Fall Calculator or do your own math to find what height of wave face would be required to achieve a top speed of 39km/h, if Stoneburners hypothesis was true (that maximum surfing speed cannot exceed the theoretical speed achieved by free falling the height of the wave face).
What you will find is this: The waves faces were certainly no higher than 3m at any time during the event, which should have resulted in maximum speed of no more than 27.6km/h, according to Stoneburners math.
For Mick Fanning to reach 39km/h, the waves would have to have been over 6m high, and for Kelly Slaters 32km/h they would have to have been over 4m heigh.
By saying I am wrong, you are saying most of LarryG’s posts in this thread are wrong too Mr. Mik…
The values I reported are Vmax velocity vectors — sustainable maximum velocity.
EDIT:
Furthermore, final free-fall speed is identical to final speed at the bottom of a frictionless slope when initial height is the same. But, the “velocity” is vertical for free-fall and horizontal at the bottom of a slope. Since speed is the same, the equation for free-fall speed is simpler.
——-
I found a journal article titled: The Maximum Speed of Surfers
You can read it for free after signing up at https://www.jstor.org/stable/25736203?seq=1#page_scan_tab_contents
It’s an interesting read, I don’t want to breach copyright and repost too much of it here.
In a nutshell, the videogrammetric analysis confirms that Stoneburners assumption of max attainable speed is wrong and that my measurement of 45.5km/h is typically achieved on 4.25m waves (face height). So my wave size estimate of 3-4m for that day was pretty good it seems. I was sitting far out from the (small) pack, only interested in the biggest ones.
The author William R. Dally used the ‘Maximum sustainable board speed’, not the speeds obtained during drops or turns. He also excluded pumping. He used the “Wave Warriors III” video and identified 29 ‘critical limit surfing’ sequences where the surfer is surfing in a nearly direct line along the wave face, without attempting turns or acrobatics and without outrunning the wave. The methods used to reduce measurement errors are described in detail. He also discusses prior work done by other researchers, including using land based surveying equipment and scaled surfboard models in a standing laboratory wave. All the results are clearly very close to each other, and miles from Stoneburners assumption.
Maximum sustainable speed does not exclude bursts of speed beyond Vmax. And the basic physics that accounts for that is simple but abstract. But because the concept is abstract and instantaneous speed calculations likely involve calculus I did not attempt to discuss it in this thread.
Without access to the referenced journal article, I cannot comment about it…