As I wrote, access to the article is free. Six articles per month apparently. Signing up took less than a minute.
In any case, **you go it! **Short bursts of even higher speeds than the sustained maximum speed may be possible, but according to your theoretical math exercises, even the regularly achieved sustained maximum speeds should be impossible.
i did register Mr. Mik. The article stopped dowloading after p.37 – apparently they are having server difficulties.
Based on what I could read:
The data collected were subjective visual estimates derived from videographic frames. There does not appear to be any actual physical data measurement.
Sample size was small. There did not appear to be replication, making data set variability information vague at best. There appear to be many uncontrolled variables.
I will wait until I can review the article in its entirety before making my final evaluation.
According to the Journal Citation Reports, the Journal of Coastal Research has a 2016 impact factor of 0.915, ranking it 193rd out of 229 journals in the category “Environmental Sciences.”
Read LarryG’s posts in this thread to see the piftalls of estimating waveheights visually. He addresses many of your other criticisims too. Credibly explain why he is wrong without using anecdotal data/observations.
I welcome you to provide scientific and mathematic means to substantiate the velocities you report and claim. Ironically, the intruments you use to measure surfboard speed are based on the physics/science that you appear to scorn.
I suspect we will not likely agree. Further debate without credible scientific/mathematic explanations or substantiation would be pointless…
EDIT:
The Journal of Geophysical Research is a peer-reviewed scientific journal. It is the flagship journal of the American Geophysical Union with a 2015 impact factor of 3.318.
Cyril J. Galvin, 1968. Breaker Type Classification on Three Laboratory Beaches. Journal of Geophysical Research, 73 (12), 3655
You crack me up!
It’s not science that I scorn, it’s people who misuse a pseudo-scientific approach, like you, particularly if they remain ignorant in the presence of clear evidence that their theory is wrong.
You are clearly incapable of understanding that your ‘simple solution’ to this complex problem is wrong. Anyway, I’ll keep on surfing faster than the laws of your universe allow, and have a lot of fun in the process!
One more link and quote, then I’ll stop wasting time on trying to talk sense into you: http://www.surfline.com/community/whoknows/whoknows.cfm?id=1163
Harry Friebel, surfer, ocean engineer and research assistant for the Stevens Institute of Technology responds:
"Answering a question like this is highly complicated – to say the least. There are just too many variables.
…
In short, as I said before, there are too many variables undefined to give a definite answer to a specific ride, but you could comfortably say that skewing everything toward maximum velocity on a 9-foot wave, a surfer is never going to break the 40 feet per-second mark, which is approximately 27 miles per hour."
End quote.
Converting the feet and MPH in Harry Friebel’s quote to more manageable units you get this: A wave with 2.7m face height will not allow speeds above 43.45km/h.
A nice safety margin for my 45.5km/h on an approximately 4m high wave!
In Stoneburner’s universe the maximum speed on a 2.7m wave would be 26.19km/h. I guess that would make surfing near impossible, too slow to keep up!
http://www.surfline.com/community/whoknows/whoknows.cfm?id=1163
“skewing everything ‘toward maximum velocity’ on a 9-foot wave… 27 miles per hour”
Skewing is not objective science.
skew
skyo͞o/
verb
make biased or distorted in a way that is regarded as inaccurate, unfair, or misleading.
Harry Friebel also said,
“However, we can simplify the problem by assuming that the surfer just rides the wave and doesn’t turn up and down the face. Then he travels slightly faster than the speed of the wave, which in shallow water is 19.24 feet per second, or approximately 13 miles per hour.”
Which is 3.32 mph slower than the (average/simplified) Vmax velocity vector for a 9-ft wave that would be consistent with what LarryG and I are saying. This is precisely what LarryG and I have been addressing. Now we have a third validation of the (average/simplified) Vmax velocity vector approach – pretty much the straight track drop and ride on a big wave
You appear to be willfully skewing what I am saying while avoiding any discussion of LarryG’s posts in this thread.
Again please address all of LarryG’s posts in this thread. He and I used variants of the same equations, in a similar way but from different directions, to arrive at similar findings. Clearly, you believe LarryG is wrong too, that is, assuming you read any of his posts before commenting at the end of a thread.
BTW I do not recall you previously posting the height of the wave for your 45.5 kph ride. **Approximately **4m high? Maybe I just missed it…
I would be happy to compare my scientific credentials and accomplishments with yours off-forum Mr. M, anytime.
EDIT:
For those tuning in late, I have consolidated my posts about surfer & wave speeds, related to the original thread, at the following link:
Roy Stewart used to be a big advocate for the gravity effect in surfing, it kinda makes sense that if your speed along the wave is limited by the waves shape and speed then the only known finite value for vector calculations is gravity. Even if you’re trimming along the Fall Line in a stand up wave, sitting in the pocket or pumping along a tube , gravity is a constant value.
We probably need a wave pool with 1000 replica waves to test just one board in various riding methods to find the top speed. Even then there’s be conjecture.
Roy is surf and science savvy and my teenage sons thought he was a unique organic Guru, alternative future primitive woodsman surfcraft designer. I’m sure his boards are collectors items now or soon will be.
I think the on-board measurement technology is clearly capable of producing good and plentiful data in real surf breaks.
Watch this video for what is possible already; Tracking Surf Data with TRACE Technology | World Surf League
Enjoyed that WSL video. Noticed the speed clock behind them increased after the drop, as the surfers entered the tube.
I think this is the key paragraph from LarryG’s early comments:
“But, here’s what’s REALLY interesting: As I tried various values of BDI, the Curl Speed, i.e., “Vcurl”, the speed of the surfer ACROSS THE WATER, remained the SAME! That’s the speed you would measure using a boat speedometer, NOT the GPS speed, which is given in the formulas as “Vsurfer”. Remember, Vsurfer is the speed relative to the BOTTOM, (or the Earth).”
I believe that many observers of this thread operate on speed over the ground approximated by GPS distance and time interval measures.
Stone’s approximation calculations are for speed over the water, Vcurl? I can see how max relative speed would be on takeoff, because the wave slows as it shoals.
Having recently skidded face first along a 6" deep reef, I personally think that land speed is important, but can see the value of relative water speed approximations for foil design (although Surffoil’s latest comments indicate that maximisation of foil lift is unnecessary).
The following will make the surfing speed discussion significantly more abstract, especially since we have already crossed into Relativity with initial take-off velocity Vo. We know that a surfer’s initial horizontal takeoff velocity (Voh) equals wave speed C.
Vo = initial velocity
Voh = initial horizontal takeoff velocity
Vor = relative initial takeoff velocity (Vor = Voh - C = 0)
C = wave-form speed
Vmax = maximum velocity when (actual) Vo = 0
Vult = ultimate upper limit horizontal surfing speed
This new abstract concept took hold after showing “relative” initial takeoff velocity (Vor) is zero (Voh – C = 0).
While Vor = 0 at takeoff, Voh = C. This opens the possibility of an additive horizontal speed resulting from the take-off drop, Vult = C + Vmax. Drop velocity starts out vertical at the top but changes to horizontal by the bottom/trough of the wave.
To achieve Vult = C + Vmax, there can be no friction/drag or water movement toward and up the wave’s face.
[I debated this concept with my brother over the phone today while he was driving out of town for a camping trip. He is better at physics and math than I am. We agreed that **V<em>ult</em> = C + Vmax** is a very real possibility.]
We both plan to keep pondering this concept until he gets back from camping…
there’s one hanging in the Arrow shop in Santa Cruz.has a speedometer build in.I didn’t get a good pic of the paper on it but if you squint you can make it out
I wonder if it would add or subtract to the max speed discussion by measuring the inherent drag of each board ?
Like the other physical dims of length and width, volume and fin positioning, every board could have a drag coefficient value based on its design.
Drag is a significant part of the maximum speed discussion.
Like water movement in the wave face and trough, drag is one of the big factors that prevents a surfer from reaching Vult.
But I do not know how to quantify drag for different surfboard shapes and sizes. I am guessing weight would be part of the drag equation?
surface area .
Surface area for sure. And related to velocity…
My brother and I both agree that ultimate surfer speed on a wave is accurately described by by Vult = C + Vmax.
While not a perfect example, the following is a good example demonstrating the additive speed of a surfboard dropping down the face of a wave traveling at speed C.
A train is moving down the ttrack at 8.2 mph. There is a skateboarder on top of a 5-ft ramp inside a car pulled by the train. The stationary skateboarder and the ramp are moving along with the train at 8.2 mph.
Now the skateboarder leans forward and drops down the ramp. At the bottom of the ramp, the skateboarder shoots forward at 12.2 mph (Vmax) towards the front of the train – 12.2 mph faster than the train is moving. Relative to the ground outside the train, the skateboarder is traveling at a speed of 20.4 mph (8.2 mph + 12.2 mph = 20.4 mph).
I am thinking an effective technology for measuring surfer/surfboard speed might be a hot-wire anemometer. It could be placed in the leading edge of a center fin or just in front of a center fin (minimal sensor drag).
Larry Goddard asked if I could post his reply:
I’m happy and thrilled that somebody else decided to analyze the question of wave speed and surfboard speed. It is not as straightforward a problem in Physics as some people might think.You want to calculate how fast the surfboard CAN or MUST go to stay just ahead of the breaking wave.
First, the analyst must make a few Assumptions (known mathematically as ‘Prior Conditions’). Then, from that starting point, you only need a knowledge of wave dynamics and Physics, plus some first-year Algebra, to derive a Mathematical Model for finding the Surfer Speed, given the ACTUAL or TRUE Wave Height and the Peel Angle.
The TRUE height of anything means ‘Top-to-Bottom’, so that INCLUDES the unrideable portion of the wave that we call the TROUGH. It’s below sea level, and the wave face is not steep enough down there to keep your board moving. After all, the board is sliding downhill, so If you go TOO low on a wave, your board will start to mush out and eventually will STALL. You want to calculate how fast the surfboard CAN or MUST go in order to stay just ahead of the breaking wave. Note that if you are riding a ‘Head High’ wave, your board is still about a foot or more ABOVE the bottom of the wave. If it LOOKS LIKE 5 feet (from the deck of your your surfboard to the top of the wave) , the TRUE height is actually about 6 to 6.25 feet.
You must use the TRUE height of the wave in my Surfer Speed model.
My model says that (for a Spilling wave, at least), you can go AS FAST in MPH, as 7 times the Square Root of the True Height, in feet, for a maximum Peel Angle of 53 degrees from Straight-Off. In GIANT surf, the maximum ‘make-able’ wave peel angle will be much less.
4 ft = 14 MPH
9 ft = 21 MPH
16 ft = 28 MPH
25 ft = 35 MPH (looks like 20 ft at Waimea Bay)
36 ft = 42 MPH (looks like 30 ft at Waimea Bay)
49 ft = 49 MPH
but,
100 ft = 70 MPH! (The peel angle at Nazare in Portugal is much lees than Makaha Point Break.
My model shows that the HIGHER you can get on a wave, (before it goes vertical), the STEEPER the wave face surface is, and the FASTER you can go! This works best for Spilling-type, fast-breaking long walls like Point Breaks. If you are approaching a fast section up ahead, and want to get around it, you need to climb HIGHER on the wave face so you can then dive lower going thru that section. You EXCHANGE Altitude (Potential Energy) for Speed (Kinetic Energy). Your Total Energy while riding on a wave is the SUM of Potential Energy and Kinetic Energy.
BUT, If you wish to position yourself INSIDE the Tube, you must ride well down on the face of a Plunging-Type Wave, where the wave face is not as STEEP. And LESS steep means you go SLOWER! So, you might even need to slow the board down a bit to match the speed of the tube. That’s all right: It’s pretty exciting inside the ‘Green Room’!
Surfers who use so-called “LOCAL Scale”, which is based on the old ‘Hawaiian Scale’ from the 1950s and 1960s, should be aware that the old U.S. Weather Bureau used METRIC, only expressed in “HALF-Meters” rather than METERS. So, a Half meter is about half of 39.37", or about 19.685 inches. If you round that up slightly to simply 20 inches, then a wave that looks like ‘5 feet’ (or 60") is "3 Half-meters, Hawaiian Scale (NOT FEET!). The True Height might be 6 feet, so the Hawaiian Scale is about 1/2 of the True Height, if you include the Trough.
Bob, few surfers have the patience to read my original treatment of “Surfer Speed vs.Wave Height”, so if you want to send the above to Swaylocks, I’d much appreciate it.
Thanks for that Bob. I didn’t know that Larry was still active in the surfing arena, he has some long standing design ideas that will probabaly prove to be prophetic in years to come.
Gday Brett,
Surfing is in his blood. He has some long term interests, such as surf forecasting. I haven’t asked if he’s getting wet much these days. His speed post was prompted by some photos I sent him of a recent South African trip.
Regards
Bob
Bob (bgreen),
Please thank Larry on my behalf for following the add-on discussion to your post of his work and Larry’s accompanying posts. Larry did a great job. My work was/is in no way intended to refute Larry’s.
I approached this to get a general idea about speed and foil size for hydrofoil surfboards. I read Larry’s posts after I had done my first round of calculations that followed my post in Brett’s hydrofoil thread.
My calculations were to determine the absolute maximum (ultimate) instantaneous surfer speed that is possible while obeying the laws of physics. My calculations also assume frictionless acceleration and velocity. Wave height is assumed to be measured from trough to crest/peak – a liquid skateboarder’s ramp. Also, I used Cyril J. Galvin’s research (1968) for my wave speed estimates.
I think most of us realize that a frictionless (ideal) wave, without water movement in the wave’s face, does not exist in the real world (i.e. the line-up). Water movement toward and up the wave face, as well as drag, prevent this “upper limit” speed from ever happening.
The ultimate surfer speed equation (in the ideal environment) can be simplified as shown below. To see the derivation of these equations, go to the end of the blog post at this link:
Bill Wurts
The bit on Hawaiian half meters explains why wave measures in Hawaiian feet seem about 30% understated.
