Surfer & wave speed (measurement and technical considerations)

General Discussion
61

Hello Larry,

 

When I get back home, I think the Jeffreys Bay cntest is on. It might be worth contacting them as they tested the gps last year. I'll try to look into this. With the growing number of unversities offering surfing 'degrees' there must be someone interested in researching this. There are a couple in Oz.,

You may get some photos from a guy called Warren who just returned from the US and had a board made based on one of your designs. I asked him to include you in, when he sent photos.

 

Bob

62

I think I commented on this before, but I saw the Red Bull Mentawai show and they measured Mick Fanning at 42kph, by radar.

 

Then a few days ago I saw Storm Surfers on tv, with Tom Carroll and Ross Clark Jones. I think at fastest they measured was 60 plus kph, using a sensor that had GPS, accelerometer, etc.

 

You're right Larry about the position of the sensor. Imagine if you put it on the tip of the nose... there would be flashes of high speed. In the board between the feet would definitely be best.

63

[quote="$1"]

In the early to mid 1960's, Bob Shepard was riding a pintail balsa gun, on the North Shore, that he had made.    The board was fitted with a boat speedometer that used a pitot tube pickup, at the base leading edge of the fin.   Many of us thought we were going close to 45 mph, on 15 foot Sunset, and 20 foot Waimea. But Bob was reporting 24/25 mph on the drop at Sunset, and 27/28 mph on the drop at Waimea.   We sure thought we were going faster.   Just shows that you can't always trust your senses.  The boards in use at that time were typically 10 to 11 feet long, and in my case 10' 5'' x 38 1/2 pounds.   Those big paddle in guns would really move, when driven by a significant wave.  Point is, we are going slower than we think we are.

[/quote]

I decided to move this up, as it relates to several recent posts.     I'm sure there is more sensitive instrumentation available today.  Perhaps a digital speedo' with memory.    Waterproof of course, would be in order.

64

these can be used with good results but they have to stay"line of sight" in other words if you put them in a back pack a run a dirtbike through the desert you'll get some insane,unbelievable numbers lol.

http://www.amazon.com/Quality-WAAS-Enabled-Lightweight-Waterproof-Receiver/dp/B0045AG168/ref=sr_1_4?ie=UTF8&qid=1305734003&sr=8-4

 

i have a very similar model that is not waterproof. aftermarket handlebar mounts are available the could be rigged to work in a leashplug or something if anyone is into it enough to try it. it's do-able. i've dabbled in waterski racing and boat racing and i'm also of the belief that we are not going nearly as fast as most would believe.

65

I’m with Bill T on this one just based on personal experience, not based on ever trying to measure anything.  But, when I was younger I used to waterski, sometimes at a decent clip (35+ mph).  Having surfed a fair number of waves, I have never felt that water-hardening-underfoot sensation on a surfboard that you get when going that speed on a waterski.  Maybe that’s just the thinness of the ski versus the surfboard?  But also having fallen behind a boat at that speed, the sensation is not much like I’ve ever had falling off a surfboard (even on bigger waves).  Off a surfboard you tend to skip once?  Skiing you skip across the water a lot more. Check out this video – a number of guys bounce 3, 4 times before they penetrate, and that’s on a slalom course (not speed skiiing). 

http://www.youtube.com/watch?v=YVA5W7mdGSc&feature=related

It just seems to me if anyone was ever doing 50+ mph on a surfboard, when they fell they would skip more like 8 or 9 times?

As for how fast CAN you go on a surfboard?  Well, on a tow-in board, as fast as the craft pulling you, and then some if you crack the whip.   On lots of jetskis thats at least 65 mph, and from what I read there is at least one that has hit 90+ mph.  If you were so inclined, you could get pulled into a wave at somewhere around 100 mph, I’d reckon.

Who wants to go first?  maybe before the 100 foot wave, we’ll see the 100 mph tow-in?  You would need one HECK of a glassy day!

Here’s a video of a guy waterskiing 156 mph, if you think getting pulled that fast over water is impossible?

http://www.youtube.com/watch?v=R-el1H3PUG0

And a woman BAREFOOT water skiiing 100 mph (neck brace seems to be a good idea!)

http://www.youtube.com/watch?v=fn0aiYi8al4&NR=1

66

Hey guys...Howzit?

This is getting pretty interesting, once again! Anybody remember the famous "Cannonball Wipeout" at Waimea Bay, (back in the '60s, I think)? I can't remember the well-known big-wave surfer's name, but we all remember how he skipped down the face of a big one at the Bay, and got clobbered at the bottom of the wave, right in the impact zone.

Yeah, I guess the water skiers experience just how unyielding water can be when you hit it at high speed. Something few of us non-tow-in mere mortals ever get to experience first hand.

I still don't know how fast those guys on those 50 ft + waves are going when trimmed up high racing across the wall of water. It's gotta be pretty close to 50-55 MPH. If one of those giant waves dumps on you, you could find yourself suddenly immersed under 30-40 ft of turbulent water, maybe more, doing a 'deep dive' without having had time to equalize the pressure on your ears. Goodbye eardrums! Cold water in your inner ear could be very disorientating, not to mention extremely painful. Not good!

I wish we could SEE pictures of those surfers AND the wave they're riding, taken at the same moment their top speed was recorded. The speed by itself is interesting to know, but if we could get a reliable MEASURE of the wave height and the Peel Angle, we could then build a database of many such rides, from which we could determine the Maximum Makeable Peel Angle of waves of various sizes.

If a surfer's peak speed is measured by a radar gun or a GPS unit, that only gives what an airplane pilot calls "Ground Speed". It doesn't tell us how fast he's going across the water.

A pilot can refer to his Air Speed Indicator to see what his "Indicated Air Speed" is, which varies with altitude and outside air temperature...i.e., the air density at his altitude. Then, the instrument can adjust that IAS and display his True Air Speed. He needs to know his actual airspeed to maintain safe flight speeds (too slow, you might stall; too fast, you might rip the wings off).

Does anybody here in the forums, with experience in the boating world, have any suggestions for a tiny speed-measuring device that wouldn't add much Parasitic Drag to a surfboard hull? It would preferably be electronic, a digital device that could record or transmit the readings to a receiver on the beach. That's the ONLY way we are ever going to get reliable measurements of "True Water Speed" (TWS), like the TAS of an airplane.

By the way, if that "60 kilometers per hour" peak speed reading was measured by radar or GPS, then it was his "Ground Speed", i.e., speed over the bottom, and we can calculate the following equivalent Surfer Speed values:

Vm/s = Vkm/hr x 1000/3600 = 16 2/3 meters/sec

Vf/s = Vm/s / 0.3048 = 54.68066492 ft/sec

Vmph = Vf/s x 15/22 = 37.28227153 MPH

If we knew the true speed of his surfboard 'over the water', that is, True Water Speed, or "TWS", that is the same as the Curl Speed, "Vcurl", then we could easily calculate the Peel Angle of the Curl moving across the breaking wave crest.

So, if the peel angle is measured in degrees AWAY from the crest of the wave, then...

The Peel Angle, P =  the Angle whose Tangent is the Square Root of the ratio: Vwave / Vcurl

Or, Peel Angle, P = the Angle whose Sine is the Square Root of the ratio: Vwave / Vsurfer

 

Note that: "Vcurl" is the true surfboard 'hull speed' over the Water, or True Water Speed.

and "Vsurfer" is the GPS or radar-measured 'ground speed' of the board over the Bottom.

In EITHER case, we need to KNOW the Wave Propagation Speed, "Vwave". But, in order to determine the wave speed, we need to measure either the True Breaking Wave Height, Hb, OR actually go out with a long pole and measure the depth of the water in the breaker zone.

All this was covered in my long-winded essay on "Surfer Speed Vs. Wave Height". My resulting formulas for Minimum Makeable Peel Angle suggested that the smallest angle was about 38.67 degrees away from the crest line.

Then, conversely, the Maximum Makeable Ride Angle, which I'll call the "Break Angle", i.e., measured in degrees away from 'going straight off', is about (90 degrees - 38.67 degrees) or, about 51.33 degrees. If it breaks across the crest any faster than that, he won't make it.

So, a surfer would only be able to get up to a GPS speed about 1.6 times as fast as the wave itself (or a hull speed over the water of about 1.25 times as fast as the wave) in order to attempt to make it across the faster parts of the wave. Any sections faster than that, and he won't make it very far. It will close out on him.

If that's the case, then the wave speed would be about 0.625 times his GPS speed, (or about 0.8 times his hull speed). From the wave speed, you could calculate the Water Depth, and from that, the True Wave Height.

If you use "Local Scale" for wave height estimates, you'll find that the true wave heights are about TWICE as high. In other words, a "Head High" wave is NOT "3", but actually is about 6 ft, INCLUDING THE TROUGH. Without the trough, it 'looks like' 5 feet, which is 60 inches, or about 3 "half-meters", the correct unit for Hawaiian Scale, (or "Local Scale"). Local Scale is about 3/5ths of what the wave 'looks like' without the trough, but is only 1/2 of the true Total Height.

'Nuff already! I'll clam up here...sorry, guys! I get carried away...

Thanks for all the comments and added information. Some day we'll know how fast we can go on a wave!

Aloha!

67

Thanks, Larry.

The key for me is the conversion of “good” speed to m/s (fps).  So, if I get a 2 second tube I cover some 11m (35ft) @ 20km/h (5.5m/s or 18 fps).  This fits reasonably well with my experience and also explains why that guy who was “miles away” nearly got run over.

68

Hello Larry,

 

I could be wrong, but from my grom days I remember Tommy Lee's cannonball wipeout on film. Waves at the time were cited as the biggest that could possibly be ridden. That horizion has certainly expanded 

''m not sure if he is following the thread, but "Doc"knows about boats and technical stuff - I'll try to ask him.

 

Bob 

 

.

69

  to add to the confusion(lol), what we're not taking into account here is drag. all kinds of it. do 65 on the road and put your hand out the window. then picture your whole body experiencing this force. then there is my theory that almost all boards today ,so far are too wide to over come the drag devloped over 60mph.in the boating world guys who experiment with set up and different hulls find "walls" or speed barriers inherent to certain designs that cant by overcome easily or at all. these are all cuased by drag. then there is the human factor. take an experienced slalom skier who is used to diong between 30 and 40 mph. bump the speed up to 50. he'll freak out., hold on for a while and then notice it takes more leg power to do anything. . bump it up to 60. his eyes will pop out of his head! no amount of training at 50 will prepare you for over 60. it is not linear.that last 10 miles per hour will feel 2-3 times as fast. slalom skis have deep concave bottoms. no good at all for speed over what they were intended for. waaay to much drag. they also become uncontrolable which is why they are concave in the first place. consider the race ski. typically they are 7' long by 9" wide. if you watch a guy on a race ski his back leg is just a shock absorder and his front leg is almost locked out in front of him as for as he can keep it. why?drag. these ski have to be ridden over 50mph to over come the drag they create at lower speeds.over 50 they break free and stay on plane. from 60 to 120 they still have drag but what are yuh gonna do? they also have a 1/4"bevel from front to back on the bottom  of the rails. the rear 2' of the ski has it on top as well for release. these skis are used in rough water sometimes so they are not lightweight. they are solid ,stout wood. probably 1 1/8 to 1 1/4 thick. the fins are very small compared to single fins  of surf boards. they vary in size a little bit but basically 6" base by 2 3/4" tall and pretty rectangular. all the fin area that is required and no excess drag. so it is these thigns that make me wonder how wide tow boards are and if they will become narrower as great speeds are acheived....or if they will become narrower to acheive them in the first place.

fast forward to :20. these guys AVERAGE 115-125MPH. note the rooster tail coming off the back of their skis. it take 1200 horse power to do this. which brings to the limiting power when surfing but i digress,lol.

http://www.youtube.com/watch?v=CX9g06xKBTU&feature=share

in other news it's pretty common knowledge among performance boats that pitot tubes tend to lie about speed by about 10% so the faster you go the more they lie. they tell you you are going faster than you really are which makes it depressing the first time someone gets aboard with a handheld gps. they can also go the other way due to hull conviguration and the way they disturb the water. i have seen the speed drop off on the gauge while under acceleration at around 80 coming up on 90 mph before,too.

 im sure someone makes a transmitting type gps device even with a recall function but then your talking big bucks. even for the receiver units that are hardwired to a gauge in dash that aint exactly cheap. a company called gaffrig sells the industry standard and can be easily found. transmitting type? not so much.

 

70

Don’t know if you guys already talked about this but it’s pretty cool.

Slater and Fanning speed analysis via GPS and video. Mick clocked in at 39kph accelerating through a turn on a smallish wave.

http://www.surfertoday.com/videos/5125-analyzing-maximum-speed-in-surfing

71

here is the metric conversion.

 

1km = 0.6214 mile

 

so 39 km/hr = 24.2 mph.. which i think is absolutely hualing @$$ on a surfboard

also 1 mile = 1.609 km

1 m = 1.094 yds or

          39.37 in or

          3.280 feet

1 yd = .9144 m

1 foot = .3047 m

72

Howzit, guys!

This forum is getting VERRRY interesting! Thanks to all who have contributed.

Now, thanks in particular to the the link to the video provided by "JohnnyK3", I finally have what I've been searching for: a 'synchronized' video with the so-called "speed" measurement of a surfer on a decent wave, showing not only WHERE he was on the wave, but, more importantly, what he was DOING at the moment the highest 'speed' was recorded! Now I can finally do some calculations, and draw some conclusions. Oh, HAPPY DAY!

The particular video I'm referring to is of Kelly Slater and Mick Fanning at the 2011 "Quiky Pro", dated Tuesday, 01 March 2011, 15:04

See at:

http://www.surfertoday.com/videos/5125-analyzing-maximum-speed-in-surfing

 

The Kelly slater ride of interest was from about 2:10 to 3:00 in the video, and his hard roundhouse cutback at 2:40 produced the highest so-called 'speed' of the ride of 32 KM/hr.

The Mick Fanning ride from about 3:30 to 4:25 had its highest 'speed' of 39.1 KM/hr recorded at 4:10, ALSO during a hard cutback.

I'll get to the calculations in a moment, but first I have some comments to make on these results:

I've studied Physics and learned math up to Calculus. While in college, I studied to be an Aeronautical Engineer, and was interested in hotrods and dragboats in the '50s and '60s mostly. I analyzed drag-racing performance when I was a hotrodder. I came to Hawaii in 1969 to design and test kneeboard and bellyboard designs.

The fact that the surfboard 'speeds', as measured by the devices in use up to now, seem to be recording the highest 'speed' values during bottom turns and cutbacks or snapbacks, suggests to me that maybe the onboard accelerometers are being fooled or confused by the high-g maneuvers performed on the wave. They are really only measuring Acceleration, which is integrated with very small time intervals to yield the equivalent 'Speed'.

Only problem is: the high-g turns produce acceleration that is acting is at Right Angles to the forward motion of the surfboard. It is caused by the 'Centripetal Force" produced by the water 'pushing' back on the board during high angles of attack, which produces the necessary 'Lift" required to balance the Centrifugal Force generated by the turn.

So, the Integration of Instantaneous Acceleration acting over tiny Intervals of Time, does NOT give you the FORWARD SPEED of the board. Only FORWARD ACCELERATIONS can give you the Speed! When does 'Forward Acceleration' reach its highest value? Certainly NOT during a turn or banging-off-the-lip!

Think about it: Is an airplane going fastest during a high-g turn, when the angle of attack of the wings is highest, and the Induced Drag (caused by Lift) is highest? How about a race car in the turns, or a speed skater in the turns? No, the highest speed is attained on a racetrack near the end of the straightaway, before you apply the brakes and slow for the turn.

The surfer on a wave goes fastest at the end of a descent from up high on the wave, 'diving' to gain enough speed to make that fast section that's approaching. That's called "Energy Management". Think Roller Coaster, or Bob Hoover in an airshow with his Shrike, both engines shut down, props feathered. After a series of aerial stunts (rolls, loops, etc), he makes a 'dead-stick' landing, then he finally rolls to a slow, gradual stop in front of the announcer's stand, without ever touching his brakes!

Anyway, in the video of Mick and Kelly, I was particularly interested in estimating the wave heights at the point where the surfer was trimming at his most likely highest straight-line speed.

Taking the Mick Fanning ride at about 3:50, the wave looked like anywhere from 1 1/2 to 2 1/2 feet over his head, while he was in a semi-crouch. My guess is that he was around 4 ft tall on his board at that point. How far above the bottom of the wave was his board at that moment? It's hard to pinpoint where the lowest point of the trough is, based on a photograph looking straight-on, toward the wave, but it looks like the trough is at least a foot below his board's position.

OK...If the total wave height is 1 ft + 4 feet + 1.5 to 2.5 feet, that's about 6.5 to 7.5 ft. But the bottom of the trough is usually well out in front of a wave, not so close as the above example appears to show. If I use the part of the wave that was highest above his head, then the wave is 6.5 ft above his surfboard. The true total height of the wave, then could be 6.5 ft PLUS the distance down to the true bottom of the wave, in the trough. Another 1.5 ft or so would make it a true 8 ft wave, 'top-to-bottom'.

My own studies and ACTUAL measurements of MANY waves in Hawaii, shows that the trough is anywhere from about 1/7th to 1/5th of the total height. Severe suck-out waves like Teahupoo in Tahiti probably have a "Pit" as much as 1/4th of the entire wave!

If I use the typical wave in Hawaii for an example of a 'good' surfing wave, then the typical trough seems to be about 1/6th of the entire wave height. So, a true 6 ft wave has a trough of about 1 foot, leaving about 5 feet Above Sea Level. That's about 1.5 meters, or 3 'Half-Meters", the so-called "Local Scale".

Then, the total height of a decent wave is about 6/5ths, or 1.2 times, the apparent height of the wave (to a surfer's eyes) NOT including the trough.

But, the total height of a 'juicy' wave might be somewhere between 1.2 and 1.25 times the height of the wave 'without the trough'.

So, tell me, guys: does that Fanning wave look like it could be around 6 1/2 ft or 2 meters, say at his position on the wave when it was largest? If you add another 1 1/2 ft (or a half-meter) to that, you'd be looking at a true, TOTAL wave height of around 8 ft, or 2.5 meters.

My Maximum Surfer Speed (GPS, or 'over-the-bottom' speed) is given by:

Vmax,mph = 7 x SQRT(Hb, ft)   = 7 x SQRT(8ft)   = 19.79898987 MPH

Vft/sec = (22/15) x Vmph   = 29.03851848 ft/sec

Vm/s = 0.3048 x Vft/sec   = 8.850940433 m/s

Vkm/hr = 3.6 x Vm/s        = 31.86338556 Km/hr

 That's almost 32 Km/hr

 

But, if I use the metric system, if the wave total height is 8 meters:

Vmax, Km/hr = 20.40513366 x SQRT(Hb, m):

Vmax, Km/hr = 20.40513366 x SQRT(2.5m)   = 32.26334916 Km/hr

A little over 32 Km/hr.

 

Well, that's about what Kelly Slater got on HIS waves (32 KM/hr). Mick Fanning was timed at a max of 39.1 KM/hr during a VERY hard cutback (seen at 4:10 in his ride), where he banked his board up at a very steep 70-80 degrees, probably 'pulling' about 3-6 g's in that moment. Maybe he's actually the "Snapback Champ"? Pulls the highest g's! Ha!

I saw George Greenough do stuff like that at Rincon back in the mid-'60s, when everyone else was trying to 'hang ten" and going in a boring straight line on 10 or 12 ft waves. George showed me the stress cracks on the bottom of his 'spoon' kneeboard from the 6-g turns he liked to perform on those 600-yard rides. He went faster than anybody else out there!

I think if any surfer ever gets on a True 100 ft wave, my formula says the maximum makeable speed is about 70 MPH. But, if he is limited by air drag (relative wind, in his face) to only going 50 MPH, then the fastest peeling wave that he could make might be a Peel Angle of only 29 or 30 degrees away from straight off.

Did any of you guys see that video of the big wave surfer who got towed into a wave while riding modified WATER SKIS? Wierd...

Aloha!

73

Larry,  Your above post #73, is bang on!     As a licensed pilot since 1966, your aeronautical examples were especially clear.    In large Hawaiian waves, there is a lot of surfable slope in front of a breaking wave.    Many’s the time I’ve surf right around a closout section by running on that slope, and then coming back up into the wave face.   The only significant finding, for me, is the speed over the water!    The speed and G forces generated by waves on the North Shore, were mind blowing when I first experienced them.   The speed sensation was fantastic.    Surely we had to be going 45 mph, or more.  Not so.   Our actual speeds were about 60% of that, as measured by Bob Shepard, with his ‘‘speedometer board.’’

74

Hi, Bill...always good to hear your comments.

I only flew lightplanes and sailplanes, in the '50s and '60s. After I came to Hawaii, I got a little 'stick time' in the '70s (Piper Arrow, Cherokee 6), until the 1974 Oil Embargo made the gas prices go way high (a dollar a gallon...ha!). Only flew with friends once in a while after that. I got my friend Buzzy Trent into hanggliders in the mid-late '70s. I couldn't even afford an Ultralight THESE days! (sigh...)

You mentioned Bob Shepard's boat speedometer-equipped surfboard. If the waves at Sunset really were actually 15 ft, (TRUE total height), then my Maximum Surfer Speed (GPS, over the bottom) formula says that:

Vmax, mph = 7 x SQRT(Hb, ft)   = 7 x SQRT(15)   = 27.11088342 MPH

If Hb = 16 ft, then Vmax = 28 MPH

But, he measured 27-28 MPH ACROSS THE WATER, i.e., "Vcurl",  not GPS Speed or Vsurfer!

So, what was his likely actual speed 'Over the Bottom' (GPS Surfer Speed, or "Vsurfer")?

Vcurl / Vsurfer = COS P,        where P is the Peel Angle, 38.65980825 degrees

so,

Vcurl (over Water) = Vsurfer (over Bottom) x COS P

and,

Vsurfer = Vcurl / COS P

My formula says P = 38.65980825 degrees, so...

COS 38.65980825 degrees = 0.780868809

1/COS P = 1.280624847

Thus, if Vcurl = 27 MPH, Vsurfer = 27 / COS P   = 34.57587088 MPH

and, if Vcurl = 28 MPH,  Vsurfer = 28 / COS P   = 35.85749573 MPH    = GPS speed

If you just round it off to around 35 MPH, then the true height was about 25 ft.

The waves would've been breaking in about 32 feet of water, and the breaking wave height would be about 25 ft. So, Bob Shepard was reporting about 60% of the true height...typical of surfers in Hawaii. Generally, in Hawaii, they report about 50-70% of actual heights.

I'm burned out...guess I'll call it a day.

Thanks to all you guys, we're finally getting closer to finding the answer to the vexing question: Just how fast ARE we really going?

 But, it looks like it will be a while before we'll be able to figure out: How fast CAN we go?

Hmmm...                        Aloha!

 

75

      Howzit Keith, Back in my youg days when I waterskied I was in to speed sking and topped out at 95 MPH since my brother and his brother in law built speed monster inboards that would go over 100MPH. I fell more than once and I remember sliding along the top of the water and just dreading when I would slow down and catch a part of my body or any other part and then start tumbling till I would finally stop but I usually went about 100-200 ft before that would happen. But in the end that didn't even come near to the great feeling of surfing. Aloha,Kokua

76

Bump.

Mercedes Benz made Garret a board - http://www.youtube.com/watch?v=zL90RIIa0vs

They’re claiming a top speed of 62.4 kph / 38.8 mph at Nazaré

I bet they’re fairly accurate. 

 

77

Aloha Kendall,

Glad you dug this thread out of the archives.     It has a great depth of information, and should be required reading for all forum members.    Sadly, MTB(Terry Hendricks) is no longer with us.    His contributions should be preserved (sticky?) for the benefit of future members, as well a re-read by current members.

Bill

78

Hi Bill T,  I start reading redux threads from page one so I get all the info, and on page one there’s a comment by Terry Hendricks, and it made me stop.

 And think that he’s not here anymore, or anywhere, just gone.

 There’s something wrong with life when good people disappear.

79

I just browsed this thread and skimmed some of the entries. Much of it is way over my math impaired brain.

Am I correct in guessing that “mtb” was Terry Hendricks? Also, who is LarryG ? He looks very familiar.

80

Yes.   He was a regular fixture, at Windansea, through the 60’s.      Had many a chat with him in the parking lot, after surfing.