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

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...

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.''

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?

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.

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.

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.

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

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

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!

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.''

Bill ThrailkillSHAPER SINCE 1958Hi, 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!

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.

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

Bill ThrailkillSHAPER SINCE 1958Hi 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.

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.

This space reserved to mock trolls

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

Bill ThrailkillSHAPER SINCE 1958## Pages