Re: 68.8km/h on a Double Ski

A mate showed me this yeterday, I didn't belive him till I saw it.

"Tropical Cyclone 'IRINA' hit Durban 4th March 2012.

Barry And Mark Lewin went out on a double surfski and rode swells on the mound getting to 68.8km/h recorded on Barry's Garmin Forrunner 310xt.

All the footage was shot on the Hero 2 by GoPro and edited by White Hot Media. Check out the full story on www.barrylewin.co.za"

First up - Barry and his mate have balls of steel, clearly.

They are undoubtedly moving at a super pace - but nearly 70kmh?

The rest of their GPS read has a few tipping 50kmh, which is also a lunatic speed.

So either that first wave was akin to the tsunami that took out Japan, or the read out is flawed.

Again, they're tackling monster conditions in double and look like they're doing it with ease, but in discussion with some much more experienced paddlers than me, the consensus was at 70kmh, the paddles would get ripped out of your hands if you tried to put them through the surface of the water.

I've often had random numbers come off a 310XT, particularly near the start of paddles, that don't seem to relate to what actually happened on the water,

But hey, I'm keen to see them crack the ton if the data is right!

I wouldn't necessarily believe it because it is on youtube. Unless you are a total beginner, it is always very difficult to set a new personal best that doubles your previous record (as Barry Lewin wrote in the blog).

GPS errors or dropouts that skew results are not unusual. So take readouts with a dose of skepticism when they don't make sense, even your own. According to my Garmin 705 and Powertap, I put out 5000W on a climb yesterday! I use a program to fix incorrect GPS data, recording dropouts, or power spikes automatically.

Maybe they got close to 40km, which would already be an amazing ride.

I've seen a couple of skis beat 60km/hr ... both on roof racks with photographic documentation from local law enforcement!

I love some controversy.

They are certainly going very fast, that spray comming off the boat is not a result of increasing the frame rate!

I can believe this, although I would have been hard pressed to a month ago.
I was paddling with a mate and we both took separate lines, him closer to shore, me, the deeper, more direct line, lined up with the swell.

I stopped frequently to try and see where he was as I new he was a bit nervous about conditions.
I was the better part of a kilometre further out on a great line, but only caught glimpses every now and again when I stopped to do so.

There was quite a large groundswell coming over my left shoulder but I was following the windswell that was headed my way.

I decided that it was better if we paddled together so I headed over his way, lining me up perfectly with the groundswell.

These were quite a long period and I didn't think that it possible to catch them, but a good try teased me enough to have another go.
I briefly caught it, but couldn't get down the face and then fell off the back, but that was all I needed to encourage me.

I paddled flat out to get as much speed up as possible and assisted by a bit of the wind driven swell, felt the boat lift and I new I had it.

It steepened considerably to the point that I was perched on top and could see the water about me and in the dip, but the face was steep enough to be hidden from my view.

As the nose started to drop it looked awfully vertical and I had visions of Oscar and Dawid's millars run.

I nearly backed out right there and then, but put the one last paddle stroke in to pull onto the wave.

It was fast and it was bouncy, but this one wave took me most of the way in to my partner.

I never looked at the GPS as I was just looking to keep myself out of trouble.

When I got home, I had a maximum speed of 49km/h.
First thing I did was look to see if I left it on and caught me driving home.
Nup.
Then I thought it may has lost positioning when the boat was upside down as it had before, but then remembered that I never took a swim.

The final teller was looking at the data and seeing three peaks,
the first 28km/h, the second 39km/h and the last 49km/h.




But 68km/h is dammed impressive.

I was sceptical on this, the Forerunners are known to spit out odd data at time and I didn't do the analysis but check out these threads on the same topic.

www.seakayakforum.com/viewtopic.php?f=31&t=1662

I followed the various links until I came to their published speed and track data on Garmin Connect at

connect.garmin.com/modern/activity/155120476

The 60+ kmh spike is at the beginning of the day, while turning from an along-shore plod to go out through the surf. The high speed reading is while turning. If you understand how the GPS takes and records a trackpoint, you will immediately see that this is an error. It's probably not that the GPS reads the satellites incorrectly, but that while reducing the data to fit into track memory, it has wrongly recorded the point of the turn (where it has to compress many satellite readings on a curve to one or two readings in memory at right angles). Another two high speed readings, one at 50.4 and one at 37.2 also occur at corners, at moments when they obviously are not running a wave.

On the positive side, there is another run, peaking instantaneously at 37.7, which is on a corner, but clearly heading towards shore. This is a plausible situation, where they might have just picked up a wave long enough to get a push, then drop off the back as it rolls under.

The real gems are the two long runs, at 30 to 32 kmh, going for 40 or 50 seconds. That's runs of around 400 metres. Mind-boggling! I'm sure those are the runs on the video. The fantastic thing about a ski (especially a double) is that it has the hull speed to allow it to stay on a swell wave, whereas a sea kayak might get that speed for a moment, then bog down with hull resistance and have to let the wave roll under, even under sail power.



So basically, BS.

Thanks Greg for busting my balloon. You didn't have to be so dammmed harsh, didya? Oh well, the vid was fun.
I've done 120 mph on my speed skates screaming up and down hills, and 30+ mph in the ski, in kinda-rough water, several times in fact. I'm sure you'll debunk those too if you find my record breaking runs on Garmin.com. Again, thanks Greg.

I wouldn't be so easy to disregard this as fiction or mistake. RAB on a single got 50kph on a day with a big groundswell. Oscar posted his fastest recorded time on the Epic site as 54 (odd?) kph. In the light of those 2 alone I cannot see an increase in speed from 50's to top end 60's as impossible. If anything I would say the fact that RAB and O boasts upward of 50 on a single corroborates the probability Barry with his old man screamed down those faces at much higher speeds. Maybe they could enter the stage and explain your observation of the 68kph measured at the start (and then obviously a bug in the German).

Battling a bit with your basis point that the Garmin 'wrongly recorded the point of the turn' on 3 occasions (that records the three higher speeds). Does the garmin's recording of a gradual acceleration to a peak followed by a deceleration not indicate a true recording (and what one would expect of surfing a wave)? And if you assume a mistake you discard that the mistake could be with the actual location of the speeds on the map? The video shows breakneck speeds. 38kph - nope!

Any HI guys to hit Jaws in a double and see what they record from top to bottom? Send Rob M and Dale L out at Dungeons, RAB and Sven out to Shipsterns and see what speeds they get?

Who could disagree with people who can paddle at speeds of over 40km/h, I bet they do that even into the wind....

But since we look for records, no need to be stuck in the double digits. Here is somebody clocking more than 150,000 mph while skating through London. Now that's a real athletic feat (and since it was measured by GPS and is posted on the internet, it must be true):
connect.garmin.com/activity/36503221

Now that I look at the Garmin track, it does seem suspicious. Look at the video - the fast runs are towards shore (makes sense - the large waves are traveling towards shore). But on the track, the top speed is during travel away from shore or in some random direction/turn.

Something is not right with the data. The only good runs seem to be as Greg suggests, the rest seems fishy to me. Fast, yes but how fast I don't think we can tell from the GPS with certainty. Some of the super high speeds were also recorded going against the waves, some in the opposite direction, so not sure what's going on there ...

Also, looking at the video again, it seems they had to put a few paddle strokes to the water at various times. The cadence did not seem to correspond to a speed of 60+ km/h for sure - it was not even frantic looking, and the spray when they were not paddling is not that different from the spray when paddling... Although the second drop looked steeper and they did not paddle - that might have been the fastest or at least it looked the most hecktic !!!

Nice runs though, regardless of how fast it was actually

I'm sure the Lewin's had a feeling, after reviewing their own data, that the speeds were just a bit "out there" and corrupted in favor of the fantastic. But still, it sure got a lot of hits from us, and I don't feel slighted in the least. Great vid!

Good work Greg. I didn't play their data before you pointed out that it was accessible.

With tghe top speed going out to sea I can see that this isn't a valid sea speed run.

None-the-less, they were really hiking down those faces, that would be adrenaline producing for me!

So after all this do we have a reasonably recognised max spee for doubles and singles?

Just to clarify, the earlier post is linked to the person that did the work, not me, don't give me the credit, I'm just passing it on.

Only the first sentence and the basically BS bit is mine.

Forgetting the spikes the Garmin products can throw up ...I really enjoyed the sense of speed the good quality video and production showed us, also the sound of the water rushing by gave an idea of the speed at which these guys were going, great stuff !!!

In deep water, waves with a period of 10 seconds, travel at 56 km/hr with a wave length of about 156m. A 60 knot (110 km/hr) gale can produce in 24 hours waves with periods of 17 seconds and wave lengths of 450m. Such waves travel close to the wind's speed (97 km/hr). A tsunami travelling at 200 m/s has a wave period of 128 s, and a wave length of 25,600 m.

The period of waves is easy to measure using a stopwatch, whereas wave length and speed are not.

A 12 second swell in deep water travels at about 20m/s or 72 km/hr.
When the 12s swell enters 10m shallow water, its speed will halve to 10m/s and so will its wave length. But the height of the wave increases by a similar factor.

We typically have 10s wave periods at the breaks here on the Gold Coast.
Further out they approach 20s. Most are simply too fat and our boats too hard to accelerate to catch.
Most often seen speeds coming in through the break are between 20 and 30km/h.
Although when it is small they may be well below this.

For those that are interested:



For deep water, the relationship between speed and wavelength is given by the formula:

l = g x t x t / (2 x pi)
l = t x c for all kinds of waves, substitute in above equation: t x c = g x t x t / (2 x pi)
c = g x t / (2 x pi) or t = c x 2 x pi / g or t = c x 0.641 (s)
where t= wave period (sec), f= wave frequency, l= wave length (m) and pi=3.1415...
to calculate c and l from wave period t (in sec): c = t x 1.56 m/s= t x 5.62 km/hr = t x 3.0 knot
l = 1.56 x t x t (metres)

Thus waves with a period of 10 seconds, travel at 56 km/h.





Don't blame me if it doesn't add up, pretty much shameless cut and paste.

Shit RAB , all that algebra and complicated stuff , how come you couldn't figure why you boat slows down when it's full of water?(re One for the thinkers)

Because I was trying to figure out if the small amount of water left by the bailer that was free to slosh around really did impact on speed to a significant degree.
Still haven't tested to see yet.


The high speeds in the above data whilst turning, may have been the bucket swamping with the GPS on the footstrap and therefore loosing GPS signal.

RAB, are you seriously claiming a 49kmph run?


Share the Garmin file, would love to see it.