Foiling is EASY

[Beasho]

Even a monkey can foil!

I am confused.

Even a monkey would keep a hand on the paddle.  This must be a counterfeit.

[Cardiff Sweeper]

What’s the smallest wave (breaking or not) that any of you have caught?




Sent from my iPhone using Tapatalk

[Beasho]

2 to 2 1/2 feet. 

The challenge is more with the period of the wave than the size.  Periodicity is related to the speed of the wave. 

Sources suggest a factor of 1.7X Period = Wave Speed.  Therefore a 10 Second Period wave energy will move at ~ 17 mph, this does slow down as it hits the bottom aka near the beach.

Using this approximation and the fact that it takes ~ 15 mph to get up and fly.  Once you're up you can continue to fly at a lower speed as low as ~ 11 mph (Kai Go Foil @ 180 lbs rider).  With longer period swell >> 12 seconds I have been able to get up, fly off a bump and continue even as the wave moves back over deeper water.  Compare this to 5 ft @ 8 seconds.  I could get up and fly but the wave quickly lost energy down the shoulder and was too slow to continue riding after the initial flight.

From:
http://www.rodndtube.com/surf/info/SwellSpeed.shtml

[kamalino808]

  Monkey see monkey do!

[PonoBill]

Got to be Sam.

[tautologies]

  Monkey see monkey do!

hah. I recognize that wave at pretty much any angle.

[PonoBill]

Beasho, deep water waves move quite a bit faster than that. Cp=1.56T in m/sec so 10-second deep-water waves travel 15.6 meters/second. Multiply by 2.0 to get kts and that's 31.2 kts or by 2.25 to get mph yields 35.1mph. Shallow water wave speed is a function of depth. A 10-second wave feels the bottom at 250 feet and slows very rapidly (fortunately) or we'd all need jetskis to surf. The speed of a wave of ANY period in shallow water is S=sqrt(1.25d) where depth is in meters and S is m/sec. Of course, it takes time for the waves to slow, but even at a deep water break like Mavericks, the longer period waves have been feeling the bottom for quite a while. But the slowing by depth is why both big and small waves seem to be traveling at more or less the same speed. They aren't, the big waves (longer period waves that are jacking more) are still decelerating and stacking more water from the backside, even as they break, whish is why those bastards are so thick. The real calculations are very challenging since you need to know the ocean depth and bottom composition for as far out as the waves of the longest period start having the bottom rotation flattened. But just understanding the phenomenon provides a lot of insight. For example, very long period waves can be refracted as much as 180 degrees, which is why a swell from a funky angle can still provide good surfing if the period is long enough to rotate them in, and it's why a Maliko run on a day when there's not much "groundswell" from the north but the trades have been pushing long period wind swell from the east for a lot of miles can light up the north shore and scare the shit out of you.

There is a shocking amount of variation in the wave speed formulas on the web. It takes some digging to get answers that make sense. I suspect it's just basic errors by the people posting rather than a lack of understanding of a phenomenon that has been studied for centuries. For example, group wave speed (sets) is half the phase speed of individual waves. I've seen the group speed expressed as S=1.56T which would make the speed of an individual 10-second period wave in a set something like 70mph. I doubt that. Most sources say group speed is half of Cp=1.56T, meaning the 10-second set is going to take twice as long to get from the buoy that reported it to your beach if you use an individual wave speed calculation since the group travels at 17mph.

But I digress.

[Tom]

Pono , very  interesting  but a bit  over my head . I  do get  the  concept  though . One of the  reasons  I  like  surf-forecast.com is they predict  wave energy  which  is  displayed  in  kilo Joules .  It's  a  measurement  that  uses wave height  and period to calculate  energy

[Beasho]

Beasho, deep water waves move quite a bit faster than that. Cp=1.56T . . . . . wave speed calculation since the group travels at 17mph.
But I digress.

Agreed but maybe TMI I'm trying to put it in crayon.

<10 Second Period - Slow
> 13 Second Period - Fast
>17  Second Period  - Really Fast

If I had to put a stake in the ground I would use a factor of 1.2 X Period as the wave hits the beach and breaks.  10 Second = 12 mph, 17 second = 20.4 mph as the Wave Faces are breaking in 6 to 30 feet of water. 

This comes from 2 years of TRACE Up measuring wave riding speeds from very slow of 8 mph to blistering fast 30 mph.  The only way to hit 30+ is with a BIG ARSE wave 18++ feet and going down the line, not just running out in front of the wave which after the initial drop may only result in a 20 mph speed. 

Moral of the story:  Foiling is easy in waves that move from 12 to 18 mph.  As speeds get up to 20 mph things get exciting.  Maybe I'm just not good enough.

[surfercook]

That's so cool you are foiling now. I wanna do it too! Always since I first saw it yrs ago when Laird first started. There's a Naish Raptor here in one of the shops w/a foil mount. $2000!

[PonoBill]

This comes from 2 years of TRACE Up measuring wave riding speeds from very slow of 8 mph to blistering fast 30 mph.  The only way to hit 30+ is with a BIG ARSE wave 18++ feet and going down the line, not just running out in front of the wave which after the initial drop may only result in a 20 mph speed. 

Yeah, but no. What's making you go so fast in big-ass long period wave is the energy available. You aren't going straight, you're cutting across the face. In shallow water with any kind of ledge running up to it (in other words, anywhere but Teahupoʻo) even a very big wave isn't going 20 MPH. Put your trace on, go straight, and see what you get (besides coasting out away from the wave, slowing to a stop and getting worked). In a big wave you can hold a tighter angle across the wave. If the wave was going one mph and you held a 90 degree angle across the face your speed would be infinite--or at least approaching the speed of light. The cosine of 90 is 0, but the hypotenuse calculated is undefined (but very, very big) cosine of 89.9 is 0.0017 so 1mph/cos 89.9 degrees is 588mph.

More usefully, if you can hold a 40 degree angle in a big wave going 20mph you're traveling 26 miles per hour (h=20/cos theta) and if you can hold 50 degrees you're going 31.35 mph. More to it of course, dynamic system, blah, blah, but that's the basics.

[Beasho]

Yeah, but no. What's making you go so fast in big-ass long period wave is the energy available. You aren't going straight, you're cutting across the face. . . . .

We are in violent agreement.

Bigger waves move faster, typically because they are created from longer period sources.  Longer period goes faster . . . . The bigger waves also have the power to get you 'down the line.' 

As most waves approach the shore they start to get pathetically slow.  The only way to pick up the pace is to introduce a speed vector at right angles to the wave's progression aka go down the line. 

At some point the drag on the board is too great for the attempted angle off straight and you get sucked up and over the falls.  Like at Teahupo'o or the recent video of Ian Cairns at Kelly Slater's wave pool. 

[Beasho]

Back to the topic at hand:

Foiling is Easy

This guy, Trevor Tunnington, is putting us all to shame.  He claims he's only been foiling for 2 weeks.  If this is even HALF true, and included some boat time, and you have a shred of ego about being a surfer then you have no excuse not to try for a few sessions.

s

[headmount]

Interesting discussion and it shows to some degree the dynamics involved in downwinding, where the waves can be even smaller that 2.5 feet and still push a foiler along quite well.  I saw Dave on a downwinder  (see the video) and he did it for 10 miles

[Piros]

What's changed is these guys are on the right board with the right foil , no R&D needed with good advice . The hard work has been done , the frothers will launch this.