Author Topic: Energy under water  (Read 3047 times)

frenchfoiler

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Energy under water
« on: August 12, 2018, 11:29:12 AM »
We talk a lot about foil and board but I noticed that the power under water is super important.

I live in France and in California

On a same type of wave, same size, I can notice the difference of power between my home break in France and Sano CA.

It is harder to keep flying when I surf in France than in California. I feel way better foiling in California.

Have you noticed this as well ?

PonoBill

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Re: Energy under water
« Reply #1 on: August 12, 2018, 11:54:34 AM »
The energy carried in a wave is a function of both amplitude and period. Longer period waves have more power for a given height. Possibly your waves in France are mostly short period, local wind waves while those you're riding in CA are long period ground swell generated in big storms far away, cleaned up by the long distance they travel into long period waves (short period stuff dies out quickly)
« Last Edit: August 12, 2018, 11:56:30 AM by PonoBill »
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

Califoilia

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Re: Energy under water
« Reply #2 on: August 12, 2018, 12:08:28 PM »
Beasho posted this sometime back that might help as well....

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
Me: 6'1"/185...(2) 5'1" Kings Foil/Wing Boards...7'10 Kings DW Board...9'6" Bob Pearson "Laird Noserider"...14' Lahui Kai "Manta"...8'0" WaveStorm if/when the proning urges still hit.

PonoBill

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Re: Energy under water
« Reply #3 on: August 12, 2018, 01:30:39 PM »
That thumb rule is only true in open water with the bottom more than half the wavelength deep. We downwind on waves traveling at that kind of speed, but rarely surf something like that, for the obvious reason that we are generally surfing breaking waves, which happens when the wave is in water at about 1/20th of the wavelength. Way out where you start seeing the waves form up (peak) the water is about L/2, where you see it break it's L/20 and the wave has generally been slowing rapidly for whatever that distance is. I know Beasho is not confused about this, but that paragraph confuses wave speed with foil speed. No one but a beginner goes straight on a foil--you run out of the wave immediately and stop. You cut across the wave face and your speed is a function of the angle and the wave speed.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

sharksupper

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Re: Energy under water
« Reply #4 on: August 13, 2018, 03:54:54 PM »
I was out today starting at a very low tide and ending with a mid tide.  While it was super low tide the energy in the waves was not enough to keep me going all the way to the shore ~2000ft away.  As the tide came up some, the waves appeared to stay exactly the same, they broke the same and were the same height, but somehow they gained energy (even though the waves were dropping in height according to the forecast).  When the tide came up a couple of feet there was a magic time where I could just foil effortlessly all the way to the shore.  Very strange, I guess it's not all about the height and period, but also local geography/currents and the height/direction of the tide as well which can make for good or bad foiling.

PonoBill

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Re: Energy under water
« Reply #5 on: August 13, 2018, 04:54:55 PM »
I've never really understood the effect of tide on surf breaks. There have been times when I thought I did, but there seems to be more to the result than simply how much water is over a particular reef or sandbar. I know that tide changes the effects of the bottom contour, but as Sharksupper says, an incoming tide seems to add energy, even in an open break, where it seems the current differences should be trivial.

Oh, well. I can live with a lot of mystery. As with most things, the more I learn the less I know.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

sharksupper

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Re: Energy under water
« Reply #6 on: August 13, 2018, 07:07:31 PM »
I don't know jack**** about the waves, I just seem to get lucky once in a while.  I probably get 1/10 really "good" days I go out.  The rest of it is just making the best of what's there.  Most of the time I can't even tell if it's "good" just looking at the waves from the beach! haha

I keep track of all the stats, and when I see what I think is going to be a good repeatable day, it rarely happens!  However, there does seem to be a few wise individuals who have figured it out, they're the ones who are always out there first when it's good... I think maybe my time is better spent watching when those guys go out than looking at the charts   ;D

I wouldn't write off a spot too quickly based on one or two sessions.  I'd give it a chance for a while, maybe the right combination of conditions will come together and it will be good at some point.



Beasho

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Re: Energy under water
« Reply #7 on: August 14, 2018, 06:29:35 AM »
That thumb rule is only true in open water with the bottom more than half the wavelength deep. . . .when the wave is in water at about 1/20th of the wavelength. . .  the water is about L/2, where you see it break it's L/20 . .

Beasho posted this sometime back that might help as well....

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. . .

You guys are making my hair hurt.  I am making my hair hurt.

My latest revelation is that the better I get the crappier the  waves I can foil. I am foiling on waves in the East coast I would have thought to be WAY to putrid to catch in California.  Think 3 ft @ 7 seconds.  On the right point break you get up and you can fly all over the place.

In California I considered 8 seconds much too short to fly.  Not on the East coast.
« Last Edit: August 14, 2018, 06:33:04 AM by Beasho »

PonoBill

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Re: Energy under water
« Reply #8 on: August 14, 2018, 06:34:55 AM »
I think downwind foiling proves that's so. The folks that are good at it are foiling on close to nothing. Not just pumping--foiling.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

SUPeter

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Re: Energy under water
« Reply #9 on: August 14, 2018, 09:03:27 AM »
  Soory, I do not have the Quote thing down. 

Quote from Beasho.

(You guys are making my hair hurt.  I am making my hair hurt.

My latest revelation is that the better I get the crappier the  waves I can foil. I am foiling on waves in the East coast I would have thought to be WAY to putrid to catch in California.  Think 3 ft @ 7 seconds.  On the right point break you get up and you can fly all over the place.

In California I considered 8 seconds much too short to fly.  Not on the East coast.)
[/quote]

Welcome to East coast shit.  That's what we get most of the time.  I think foils will be the tools which turn all that shit into gold.
« Last Edit: August 14, 2018, 09:06:12 AM by SUPeter »

Beasho

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Re: Energy under water
« Reply #10 on: August 14, 2018, 10:31:11 AM »
  Soory, I do not have the Quote thing down. 

Welcome to East coast sh-t.  That's what we get most of the time.  I think foils will be the tools which turn all that sh-t into gold.

Exactly!!!!!

The East coast has NO idea what is coming.

SUPeter

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Re: Energy under water
« Reply #11 on: August 15, 2018, 05:51:28 AM »
Yes, I agree.  These foils are far too efficient and fun to not change wave riding significantly.  A friend of mine spent some time watching you in RI and was very impressed with both the foils and your expertise.  He is on the fence on whether or not to make his own or buying a set.  Either way, this is going to explode, striped bass be damned.  ( almost had dinner for a week when I flew right into a rather large group of them in Maine.
« Last Edit: August 15, 2018, 06:00:01 AM by SUPeter »

Beasho

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Re: Energy under water
« Reply #12 on: August 18, 2018, 07:47:32 AM »
Yes, I agree.  These foils are far too efficient and fun to not change wave riding significantly.  A friend of mine spent some time watching you in RI and was very impressed with both the foils and your expertise. . . . Either way, this is going to explode, striped bass be damned. .

This is both creepy and cool.  Thank you.

I was out again this week in Rhode Island.  4.5 ft @ 7 seconds.  Wind went from light to ~ 10 mph and bothersome then dropped back to ~ 6 mph side onshore SW (The picture below is inverted South on top).  At first I thought I was pushing the limits of what was foilable.  Then I realized I might have been a bit rusty not having foiled for 2 weeks.  I started getting back into the groove.

I ended up rating the session a 6.5 / 10.  I was noting a SLIGHT lack of energy.  My daughter gave it a 7.0 / 10.  First time she has ever rated higher than me, probably because it was the middle of the week and uncrowded.  Set waves were up to shoulder high.  Managed to catch 20+ waves in 1:45 up to 200 yards hitting 16.6 mph.  Check out some of the turns on the inside 120 to 160 degrees.  Full roundhouse cutbacks in MUSHY slow East coast SLOP!

This would all be impossible on any other surf craft.

Quick video of conditions:
https://youtu.be/6e2oAMOYJyY
« Last Edit: August 18, 2018, 08:27:20 AM by Beasho »

Califoilia

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Re: Energy under water
« Reply #13 on: August 18, 2018, 12:57:22 PM »
I was out again this week in Rhode Island.  4.5 ft @ 7 seconds.  Wind went from light to ~ 10 mph and bothersome then dropped back to ~ 6 mph side onshore SW (The picture below is inverted South on top).  At first I thought I was pushing the limits of what was foilable.  Then I realized I might have been a bit rusty not having foiled for 2 weeks.  I started getting back into the groove.

I ended up rating the session a 6.5 / 10.  I was noting a SLIGHT lack of energy.  My daughter gave it a 7.0 / 10.  First time she has ever rated higher than me, probably because it was the middle of the week and uncrowded.  Set waves were up to shoulder high.  Managed to catch 20+ waves in 1:45 up to 200 yards hitting 16.6 mph.  Check out some of the turns on the inside 120 to 160 degrees.  Full roundhouse cutbacks in MUSHY slow East coast SLOP!

This would all be impossible on any other surf craft.

Quick video of conditions:
https://youtu.be/6e2oAMOYJyY
Looks like the average conditions we were having for the most part of the summer here, and yes, very doable on a foil. As long as you can stand to catch a wave you can most definitely foil it. FOILING IS EASY!!  ;) :D
Me: 6'1"/185...(2) 5'1" Kings Foil/Wing Boards...7'10 Kings DW Board...9'6" Bob Pearson "Laird Noserider"...14' Lahui Kai "Manta"...8'0" WaveStorm if/when the proning urges still hit.

 


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