What's the smallest wave you can surf downwind?

3 weeks 6 days ago - 3 weeks 6 days ago #30385 by HangTen
I'm relatively new to surfski, so interested in hearing the theory and techniques for small waves because it seems like all the downwind videos are more focused on the big ocean swell downwinds which you only get close to in my area the day before or after big storms. Is there a minimum size? Or minimum distance between the crests?

I feel like the distance between the crests is what is important to actually surf, ie. you're paddling downhill vs. flat or up, although I suppose even if the waves are so close together that you're not surfing that the small waves are pushing you?

In the attached A is when you have great downwind conditions and you're just grinning ear to ear because you're surfing.

But in B situations where your boat doesn't really fit between waves to be "downhill", just from my experience I match the wave speed and then steer to angle immediately so it will "fit" as shown in C from a top down view.



Also, when people refer to "runners" are those the small waves in B or are they the really fast running waves you see compounded underneath the slower moving waves that you need to link up off the slower waves to have any chance of catching? I feel like I've seen it used in both contexts.
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3 weeks 6 days ago #30390 by AR_convert
Good post and why shorter skis will be more popular is parts of the world where you are likely to be only getting the short period wind driven waves in B and C.

As you've pointed out, often you cant fit the longer skis down the wave so you must be going one way or the other.

I'm lazy and prefer to paddle down wind that only has localised wind generated waves and no swell (protected inshore waters, estuary's etc) Lot less technical and for me at least, more fun.

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3 weeks 6 days ago #30391 by kwolfe
I live inland so the only waves I get are wind generated on the largest lake I paddle. They can get up to 3ft but they are really close together. This is where have an 18ft ski is definitely better than a 21ft ski. It may not track quite as straight upwind, but it catches far more waves.

Last time I was on my Nelo 550 and was still burying the nose in the wave in front of me, however if I was in my old SEL, I would have completely bridged the two.
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3 weeks 6 days ago #30394 by HangTen
So would you say under 2 feet you don't bother surfing?

I'm curious what the threshold is for most people and especially the pros between just paddling straight and hard like it was flat(or maybe that is what they refer to as flat) vs. looking to constantly put it in the "hole" when you have small wind generated chop, or maybe it's just second nature to them where they are just intuitively rather than a conscious distinction trying to get every micro speed boost/energy saving by always paddling as downhill as possible? I'm wondering if it's that lack of experience and expert technique to link the smallest wind generated waves but I feel like with the smaller wind generated waves any gains from surfing them might be wiped out or maybe even net negative as compared to just pulling hard and straight.

Any thoughts on the standard definition for "runners"? Maybe Robin can put together a glossary section?

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3 weeks 6 days ago #30396 by LakeMan
I'm also inland so the only waves I ride are from following the occasional boat. In my local lake they only allow 10hp crafts but even though they create only small swell I can still ride them. Lots of fun. The chop during afternoon pop-up storms are not fun. It's impossible to ride them and they toss you around like a matchstick in a hurricane at sea (and I never exaggerate).

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3 weeks 6 days ago #30398 by kwolfe
2 ft is totally ridable. I raced my OC1 earlier this year on the Potomac river in DC. On the way back, I caught a 2ft reflecting boat wake that took me 30ft from the guy that was riding my wash. He didn't see and missed it. Fun little ride for sure.

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3 weeks 6 days ago #30402 by Newbflat
Wave hight is a strange thing. It seems to me that 3 feet to one person is about a foot to another. I can happily surf 1 foot waves if developed over reasonable fetch so they have good length. The way I see it, honest 3’ waves are way more than enough to surf and no one anywhere would complane having them. . In 3 foot/1 meter waves, they are head hight if you are sitting in the trough. If you were in the trough and someone else was in another trough, you couldn’t see them. 2’ waves are shoulder hight and good solid fun and 1 foot surfable but slow. It always seems to me wave length has more to do with it than hight.

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3 weeks 6 days ago - 3 weeks 6 days ago #30404 by HangTen
Newbflat, sorry, I should've clarified. I believe wave height is measured from crest to trough.

What you're describing as "honest 3'" waves are 6 foot wave conditions. So when you say 1 foot wave I believe you're referring to 2 foot wave conditions as the smallest that you would surf.

I am not an expert on fluid dynamics, but I believe like deep ocean swells from tidal and seismic activity interacting with the seabed tend to be the longer waves(can be small or large in height) as measured in distance between crests, whereas the surface wind driven waves(which can also get large around and during storms) tend to be shorter in distance and then you have boat driven wakes which are very uniform and typically very surfable regardless of size.

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3 weeks 6 days ago #30407 by Newbflat
What I’m refusing to as a 3 foot/ 1 meter wave is head hight while sitting in your ski. If you sit on the ground and put yard stick or meter stick next to you, it more or less comes to the top of your head. To me, if I’m in a ski and in the bottom of the trough a 3 foot wave it at the top of my head hight. Someone in the same conditions also in the bottom of the trough one or three ahead would not be visible as my eyes would be below the top of the waves. It rarely occurs because we are usually higher on the waves than that and rarely time it with the other paddler. A 6 foot or 2 meter wave would be double over head.... I’m talking while sitting In a ski, not standing. A 1 foot wave with a lot of fetch/ time to propagate will have a longer wavelength than one developed by higher wind speeds over a shorter fetch. The info I was looking at says 12 mph over 12 miles will develop a .9 foot wave with a wavelength of 28 feet... more than enough to surf. Also larger dying waves dropping to a foot or so often have quite long wavelengths and can be fast. Totally surfable but a lot of work and very fast.

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3 weeks 5 days ago - 3 weeks 5 days ago #30409 by HangTen
Ahhhh, Newbflat, I misread your earlier post. So what is the smallest wave you surf vs. just paddle?

As an aside, do you have a link to the info that you were looking at? And do you know the formula for calculating height and distance from the windspeed and fetch? If you're referring to the chart for nominal characteristics of fully developed seas, at least in my area I don't think I've ever seen a 1 foot wave with a 28 ft length, but that might have to do with the fact that it would require 12 miles of uninterrupted water for the wind to fully propagate over.

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3 weeks 5 days ago #30424 by Newbflat
I can’t find the same chart I found befor but Wikipedia has similar info. en.m.wikipedia.org/wiki/Wind_wave

I surf what ever I can’t paddle over... so it depends on how fit, and lazy I am.

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3 weeks 5 days ago #30426 by Kiwi Dave
Plenty of online wave calculators out there .. here is one to play with:
woodshole.er.usgs.gov/project-pages/coas...s/fetch_limited.html
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3 weeks 4 days ago #30432 by HangTen
Thanks Kiwi Dave,

I had already played around with that one, but it doesn't return the wave length so was hoping there was a formula.

Any idea how to calculate the wavelength from the height and period that calculator spits out?

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2 weeks 6 days ago #30496 by davgdavg
What people in this thread are referring to as wave length is much more commonly known as "period" or interval when talking about waves and is measured in seconds. That's the seconds it takes between two peaks pass a point. Usually under 10 seconds is windswell and greater is called groundswell.

Swell periods are dependent on the fetch and wind strength. The longer the distance the wind blows and stronger it blows, the longer the period. The speed of the waves increases proportionally with the period.

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2 weeks 5 days ago #30514 by HangTen
Davg,
Thanks for the reply and information on the groundswell/windswell, would you happen to have formulas?

Wavelength is actually not commonly known as period. As you described period is the time between two peaks, wavelength is the distance. You could have different waves of the same period but with very different wavelengths because unlike they have different speeds unlike sound/light that are constant.

Wave speed would be inversely proportionate to period for a given wavelength, not increasing proportionally. I'm interested in understanding the resultant waves from less than maximum fetch.

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2 weeks 5 days ago - 1 week 6 days ago #30520 by davgdavg
HangTen,

1) I said "what people are referring to in this thread as wavelength," not what the actual definition of wave length is.I don't mean to insult you so please don't take it as more than it is, but you don't seem to have a good grasp of wavelength to begin with.. I will explain now,

2) Sound is not constant. It depends on the medium through which it travels and density, etc. Light is more constant, but also has shown to show variations through different mediums, it is constant through a vacuum.

3) Waves of the same period have the same distance between them until they begin to "feel" the bottom, in which case they compress together as they slow in speed.

What you are referring to in terms of size is "amplitude," which we measure in meters or feet, etc. This is a totally separate thing.

4) A greater period is directly proportional to increased speed. It just is with with waves, sorry. A ground swell at 2 feet and 25 seconds travels a heck of a lot faster than 2ft at 5 seconds. What you may be thinking is that in physics and electromagnetic waves, a decrease in wavelength shorter (and corresponding increase in frequency, another term out of place in a wave discussion) means an increase in the energy of the wave (light or gamma or whatever). As I've already said, this doesn't apply to waves and is something totally different.

As applies to surfski, the ideal is to use the smaller windswell to slingshot into the faster moving groundswell. The groundswell is always much less steep, so mostly it rolls by, but it does give a significant increase in speed.

Ill try to find the calculators tomorrow.

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2 weeks 5 days ago #30524 by HangTen
Davg,
What was being referred to in this thread as wavelength is wavelength. When people in surfing refer to period, they aren't referring to wavelength. For a fully developed wave with maximal fetch the two correlate, but they are not the same. Where I normally paddle the fetch is hard capped out, which is why I'm interested in better understanding the wave propagation in limited fetch.

Yes, you are correct that sound and light are not universally constant depending on the medium. But when people speak of the speed of sound or light they are referring to the speed through a given medium as a constant. Ocean waves on the other hand, have very different speeds from each other, period.

Ocean waves of the same period do not have the same distance between them; as I explained earlier unless the waves are all fully developed the period and wavelength are not correlated, you can have waves of the same period with very different lengths/speed.

Again, I am not referring to amplitude, because the amplitude, wavelength, and period are all very different things.

In any case, if there is an expert in fluid mechanics(I am not), that can direct me to the formula for non-fully developed waves of submaximal fetch, many many thanks. If not, no worries, more just a point of small curiosity tangential to the topic.


Davg, what's the smallest wave you bother surfing vs just paddling? Standard definition of runner?

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2 weeks 5 days ago - 1 week 6 days ago #30525 by davgdavg
HangTen,

Ok, if that's your opinion, fine, everyone is entitled to their opinions, no matter how scientifically incorrect. Some people think the world is flat, fine, great. But in the world of the ocean its period, wave height, and wave steepness. Those are the measurements because that it what is important and relates the necessary information. End of story.

You keep using terms in your posts that seem to indicate you have absolutely no idea what you are talking about. "Maximal fetch?" "Submaximal Fetch?" Really, please just stop. As they say here, "maybe try listen."

"Wavelength" is a meaningless measurement in the ocean, and even moreso because the small windswell experienced in the ocean, on a surfski is highly irregular and not ordered, so where one wave breaks is not directly in front of the other. I am sort of wondering if you are not just trolling here and don't even paddle.

Anyhow, the smallest wave that I paddle depends on how fast I am trying to go. If I'm sprinting, then I may try and paddle through smaller waves. If I'm cruising I'll stop paddling when a wave picks me up at whatever pace I'm going. Or a combo of cruising on the small ones and pushing it to get onto a big one.
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2 weeks 5 days ago #30527 by HangTen
Davg,
To say period, wavelength, and amplitude refer to the same thing in any permutation is scientifically incorrect, not opinion or some tin foil hat conspiracy theory.

I am not an expert in fluid mechanics, but even I know that there is a maximum fetch after which no additional fetch will increase the wavelength/period/amplitude of the wave ie. fully developed; any additional energy just creates whitecapping, hence submaximal when the fetch is hard capped by land mass.

If you are an expert in fluid mechanics, provide the formula or let it go.

Thanks for your reply to my original question. Any thoughts on the standard definition of runner?

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2 weeks 5 days ago - 1 week 6 days ago #30528 by davgdavg
I never said anything of the sort about period, wavelength, or amplitude.

Seriously, nothing even close.

The ideas you are expressing in your concept of the ocean and waves are just wrong.
Honestly, each one of your posts in this thread has been so incredibly wrong that I am amazed you haven't at least googled it to figure out you don't know what you are talking about.

Hopefully someone else will chime in if you still want to try, because I'm tired of trying to argue against nonsense, not reading, and misquotes.

My definition of a runner would be a wave that will carry the ski/paddler at a sustained speed for at least two boat lengths, but that's a totally arbitrary idea if I had to define it.

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