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What is the problem with too much current at Maryhill?
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biffmalibu



Joined: 30 May 2008
Posts: 541

PostPosted: Sun Jun 04, 2017 12:57 pm    Post subject: Reply with quote

OK, it can be interesting to understand (or try to understand) the underlying reasons why. But I am pretty sure the average Joe/Jane these days wants simpler answers. Thanks for the physical explanations; I glossed over them with glossed-over eyes.

I remember when windsurfing got simple. And it was partly responsible for the explosion in popularity. The best example I can think of was the Chinook clamp-on boom, Classic head. So simple, compared to the tie-on boom! I think this helped increase accessibility and popularity of windsurfing in the late-80s/early-90s.

When sports become "dweebified", only the dweebs appreciate and consume. The rest of the people (most of the people) can get alienated and lose interest as a consequence. Another sport that has gotten dweebified is road biking.
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scottwerden



Joined: 11 Jul 1999
Posts: 302

PostPosted: Sun Jun 04, 2017 1:20 pm    Post subject: Reply with quote

windfind wrote:

Hi Gang,

It is a mistake to assume a water column moving in the rivers current is a homogenous mass moving the same direction/speed.

The first 2 images below show that when there is swell you have some complex and opposing movement patterns in the water column. So one part of a submerged rig can be carried the opposite direction than the deeper parts of the rig and board.


Mike, I think your observation that the horizontal flow is not vertically uniform is correct, but not exactly for the reason you illustrated. Those illustrations are of deep ocean waves which propagate in a particular way (circular motion, group velocity = 1/2 phase velocity, energy vector is perpendicular to the wave face). There are dozens of different types of waves that can form, each with unique motions. There are waves types with pure vertical motions and some with pure horizontal motions. It is not likely that the type of wave we get in the Columbia is a deep-water ocean wave type.

One observation about the "waves" in the Columbia is that they do not propagate to any appreciable degree. If they did, then when there are 10-15' waves faces at the Hatch, you would expect to see 10' or so waves breaking on the HR sand bar, but you don't. And if they were the same as ocean waves, they would only depend upon the length of fetch, but as we all know Columbia waves are very dependent upon current and are very local to the fetch.

What we see in the Columbia is more likely standing waves produced by the high current flow over an un-even bottom contour, which the wind then pushes up the river but due to bottom friction they never form into true propagating ocean-style waves and dissipate quickly. In fact they never really qualify as any true linear, harmonic wave at all since the forcing function (the wind and current) must be present at all times.

One other observation - I see the sucking-clue effect in strong ocean currents that flow parallel to the shore and perpendicular to the waves. The current there has different flow at different depths also but in this case it is perpendicular to the waves and actually is worse inside of the impact zone (where I sail at least). Open channel currents are known (hydrodynamically) to have non-uniform flow, so I think this is more a property of the current than the wave environment.
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ldhr



Joined: 10 Apr 2000
Posts: 120

PostPosted: Sun Jun 04, 2017 10:39 pm    Post subject: Reply with quote

If it swells I ride it!
If it doesn't I don't.
How's that for simple?
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knifeonwater



Joined: 25 May 2000
Posts: 51

PostPosted: Mon Jun 05, 2017 10:32 am    Post subject: Reply with quote

This is all fascinating but did anyone actually sail the Maryhill/Rufus stretch yesterday? Wind graph looked epic. Current is definitely a factor in the corridor, but very sailable. Would love to get an honest report.
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stu2



Joined: 28 Dec 2012
Posts: 22

PostPosted: Mon Jun 05, 2017 11:26 am    Post subject: Reply with quote

I sailed The Wall (Marker 41) yesterday from about 12:30 to 2PM. Rigged a 4.2m w/ 81L board and held it down slightly overpowered.

Absolutely no problem staying in place and it was a pretty cool feeling sailing straight downwind while the river carried me upwind. Huge pools of flat glass smooth water on both sides (because of the powerful eddies) made for easy jibes.

Was it epic? No. Was it windsurfing under full sunshine with just a handful of other enthusiasts? Absolutely. So yeah, there is too much current but as long as you are powered up - it's no problem TrainWreck...
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drblanke



Joined: 02 Aug 2006
Posts: 65

PostPosted: Mon Jun 05, 2017 11:54 am    Post subject: Reply with quote

I was at rock island for a couple sessions late morning and then came back in the afternoon for a session. The swell seemed about the same all day--not there all the time but there were some steep ones to ride every once in a while. The current was strong but the wind was filled in all the way across and steady in the morning so no problems staying even with the launch for a few hours. Easy to keep on a plane and you could ride deep downwind without much fear of being steamrolled by a gust. Other folks will have to chime in about in between, but when I came back in the afternoon the wind had jacked up but the gusts were sharper and the lulls were bigger. It worked for a while but then I sank a few times and drifted in at the cove after about 45 minutes. The wind regrouped and was blowing pretty hard when I packed up at 5 PM, but nobody was out. Nice day all and all Smile

knifeonwater wrote:
This is all fascinating but did anyone actually sail the Maryhill/Rufus stretch yesterday? Wind graph looked epic. Current is definitely a factor in the corridor, but very sailable. Would love to get an honest report.
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