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Search took 0.00 seconds. Search: Posts Made By: Paul Elliott
Forum: Challenges 29-11-2013, 15:06
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

Well, I'm glad we agree on something as fundamental as that.


Yes, but a proof of WHAT?

Dockhead originally posed the question. Seaworthy Lass recently suggested a definition of Lee Bow...
Forum: Challenges 29-11-2013, 14:39
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

If you have the current on your bow, you are being pushed backwards, slowing your forward progress over the ground. The True(*) and Apparent Wind Directions will shift aft ("in increase in the...
Forum: Challenges 29-11-2013, 14:17
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

And so why is this even an issue? What exactly are we arguing about? OF COURSE the apparent wind changes when the boat changes orientation (assuming non-zero wind). And the True (water-referenced)...
Forum: Challenges 29-11-2013, 13:10
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

I am truly dumbfounded by the proposition that since the real world is full of variables then we should not attempt a "first principles" analysis. That's how we begin to understand what is going...
Forum: Challenges 29-11-2013, 09:14
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

Dave, what I think you are describing is the relationship between Ground Wind, Current, and True Wind. If so, what's the debate?

I will suggest that this simple and well-understood relationship...
Forum: Challenges 29-11-2013, 09:09
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

And to clarify a bit further, by "close hauled at your optimal heading with optimal sail trim" I mean sailing the optimum current-adjusted course at your best angle per your polars. This may involve...
Forum: Challenges 29-11-2013, 08:33
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

And is this the Lee-Bow effect we are debating? And this is supposedly to be applied in unchanging (current, wind) conditions?

This has been my understanding of the Lee-Bow effect, and I claim,...
Forum: Challenges 28-11-2013, 19:44
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

Dave, in recent discussions nobody has mixed up the vector references, except possibly you (it was hard to tell, given the terminology problems). And, nobody has disputed that given a fixed Ground...
Forum: Challenges 23-11-2013, 21:11
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

I am perfectly comfortable with whatever credibility I may or may not have, thank you very much. But why don't you go ahead and suggest a particular problem.

Look, the leeway can vary...
Forum: Challenges 22-11-2013, 10:03
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

Exactly! It doesn't matter to me which frame of reference someone uses. What matters is that they use terms that we understand, and that the results are correct.

I prefer using water-referenced...
Forum: Challenges 22-11-2013, 09:45
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

Hoofsmit, if you want to figure leeway, just use 5 degrees on all points of sail, other than (say) within 20 degrees of dead downwind). Use zero for the that.

The only significant difference you...
Forum: Challenges 21-11-2013, 08:05
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

In that case he would be wrong. Are you sure about the motoring speed?

Do you and I agree that if he is motoring 10kts directly into the 5kt current that the Apparent Wind is 10kts (etc)?

And...
Forum: Challenges 20-11-2013, 23:07
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

Dave, where in the world did that diagram come from? Are any of those numbers or angles related to any of the examples we have been discussing? Certainly none of mine!

That U.S. Sailing...
Forum: Challenges 20-11-2013, 21:17
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

Dockhead is correct, and so am I. In his example the ground Wind is 5kts (say it's from the north). The current is 5kts from north to south.

True Wind (water-referenced) is 0 kts, since the...
Forum: Challenges 20-11-2013, 20:15
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

Yes, my mistake. I had originally had the current flowing in the opposite direction, and I obviously missed that in the editing.
Forum: Challenges 20-11-2013, 09:28
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

Here's something that I had started two days ago, but ran out of steam (and time). I have salvaged some (I hope) germane points. I am using a rather strong current just to make the numbers easy to...
Forum: Challenges 19-11-2013, 20:42
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

WHAT current-related hydrodynamic forces? There are none, unless you are merely talking about there being a down-current vector to your speed/course over ground, or something about the True Wind...
Forum: Challenges 19-11-2013, 20:37
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

Dave, you've said this many times before (the Ground Wind being generated in part by the current). It was wrong the first time, and it's always going to be wrong. Ground Wind is the wind measured...
Forum: Challenges 18-11-2013, 22:58
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

Dave, family life has gotten in the way of analyzing and working out these diagrams. I hope tomorrow I can make the time.

I do want to bring in some actual polars and leeway calculations, so we...
Forum: Challenges 18-11-2013, 19:22
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

Sorry, no. In your diagram you have the boat changing course or heading slightly to "put the current on the leeward or windward bow" (paraphrased). Therefore the bow no longer points straight up,...
Forum: Challenges 18-11-2013, 12:19
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

One difficulty with your diagram is that even while you have the current-induced wind shifting many degrees as you swing the boat to put the current to one side or the other, your...
Forum: Challenges 18-11-2013, 11:59
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

Leeway is most certainly being considered here, particularly if you are using your polars and your intimate knowledge of your boat's sailing characteristics. Your polars tell you your speed through...
Forum: Challenges 18-11-2013, 09:33
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

Lift is exactly the right term to use when the wind shifts away from your bow, allowing you to sail closer to your mark. When used in this context it has nothing to do with hydrodynamics,...
Forum: Challenges 17-11-2013, 22:36
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

If that's your point then I don't think anybody here would disagree.

When there is a current our optimum course can be different from the no-current course. Current and Ground Wind affect the...
Forum: Challenges 17-11-2013, 18:52
Replies: 774
Views: 57,001
Posted By Paul Elliott
Re: Let's Get to the Bottom of the Lee-Bow Effect Once and For All

DumnMad and Hoofsmit, can you please show us a diagram, or describe with numbers, a case where the current generates hydrodynamic forces on a sailboat (or powerboat) that are any different than those...
Showing results 1 to 25 of 65
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