Lee bow effect when running?

toad_oftoadhall said:
Both these links define the lee bow effect:

http://www.j105.org/docs/noleebow.pdf
http://www.destinationonedesign.com/prep/index.aspx?chapter=ef1a1d70de9643908888312af7e7952c

I'd love to read some alternative definitions from credible sources, but all the stuff I can find with google (I've posted a lot of links in this thread!) agrees with what I consider the generally accepted definition that's been knocking around all my life.
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Those both use concepts (I won't say definitions - neither link provides a definition) of the "lee-bow effect" that are entirely novel to me. I have always understood the effect to be related to a choice, when you are sailing upwind. The choice being to have the current hitting your lee bow or your windward bow. Not plugging directly into the current. I think this is consistent with what flaming is discussing.

I think you are wrong that there is a single, clear, unambiguous meaning of "lee-bow effect". So before you say with such certainty that there is no lee-bow effect, I think you have to clarify what people mean. With one meaning you may be right. Using a different meaning, there certainly is an effect.
 
bbg said:
I have always understood the effect to be related to a choice snip the current hitting your lee bow or your windward bow.
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That's entirely possible, but conflicts with my recollection of the endless childhood debates we had on this. Also IME the lee bow effect is hotly debated on clubs on Estuarys and rivers where up stream and downstream are the only options which rules out a cross tide definition.

Since our definitions don't match, the best way to sort it out is for you to an explanation of the lee bow effect from a credible source in the terms you understand it. It took seconds for me to find definitions that support my experience of this debate. If other definitions are in common use they should be easy to find. Even better an article listing *all* the possible meanings. If a term has multiple meanings I'd expect that fact to be recorded somewhere.

That would demonstrate that both definitions are valid uses of the term.
 
bbg said:
I think this is consistent with what flaming is discussing.
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I think Flaming's posts support the conventional view:

He defines the Lee Bow Effect as: "I get better VMG when I pinch to get the tide on the other side of the keel"

Doesn't mean there are not other definitions of course. Just rather hard to find these other definitions.
 
flaming said:
Wrong Lee bow effect toad... In effect it's not really a "Lee bow" effect at all, but an easy shorthand way of remembering how to take advantage of the tide induced change in the true wind.

Think of it as the tide not moving the boat but instead creating a wind of that strength in the opposite direction. Then add that to the "ground wind" to see how it's shifted. Then just gibe to take advantage of the shifts.
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"Flaming" has it right.

The situation is that you must add the negative vector of the tide, the tidal wind, to the true wind (speed and direction) to obtain an apparent wind, it's also necessary to add the negative vector of the boat's speed and direction to that.
It's complicated which is why lots of people fail to understand it.

The lee bow is a way of making it understandable.
 
flaming said:
Since the way to get the best of that is to keep the tide on the Lee bow, I'm sure you can see that calling it "the lee bow effect" is a nice easy way to remember it.
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This is what flaming was discussing, and he is about as credible an authority on sailing matters as this forum has.

The fact that he and I, who grew up and raced thousands of miles apart and who have never met, both think of this as the lee-bow effect confirms that your understanding of the "definition" is not the only meaning in common usage.
 
bbg said:
This is what flaming was discussing, and he is about as credible an authority on sailing matters as this forum has.
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Well he and I are in total agreement on the two points in dispute.

Flaming: "And as to this not being "the Lee bow effect". Well, no it isn't. "
Flaming: "the lee bow effect" is *******s"


The third point of whether or not there's a second definition in common use is rather hard for anyone to assess without seeing the other definition in use somewhere credible, which you don't seem to be able to find. (Obviously because there's no such second definition.)
 
toad_oftoadhall said:
Well he and I are in total agreement on the two points in dispute.

Flaming: "And as to this not being "the Lee bow effect". Well, no it isn't. "
Flaming: "the lee bow effect" is *******s"


The third point of whether or not there's a second definition in common use is rather hard for anyone to assess without seeing the other definition in use somewhere credible, which you don't seem to be able to find. (Obviously because there's no such second definition.)
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Those points are not in dispute by anyone except you, who raised them in order to say they don't exist.

The fact that seemingly everyone else who has posted on this thread seems to have a different understanding of the meaning of the phrase "lee bow effect" (which is different than the meaning you have introduced) shows how wrong you are that there is a single "very clearly defined" meaning. Which, by the way you haven't defined either. Neither of your links contain definitions.

The issue relates to the turn of the tide, when the current will not be the same throughout the voyage.
 
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toad_oftoadhall said:
The third point of whether or not there's a second definition in common use is rather hard for anyone to assess without seeing the other definition in use somewhere credible
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New information black adder.

An alternative definition in Racing: A Beginner's Guide By Mr John Caig, Timothy Davison

http://books.google.co.uk/books?id=...v=onepage&q="lee bow effect" glossary&f=false

Not sure any of us agree with it but it shows there at least two definitions. Assuming Caig and Davison got it right and I'd hope they fact checked their book.
 
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bbg said:
Those points are not in dispute
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Terrifc!

bbg said:
The issue relates to the turn of the tide, when the current will not be the same throughout the voyage.
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I've found two definitions now. Neither mentions the turn of the tide.

If you read all the threads on Sailing Anarchy and Yachts and Yachting Forums none mention the turn of the tide in relation to the lee bow effect.
 
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VicS said:
With you now!

If the required course is dead down wind having the tide on the lee bow will take the apparent wind slightly away from a dead run in a direction that will contribute a little towards Sarabande's suggestion to sail 10 or 20° off the dead run. Meaning that you can manage that without quite such a large alteration in course away from that required.

Makes sense therefore to gybe when the tide changes so that it is kept on the lee bow.


Crossing the channel with a following wind is a novel concept anyway. In my experience cross channel trips are always a beat to windward
wink.gif
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BUT ON SECOND THOUGHTS

In a situation, as often occurs when crossing the channel, when the tides almost exactly cancel themselves out there will be no advantage in Gybing when the tide changes. You'll stay closer to the rhumb line (is that the correct word ??) if that is of any benefit but that is all.

Useful tactic therefore only really where the tides dont cancel themselves out ... I think.
 
bbg said:
Bully for you. You have won an argument with yourself, by editing my quote. Well done. You must be very satisfied with yourself.
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It's not about winning or losing it's about establishing facts and learning.

See post 50. In your playground mindset I 'lost' the 'argument' on that point.

In fact I've learned that what I've always described as "lee bowing" someone is actually known in some circles as "the lee bow effect".

You call that 'losing', but I've learned something new so it feels far more like winning to me than the two statements that are now acknowledged as true.
 
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Michael Reeves – Fowkes “The Yachtsman’s Manual of Tides”

p. 47 - 49

‘Tide – Wind: Lee-bowing the Tide

For practical purposes when sailing and plotting courses at the chart table, known tacking angles can be applied to the apparent tide-wind diagram as shown in Fig 8.5 which illustrates the following :
A yacht which can sail at 45 degrees to the wind and makes 5 degrees leeway has a total tacking angle of 100 degrees in a situation where there is no tide. However, by changing tack with the changing tidal stream, as shown, and thereby keeping the tidal stream under the leeside of the yacht, the total tacking angle is effectively reduced, in this particular example to 77 degrees due to the effect of the apparent tide-wind.

……for the practical yachtsman, the best advice is to…..: make the best possible use of the apparent tide-wind by keeping the tide running under the lee bow.’

An excellent diagram on p.48 which I cannot post….

I have done this many a time when crossing the Channel and saved hours - always known it as the “lee bow effect” and never heard of the other definition until today.

Hope this helps !!
 
stephenh said:
Michael Reeves – Fowkes “The Yachtsman’s Manual of Tides”

p. 47 - 49

‘Tide – Wind: Lee-bowing the Tide

For practical purposes when sailing and plotting courses at the chart table, known tacking angles can be applied to the apparent tide-wind diagram as shown in Fig 8.5 which illustrates the following :
A yacht which can sail at 45 degrees to the wind and makes 5 degrees leeway has a total tacking angle of 100 degrees in a situation where there is no tide. However, by changing tack with the changing tidal stream, as shown, and thereby keeping the tidal stream under the leeside of the yacht, the total tacking angle is effectively reduced, in this particular example to 77 degrees due to the effect of the apparent tide-wind.

……for the practical yachtsman, the best advice is to…..: make the best possible use of the apparent tide-wind by keeping the tide running under the lee bow.’

An excellent diagram on p.48 which I cannot post….

I have done this many a time when crossing the Channel and saved hours - always known it as the “lee bow effect” and never heard of the other definition until today.

Hope this helps !!
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Brilliant, thanks! Exactly what was required.
 
VicS said:
BUT ON SECOND THOUGHTS


Useful tactic therefore only really where the tides dont cancel themselves out ... I think.
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No.

It's a wind shift over the period of a tide. It's exactly as usefull as any other windshift.

How much it shifts depends on the relative strength of the tide and wind. Strong tide and light winds = big shift, and vice versa.
 
Goodness me! All that nonsense over the difference between saying, "the effect of lee bowing" and, "the lee bow effect". And to cap it all, everyone but the main protagonist was clear that the former was what was being discussed. Still, I suppose it makes for a hobby, of sorts.
 
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