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LEE BOW EFFECT |
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JimC 
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Joined: 17 May 04 Location: United Kingdom Online Status: Offline Posts: 6661 |
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 Topic: LEE BOW EFFECTPosted: 12 Oct 11 at 4:36pm |
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OK, GRF I think I see what you are talking about... To my mind that's an entirely different thing to the classic "lee bow/tide" fallacy. Am I right in thinking you're saying there's (often?) a tactical advantage to taking the tack that gets you nearest to the mark most quickly...
Edited by JimC - 12 Oct 11 at 4:36pm |
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2547
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Joined: 11 Aug 11 Online Status: Offline Posts: 1151 |
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Posted: 12 Oct 11 at 5:42pm |
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Poor old GRP gibbon ... he's having a bit of trouble with his maths ...
If you have a true wind of 5 knots (i.e. the wind over the ground) and a 5 knot cross tide (i.e. 90 degrees to the true wind running left to right) you have a apparent wind of 7.07 knots which is 45 degress different to the true wind ... in the gibbons example you sail straight to the windward mark on starboard ... if it's laid square to the line by a race officer who has laid a windward leg to the true wind as he is anchored to the land and isn't experienceing the apparent wind which all sail boats do ... This example is nothing to do with the lee bow effect .... which as JimC says is a fallacy ... Edited by seamonkey - 12 Oct 11 at 5:43pm |
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I luv Wight
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Joined: 28 Jan 05 Location: United Kingdom Online Status: Offline Posts: 628 |
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Posted: 12 Oct 11 at 6:11pm |
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But doesn't the RO notice the tidal current, and offset the windward mark?
It can be good to 'lee-bow ' the tide, but only because the tide is always variable across the course. If you can stay close to the shore in weaker current by pinching a bit, it does gain a lot over those who foot off into stronger adverse current, - reducing the apparent wind, so they sag off even more - and they also have to do extra tacks. |
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rb_stretch
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Joined: 23 Aug 10 Online Status: Offline Posts: 742 |
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Posted: 12 Oct 11 at 6:34pm |
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Clearly there are different definitions around as I've always used it and been around people who have used it to describe tide coming in on your lee bow and pushing you into the wind. |
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2547
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Joined: 11 Aug 11 Online Status: Offline Posts: 1151 |
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Posted: 12 Oct 11 at 7:42pm |
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if the course is square to the apparent wind then it dosn't make any difference. The other examples you describe are just tactical tidal issues to manage. Of course current is a key tactical issue but this thread is about the so called lee bow effect
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G.R.F.
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Joined: 10 Aug 08 Location: United Kingdom Online Status: Offline Posts: 4028 |
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Posted: 12 Oct 11 at 7:47pm |
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Eh? come on Jim, don't you be a chump.. It's not a fallacy, tide on your lee bow assists you, in some circumstances if the RO doesn't spot it, or it comes on during an event (say over lunch) you can single tack a beat and even then some idiots go the other way... Tell me you'd go the right way now, i refuse to believe you don't 'get it'. It's written large by Eric Twiname in start to win I'll wager.. I'm going to find that book and have a look. I can't believe any of you are even doubting it. |
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JohnW
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Joined: 17 Jul 07 Location: United Kingdom Online Status: Offline Posts: 552 |
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Posted: 12 Oct 11 at 8:04pm |
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At the half way mark you are closer to the final destination over the ground, but you are no nearer the mark through the water - the other guys get the tidal benefit when they tack as you start loosing out. However...
As above, it does make tactical sense, in the same way that it is (generally) better to take the long tack first on a very one sided beat, to insure against over standing the lay-line from a long way out. |
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sargesail
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Joined: 14 Jan 06 Location: United Kingdom Online Status: Offline Posts: 1459 |
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Posted: 12 Oct 11 at 8:08pm |
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Exactly - not lee bow but a tidal consideration.
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G.R.F.
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Joined: 10 Aug 08 Location: United Kingdom Online Status: Offline Posts: 4028 |
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Posted: 12 Oct 11 at 8:09pm |
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No, go back to my scenario.
Taking the lee bow effect tack first, straight away, lets say the tide eases for the 2nd part of the beat.. = you're ahead you win. Lets say it doesn't, it increases, they've gone too far = they over stand. Tide is never ever constant.
Edited by G.R.F. - 12 Oct 11 at 8:11pm |
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JimC
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Joined: 17 May 04 Location: United Kingdom Online Status: Offline Posts: 6661 |
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Posted: 12 Oct 11 at 8:15pm |
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Same term, different meanings... it sounds as if you've never come across the traditional lee bow fallacy. That says that if the tide is more or less bang on the nose you should pinch up so that the tide is fractionally on the lee bow because even though you'll go more slowly the tide will push you up to windward. Its nothing to do with the choice of which tack is favoured and thus which you should be on, which is what I believe you are talking about. |
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