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LEE BOW EFFECT |
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didlydon
Far too distracted from work Joined: 15 Oct 08 Location: Margate England Online Status: Offline Posts: 280 |
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Topic: LEE BOW EFFECT Posted: 11 Oct 11 at 1:58pm |
It's probably been discussed here before, but someone in my club mentioned the Lee Bow Effect after racing on a light breeze day when the tide was running strongly...... I just nodded & thought I understood, but to be honest didn't really.... So can anyone explain it to me please? Thanx.
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Vareo 365
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rb_stretch
Really should get out more Joined: 23 Aug 10 Online Status: Offline Posts: 742 |
Post Options Quote Reply Posted: 11 Oct 11 at 2:05pm |
My understanding is that when beating against the tide, if the tide is coming at your bow from the lee side then it is effectively pushing you into the wind. This is good because firstly it counteracts leeway and secondly gives you stronger apparent wind as you get pushed into the wind. Sometimes the difference between stuffing and footing is the lee bow effect, which therefore makes it pay to stuff.
Obviously if tide is on the windward side upwind then you are fighting both wind and tide, so can sail anyway near as high or fast. |
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didlydon
Far too distracted from work Joined: 15 Oct 08 Location: Margate England Online Status: Offline Posts: 280 |
Post Options Quote Reply Posted: 11 Oct 11 at 2:13pm |
Stuffing & footing ............ Please explain as well.......
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Vareo 365
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Jack Sparrow
Really should get out more Joined: 08 Feb 05 Location: United Kingdom Online Status: Offline Posts: 2965 |
Post Options Quote Reply Posted: 11 Oct 11 at 2:22pm |
Stuffing (pinching) into wind for height. Footing... Easing off the wind for speed.
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didlydon
Far too distracted from work Joined: 15 Oct 08 Location: Margate England Online Status: Offline Posts: 280 |
Post Options Quote Reply Posted: 11 Oct 11 at 2:33pm |
Ahhhhh..... Thanx! I do know how to sail - honest - just not familiar with the (Slang?) terminology.
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Vareo 365
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JimC
Really should get out more Joined: 17 May 04 Location: United Kingdom Online Status: Offline Posts: 6649 |
Post Options Quote Reply Posted: 11 Oct 11 at 2:44pm |
The lee bow thing is largely a myth...
The theory goes that if you point up so that the tide is one degree on the lee bow instead of 1 degree on the windward bow then you'll magically go much better. Of course if you sail your [expurgated] off so that you point two degrees higher *without slowing down* then you don't need any complicated theories about tide to explain why you're suddenly going better up the beat... Yes, the tide pushes you across the track, but the apparent wind clocks back the other way as a result. Nothing special happens when the tide goes from 0.1 degrees one side to 0.1 degrees the other. It takes ages and a lot of drawing of force triangles to explain why, but that's what happens. Remember all that counts is what the wind is doing relative to the sails and the water is doing relative to the foils. The boat hasn't got a clue what the sand on the bottom of the river is doing... In tide the effective wind direction and speed is not what you get in a moored boat, but what you get in a boat drifting in the current. Of course if the tide is not constant in speed and direction across the race track there are enormous gains to be made by exploiting the differences, but that's something else again: not what was traditionally called the lee bow effect. Edited by JimC - 11 Oct 11 at 2:48pm |
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Oli
Really should get out more Joined: 23 Mar 05 Online Status: Offline Posts: 1020 |
Post Options Quote Reply Posted: 11 Oct 11 at 3:19pm |
jim my understanding of it is that i dont point higher with a tidal lee bow but for the same tacking angle i can effectively sail a shorter distance to the mark as the tide is pushing me into the "as the crow flys" line (crabbing). a velocity diagram may show you as sailing slower but at a better angle, its all down to vmg to the mark as to whether its beneficial.
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Rupert
Really should get out more Joined: 11 Aug 04 Location: Whitefriars sc Online Status: Offline Posts: 8956 |
Post Options Quote Reply Posted: 11 Oct 11 at 4:17pm |
The lee bow effect is one of those things like asymmetric spinnakers lifting the bow - easy to disprove with science, but less easy to explain why it still appears to work in real life!
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G.R.F.
Really should get out more Joined: 10 Aug 08 Location: United Kingdom Online Status: Offline Posts: 4028 |
Post Options Quote Reply Posted: 11 Oct 11 at 4:27pm |
Lee Bow is my particular expertise, have had arguments with Olympics coaches then demonstrated my point by taking ten minutes, yes ten minutes out of the entire Olympic Squad in one instance by it's correct application as against the advice the coaches gave to the squad, a delicious moment.
Anyone who doubts it's effect hasn't had thirty years of tidal racing and sailing, including that muppet that tried to write a lame book debunking it. On a sailboard you actually get to 'feel' the effect it has on the driving forward force of the board, it is very much less in a dinghy. The other Lee Bow effect is that force prevalent at the start of the race when all the boats (boards) are lined up, the sail on boat to your lee bow, if allowed to creep ahead, diverts the wind between both boats and effectively heads the windward boat. So you fight to get your nose ahead, to stuff the guy upwind of you with lee bow, whilst covering the boat to leeward, it's how the fleet divides by approx 1/3rd within minutes of the gun firing. Back to the tide, leaving the line, imperative to take the tide on the lee bow initially to help speed if at all possible, even though the water you're on should be thought of as a conveyor belt, the boats speed over it is not the same. (assuming in this instance a left to right tide within which tidal lee bow would play a part. Kind of difficult doing this in words, sailing in tide is an entire lecture in it's own right and events get won and lost by the correct application and timing of when to 'go for' tide on the lee. Tide on the lee bow can be like a lift whereas tide on the weather bow is almost certainly heading. Just as with wind shifts there are times to play either or, depending on your position in the fleet at any given moment.
Edited by G.R.F. - 11 Oct 11 at 4:28pm |
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Presuming Ed
Really should get out more Joined: 26 Feb 05 Location: United Kingdom Online Status: Offline Posts: 641 |
Post Options Quote Reply Posted: 11 Oct 11 at 4:38pm |
Of course, there is an argument that if your opposition _do_ believe in the "lee bow effect", then the last thing you actually want to do is disabuse them of their belief. If they believe that stuffing the bow up and sailing slowly is the best way to win a race, then who are we to try and dissuade them....
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