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LEE BOW EFFECT |
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Presuming Ed
Really should get out more Joined: 26 Feb 05 Location: United Kingdom Online Status: Offline Posts: 641 |
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Topic: LEE BOW EFFECT Posted: 11 Oct 11 at 5:52pm |
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And there was me thinking that the lift/drag curve for a particular foil was a fixed thing. A foil of NCAA section xxxx at an angle of attack (= leeway angle) of x will generate lift of F and drag of D. All physics. If you're saying that there is some magic way the keel becomes "aware" of the angle between the tidaf flow and the seabed, then could you tell me where the brain in the keel is because I haven't found one yet. Also, if there is some way we can "switch on" this "extra lift", the again, that would be really useful because I'll just switch it on all the time.
Edited by Presuming Ed - 11 Oct 11 at 6:08pm |
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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 5:55pm | |
IME, it's not that the boat ahead is lifted, it's that the boat behind is knocked. In the same way that the main has to be sheeted closer than the jib, because it's knocked by the jib. I've always called tacking into someone's lee bow "lee bow-ing" someone, never the "lee bow effect". To me the "lee bow effect" is this mythical thing about magically generating extra lift out of nowhere.
Edited by Presuming Ed - 11 Oct 11 at 6:08pm |
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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 6:07pm | |
Well, he does have a rough idea how to sail....http://www.sailing.org/biog.php?id=USADP4
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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 6:09pm | |
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Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686
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RS400atC
Really should get out more Joined: 04 Dec 08 Online Status: Offline Posts: 3011 |
Post Options Quote Reply Posted: 11 Oct 11 at 6:19pm | |
The lee bow effect debate is largely as JimC says, people talking at cross purposes.
Some people cannot add up the vectors to understand how tide affects your VMG Some people forget the mark is moving through the tide The deniers can't explain what they are denying because the proponents can't explain it properly either, usually because they are working on a badly worded explanation in a sailing book that was not written by a mathematician. There is nothing magic about it, but a tide on your bow definitely has an effect. What seems to a science graduate as the boring predictable unsurprisng addition of vectors is the same magic effect that surprises people who can't add vectors. It's also used to explain any inconvenient/remarkable divergence of courses. A couple of seasons sailing leadmines, well iron mines in fact, in the solent help you realise that the tide is always significant, never constant and doesn't obey the little charts they sell. |
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SoggyBadger
Really should get out more Joined: 26 Oct 10 Location: The Wild Wood Online Status: Offline Posts: 552 |
Post Options Quote Reply Posted: 11 Oct 11 at 6:21pm | |
Actually, the leeward boat is lifted slightly WRT to the apparent wind and also experiences a slight increase in wind speed. |
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Best wishes from deep in the woods
SB |
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JimC
Really should get out more Joined: 17 May 04 Location: United Kingdom Online Status: Online Posts: 6649 |
Post Options Quote Reply Posted: 11 Oct 11 at 7:00pm | |
These sorts of discussions probably feel really intimidating to beginners, but they should in fact be enormously encouraging, because they so often demonstrate that a lack of understanding of the underlying science is frequently no obstruction to sailing a boat fast...
I have to admit I've never really quite understood what GRF is getting at with respect to tides and lee bows: I have no idea whether he's saying the same thing as me or something quite different. |
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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 7:01pm | |
I've never really quite understood what GRF is getting at with respect to pretty much anything.
I'll get me coat.
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Rockhopper
Really should get out more Joined: 16 Nov 07 Location: Eastry Online Status: Offline Posts: 642 |
Post Options Quote Reply Posted: 11 Oct 11 at 7:49pm | |
Don just come over and join us when the winds from the south or south east its perfect for that lee bowing the tide
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Retired now after 35 seasons in a row and time for a rest.
2004 national champ Laser5000 2007,2010,National Champ Rs Vareo |
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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 8:36pm | |
Ok.... Thanks everyone for the really informative replies It's just as I thought...... Bloody complicated to understand, but there is something definitely there. I can feel it when pushing into the tide (& breeze)... It's just working out how to harness it to your advantage to either make the mark without tacking again or getting that extra bit of "lift" & catching the bloke in front by surprise. So can anyone suggest a practical way of demonstrating it's effect to yourself when out practising so it's effect or otherwise is really noticeable?
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Vareo 365
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