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| Laser 28 - Excellent example of this great design Hamble le rice |
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| Rossiter Pintail Mortagne sur Gironde, near Bordeaux |
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LEE BOW EFFECT |
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gordon 
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Joined: 07 Sep 04 Online Status: Offline Posts: 1037 |
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 Topic: LEE BOW EFFECTPosted: 14 Oct 11 at 12:55pm |
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I hope GRF is not advocating a rule 42 infringement!
Gordon |
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Gordon
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Presuming Ed
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Joined: 26 Feb 05 Location: United Kingdom Online Status: Offline Posts: 641 |
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Posted: 14 Oct 11 at 2:16pm |
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By the sounds of it, he's advocating using a perpetual motion machine...
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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: 14 Oct 11 at 2:17pm |
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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: 14 Oct 11 at 2:29pm |
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They're allowed to now, thanks to me and I wish now I hadn't driven it, but the way it was, we Brits obeyed the rules and didn't whilst the Euros just did and ignored the rules. So when we set up Imco (the Mistral OD class we just said yep ignore it, and mark touching). It was great all time time I was fit and young, it's bloody hard work now. Not that the young kids these days have the techniques as shown in the first of those two videos, it's best the body stays still and the rig propels you those girls are hopeless, the second vid, downwind rowing (he's doing it better)was, believe it or not, perfected by my own good self and my then peers, many moons ago and passed on to later generations for our sins. I wrote an article at the time for Eric Twiname in the then Dinghy and Boardsailing, it caused a right furore, but at least the blatant rule breaking was out in the open. But, and back on topic, air rowing is a lot easier and the board a lot faster, with tide on your lee bow!
Edited by G.R.F. - 14 Oct 11 at 2:32pm |
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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: 14 Oct 11 at 7:43pm |
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Absolutely correct, right up until the moment the 'other' foil, the sail, gets orientated against the direction of the tidal flow, even in totally still air. I totally understand where your coming from, and it is true if a boat moves with the flow of the tide it matters not which direction it points in, it just moves along. But once you engage the sail, you introduce another force, then if you orient the foil under th boat in opposition to that second force, you get a resultant movement of the combined forces
I'm still at a lost as to how you can create something from nothing by changing the angle a force is applied at! As the 1.01 v 1 knot argument shows tide on the lee bow will amplify an existing advntage in VMG - but it won't create one. If it did in the pumping example above you would only have to pump once to get the boat moving permanently, but clearly that is not the case! The smiley above almost makes me think GRF has been trolling - but I've never known such a sequence of insult free posts: he's obviously thinking too hard! I just wish he or someone else could explain the magic - then I'd believe in it and, like Father Xmas, it would work for me too.
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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: 14 Oct 11 at 10:46pm |
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I'm going to write it up, it's been years since I did this stuff, but nothings changed, except obviously like just about everything else in life, dumbing down for whatever Agenda, in this instance that muppet writing something up controversially simply to sell a book.
I do lark about, I do take the piss, i am rude, all these things are true, except when somebody asks me for information about a sport I pursue and am enthusiastic about, then I'll generally tell them as it is, or at the very least how i perceive it to be. I get very irritated when other folk for whatever reason, spread disinformation or inaccurate stuff based on ill thought through logic. So I'll do a few Eric Twiname style drawings, and knock them into a logical irrefutable factual proof, then it's done. We could do with something to help the cruisers that come and go through our club, very often when the wind has gone in the evening or drops for whatever reason, using the tide is the only way folk can get home or back to shore. Now it's not going to prove the 'if you pinch' bit that has so much to do with the rocker of the boat/board and it's speed potential sailing free, so can never be proven as an across the board fact. But tide on the actual lee bow has a factual and easily proven increase in a boats performance over the water and to weather, so the 'lee bow effect' is a fact, no question no doubt. The other 'lee bow effect' which is the effect of another sail to the lee bow of your sail, and it's propensity for bending the airflow between both sails which then 'heads' the windward sail to negative effect to such an extent the windward boat will drop back and behind the leeward boat. Again a fact, proven time and again over the years. So Lee Bow effect is a Fact, was a fact before i came along and will remain a fact long after I've gone. I'll do my best to help you understand it, but it will have to be drawings.
Edited by G.R.F. - 14 Oct 11 at 10:49pm |
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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: 14 Oct 11 at 11:02pm |
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That's cool....
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Ian29937
Far too distracted from work 
Joined: 25 May 05 Online Status: Offline Posts: 409 |
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Posted: 14 Oct 11 at 11:23pm |
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"But tide on the actual lee bow has a factual and easily proven increase in a boats performance over the water and to weather, so the 'lee bow effect' is a fact, no question no doubt."
It has a proven effect. In racing terms when people talk about gaining an advantage from the lee bow effect the debate is whether it is worth pinching so that your boat has a lee bow and the opponent does not. If two racing boats both have the tide on the lee bow they both get an equal advantage. If one slows down by pinching to get a lee bow and another sails normally, the result would still be exactly the same as if they weren't in tide. The boat sailing the optimum windward course will win. Please draw the vector diagrams and if you are honest, open minded and logical you'll see for yourself... I used to believe in the effect when I first heard of it, until I tried it and was regularly thrashed by people who knew better. Ian |
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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: 14 Oct 11 at 11:45pm |
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We're not discussing the 'pinching issue' the OP didn't ask that, he asked what 'Lee Bow effect' was wether to pinch or not is a red herring, and as i said even if it were true would be very hull and rocker dependant, some hulls actually function better sailed high, if the hull is carrying a light crew in a rockered displacement hull, it's better to sail high, if it's a straight rockered skiff type hull the reverse would be true, there are too many variables to write a definitive proof, but what has been introduced to this discussion and the one on the US children's forum, is the writings of a pseudo guru and in the effort to sell a book the "Lee Bow Effect" is a myth, statement has been entered. The effect of tide on the Lee Bow is a fact, and yes it is exactly the same for two boats on the same tack.
It's not about wether it works or not, or wether sailing a bit higher might or might not make it work better, it is about when to use it, wether to use it and if the opportunity presents itself for it's use how advantageous that might be. But if someone comes onto a forum, asks in all innocence, what it is, and some well meaning repeater of information gleaned from a book written by someone else for whatever reason, declares it is a nonsense, then that detracts totally from the point of having a forum for discussion. As to your statement it should read, if two boats are sailing into adverse current with the tide on the nose or slightly to the weather bow, and one managed to point high enough to get the tide on the lee bow, then what would be the outcome... The answer to that question very much depends on the type of boat in that scenario as well, to answer that, one would have to have a different answer for different classes of boat. Now a tactical scenario might be as follows, say in a cross on wind with the weather mark out to sea but a mile up the coast and the lee mark is inshore, a typical South Westerly wind sound coast situation, is it better to sail up the coast and stay out of the tide, or is there a sufficient angle out to sea, to take a short tack out into the current, then tack and get the current on your lee bow, to lift you a tad higher than you would have sailed had the long tack you would have taken along the coast in shallow tide free water. This can happen when the tide bends around a coastal bay, then very much the tidal lee bow can be a race winning advantage, if the rest of the fleet have gone for the safe inshore bet.
Edited by G.R.F. - 15 Oct 11 at 12:00am |
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Ian29937
Far too distracted from work
Joined: 25 May 05 Online Status: Offline Posts: 409 |
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Posted: 15 Oct 11 at 12:29am |
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So how do you use this mythical beast if you don't sail higher than the other boats about you. If everyone sails at the same angle to the wind and tide they either all get a lee bow effect or they don't.
You're changing the question, discussing the use of tactics with tidal bends now, (and in your example, you are as likely to lose out as gain by taking the high risk option which would disprove your theory in any case). We are talking about a specific boat on boat situation - if I can get a lee bow when others around me don't, do I gain an advantage ? No.... Ian
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