Lee-Bow-Effect/Lee-Bow-Strategy Article

[Mark-1]

He's missed out at least one definition, but supports some of my prejudices, which is always nice.

Also FWIW, I question how common the term lee-bow is in some of these contexts. I'd only heard one definition for years and a lot of these 'strategies' don't really need names, they're either common sense or impractical in the real world where you typically tack on headers and stay with lifts rather than, for instance, remain dogmatically on one pre-planned tack for 5-6 hours trusting that the wind won't change later on in the day.

Anyway, here it is:

http://www.sailingtoday.co.uk/practical/lee-bowing/

 

[lpdsn]

I only got as far as the crossing to Cherbourg diagram and gave up. Shame that in his diagrams he doesn't take account of the effect on boat speed and direction. He assumes that the two boats are both sailing at the same angle and speed to the ground wind and are merely being set to one side or another by the tide. That's not accurate. The difference is that the boat that is lee bowing the tide is getting more southing than the one that isn't because of the apparent wind shift caused by the tide wind.

Edit: Actually I think the way he's confused himself is in the use of the terms ground wind and true wind. Assuming the real true wind (i.e. the ground wind) remains constant (OK not likely often in reality but lets continue...) then the true wind (his definition) will behave like an oscillating shift in a normal windward beat, albeit with a much longer period. The boat that hits the shifts (the boat lee bowing) will gain substantially on the boat that always tacks just as it is lifted on the old tack.

 

[lw395]

The article is plain wrong.

Cross Channel tactics

For this example (above right) the ground wind is from due south and the boats are close-hauled at 45° to the ground wind on either 135° T or 225° T.
Boats will be closehauled wrt the true wind.
Initially the tide going west makes the 'true' wind appear to be more from the W. So the boat on starboard is lifted.
When the tide turns, it's time to be on port.
So in this (hopelessly unrealistic) scenario, the boat which keeps the tide on the lee bow wins.

 

[flaming]

I don’t get that article. He explains the shift due to tide wind, then ignores it when doing his cross Channel example, which is Flat wrong, green will be a long way ahead of red.

 

[savageseadog]

I was mystified too. I've done a few races from Liverpool to the Isle of Man. In reasonable wind conditions the least passage time is about 12 hours which takes the fleet through a full cycle or more of fairly strong cross tidal streams and can definitively state that "lee bowing" works.

 

[Mark-1]

So in this (hopelessly unrealistic) scenario

The utterly theoretical nature of this is one reason I think the term has never historically been used in this context and has only relatively recently been applied to this context.

the boat which keeps the tide on the lee bow wins.

....and this is the other reason. The Green boat hasn't used some clever strategy that needs a name. He's just sailed all the way on his best tack at the time.

Impossible to prove it but I reckon there was one original meaning of the term 'lee-bow-effect', probably the one Perry debunks, and in the last couple of decades or so people have applied the term to all kinds of other things as they try to find ways to make a meaningless term they feel they ought to understand make sense. I'd be interested if people have books/magazines from before (say) 1990 that uses lee-bow in various different contexts.

 

[flaming]

....and this is the other reason. The Green boat hasn't used some clever strategy that needs a name. He's just sailed all the way on his best tack at the time.

That is because the cross channel example is the easy, obvious one.

Try the following example, and see if the boat that just sails on his best tack does as well as the one that thinks about it...

2 Boats go around a leeward mark in the Solent. Let's say it's deep in Osbourne Bay, out of the worst of the tide. The Next mark is on the south side of the Ryde Middle (so basically still in the strong tide of the channel), and is upwind but slightly favours a port tack - i.e you'll spend 60-70% of the leg on Port.
The Tide is flooding, heading East-West. It is 3 knots in the main channel, and 1 knot at the leeward mark out of the channel. The wind is light, say 8 knots.

So the boat who decides what tack to head off on only by which tack he can point closer to the mark (what you might call the cruising option...) sets off on Port.

With everything else being equal, can a boat that rounds right behind him beat him to the next mark?

 

[Mark-1]

I don’t get that article. He explains the shift due to tide wind, then ignores it when doing his cross Channel example, which is Flat wrong, green will be a long way ahead of red.

I confess I haven't close read it, I'm more interested in the definitions, but from the diagram alone if you replaced 'ground' wind with 'true' wind (in the sense that you define true in another thread) it would be spot on, so maybe it's just a typo and 'ground' should be 'true'.

Of course that requires the already ludicrous scenario to be even less plausible: Wind, rather than remaining exactly constant all day, changing through the day to exactly counteract the tidal effect on apparent wind.

...and the Green boat would still be a total fool to rush off downtide for about 72 other reasons.

That is because the cross channel example is the easy, obvious one.

In the last ten years or so I've heard people use the term 'lee-bowing' in that specific context. ie) Sailing to best VMG over two tides on a long sail with the wind on the nose. I'm talking a exclusively about that individual definition. You can offer an alternative definition that you think makes more sense. So can I - at least half a dozen of them.

 

[lw395]

Having sailed dinghies for many years in current, I can recall many races where people who could get the current under their lee bow cleaned up, and those who took it on the weather bow were doomed.
A boat that points high is a weapon on a river, even if a faster footing boat would be all over it on a lake.
Partly that is about keeping out of the worst of the tide.
Partly it's about losing less time tacking.
Partly it's about picking shifts to take the adverse current at the best time.
Partly it's about better sailors being able to point higher.
Partly it's about boats which sail low falling into dirty air and not being able to overtake.
Mix that with some dubious spatial perception, a poor appreciation of vectors and a few beers after the race.
The answer to the lee bow question is something like '42'.

 

[Mark-1]

The answer to the lee bow question is something like '42'.

...and the beauty of this topic as a source of squabbles is that someone else can slightly change the question and tell you you're wrong and it's actualy 47.

The nice thing about the pre-internet lew-bow-effect squabbles is that at least everyone had a consistent idea of what they were squabbling about. Or at least we did in my bubble.

 

[lpdsn]

That is because the cross channel example is the easy, obvious one.

Try the following example, and see if the boat that just sails on his best tack does as well as the one that thinks about it...

2 Boats go around a leeward mark in the Solent. Let's say it's deep in Osbourne Bay, out of the worst of the tide. The Next mark is on the south side of the Ryde Middle (so basically still in the strong tide of the channel), and is upwind but slightly favours a port tack - i.e you'll spend 60-70% of the leg on Port.
The Tide is flooding, heading East-West. It is 3 knots in the main channel, and 1 knot at the leeward mark out of the channel. The wind is light, say 8 knots.

So the boat who decides what tack to head off on only by which tack he can point closer to the mark (what you might call the cruising option...) sets off on Port.

With everything else being equal, can a boat that rounds right behind him beat him to the next mark?

It's a while since I've raced in the Solent and haven't got time to dig out an old chart so can't mentally picture the marks, but in general, beating against the tide stay out of the strongest tide as much as possible.

However it's not really that relevant as lee bowing is not a technique for short legs. Forget the direct tidal aspects of it, it is a technique for making use of tidally-induced shifts in the true wind. That's all. I've used your defn of true wind in thsi context.

PS: in your case going out into the stronger tide gives a tidally-induced header as well as the direct effect of the tide on the boat.

 

[flaming]

In the last ten years or so I've heard people use the term 'lee-bowing' in that specific context. ie) Sailing to best VMG over two tides on a long sail with the wind on the nose. I'm talking a exclusively about that individual definition. You can offer an alternative definition that you think makes more sense. So can I - at least half a dozen of them.

Sorry, I wasn't aware that you were only interested in discussing the definition of "Lee Bowing" to which I totally agree with you, that it has multiple uses and meaning has changed over the years. Context is everything when that phrase is used!

I find the discussion around tidally induced changes to true wind much more interesting!

 

[flaming]

It's a while since I've raced in the Solent and haven't got time to dig out an old chart so can't mentally picture the marks, but in general, beating against the tide stay out of the strongest tide as much as possible.

However it's not really that relevant as lee bowing is not a technique for short legs. Forget the direct tidal aspects of it, it is a technique for making use of tidally-induced shifts in the true wind. That's all. I've used your defn of true wind in thsi context.

The point was a cross tide beat starting in an area of less tide, and going out into an area of strong tide. So, as you point out a tidal induced wind shift. The point of my example was as a counter example to Mark's claim that you didn't have to understand why the wind was shifting to get the best out of it, just sail on your best tack. Which is not true when the tide will not reverse, but increase.

 

[Mark-1]

I find the discussion around tidally induced changes to true wind much more interesting!

Tidally induced changes to true wind are already well understood so there's little to discuss. If people want to discuss that the term 'lee-bow' is unnecessary and deeply unhelpful.

 

[lpdsn]

The point was a cross tide beat starting in an area of less tide, and going out into an area of strong tide. So, as you point out a tidal induced wind shift. The point of my example was as a counter example to Mark's claim that you didn't have to understand why the wind was shifting to get the best out of it, just sail on your best tack. Which is not true when the tide will not reverse, but increase.

Exactly. Although he may tack on the header thinking it's just an ordinary shift, he'd be disadvantaged compared to another boat that understood why things were happening.

 

[Mark-1]

Mark's claim that you didn't have to understand why the wind was shifting to get the best out of it, just sail on your best tack.

My claim was applied to a very specific and unlikely example. (So unlikely as to be impossible in the real world IMHO, and therefore undeserving of a name.) I certainly wasn't arguing that knowing what the tide/wind is likely to do in the future is never useful.

 

[DJE]

I'm confused. Is this the true Lee Bow thread or the apparent Lee Bow thread.

 

[Mark-1]

I'm confused. Is this the true Lee Bow thread or the apparent Lee Bow thread.

I thought it was the 'ground' thread, and that the other thread had needlessly copied me.

I just checked the thread times, and it turns out I'm the dingbat here! Sorry all.

 

[lpdsn]

I thought it was the 'ground' thread, and that the other thread had needlessly copied me.

I just checked the thread times, and it turns out I'm the dingbat here! Sorry all.

The advantage of having two lee bow threads is that you can see which one gets to windward faster.