Leeway

"In the end, leeway is simply the difference between the desired course over the water and the achieved course over the water. Nothing more, nothing less."
That is what I think I also said, but given 'downthecreek's question
"So, when you sail across a strong weather going tide, reaching with a light wind, and end up to windward of the buoy for which you set your course, that's still leeway?"
it would suggest that we are wrong!
What I called Leeway was describing 'Course To Steer'.
Ho Hum, back to the books - or maybe not, as I tend to get to where I wanted to go, and I've got nothing to prove to anyone /forums/images/graemlins/grin.gif
 
Well given all the conflicting opinions from the "experts" this was obviously not a simple question. I really like saltyjohn's answer - it's very elegant: [ QUOTE ]
...leeway is simply the difference between the desired course over the water and the achieved course over the water. Nothing more, nothing less.
Tidal set, which I'm sure you also realise, will cause your steered course to differ from your course achieved over the ground.

[/ QUOTE ]
It may come as a surprise then, that I don't quite agree with him. If you will bear with me - this speaks also to those who have said that in going dead downwind, you experience no leeway. I contend that sailing dead downwind is all leeway, since leeway in its simplest terms is that component of wind-driven motion that is downwind. Power-driven vessels also experience leeway, BTW. The keel, rudder and deadwood (and to some degree, the sails) convert leeway to forward motion - without these and discounting current, you would only drift along in the direction of the wind like a hot-air balloon. Ultimately leeway acts on the boat much like tidal set. It's not practical to calculate leeway by itself, but when you construct a tidal triangle the drift vector is a combination of current, tidal stream, surface drift and leeway.
 
Re: Leeway: Here\'s the only answer

O now I understand - except that I don't remember the brazier and chestnuts bit! Tales from the Riverbank was around when I was a child and I actually met the man once. I was 11 and it was 1967. All I could say was "My names Johnny Morris as well". I waited for some words of wisdom from the great man. He said '"Oh!" and moved on...
 
You are quite right, it is a simple effect: the resultant of a number of vectors. But what I thought the OP was after was an explanation, given that there is leeway, how the forces on the boat behave as a consequence of it.

That is, how the forces that resist and limit the leeway are generated.
 
Ah, but if you intend to steer dead downwind then the resultant motion is not leeway. Remember that leeway is the unintended componant of your course over the water.
 
Re: Leeway: Here\'s the only answer

[ QUOTE ]
And there was me thinking that Leeway was the accumulative effects that changed the boats COG from direction that you were pointing it to!

Just shows how wrong one can be.

<u>Note to me</u>: Carry on calling it Leeway and calculating it as I always have, but don't tell anyone /forums/images/graemlins/wink.gif

[/ QUOTE ]

Some people cannot have simple lives - they have to be scientific and confuse not only themselves, but everyone else who's been happily sailing alone .... /forums/images/graemlins/wink.gif
 
Re: Leeway: Here\'s the only answer

[ QUOTE ]
http://www.sailtrain.co.uk/navigation/cts.htm


Leeway with a course to steer
If there is leeway when you are working out the course to steer there is no change in the calculations. Everything is worked out as if there was no leeway, but the last step once you have the water track is to decide if the leeway is to be added or subtracted from the water track to find the correct course to steer. This is the course that is passed to the helmsman.

Leeway is applied in to the wind with a course to steer as you are countering the effect it is going to have.

[/ QUOTE ]

Simple, nice, and I'll go with that.

Once you have sailed your boat in varying conditions most will get a feel for how much to allow ...
 
Re: Leeway: Here\'s the only answer

Nigel at least once thing that has'nt changed is your capacity to to talk rubbish ..... copiously.

Working out a course to steer in a tidal situation you need 3 components.. 1, desired COG, 2, Tidal set 3, leeway.

1 and 3 are fixed but 2 changes with time so netting 2 and 3 together is not helpful.

BTW If, as you say, you not worried about the nomenclature of labels being attached to things then why did you leave in such a strop the last time?
 
Re: Leeway: Here\'s the only answer

[ QUOTE ]
Leeway with a course to steer
If there is leeway when you are working out the course to steer there is no change in the calculations. Everything is worked out as if there was no leeway, but the last step once you have the water track is to decide if the leeway is to be added or subtracted from the water track to find the correct course to steer. This is the course that is passed to the helmsman.

Simple, nice, and I'll go with that.

Once you have sailed your boat in varying conditions most will get a feel for how much to allow ...

[/ QUOTE ]

Yes, but when I'm navigating I don't quite do it like that. Yes, everything is worked out as if there were no leeway, but then that course is passed to the helmsman. Give him a couple of minutes to settle, then come up and feel the conditions. Make an estimate of the leeway, then ask the helmsman to harden up by that amount. Avoids the question of adding or subtracting, and is more likely to get the right answer than by trying to assess the conditions from the chart table, particularly when the boat is on a quite different course.
 
Re: Leeway: Here\'s the only answer

[ QUOTE ]
Make an estimate of the leeway, then ask the helmsman to harden up by that amount. Avoids the question of adding or subtracting, and is more likely to get the right answer than by trying to assess the conditions from the chart table, particularly when the boat is on a quite different course.

[/ QUOTE ]

That could be tricky when you are sailing close-hauled!
 
Re: Leeway: Here\'s the only answer

[ QUOTE ]
[ QUOTE ]
Make an estimate of the leeway, then ask the helmsman to harden up by that amount. Avoids the question of adding or subtracting, and is more likely to get the right answer than by trying to assess the conditions from the chart table, particularly when the boat is on a quite different course.

[/ QUOTE ]

That could be tricky when you are sailing close-hauled!

[/ QUOTE ]

No trickier than giving the helmsman a course that he can't hold. At least I can get a feel for the course that can be held, then look at the chart to see where it takes me.
 
Re: Leeway: Here\'s the only answer

[ QUOTE ]
Nigel at least once thing that has'nt changed is your capacity to to talk rubbish ..... copiously.

Working out a course to steer in a tidal situation you need 3 components.. 1, desired COG, 2, Tidal set 3, leeway.

1 and 3 are fixed but 2 changes with time so netting 2 and 3 together is not helpful.


[/ QUOTE ]

I agreed with the post because the one factor that is not calculable is the leeway ... that is applied by estimate. You then correct as you go. Hopefully you are correcting tide by calcualtion as you go as well.
I never even hinted that 2 & 3 are netted together ... wher do you get that from ?
I see your point but my point of applying leeway last and after calculation of CTS is valid.

[edit] Post edited ... will not rise to bait.[/edit]
 
Re: Consider the keel as a sail as well ...

[ QUOTE ]
Hey! Freestyle, I've got one of those as well.

[/ QUOTE ] Blimey! How did you get one of those on a Bene?

In response to Mortehoe's dismissive "more drag", yes there is more marginally more drag. This is significant in light winds, but in stronger winds the benefits outweigh the disadvantages. I'm not too fussed about the speed, what I like is the reduced pitching, and the ability to turn rapidly without losing speed (stalling resistance).
 
Re: I don\'t understand that keel

[ QUOTE ]
M, if you are around next Thursday, 18 Dec, ~ 1530 I'm coming out and having an Xmas drink or 2 at the Tap and Spile. All Dickies/Dinorwic(Felinheli)Penrhyn/Silliwen/Dinas afficionadas are welcome.

[/ QUOTE ] Mmmm! Now that might just tempt me off the wagon . . . (only trying to loose weight so's my kids can't rib me at Xmas about the paunch, you understand).
 
[ QUOTE ]
Ah, but if you intend to steer dead downwind then the resultant motion is not leeway. Remember that leeway is the unintended componant of your course over the water.

[/ QUOTE ]

If that's the way you wish to see it. If you still have to correct for steering error, set and drift, then it's inconsequential that leeway is not blowing you off course. A vessel that's drifting (under bare poles) will make leeway - this would be the only component to its course over water, but I don't know whether this is considered unintended or not. Running downwind, a power-driven vessel can see SMG greater than Speed rung-on - the wind is not acting perpendicular to the vessel's intended course, but it is still leeway. While I agree that in a sailing vessel the only "leeway" we care about is that which pushes us off our intended track, I can still see leeway in its purest sense.
 
Re: Leeway: Here\'s the only answer

[ QUOTE ]
[ QUOTE ]
Working out a course to steer in a tidal situation you need 3 components.. 1, desired COG, 2, Tidal set 3, leeway.

1 and 3 are fixed but 2 changes with time so netting 2 and 3 together is not helpful.


[/ QUOTE ]

I never even hinted that 2 & 3 are netted together ... wher do you get that from ?

[/ QUOTE ]

He must be confusing us - I suggested they are lumped together. The difference between the fix and the DR (the 'set and drift vector') encompasses tidal stream, current, surface drift, steering error and leeway - I don't see any advantage in breaking them into separate components and I challenge anyone to provide one. Yes I know you can pre-plan based on tidal predictions and estimations of the wind effects to get an EP, but who would bother? All of those components are variable; I have no idea how anybody can think leeway is fixed? Since they are variable pre-planning is not much better than a WAG and won't replace empirical observations (fix-DR-fix-EP).
 
Re: Leeway: Here\'s the only answer

I would like to think he did ... but he specifically names me in his post in his typical friendly way - even though often he fails to read what i and others actually write. But why change habit of a lifetime ... /forums/images/graemlins/wink.gif /forums/images/graemlins/wink.gif /forums/images/graemlins/wink.gif Jimi's Jimi ... aint that fact ! /forums/images/graemlins/laugh.gif

Even I fail to read properly sometimes - but I admit and own up to it !! /forums/images/graemlins/shocked.gif
 
Re: Leeway: Here\'s the only answer

I seem to recall that you decide where you want to go, then allow for the tide sending you every which way to produce your course to steer.

This magic number is given to the helmsman, rounded to the correct half point so he can steer it.

Once on the way you then look over the back end of the boat and note the angle between the lubber line, extended aft, and the nice white trail through the water. The angle between the two lines is then the amount of leeway that you are making at that time.

You can then tell the helmsman to steer up an amount to counter the effect or you use it to check the actual route over the ground that you are tracking.

Either way it is a variable rather than fixed amount, rather akin to the drift induced in a high speed turn by a decent car like the S2000 /forums/images/graemlins/smile.gif
 
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