Estimating Leeway
 

Milton Waddams wrote:
Which is more accurate to use in estimating leeway, the true
wind/current or the apparent wind/current?


Milton
How do you tell the difference between "true current" and "apparent
current"? How do you measure either?

And leeway is a function only of the wind, not of the current.

Traditionally, and by that I mean going back a few hundred years to
the square riggers, leeway guesstimates were based not on wind
strength, but on the amount of sail you had to take in. Bowditch
summarizes several other earlier writers and claims:
"1st. When a ship is Close-Hauled, with all her sails set, the water
smooth, and a moderate gale of wind, she is then supposed to make
little or no lee-way.
2d. Allow 1 point, when the top-gallant sails are taken in.
3d. Allow 2 points, when the top-sails must be close-reefed."

Nowadays, if you did it at all it would be based on the tables
generated by a "Velocity Prediction Program," the same software that
generates polar diagrams. These tables are usually organized by true
wind.

Estimating Leeway
 

"Jeff" wrote in message
...
Milton Waddams wrote:
Which is more accurate to use in estimating leeway, the true
wind/current or the apparent wind/current?


Milton
How do you tell the difference between "true current" and "apparent
current"? How do you measure either?

And leeway is a function only of the wind, not of the current.

Traditionally, and by that I mean going back a few hundred years to the
square riggers, leeway guesstimates were based not on wind strength, but
on the amount of sail you had to take in. Bowditch summarizes several
other earlier writers and claims:
"1st. When a ship is Close-Hauled, with all her sails set, the water
smooth, and a moderate gale of wind, she is then supposed to make
little or no lee-way.
2d. Allow 1 point, when the top-gallant sails are taken in.
3d. Allow 2 points, when the top-sails must be close-reefed."

Nowadays, if you did it at all it would be based on the tables generated
by a "Velocity Prediction Program," the same software that generates polar
diagrams. These tables are usually organized by true wind.


Maybe he's thinking of set and drift...


--
"j" ganz @@
www.sailnow.com

Estimating Leeway
 

"Capt. JG" wrote in
:

"Jeff" wrote in message
...
Milton Waddams wrote:
Which is more accurate to use in estimating leeway, the true
wind/current or the apparent wind/current?


Milton
How do you tell the difference between "true current" and "apparent
current"? How do you measure either?

And leeway is a function only of the wind, not of the current.

Traditionally, and by that I mean going back a few hundred years to
the square riggers, leeway guesstimates were based not on wind
strength, but on the amount of sail you had to take in. Bowditch
summarizes several other earlier writers and claims:
"1st. When a ship is Close-Hauled, with all her sails set, the water
smooth, and a moderate gale of wind, she is then supposed to make
little or no lee-way.
2d. Allow 1 point, when the top-gallant sails are taken in.
3d. Allow 2 points, when the top-sails must be close-reefed."

Nowadays, if you did it at all it would be based on the tables
generated by a "Velocity Prediction Program," the same software that
generates polar diagrams. These tables are usually organized by true
wind.


Maybe he's thinking of set and drift...


LOL..... exactly why I stayed away from this one

otn

Estimating Leeway
 

In article ,
Milton Waddams wrote:
[Default] On Mon, 19 Feb 2007 20:25:04 -0800, "Capt. JG"
Maybe he's thinking of set and drift...


Can you explain set and drift? Thank you.

Quick and dirty explanation....

http://en.wikipedia.org/wiki/Set_and_drift
--
Capt. JG @@
www.sailnow.com

Estimating Leeway
 

Milton Waddams wrote in
:


Can you explain set and drift? Thank you.

Milton

BTW thanks to everyone for their generous help on all my questions.

Basically, as Jeff said, leeway involves wind, whereas "set and drift"
involve current.
Problem is, many people now include an either/or factor when using
either/or, phrase/term.
At any rate, for current...... in some cases you can get a good visual
quesstimate of what the true current is doing in both direction and speed
but you'll rarely get any idea as to it's relative affects until after the
fact....I'd say apply true.
For wind, you may be able to get a better read of relative (anemometer)
than true..... kinda.... use whichever one you feel most comfortable with
at a given time.

Like so many aspects, it's hard to say "This is better than That"

Estimating Leeway
 

Milton Waddams wrote:
[Default] On Mon, 19 Feb 2007 20:25:04 -0800, "Capt. JG"
wrote:

"Jeff" wrote in message
...
Milton Waddams wrote:
Which is more accurate to use in estimating leeway, the true
wind/current or the apparent wind/current?


Milton
How do you tell the difference between "true current" and "apparent
current"? How do you measure either?

And leeway is a function only of the wind, not of the current.

Traditionally, and by that I mean going back a few hundred years to the
square riggers, leeway guesstimates were based not on wind strength, but
on the amount of sail you had to take in. Bowditch summarizes several
other earlier writers and claims:
"1st. When a ship is Close-Hauled, with all her sails set, the water
smooth, and a moderate gale of wind, she is then supposed to make
little or no lee-way.
2d. Allow 1 point, when the top-gallant sails are taken in.
3d. Allow 2 points, when the top-sails must be close-reefed."

Nowadays, if you did it at all it would be based on the tables generated
by a "Velocity Prediction Program," the same software that generates polar
diagrams. These tables are usually organized by true wind.

Maybe he's thinking of set and drift...


Can you explain set and drift? Thank you.

As mentioned, set is the direction the current is flowing, and drift
is the strength. It is important to remember that current does not
have a noticeable affect on the boat unless you can take bearings, or
use the GPS to determine that your motion is not what you might first
imagine. Sometimes people make silly claims, like you can feel the
current on the rudder, but assuming there is constant flow in open
water, its best to think of the current as a shift in your coordinate
system. When plotting, you use vector addition to add in the affect
of the current.

Leeway is quite different, since it is a function of the way the
particular boat responds to the wind. It is usually minimal except
when going upwind. When plotting, you add in several degrees (as
appropriate) to your angle to the wind.



Milton

BTW thanks to everyone for their generous help on all my questions.