2 point question
 

In most of my posts on this subject I have mentioned a trip going east
north west and south. In this post I referred to the original
question, and in the question the trip goes east south west and north,
so in this post the destination would be east of the start-point.
Sorry if anyone got confused.

Peter S/Y Anicula

"Peter S/Y Anicula" skrev i en
meddelelse ...
I was taught that:

Speed is the forward motion through the water
Leeway is the sideways movement of the boat through the water
Current is the movement of the water over the ground
Steered course is the way you point
Sailed course is the direction that you move through the water
Course over the ground (is that called course made good ?) is the
direction you move over the ground
etc.

If one sails as you described in the question (on the northern
hemisphere), one sails toward a destination B that is west of the
starting-point A (if there were no current). The position after 56
hours is point C.
So, If your teacher taught you that when you sail from A toward B
and
arrive at C then AC is the "current" then he must have been an
electrician and not a sailor. You could justify to call BC for
current, though the distance might be a result of more than just
the
surface-waters movement over the ground.

Peter A/Y Anicula


"Bart Senior" skrev i en meddelelse
et...
In most places where people are sailing, current would be
the greater effect.

Other factors, can all be lumped into something that for
lack of a better word is called current.

That is what I was taught.

DSK wrote

Yes it is, but a minute of longitude differs in length as you go
north
and/or south.

2 point question
 

On the south pole, even if you insist on going only 14 nm on every
leg, you could reach the 28 nm that you mentioned in your earlier
post, so you wouldn't have to admit that you have a really bad
compass. You might have to bring an iceboat though.

Peter S/Y Anicula


"Wally" skrev i en meddelelse
...
Peter S/Y Anicula wrote:
1.86nm is not far enough for me: For one thing, I can sail much
faster
than your 1 knot. If I can do 6 knots, the figure would be 11.16
nm,
assuming your math is correct, but you can do better than that,
even in your slow boat.

The misapprehension of the question that led to this discourse was
concerned
with distances of 14nm. You might sail the course six times faster,
but
you'll still be 1.86nm from the start.


Why don't you take a trip to the South Pole ?

Because my ice-breaker would founder on the mountains.


--
Wally
www.artbywally.com
www.wally.myby.co.uk

2 point question
 

Peter S/Y Anicula wrote:

On the south pole, even if you insist on going only 14 nm on every
leg, you could reach the 28 nm that you mentioned in your earlier
post, ...

How?


--
Wally
www.artbywally.com
www.wally.myby.co.uk

2 point question
 

You would start with the outer circle going east then go closer to the
pole moving south...
If the inner circle has an arc of 180 degrees plus the arc of the
outer circle, then the end-point should be opposite the start-point,
and the distance over the pole would be 2 x length of legs plus
diameter of inner circle: more than 28 nm in at 1 knot and
more than 168 nm at 6 knot.

Peter S/Y Anicula

"Wally" skrev i en meddelelse
...
Peter S/Y Anicula wrote:

On the south pole, even if you insist on going only 14 nm on every
leg, you could reach the 28 nm that you mentioned in your earlier
post, ...

How?


--
Wally
www.artbywally.com
www.wally.myby.co.uk

2 point question
 

The terminology is not quite right, substitute inner circle with the
leg along the inner circle...
So it should be:

You would start with the leg along the outer circle going east then go
closer to the
pole moving south...
If the leg along the inner circle has an arc of 180 degrees plus the
arc of the
leg along the outer circle, then the end-point should be opposite the
start-point,
and the distance over the pole would be 2 x length of legs plus
diameter of inner circle: more than 28 nm in at 1 knot and
more than 168 nm at 6 knot.

Peter S/Y Anicula


"Peter S/Y Anicula" skrev i en
meddelelse ...
You would start with the outer circle going east then go closer to
the
pole moving south...
If the inner circle has an arc of 180 degrees plus the arc of the
outer circle, then the end-point should be opposite the start-point,
and the distance over the pole would be 2 x length of legs plus
diameter of inner circle: more than 28 nm in at 1 knot and
more than 168 nm at 6 knot.

Peter S/Y Anicula

"Wally" skrev i en meddelelse
...
Peter S/Y Anicula wrote:

On the south pole, even if you insist on going only 14 nm on
every
leg, you could reach the 28 nm that you mentioned in your
earlier
post, ...

How?


--
Wally
www.artbywally.com
www.wally.myby.co.uk

2 point question
 

Both Peter and Wally deserve 5 points for taking this
silly question so far.

Bart

Peter S/Y Anicula wrote

The terminology is not quite right, substitute inner circle with the
leg along the inner circle...
So it should be:

You would start with the leg along the outer circle going east then go
closer to the
pole moving south...
If the leg along the inner circle has an arc of 180 degrees plus the
arc of the
leg along the outer circle, then the end-point should be opposite the
start-point,
and the distance over the pole would be 2 x length of legs plus
diameter of inner circle: more than 28 nm in at 1 knot and
more than 168 nm at 6 knot.

Peter S/Y Anicula


"Peter S/Y Anicula" skrev i en
meddelelse ...
You would start with the outer circle going east then go closer to
the
pole moving south...
If the inner circle has an arc of 180 degrees plus the arc of the
outer circle, then the end-point should be opposite the start-point,
and the distance over the pole would be 2 x length of legs plus
diameter of inner circle: more than 28 nm in at 1 knot and
more than 168 nm at 6 knot.

Peter S/Y Anicula

"Wally" skrev i en meddelelse
...
Peter S/Y Anicula wrote:

On the south pole, even if you insist on going only 14 nm on
every
leg, you could reach the 28 nm that you mentioned in your
earlier
post, ...

How?


--
Wally
www.artbywally.com
www.wally.myby.co.uk

2 point question
 

Peter S/Y Anicula wrote:
The terminology is not quite right, substitute inner circle with the
leg along the inner circle...
So it should be:

You would start with the leg along the outer circle going east then go
closer to the pole moving south...

I hadn't realised it would work differently at the south pole... I'll do
some numbers later and see what I come up with.


If the leg along the inner circle has an arc of 180 degrees plus the
arc of the leg along the outer circle, then the end-point should be
opposite the start-point,

That doesn't quite sound right - if the leg along the outer circle, plus the
leg along the inner circle, add up to a total of 180 degrees longitude, then
the end point would be opposite the start point.


and the distance over the pole would be 2 x length of legs plus
diameter of inner circle: more than 28 nm in at 1 knot and
more than 168 nm at 6 knot.

Yup. Proving that my compass does indeed work, in some places at least.


--
Wally
www.artbywally.com
www.wally.myby.co.uk

2 point question
 

Bart Senior wrote:
Both Peter and Wally deserve 5 points for taking this
silly question so far.

Ah, bonus points for waffling...

(The apple's in the post, teach!)


--
Wally
www.artbywally.com
www.wally.myby.co.uk

2 point question
 

Wally wrote:

If one starts from 7nm N of the equator, and goes ESWN, one ends up at the
start point.

Right! I didn't think of that angle...

... Starting on the equator, I get 0.000116nm - 0.215m.

Now that I have my referance library and a spreadsheet instead of a
pocket calculator and faulty memory, I'll try again. It's a more
interesting problem than I thought it'd be....




now I have another question, would the offset be constant as you move
further north or south?


No, it increases. And the change isn't linear.

Yes, I realized this thinking about it on the drive home. So what is it
proportional to, the arcsine?

You and Peter deserve your points. Maybe one day Taddy will write a poem
about you... now there's something to brag about to your grandkids...

Fresh Breezes- Doug King

2 point question
 

Wally wrote:

If the leg along the inner circle has an arc of 180 degrees plus
the
arc of the leg along the outer circle, then the end-point should
be
opposite the start-point,

That doesn't quite sound right - if the leg along the outer circle,
plus the
leg along the inner circle, add up to a total of 180 degrees
longitude, then
the end point would be opposite the start point.

If you count the arc with sign, whitch is probably the right thing to
do, you are right. I just counted the size - independent of direction.


Peter S/Y Anicula



"Wally" skrev i en meddelelse
...
Peter S/Y Anicula wrote:
The terminology is not quite right, substitute inner circle with
the
leg along the inner circle...
So it should be:

You would start with the leg along the outer circle going east
then go
closer to the pole moving south...

I hadn't realised it would work differently at the south pole...
I'll do
some numbers later and see what I come up with.


If the leg along the inner circle has an arc of 180 degrees plus
the
arc of the leg along the outer circle, then the end-point should
be
opposite the start-point,

That doesn't quite sound right - if the leg along the outer circle,
plus the
leg along the inner circle, add up to a total of 180 degrees
longitude, then
the end point would be opposite the start point.


and the distance over the pole would be 2 x length of legs plus
diameter of inner circle: more than 28 nm in at 1 knot and
more than 168 nm at 6 knot.

Yup. Proving that my compass does indeed work, in some places at
least.


--
Wally
www.artbywally.com
www.wally.myby.co.uk