Is sideways force always exactly perpendicular to the boat's centerline, as
shown by the vectors in Sleight's Manual (link below)? Can the camber of the
sail be forced to shift that force slightly forward?
http://scout235.tripod.com/Sleight_p_31.jpg
Scout

"Scout" wrote in message
...
Is sideways force always exactly perpendicular to the boat's centerline,
as
shown by the vectors in Sleight's Manual (link below)? Can the camber of
the
sail be forced to shift that force slightly forward?
http://scout235.tripod.com/Sleight_p_31.jpg

I think that whoever did those diagrams didn't understand very much about
physics.

What does "sideways force" actually mean? If you think about it, sideways
force must always be perpindicular to the centreline.

In reality, a force is exerted upon a boat in line with the wind. The sails
and keel combine to produce a forward motion that may not be directly
downwind.


Regards


Donal
--

I thought something seemed off with the diagram too, and also believed your
last paragraph to be true. I can see the perpendicular force in the first
figure, but when close hauled, as in fig 2, especially considering the wind
on the structure, I'm not sure why that vector isn't running "slightly" more
toward the stern?
Scout

"Donal" wrote in message
...

"Scout" wrote in message
...
Is sideways force always exactly perpendicular to the boat's centerline,
as
shown by the vectors in Sleight's Manual (link below)? Can the camber of
the
sail be forced to shift that force slightly forward?
http://scout235.tripod.com/Sleight_p_31.jpg

I think that whoever did those diagrams didn't understand very much about
physics.

What does "sideways force" actually mean? If you think about it, sideways
force must always be perpindicular to the centreline.

In reality, a force is exerted upon a boat in line with the wind. The
sails
and keel combine to produce a forward motion that may not be directly
downwind.


Regards


Donal
--

"Scout" wrote in message
...
I thought something seemed off with the diagram too, and also believed
your
last paragraph to be true. I can see the perpendicular force in the first
figure, but when close hauled, as in fig 2, especially considering the
wind
on the structure, I'm not sure why that vector isn't running "slightly"
more
toward the stern?
Scout

I think that the author of the diagram simply failed to express himself
clearly. If we substitute "leeway" for "sideways force" then his diagrams
make a bit more sense. Leeway is not a force, but it is the result of
combined forces.

In fact, leeway is *always* directly downwind. I learned this on my recent
dinghy sailing holiday. There was an area known as "the Graveyard". It
was a lee shore that had very gentle winds. Once you entered the Graveyard,
you were bound to end up on the rocks. The reason was that after a tack,
you would make leeway before you got forward motion. Furthermore, the wind
was so light that it was impossible to get forward movement without bearing
away --- which meant going even closer to the shore..... The first time
that it happened to me was very disspiriting. I thought that I had
forgotten everything that I knew about dinghy sailing.


I'll do a drawing if I get time.

Regards


Donal
--

Donal wrote:


In fact, leeway is *always* directly downwind. I learned this on my recent
dinghy sailing holiday. There was an area known as "the Graveyard". It
was a lee shore that had very gentle winds. Once you entered the Graveyard,
you were bound to end up on the rocks. The reason was that after a tack,
you would make leeway before you got forward motion. Furthermore, the wind
was so light that it was impossible to get forward movement without bearing
away --- which meant going even closer to the shore..... The first time
that it happened to me was very disspiriting. I thought that I had
forgotten everything that I knew about dinghy sailing.


Was there a current to drive you onto the rock or are you saying you
can't sail to windward in light winds???

Cheers

"Nav" wrote in message
...


Donal wrote:


In fact, leeway is *always* directly downwind. I learned this on my
recent
dinghy sailing holiday. There was an area known as "the Graveyard".
It
was a lee shore that had very gentle winds. Once you entered the
Graveyard,
you were bound to end up on the rocks. The reason was that after a
tack,
you would make leeway before you got forward motion. Furthermore, the
wind
was so light that it was impossible to get forward movement without
bearing
away --- which meant going even closer to the shore..... The first
time
that it happened to me was very disspiriting. I thought that I had
forgotten everything that I knew about dinghy sailing.


Was there a current to drive you onto the rock or are you saying you
can't sail to windward in light winds???

Current??? Now why didn't I think of that?

Sadly, there wasn't any current.



Regards


Donal
--

"Donal" wrote

In fact, leeway is *always* directly downwind. I learned this on
my recent
dinghy sailing holiday. There was an area known as "the
Graveyard". It
was a lee shore that had very gentle winds. Once you entered the
Graveyard,
you were bound to end up on the rocks. The reason was that after a
tack,
you would make leeway before you got forward motion. Furthermore,
the wind
was so light that it was impossible to get forward movement without
bearing
away --- which meant going even closer to the shore..... The first
time
that it happened to me was very disspiriting. I thought that I had
forgotten everything that I knew about dinghy sailing.

So, did you end up on the rocks?

Scotty

"Scott Vernon" wrote in message
...
"Donal" wrote

In fact, leeway is *always* directly downwind. I learned this on
my recent
dinghy sailing holiday. There was an area known as "the
Graveyard". It
was a lee shore that had very gentle winds. Once you entered the
Graveyard,
you were bound to end up on the rocks. The reason was that after a
tack,
you would make leeway before you got forward motion. Furthermore,
the wind
was so light that it was impossible to get forward movement without
bearing
away --- which meant going even closer to the shore..... The first
time
that it happened to me was very disspiriting. I thought that I had
forgotten everything that I knew about dinghy sailing.

So, did you end up on the rocks?

Twice!!!! ...And to make matters worse - the second time I had my wife in
the boat. I had assured her that the wind was gentle, and that there was
*no* chance of a capsize at all. Fortunately, she seems to have forgiven
me. AFAICR, she didn't get her hair wet in the capsize.


Regards


Donal
--

I had a vaguely similar experience only with anchored fishing boats instead
of rocks - damned embarrassing, and most power boaters seem to think only in
terms of "just give 'er more throttle!".
Scout

"Donal" wrote
[snip]
... after a tack, you would make leeway before you got forward motion.
Furthermore, the wind was so light that it was impossible to get forward
movement without bearing away --- which meant going even closer to the
shore.....

Scout wrote:
Is sideways force always exactly perpendicular to the boat's centerline, as
shown by the vectors in Sleight's Manual (link below)?
http://scout235.tripod.com/Sleight_p_31.jpg

The short answer is yes. Because sideways force is *defined* to be
perpindicular to the boat's centerline.

Think about it this way: there is a net force from the wind. It's a
vector (i.e. it has a magnitude and a direction.) You can always
express a vector in terms of it's components relative to a coordinate
system. In this case, the've chosen a coordinate system with axes
paralell to and perpindicular to the boat's centerline. So of course
sideways force is perpendicular to the boat's centerline - in the same
way that the x-component of any vector is parallel to the x-axis.

Can the camber of the
sail be forced to shift that force slightly forward?

You can definitely do things to make the net force more forward and
less sideways. i.e. make the forward component larger and the
sideways component smaller.


--
// Walt
//
// There is no Volkl Conspiracy