"Thom Stewart" wrote ...
Scott,

You've seem to have forgotten "The Gulf Stream Master" Jax. I'm sure
he
can help you ride the eddies:^) Maybe even find you a stray current
heading south (g)

Not forgotten, simply ignored.



Now, for what's it worth. The Tide Flow is a sine wave. Us common
folk
understand that slack water is at the top and bottom of the wave. So
slack is, roughly about a hour and it is roughly in the upper 30%
counting the end of the rising tide and the beginning of the Ebb.
15% to
the HW and 15% roughly to the Max Flow. That means about two hours
to
max flow, 8 hours of max flow and then another couple of hour of
diminishing flow to LW.

That doesn't make allowance for land masses, rivers, depth, etc.
Also
the time differences of where the HW takes place. So if you are
sailing
a Riding Tide you can increase your Max Flow by watching your
location
and tide tables times.


Thanks, Thom.

Scotty

"Nav" wrote in message
...


DSK wrote:

"Peter S/Y Anicula" wrote...

If you only know the time of HW and LW, you can assume that the

curve

of the tidal current will look a bit like a sinus curve.


Yes, that's true. The current will also follow the 'rule of 12s'
somewhat, lagging because of the momentum of the water in motion.

In the absence of current tables, assume the max current is at
7/12s the
interval between high & low water.


Got that wrong Doug. Tidal stream is generally strongest at the time
of
the fastest rate of change of tide height. That is most often about
halfway between high and low water. Look it up.

Isn't 7/12s 'about halfway'?

look it up.

Scotty

Scott Vernon wrote:
Isn't 7/12s 'about halfway'?

look it up.

Not when it's Nav-math.

And otnmbrd's post is really to the point... general rules are nice, but
every location is a special case and will trump most of the general
rules.

One of the most frustrating things around here is that the tide tables
are usually in error by at least half an hour. The tidal current in
Snow's Cut (for example) is very strong, and so far I have yet to see it
run on schedule. It's annoying after planning a departure at an
inconvenient time so as to arrive at slack, only to find the current
running like a champ with no sign of slacking.

Fresh Breezes- Doug King

"DSK" wrote in message
.. .
Scott Vernon wrote:
Isn't 7/12s 'about halfway'?

look it up.

Not when it's Nav-math.

And otnmbrd's post is really to the point... general rules are nice, but
every location is a special case and will trump most of the general
rules.

One of the most frustrating things around here is that the tide tables
are usually in error by at least half an hour. The tidal current in
Snow's Cut (for example) is very strong, and so far I have yet to see it
run on schedule. It's annoying after planning a departure at an
inconvenient time so as to arrive at slack, only to find the current
running like a champ with no sign of slacking.

The current in cuts between two tidal domains is very difficult to predict.

BTW, I was flying up from FL last week and had a great view of Snow's Cut from 7
miles up. In fact I had great views of the coast both down and back. And the
Song Airlines off-season rate was less than what I paid for a 20 minute bi-plane
ride on the Vineyard this summer.

"Thom Stewart" wrote in message
...
Scott,

You've seem to have forgotten "The Gulf Stream Master" Jax. I'm sure he
can help you ride the eddies:^) Maybe even find you a stray current
heading south (g)

Jax also insisted that the time of high water and slack current must be the
same, to be otherwise would violate the laws of physics (on his planet).





Now, for what's it worth. The Tide Flow is a sine wave. Us common folk
understand that slack water is at the top and bottom of the wave. So
slack is, roughly about a hour and it is roughly in the upper 30%
counting the end of the rising tide and the beginning of the Ebb. 15% to
the HW and 15% roughly to the Max Flow. That means about two hours to
max flow, 8 hours of max flow and then another couple of hour of
diminishing flow to LW.

While the current flow in "simple harbors" may follow a sine curve, in cuts
between two bodies of water the flow is different. The curve is more
"squarish," that is, the flow ramps up quicker and stays high longer. The
duration of slack is reduced. The best example is Hell Gate in New York.

IIRC, the flow rate is proportional to the square root of the different of
height of the two bodies.

"Scott Vernon" wrote in message ...
I found some current charts for some areas, they give slack, max ebb,
and max flow. this I understand.
For other areas I find only the H & L tide chart. I want to make max
use of the tide (ebb). Say H is at 0800 and L is at 1400. is it simply
a matter of shoving off at 0800 and 'ride the out going tide till
1400?
TIA

Scotty


Perhaps if you modified your vessel and made it float like this one:
http://pao.cnmoc.navy.mil/pao/n_onli...hotos/flip.jpg

You would get a great current ride. This Navy ship has been in 80 foot seas!

Joe

Jeff,

You're not telling the full truth with "Hell's Gate" are you? You are
leaving out the River flow. That is a constant and mentioned as a
variation to Tidal flow. There are many variations on Tidal flows,
including the Moon, which causes abnormal high and low tides. When
coupled to large bodies of water constricted thru small inlets the sine
wave will be knocked for a loop. Much like a clogged drain on a sink.
LIS has its share of them. The Narrows, Plum Gut, Fisher Island to name
a few. Every place in the World has its' variations, the higher the
Latitudes, the greater the number. Fundy, Solvent, Gibraltar, Georgia
Straits, Cape Horn, etc. The list is endless but local knowledge has
learned to handle it. That's why we sail. It is still more of an Art
than a Science!

Ole Thom

That's one heck of a big submarine!!!


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

"Joe" wrote in message
om...
"Scott Vernon" wrote in message
...
I found some current charts for some areas, they give slack, max ebb,
and max flow. this I understand.
For other areas I find only the H & L tide chart. I want to make max
use of the tide (ebb). Say H is at 0800 and L is at 1400. is it simply
a matter of shoving off at 0800 and 'ride the out going tide till
1400?
TIA

Scotty


Perhaps if you modified your vessel and made it float like this one:
http://pao.cnmoc.navy.mil/pao/n_onli...hotos/flip.jpg

You would get a great current ride. This Navy ship has been in 80 foot
seas!

Joe

Jeff Morris wrote:
The current in cuts between two tidal domains is very difficult to predict.

I bet it is. Lots and lots of variables...



BTW, I was flying up from FL last week and had a great view of Snow's Cut from 7
miles up. In fact I had great views of the coast both down and back.

I've had the chance to do this too... a while back, though. The Outer
Banks and the Eastern Shore are fascinating to fly over. Snow's Cut
isn't really one of the highlights, visually speaking. ;)

Fresh Breezes- Doug King

"Joe" wrote

Scotty


Perhaps if you modified your vessel and made it float like this one:

http://pao.cnmoc.navy.mil/pao/n_onli...photos/flip.jp
g

You would get a great current ride. This Navy ship has been in 80
foot seas!

What the heck is that? and where is it?

SV