"Peter S/Y Anicula" wrote in message
...
It depends of the area and of the duration of the trip.

There is 3 sources of tidal current: Tidal current tables (ATT),
Tidal
current charts and tidal currents shown in the sea charts.

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.
Generally there is a period of relatively weak currents around HW
and
LW and the current will run faster halfway between HW and LW.

That's what I thought, but I want to be sure.



If the trip is expected to take 9 hours it would best to leave
around
6.30
so you can sail in two periods of slack (weak currents) and one
period
of favourable current.
If the trip is expected to take 3 hours, if you leave around 9.30
you
should be able to sail the whole trip in favourable current.


Should take about 8 hrs., but you know sailing, could be longer.
At a different location there is a narrow channel , with strong
currents, to go through. this should be done at slack tide.


I'm sure Donald or some of the others who sail in areas of strong
tides could elaborate further, but they probably think that you need
the mental exercise of figuring it out yourself.

Nah, they know me better than that.

Thanks, Peter.

Scotty

"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.

DSK

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.

Cheers

Nav wrote:


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.

Cheers

Personally, I disagree. You need to know where you are (narrow
opening/wide opening) and various given conditions before you start to
apply any particular rule. Compare your tables (tide/current) for the
particular locale, then see if a particular rule applies at all times or
only sometimes.

otn

"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.

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

"DSK" wrote in message
.. .
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.


A couple of years ago we encountered a tide that seemed to be an hour early.
Five boats set off from St Peter port for the trip to Cherbourg. The trip
took us through the Alderney Race, where the stream can reach more than 10
kts! We had planned to catch the last of the tide .... in fact we caught
the first of the next tide!

Afterwards, we all checked our figures, and we concluded that the tide had
definitetly turned earlier than forecast. I suspect that weather systems
can have an effect.

In future, I will always leave half an hour earlier!!!



Regards


Donal
--

How do you think it related to the change in tide height that day?

Cheers

Donal wrote:

"DSK" wrote in message
.. .

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.



A couple of years ago we encountered a tide that seemed to be an hour early.
Five boats set off from St Peter port for the trip to Cherbourg. The trip
took us through the Alderney Race, where the stream can reach more than 10
kts! We had planned to catch the last of the tide .... in fact we caught
the first of the next tide!

Afterwards, we all checked our figures, and we concluded that the tide had
definitetly turned earlier than forecast. I suspect that weather systems
can have an effect.

In future, I will always leave half an hour earlier!!!



Regards


Donal
--