"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
--

"Nav" wrote in message
...
How do you think it related to the change in tide height that day?

I've no idea.

Our destination, Cherebourg, is a deep water port with 24 hour access to the
marina. We had all done the trip many times, so we weren't watching the
charts too closely. With hindsight, it would have been interesting to check
the depth.


Regards

Donal
--

The reason I ask is that wind and air pressure affect the tide height
and I would expect that that effect could alter time of peak tide and
stream. The question, would such an effect also alter time of slack
water differently from time of high water? I suspect not much.

Cheers

Donal wrote:

"Nav" wrote in message
...

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


I've no idea.

Our destination, Cherebourg, is a deep water port with 24 hour access to the
marina. We had all done the trip many times, so we weren't watching the
charts too closely. With hindsight, it would have been interesting to check
the depth.


Regards

Donal
--

"Nav" wrote in message
...
The reason I ask is that wind and air pressure affect the tide height
and I would expect that that effect could alter time of peak tide and
stream. The question, would such an effect also alter time of slack
water differently from time of high water? I suspect not much.


I tend to agree with you. However, I cannot think of any other explanation.


Any ideas?


Regards

Donal
--

You should complain to the hydrographic offic. Tide tables are hardly
rocket science!

Cheers

DSK wrote:


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