Seamanship Question #32
 

It's high tide. The cycle from High to Low is 6 hours.

What is a quick way to estimate the drop tide height
in the next hour?

Seamanship Question #32
 

"Bart Senior" .@. wrote in message ...
| It's high tide. The cycle from High to Low is 6 hours.
|
| What is a quick way to estimate the drop tide height
| in the next hour?


The rule of thirds??

Cheers,
Ellen

P.S. thanks for sailing content

Seamanship Question #32
 

Ellen MacArthur wrote:
"Bart Senior" .@. wrote in message ...
| It's high tide. The cycle from High to Low is 6 hours.
|
| What is a quick way to estimate the drop tide height
| in the next hour?


The rule of thirds??


Wrong...another lubber I see. The rule of thirds is fo tital stream
flows .

For height you use the rule of 12.

Joe


Cheers,
Ellen

P.S. thanks for sailing content

Seamanship Question #32
 

"Joe" wrote
| Wrong...another lubber I see. The rule of thirds is fo tital stream
| flows .
|
| For height you use the rule of 12.

Don't EVER call this girl a lubber, you farmer! :-)

Rule of thirds works for tide height. In the first two hours it goes down 1/3 of its height.
In the next two hours it goes down 1/3 more and in the last two hours it goes down the last
1/3. (I think.)

Cheers,
Ellen

Seamanship Question #32
 

Ellen MacArthur wrote:

Rule of thirds works for tide height. In the first two hours it goes down 1/3 of its height.
In the next two hours it goes down 1/3 more and in the last two hours it goes down the last
1/3. (I think.)


Wrong.

Joe

Seamanship Question #32
 

"Ellen MacArthur" wrote
| Rule of thirds works for tide height. In the first two hours it goes down 1/3 of its height.
| In the next two hours it goes down 1/3 more and in the last two hours it goes down the last
| 1/3. (I think.)

Oops! That doesn't sound right. Maybe it goes down 1/4 the first two hours and 1/2 the next
two hours and 1/4 the last two hours. Yes, that's it. Makes more sense that way. It goes down
faster in the middle hours.

Cheers,
Ellen

Seamanship Question #32
 

Ellen MacArthur wrote:
"Ellen MacArthur" wrote
| Rule of thirds works for tide height. In the first two hours it goes down 1/3 of its height.
| In the next two hours it goes down 1/3 more and in the last two hours it goes down the last
| 1/3. (I think.)

Oops! That doesn't sound right. Maybe it goes down 1/4 the first two hours and 1/2 the next
two hours and 1/4 the last two hours. Yes, that's it. Makes more sense that way. It goes down
faster in the middle hours.

Bwahahahaha lubber!

Joe

Cheers,
Ellen

Seamanship Question #32
 

"Joe" wrote |
| Wrong.

Maybe your right, Mr. Farmer (sign of respect (-:) Explain how the rule of 12 works.
That's probably what I was thinking. The rule of 1/3 maybe is more for photography.

Cheers,
Ellen

Seamanship Question #32
 

"Joe" wrote


| Bwahahahaha lubber!

OK! You got me. Your not a farmer. (blush, I guess I blew my sailing test debut)

Cheers,
Ellen

Seamanship Question #32
 

Ellen MacArthur wrote:

OK! You got me. Your not a farmer. (blush, I guess I blew my sailing
test debut)

For someone that moans about lack of sailing content in what is widely seen
as a virtual yacht club bar (where the patrons also talk about stuff other
than sailing), you have a lot to yet contribute.

The clue is in the 12ths part...

hour change as a fraction of tidal range
1 1/12
2 2/12
3 3/12
4 3/12
5 2/12
6 1/12

Say the tide drops 5" over the first hour. Since you know that that 5" is
one twelfth of the total range, you can calculate that the tide will have
dropped 5"x12 = 60" = 5 feet when it gets to low water. Of course, 5' is a
girly tidal range. Here, it's a proper, manly 5 metres (or more).


--
Capt Scumbalino

Seamanship Question #32
 

"Capt. Scumbalino" wrote

| The clue is in the 12ths part...
|
| hour change as a fraction of tidal range
| 1 1/12
| 2 2/12
| 3 3/12
| 4 3/12
| 5 2/12
| 6 1/12

Thanks for the explanation. So what's the difference between the rule of 12ths
and the rule of thirds. In the rule of thirds the first two hours it goes down 1/4
which is the same as your 3/12th. The second two hours it goes down 1/2 which is the
same as your 6/12th and the third two hours it goes down 1/4 which is the same as
your 3/12th. See I got it right in spite of myself.

Not a lubber, not a lubber, not a lubber... Yippee!

Cheers,
Ellen

Seamanship Question #32
 

Wrong.

Rule of 12's applies.

Ifyou want to break it down into 2 hours portions it works out like
this:
First two hours it goes down 1/4, middle two hours is 1/2, last twohours is
1/4.

"Ellen MacArthur" wrote in message
reenews.net...

"Joe" wrote
| Wrong...another lubber I see. The rule of thirds is fo tital stream
| flows .
|
| For height you use the rule of 12.

Don't EVER call this girl a lubber, you farmer! :-)

Rule of thirds works for tide height. In the first two hours it goes down
1/3 of its height.
In the next two hours it goes down 1/3 more and in the last two hours it
goes down the last
1/3. (I think.)

Cheers,
Ellen

Seamanship Question #32
 

The point I wanted to make you covered. 1 point to Capt
Scumbalino.

If the range of tide is 8 feet, the first hour is 8".

For a six hour cycle, Multiply by twelve to get inches and
divide by 12 to get 1/12.

It is easier to simply check the range of tide and change
the units to inches.


"Capt. Scumbalino" wrote

Ellen MacArthur wrote:

OK! You got me. Your not a farmer. (blush, I guess I blew my sailing
test debut)

For someone that moans about lack of sailing content in what is widely
seen
as a virtual yacht club bar (where the patrons also talk about stuff other
than sailing), you have a lot to yet contribute.

The clue is in the 12ths part...

hour change as a fraction of tidal range
1 1/12
2 2/12
3 3/12
4 3/12
5 2/12
6 1/12

Say the tide drops 5" over the first hour. Since you know that that 5" is
one twelfth of the total range, you can calculate that the tide will have
dropped 5"x12 = 60" = 5 feet when it gets to low water. Of course, 5' is a
girly tidal range. Here, it's a proper, manly 5 metres (or more).


--
Capt Scumbalino

Seamanship Question #32
 

"Bart Senior" .@. wrote in message ...
| Wrong.
|
| Rule of 12's applies.
|
| Ifyou want to break it down into 2 hours portions it works out like
| this:
| First two hours it goes down 1/4, middle two hours is 1/2, last twohours is
| 1/4.

I corrected myself when I answered 'farmer' Joe. :-0~ I wrote it down just
like you said after realizing how dumb the 1/3, 1/3, 1/3 thing looked. Duh!

Ask some more questions. I'll get the next one right. For sure. That one threw
me off for some reason.

Cheers,
Ellen

Seamanship Question #32
 

Bart Senior wrote:
The point I wanted to make you covered. 1 point to Capt
Scumbalino.

NO FAIR! I said rules of 12 first, gimme my point you Scurvey dog!

Joe




If the range of tide is 8 feet, the first hour is 8".

For a six hour cycle, Multiply by twelve to get inches and
divide by 12 to get 1/12.

It is easier to simply check the range of tide and change
the units to inches.


"Capt. Scumbalino" wrote

Ellen MacArthur wrote:

OK! You got me. Your not a farmer. (blush, I guess I blew my sailing
test debut)

For someone that moans about lack of sailing content in what is widely
seen
as a virtual yacht club bar (where the patrons also talk about stuff other
than sailing), you have a lot to yet contribute.

The clue is in the 12ths part...

hour change as a fraction of tidal range
1 1/12
2 2/12
3 3/12
4 3/12
5 2/12
6 1/12

Say the tide drops 5" over the first hour. Since you know that that 5" is
one twelfth of the total range, you can calculate that the tide will have
dropped 5"x12 = 60" = 5 feet when it gets to low water. Of course, 5' is a
girly tidal range. Here, it's a proper, manly 5 metres (or more).


--
Capt Scumbalino

Seamanship Question #32
 

While the Rule of 12ths is a very handy tool for estimating the tide
height at any point in the cycle, I would be very careful of using to
extrapolate total range from one hour's observation. For instance, if
your observation were off by one inch, then you might mis-estimate the
full range by a foot.

On a related topic, sometimes people will claim that the Rule of 12ths
also applies to current estimation. This is generally not true.
The strength of the current through the cycle is highly dependent on
the local geography. In particular, the strong currents that are
generated by tidal differences on connected bodies of water (Hell
Gate, Cape Cod Canal, etc.) ramp up very quickly and their chart is
more of a square wave, than a sine.



Bart Senior wrote:
The point I wanted to make you covered. 1 point to Capt
Scumbalino.

If the range of tide is 8 feet, the first hour is 8".

For a six hour cycle, Multiply by twelve to get inches and
divide by 12 to get 1/12.

It is easier to simply check the range of tide and change
the units to inches.


"Capt. Scumbalino" wrote

Ellen MacArthur wrote:

OK! You got me. Your not a farmer. (blush, I guess I blew my sailing
test debut)
For someone that moans about lack of sailing content in what is widely
seen
as a virtual yacht club bar (where the patrons also talk about stuff other
than sailing), you have a lot to yet contribute.

The clue is in the 12ths part...

hour change as a fraction of tidal range
1 1/12
2 2/12
3 3/12
4 3/12
5 2/12
6 1/12

Say the tide drops 5" over the first hour. Since you know that that 5" is
one twelfth of the total range, you can calculate that the tide will have
dropped 5"x12 = 60" = 5 feet when it gets to low water. Of course, 5' is a
girly tidal range. Here, it's a proper, manly 5 metres (or more).


--
Capt Scumbalino

Seamanship Question #32
 

I'll give you 1/2 a point, because you did not explain how
it worked.

"Joe" wrote in message
oups.com...

Bart Senior wrote:
The point I wanted to make you covered. 1 point to Capt
Scumbalino.

NO FAIR! I said rules of 12 first, gimme my point you Scurvey dog!

Joe

Seamanship Question #32
 

Good point Jeff.

"Jeff" wrote

While the Rule of 12ths is a very handy tool for estimating the tide
height at any point in the cycle, I would be very careful of using to
extrapolate total range from one hour's observation. For instance, if
your observation were off by one inch, then you might mis-estimate the
full range by a foot.

On a related topic, sometimes people will claim that the Rule of 12ths
also applies to current estimation. This is generally not true. The
strength of the current through the cycle is highly dependent on the local
geography. In particular, the strong currents that are generated by tidal
differences on connected bodies of water (Hell Gate, Cape Cod Canal, etc.)
ramp up very quickly and their chart is more of a square wave, than a
sine.

Seamanship Question #32
 

Ellen MacArthur wrote:

Thanks for the explanation. So what's the difference between the
rule of 12ths and the rule of thirds. In the rule of thirds the first
two hours it goes down 1/4 which is the same as your 3/12th. The
second two hours it goes down 1/2 which is the same as your 6/12th
and the third two hours it goes down 1/4 which is the same as your
3/12th. See I got it right in spite of myself.

It's based on the pretty-much universal fact that the time for the tide to
change from high to low water, and vice-versa, is pretty close to six hours.
Since we humans deal with time in chunks of one hour, the question we ask
is: "how much does the tide change in one hour?". Since the smallest
fraction is one twelfth, just before and just after slack water, it's
natural to refer to the tidal change during other hours in terms of the same
denominator. One twelfth in the first hour leads us to express the change
during the second as two twelfths, etc.

Also, the larger the time slot, the greater the granularity. Imagine you're
waiting for the tide to rise enough to clear a sandbar. The rule of thirds
would have you waiting in chunks of two hours before you sail. The rule of
12ths would keep you at anchor for chunks of one hour. Of course, plot the
heights on a graph over time, and you can pinpoint your departure time
(rather, the time at which you can safely cross the sandbar) much more
finely.

Whilst your 'rule of thirds' (which, incidentally, isn't exclusive to
photography, but is a general principle used in many forms of visual art)
may be mathematically correct at its junctures, it doesn't fit with how
people think of time (ie, we think in days of 24 hours, not days of 12
bi-hours).


--
Capt Scumbalino

Seamanship Question #32
 

Bart Senior wrote:
I'll give you 1/2 a point, because you did not explain how
it worked.


I was busy givin the lubber more rope to hang herself.

If you do not give me a full point I will file a protest... and request
the ASA points commitee to rule on this matter.

Joe


"Joe" wrote in message
oups.com...

Bart Senior wrote:
The point I wanted to make you covered. 1 point to Capt
Scumbalino.

NO FAIR! I said rules of 12 first, gimme my point you Scurvey dog!

Joe

Seamanship Question #32
 

Joe wrote:

I was busy givin the lubber more rope to hang herself.

If you do not give me a full point I will file a protest... and
request the ASA points commitee to rule on this matter.

You should know by now that Bart's points are hard to win. You were lucky
not to taste the cat'o'nine for such a half-assed answer. You'll be luckier
still not to have the half point deducted for making waves with the
committee. Still, the lubber could have been in danger of getting keelhauled
for that rule of 3rds nonsense...


--
Capt Scumbalino

Seamanship Question #32
 

Joe wrote:
Bart Senior wrote:
I'll give you 1/2 a point, because you did not explain how
it worked.


I was busy givin the lubber more rope to hang herself.

If you do not give me a full point I will file a protest... and request
the ASA points commitee to rule on this matter.

Joe


"Joe" wrote in message
oups.com...
Bart Senior wrote:
The point I wanted to make you covered. 1 point to Capt
Scumbalino.
NO FAIR! I said rules of 12 first, gimme my point you Scurvey dog!

Joe

We gonna have a duel at dusk?

Seamanship Question #32
 

Jeff wrote:

While the Rule of 12ths is a very handy tool for estimating the tide
height at any point in the cycle, I would be very careful of using to
extrapolate total range from one hour's observation. For instance, if
your observation were off by one inch, then you might mis-estimate the
full range by a foot.

I'd agree with that. The way I read the question, I took it that the only
information available was what could be observed over the next hour, hence
the extrapolation. I'd much rather know the tidal range and work from big to
small. :-)


--
Capt Scumbalino

Seamanship Question #32
 

Everybody should read your post...

Very erudite of you, Capt. And you didn't lose your temper. And you didn't call
me names. Your a good example for how newsgroup discussion should be done.

Cheers,
Ellen



"Capt. Scumbalino" wrote in message ...
| Ellen MacArthur wrote:
|
| Thanks for the explanation. So what's the difference between the
| rule of 12ths and the rule of thirds. In the rule of thirds the first
| two hours it goes down 1/4 which is the same as your 3/12th. The
| second two hours it goes down 1/2 which is the same as your 6/12th
| and the third two hours it goes down 1/4 which is the same as your
| 3/12th. See I got it right in spite of myself.
|
| It's based on the pretty-much universal fact that the time for the tide to
| change from high to low water, and vice-versa, is pretty close to six hours.
| Since we humans deal with time in chunks of one hour, the question we ask
| is: "how much does the tide change in one hour?". Since the smallest
| fraction is one twelfth, just before and just after slack water, it's
| natural to refer to the tidal change during other hours in terms of the same
| denominator. One twelfth in the first hour leads us to express the change
| during the second as two twelfths, etc.
|
| Also, the larger the time slot, the greater the granularity. Imagine you're
| waiting for the tide to rise enough to clear a sandbar. The rule of thirds
| would have you waiting in chunks of two hours before you sail. The rule of
| 12ths would keep you at anchor for chunks of one hour. Of course, plot the
| heights on a graph over time, and you can pinpoint your departure time
| (rather, the time at which you can safely cross the sandbar) much more
| finely.
|
| Whilst your 'rule of thirds' (which, incidentally, isn't exclusive to
| photography, but is a general principle used in many forms of visual art)
| may be mathematically correct at its junctures, it doesn't fit with how
| people think of time (ie, we think in days of 24 hours, not days of 12
| bi-hours).
|
|
| --
| Capt Scumbalino
|
|
|

Seamanship Question #32
 

"Joe" wrote
| If you do not give me a full point I will file a protest... and request
| the ASA points commitee to rule on this matter.

Give 'farmer' Joe ALL the points. He was right and posted first. Be fair.
Capt. Scumbalino's answer was more complete but it was the same. Actually,
give them each half the points.

Cheers,
Ellen

Seamanship Question #32
 

Ellen MacArthur wrote:
"Joe" wrote
| If you do not give me a full point I will file a protest... and request
| the ASA points commitee to rule on this matter.

Give 'farmer' Joe ALL the points. He was right and posted first. Be fair.
Capt. Scumbalino's answer was more complete but it was the same. Actually,
give them each half the points.

Cheers,
Ellen

....you have not been here long enough to have a say.

Sorry

Joe

Seamanship Question #32
 

"Joe" wrote
| ...you have not been here long enough to have a say.

Biting the hand that's feeding ya? Doh!
You've a lot to learn about women, Joe. We're entitled to a say any old time.
That's what we do best, ya know. (well, second best, wink wink!)

Cheers,
Ellen

Seamanship Question #32
 

Bull. He one of the worst examples. If he happens to occasionally say
something useful, it's mostly drowned out by his other common behavior. We
don't need any more sockpuppets, certainly not like him.

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

"Ellen MacArthur" wrote in message
reenews.net...
Everybody should read your post...

Very erudite of you, Capt. And you didn't lose your temper. And you
didn't call
me names. Your a good example for how newsgroup discussion should be done.

Cheers,
Ellen



"Capt. Scumbalino" wrote in message
...
| Ellen MacArthur wrote:
|
| Thanks for the explanation. So what's the difference between the
| rule of 12ths and the rule of thirds. In the rule of thirds the first
| two hours it goes down 1/4 which is the same as your 3/12th. The
| second two hours it goes down 1/2 which is the same as your 6/12th
| and the third two hours it goes down 1/4 which is the same as your
| 3/12th. See I got it right in spite of myself.
|
| It's based on the pretty-much universal fact that the time for the tide
to
| change from high to low water, and vice-versa, is pretty close to six
hours.
| Since we humans deal with time in chunks of one hour, the question we
ask
| is: "how much does the tide change in one hour?". Since the smallest
| fraction is one twelfth, just before and just after slack water, it's
| natural to refer to the tidal change during other hours in terms of the
same
| denominator. One twelfth in the first hour leads us to express the
change
| during the second as two twelfths, etc.
|
| Also, the larger the time slot, the greater the granularity. Imagine
you're
| waiting for the tide to rise enough to clear a sandbar. The rule of
thirds
| would have you waiting in chunks of two hours before you sail. The rule
of
| 12ths would keep you at anchor for chunks of one hour. Of course, plot
the
| heights on a graph over time, and you can pinpoint your departure time
| (rather, the time at which you can safely cross the sandbar) much more
| finely.
|
| Whilst your 'rule of thirds' (which, incidentally, isn't exclusive to
| photography, but is a general principle used in many forms of visual
art)
| may be mathematically correct at its junctures, it doesn't fit with how
| people think of time (ie, we think in days of 24 hours, not days of 12
| bi-hours).
|
|
| --
| Capt Scumbalino
|
|
|

Seamanship Question #32
 

I say give him his point. He needs them wherever he can get them. :-)

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

"Joe" wrote in message
oups.com...

Bart Senior wrote:
I'll give you 1/2 a point, because you did not explain how
it worked.


I was busy givin the lubber more rope to hang herself.

If you do not give me a full point I will file a protest... and request
the ASA points commitee to rule on this matter.

Joe


"Joe" wrote in message
oups.com...

Bart Senior wrote:
The point I wanted to make you covered. 1 point to Capt
Scumbalino.

NO FAIR! I said rules of 12 first, gimme my point you Scurvey dog!

Joe

Seamanship Question #32
 

ASA point? :-)

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

"Bart Senior" .@. wrote in message ...
Good point Jeff.

"Jeff" wrote

While the Rule of 12ths is a very handy tool for estimating the tide
height at any point in the cycle, I would be very careful of using to
extrapolate total range from one hour's observation. For instance, if
your observation were off by one inch, then you might mis-estimate the
full range by a foot.

On a related topic, sometimes people will claim that the Rule of 12ths
also applies to current estimation. This is generally not true. The
strength of the current through the cycle is highly dependent on the
local geography. In particular, the strong currents that are generated
by tidal differences on connected bodies of water (Hell Gate, Cape Cod
Canal, etc.) ramp up very quickly and their chart is more of a square
wave, than a sine.

Seamanship Question #32
 

Ellen MacArthur wrote:
"Joe" wrote
| ...you have not been here long enough to have a say.

Biting the hand that's feeding ya? Doh!
You've a lot to learn about women, Joe. We're entitled to a say any old time.
That's what we do best, ya know. (well, second best, wink wink!)

Cheers,
Ellen

I will not sell out for all the asa points on earth.

Whats right is right.

Joe

Seamanship Question #32
 

Ellen MacArthur wrote:


Very erudite of you,

Katy is that you?

Joe

Seamanship Question #32
 

Very risky to try to estimate the range like that. You will find it
difficult to correct for barometric pressure, and also you need to be sure
you are not in a place where the (very useful) rule of 12 does not work. For
example, in UK the tides in the Solent do not follow the rule. There you get
a 'stand' of high water because the tide coming in fom the English channel
comes straight in from the west to form the first high water and a little
later after going round the Isle of Wight it comes in again from the east to
hold the level up.
Don't they publish tidal charts for ports in USA?
"Jeff" wrote in message
. ..
While the Rule of 12ths is a very handy tool for estimating the tide
height at any point in the cycle, I would be very careful of using to
extrapolate total range from one hour's observation. For instance, if
your observation were off by one inch, then you might mis-estimate the
full range by a foot.

On a related topic, sometimes people will claim that the Rule of 12ths
also applies to current estimation. This is generally not true.
The strength of the current through the cycle is highly dependent on
the local geography. In particular, the strong currents that are
generated by tidal differences on connected bodies of water (Hell
Gate, Cape Cod Canal, etc.) ramp up very quickly and their chart is
more of a square wave, than a sine.



Bart Senior wrote:
The point I wanted to make you covered. 1 point to Capt
Scumbalino.

If the range of tide is 8 feet, the first hour is 8".

For a six hour cycle, Multiply by twelve to get inches and
divide by 12 to get 1/12.

It is easier to simply check the range of tide and change
the units to inches.


"Capt. Scumbalino" wrote

Ellen MacArthur wrote:

OK! You got me. Your not a farmer. (blush, I guess I blew my sailing
test debut)
For someone that moans about lack of sailing content in what is widely
seen
as a virtual yacht club bar (where the patrons also talk about stuff
other
than sailing), you have a lot to yet contribute.

The clue is in the 12ths part...

hour change as a fraction of tidal range
1 1/12
2 2/12
3 3/12
4 3/12
5 2/12
6 1/12

Say the tide drops 5" over the first hour. Since you know that that 5"
is
one twelfth of the total range, you can calculate that the tide will
have
dropped 5"x12 = 60" = 5 feet when it gets to low water. Of course, 5'
is a
girly tidal range. Here, it's a proper, manly 5 metres (or more).


--
Capt Scumbalino

Seamanship Question #32
 

Capt. JG wrote:
ASA point? :-)


Yeah, win enough of them and you, too, can vacation at Paul Fortin's
home in the Bronx....

Seamanship Question #32
 

Joe wrote:
Ellen MacArthur wrote:

Very erudite of you,

Katy is that you?

Joe

Nope...have never played the sock puppet game....

Seamanship Question #32
 

Edgar wrote: Don't they publish tidal charts for ports in USA?

Yes, they do. We have wind driven tides where we are, so unless you're
going way out into the Sounds, you're better off knowing what the
weather's doing than what the tide chart says.

Seamanship Question #32
 

I heard he has a very big guest house.

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

"katy" wrote in message
...
Capt. JG wrote:
ASA point? :-)


Yeah, win enough of them and you, too, can vacation at Paul Fortin's home
in the Bronx....

Seamanship Question #32
 

Capt. JG wrote:
I heard he has a very big guest house.

Vinnie's Garage and Cement Contractor's?

Seamanship Question #32
 

Capt. Scumbalino wrote:

It's based on the pretty-much universal fact that the time for the tide to
change from high to low water, and vice-versa, is pretty close to six hours.

Universal, if your universe consists of only places with semi-diurnal
tides. That's the majority, granted, but not everywhere has
semi-diurnal tides.

You might want to get out more.

//Walt

Seamanship Question #32
 

Walt wrote:
Capt. Scumbalino wrote:

It's based on the pretty-much universal fact that the time for the
tide to change from high to low water, and vice-versa, is pretty
close to six hours.

Universal, if your universe consists of only places with semi-diurnal
tides. That's the majority, granted, but not everywhere has
semi-diurnal tides.

You might want to get out more.

You might want to try and comprehend the qualifier "pretty-much".


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Capt Scumbalino