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The Moon and the Lizard.

This fascinating series is a combination of historical seafaring, swashbuckling adventure, and high technological science-fiction. Join us in a discussion!
Re: The Moon and the Lizard.
Post by EdThomas   » Sun Oct 12, 2014 10:04 pm

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Philip Stanley wrote:The point I was trying to make earlier in this post is that the throat is so narrow, relative to the enormous volume of Howell Bay, that not enough water can flow in during high tide on the Charis Sea, or out during low tide on the Charis sea, to change the level of Howell bay by more than an inch or two. Hence, no significant tide in Howell Bay!
However, if the omnipotent Jogger with Stalked Vegetables chooses to assert that significant tides occur in Tellesberg, who are we to question him. We are obviously deficient in our understanding of the dynamics of tides, ALAS!

Did some googling and learned the Mediterranean and Baltic Seas have very low tides. The articles I found said this comes from the very small size of the openings to the Atlantic. The Med's interesting cuz it has an "in" current at the top of Gibraltar and an "out" current at the bottom.

Howell Bay has a narrow opening in western end the Throat but more importantly IMHO is the very shallow section to the east. It almost looks like a river delta. Soooo...Howell Bay may indeed have no tides or very small tides if any. I'd say Howell Bay is similar to the Baltic
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Re: The Moon and the Lizard.
Post by InvisibleBison   » Sun Oct 12, 2014 11:45 pm

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We don't actually know that Tellesburg has any significant tides. There is that reference about not missing the tides when Cayleb is leaving to invade Corisande, but he wasn't being dead serious at the moment. It could well be that the sailors of the ICN would be annoyed about missing the tide simply because sailing with the tide is traditional, not because of any actual benefits to doing so when leaving Tellesburg.
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Re: The Moon and the Lizard.
Post by Weird Harold   » Mon Oct 13, 2014 2:08 am

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EdThomas wrote:
Philip Stanley wrote:The point I was trying to make earlier in this post is that the throat is so narrow, relative to the enormous volume of Howell Bay, that not enough water can flow in during high tide on the Charis Sea, or out during low tide on the Charis sea, to change the level of Howell bay by more than an inch or two. Hence, no significant tide in Howell Bay!


Howell Bay has a narrow opening in western end the Throat but more importantly IMHO is the very shallow section to the east. It almost looks like a river delta. Soooo...Howell Bay may indeed have no tides or very small tides if any. I'd say Howell Bay is similar to the Baltic


Everyone seems to be ignoring the topography of the various points of interest. IIRC, the Bay of Fundy has such extreme tides because the configuration of the bottom of the bay. I don't recall the particulars, but it is something like a deep entrance and rapid shelving to shore that causes the extreme tides.

In the case of Safehold, a narrow but deep entrance will pass the same amount of tidal flow as a wide but shallow entrance of the same cross-sectional area. (EG a ten-meter wide by one-meter deep passage will pass the same amount of water as a one-meter wide by ten-meter deep passage.) At least in theory; I know that tides don't always use the entire passage and water flows at different rates at different depths and bottom conditions.

Without knowing the depth of any given passage, we can't make any valid assumptions about the amount of tidal flow that will be allowed. Even then, it would require detailed knowledge of the bottom topography to determine the effects of turbulence and resistance.
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Answers! I got lots of answers!

(Now if I could just find the right questions.)
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Re: The Moon and the Lizard.
Post by runsforcelery   » Mon Oct 13, 2014 5:45 am

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Weird Harold wrote:
EdThomas wrote:The point I was trying to make earlier in this post is that the throat is so narrow, relative to the enormous volume of Howell Bay, that not enough water can flow in during high tide on the Charis Sea, or out during low tide on the Charis sea, to change the level of Howell bay by more than an inch or two. Hence, no significant tide in Howell Bay!


Philip Stanley wrote:Howell Bay has a narrow opening in western end the Throat but more importantly IMHO is the very shallow section to the east. It almost looks like a river delta. Soooo...Howell Bay may indeed have no tides or very small tides if any. I'd say Howell Bay is similar to the Baltic


Everyone seems to be ignoring the topography of the various points of interest. IIRC, the Bay of Fundy has such extreme tides because the configuration of the bottom of the bay. I don't recall the particulars, but it is something like a deep entrance and rapid shelving to shore that causes the extreme tides.

In the case of Safehold, a narrow but deep entrance will pass the same amount of tidal flow as a wide but shallow entrance of the same cross-sectional area. (EG a ten-meter wide by one-meter deep passage will pass the same amount of water as a one-meter wide by ten-meter deep passage.) At least in theory; I know that tides don't always use the entire passage and water flows at different rates at different depths and bottom conditions.

Without knowing the depth of any given passage, we can't make any valid assumptions about the amount of tidal flow that will be allowed. Even then, it would require detailed knowledge of the bottom topography to determine the effects of turbulence and resistance.



Tides are much more complex phenomena than most people (I speak of the population in general, of course, not the brilliant individuals who read my books :ugeek: :lol: ) think. The location of a given spot in terms of latitude can have a significant effect; so (as has been pointed out) can the constriction (or lack thereof) of a narrow passage connecting a given body of water to a larger body of water. Virtually any body of water large enough to be called a "sea," however, will have at least some tide, even though it may be measured in single-digit inches. Some examples have already been given in earlier posts on this thread. The rise and fall of the tide in Shwei Bay and Howell Bay are much smaller than those of the Great Western Ocean, for example, but they do exist. And, yes, the Throat and the Shweimouth Passage are both going to be lively places, although nowhere near up to Bay of Fundy standards, both the Gulf of Dohlar and the Sea of Charis have relatively low tidal ranges. The Throat is 58 miles wide at Lock Island (approximately equal to the Bay of Fundy's entire width) and exceptionally deep at its western end at the Bay of Howell, where width drops to only about 20 miles. Thus what Ed has called the "tidal current" is strong but not exactly overwhelming at either point along the passage and there is no equivalent of the Bay of Fundy's tidal bores. And, as he has also pointed out, you can only get so much water through a given opening, no matter how fierce the current, which also helps to account for the low tides on Shwei Bay and Howell Bay. There simply isn't enough water exchange to drive a heavy tide in either location, irrespective of the tides in the Sea of Charis and the Gulf of Dohlar.

Yes, tides exist on Howell Bay. Yes, really canny seamen will try to take advantage of even gentle tides. And, yes, Cayleb was making a joke with Sharley in an effort to diffuse some of the intense emotion both of them were feeling at the moment.

There is actually a point in HFQ where this entire issue of tides and tidal ranges is addressed and plays a major role in the action. Further than that deponent saith no more. :twisted:

BTW: Hope I got the attributions right when I spread out the quotes! ;)


"Oh, bother!" said Pooh, as Piglet came back from the dead.
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Re: The Moon and the Lizard.
Post by Tim   » Mon Oct 13, 2014 6:40 am

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So RFC where do you stand on major ocean currents on Safehold?

It would appear the only world class current on par with the Gulfstream or Japanese Current would occur in the southern hemisphere with a circular flow through Carter’s Ocean and the southern Great Western Ocean.

There would be other local currents but they would not have the scale and strength to be major heat pumps.

runsforcelery wrote:Tides are much more complex phenomena than most people (I speak of the population in general, of course, not the brilliant individuals who read my books :ugeek: :lol: ) think. The location of a given spot in terms of latitude can have a significant effect; so (as has been pointed out) can the constriction (or lack thereof) of a narrow passage connecting a given body of water to a larger body of water. Virtually any body of water large enough to be called a "sea," however, will have at least some tide, even though it may be measured in single-digit inches. Some examples have already been given in earlier posts on this thread. The rise and fall of the tide in Shwei Bay and Howell Bay are much smaller than those of the Great Western Ocean, for example, but they do exist. And, yes, the Throat and the Shweimouth Passage are both going to be lively places, although nowhere near up to Bay of Fundy standards, both the Gulf of Dohlar and the Sea of Charis have relatively low tidal ranges. The Throat is 58 miles wide at Lock Island (approximately equal to the Bay of Fundy's entire width) and exceptionally deep at its western end at the Bay of Howell, where width drops to only about 20 miles. Thus what Ed has called the "tidal current" is strong but not exactly overwhelming at either point along the passage and there is no equivalent of the Bay of Fundy's tidal bores. And, as he has also pointed out, you can only get so much water through a given opening, no matter how fierce the current, which also helps to account for the low tides on Shwei Bay and Howell Bay. There simply isn't enough water exchange to drive a heavy tide in either location, irrespective of the tides in the Sea of Charis and the Gulf of Dohlar.

Yes, tides exist on Howell Bay. Yes, really canny seamen will try to take advantage of even gentle tides. And, yes, Cayleb was making a joke with Sharley in an effort to diffuse some of the intense emotion both of them were feeling at the moment.

There is actually a point in HFQ where this entire issue of tides and tidal ranges is addressed and plays a major role in the action. Further than that deponent saith no more. :twisted:

BTW: Hope I got the attributions right when I spread out the quotes! ;)
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Re: The Moon and the Lizard.
Post by kbus888   » Mon Oct 13, 2014 6:40 am

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=2014/10/13=
Thank you RFC for the tides information.

As a matter of interest (interest to me anyhow) I and my family actually saw the reverse flow of the St John river
in New Brunswick on our trip around the eastern coast.

I was impressed to see the darned river flowing the wrong way :o

That was in 1976, actually ...

Editted 1 time for typos corrections

R
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..//* *\\
(/(..^..)\)
.._/'*'\_
.(,,,)^(,,,)

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the happiness of another
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Re: The Moon and the Lizard.
Post by Tanstaafl   » Mon Oct 13, 2014 10:27 am

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runsforcelery wrote:
There is actually a point in HFQ where this entire issue of tides and tidal ranges is addressed and plays a major role in the action. Further than that deponent saith no more. :twisted:



The place I expect strong tidal effects is at Silk Town. At the end of a funnel after a large stretch of open ocean.

But why would there be any action at Silt Town? :twisted:
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Re: The Moon and the Lizard.
Post by EdThomas   » Mon Oct 13, 2014 10:46 am

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kbus888 wrote:=2014/10/13=
Thank you RFC for the tides information.

As a matter of interest (interest to me anyhow) I and my family actually saw the reverse flow of the St John river
in New Brunswick on our trip around the eastern coast.

I was impressed to see the darned river flowing the wrong way :o

That was in 1976, actually ...

Editted 1 time for typos corrections

R
.

The truly awesome thing here is that it's happened every day for the last 38 years and it'll happen every day long after you and I are gone :) :)
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Re: The Moon and the Lizard.
Post by EdThomas   » Mon Oct 13, 2014 10:52 am

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Tim wrote:So RFC where do you stand on major ocean currents on Safehold?

It would appear the only world class current on par with the Gulfstream or Japanese Current would occur in the southern hemisphere with a circular flow through Carter’s Ocean and the southern Great Western Ocean.

There would be other local currents but they would not have the scale and strength to be major heat pumps.
SNIP

I believe just about every discussion of climate makes some reference to the presence, or lack of, of ocean currents in the factors determining an areas climate. I'd do a text search onthe kindle but It's not with me now.
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Re: The Moon and the Lizard.
Post by EdThomas   » Mon Oct 13, 2014 12:12 pm

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Some comments on "Catching the Tide"
The first thing you have to know is sail-powered commercial carriers are SLOW!!with the possible exception of the tea clippers. First guy back got the highest price.
Two factors - speed and direction. Assume a 1 knot current and 6 hours between high and low tide.
Speed - Galleons (think big fat tubs)probably moved at 3-4 knots in harbor. They may have reached 7-8 knots out in the open. In the harbor where things are crowded and they don't have much sail up, they're slow. The outgoing tide, usually the ebb, is going to increase their speeds. Remember the rule of 12ths. For the first and last 2 hours they'll get 1/2 knot or 2 miles and for the third and 4th hours they'll get 2 more miles. This extra 4 miles, or hour of sailing might mean the difference of getting out of the harbor.

Direction is a bit more complicated. For the most part, the ebbing and rising tide will cause water to move straight in and out of a harbor. The navigable channel for large boats may not be straight into a harbor (it seems like they never are to this sailor :) ). Where the tidal flow is across the channel, the boat's movement will be crab-like with two vectors, the forward from sails and rudder and the lateral from the cross flow of the tide. Navigation in a curvy channel can be interesting, which is why sailors prefer their curves on women.

Changes in depth will also affect the speed of the tidal current. Moving into a shallower portion of the channel will increase the speed of the current and vice versy.
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