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A Docking Dilemma

Creed

Sage
In one of my worlds there are five moons for the planet. Along with important theological/philosophical changes to the evolution of the cultures on the planet, there are obviously physical changes- i.e. storms and tides.
The important one right now is the tides. Due to the intensity of the tidal shifts and the general increase in naval danger trading from the continents of Ghalab and Jenedon-across-the-sea is very expensive.
Firstly, what is a reasonable height that the waters can rise? Secondly, with ocean levels rising and falling with the tide, how can I make an effective harbour?
The thought of a floating dock crossed my mind, but only that. It seems a little far-fetched in my world for it to be magical (especially since the culture hates magic) and I'm not sure how it would work otherwise.
A more realistic idea that I think is better is having a stone harbour with several tiers on it, so that way when a ship comes in can make it to the harbour, and there should be a tier that is relatively close to its level where it can dock. They might have to wait a little while before they can safely get cargo off, though.
Any different ideas for making an effective dock in this tidal world?*Any problems (and possible fixes) for what I proposed?
 

Saigonnus

Auror
I imagine an elevated docking area. Likely the city would be elevated to a point where even at high tide they won't be inundated, it would stand to reason the docks would be at the same level as the city and you could have floating piers attached to the side of the dock main structure, built so they can slide up and down freely (like a piston) and secured to the dock, but still maintain enough strength so passengers or cargo can use it. When it's in the lowest positions, booms could be attached to the dock to off-load the cargo below and simple stairs could give the passengers access to the city above.

The tiered approach could work as well, but the depth between each one would have to be sufficient enough to accommodate even the deepest drafted ships (most cargo ships) on any level. Just one issue that comes to mind are those ships that are berthed for a long while, whichever system you use would have to accommodate the lower or raising of the tide with the ships in place; probably not something a tiered system could do since they'd likely be a solid construction.

Side note: If I was going to build a harbor in such a place, I would have a natural or man-made seawall out in the bay, directly opposite the docks with entrances both right and left. That would protect from the most violent direct waves, the rising and falling of the water level would be more passive.
 
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Creed

Sage
A very useful post, Saigonnus! Thank you!
I see what you mean about the issue with the solid structure, and how it wouldn't be able to adjust to the different height. That was one problem I had, and I realised that a ship would simply have to wait until the tide brought it to whichever tier was closest to its level.
The seawall was something I never really thought of. Nevertheless, I reasoned with something similar; the idea of having the harbours elevated rather high, with walls to prevent storms from causing too much damage to the harbours. But a seawall's something that could be a very useful addition to the system.
For the elevated piers I'm thinking that's my best bet. It seems a pretty good system. But I have some questions: I'm assuming they are made of wood to allow them to float freely. If these ships bring in a lot of cargo (spices, fruits, ores, etc.) how thick would these platforms have to be to maintain the weight of these products and keep them afloat? And to get the cargo up, would they simply wait until high tide, or perhaps use some form of crane (that might be a little advanced, I'm not sure)? If they cannot get the cargo up in a quick fashion, what precautions (if any- is it just a danger of the trade?) would they have in place to get the cargo to safety if a storm hit while cargo is still on the platforms? I suppose the seawalls would mitigate the danger slightly, but not all of the harbour cities can have seawalls and even if they do, they cannot be certain of the cargo's safety.
 
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ThinkerX

Myth Weaver
Twenty foot tides are the norm in my part of the world.

Basically, you want your actual wharfs in an area where the water is as deep as possible as close to shore as possible.

As to the changing height...envision long ramps that 'pivot' at either end.

In my younger days, I spent some time on a sea floating monstrosity termed 'Derrick Barge 100' (which had apparently been the hangout of an LA street gang prior to being deployed to Alaska). The deck for this thing was 'mounted' on a number of vertical metal cylinders, which were filled with either air or water, depending on how close to the surface the bosses wanted it to be. I usually hand to walk up about 200 steps after finishing a 12 hour shift.
 

Saigonnus

Auror
For the elevated piers I'm thinking that's my best bet. It seems a pretty good system. But I have some questions: I'm assuming they are made of wood to allow them to float freely. If these ships bring in a lot of cargo (spices, fruits, ores, etc.) how thick would these platforms have to be to maintain the weight of these products and keep them afloat? And to get the cargo up, would they simply wait until high tide, or perhaps use some form of crane (that might be a little advanced, I'm not sure)? If they cannot get the cargo up in a quick fashion, what precautions (if any- is it just a danger of the trade?) would they have in place to get the cargo to safety if a storm hit while cargo is still on the platforms? I suppose the seawalls would mitigate the danger slightly, but not all of the harbour cities can have seawalls and even if they do, they cannot be certain of the cargo's safety.

Necessity is the mother of invention. I am certain if the oceans are such an issue kingdoms would probably either manufacture a harbor (utilizing tons of manual labor to augment the lanscape) or simply limit the number of them that they have in locations that are more suitable.

Another thing to consider is having "stopovers" (possibly using your idea for floating platforms) along the trade route but near the shore; where the large transports transfer goods to smaller ships that can traverse the rivers, where more cities would be located. Likely this would increase the cost of goods a bit, but would allow inland supply runs. Maybe the stopovers even serve as trade depots; where merchants get together and make deals for the different kingdoms in the area.
 

Saigonnus

Auror
As for how thick they'd need to be, it would depend on the materials available to them and how they are built. I would think 2-3" thick planking reinforced with crossmembers below would be sufficient thickness for mostly anything. They'd likely use wheelbarrows or carts to move the heaviest merchandise.

I also mentioned booms, which is a type of crane that has been used for centuries. Basically an upright pillar with a long crossmember rigged with a pulley... attach the ropes around the cargo, other end to horses or a crank device and hoist the stuff up, turn the boom and lower it to the ground or into the back of a wagon.
 

Creed

Sage
Twenty foot tides are the norm in my part of the world.
So about six metres in metric. So I should be able to have 20m tides in bad weather- which would be about 65 feet.
I usually had to walk up about 200 steps after finishing a 12 hour shift.
I certainly hope the pay was good!
Maybe the stopovers even serve as trade depots; where merchants get together and make deals for the different kingdoms in the area.
If I was a merchant in that world I would stay well away from the oceans. It's quite a dangerous place to be, storm or no. However the idea could work for the convenience of ships.
I would think 2-3" thick planking reinforced with crossmembers below would be sufficient thickness for mostly anything.
Perfect! Along with the boom-cranes I think these harbours are nearing technological completion! I don't really need a huge amount of detail for them, I just thought it was an interesting concept I would like to explore. After all, us humans are a crafty bunch and I was confident there would be interesting solutions!
 

A. E. Lowan

Forum Mom
Leadership
Another thought might to have a completely man-made harbor with the water level held level, and locks built to accommodate the varying shifts in tides.

Lock (water transport) - Wikipedia, the free encyclopedia

That way, all the engineering happens at the harbor's mouth, and your ships don't have to worry about complicated maneuvers while loading and unloading cargo and people. Maybe this could be a new technology?
 

CupofJoe

Myth Weaver
Another thought might to have a completely man-made harbor with the water level held level, and locks built to accommodate the varying shifts in tides.

Lock (water transport) - Wikipedia, the free encyclopedia

That way, all the engineering happens at the harbor's mouth, and your ships don't have to worry about complicated maneuvers while loading and unloading cargo and people. Maybe this could be a new technology?

That was [sort of] done in the Liverpool docks in the early 20C. As the ships got bigger, the river didn't get deeper, so they would float the ships in on high tide, the dock bays would be closed behind them and they could unload.

I could also see cargo lifts [elevators] being an option given a little technology. If you know about counterweights and have access to water, lifts could work too.
 

Queshire

Auror
I don't know much about tides, but wouldn't five moons not effect the size of it much? I mean, aren't the tides caused by the moon's gravity pulling at the water? So wouldn't the tides size only be affected if multiple moons line up in a way that their gravity worked together to increase the pull? I imagine that would certainly happen, but how often it happens is up to you. I think five moons would make mostly make the moons a lot more complex / unpredictable with the five moons each trying the pull the water and the tides in different ways, though unpredictable tides would be dangerous in their own rights. Sorry if I'm talking out my ass here, like I said, I don't know much about tides.
 

Creed

Sage
Another thought might to have a completely man-made harbor with the water level held level, and locks built to accommodate the varying shifts in tides.
I'll have to do some research in that vein, because I'm not sure what sort of technology level would be required to do this sort of project.

Sorry if I'm talking out my ass here, like I said, I don't know much about tides.
Don't worry, because you're exactly right!*
However, it's a complicated thing, the balance of moons. Take, for instance, Earth. Because our moon Luna weighs just the right amount, our planet's tilt is stabilised and our seasons are equal. So for any ASoIaF fans out there, the prospect of very long and uneven seasons is realistic- in fact, our seasons are a cosmic anomaly.*
So if there are two moons with similar masses and distances on the opposite side of a planet, then theoretically their influences on the tides would be acting against each other. This would cause tidal bulges on either side of the planet. If they all aligned on one side of the planet, then the bulge would be very large. These swells of water can cause larger waves and, again in theory, bigger storms. And if the theory is more convoluted than that, well then science will have to take a step away from my fantasy, because hey, it is fantasy after all.*
Two of my moons are rather small and don't have much influence. One is barely noticeable in the tidal sense. Morin, however, is larger and Vaki is the largest. They are on opposite sides, but still their tidal influence is noticed, like in storms and high tide.
 
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