Sea based human civilisation.

The Uru people live on artificial floating islands in Lake Titicaca: although it still doesn't seem sustainable enough to support an advanced society, it is pretty cool.
 
Well, they are cheaper, in the preindustrial times we are talking about, then metal ships.
But way more expensive than wooden ones.

Furthermore, metakaolin is very easy to produce, being just heated pure clay (kaolin) and when mixed with lime, which can, and in OTL, was by the Maya for example, be produced by burning marine shells, which are obviously ubiquitous on marine shores environments and would also be a useful byproduct product from the farming of conch, bivalves, limpets and other shelled mollusks.
Right, now try producing big sheets of the stuff at a quality good enough to be watertight.

Concrete ships would also last far longer than steel ships which would be far more expensive and difficult to produce without the Bessemer process.
It would still be a lot more expensive to produce and a sight harder to work with than wood.
 
But way more expensive than wooden ones.

Right, now try producing big sheets of the stuff at a quality good enough to be watertight.

It would still be a lot more expensive to produce and a sight harder to work with than wood.
About Cost: Not if one is in Micronesia or many parts of Polynesia with very sparse land. And, given that the bamboo rebar is sealed off from external decay and pests by the concrete, the boats would be able to last a great deal longer than wooden ships and even longer than steel ships.

On Concrete Manufacturing: Metakaolin-lime concrete hardens under water (like the chemically similar Roman concrete). And one would be pouring the concrete into a bamboo rebar frame surrounded by a series of small to large, say 10 or more metres cubed, reusable wooden or bamboo molds (or cast a small boat as a single piece with the bamboo frame encased and protected by the concrete) as the concrete rapidly harden, not making it from sheets or planks as in wood or metal ships.
 
About Cost: Not if one is in Micronesia or many parts of Polynesia with very sparse land. And, given that the bamboo rebar is sealed off from external decay and pests by the concrete, the boats would be able to last a great deal longer than wooden ships and even longer than steel ships.
So precisely how are you starting the shell burning? Also, bamboo is an absolutely terrible material to be used for a rebar, it's too hard to bend the stuff into the shape a boat would need to be.

On Concrete Manufacturing: Metakaolin-lime concrete hardens under water (like the chemically similar Roman concrete). And one would be pouring the concrete into a bamboo rebar frame surrounded by a series of small to large, say 10 or more metres cubed, reusable wooden or bamboo molds (or cast a small boat as a single piece with the bamboo frame encased and protected by the concrete) as the concrete rapidly harden, not making it from sheets or planks as in wood or metal ships.
If you haven't got the wood to build a ship you haven't got the wood to build the mold for a ship. Also, the fact that you'd need a land-based industry means that you couldn't actually make the people sea-based to begin with.
 
Moreover, Land-based ships could be short ranged, more specialized, faster and not least better armed. Picture a Byzantine Dromon or Barbary Xebec as examples. Fast, maneuverable ships like these, operating from coastal bases would suffice to run down the sea people's craft.
FWIW the first society that came to my mind when I read this thread was the Marsh Arabs, as depicted by Thesiger.
of course I realize they weren't a seafaring society
 
If you haven't got the wood to build a ship you haven't got the wood to build the mold for a ship. Also, the fact that you'd need a land-based industry means that you couldn't actually make the people sea-based to begin with.

But your last argument states that aside from genetical manipulation it's pretty much impossible to get a fully sea-based civilization: no wood, no meltable minerals or charcoal means no metal tools...

I think what is possible is a civilization which inhabits small islands as outposts and primarily is engaged in seafaring and trade, whereas bigger islands and landmasses are populated by other peoples. Essentially, some sort of early Venice without Terra Ferma. Therefore, Indonesia and the Philippines seem the easiest choice for me.
 
But your last argument states that aside from genetical manipulation it's pretty much impossible to get a fully sea-based civilization: no wood, no meltable minerals or charcoal means no metal tools...
Which is pretty much what I've been saying all along, no civilisation can be entirely sea-based, the resources needed to maintain a civilisation just don't exist qat sea, and the more advanced a civilisation gets the more resources it needs. Oh sure, it might be possible for a new-stone-age people to be nomadic seafarers, but as soon as you add metal to the mix your cost of maintaining that civilisation rises dramatically, even though your population hasn't grown.
 
Here is a scenario I came up with a decade ago here:

Originally Posted by Fardell on SHW-I in 2001
POD sometime in antiquity (probably 2000 - 500 BC)
A group of people develop a religion that says that the sea is where the
true people roam.

Over a few decades they build some really large ships (the largest at that
time), on the ships they take farm animals, put soil on a large part of
the upper decks deep enough to grow trees for extra wood for more ships
and for growing crops

Not looking back to the land they sail off. For a long time they are alone
on the sea and they use the bones of Whales and sharks to augment the wood
and more ships are built and their diet consists of mainly fish and
seaweed. They bury their dead in the sea. Sometimes groups split off.
hundreds of years later the time their ancestors lived on land is mainly
legend. Tribes of this people wonder the worlds oceans. They develop
excellent navigation and map the world (the outline of the land they never
go up rivers). They occasionally trade with the Polynesians. They Judge
the weather conditions really well. They call themselves the People of The
Sea

AD 60's a Roman ship sailing the Channel between Brittania and Gaul sight
a really large ship larger than their largest Tirieams made of wood and
whale bone... ...and trees on the deck. Intreaged the Roman captain orders
them to approach carefully. The first contact goes well despite the fact
that the People of The Sea don't understand Latin or the Romans don't
understand the language of the People of the Sea.
Word of the ship is sent back to Rome. The Emporor (Nero) orders that the
Empires best linguists find a way to translate to and from Latin and the
Language of the People of The Sea. The People of the Sea are careful as
they had never encountered a large land based Empire before. As it was it
takes a year to find a dialogue in between the 2 languages.
The Romans want copies of the maps that the People of the Sea have. The
leader (captain) of the People of The Sea ship decides just to give the
Romans a map of part of the Atlantic. The map shows Africa around to the
mouth of Congo, the Atlantic Coast of Europe up to Danmark, The Norweigen
coast up to the Artic circle (As the People of The Sea have never been in
the Mediterrainian or the Baltic), Iceland, the British Isles, The
Canaries, The Azore's and Bermuda. The Romans are satisfied as they have
never been that far down the African coast or to Iceland (or Bermuda for
that matter). The Romans give them a map of the Mediterrainian and the
Black Sea
The Ship then leaves the Channel with the People saying that
the Roman Empire will be visited from time to time by the People of The
Sea

It takes a few decades for the knowledge of the Roman Empire to spread to
all of the People of the Sea as they are spread over all of the world at
this point.

The Romans continue to have visits by the People of the Sea until the
Western Empire collapses. The contacts do not change the Romans history
from OTL as The People of The Sea don't give them any more maps although,
the Romans do hear about the Chinese and the Polynesians.

Edit: And a 5 year old thread here.
 
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So precisely how are you starting the shell burning? Also, bamboo is an absolutely terrible material to be used for a rebar, it's too hard to bend the stuff into the shape a boat would need to be.

If you haven't got the wood to build a ship you haven't got the wood to build the mold for a ship. Also, the fact that you'd need a land-based industry means that you couldn't actually make the people sea-based to begin with.
On Bamboo Rebar: This is a misconception; see here, here and here; bamboo is stronger in tension than steel and one only needs to smoke the bamboo to make it not absorb water from the concrete.

About Shell Burning: One could use fish oil, seaweed or even biogas from decomposing organic waste to heat the shells.

About Molds: That is why one reuses the molds as they are building the ship section by section; it would only take about 12 to 18 molds to make a 40 metre long ship going lengthwise.

About the Land Based Industry: Yes, but only a few small islands for aggregates, and shells occur in abundance on all atolls in Micronesia while clay is also basically universal on all but the smallest islands, for concrete and ore from a few volcanic islands for tools. Metal would of course be recycled, much like in the OTL Bronze Age, due to the fact that fuel would be far more plentiful than ore from the sources I suggested above.
 
On Bamboo Rebar: This is a misconception; see here, here and here; bamboo is stronger in tension than steel and one only needs to smoke the bamboo to make it not absorb water from the concrete.
Strength doesn't matter, you can't make bamboo flexible enough to make any reasonable hull-shape with it.

About Shell Burning: One could use fish oil, seaweed or even biogas from decomposing organic waste to heat the shells.
Low heat and hard to get enough of it. Coal would be a much better solution.

About Molds: That is why one reuses the molds as they are building the ship section by section; it would only take about 12 to 18 molds to make a 40 metre long ship going lengthwise.
and how do you propose for a new-stone-age people to shift a 40-metre concrete ship that would weight in the hundreds of tonnes?

About the Land Based Industry: Yes, but only a few small islands for aggregates, and shells occur in abundance on all atolls in Micronesia while clay is also basically universal on all but the smallest islands, for concrete and ore from a few volcanic islands for tools. Metal would of course be recycled, much like in the OTL Bronze Age, due to the fact that fuel would be far more plentiful than ore from the sources I suggested above.
And then you need to find some way to protect it all from hurricanes and storms. There may be no metal either, which would probably be a big limitation.

Oh, and concrete hulls need to be pretty thick, which means they're going to be heavy, and heavy ships aren't brilliant because they're slow and can't carry nearly as much cargo as wood or metal vessels. Durability has its trade-offs.
 
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So precisely how are you starting the shell burning? Also, bamboo is an absolutely terrible material to be used for a rebar, it's too hard to bend the stuff into the shape a boat would need to be.

If you haven't got the wood to build a ship you haven't got the wood to build the mold for a ship. Also, the fact that you'd need a land-based industry means that you couldn't actually make the people sea-based to begin with.
The shell burning will be fueled by fish oil in large furnaces, similarly to scaled-up qulliq in principle. Or you could put wet seaweed, human waste and other organic materials to decay in a glazed ceramic vessel thus producing biogas. Probably it is more likely that this civilization would simply dry these materials and compress them into pellets.

Bamboo rebar is, as shown in the links I posted, in tension superior to steel; see here about bamboo boats in Vietnam. And bamboo is no more stiff than steel; indeed, it is more elastic whereas steel is more plastic.

And with regards to the molds: That is why the molds are reusable, and do not forget that wood is recyclable, and are only used to make longitudinal sections of the ship; one could use one mold for the same part on dozens of different ships easily.
 
The shell burning will be fueled by fish oil in large furnaces, similarly to scaled-up qulliq in principle. Or you could put wet seaweed, human waste and other organic materials to decay in a glazed ceramic vessel thus producing biogas. Probably it is more likely that this civilization would simply dry these materials and compress them into pellets.
Yeah, now work out how much you need for a 40 metre ship. I think you'll find you need something in the region of 100 cubic metres of the stuff. That won't be cheap.

And bamboo is no more stiff than steel; indeed, it is more elastic whereas steel is more plastic.
You realise that shoots down your whole argument right?
 
Yeah, now work out how much you need for a 40 metre ship. I think you'll find you need something in the region of 100 cubic metres of the stuff. That won't be cheap.

You realise that shoots down your whole argument right?
Actually, that volume of fuel would be easy to come by given the extensive mariculture that would be practiced in the oceans around Micronesia. And seaweeds often grow far faster than bamboo.

The bamboo boat was merely to show that bamboo is very elastic and well suited to use as concrete rebar; the key advantage of concrete is that it can last for well over a century if maintained for even a 10 metre long watercraft being that it does not decay. It can also be built into great sizes far more easily than wood can, or even steel: Just look at the huge reinforced concrete structures that are so common in the modern world on land. And, as it says repeatedly on the Wikipedia page on the subject, concrete ships are very cheap to build compared to metal or wooden ships.
 
Actually, that volume of fuel would be easy to come by given the extensive mariculture that would be practiced in the oceans around Micronesia. And seaweeds often grow far faster than bamboo.
Would seaweed fires even get hot enough to start shell burning?

The bamboo boat was merely to show that bamboo is very elastic and well suited to use as concrete rebar;
Flexibility is NOT good for rebar material, you want something as stiff and strong as possible.

the key advantage of concrete is that it can last for well over a century if maintained for even a 10 metre long watercraft being that it does not decay.

It can also be built into great sizes far more easily than wood can, or even steel: Just look at the huge reinforced concrete structures that are so common in the modern world on land.
Yeah, with reinforced concrete, you can't get more than about 10 stories high with plain concrete, and you'd never get earthquake approval for an unreinforced concrete structure.

And, as it says repeatedly on the Wikipedia page on the subject, concrete ships are very cheap to build compared to metal or wooden ships.
No, the materials are cheap to obtain (but are only so because the production of concrete has been industrialised), but the labour costs are higher than steel ships, and the actual efficiency of the vessels are low, because the hulsl have to be rather thick to survive sea conditions.
 
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Would seaweed fires even get hot enough to start shell burning?

Flexibility is NOT good for rebar material, you want something as stiff and strong as possible.

the key advantage of concrete is that it can last for well over a century if maintained for even a 10 metre long watercraft being that it does not decay.

Yeah, with reinforced concrete, you can't get more than about 10 stories high with plain concrete, and you'd never get earthquake approval for an unreinforced concrete structure.

No, the materials are cheap to obtain (but are only so because the production of concrete has been industrialised), but the labour costs are higher than steel ships, and the actual efficiency of the vessels are low, because the hulsl have to be rather thick to survive sea conditions.
Well, seaweed fires could easily get hot enough if they were compressed into blocks or pellets, easily accomplished with just a simple hand-operated lever press. I did not say bamboo was flexible, I said it was elastic; in other words, it rebounds. And it is stronger in tension than steel (compressive strength is largely moot given the great compressive strength of the concrete itself) and it is being tested for use in contemporary China to reinforce concrete bridges that trucks can go over. And we are not building concrete skyscrapers but concrete ships and floating platforms, both of which have proven completely feasible; the engineering of skyscrapers and of ships, or for that matter, buildings of but a few floors, is very different and subject to different types and levels of stress.
 
I did not say bamboo was flexible, I said it was elastic; in other words, it rebounds. And it is stronger in tension than steel (compressive strength is largely moot given the great compressive strength of the concrete itself) and it is being tested for use in contemporary China to reinforce concrete bridges that trucks can go over.
Buildings tend to stay still, but ships will flex, and it's the flexing that does the damage to the concrete.

And we are not building concrete skyscrapers but concrete ships and floating platforms, both of which have proven completely feasible;
Only when steel is in short supply, and not much even then (in peace-time, concrete ships tend to go out of commission quickly, because they're not that good if there are alternatives.

the engineering of skyscrapers and of ships, or for that matter, buildings of but a few floors, is very different and subject to different types and levels of stress.
Precisely, which is why you can't apply to ships the same methods of construction as you apply to buildings.
 
Buildings tend to stay still, but ships will flex, and it's the flexing that does the damage to the concrete.

Only when steel is in short supply, and not much even then (in peace-time, concrete ships tend to go out of commission quickly, because they're not that good if there are alternatives.

Precisely, which is why you can't apply to ships the same methods of construction as you apply to buildings.
Perhaps we should agree to disagree as we seem to be getting nowhere in this debate; better yet, let us have other boardmembers decide who makes the most sense.
 
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