How large can an oceangoing vessel be made within the constraints of Neolithic technology?

Question

Long story short, I have a bunch of folks with Neolithic technology, and they want to build a big ship - preferably, a ship that's as large as they can make it.

How big can these Neolithic folks make this ship? Assume that the amount of available labor and the will to build this thing are all non-concerns, and that this vessel is being built over many generations (let's say five), much like some European cathedrals. Resources are also a non-problem too, although they're limited to what can be produced and handled with Neolithic technology - no steel, aerospace composites, or electronics here, nosiree.

There's certainly precedent for ships being built with Neolithic technology, so, at least in that regard, this question is based on an entirely plausible concept. I'm just asking how large such a vessel could conceivably get.

Also, I'm asking about one big vessel, not many smaller vessels, for multiple reasons that are irrelevant to the scope of this question. It has to be one big one.

Answer 1

• Like many such questions, you have to decide how far you can uplift your neolithic people before they are no longer neolithic. I believe both clinker and carvel boats are bronze age technology even if they are woodworking. So you would have neither without leaving the neolithic. Dugouts are limited by the availability of large trees, wicker boats are limited by stability.
• When you build a wooden ship, having many generations might not resolve anything. Once the logs are cut, they will start to dry and shrivel; once they are in the water, they will start to rot. So having a supply of seasoned wood when you start might be the way to go.
• Boats like the Kon-Tiki had a tendency to come apart during their voyage, which is kind-of-OK if you have an emergency radio and a plane ticket home. If you want a practical trans-oceanic vessel, it should be more likely to make it home than not.

So my gut feeling is a 100 to 200 cubic metres, possibly doubled in a catamaran arrangement. Certainly smaller than a trireme.

Answer 2

The linked Kon-Tiki was already more than a floating cork:

The main body of the float was composed of nine balsa tree trunks up to 14 m (45 ft) long, 60 cm (2 ft) in diameter, lashed together with 30 mm (1+1⁄4 in) hemp ropes. Cross-pieces of balsa logs 5.5 m (18 ft) long and 30 cm (1 ft) in diameter were lashed across the logs at 91 cm (3 ft) intervals to give lateral support. Pine splashboards clad the bow, and lengths of pine 25 mm (1 in) thick and 60 cm (2 ft) wide were wedged between the balsa logs and used as centreboards.

The main mast was made of lengths of mangrove wood lashed together to form an A-frame 8.8 m (29 ft) high. Behind the main-mast was a cabin of plaited bamboo 4.3 m (14 ft) long and 2.4 m (8 ft) wide was built about 1.2–1.5 m (4–5 ft) high, and roofed with banana leaf thatch. At the stern was a 5.8 m (19 ft) long steering oar of mangrove wood, with a blade of fir. The main sail was 4.6 by 5.5 m (15 by 18 ft) on a yard of bamboo stems lashed together. Photographs also show a top-sail above the main sail, and also a mizzen-sail, mounted at the stern.

The raft was partially decked in split bamboo.The main spars were a laminate of wood and reeds and Heyerdahl tested more than twenty different composites before settling on one that proved an effective compromise between bulk and torsional rigidity. No metal was used in the construction.

Without technologies available to join together trunks and make longer assemblies, you are basically limited to the length of the tallest trees you can chop down, using a stone axe. Considering that you will use similar trees as beam, you are limited within a square.

20-30 meters is therefore what you can reasonably get.

Answer 3

This is a fairly complicated question, to which I believe a complete answer to be impossible. Anyway, here's my shot at it. First some questions:

1. Does it need to be a ship-shaped ship?
2. Where do your protagonists live?
3. What material and/or which animals do they have access to?
4. During the use, may there be one person dedicated to maintainance?
5. Does it have to be fit for the ocean? Or just near the shore?

If you don't need the ship to be boat-shaped, a multiple pontoon raft might be the better construction. If your neoliths live in an area where large bamboo exists, this gives the better building material for the main parts, as it is very easy to split to flexible, tough, long strips. Otherwhise willow will work, but no where near as good. If your neoliths have access to slightly larger animals (moose and simmilar), that would help with large skins, but again smaller animals (sheep) will work.

Assuming bamboo to be available the concept goes as follows:

Preparation: You'll want to build roofs to keep at least some rain off your materials. You'll need something like 20-30m x 2-3m for your long material. Your baskets can be stacked and stored under 5x5m.

Building-Blocks:

• First large baskets are woven. Building baskets of about 2 m depth and 2-3 m width is easily a task Neolithic folks are capable of. These baskets don't need to be tight, but they need to be sturdy-ish.
• Then other baskets are woven. This time, an opening to the side is needed, large enough for a person to enter through. The first baskets will become pontoons, the second ones will help making the whole construction more sturdy. They will double as storage and crew quarters, if necessary. These second baskets are not strictly necessary, but they simplify things.
• Large strips are woven, (2-3) x (10-30) m. These may be used for the floor, as well as for walls.
• Many felts are prepared, turned to leather, and maybe even sewn in shape to wrap around the baskets. Similarly large sheets are created for roofing and for sails.
• Tar, resin, or bees wax is used to make the materials more resilient against pests and rot.

The baskets can be stacked top down and small fires may be lit under them to keep them dry and smoke them, keeping pests and rot away. (Keep in mind, that these fires should smolder at least 2-3 hours at least every second day, but it would be far better to keep the smoke going almost constantly...)

Assembly: The pontoon baskets are wrapped in their leather lining and placed on the water. The strips for floors are placed on them and they are bound/woven into place. Larger "nests" of these are placed end-to-end as well as next to each other. Then their floors are interwoven. This is where the bamboo-strips shine, as you could get flexible strips of up to 30 m length, allowing for very solid links. These floors will not come apart (at least not easily). (If willow is used instead, we have to rely on ropes instead.) Next the walls are added. By putting the second type of basket upside down on the floor, shifted by half a basket, and connecting it to the floor, the structure becomes a lot more sturdy. Also the outside is the perfect for attatching the connections between the walls to. This helps again with stability and allows us to close the shape.

This structure could easily be built to multiple hundred meters diameter. It could be round, long or pointy-ish, resulting in an over-all ship shape. Somewhere between 2 and 5 layers of living space are possible, even though more than 2 layers might not be sensible. If a few people go around and check if, and how much water seeped into the pontoons, and empty them by bucket, that should easily be functional for long times and small to medium-harsh oceanic use. For harsh ocean passage it is probably more sensible to build smaller ships and link them with ropes to a semi-fixed non-rigid patch.

If you can completely forgo any ship-shape, you can build a massive raft / multiple-pontoon-raft dwarfing our current oil freighters. After all, you got 5 generations and neither material nor workforce are of concern. This will however only be semi-rigid, as it starts hitting the strength limits for your woods. Also it is probably stupid.

Which leads us to the final questions:

• What is the purpose of your ship and
• Why does it need to be one ship?

If the ship shape is a hard constrain, and you refer to it being a functional ship shape, about 40-50 m probably is the limit, with the 20-30 m that L.Dutch posted being the reasonable maximum.