I know that there have been multiple postings related to boats, but I have thought of ideas that would work for boats.
Boats can only be bullt out of wood or metal, with wooden boats easier to build then metal ones, because wooden boats are built using planks (5 planks per log) where as metal boats are built using hull sections which in made with one bar. Wooden boats are smaller then metal boats because metal is stronger then wood in large structures. The strength of metal comes at a price though, it weighs more and therefor has more water displaced because of that. The displacement of the boat goes like this:
# is the depth of the water, _ | is the hull . Is the surface.
..|___|.. ..|___|..
7333337. 7|___|7
In the first example, the ship has a displacement of 4/7 and the second example the ship has 7/7 displacement and ran aground. The ship looks like the first example for displacement of 1/7 to 6/7.
The ship also increases or decreases displacement depending on weight of cargo.
Ships also leak and will need either buckets or bilge to get rid of the water.
Boats are built in a carpenters workshop if it a canoe, but on slipways or dry docks for larger ships.
slipways require wood supports to slide down when finished.
Dry docks use more materials to get setup but can test ships before sending them out, but need a pump to remove the water, and a special floodgate that restricts the flow of water into the dry dock.
When ships are being built, they get built by shipbuilders, and the amount of leaking is related to the skill of the builder. The keel is built with double the number of planks or plates for extra strength and the hull with the normal amount. Portholes can be built too.
Ships are propelled by either the wind, oars, or paddle wheels.
With the wind, all that is needed is a sail, but is then dependent on the wind strength, oars are used by dwarfs for smaller ships, and paddle wheels are powered by dwarfs, animals or by windmills.
It would be possible for ships that use paddle wheels to be powered by windmills and dwarfs or animals.
But food would be needed for animal power. However, once built and launched, there are four options for the ship;
A) use for trade, which would then have a crew on board (must be assigned) and trade goods.
B) use for local use, which could be used for defense, fishing or transport accross a river.
C) use as colony ship [stay at fortress] you then select a crew and provide food and supplies, and then the ship leaves to start a new fortress around the world or just stay at sea.
D) use as colony ship [stay with ship] you then select a crew and stay with the ship and leave the fortress with the crew
The max crew size is 50% of your fortress population currently.
Ships that are large anough can have fisheries and small farm plots, and have siege engins on board.
Ships cannot go over waterfalls, and need to use a lock to get around it, but the canoe can just be carried around the falls. Lock diagram: [] flood gate [.] dry dock flood gate ~ water |_ boat # wall
[]~|___|~[]~~~~~
[]~~~~~~#
~[]~~~~~~[.] two, on for inflow and one for outflow
A leaver to operate the gates are onshore and placed in a manner that is easy to tell lower lever fg on left, drain ddfg left middle, fill ddfg middle right, and upper fg right.
Any dwarf at sea can get sea sick if there are waves, on lakes and oceans.
Any canoe found by an adventurer can be used.
I also apologize for the length of this post.