Boats and water travel

Each stage has a check. Do not move on until it passes.

Every boat on the t1 and t2 pages is category D at best: sheltered water, wind up to force 4, waves under 0.3 m. Turn back at the first white horses. Rougher water needs a boat built and tested to its category.

Pick by the water and the load first, then by what grows or lies to hand. Boats come in five kinds, by how they are made:

• Rafts float on their material: logs, bamboo or reed bundles. Stable, slow, hard to steer.
• Logboats are one log hollowed out: the dugout.
• Frame boats stretch a cover of hide, bark or cloth over a light frame: coracle, bark canoe, kayak, umiak. Light enough to carry.
• Plank boats are built up from boards. They grow to any size and take a sail.
• Sheet boats are industrial: plywood, aluminium, fibreglass, polyethylene.

Season it first. Freshly felled, any of these woods can weigh 800–1,000 kg/m³ and float awash. Lift is 1,000 kg/m³ less the wood's density (USDA Wood Handbook, air-dry at 12 % moisture):

A boat floats by pushing aside its own weight of water: 1,000 kg per m³ in fresh water, 1,025 kg in the sea. Two limits set the load:

• People: length × beam ÷ 15, both in feet, for open boats under 20 ft in good weather (US Coast Guard rule of thumb). In metres, about 0.72 people per m² of length × beam: a 4.5 × 1.4 m skiff carries 4, a 4.6 × 0.64 m dugout 2.
• Freeboard: at full load, the lowest point water can come in over stands at least 0.2 × the beam above the water (FAO): 28 cm on a 1.4 m beam, 13 cm on 0.64 m.

The sum is a starting point; the tests decide.

A boat rights itself while its weight G acts inside its buoyancy B: as it heels, B moves to the low side and pushes it back up. It capsizes when G rises or moves out past B.

• Wider is stiffer: initial stability rises with the cube of the beam at the waterline, so a hull 20 % wider is about 70 % stiffer.
• Keep the weight low: cargo on the floor, crew seated. One person standing in a narrow boat can capsize it.
• Outriggers and twin hulls give width without weight: a float 1–1.5 m out.
• Ballast (stones or sandbags on the bottom) lowers G, and is load the boat must also carry.
• The sail comes last: fit one only to a boat that passes the stability test without it.

In calm, shallow water, with help standing by. Load it with the real crew, or water drums weighed to the same total. A raft takes the load test only; the swamp tests are for open boats. A boat that fails does not go out.

• Everyone afloat wears a float. A lifejacket or buoyancy aid; where none exists, at least 5 litres of sealed air held on the chest: a closed gourd, drum or dry bag. The smallest rated aid, 50 N, gives about 5 kg of lift; 150 N or more turns an unconscious person face-up (ISO 12402).
• Cold water: float first. The gasp and fast breathing of sudden immersion pass in 60–90 seconds. Lean back, keep the airway clear and move as little as possible until breathing settles; then act (RYA, giving the RNLI's Float to Live advice).
• Capsized: stay with the boat. A wooden boat floats swamped, and is bigger and easier to see than a swimmer. Swim only when the shore is close.
• Never alone. Tell someone on shore where you are going and when you will be back.
• Carry a way to signal: a whistle, a torch, a mirror.

Hull speed: no displacement hull goes much faster than about 4.5 × √(waterline length in m) km/h, whatever drives it: 9 km/h for a 4 m canoe, 18 km/h for a 16 m ship. Going faster takes a light, flat hull that planes, and far more power.

The collision regulations are the same on every sea and most rivers (COLREG):

• Keep clear of big vessels in channels. A boat under 20 m, or any sailing boat, must not impede a vessel that can navigate only within a narrow channel (Rule 9). A ship takes several of its own lengths to stop.
• Keep to the right of a channel. Meeting head-on, both turn to starboard and pass port to port (Rules 9 and 14).
• Power gives way to sail (Rule 18), except when the sailing boat is overtaking or in a narrow channel. The overtaking boat keeps clear, sail or power (Rule 13). Two power boats crossing: the one with the other on its right gives way (Rule 15).
• Buoys mark the channel's sides, read going in from sea. In IALA Region A (Europe, Africa, most of Asia including India, Australasia) keep red on your left and green on your right. In Region B (the Americas, Japan, Korea, the Philippines) the colours are reversed: red right returning. In both, port marks are can-shaped and starboard marks cone-shaped (IALA R1001).
• At night, a rowing boat, or a sailing boat under 7 m, keeps a white torch or lantern ready and shows it in time to prevent a collision (Rule 25).
• Launch and land bow or stern to the waves, never side-on: a breaking wave on the side rolls a small boat.

Before every trip: lashings, seams, floats, and the capacity mark.