Moving this interesting debate to a new thread to avoid being told off!
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Off topic, but I can't let that one go. Absolutely not! Cargo ship schedules are vitally important to keeping freight out of the air and in the sea, which is a vastly more efficient place to put it. Some cargoes can move slow, particularly bulk cargoes, but the capital cost starts getting high (of the cargo existing and being owned by someone, but not in use). For container ships there is a reason there has been a shift of schedules towards faster ships - demand. Putting sails on ships can make them less efficient - a modern 15,000+ TEU container ship is vastly more efficient than a smaller vessel, but is far too big to make sails anywhere near viable - moving to smaller ships would be environmentally bad. The marine industry's future probably lies in biofuels for long distance tradeCargo ships do not need to move quickly; if you want to move freight fast you fly it.
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Because it really isn't possible to go to 100% sail power - realistically it would be sail assist, not fully sail. If a large ship is 50% more efficient than a small ship, and the small ship could save say 40% of fuel through using sails, the large ship is more efficient. It takes months to sail from Asia to Europe, and the modern world requires goods to be delivered on a given date, rather than just 'when it gets here' which is how it used to work. Also modern crew would not be prepared to sign on on this basis. Our shipping lanes are also far too busy to cope with the vast increase in number of ships that would be needed to cope with modern trade, especially under sail, which means they can't go in straight lines. As you frequently say, 2 car DMUs on the WCML is a bad idea - the Dover Strait isn't that different! The largest cargo sailing ship ever built was France II - She had a deadweight (cargo weight capacity) of ~7000t. A very large modern container ship has a deadweight of around 200,000 tonnes. Whilst a modern sailing ship could get bigger, it can't get that much bigger - there are length, depth and height restrictions, A modern cargo ship is also basically a big square box, optimised for carrying cargo. This isn't possible with a sailing ship, masts get in the way, so capacity is reduced further.How would moving to smaller ships so as to avoid the burning of diesel entirely be environmentally bad? I'm sorry, I can't see that as anything other than nonsense.
The real fix of course is to stop shipping manufactured goods and food half way round the world when it can be produced locally (including a view to eating more seasonally). Which, to get back on topic again (amazingly), is a benefit of building Class 197s in Wales!