EV cars.

[lmoengnr]

Boats use a lot of power to keep them moving. A boats engine is constantly under load unlike a car that coasts somewhat once it gets up to speed. A boat motor is never efficient like other forms of transport. But then again carrying capacity it would take many, many planes to carry the same load. I don't see us losing sea transport.

Love looking at huge ship diesel engines, especially those fitted with access doors into each cylinder.

 

[J_D 2.0]

A boat motor is never efficient like other forms of transport.

Au contraire, a boat engine is basically as efficient as it can be most of the time. All engines have a specific BMEP that they are most efficient at and a ship engine can run at that BMEP most of the time.

 

[Immortality]

Love looking at huge ship diesel engines, especially those fitted with access doors into each cylinder.

Those are cool engines.

 

[figjam]

Boats use a lot of power to keep them moving

Cars are going to end the world, and we are all guilty ! !

And yet very little seems to be said about boats full of rich, drunken tourists going for a cruise from somewhere to nowhere and back for no good reason other than to eat, drink alcohol, and be obnoxious whenever they get off at an island.
I have been on 2 boat cruises to NZ. The first was something new, the second was one too many and the last.

 

[losh1971]

Au contraire, a boat engine is basically as efficient as it can be most of the time. All engines have a specific BMEP that they are most efficient at and a ship engine can run at that BMEP most of the time.

Yeah but driving on water is what reduces its efficiency. Agree there is a point when the boat gets to it's optimum speed and efficiency. They are as efficient as they can be and that's probably somewhere around 3/4 throttle.. But you say stick that same engine in a train carrying the same weight and the boat would still use more fuel. The boat has constant resistance, which is why they use so much fuel compared to other forms if transport.

 

[chrisp]

Boats use a lot of power to keep them moving. A boats engine is constantly under load unlike a car that coasts somewhat once it gets up to speed. A boat motor is never efficient like other forms of transport. But then again carrying capacity it would take many, many planes to carry the same load. I don't see us losing sea transport.

There is a very old, and a moderately famous calculation regarding shipping. There used to be speculation that powered shipping would have limited range and that the more range, the more fuel that needed to be carried. The assumption was it was a diminishing returns, and a practical limit to the range as at some point the entire carrying capacity would be given over to carrying fuel.

The assumptions were wrong, and simple mathematics proved it wrong. The carrying capacity is proportional to the volume of the vessel, whereas the fuel needed is proportional to the friction, which is proportional to the area of the hull in the water. Volume is a cubic (power of 3) function; area is a square (power of 2) function. So, the bigger the better - more carrying capacity per unit of fuel. Those super carriers are actually very efficient.

 

[J_D 2.0]

Yeah but driving on water is what reduces its efficiency. Agree there is a point when the boat gets to its oTdoptimum speed and efficiency. They are as efficient as they can be and that's probably somewhere around 3/4 throttle.. But you say stick that same engine in a train carrying the same weight and the boat would still use more fuel. The boat has constant resistance, which is why they use so much fuel compared to other forms if transport.

Boats are the most energy efficient form of transport hands down. The resistance of the water isn’t as much as rolling resistance for land transport.

 

[Immortality]

Problem is, no train will ever get close.

You can't beat large ships for cost efficiency of moving cargo period. They also burn much cheaper fuel, it's really the crap left over after all the other good stuff is removed from oil.

 

[losh1971]

Boats are the most energy efficient form of transport hands down. The resistance of the water isn’t as much as rolling resistance for land transport.

All boats or just ships?

 

[Immortality]

Big boats are very different to your little trailer runabout. Those suck a heap of petrol to go not very far.