Is the quadrupling of drag and octupling of rolling resistance related to the assumption that drag is proportional to the surface area of the side on which the drag is produced, and that rolling resistance is proportional to weight?
Yes. It’s a little more complex than this since rolling resistance is irrespective of speed, whereas drag increases with speed. But if you’re aiming for efficiency you’ll go at low speeds, so we can hold speed fixed and see what happens as we scale.
Either way, cost would still decrease due to larger and more complex engines, as rolling resistance per kg would not change.
Even if the engine is 100% efficient, you still lose energy to drag and rolling resistance, so sooner or later increased engine efficiency doesn’t buy you very much.
I was just speculating where the relative efficiency of cargo ships comes from.
I think it’s the fact they’re so much larger, and so drag/capacity is very low.
Yes. It’s a little more complex than this since rolling resistance is irrespective of speed, whereas drag increases with speed. But if you’re aiming for efficiency you’ll go at low speeds, so we can hold speed fixed and see what happens as we scale.
Even if the engine is 100% efficient, you still lose energy to drag and rolling resistance, so sooner or later increased engine efficiency doesn’t buy you very much.
I think it’s the fact they’re so much larger, and so drag/capacity is very low.