Item — HN Reader

Modern sailing technology is amazing, and you may want to check it out. Speeds are, literally, 10 times faster (or more) today than the recent past. It’s absolutely astonishing.

The even better news is that the technology is becoming available to the general population and also commercially viable for projects like this.

1 comments

I am familiar with modern sailing technology. Very little of it is applicable to huge merchant vessels. This project is a cute little stunt but it's never going to be economical for moving bulk cargo. Sails will be a minor supplement at best. Seriously, do the math.

Sincere question: have you done the math? If so, this conversation would be a lot more interesting if you shared it.

How much sail area would it take to move a 20000 TEU ship at, let's say, even 12 kts? How tall would the masts have to be? Would they fit under bridges? You guys are talking about total fantasies here.

But you don't need 12kts, right? The ocean logistics is ~only about costs, as evidenced by the reduction in travel speed. That being said, cost is currently not dominated by fuel cost either. That means unless you reduce crewing requirements or build cost, there is probably not much savings that will pencil out. Plus you'd need more ships and the physical capacity to build more is limited

> How much sail area would it take to move a 20000 TEU ship at, let's say, even 12 kts? How tall would the masts have to be? Would they fit under bridges?

For ocean-going ships, isn't 99.x% of the trip in the open ocean? If so, what limit is there on sail dimensions? It's a genuine question; if coastal infrastructure isn't the limit, what is the next limitation.

They could lower sails, and use a motor and/or smaller sails, around coastal infrastructure.

The power required would be the same as that provided by the bunker fuel engines in common use. Modern, computer controlled sails are efficient and very powerful. It’s obviously working for this ship, which is a conservative build.

I think nradov has a point about the physics.

> The power required would be the same as that provided by the bunker fuel engines in common use

And that is a lot of power! Emma Mærsk has an engine output around 80-90MW.

The largest off shore wind turbine today is 26MW with a rotor diameter north of 300m/1000ft(!!). Common (modern) offshore wind turbines today are about 10-15MW with rotor diameters of ~220m/720ft.

I will not conclude it is impossible at this end of the scale, but you need a huge foil area to match such engine output.

IIUC, the physics work against us as we scale up in size, because of the square/cube-law https://en.wikipedia.org/wiki/Square%E2%80%93cube_law (weight of the foil/sail + mast is cubed when the area is squared).

> Would they fit under bridges?

You do realize that none of those ships could get into any port, right? We've made modifications to accommodate that.

I tend to agree with you that putting a fixed sail on top of a container vessel won't fly.

Maybe ships would need to be smaller. I think the size of ships was mostly increased because it makes it more efficient. But if fuel is free, you could have smaller ships take direct routes instead of the layovers we do now. That might compensate for time lost as well due to lower speed.

This is a PoC not a finished product

> I tend to agree with you that putting a fixed sail on top of a container vessel won't fly.

Of course it won't, it's not an airplane.

Perhaps sardonically, sailboats do “fly” these days. Not literally, just terminology.

> > Would they fit under bridges?

> You do realize that none of those ships could get into any port, right?

Container ships sail under bridges all the time. Check YouTube for videos of this or just Google it if you want proof.

Yes I understand, my point was that we've adjusted ports to make room for container ships. So making some adjustments isn't out of the question.