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> Is there any prospect of getting near 100%? A sailboat. The word you are looking for is a sailboat. Sailing cargo vessels have a number of issues with econo
by dghlsakjg 3y ago
> Is there any prospect of getting near 100%?
A sailboat. The word you are looking for is a sailboat.
Sailing cargo vessels have a number of issues with economics, which is why we stopped using them 75 years ago. There are some people using them in limited capacities, but for the most part we can't replace our global shipping with them.
Speed is one. Even the fastest sailing cargo ships, which carried very limited cargo averaged 15ish knots on favourable routes. Modern motor cargo can travel at 20+ knots on almost any route.
Even the largest metal hulled sailing ships that lasted until the 1950s carried an order of magnitude less cargo than a small container ship today. And take more crew to handle.
The other issue is that sailing to windward is still not solved by this, and just from looking at the design, I would guess that it actually decreases fuel efficiency on any route that requires you to go into wind.
The other problem with stacking more of these onto a ship is that you have to counterbalance both the weight and the lateral forces. Sailboats do this with a keel. Adding a keel to a large bulker like these is expensive, and will limit the ports you can visit due to draught, which will already be limited by the enormous sail keeping you from transiting under bridges.
- brianwawok 3y agoCargoships would gladly go slower if they burn less oil. In fact they generally opertate nowhere near their top speed for this very reason.
- dghlsakjg 3y agoYes, but slow-steaming for efficiency on a cargo ship is ~18 knots, which is still above the upper speed of the fastest sustained speed of sail cargo vessels. You can slow further for efficiency, but you hit a tipping point pretty soon where you end up costing yourself more in time than you save in fuel. Realistically, a sail cargo ship is going to move along at a rate less than 10 knots. And of course this is all on a route with favorable winds. If the winds are against you, all bets are off. The same is true of these wingsails, there are limited routes where they will be efficient. Anything going up-wind is actually going to be a loss.
- gravescale 3y agoDrag when sailing into the wind and going under bridges, as well as not having them torn away in a storm, is addressed with this design by folding them flat against the deck.
- dghlsakjg 3y agoI saw the picture of them folded down. They are still a good 20 feet higher than the deck. So they can clear bridges.
- paholg 3y agoThe keel issue, at least, can be solved by using a kite instead of a sail. There appears to be at least one company working on this: https://www.cnn.com/2023/06/30/travel/airseas-giant-kites-ships-slash-carbon-emissions-scn-climate-spc/index.html https://www.cnn.com/2023/06/30/travel/airseas-giant-kites-sh...