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Wind Powered Freighters Return
thatoneguyfromphoeni writes "It appears that sails could return to the ocean's freighters soon. Newsweek is reporting on a technology to assist with cross-ocean travel. From the article: 'SkySails' system consists of an enormous towing kite and navigation software that can map the best route between two points for maximum wind efficiency. In development for more than four years, the system costs from roughly $380,000 to $3.2 million, depending on the size of the ship it's pulling. SkySails claims it will save one third of fuel costs.'"
During the oil crisis in the early 80's they worked on this. I'm fairly sure one company did add sails to a ship or two and did see a reduction in fuel consumption.
Also Popular Mechanics ran an article on this like 4 months ago. In fact it was on the cover of that issue.
Actually, this is not just a weird idea, but this is already in use by Beluga, an ocean carrier from Bremen/Germany.
(Funny that the image whose words I have to type in right now says 'seaport' (-: )
Sorry, this is the best I could find. I'm just not that good with this Google thing. I was looking for a picture, but FTL:
Rising fuel prices during the 1970s prompted the development of a new technology that used sails shaped like aircraft wings turned on end to take some of the burden off the engines and save fuel. Slightly curved to form a wing shape, these sails were attached to a mast that could pivot and locate the best angle for the sail to catch the wind. Once the computers set the mast at the best angle to the wind, the sail created the same "lifting" force that an airplane's wing generates, except that the force pushed the ship along the water. However, this system did not always prove to be efficient for extremely large vessels. I thought what I saw was that the mast itself was a rigid aerodynamic sail.
What?
Here is a video from their site. This is obviously a prototype, so they have a LOT of scaling to do. Plus, the only time you see the boat (yes, I said boat, not ship) moving with any significant speed, you can't see the rear, so it's safe to assume that its engine is assisting.
According to http://www.skysails.info/index.php?id=66&L=1
To get an increase of 35% (the max claimed by SkySails) would mean a 3.5 million euro investment, that's a lot of crewman salaries even at union wages and less than the Skysails implementation would cost.They have some interesting performance calculations on their website too about how much sail produces how much energy. http://www.skysails.info/index.php?id=89&L=1
It takes some time to get a supertanker turning... but once they turn it takes significant time to stop the rotation. Rotational inertia can work against you.
Having the pulling force closer to the center of the ship will decrease the needed rudder force for correction; using the rudder creates friction, so that's best avoided. Another advantage of having the ropes mid-deck makes it possible to lower the kite on deck, much more convenient than fishing it out of the waves after use.
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The parasail behaves very differently to a normal triangular sail or even a jenica. You move the parasail constantly through the air in a figure of eight to generate power. Also these ships are likely to follow the trade winds where the wind normally comes from the stern, therefore attaching the sail to the bow won't be a problem as most of the time the ship would be traveling on a broad reach or run.
Assuming that there needs to be something extra for directional stability, there are also :
- centreboards - which drop or hinge from inside the boat which can be retracted
- lee boards - which hinge from the side of the boat, one on each side. The one on the downwind side is usually lowered, hence the name. The most common example I can think of for these that you might know ( from paintings and such ) is Dutch sailing barges.
- bilge keels - short ( heightwise ) keels which run along the bottom of the boat away from the centreline ( along the bilges ), often oriented on a bit of outward angle vertically.
- water ballast - internal tanks which hold water to balance the boat. This is usually more to help with resisting the heeling/tipping force of the sails, but can be also be used to aid directional stability through good balancing.
All of these methods generally do not add any significant permanent draught to the boat. Many of these already have a strong tradition in freight vessels, for example sailing barges which also needed to be able to move through canals, but of course not on the scope of today's freighters. Although it would cost ( or just be impractical ) to adapt these sorts of things to existing vessels, you can imagine a future when wind assisted freighters might have these designed in from the start. There would not really be too much need for extra dredging etc. The wind provides free energy ( barring the cost of the equipment needed to harness that free energy ) and engines can still be used to offset the problems sailing ships had with adverse conditions. I think we'd really have to be on the last two litres of oil before that sort of thing was seriously looked at though, there have been a number of wind assisted schemes over the years which haven't caught on ( not counting actual sailing ships of course ).Regards,
Jo Meder
Boatbuilder and yacht design student turned software developer...
Most newer freighters and tankers can pretty much dock themselves. The have bow and stern thrusters that make them very maneuverable at low speed. These days tugs are more of a backup system for docking ships. They'll tie on and sit at the ready but the pilot on the ship is doing the docking using the bow and stern thrusters.
I reserve the right to think for myself. Others' opinions are optional. Puppy on lap = typos...not illiteracy.