Modern Ships by Sail Assist

[xoxoxoBruce]

I don't think that para-sail would provide enough tug to make a significant difference.

This should work though. http://www.ecogeek.org/content/view/2276/

[BigV]

Originally Posted by xoxoxoBruce

I don't think that para-sail would provide enough tug to make a significant difference.

This should work though. http://www.ecogeek.org/content/view/2276/

Depending on the prevailing wind conditions, a ship’s average annual fuel costs can be reduced by 10 to 35% by using the SkySails-System. Under optimal wind conditions, fuel consumption can temporarily be cut by up to 50%. The SkySails-System consists of three simple main components: A towing kite with rope, a launch and recovery system, and a control system for automatic operation.

Sail power is back.

The MV Beluga SkySails, a cargo ship rigged up with a billowing 160-meter sail from SkySails, used approximately 20 percent less fuel than it would have without the sail during a two-month voyage. Put another way, that's 2.5 tons of fuel, or $1,000 a day, in operating costs. Beluga Shipping ultimately hopes to save $2,000 a day with the technology.

$1000/day is pretty sweet. Free money, no?

[xoxoxoBruce]

A ship is a highly dynamic system that is simultaneously exposed to a number of different environmental conditions. The result is a complex arrangement of cause and effect, whose factors have a linear correlation in only the most seldom of cases.

All those calculated claims are based on the premise that these kites will have sufficient tug. Color me skeptical.

The MV Beluga SkySails, a cargo ship rigged up with a billowing 160-meter sail from SkySails,...

The pictures of that ship look like a fair sized cargo ship with a 160 square meter sail.

For comparison: The 109m long four-mast barque “Sea Cloud” has a sail area of 3,000m² in total. A cargo ship of the same length would be fitted optimally with a towing kite of 300 to 600m² in size.

So a 109 meter (358 ft) ship, which the Beluga looks it could very well be, should have 2 to 3 times the sail area they show in the pictures to support their claims. Hmmm, I think it's a good idea, but I'm still skeptical of their claims.

A ship is a highly dynamic system that is simultaneously exposed to a number of different environmental conditions. The result is a complex arrangement of cause and effect, whose factors have a linear correlation in only the most seldom of cases.

Environmental factors can be such things as the wind, waves, water temperature or the salt content of the water. The state of a ship will also change depending on its loading conditions or hull fouling. Ships vary among themselves in terms of their cruising speed, the efficiency of their propellers or main engine, as well as in the shape of their hull. All these factors have an impact on ship resistance and in turn on the propelling performance of a SkySails-System. To be able to predict savings, real ships must be examined under real operating conditions. In only the rarest of cases will all the needed information be available, which is why all forecatings are only approximations.

Put another way: The fuel savings achieved with the use of SkySails propulsion depend for the most part on the efficiency of the ship's propeller, on the ship resistance, the ship's speed, the wind conditions (wind speed and direction), on the routes traveled and the manner in which the crew and shipping company employ the system. This is the reason why no across-the-board statement can be made regarding fuel savings.

I'm sure the Beluga is a ship that meets the optimum requirements for this application.