Modern Ships by Sail Assist

[TheMercenary]

Pretty cool.

http://www.skysails.info/english/inf...luga-skysails/

[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.

[TheMercenary]

I believe the application is sound. Maybe they just need to make it bigger, as others have stated, to have a bigger impact. I does seem to make a difference.

[xoxoxoBruce]

I agree, anyone who's flown a fair size kite or even carried an umbrella in a wind storm, knows they can give you a good pull. The little magic steering box is cool too.

I think the pictures on the site are misleading, in that the real world application would be much bigger... maybe intimidatingly so.

Their performance claims are supposedly real world data for a ship that's equipped with a sail that 1/2 to 1/3 the size they recommend. WTF?

[BigV]

xoB, I think you're making an unfair comparison about the raw square footage of the two different examples of sails. The kites in this example are designed to act as airfoils. The lift generated by the air flowing over the shape of the inflated kite is what the boat perceives as thrust/pull.

That's not directly proportional to the thrust provided by the much flatter sails of the Beluga. At 109 meters long that's longer that a 747 by about 40 meters. The 747 has about 5500 square feet of wing area and it can literally fly. Plus, the wind speed at altitude is higher than the wind speed at the surface, usually.

All I'm trying to say is the sail design works more like a wing than a parachute. The performance of the two different shapes is vastly different for a given sail area.

[Griff]

Well, let's get the damn thing on a treadmill and sort it out.

[footfootfoot]

[glatt]

Looking at the pictures on the site, I have to side with Bruce. I see no way that that particular sail they show can "temporarily reduce fuel consumption by 50%." It's too small.

[xoxoxoBruce]

Originally Posted by BigV

xoB, I think you're making an unfair comparison about the raw square footage of the two different examples of sails. The kites in this example are designed to act as airfoils. The lift generated by the air flowing over the shape of the inflated kite is what the boat perceives as thrust/pull.

That's not directly proportional to the thrust provided by the much flatter sails of the Beluga. At 109 meters long that's longer that a 747 by about 40 meters. The 747 has about 5500 square feet of wing area and it can literally fly. Plus, the wind speed at altitude is higher than the wind speed at the surface, usually.

All I'm trying to say is the sail design works more like a wing than a parachute. The performance of the two different shapes is vastly different for a given sail area.

You misunderstand me.
They said the Beluga is the freighter they are using as a sponsor/demonstrator with the 160 sq meter parasail, but they don't say how big the ship is.

They said the Sea Cloud, with 3,000 sq meters of flat sail, is 109 meters long and a freighter the same size would use a 300 to 600 sq meter parasail.

I said the Beluga looks like it could very well be in the 109 meter (358 ft) range. I see a number of freighters that size go by where I work every day. Yet they are claiming these performance figures with a parasail that's 1/3 to 1/2 their own recommendation?

They also said their are a lot of other design and performance factors of each particular ship that contribute to the parasail sizing, which makes me suspect that the Beluga was chosen because it has a combination of traits that will respond particularly well to this parasail. This is why I'm skeptical their performance claims can be accepted as an indicator of savings in general application.

I thinks we's gots us a ringer here.