Quote:
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.
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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.
