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Posts Tagged ‘wing’

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Screen Shot 2015-09-24 at 10.46.14 AMThe wonders never cease in the world-famous Sailing Anarchy Forums, where people say the strangest things.  Like yesterday, when Anarchist ‘bgytr’ calculated the real-world efficiency of the fantastical sail-powered crude carrier we featured earlier in the week.  Do his numbers check out?

As a nav. arch. student, I did a thesis paper on wind assist for commercial ships.  Basically the price of fuel needs to be so high for it to work that it is not feasible.  Also,  tankers routinely take green water over the deck.  Those little sails would have to be pretty dern heavy to stand up to that.  And just everyday industrial conditions on a tanker are pretty friggin rough.  Maitenance costs of another system onboard- not reasonable.

A simple computation, under ideal beam apparent wind at 20 knots:

Assume those sails are roughly 80 feet high by 20 feet chord.  = 1600 ft^2

Lift= 0.5 r*v^2*A*C

C: lift coefficient (give a fairly generous C of 2.0)

r:  air density taken as 0.0023769 slug/ft^3

v: 20 knots = 33.8 ft/s

A:  area = 1600 ft^2

Force from one sail = 4300 lb of thrust per sail.  x 20 sails = 86000 lb of thrust.  A typical tanker of that size will crank out 80000 hp or more at about 17 knots =>  1.5 million lb of thrust.

Multiply the sail thrust by about .7 since the leeward sails will be in the wash of the windward sails => 60,000 lbs of sail thrust under ideal conditions.

60,000 / 1,500,000 = 0.04, or a 4% thrust benefit.  Not worth it when you factor the drag under headwind conditions, maintenance costs, weight, etc.  And that calc was for pretty much ideal circumstances.  Actual thrust benefit under a range of conditions would be way less.

 

September 24th, 2015 by admin

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Never mind the problems with it (and they are myriad), how cool would it be if the Ro-Ro of the future looked like this? Norwegian engineer Terje Lade says his Wind Ship (did he mean “Wing Ship”?) could be an economic reality sooner than you think; 3 or 4 years until the first one splashes.  ”It will give you a positive pull in the direction of the ship more than fifty percent of the time, as an average, without doing anything,” he said. “You don’t have to think about it. It’s so simple.”

Simple until the first storm, apparently.  Discuss here.  There’s even some video.

 

November 1st, 2013 by admin

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Konstanty Ossowski shows us his idea for a foiling…something.  If nothing else, it’s interesting wallpaper.

 

October 26th, 2013 by admin

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