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  #16  
Old 08-28-2010, 05:45 PM
apex1
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Originally Posted by DougCim View Post
Without going into any simple reasoning, I am fairly certain that adding rigid wing-type sails would do more than these spin-tube things do.

In particular, the notion of adding a "motorized" sail to save fuel seems rather odd.
~
That is not the case, the Flettner rotor is very efficient. And the rotation is provided by the exhaust gas of the diesels!
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  #17  
Old 08-28-2010, 06:21 PM
DougCim DougCim is offline
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Originally Posted by apex1 View Post
That is not the case, the Flettner rotor is very efficient. And the rotation is provided by the exhaust gas of the diesels!
Yea but restricting the exhaust gas still imparts a load on the engines, in terms of an efficiency reduction.

Take some vise-grips and crush the end of your car's exhaust pipe down to about 50% restriction, and see what it does for your gas mileage.

-------
My main question is how much power s really necessary for spinning such a device. Why not put some kind of wind-operated turbine on top of the Flettner rotor, and let the wind spin the thing too?
~
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  #18  
Old 08-28-2010, 06:28 PM
apex1
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Originally Posted by DougCim View Post
Yea but restricting the exhaust gas still imparts a load on the engines, in terms of an efficiency reduction.

Take some vise-grips and crush the end of your car's exhaust pipe down to about 50% restriction, and see what it does for your gas mileage.

-------
My main question is how much power s really necessary for spinning such a device. Why not put some kind of wind-operated turbine on top of the Flettner rotor, and let the wind spin the thing too?
~
Very little power is needed to spin them.

And thanks, I must not destroy my exhaust, I know what back pressure causes. In the example linked to by rwatson, the losses are zero, the expansion of the gas** provides the power to spin the rotors. Otherwise wasted energy.

Regards
Richard
edit:
**and conversion into electricity
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  #19  
Old 08-28-2010, 10:12 PM
Boston Boston is offline
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Originally Posted by rwatson View Post
To give you an idea of the power produced by spinning those things at 200 rpm, multiply the area of each cylinders cross section ( silhouette ) by seven. This is the equivalent sail area they replace.

An article on the effectiveness on a much smaller boat fitted with one rotor provides some actual figures

http://www.rexresearch.com/flettner/flettner.htm

Popular Science January 1984

"Power Mode --- Ave. Wind (Knots) --- Ave. Boat Speed (knots) --- Ave Fuel Saving (%)

Rotor-Assist --- 16.1 --- 7.0 --- 44
Rotor-assist --- 12.9 --- 6.0 --- 27
Rotor Sailing --- 17.7 --- 5.3 --- 100

Under rotor power alone, the Tracker reached a maximum speed of 6.1 knots in an 18.4 knot wind and a true wind angle of 122 degrees.

Bergeson is demonstrating the Tracker to fishing-boat owners, talking to large shipping companies, and presenting scientific papers at maritime conferences. And interest is growing. He now has a Navy contract to study the conversion of a military sea-lift ship to rotor-assisted propulsion. He is also conducting similar studies for a number of independent shipping companies, including major oil and cruise-ship companies.

The economic potential certainly is there. Bergeson has calculated that the world’s shipping fleet consumes 730 million barrels of petroleum a year at a cost of $30 billion. If only 20 percent of the world’s fleet adopted sail assist, the savings would be on the order of 91 million barrels a year --- almost $3 billion.

The payback to an owner can be astonishingly quick. The entire rig for the Mini Lace cost $250,000. But the owner’s records show that the sailassit saves $48,000 worth of fuel a year. In addition, average speed is increased by 5 percent, which means that the ship can make more trips. Extra income from this source was $9200. At that rate, the rig would pay for itself in a little over 4 years. But there’s more. On the New Orleans-Jamaica route, where winds are usually unfavorable, the fuel savings was an incredible 36 percent, and the speed was up 18 percent. If the ship were used on similarly favorable routes, the payback would fall to an astonishing 1.7 years. "
thats a pretty dam convincing argument there Mr Watson
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  #20  
Old 08-28-2010, 10:28 PM
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rwatson rwatson is offline
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Quote:
Originally Posted by apex1 View Post
Reportedly she did perform well. No real wonder, the "turbo sail" is nothing else but a Flettner rotor. Cousteau developed a new name, nothing else.

Regards
Richard
The Coaustea boat was a totally different scheme. It consisted of very fat non rotating aerofoil masts with a series of opening holes near the rear of the lifting surfaces on each side of the mast.

The pressure differential was achieved by opening the holes in the leeeward side of the lifting surface, and using fans to suck air into the mast itself, thereby creating a negative pressure differential.

Re the "Tracker" info, I have searched online for articles, to no avail over the years. In the spirit of preserving the information on line, I have taken the liberty of photycopying the article for all to review. I am sure that after over thirty years that the magazine would appreciate the publicity.

Also , as a point of interest, I have also included an image of a Flettner Windmill that was built and working - to help demonstrate that smaller scale rotors will work.

In my bones, I feel that with the modern, precision technology of today (especially with carbon fibre/resin technology) , that rotors have real potential to provide a usefull role for many wind assisted vessels.
Attached Thumbnails
Everything Old is new again - Flettner Rotor Ship is launched-flettnerboat00.jpg  Everything Old is new again - Flettner Rotor Ship is launched-flettnerboat-001.jpg  Everything Old is new again - Flettner Rotor Ship is launched-flettnerboat002.jpg  

Everything Old is new again - Flettner Rotor Ship is launched-flettnerboat003.jpg  Everything Old is new again - Flettner Rotor Ship is launched-windmill.jpg  
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  #21  
Old 08-28-2010, 10:37 PM
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rwatson rwatson is offline
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Scale of Sail V Rotor

Quote:
Originally Posted by DougCim View Post
Without going into any simple reasoning, I am fairly certain that adding rigid wing-type sails would do more than these spin-tube things do.

In particular, the notion of adding a "motorized" sail to save fuel seems rather odd.
~
It does seem odd indeed Doug. But, to illustrate the effect, if you were to make spinning cylinders with the section ( silhouette if you like) of any given sail or aerofoil surface, a spinning cylinder with "gates" at both ends, generates over ten times the amount of lift as a conventional foil surface.

It has intrigued me no end over the last forty years.

PS. I have added an illustration from the original study done on rotor sail designs
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Everything Old is new again - Flettner Rotor Ship is launched-sailexample.jpg  

Last edited by rwatson : 08-29-2010 at 12:16 AM. Reason: add illustration
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  #22  
Old 08-28-2010, 10:56 PM
apex1
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Thanks for the article!
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  #23  
Old 08-28-2010, 11:49 PM
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rwatson rwatson is offline
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Originally Posted by apex1 View Post
That is not the case, the Flettner rotor is very efficient. And the rotation is provided by the exhaust gas of the diesels!
I have never come across any mention of rotors being driven by exhaust gases.

In every case they were rotated using small auxilliary motors.
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  #24  
Old 08-29-2010, 06:44 AM
apex1
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Originally Posted by rwatson View Post
I have never come across any mention of rotors being driven by exhaust gases.

In every case they were rotated using small auxilliary motors.

Your link:

http://www.oldsaltblog.com/2010/08/1...nally-arrived/
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  #25  
Old 08-29-2010, 07:54 AM
DougCim DougCim is offline
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The Flettner rotor is a solution in search of a problem.

......It is most certainly not a sail, if it needs engine power to function--it is only a method of converting engine power.

......If it generates seven times as much as an airfoil the same size, they why is it not used on any production aircraft, or as the propulsion method for any aircraft? I've seen a number or articles about experimental models, but for some reason all those dumb guys over at Airbus and Boeing keep sticking with the same old airfoil wings (-and airfoil engines...).

......DIY boatbuilders are free to try anything they want, and yet there's a sizable list of other innovations that are far more common than Flettner rotors: Kort nozzles, winged keels, keel bulbs, hydrofoils, rigid-wing sails, torpedo tubes and variable-pitch props to name just a few. Other than this publicity stunt by Enercon, the original Flettner boat and the Cousteau boat, how many Flettner-rotor boats even exist? I'd bet not very many, compared to anything else in that list.

.....I've no doubt the principle works, but it's not as useful as inferred. Enercon themselves doesn't even make any wind turbines using Flettner rotors.
~
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  #26  
Old 08-29-2010, 08:25 AM
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TeddyDiver TeddyDiver is offline
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Quote:
Originally Posted by DougCim View Post
......If it generates seven times as much as an airfoil the same size, they why is it not used on any production aircraft
But it is.. thou a bit different implement with a blower instead of rotating the tube..
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Everything Old is new again - Flettner Rotor Ship is launched-air_md-900_explorer_lg.jpg  
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  #27  
Old 08-29-2010, 12:06 PM
apex1
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Originally Posted by DougCim View Post
The Flettner rotor is a solution in search of a problem. ~
I would strongly recommend to study the topic before you make yourself a clown.

Especially the Magnus effect is the point you are missing.

Wind turbines are not ships, they don´t sail either. Enercon knows that.

Regards
Richard
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  #28  
Old 08-29-2010, 01:58 PM
DougCim DougCim is offline
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Originally Posted by TeddyDiver View Post
But it is.. thou a bit different implement with a blower instead of rotating the tube..
Well maybe not.
Wikipedia says the NOTAR system uses the Coanda effect, as the tail boom of the MD-500 does not revolve. The Magnus effect is a property of boundary layer flows around a rotating tube.

--------

The Flettner rotor is 88 years old; when modern industry with its engineers and accountants won't touch an invention that is well into the public domain, that tells you pretty much all you need to know about its usefulness.

Has the Flettner rotor gained widespread use in any industry? For any purpose?
~
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  #29  
Old 08-29-2010, 02:21 PM
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philSweet philSweet is online now
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does anyone have a graph showing the force and DIRECTION of force relative to incident wind as a function of rotor speed?

I also thought of the Cousteau wing in connection with this. Would pulling suction on a small forward area of the rotor help to keep the lift aligned with the ship as apparent wind changes?

What about a "peeler" to control aft separation and influence thrust direction?

searching "Magnus effect" seems to get better stuff than "Flettner"
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  #30  
Old 08-29-2010, 02:35 PM
apex1
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Originally Posted by DougCim View Post
Well maybe not.
Has the Flettner rotor gained widespread use in any industry? For any purpose?
~
Wiki might be not the most knowledgeable source of info, don´t you think?

In the past 80 years NOTHING was brought really further related to wind power in our industry. That does not prove it is the wrong way.

The Flettner rotor has proven it does what it is expected to do, saving a lot of fuel. That was valid in 1925 and it is still today.

The fact that YOU don´t like it, does not make any difference. Most probably you don´t like it because you don´t understand it.

In the years when Flettner developed it, nobody in the shipping world was interested in wind power. The fuel (coal) was dirt cheap and the steamers replaced the tall ships in these days. Everybody was going "modern".
Times change, and we see several new attempts to reinvent the wheel.
In this case that is not necessary, it is already there.

BTW
Albert Einstein was a true admirer of Flettners Rotor, maybe he had a better understanding of the system:
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