# Flettner Rotor System



## seaman38 (Mar 16, 2016)

Have any of our brethren sailed with the Flettner Rotor System, tall rotating cylinders on deck reputed to save fuel consumption. Have watched a few videos and for those on the bridge a noisy experience. A bulker had four fitted on the starboard side all taller than the bridge, it would appear that no thought had been given to safe navigation with so many obstructions on the stb'd side, preventing a clear vision to what a navigator could consider his most dangerous side having to give way to vessels (if he can see them, yes I know we have radar!) approaching on that side. Just the thoughts of an old codger (Smoke)


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## alaric (Feb 27, 2012)

Pity there has been no response to this post.
The theory is sound and the rotors do generate a propulsive force that helps power the ship.
There have been a number of experimental rotor ships at sea, the first being the Bruckau in 1924, almost 100 years ago. Vague claims of 20-25% reductions in fuel consumption have been made, but very few, if any authoritive reports have been published in all that time.
There must be a big snag, 25% fuel savings are too good not to be utilized in today's carbon reduction world. There must be more to it than not having a good view from the bridge. Piling containers far too high seems to be acceptable.
It would be good to hear from any member who has sea-going rotor experience. Viking and Maersk have, or are about to have rotor ships at sea according to Wiki.


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## price (Feb 2, 2006)

Hello Alaric, I posted in a previous forum about Flettner Rotor Ships. A photo and short account can be found in my photos (Price) 20th. sept 2007. with a photo of my late first cousin taken aboard one of the ships in Keil Harbour about 1925


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## seaman38 (Mar 16, 2016)

price said:


> Hello Alaric, I posted in a previous forum about Flettner Rotor Ships. A photo and short account can be found in my photos (Price) 20th. sept 2007. with a photo of my late first cousin taken aboard one of the ships in Keil Harbour about 1925


Thanks for your post, interesting (astounded I managed to find it!). It would be interesting to hear from someone who has sailed with the modern version, because the clips I saw it seemed it did the bridge watch no favours.

Also be interesting to hear from someone other than Flettner about the actual, rather than theoretical fuel savings, as they quote 25%, but that is open, as surely that would depend upon the vessel's co-efficient of fineness. Latest research shows that the bulbous bow increases fuel consumption if a vessel completes a passage on 'slow steaming' in fact Maersk put new shorter bulbous bows on some of their current vessels, as decided to operate them at 16/17 knots instead of 21/22 knots and apparently fuel consumption has gone down dramatically, which it didn't with the original bulbous bow.

The bulbous bow is certainly a mixed blessing, in the old days hitting a vessel with your bow usually meant damage above the waterline due to the flare and vessel may be able to continue on passage, but with the projecting bulbous bow the damaged is now invariably below the waterline of the receiving vessel causing more severe damage where-in the receiving vessel may not be able proceed on passage.

Its called progress.


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## Stephen J. Card (Nov 5, 2006)

Just found this original post! Most interesting. I spoke to a shipowner two weeks ago and he said they were thinking about a new ship with the Flettner system. Anyhow this all makes good reading... especially 'hands on' information.

Thanks.

Stephen


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## alaric (Feb 27, 2012)

Some interesting up to date reading; http://en.marigreen.eu/ecoflettner-installation
Positive comments but short on hard data.
EU funded.
Go to bottom of page and scroll up to read.


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## seaman38 (Mar 16, 2016)

alaric said:


> Some interesting up to date reading; http://en.marigreen.eu/ecoflettner-installation
> Positive comments but short on hard data.
> EU funded.
> Go to bottom of page and scroll up to read.


As you say interesting reading, but it would seem conjecture about the efficiency, surely if they were monitoring it as they say, they would have produce some figures no matter how infintissimal the improvement. Doubt the quartermaster would see many leading marks with that monstrosity stuck on the f'cle. However full marks for trying


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## alaric (Feb 27, 2012)

Have just been digging a bit deeper to find; 



A short presentation given recently by Prof. Capt. Michael Vahs who is heading up the MV Fehn Pollux rotor ship project.
All good common sense stuff which I don't argue against, but I wish he would actually publish the data to back up his claims and projections.
If we see a sudden boom in sales of retro-fit Flettner kits we will know the claims are true, but until then I still feel there is a snag that we are not being told about.
Could it be that most of the savings are being lost by having to steer a constant zig-zag course to a) catch a favourable wind, and/or b) to actually see where the ship is heading?


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## alaric (Feb 27, 2012)

The U-tube link is www.youtube.com/watch?v=5XdCEubz_R4


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## seaman38 (Mar 16, 2016)

alaric said:


> The U-tube link is www.youtube.com/watch?v=5XdCEubz_R4


Thank you for posting, interesting.

48 minutes of conjecture, with no facts, as far as I could ascertain (as usual I stand to be corrected). I wonder how many were still awake at the end of his monotone presentation.

The illustration of the passenger vessel (projected for 2050!) with all those rotors on the top sun/promenade deck begs the question, when booking do you get a supply of free ear plugs.

On larger vessels I wonder how much of the DWCC is lost because of these large structures on deck, and from a stability point of view will larger ballast tanks be need, thereby possibly cutting down the hold cubic capacity.

On a lighter note, if he uses all the coconuts in the Pacific for bio fuel, where are we going to get coconut cream to put in our curries. He says there will be an almost endless supply, but surely not if all vessels in the region use coco-bio


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## alaric (Feb 27, 2012)

I have just posted a photo of the Rotor assisted Ro-Ro Estraden.
Should meet with Seanam38's approval as the positioning of the rotors does not obscure the view from the bridge and it is probably the ideal size for the Ramsgate service?
To take my mind off Brexit votes, thinking about this layout led me to consider using the rotors as funnels. Aesthetically more pleasing than many modern ships which have a variety of ugly pipes sticking out of their stacks, but more importantly, can any propulsive effect be gained from this arrangement?
Adrian Newey, one of this countries outstanding Engineers has been able to generate considerable downforce (=faster cornering) by directing engine exhaust energy in his Formula 1 designs. 
Motor racing now employs hundreds of clever aerodynamists, all trying to gain fractions of a second advantage in reducing lap times. If some moved over to shipping and applied their knowledge and ingenuity to rotor funnel design real progress could be possible?


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## seaman38 (Mar 16, 2016)

#11 Yes the F1 boys are certainly amongst the leaders in aerodynamic design, perhaps we should tell Flettner (Read)


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## skilly57 (Mar 11, 2008)

With regard to post #4 and Seaman 38's comment about the bulbous bow consumption, in November 2000 I spent 3 weeks at the testing tank at the AMC in Tasmania. We were operating a self-discharging bulk cement carrier built in 1978/79 by Robb Caledon's in Dundee. The ship's original spec stipulated the fitment of a bulbous bow, but then that item was deleted. 
With fuel prices rising at the turn of the century, the then owners were looking for ways of reducing fuel consumption, so I got nominated to investigate.
Got a 2 metre long model of the hull made off the lines plans (a beautiful job, by a Tasmanian boat builder). The AMC's large computer was set to work doing computational fluid dynamics calculations to determine 2 bulb sizes to be trialled. 
Preparing for the tank test runs, loaded the model down to normal marks, and off we set down the tank, with myself & the operator sitting on the carriage above. In total we did 94 runs, the first set with no bulb, the second set with the small bulb, and the 3rd set of runs with the largest bulb. Scale speeds ranged from 7 to 17 knots.

The amount of computer data being downloaded from the strain gauges attached to the hull was incredible. The results showed the larger bulb gave us a 7.1% reduction in resistance at service speed of 14 knots.

Then I asked for all the runs to be repeated, with the model in ballast condition. But why, was the reply. Because I asked for this to be done months ago in our early correspondence on the test format, but the AMC people thought I was over the top I think!

The results were stunning! With either bulb fitted, there was a large increase in fuel consumption at all speeds up to 13.5 knots! The resistance increase was 25% at 13.5 knots with the largest bulb fitted. It transpired that as soon as the top of the bulb remained dry, fuel savings disappeared as the bulb became ineffective! The bulbs were only effective over a very narrow speed band (3 knots range), and only when the vessel is in a loaded condition that will keep the bulb continually immersed.

I had all the certified steel waiting in NZ to do the installation at the imminent docking, but immediately cancelled the manufacture of the bulb. It turns out those naval architects at Robb Caledon knew that vessels that spend half their time in ballast derive no benefits from fitment of a bulbous bow, and so had deleted the bulb from the original spec.

Now, I look at all the ships I see running around with their bulb tops up and dry and wonder if they realise how much fuel they are wasting!

Model photos attached.


First photo shows model of the hull as built, and as she still is today (she has just arrived in Iceland with a cargo of cement from Aalborg). Built in Scotland - keel laid 41 years ago, and still going strong!


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## seaman38 (Mar 16, 2016)

skilly57 said:


> With regard to post #4 and Seaman 38's comment about the bulbous bow consumption, in November 2000 I spent 3 weeks at the testing tank at the AMC in Tasmania.
> 
> First photo shows model of the hull as built, and as she still is today (she has just arrived in Iceland with a cargo of cement from Aalborg). Built in Scotland - keel laid 41 years ago, and still going strong!


Thanks for an interesting post Skilly, nice to hear from someone with first hand experience, I think the BB became a fashion statement as much as anything else, I remember reading years ago that it was not all things to all men, but the Naval Architect who presented the paper was told that his calculations may be suspect, bet he's laughing now.


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## alaric (Feb 27, 2012)

See #11 .
As Adrian Newey is probably too busy at the moment I have been giving the rotor funnel idea some thought myself and have passed it along to Norsepower for their views. Norsepower is the company who did the Ro-Ro Estraden installation and have also got Rotorsails at sea on a Viking ferry and a Maersk tanker.
For Attn. Tuomas Riski, CEO Norsepower.

Some pipe dreaming from a retired Engineer who admires the good work your company is achieving improving shipping efficiency and environmental standards.

It occurs to me that further gains are possible by eliminating conventional funnels and utilizing rotors in their place. It is envisaged that exhaust gases are directed into the base of the rotor and are released at the top via vectoring nozzles which would control the rotational direction and speed of the rotor.

This arrangement has a number of potential benefits;
•Electrical power to spin the rotors reduced or eliminated.
•Cleaner airflow onto/off rotor. 
•Generating deck space.
•Exhaust gas released at higher level.
•Improved aesthetics.
I appreciate that one of the major selling points of your system is it’s basic simplicity, and my proposals would undoubtedly increase complexity and first cost. However, the technology is proven (Harrier jump jet) and if these nozzles prove to be capable of eliminating the electric drive altogether the extra costs would be reasonable if applied to a new build rather than a retro fit project.

I would be interested to hear your views on the concept, could it be a viable system, or should it remain a pipe dream?

Should you decide to investigate the proposal further I do not want to have any involvement, but if a nozzle rotor ever gets to sea I would love to be on board to see how it sails. I will bring my own earplugs!


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## seaman38 (Mar 16, 2016)

#15 . Thanks for that, lets hope that they have the courtesy to reply, with thanks for showing an interest and perhaps an invitation to an installation.

I am surprised by the lack of comment or observations by our fellow seafaring members on this and similar subjects, as although being retired for many years developments in our industry still hold my interest.

Whoever thought that we would see vessels with reverse bows and other features reminiscent of illustrations first seen in the adventures Dan Dare so many moons ago which many naval architects of the day would have considered pure fantasy and impossible to achieve.


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## Duncan112 (Dec 28, 2006)

alaric said:


> See #11 .
> As Adrian Newey is probably too busy at the moment I have been giving the rotor funnel idea some thought myself and have passed it along to Norsepower for their views. Norsepower is the company who did the Ro-Ro Estraden installation and have also got Rotorsails at sea on a Viking ferry and a Maersk tanker.
> For Attn. Tuomas Riski, CEO Norsepower.
> 
> ...


There is a bit of "Form" associated with this type of idea, I understand it was quite noisy!! https://en.wikipedia.org/wiki/Fairey_Rotodyne


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## seaman38 (Mar 16, 2016)

Duncan112 said:


> There is a bit of "Form" associated with this type of idea, I understand it was quite noisy!! https://en.wikipedia.org/wiki/Fairey_Rotodyne


Hmmm! did I not mention that in #1 (Smoke)


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## Duncan112 (Dec 28, 2006)

seaman38 said:


> Hmmm! did I not mention that in #1 (Smoke)


Not this one 



 with exhaust bleed to spin the rotors which is where we have gone now.(==D)(==D)


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## alaric (Feb 27, 2012)

#17 
The Rotodyne was in mind when I mentioned that I would bring my own ear defenders Duncan.
Not really necessary in my case because I am already deaf, caused by diesel exhaust gas being expanded through a nozzle. Turbochargers.
But I accept that noise is the most difficult technical problem that will need to be overcome if the concept is taken up, even on non passenger ships.
However, the Fairy design actually had jet engines in the rotor tips, I am suggesting directing existing exhaust gas trough nozzles. Not quite in the same league regarding noise generation but still a problem I fear.


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## seaman38 (Mar 16, 2016)

Duncan112 said:


> Not this one D)(==D)


Whoops sorry ! must take my own medicine and read properly


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## Duncan112 (Dec 28, 2006)

alaric said:


> #17
> The Rotodyne was in mind when I mentioned that I would bring my own ear defenders Duncan.
> Not really necessary in my case because I am already deaf, caused by diesel exhaust gas being expanded through a nozzle. Turbochargers.
> But I accept that noise is the most difficult technical problem that will need to be overcome if the concept is taken up, even on non passenger ships.
> However, the Fairy design actually had jet engines in the rotor tips, I am suggesting directing existing exhaust gas trough nozzles. Not quite in the same league regarding noise generation but still a problem I fear.


The thing that has always interested me is how the fuel and air connections between the rotor assembly and fuselage worked - the internet is strangely silent on this?


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## alaric (Feb 27, 2012)

Duncan112 said:


> The thing that has always interested me is how the fuel and air connections between the rotor assembly and fuselage worked - the internet is strangely silent on this?


The whole design seems to have worked very well considering the lack of modern aids available in the 1950s. Have been looking on the internet but can't find any detail on the rotor head. 
Like you, my memory was that the Rotordyne project was scrapped because of the high noise levels, but the 4 part film on U-tube suggests that this was not the case. The film makers say it was government directed industry re-organisation that killed off this promising concept. The film was made by Fairy Aviation and this opinion may well be a little biased? 
But maybe, just maybe we might yet have exhaust driven rotor sails helping to save our planet?


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## Dartskipper (Jan 16, 2015)

alaric said:


> The whole design seems to have worked very well considering the lack of modern aids available in the 1950s. Have been looking on the internet but can't find any detail on the rotor head.
> Like you, my memory was that the Rotordyne project was scrapped because of the high noise levels, but the 4 part film on U-tube suggests that this was not the case. The film makers say it was government directed industry re-organisation that killed off this promising concept. The film was made by Fairy Aviation and this opinion may well be a little biased?
> But maybe, just maybe we might yet have exhaust driven rotor sails helping to save our planet?


Fairey Aviation were also heavily involved with developing high speed interceptors, working on the successful FD2 supersonic research aircraft. That was another opportunity lost, as due to restrictions on sonic booms over the land, they flew it in France and it is alleged that it inspired the Mirage designed by Marcel Dassault. There is a strong similarity with the designs. At the same time they worked on larger aircraft, in competition with other companies, so perhaps the Rotodyne became surplus to requirements and funding ran out.


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## alaric (Feb 27, 2012)

Dartskipper said:


> Fairey Aviation were also heavily involved with developing high speed interceptors, working on the successful FD2 supersonic research aircraft. That was another opportunity lost, as due to restrictions on sonic booms over the land, they flew it in France and it is alleged that it inspired the Mirage designed by Marcel Dassault. There is a strong similarity with the designs. At the same time they worked on larger aircraft, in competition with other companies, so perhaps the Rotodyne became surplus to requirements and funding ran out.


Yes Roy, we discussed this probable case of industrial espionage on 18th July last year, on the other site.
Westland killed off the Rotodyne?
Or was it really the noise?


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## alaric (Feb 27, 2012)

I am delighted to have received this reply to my post #15 .

Many thanks for contacting Norsepower: it is always nice to receives ideas like this one. We have actually heard part of this idea before: there is a patent for a Flettner rotor, which has been built around the funnel. If I remember correctly, the patent owner is Wärtsilä, and the inventor is Mr Oskar Levander. Anyhow, we have never before heard the idea of rotating the Flettner rotor with the exhaust gases. 

I have cc’d to this message our CTO, who will have a look at this idea and possibly revert to us with some comments. My initial concerns are the added complexity of the product (which you have also noted), and potential issues caused by the poisonous / toxic gases, but it might also be that these would be simple to be solved.

Kind regards,

Tuomas Riski


I will be even more interested in hearing the considered technical response which I will share on this forum.


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## alaric (Feb 27, 2012)

alaric said:


> I am delighted to have received this reply to my post #15 .
> 
> Many thanks for contacting Norsepower: it is always nice to receives ideas like this one. We have actually heard part of this idea before: there is a patent for a Flettner rotor, which has been built around the funnel. If I remember correctly, the patent owner is Wärtsilä, and the inventor is Mr Oskar Levander. Anyhow, we have never before heard the idea of rotating the Flettner rotor with the exhaust gases.
> 
> ...


Have not heard anymore from Norsepower regarding driving the rotor by exhaust gas, but some further performance figures have just been published in MEM Weekly News;


INDEPENDENT TESTS CONFIRM ROTOR SAIL SAVINGS


Thursday, May 16, 2019 


Norsepower, a provider of auxiliary renewable wind energy propulsion systems, has announced that independent test results showed that its Rotor Sail technology has great potential to deliver savings on a Viking Line gas-fuelled ro-pax ship. 


Long term LNG marine fuel savings for the Viking Grace are expected to be up to around 300 tonnes annually, equalling an average propulsion power from the wind-power system between 207kW and 282kW.

When looking at fuel consumption alone over the measurement period, the savings were not immediately evident. However, analysis by NAPA and ABB isolated an evident change in the propulsion power breakdown of Viking Grace, caused by the Rotor Sail. The same conclusion was confirmed with a strain gauge analysis, where forward thrust of the Rotor Sail was measured and converted into propulsion power. According to the analysis results, the Rotor Sail delivers more forward thrust on the open sea legs of the route for the Viking Grace, but due to the route being located mostly in the archipelago, the annual fuel savings potential is on the same level within both route areas.

As a result, Viking Line and Norsepower have agreed to continue collaboratively using and optimising the Rotor Sail on the Viking Grace with the technology now fully operational. 

Tuomas Riski, CEO, Norsepower, said: “When the test period began, we had some challenges with our new product, but were able to fix them quickly, and since the end of September 2018, the technical availability of the Rotor Sail has been around 97%. We are pleased to see that independent testing from respected, independent companies NAPA and ABB has shown impressive fuel savings potential on the Viking Grace. This project has confirmed, that our technology works also with high-speed cruise ferries and that favourable results can be achieved with a service speed of 21 knots. During the last year we have been using the Rotor Sails in extreme weather conditions including icing events and high wind speeds, in which the Rotor Sail has been operational. Based on the harsh weather experiences so far, the Rotor Sail can be operated around the year without any weather-related issues.”

Commenting on the trials, Jan Hanses, CEO, Viking Line said: “We want to pioneer the use of solutions that reduce the environmental load. Viking Line has been testing the Rotor Sail on Viking Grace for a year now, and together with Norsepower we will continue the testing and optimising the sail for its current route. We are proud to be the first in the world to trial Norsepower’s world-class mechanical rotor sail solution.”

“This analysis showcases the importance of onboard data collection and the value of ABB’s analytical services. Besides optimizing operations through improved energy efficiency on board Viking Grace, the data collected by ABB Ability Marine Advisory System Octopus was used to calculate the savings gained from the Rotor Sail without disturbing operations,” said Marcus Högblom, Head of Passenger Vessel segment, ABB Marine & Ports.

NAPA added: “In the actual navigational conditions there is always variation in the environment, which has important effect on the fuel consumption. This is why a statistical regression model was applied, to overcome the variations in the comparison conditions and to disclose the effect of the rotor sail. The long history of NAPA on ship performance modelling gave a really good basis for the study.”

The Norsepower Rotor Sail Solution, which can be installed on new vessels or retrofitted on existing ships without off-hire costs, is a modernised version of the Flettner rotor. The solution is fully automated and senses whenever the wind is strong enough to deliver fuel savings, at which point the rotors start automatically. In addition to the installation onboard the Viking Grace, Norsepower’s Rotor Sail Solution is installed onboard Bore’s Estraden, a 9,700 DWT ro-ro carrier and Maersk Tanker’s 110 000 DWT Maersk Pelican.



Article published in Propulsion & Machinery


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## alaric (Feb 27, 2012)

Although I have not had any further response to my idea of rotating the rotor with exhaust gas, see #26 I keep an eye open for Flettner news.
Norsepower has recently announced they have an order for retro fitting a large 30 x 5m rotor to the ferry Copenhagen in 2020.
The existing ferry installation on Viking Grace has a rotor of 24 x 4m and has been saving c300 tonne pa of fuel on a non optimal route.


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