Everything Old is new again - Flettner Rotor Ship is launched

[CT249]

The paper also projected a payback period of 8.8-14 years - but the lower end only comes into play if the ship does fewer voyages and therefore earns less money. The compelling case only applies to owner-operators, not to time or voyage charterers. I'd love to see Co2 emissions drop but the compelling case didn't apply to many operators.

 

[Herreshock]

This is

Neither do sails. What is your point ??

Meantime, the actual study done for these diagrams says Rotors are a "compelling case"

View attachment 199948

https://www.researchgate.net/public...Commercial_Ships_A_Techno-Economic_Assessment

This is ac72 with multi element rigid wingsails

Look at that, flexible windgsails have better upwind traits than rigid wingsails and any current "performance boat" using common fabric sails look pretty lame compared, and still the myth of keeled sloop upwind fallacy is still there

 

[rwatson]

This is
This is ac72 with multi element rigid wind sails
Look at that, flexible windgsails have better upwind traits than rigid wingsails and any current "performance boat" using common fabric sails look pretty lame compared, and still the myth of keeled sloop upwind fallacy is still there

Of course. Performance isn't the major benefit.
I started a thread on the topic The case for fully automated sailing rigs https://www.boatdesign.net/threads/the-case-for-fully-automated-sailing-rigs.69564/

The need for managing the equivalent of huge sail rigs using automated systems in complete safety is a big benefit.
Can you imagine having the three crew members of a 100,000 racing around the decks adjusting, trimming, optimising sails like the poor sods in "The Ocean Race" currently pounding their way across the Southern Ocean.
----------------------------------------------------------------------------------------------------------------

But, as far as tested, documented performance, lets look at an actual comparison study .
https://www.tandfonline.com/doi/full/10.1080/17445302.2019.1612544#d1e628

Not so very different performance Polars comparing sophisticated sail systems with Rotors, and as noted in the Rotor description, the power required to turn the Rotors was included in the calculations.
PLUS
Vastly reduced Heel performance
The small space this technology requires on deck in comparison with the other two sail technologies
The ability to move the Rotors to help with Cargo operations

Between Safety, Ease of Handling, Comparative Performance the benefits of the Rotors stack up.

 

[Herreshock]

Of course. Performance isn't the major benefit.
I started a thread on the topic The case for fully automated sailing rigs https://www.boatdesign.net/threads/the-case-for-fully-automated-sailing-rigs.69564/

The need for managing the equivalent of huge sail rigs using automated systems in complete safety is a big benefit.
Can you imagine having the three crew members of a 100,000 racing around the decks adjusting, trimming, optimising sails like the poor sods in "The Ocean Race" currently pounding their way across the Southern Ocean.
----------------------------------------------------------------------------------------------------------------

But, as far as tested, documented performance, lets look at an actual comparison study .
https://www.tandfonline.com/doi/full/10.1080/17445302.2019.1612544#d1e628


View attachment 199968


Not so very different performance Polars comparing sophisticated sail systems with Rotors, and as noted in the Rotor description, the power required to turn the Rotors was included in the calculations.
PLUS
Vastly reduced Heel performance
The small space this technology requires on deck in comparison with the other two sail technologies
The ability to move the Rotors to help with Cargo operations

Between Safety, Ease of Handling, Comparative Performance the benefits of the Rotors stack up.

Already there are free-standing masts ignored by current sailboat designers and also lower and high aspect ratio sails also reduce heel

And small sailboats can transport cargo for free so no need for these behemoths that fuel consumerism

Today Im focusing in low height multi mast thin flexible wingsails acting as multi element wing and these are the present of safe engineless sailboats

 

[rwatson]

Already there are free-standing masts ignored by current sailboat designers and also lower and high aspect ratio sails also reduce heel

No, not ignored. Uninsurable
Just been reading some posts on the Proa Forums, where they cannot get Insurance for unstayed masts.

And small sailboats can transport cargo for free so no need for these behemoths that fuel consumerism

Nice dream, but totally unrealistic. Until you can reduce civilisation to the stone age, you are looking at " 30 million twenty-foot equivalent units (TEU) of cargo are expected to be transported across the Pacific Ocean in 2024"

Today Im focusing in low height multi mast thin flexible wingsails acting as multi element wing and these are the present of safe engineless sailboats

They must be magic masts, able to conjure up their own optimum winds. There is no such thing as a "safe engineless" yacht, especially one engaged in commercial operations.

 

[Herreshock]

No, not ignored. Uninsurable
Just been reading some posts on the Proa Forums, where they cannot get Insurance for unstayed masts.


Nice dream, but totally unrealistic. Until you can reduce civilisation to the stone age, you are looking at " 30 million twenty-foot equivalent units (TEU) of cargo are expected to be transported across the Pacific Ocean in 2024"



They must be magic masts, able to conjure up their own optimum winds. There is no such thing as a "safe engineless" yacht, especially one engaged in commercial operations.

Who cares about insurers? Already freestanding masts are safer, they bend and if they break is at the base just like laser masts and can be reinserted with few tools cutting the base from the rupture point


Rather 1950s-80s Consumerism is a nightmare and humanity has lasted millenniums without it, check your bias we can cut transportation by almost 99% just by growing local food, wood and textiles and closing landfills reusing everything

If you see ac72 catamaran wind polar diagram thats a safe engineless boat, besides a sail is a sort of wind engine blade


Check your bias

 

[rwatson]

Historic details of the original Flettner Ships.

The first illustration is the before and After pictures of the first Rotor Ship, the Baden Baden

And her sister ship, who worked the Mediterranean for 6 years.

Courtesy of Professor Hubert Chanson

 

[rwatson]

In depth report on Flettner Rotor design.

 

[rwatson]

An interview with an actual Captain of a Rotor Ship

 

[rwatson]

Some comments about Rotor Sail safety, found

ECO FLETTNER rotor sail stands the test - Industry insights - Maritime Impact https://www.dnv.com/expert-story/maritime-impact/ECO-FLETTNER-rotor-sail-stands-the-test/#:~:text=The%20painstaking%20preparations%20paid%20off,conditions%20the%20vessel%20may%20experience.

 

[rwatson]

Gearing up with a dedicated factory on China

"8 Jul 2025
Anemoi Marine Technologies, a global leader in wind propulsion solutions, is proud to announce the official opening of its new Rotor Sail production facility in China. This landmark development significantly enhances Anemoi’s manufacturing capabilities and underscores its commitment to accelerating the maritime industry’s transition to zero emissions. Strategically located on the banks of the Yangtze River, Anemoi’s facility is located in Jingjiang City, Jiangsu Province, within Daming Heavy Industry’s manufacturing base. The facility provides direct access to port infrastructure, enabling seamless logistics for import, export, and delivery. With barge transport available on-site, Rotor Sails can be transported efficiently and installed directly at nearby major shipyards, streamlining operations and minimising environmental impact."

 

[kerosene]

Norsepower started a Chinese factory last year too. They have been getting fair bit if industry press here in Finland.

Norsepower launches world’s first dedicated rotor sail factory, consolidates leadership of the wind propulsion market - Norsepower Rotor Sails™ | Wind Propulsion https://www.norsepower.com/post/norsepower-launches-worlds-first-dedicated-rotor-sail-factory-consolidates-leadership-of-the-wind-propulsion-market/

 

[kerosene]

Norsepower turned 1stvprofit in 2023, which is the latest date for public filings.
Still very small but a big milestone regardless. Interesting to see how it goes but seems they have clients and production is ramping up.