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Posted

saw a photo today on another forum that the WW2 liberty ships had a top and bottom rudder, but i dont know why?, was it an adjustable setting to offset a poor build , ie to enable a straight line/course heading?

Visual search query image

Its all part of Kev's journey, bit like going to the dark side, but with the lights on
 

All the best

Kevin :omg:


SAY NO TO PIRACY. SUPPORT ORIGINAL IDEAS AND MANUFACTURERS.
KEEP IT REAL!

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Posted

Interesting subject Kevin.   I remember studying these ships in the Naval Architecture class and wish I still had my old books, but do not recall this subject (it has been close to 60 years)    I did find this paper which is quite interesting but see nothing about the rudder design to help you, sorry.    https://ww2.eagle.org/content/dam/eagle/publications/company-information/workhorse-of-the-fleet-2019.pdf

Posted

Kevin,

 

That’s called a ContraGuide rudder.   It is shaped that way to straighten flow from the propeller.

 

The propeller works by accelerating a column of water behind the ship.  The reaction to this column of water, Newton’s Third Law, is a force in the opposite direction that pushes the ship ahead. Water, however, is viscous and this viscosity causes the water in the column from the propeller to rotate.   This rotation is lost energy.  The offsets on the rudder are intended to introduce a vector opposite to that of the rotating water column, to recover the lost energy.

 

Roger

 

 

Posted (edited)
2 hours ago, Roger Pellett said:

Kevin,

 

That’s called a ContraGuide rudder.   It is shaped that way to straighten flow from the propeller.

 

The propeller works by accelerating a column of water behind the ship.  The reaction to this column of water, Newton’s Third Law, is a force in the opposite direction that pushes the ship ahead. Water, however, is viscous and this viscosity causes the water in the column from the propeller to rotate.   This rotation is lost energy.  The offsets on the rudder are intended to introduce a vector opposite to that of the rotating water column, to recover the lost energy.

 

Roger

 

 

thank you,

 

rereading the reply it wasnt two rudders then with independent movement, it was two welded together offset

 

so how was this solved,

was it better propeller design, two props, twin rudders?

 

Edited by Kevin

Its all part of Kev's journey, bit like going to the dark side, but with the lights on
 

All the best

Kevin :omg:


SAY NO TO PIRACY. SUPPORT ORIGINAL IDEAS AND MANUFACTURERS.
KEEP IT REAL!

------------------------------------------------------------------------------------------------------------------------------------------------------

On the build table

HMS Indefatigable 1794 by Kevin - Vanguard Models - 1:64 - Feb 2023

 

On hold

MHS Britannic by Kevin 

SD 14  - Marcle Models - 1/70 - March 2022 -  Bluebell - Flower Class - Revel - 1/72   

U552 German U Boat - Trumpeter -

1/48  Amerigo Vespucci     1/84 - Panart-   

HMS Enterprise  -CAF -  1/48     

Finished     

Belle Poule 1834 by Kevin - OcCre - 1/90 - French frigate - started June 2024 - - 

Hercules by Kevin - OcCre - 1/50 - Tugboat - Finished - May 2024

Nectan-Mountfleet-models-steam-trawler-1/32 - Completed June 2020

HMS Victory - Caldercraft/Jotika - 1/72 - Finished 

 Dorade renamed Dora by Kevin - Amati - 1/20 - Completed March 2021 

Stage Coach 1848 - Artesania Latina - 1/10 -Finished 

Lady Eleanor by Kevin - FINISHED - Vanguard Models - 1/64 - Fifie fishing boat

Posted
4 hours ago, allanyed said:

Interesting subject Kevin.   I remember studying these ships in the Naval Architecture class and wish I still had my old books, but do not recall this subject (it has been close to 60 years)    I did find this paper which is quite interesting but see nothing about the rudder design to help you, sorry.    https://ww2.eagle.org/content/dam/eagle/publications/company-information/workhorse-of-the-fleet-2019.pdf

thank you, i will read that when i get a chance

Its all part of Kev's journey, bit like going to the dark side, but with the lights on
 

All the best

Kevin :omg:


SAY NO TO PIRACY. SUPPORT ORIGINAL IDEAS AND MANUFACTURERS.
KEEP IT REAL!

------------------------------------------------------------------------------------------------------------------------------------------------------

On the build table

HMS Indefatigable 1794 by Kevin - Vanguard Models - 1:64 - Feb 2023

 

On hold

MHS Britannic by Kevin 

SD 14  - Marcle Models - 1/70 - March 2022 -  Bluebell - Flower Class - Revel - 1/72   

U552 German U Boat - Trumpeter -

1/48  Amerigo Vespucci     1/84 - Panart-   

HMS Enterprise  -CAF -  1/48     

Finished     

Belle Poule 1834 by Kevin - OcCre - 1/90 - French frigate - started June 2024 - - 

Hercules by Kevin - OcCre - 1/50 - Tugboat - Finished - May 2024

Nectan-Mountfleet-models-steam-trawler-1/32 - Completed June 2020

HMS Victory - Caldercraft/Jotika - 1/72 - Finished 

 Dorade renamed Dora by Kevin - Amati - 1/20 - Completed March 2021 

Stage Coach 1848 - Artesania Latina - 1/10 -Finished 

Lady Eleanor by Kevin - FINISHED - Vanguard Models - 1/64 - Fifie fishing boat

Posted

Kevin,

 

That’s right, one rudder, with two fixed offset parts.  I don’t know when or if they stopped using them; my Naval Architecture education occurred in the first half of the 1960’s and they were still being fitted to new ships.  

 

Finite element modeling, CAD, and powerful PC’s have allowed Naval Architects to analyze complex fluid flow problems that could not be solved in the 1960’s.  I would, therefore, believe that this has improved efficiency of propellers.

 

It may seem counter intuitive but propulsion efficiency is better for single screw than twin screw ships as the single propeller works in an area where it can capture more energy from turbulent water shed from the hull.  This “extra boost is called the Wake Fraction.

 

Roger

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