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Tandem and Contrarotating Propellers - Coggle Diagram
Tandem and Contrarotating Propellers
Tandem
Propellers in same shaft
After one
needs high pitch
to give same power
Contrarotating
One for each side
After one
smaller diameter
Largely used
in torpedoes
Advantages
Smaller diameter screws
Higher blade frequency
Improved vibration characteristics
Disadvantages
Large weight
Sealing problems
Coaxial shafting
Good torque balance
Higher efficiency
than single propellers
Better control
over cavitation
Tanker Manhattan experiments
Original - Twin Screws
Single Screw 5 Blades
Required 0,4% less power
Single Screw 9 Blades
Required 4% MORE power
Tandem
Around 2% MORE power
Contrarotating
7% less power
