Is it essential for a ship to be made with counter rotating propellers?

Question

Is it essential for a ship to be made with counter rotating propellers?

Answer 1

The answer is No! I was once a volunteer engineer on a converted fishing trawler (Torbay Lass, which originally used sail when built in 1923) When I was on it in the noughties as the Kenya Jacaranda, it's engines were two Ford Transit diesels side by side driving a shaft each. Both shafts turned the same way, clockwise. I did a number of longish pilotage runs under power with no adverse steering affects and did not even notice a pull on the tiller. For the record it was registered as 80 tonnes.

Answer 2

It's not essential but it is the most efficient way.



In small craft, a boat with counter rotating props is easier to control. Some twin engine boats without counter rotating props are difficult to steer out of a high speed hard turn to one side.



More often than not, the counter rotation is created in the transmission or marine gear just aft of the engine.



Counter Rotation: If looking at the stern of your vessel from behind it, the propeller(s) to the right of amidships would rotate clockwise relative to your position and the propellers to the left would rotate counter clockwise.

Answer 3

Essential, absolutely not. More efficient yes, but any experienced mariner knows the capabilities and the weaknesses of the set up he (or she) is using. Most older vessels with twin screws or other wise tend to have a preferred approach angle and side to dock on. Most commercial boats I have driven were set up just like this, for instance one boat always was docked with the starboard side to the wharf - that was the side we approached the gear on, and the only open side of the boat anyway unless we took the clears off and moved the deck gear. My current single screw tunnel hull works to the port side, but that's my choice as I'm left handed and steer with the right hand while gaffing/gear handling with the left. A second or two of ahead or astern thrust with the rudder amidships is ample to walk the stern either way as needed.



Prop walking a vessel in the last few metres works better with both props rotating the same way, so that is a consideration. In practice the difference is only noticeable if you look for it - in general if the boat handles that badly that it is a significant issue then I would look for the problem but it would have to be stuffed up pretty bad for that.



What do you do with a three engine set up? No operator I have spoken to even considers this an issue in day to day use.

Answer 4

Counter-rotating propellers, are chanced on on twin-engine, propeller-pushed plane and characteristic propellers that spin in opposite guidelines. Counter-rotating propellers often spin clockwise on the left engine, and counter-clockwise on the properly suited. the earnings of counter-rotating propellers is to stability out the outcomes of torque and p-ingredient, removing the situation of the severe engine.Counter-rotating propellers should not be puzzled with Contra-rotating propellers.

Answer 5

When the props turn in the same direction, the boat tends to list and steer off course. Keeping an even keel and true course requires constant attention, especially in choppy water and high winds. Much of that problem can be solved by having two props turn in opposite directions. In other words, counter-rotation. The major advantage of counter-rotation is its ability to enhance performance by reducing steering effort in all RPM ranges.

Answer 6

It's not essential but makes sense. The side thrust of each propeller counteracts the other. So the vessel would not have a tendency to turn one way all the time. It also provides the captain an option of which propeller to use to get side thrust in docking and undocking.

Answer 7

Essential? No.



But to balance the boat and reduce torque on the hull counter rotating sure makes things easier.

Answer 8

Essential? no preferable yes...a Single screw ship doesn't have a counter effect...but 2 going in same direction might tilt ship and cause difficult steering...the ship will want to turn...counter rotation screws help in docking and maneuvering..

Answer 9

yes if they both rotate the same way it will just go round in circles

Answer 10

yes. to even the torque of the rotation.