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Producing Acid Etch Items

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Port & Starboard. – Propeller Rotation.

Port & Starboard

When referring to the side of a vessel the terms PORT & STARBOARD are used but which is which.

Any reference to a position (such as left or right sides) on a ship is normally taken in relation to being in a position at the stern (back) looking towards the bow (front).

One way to remember PORT – is that the drink is Red & the word Port & Left both have 4 letters.

So STARBOARD must be Green (+ Green & Right have 5 letters).

Twin Propeller Rotation

The normal rotation is for the Port (left hand) propeller to turn anti clockwise & the Starboard

(right hand) propeller to turn clockwise, when viewed from astern looking forward.

This means that at the top of the turning circle the blades are moving away from

each other (going outwards).

Some vessels will have them turning in the opposite direction which gives better slow speed maneuvering but is less efficient.

On a scale model the rotation will work just as well in either direction as model propellers do not encounter the same problems with cavitation etc, as the full size versions.

The reason they turn in opposite directions is to counteract the sideways force the turning propeller creates (prop walk) with the rudder amidships (inline with hull) a clockwise turning prop will push the stern to the right (Starboard) & the counter clockwise prop to the left (Port) if they are both turning with the same force they cancel out any turning effect.

For the best maneuvering control on a model, having twin propellers each having their own motor & speed control & individual radio control of each motor gives very good steering &  the model can be steered round a course by just varying the propeller speed & rotation without using the rudder.

By one propeller going ahead (forward) & the other going astern (backward) the boat will spin.

A single propeller vessel can have the rotation in either direction, but clockwise is most common.