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[billyboy]

Hi new to all this can you help I have an MTB with twin 9v electric motors. viewed from the stern should the props turn clockwise or anticlockwise ? Should the left hand prop be lefthand  and the righthand prop be righthand or both be left or right ?


Confused need to order props for boat !

[Liverbudgie2]

You will require one of each. In virtually all cases the propeller turned outboard, that is the top of the blade turns away from the centre line.

LB

[malcolmfrary]

With counter rotating props, it is even more important than usual to make sure that the lock nuts are really locked to the prop, since one of them will be permanently trying to unwind itself.

[Jonty]

  Malcolm and LB are of course right, but there was a difference between ship and MTB practice. Packard engines were not handed, and the screws (three in most cases, four in Fairmile Ds] all turned the same way. In Vospers the centre engine drove direct, and the two wing engines, set further back in the boat, drove forwards through V-drives, effectively reversing their rotation.

  Similarly, aircraft engines were rarely handed. Lancasters, for instance, would probably have been easier to handle with handed engines. The only exception I can think of offhand was the Lockheed Lightning which had handed Allisons.

[Jerry C]

I wouldn't compare ships or boats with aircraft practice. Aircraft don't often reverse thrust in the air and the turning couple is large compared to ships. If you want to turn a ship short round with two screws then they need to be outward turning when going ahead.
Jerry.

[Jonty]

  Ships, yes, but not MTBs. Presumably MTBs, like Lancasters, turned better one way than the other.

[raflaunches]

Regarding direction of rotation of props on a MTB from what I've read and seen, they all go in one direction on the real vessels but on models they are handed to make them handle better and prevent torque influencing the direction of the model. Not to say that you can't put props that turn the same way on a model- I've done it on a few of my fast boats just remember to adjust your rudder to compensate.


On aircraft like Lancasters, Merlins turned in one direction unless they were suitably modified to fit the de Havilland Hornet long range fighter. The only difference was an extra set of gearing on the front of the engine to turn the output the opposite direction. Griffon engines turned opposite to Merlins but they are a bigger more powerful engine so they didnt mix and match Merlins and Griffons.