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Author Topic: Propeller Rotation & Configuration  (Read 8367 times)

dodes

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Re: Propeller Rotation & Configuration
« Reply #25 on: June 03, 2015, 08:44:37 PM »

To answer why the RN warships with CPP propellers and gas turbine engines are inward turning, the principle is easy to explain. When a screw turns its wash spins off at a slight angle to a ships direction of travel, so having inward turning props, in theory concentrates the prop wash into a stronger thrust giving better fuel economy and better speed. All twin shaft fixed screw vessels in the RN are outward turning, traditionally for ship handling purposes and because they always were that way. At Nautical college many years ago, we were taught that ferries with twin CPP props were outward turning for ship handling purposes. But I agree with Shipmate 60, model boats seem to have some different rule and with twin screw boats with one speed controller in models of older boats inward turning screws seem to work best because the wash is forced over the central rudder. The paddle wheel effect as it is called for the side effect on a vessels direction is mainly felt when the vessel is stopped or moving very slowly, except when moving ahead. But as shipmate says with screws turning at 5000 revs in very shallow water and all the turbulence of air sucked into the wash etc. We can argue and discuss this subject till the cows come home to grass. Myself I have driven single, twin screw, single and twin rudder, screw on one side, single and multiplies of voith schineder  and aqua master screw boats and at times the rules where not followed by these vessels for different reasons. All I say is build your boats lads as you want and enjoy them, I most certainly love to see other peoples works of creations and only marvel that I cannot build as good as them.
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MTB Hulls

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Re: Propeller Rotation & Configuration
« Reply #26 on: June 04, 2015, 08:32:47 AM »


found this on the web;
"The Lord Nelson Class were the last British battleships to have inward-turning screws, which allowed greater propulsive force and slightly higher speeds and slightly less fuel consumption, but were unpopular in service because they made ships less maneuverable at low speeds or when going astern."
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Regards,
Christian.
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