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From: (no name) (no email)
Date: Mon Jan 03 2005 - 10:45:27 EST
In a message dated 1/1/05 12:01:53 AM,
writes:
<< I have no idea whether ships engines are constant speed or not. But in
answer to your question, you could vary the pitch of the propeller while the
RPM remains the same up to a point. Obviously the engine would slow if you no
longer could reduce power by reducing pitch. This is how it is done on small
aircraft. >>
A constant speed prop is not the same as a controllable pitch prop (CPP). In
most cases the constant speed prop is self adjusting in pitch to keep the
engine at a set RPM. The pitch of the CPP is under the control of the operator and
can be varied independently of engine RPM.
The closest thing to a constant speed prop in recreational boat use is the
Brunton Autoprop. This is a self adjusting propeller in which the pitch of the
blades varies under load. It is a marine version of the self adjusting constant
speed propellers used in light aircraft. The Autoprop consists of a prop with
blades free to swivel on their own axis in response to water pressure. In
this regard it is similar to the feathering prop long used by sailors to minimize
drag under sail. Through clever design, the blade mass is offset from the
blades swiveling axis. The shape of the blade is difficult to describe in words
but a brief glance at a picture of an Autoprop will make everything clear.
Larry Z
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