Marine Propeller
It is a
device with a hub that rotates. It has blades
connected to the hub set a pitch to form a helical
spiral when rotated similar to Archimedes' screw.
Propeller is transforming rotational power of the
hub into thrust.
Parts of
propeller
Hub
It is the center of
the propeller. It connects blades to the
propeller shaft. The smaller diameter of the
hub is, the more thrust will the propeller
generate, but also the hub will be weaker.
Twisted
fins connected to the hub. Shape of the blades
and speed at which they are rotating dictates
the performance propeller can deliver.
Blade
Face and Back
Face of the blade is the high pressure
side - side that faces aft of the boat and
pushes the water when the ship moves
forward. Back of the blade is the low
pressure area - side that faces towards
the front of the boat.
Diameter
Diameter is very important
parameter, it determines the amount of
power propeller can absorb and deliver
as propulsion. If the ship is not
reaching speeds over 35 knots,
diameter is also proportional to the
efficiency of propeller. Increase in
diameter increases thrust but also
torque load on the engine shaft.
Leading
and Trailing Edge
Leading edge of propeller points
in the direction of the flow of
water. When looking at the
propeller from the back of the
boat, it is furthest away.
Trailing edge is the one closer to
the stern of the boat. They are
separated by the blade tip.
Propeller
Materials
Conventional
propeller materials are steel
or Nickel-Aluminium-Bronze.
Nowadays researchers focus on
different materials like fiber
glass composite or carbon
fiber composite. Fiber glass
composites proved to be more
economical and their
performance is the same or
better compared to metal
propellers. Carbon fiber
composite propellers have more
advantages than fiber glass
propellers with no
compromises. Researchers are
also working on hybrid
composite materials.
Carbon fiber
propeller
Hybrid
composite
Bronze propeller
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