Revents in Screw Propellers for Steam and other Vessels.
Year: 1888

page_text: Revents in Screw Propellers for Steam and other Vessels.
I
I, FRANCIS WILLIAM WILLCOX of 3 The Oaks West Sunderland in the County of
Durbam Civil Engineer do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained in
and by the following statement :—
This invention has for its object Improvements in Screw Propellers for steam and
other vessels namely:-the diminution or elimination of vibration caused by the blades
of screw propellers revolving past the stern and rudder posts of vessel the reduction
of slip or difference between the linear advance of the vessel propelled and that of the
propeller due to its pitch to the amount required to generate the requisite propelling
force due to a given speed of ship and the formation of the blades in such a manner
that the whole of their surface shall be effective from root to tip thus doing away with
the churning action which takes place from the propeller boss for a considerable
distance towards the ends of the propeller blades.
In order to eliminate vibration I centre each section of the blades
curve (a) as shown on Fig. 1 the after edge of blade (b) being a straight line by
a Cissoid
upon
construction the blades pass the stern and rudder posts gradually and without
violence.
The development of the Cissiod curve is shown on Fig 5.
To reduce slip I incline the blade aft square to a line (c) drawn from the centre of
area (d) of the propeller blade and tangential to the water line (k) at the level
of the centre of the screw shafting (e) of the vessel to be propelled as shown on
Fig. 2.
I also curve the outer portion of the blade (f) forwards to such an extent as will
cause the water flowing backwards from the propeller to take a cylindrical form equal
to the diameter of the propeller thus doing away with the coning or spreading action
usually occurring in the wake of screw propellers. The result obtained from this
formation of blade is that it works in solid water and clear of the broken water
following the run of the vessel. The direction of the water is shown by arrows at (g)
Fig. 3.
It also has the effect of bringing the vessel astern in a straight line when the rudder
s amidships as the water flowing from the propeller when the engines are reversed is
arried clear of the vessel as shown by arrows at (h) Fig. 3.

page_text: In order to render the blades effective for their whole area I curve the leading
edges as shown on Fig. 4 from the boss outwards to the centre of area or to a point in
the blade at which the angle is not less than forty degrees with a line drawn square or
perpendicular to the line (e) of shafting or advance. By this means the water is
gradually brought into motion and the portion of the blade near the boss or centre
becomes effective for propulsion.
said
Having now particularly described and ascertained the nature of my
invention, and in what manner the same is to be performed, 1 declare that what
I claim is :-
(a) The forming the centre of the section of the blades of screw propellers upon a
Cissiod curve.
(b) The placing the blade at right angles to a line drawn from the centre of area of
the propeller blade tangential to the water line at centre of propeller shaft of vessel to
be propelled.
(c) The curving the lower and leading portions of the blades from the boss to their
centres of area or to such part of the blades at which the angles formed with a line
drawn perpendicular to the line of advance shall not exceed forty degrees.
Dated this 11th day of July 1888.