Propeller
Measurement Within the United States there are no standards to which
propellers must be built or repaired. For this reason BLACK DOG PROPELLERS has adopted the International Standard
Organization’s ISO 484/2-1981 standard for measuring pitch,
and camber; the tolerances at the extreme radius; the angular
deviation between two consecutive blades, the surface finish and
static balance. Two of the above parameters have the greatest effect
on the overall performance and efficiency of the propeller. They are
camber and pitch.
Continuous
Camber Assessments:affect propeller RPM, propeller power, cavitation, and most of all
the pressure fluctuations on the hull. We calculate pitch for every
degree of rotation over as many as 10 radii on each blade. This
allows us to actually profile and visualize the surface variations on
the blade of a propeller. Camber is the undulations (high and low
areas) over the surface of the propeller blades. These
camber variations are the direct contributors to propeller induced
vibrations. By profiling the surface of the blade we are
able to not only identify and eliminate these areas that are inducing
vibration but also define and locate those areas on the blades that
are out of tolerance and effect modifications efficiently with less
induced metal fatigue.
Accurate
Pitch Measurements:BLACK DOG PROPS measures propeller pitch to.001" According
to ISO specifications 20 points are defined on each blade of a
propeller. Pitch is measured and compared between blades
over 16 local areas and a minimum of 4 radii on each blade for ISO
Class S propeller. The mean pitch of each blade is then
compared to the other blades. The pitch of a propeller as a whole is
then compared to the target pitch. For ISO Class 1 propeller the Mean
Measured Pitch must be within 0.75% of the target pitch.
Documented
and Numbered:Every propeller we receive is given a serial number. The first
measurement of that propeller is saved in the computer and the
finished measurement is saved. This gives us a history of your
propeller. Given accurate performance data we can improve
your propeller's performance each time it is
remanufactured. With each propeller we remanufacture you
will receive an ISO Class Report documenting the pitch and class of
the propeller. This report is recognized throughout the world as
proof of the Accuracy of the propeller.
Eliminate
Propeller Induced Vibration:The major cause of vibration in boats is propeller induced. 80% of
this vibration is the result of pitch and camber inconsistencies.
Variations in the pitch and camber of propellers waste horsepower and
cause turbulence which is perceived as vibration. This can also
contribute to cavitation and premature blade failure.
INCREASED
EFFICIENCY AND FUEL ECONOMYA pair of propellers that are pitched accurately will work more efficiently with less wasted horsepower. Having a propeller with all the blades pitched the same allows those blades to work together. Having a pair of propellers pitched within +/-.01" dramatically increases the efficiency of those propellers allowing the engines to work in concert. RPM differences or consistently poor performance from one engine can indicate significant pitch differences between propellers. Increasing propeller efficiency will result in decreased fuel consumption.
Calculated
AdjustmentsPitch changes to meet RPM goals are computer calculated to .001" of
pitch. We can also estimate the most efficient diameter and pitch for
a given vessel predicting expected top speed. Propeller efficiency
can also be calculated as well as diameter/ pitch adjustments for
various numbers of blades.
CUSTOM
REMANUFACTURINGGiven the manufacturer's or the designer's specifications and
offsets BLACK DOG PROPELLERS is able to bring a propeller to design
parameters within ISO 484/2 Class Tolerances. This work is documented
and guaranteed to meet the designated ISO Class Tolerances.
