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B
y, Joe Zingali
Pres.
of J &Z Products Inc.
It
may be a little confusing, but I am going to try to explain the functions
of our dual pitch propellers. First, of all, we will take
a specific size propeller so that I can explain the pitch
by the numbers. The size
propeller I am going to start with is 18-6-10 propeller. The 18 is the diameter and the 6-10 is the progressive
pitch that you have been
hearing about. The 6 pitch is the lowest pitch, and it is closest
to the hub of the propeller. The
10 is the highest pitch and that
Is at the FARTHEST POINT
FROM THE HUB (at
the tip of the Propeller). Now that we know where high and
the low pitches are I will try to explain the reason for the
duel pitch and the benefit you can get out of them.
First of all the pitch closest to the hub (6 pitch) progressively
increases higher as it moves toward the tip of the propeller,(10 pitch
) therefore making the center of the propeller approximately
8 pitch ( 4.500 in. from the tip). When this propeller (18-6-10)
is operating at level flight the propeller is operating normal
or has its, least load in respect to taking off, climbing, turning, and
making attitude changes and etc.
Because of this, the propeller is flying at its greatest EFFICIENCY,
because it is not Carrying the load like it would if it was climbing etc.
And the propeller is at its greatest angle of attack (highest pitch-10)
therefore moving forward 10 in. per REVOLUTION (allow 15% for Slippage).
At the instance there is an altitude change in a climbing configuration
the propeller is giving in to the extra load causing it to flatten out
at the highest pitch of the propeller (the tip). With this happening the
propeller is literally twisting to the next pitch that will support the
load that is developing with the plane climbing, in this case would be
the next favorable pitch (like shifting down to a lower gear in your car
when you start to climb a hill. Remember the weight of your plane and
the size of your motor (horse power) have a lot to do with how much the
Propeller will change pitch. In figuring the size propeller to use, just
take the size you are using and match it to the center pitch of the duel
pitch propeller. EXAMPLE
lf you are using an 18-8 you would use a 18-6-10. I hope I have cleared
up some of the questions about ZINGERS DUAL
PITCH PROPELLERS.
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