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Prop Pitch Measurement
February Tech Notes
A Supplement to The Engine Analysis Software
and
The Prop Duplicator
I have been using the Hughey Propeller Measuring Gauge for 25
years and have never thought much about it. Withing the past 10 years I have been getting interested in the some of the finer points of model boat propeller design and modification. I decided that it was time to splurge and buy one of the Woods Pitch Gauge Measurement Devices. What a terrific tool and a precision piece. I can
analyze the pitch and the efficiency of propellers VERY WELL
with this gauge. I have developed a system and spreadsheet, which I will describe.
I made up a comprehensive spreadsheet in Excel to keep
the measurement and comparison records, and additionally to do some of the mathematical calculations. I will
describe how I measure a prop with this gauge and if you find
it informative and a necessary tool, GREAT! First, you can get
the Wood's Pitch Gauge by visiting http://woodrcboatproducts.com.
If you are interested in prop measurement and documentation, you
should download the FREE spreadsheet before you analyze this tech
article. Click Here to Download. There is also an image that shows where you should mmeasure on the Gauge to set the 70%.
Here We Go!
You will want to describe the prop, the date, and your estimated
engine RPM. Take calipers and measure the total diameter of the
prop and input this in decimal measurement in the column
"Measured Prop Diameter Inches". This will output the
conversion into Millimeters. The next column (Column X) is the MOST IMPORTANT
setup measurement outputted. This represents the distance you
will want to set with your calipers BETWEEN THE TWO POINTS SHOWN ON THE DRAWING IN THE ZIP PACKAGE OF THE
MEASURING GAUGE. This figure adjusts for the centerline of each
of the posts and calculates 70% outward from the center of the
propeller shaft hole. Why do I move out 70%? I believe that this is the area on the
propeller that does MOST of the work. ALL my measurements are
taken at this 70% point. You will want to use the first 3 steps of the pitch
gauge. The first step is the base point and you use that to set ZERO.
Once you ZERO the Gauge, you will want to move to the second step and input the degrees you read
into the .0625" column. This will output the pitch. Next do the same for the 3rd and 4th step and input these degrees into the .125" and .1875" columns. The
prop is placed on the shaft upside down and the sharp pointer
is positioned using the calipers BETWEEN the large shaft and the
small shaft as outputted in the .70 from hub Measurement. Then
adjust the prop so the small pointer just hits the Far Trailing
Edge of the prop (it almost drops off the back). Set the pointer
at 0 degrees. You will need to
input the MPH that the prop actually runs on your boat and the
amount of slippage is automatically outputted in the column Percent
Prop % Slippage. This is helpful to find the best and most efficient
prop for your application. There are a few props shown as information.
After you get used to the Woods Propeller Measuring
Gauge, I know it will become one of your most valuable tools!
Let me know if you have any interesting props which don't seem
to fit any mold, and we can try to figure out why it is better
than anything else. Until Next Month……….

ENGINE Analysis Software for the Serious RC Competitor
