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murphy-rebel@dcsol.com at 18:58:34 on 17 Nov 1999.
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To add to Bob's "same pitch - very difficult"
When setting the pitch on your propellors, don't even attempt to do it on
the aircraft. You will never get the blades the same. Remove prop and find a
nice level spot on the floor or bench(may have to set prop hub on something
so blades will clear the bench) and with a marker trace the hub and one
blades location on the bench (with the prop upside down so you have a flat
surface at the tip to set the protractor on). Place the protractors flattest
edge on the hub, parallel to the tip that is in the traced area, and set
your protractor bubble so the bubble just touches the edge of one of the
centering lines(this removes the guess work as to if you have the bubble in
the same location each time). Mark the protractor so you know which way is
up, left and right, so you don't get it turned around! Make note of the
degrees showing on the scale. Theoretically zero, but probably shows 1/2, 1
or 2 degrees and could be positive or negative to the direction you
need(this is why its important not to get the protractor turned around from
here on). Then if you need 11 degrees pitch add or subtract your starting
point and lock the protractor at the required location. Don't touch it again
or drop the protractor. Set one blade with the bubble hugging the same
centering line(protractor flush with end of tip), making sure the protractor
is oriented the same as when you set it, and then rotate the propellor one
blade to sit above your traced outline.Then set this blade the same as the
first and repeat for the 3rd (4th, 5th) blade. When you have set all the
blades and tightened the hub halves, recheck each blade (with it inside the
traced outline) to make sure nothing has moved. Setting each blade in the
traced outline removes any error caused by an unleveled work bench or floor.
Remember 1 degree will change static RPM, from 70 to 100 RPM's. Now you
have a starting point to work from with all the blades pitched exactly the
same! If this pitch doesn't give what you want, to re-pitch, remove prop and
set back into your traced outline. Verify or reset your protractor at the
tip of the prop so the bubble once again hugs a centering line. Make note of
the degree setting and then add or subtract the number of degrees that you
need to increase or decrease RPM'S. Then set all the blades as before so the
bubble hugs the centering line. As a side note, I had my 3 blade X 70" dia.
warp drive set at 8 1/2 degrees on my 100HP O-235-C and had marked each
blade at the hub split with a fine point marker for preflight purposes to
see if a blade had slipped. When I repitched it to 11 1/2 degrees for my 150
HP O-320 I could not distinguish that the marks had moved, so precision is
very important when you cannot physically see 3 Degrees at the root of the
blade. And for you 150HP Lycoming runners out there, at 11 1/2 degrees I see
approximately 2400RPM on climb out and in level full power cruise I can only
spool it up to 2675RPM and this is a 70" diameter,tapered tip prop. At the
12 1/2 degrees I started at, I could only get 2575 RPM at full power.( and
yes my tach has been checked with an optical tachometer.) Don't know how you
can spool them up at 13 degrees (and most of you seem to have longer 72"
props), but maybe you are just trusting the accuracy of the protractor and
locking it in a 13 degrees and then setting the blades to the protractor and
not adjusting for zero error (or you have 160HP plus). Doesn't really matter
as the only important thing is that all the blades are pitched exactly the
same(and prop off the plane is the only way!) and you are getting the RPM's
you want!
Just My 2 Cents, Wayne
-----Original Message-----
From: Bob Patterson <
bob.patterson@canrem.com>
To: Murphy Rebel Builders List <
murphy-rebel@dcsol.com>
Date: Wednesday, November 17, 1999 1:50 PM
Subject: Re: Prop pitch
Many Rebels are using Warp Drive props, but you are the only one I know
who has it on a 912. On the O-320's, pitch is generally in the 13 degree
range - plus or minus up to 1 degree....
We use a GSC wood prop on our 912, but I have no idea of the pitch, as
I use a home-made gadget to set it. Most important consideration is having
all blades at SAME pitch - very difficult !!
.....bobp
---------------------------orig.-----------------------------------------
At 07:52 PM 11/15/99 -0500, you wrote:
One last item this evening. I use a 3 blade WD primarely in the summer on
floats. If anyone is using this prop. what type of pitch settings are you
using and do you vary that setting for different flying. I'm using the
protractor supplied by WD with the level and round wheel with degrees
marked
around the edge.
Thanks, Aurele
Rebel 063
<!DOCTYPE HTML PUBLIC "-//W3C//DTD W3 HTML//EN">
<HTML>
<HEAD>
<META content=text/html;charset=iso-8859-1 http-equiv=Content-Type>
<META content='"MSHTML 4.72.2106.6"' name=GENERATOR>
</HEAD>
<BODY bgColor=#ffffff>
<DIV><FONT color=#000000 size=2>One last item this evening. I use a 3
blade WD
primarely in the summer on floats. If anyone is using this prop. what type
of
pitch settings are you using and do you vary that setting for different
flying.
I'm using the protractor supplied by WD with the level and round wheel
with
degrees marked around the edge.</FONT></DIV>
<DIV><FONT color=#000000 size=2></FONT> </DIV>
<DIV><FONT color=#000000 size=2>Thanks, Aurele</FONT></DIV>
<DIV><FONT color=#000000 size=2>Rebel 063</FONT></DIV></BODY></HTML>
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