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Hank,

I have the first version of the IVO Magnum (3 blade) which
is suppose to have an adjustable pitch from 30" to 90", on
my L-235.  First let me say the prop is quite well made and
the factory support has been pretty good.  I runs very
smooth as well and looks pretty good.  Unfortunately, it
doesn't work very well on high speed aircraft.

I found that take off and climb performance was great but
cruise was anemic at best no matter what pitch setting I
selected.  T-O and climb was better as the pitch was reduced
but that wasn't an issue at max pitch settings.  What was
really confusing was the engine was loaded (high MF
pressures) at high cruise power setting but the speed wasn't
there.  I found I pretty much clapped out at 190mph.  A good
friend of mine tried the prop on his long-eze with the same
results.

It took me a while to figure out what was wrong but with a
propeller protractor and the angle vs. pitch formula it
became pretty clear.  The inner portion of the blade does
not twist when pitch is added and it's normal pitch is too
shallow regardless of pitch setting.

Here are the numbers I measured.

At the maximum pitch setting;

Station Blade Pitch Speed @ Speed @
in inches Angle in inches 2700 2400
3"
6"
9" 30 32 83 74
12" 30.5 44 113 100
15" 36 68 175 155
18" 35 79 202 179
21" 29.5 74 190 169
24" 27.5 78 200 178
27" 25.7 81 208 185
30" 24.5 85 219 195


At 30" diameter and less the blades are working against
forward motion.  You might also notice that I was not able
to measure 90" of pitch anywhere along the blade.

Neil


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