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To: lml@lancaironline.net
Date: Sun, 04 May 2008 23:06:17 -0400
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From: "Paul Lipps" <elippse@sbcglobal.net>
Subject: O-320 TAS
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Gary: I haven't flown Oscar's plane for a while, but as I remember, it =
started off somewhere around 2300-2400, dropped about 75-125 rpm during =
the takeoff roll, then was back up to 2400 during a climb at 110 mph =
IAS.  The replacement, highly modified Great American prop on my =
Lancair, to replace my beautiful three-blade ELIPPSE prop which I =
destroyed in a gear-up landing at Santa Paula, before an open-house =
crowd, displays the same high-low-high rpm thingy! My three-blade =
didin't; it started at 2230 rpm and just continued to increase rpm =
during the takeoff roll, reaching 2400 at lift-off at about 70-75 mph =
IAS, then continuing at 2410 while climbing at 110 mph IAS. With my =
125HP O-235, it gave me an ROC of about 1450-1550 fpm at 1000 dalt at =
1350 lb. Oscar and I did a lot of calibration flights on his plane and =
on different props we tried on it. Initially his GA prop gave 214-215 =
mph TAS at 2600 rpm. I did a slight mod to the prop tips, which boosted =
speed to 219 mph at 2750-2760 rpm. The rpm increase was due to the =
greater efficiency of the prop converting HP to thrust which gave more =
speed. That 2.1% increase in rpm was hardly sufficient in increasing the =
engine horsepower the 5% necessary for that speed increase. My GA and =
another of Oscar's props was modified by increasing root chord and pitch =
and reducing tip chord, and we were able to get more speed on less rpm, =
generally increasing efficiency 5%-10%. The reason many fixed-pitch =
props have that high-low-high rpm characteristic is that different parts =
of the prop come out of stall at different loads/rpm, whereas my design =
shows the same CL and lift all along the blade vs speed. It typically =
doesn't have the static and low speed thrust of the typical FP prop, but =
once it gets up to about 40-50 mph IAS, it really comes into its own. =
Tom Aberle describes the effect as having the same effect as cutting in =
an AB at about 70 mph on his winning biplane.
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<DIV><FONT face=3DArial>Gary: I haven't flown Oscar's plane for a while, =
but as I=20
remember, it started off somewhere around 2300-2400, dropped about =
75-125 rpm=20
during the takeoff roll, then was back up to 2400 during a climb at 110 =
mph=20
IAS.&nbsp; The replacement, highly modified Great American&nbsp;prop on =
my=20
Lancair, to replace my beautiful three-blade ELIPPSE prop which I =
destroyed in a=20
gear-up landing at Santa Paula, before an open-house crowd, displays the =
same=20
high-low-high rpm thingy! My three-blade didin't; it started at 2230 rpm =
and=20
just continued to increase rpm during the takeoff roll, reaching 2400 at =

lift-off at about 70-75 mph IAS, then continuing at 2410 while climbing =
at 110=20
mph IAS.&nbsp;With my 125HP O-235, it gave me an ROC of about 1450-1550 =
fpm at=20
1000 dalt at 1350 lb. Oscar and I did a lot of calibration flights on =
his plane=20
and on different props we tried on it. Initially his GA prop gave =
214-215 mph=20
TAS at 2600 rpm. I did a slight mod to the prop tips, which boosted =
speed to 219=20
mph at 2750-2760 rpm. The rpm increase was due to the greater efficiency =
of the=20
prop converting HP to thrust which gave more speed. That 2.1% increase =
in rpm=20
was hardly sufficient in increasing the engine horsepower the 5% =
necessary for=20
that speed increase. My GA and another of Oscar's props was modified by=20
increasing root chord and pitch and reducing tip chord, and we were able =
to get=20
more speed on less rpm, generally increasing efficiency 5%-10%. The =
reason many=20
fixed-pitch props have that high-low-high rpm characteristic is that =
different=20
parts of the prop come out of stall at different loads/rpm, whereas my =
design=20
shows the same CL and lift all along the blade vs speed. It typically =
doesn't=20
have the static and low speed thrust of the typical FP prop, but once it =
gets up=20
to about 40-50 mph IAS, it really comes into its own. Tom Aberle =
describes the=20
effect as having the same effect as cutting in&nbsp;an AB at about 70 =
mph on his=20
winning biplane.</FONT></DIV></BODY></HTML>

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