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Thanks for that feedback Tracy. I think its going
to be quite a while before I do any speed runs anywhere near sea
level.
Hopefully my cowl configuration is not
significantly worse than a stock RV cowl drag-wise. Otherwise my RV-4 should be
as clean as any other. I'll know a lot more when I have the opportunity to test
more. It did seem like speed and RPMs were still creeping up during the one
brief full throttle run that I did. At this point it seems the airplane matches
or slightly exceeds the performance of my old RV-6A (160HP Lyc). I have my
doubts that it will approach the performance Dave Leonard reported in the
Sharpie race.
I think the comfort issue for me is a combination
of muffler and just perception. My setup generates considerably more noise at
full throttle than it does at 5,000 - 5,100 but vibration levels dont seem to
change appreciably. I think I really just need to address the muffler issue and
get more comfortable with the airplane.
Mike Wills
RV-4 N144MW
----- Original Message -----
Sent: Wednesday, March 11, 2009 7:41
PM
Subject: [FlyRotary] Re: IVO Prop
Mike,
As a general rule of thumb, there will be about 1000
rpm difference between static and top speed RPM at sea level for RV speeds
(fixed pitch prop). The last 10 - 20 mph can take a surprisingly long
time. How clean the airframe is can affect the top speed and RPM quite a
bit. At higher altitudes, max rpm falls off a bit due to falling
HP.
Perception of engine "comfort" depends a lot on muffler, engine
mount and prop balance. The most 'serene' flight I ever had was the 2003
Sun 100 race with the engine humming at 6300 rpm. Everything felt just
right. The 2004 race at 7250 rpm was almost as good. The rpm
difference was due to the different drive ratios.
Tracy
On Wed, Mar 11, 2009 at 10:13 PM, Mike Wills <rv-4mike@cox.net>
wrote:
Tracy,
My RV static RPM is 5350 - 5400 with
my Warnke prop which seems pretty good. This is with a 2.17 ratio
RD-1. When the prop unloads in level flight what should I expect to see
for RPM at full power? Max RPM I've seen in level flight, full throttle,
8,000' was about 5700 - 5800 but I may not have given things enough time to
settle out. What are people typically setting for cruise RPMs/MP? With
the limited flight testing I've done so far my engine feels pretty
comfortable at around 5,000 RPM and that has been a typical power setting
for me to date. Still getting used to the different sounds and sight picture
with the high RPMs and cheekless cowl.
At higher power settings/RPM it feels
"busy" - hard to describe and it may just be a comfort factor thing that I
need to get used to.
Mike Wills
RV-4 N144MW
-----
Original Message -----
Sent:
Wednesday, March 11, 2009 8:48 AM
Subject:
[FlyRotary] Re: IVO Prop
Yep, should have thought about pushers when I wrote that
comment. The IVO seems to work well on pushers since the stalled
inner part of the blades is in turbulent air and doesn't cost them the
drag that it does on tractors. Tractors are pretty much stuck with
high priced variable pitch stuff like MT to equal the performance of a
well matched fixed pitch prop.
What is well matched?
If you are running an RD-1B the static rpm should be 5100 -
5500. With the RD-1C it should be 5900 - 6300
rpm. If you get less than that, it isn't a well matched
prop. This also assumes that the engine is performing up to par of
course. The exact number depends on what you want to optomize, climb
performance or cruise economy.
One more caveat: If you are
putting it on a plane with a cruise speed below ~ 150 MPH, the IVO also
works on tractors as well. On my RV-4 the IVO cut top speed about 15
mph. and around 10 mph from cruise compared to a well matched fixed pitch
prop.
Tracy
On Wed, Mar 11, 2009 at 12:41 AM, John Slade <sladerj@sbcglobal.net> wrote:
>I
didn't know anyone had ever had any success with an IVO. Tell me
more.
What do you want to know? Its a very well engineered piece of
equipment. The CF blades are hollow and have a steel rod running to the
hub. Activating the motor via brushes twists the steel and thus twists
the blades equally. The twist change is quite visible. There were
problems with the individual blades slipping on the hub. This has been
solved by providing a knurled hub, and not selling to guys with
Lycomings. The IVO is available for rotary, subaru, Franklin 6 and other
less "pulsy" engines. After the first 15 hours or so my blades have
hardly taken any extra torque.
My performance is greatly enhanced
compared to the fixed pitch Performance prop. Static with the wood prop
was around 4500. With the IVO on full fine I get closer to 5400 which
gives me access to a lot more power on take off. I've never done a "high
speed" run with the IVO, but I've had 180 kts indicated at 2000' a few
times without much effort, and without ever going to the full course
setting. Another nice bonus is that throttled back on full fine for
landing, the prop acts like a brake. Its much easier to land and stop
than the fixed pitch that's pushing you along fairly well, even at
idle.
I know a Velocity driver (Mike Watson) who also uses an IVO
(Franklin 6) and is very happy with it after around 5 years of
use.
The factory people are very easy to deal with and very
helpful.
The Cozy Girrrls are installing an IVO. What better
recommendation could you want? :)
Regards,
John Slade
Turbo
Rotary Cozy IV, N96PM
98.1 Hrs.
Mike Wills wrote:
Mike
Wills
RV-4 N144MW
----- Original Message ----- From: "John
Slade" <sladerj@sbcglobal.net>
To: "Rotary motors in
aircraft" <flyrotary@lancaironline.net>
Sent: Tuesday,
March 10, 2009 10:30 AM
Subject: [FlyRotary] Re: Ground
Testing
The
IVO electric in-flight adjustable costs around $2350. I'm very
pleased with mine. My "spare" is a $2700 fixed pitch wood prop thats
a piece of art, but doesn't work anywhere near as
well.
John
Tracy Crook wrote:
A variable pitch prop
would be nice to get the best of both worlds but it's an expensive
option and $10,000 buys a lot of gas.
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