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It sounds like matching the prop and cleaning up
the hub area is key to this outstanding performance with the "C" drive.
Let's see, I hope to arrive around noon on Friday. A day for carving a
right hand rotation prop out of a local tree, 3 hours to swap my "B"
for a "C" and on to Sun & Fun {:>)...... I like it, sounds
like you can eat and have your cake both .
Some day in the near future, tied the tail to a
tree and see what static rpm you get. I am particularly interested in the
take off and climb acceleration.
Ed
Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
----- Original Message -----
Sent: Monday, April 05, 2004 8:31
PM
Subject: [FlyRotary] Re: : Percent Power,
Throttle position, & RD-1C performance
Took closer note of throttle position on todays
flight. At 2000 ft the throttle was only about 1/3 open (position of
throttle quadrant, but it closely mirrors butterfly position) at economy
cruise setting which was 6.0 GPH. This is about 42% power, 82 HP
according to the EM2 which is fairly close but not perfectly calibrated
yet. The same power setting with the -B drive would bave been a bit
further open.
I did a quick check of MAP at 1000 ft at full
throttle and found I was not getting any drop at 150 MPH and had .5" boost at
220 MPH (ram air recovery I assume). I did not get around to checking it
in slow climb which would more accurately compare to what you would see on a
dyno.
Finally got some reasonably calm air to do
performance comparisons of -C drive vs -B drive. Without the prop blade
cuffs it looks like the break even point is at 203 MPH. Above
that -C burned more fuel than the -B. After installation of the
cuffs, the break even point was off the scale! i.e., above top speed with -B
drive. I had a good data point on the -B drive while burning 17 GPH
(209 mph during SUN 100 race). At the same speed, the C drive was
burning 15.8 gph. This was better than I had hoped for.
Tracy
Thanks,
Tracy. I was hoping
there would be someone out there flying with the same TB
diameters.
Like most things,
TB diameter is a tradeoff. My conclusion from the dyno data is that
44mm per rotor (1 ¾) is a bit small as the MAP is dropping off over 5000
RPM. But if you want to idle at 1500, and have a decent transition
from there to 3000; 1 ¾ is good. For a 2.85 to redrive, I’d want to
increase that flow area by 30% or so – to about 2” dia for each rotor.
My data may not
be representative because of restricted flow to the TB. The ‘airbox’
size is restricted by the cowl, and may have restricted the flow a bit.
In hindsight, it would have been smart (and easy) to make a run with
the airbox off and see what difference it made.
Al
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