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Vic Peters
Joined: 30 Oct 2009
Posts: 54
Location: Millinocket, Maine
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 Posted: Wed Jul 28, 2010 5:39 am Post subject: Too many questions |
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Hi all
How does one calculate 75% power? % of max rpm or % of wot level flight?
Same for best angle of climb and best rate.
How far north do you have to fly to be rid of 90 degree humid weather?
Vic in Maine
912ul
xtra
[quote][b]
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_________________
Vic
912ul Xtra
Maine
Too old to cut the mustard but not the cheese. |
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donaho1(at)verizon.net
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| Posted: Wed Jul 28, 2010 6:39 am Post subject: Too many questions |
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Vic, I can`t answer your first two questions, as for the last
question. It was 82 degrees and very hazy when I landed last night at
8:15 in Pennsylvania. I was sweating bullets when I got finished
unfolding the FSII at 7:00. Flying into the sun the visibility was
terrible. So I know for sure, you need to go farther north then Pa.
for cool weather.  Lanny N598LF
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Dana
Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA
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| Posted: Wed Jul 28, 2010 8:33 am Post subject: Too many questions |
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At 09:34 AM 7/28/2010, Vic wrote:
| Quote: | Hi all
How does one calculate 75% power? % of max rpm or % of wot level flight? |
Neither... it's the rpm corresponding to 75% power on the engine manufacturer's published HP curve.
| Quote: | | Same for best angle of climb and best rate. |
Through actual testing at various speeds.
-Dana
--
Clothes make the man. Naked people have little or no influence on society. [quote][b]
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russkinne(at)mac.com
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| Posted: Wed Jul 28, 2010 2:27 pm Post subject: Too many questions |
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VicDoesn't Rotax supply that info?
And try the north end of Baffin Island. It's great in July & August!
But few airfields
do not archive
On Jul 28, 2010, at 9:34 AM, Vic wrote:
| Quote: | Hi all
How does one calculate 75% power? % of max rpm or % of wot level flight?
Same for best angle of climb and best rate.
How far north do you have to fly to be rid of 90 degree humid weather?
Vic in Maine
912ul
xtra
| Quote: |
href="http://www.matronics.com/Navigator?Kolb-List">http://www.matronics.com/Navigator?Kolb-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/contribution
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Vic Peters
Joined: 30 Oct 2009
Posts: 54
Location: Millinocket, Maine
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| Posted: Wed Jul 28, 2010 3:09 pm Post subject: Too many questions |
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Vic Doesn't Rotax supply that info?
And try the north end of Baffin Island. It's great in July & August!
But few airfields
do not archive
On Jul 28, 2010, at 9:34 AM, Vic wrote:
| Quote: | Hi all
How does one calculate 75% power? % of max rpm or % of wot level flight?
Same for best angle of climb and best rate.
How far north do you have to fly to be rid of 90 degree humid weather?
Vic in Maine
912ul
xtra
| Quote: | | Yup I found it. 75% power is 5000 rpmBut how would rotax know anything about kolb performance? |
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[quote][b]
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_________________
Vic
912ul Xtra
Maine
Too old to cut the mustard but not the cheese. |
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rickofudall
Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA
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| Posted: Wed Jul 28, 2010 3:33 pm Post subject: Too many questions |
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Vic, Look in the operations manual pages 10-4 for the 912 UL and 10-8 for the 912 ULS 75% power for both is at 5000 RPM.
Rick Girard
On Wed, Jul 28, 2010 at 5:25 PM, russ kinne <russkinne(at)mac.com (russkinne(at)mac.com)> wrote:
[quote] VicDoesn't Rotax supply that info?
And try the north end of Baffin Island. It's great in July & August!
But few airfields
do not archive
On Jul 28, 2010, at 9:34 AM, Vic wrote:
| Quote: | Hi all
How does one calculate 75% power? % of max rpm or % of wot level flight?
Same for best angle of climb and best rate.
How far north do you have to fly to be rid of 90 degree humid weather?
Vic in Maine
912ul
xtra
|
[b]
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The smallest miracle right in front of you is enough to make you happy.... |
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ceengland(at)bellsouth.ne
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| Posted: Wed Jul 28, 2010 4:37 pm Post subject: Too many questions |
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| Quote: | On Wed, Jul 28, 2010 at 5:25 PM, russ kinne <russkinne(at)mac.com
<mailto:russkinne(at)mac.com>> wrote:
Vic
Doesn't Rotax supply that info?
And try the north end of Baffin Island. It's great in July & August!
But few airfields
do not archive
On Jul 28, 2010, at 9:34 AM, Vic wrote:
> Hi all
> How does one calculate 75% power? % of max rpm or % of wot level
> flight?
> Same for best angle of climb and best rate.
> How far north do you have to fly to be rid of 90 degree humid
> weather?
> Vic in Maine
Unfortunately, knowing only RPM isn't adequate to calculate horsepower.
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HP is Torque in foot lbs times RPM, divided by 5252.
A somewhat meandering explanation is at
http://horsepowersports.com/torque.php
or just Google & start reading.
To have any meaning, the RPM number in the Rotax manual should specify,
at minimum, manifold pressure, airframe, and propeller. Consider the
same engine/prop at 5000 RPM on something like a Kolb, then on a Van's
RV-12 (remember, same prop, too). 5k RPM on the Kolb might be 75%, but
would likely be closer to 50% power on the RV-12, because the cleaner
airframe would need a much lower torque figure to reach 5k RPM. Taken to
extremes, consider the engine with no prop at all at 5k RPM. The only
horsepower would be what's required to overcome internal engine friction
& 'pumping losses'.
Here's a relatively simple way to find 75% for a normally aspirated
engine: climb to roughly 7500feet density altitude, apply full throttle
with your prop pitched to turn the RPM at which the engine manufacturer
specifies *FULL* power. If you are turning the RPM for full throttle,
full power but you're at 7500 feet altitude, you're making pretty close
to 75% power. If you have a manifold pressure gauge, make a note of the
reading. If, at lower altitudes, you can set that manifold pressure &
turn the same RPM (the 'full power' RPM), you'll still be making around
75% power. This isn't exact, but it is in the ballpark. Rotax should
have a chart with RPM on one axis and manifold pressure on the other,
and a line that defines 75% power (effectively an infinite number of
combinations).
As to the temp/humidity issue, drive south & gain a lasting appreciation
for 90 degrees & 'humid'.  We used to laugh our heads off at Harry
Caray broadcasting daytime Cubs games & complaining about the 'brutal 83
degrees & 65 percent humidity.' A 95/95 or 95/100 temp/humidity day is
far too common (100+/95 isn't rare) down here 100-150 mi north of the Gulf.
Charlie
RV-7 under construction, but wishing for a Kolb here at Slobovia
Outernational
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