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02-04-2009, 08:29 PM
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Join Date: Apr 2005
Location: KSLC
Posts: 4,021
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Quote:
Originally Posted by Webb
You need to decide what your needs are.......ie: I recommend you close your eyes to cost and look at how you will use your plane. VFR pleasure flying would suggest FP since 95% of your time is spent in cruise. Gonna fly into heavy IFR, then a CS is a much better choice.
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Actually, cruise is where a C/S is excellent. The RV is like a car, where you're begging for just one more gear ratio to lower the rpm's and noise while cruising down the freeway. My motorcycle certainly has that problem! With a C/S, you have that option, and I use it all the time. The difference in sound, is VERY noticeable.
L.Adamson --- RV6A, Hartzell C/S
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02-04-2009, 08:45 PM
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Join Date: Jan 2005
Location: NC25
Posts: 3,507
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Quote:
Originally Posted by L.Adamson
Actually, cruise is where a C/S is excellent. The RV is like a car, where you're begging for just one more gear ratio to lower the rpm's and noise while cruising down the freeway. My motorcycle certainly has that problem! With a C/S, you have that option, and I use it all the time. The difference in sound, is VERY noticeable.
L.Adamson --- RV6A, Hartzell C/S
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Flying on trips in my RV-6 320 C/S turning 2300 RPM with an RV-6A 360 FP turning 2500, we burn the same fuel. What makes less noise, a 320 turning 2300 RPM or a 360 turning 2500 RPM?
__________________
Gary A. Sobek
NC25 RV-6 Flying
3,400+ hours
Where is N157GS
Building RV-8 S/N: 80012
To most people, the sky is the limit.
To those who love aviation, the sky is home.
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02-04-2009, 09:05 PM
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fugio ergo sum
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Join Date: Apr 2006
Location: Carlsbad, NM
Posts: 1,912
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Quote:
Originally Posted by RV6_flyer
...What makes less noise, a 320 turning 2300 RPM or a 360 turning 2500 RPM?
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Good question Gary. Does anyone know? I would like to see an RPM versus SPL graph. It might be surprising! I don't reject the notion that RPM and noise have a relationship, but I don't know what it is.
__________________
Larry Pardue
Carlsbad, NM
RV-6 N441LP Flying
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02-04-2009, 09:32 PM
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Join Date: May 2005
Location: Mandeville, Louisiana
Posts: 179
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Nosie freq might be a factor as well
Quote:
Originally Posted by n5lp
Good question Gary. Does anyone know? I would like to see an RPM versus SPL graph. It might be surprising! I don't reject the notion that RPM and noise have a relationship, but I don't know what it is.
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I've always thought that lower RPM equated to more comfort, but I had an interesting experience this past weekend. I was flying formation with a slower aircraft and had my plane pulled back to 2200RPM. The low frequency energy was noticable and seemed to go through me. I broke off and increased RPM to 2500. The noise was much more tolerable and comfortable. I don't think there was less noise, but is was definitly higher in freq and less noticable. I was more comfortable as a result. Your mileage may vary, as I think my plane is on the loud side as far as RV's go.
__________________
Dale Lambert
RV-6 Flying, XPIO360 Catto 3bld AFS3500EE
'68' C177
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02-04-2009, 10:07 PM
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Join Date: May 2005
Location: Mandeville, Louisiana
Posts: 179
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Airspeed is the limiting factor for acro
Quote:
Originally Posted by n5lp
The main difference is that with a fixed pitch prop, on the downside of a loop, it may be necessary to retard the throttle to prevent the engine from exceeding RPM redline.
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For my Catto, controlling airspeed would be the reason I need to control the power. RPM overspeed is not the issue when flying acro. Generally I enter a loop at 150kts and don't need to touch the throttle during the maneuver. Care needs to be taken not to overspeed the airframe during acro in a FP or CS RV. FP is fine for acro in an RV. Don't make that the reason to spend money.
Light weight might be more of a factor for enjoyable acro. In that case, consider a carbon fiber prop rather than aluminum.
No doubt, CS is better than FP for cruise fuel economy and better short feild performance, though an FP RV is still a good short feild airplane.
CS definitly slows down when you pull the throttle, but I don't view this as an issue at all. Anyone with moderate piloting skills can fly an FP and get into short strips just fine. If slowing down is a major factor, get a J3!
CS is more stable for IFR, but not a big deal if you have an autopilot.
If at all possible, you should make arrangements to fly both and then choose for yourself. Otherwise you will go nuts making this decision.
__________________
Dale Lambert
RV-6 Flying, XPIO360 Catto 3bld AFS3500EE
'68' C177
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02-04-2009, 10:11 PM
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Join Date: Mar 2008
Location: San Diego
Posts: 457
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Can happen
Quote:
Originally Posted by whifof100ll
I was flying formation with a slower aircraft and had my plane pulled back to 2200RPM. The low frequency energy was noticable and seemed to go through me. I broke off and increased RPM to 2500. The noise was much more tolerable and comfortable.
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In our installation, our Hartzell prop has an "Avoid continuous operation between 2000-2250 RPM" restriction. In that range, vibration actually can be unpleasant. So, like the SB says to, I avoid it!
--Paul
RV-6 O-360-A1A HC-C2YK-1BF
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02-04-2009, 10:14 PM
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Join Date: May 2005
Location: Mandeville, Louisiana
Posts: 179
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Catto
Quote:
Originally Posted by Garage Guy
In our installation, our Hartzell prop has an "Avoid continuous operation between 2000-2250 RPM" restriction. In that range, vibration actually can be unpleasant. So, like the SB says to, I avoid it! What engine/prop do you have?
--Paul
RV-6 O-360-A1A HC-C2YK-1BF
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Catto 3 blade. There was no vibration that could be felt by touching the panel. It was bothersome to my ears but with no perceptible vibration.
__________________
Dale Lambert
RV-6 Flying, XPIO360 Catto 3bld AFS3500EE
'68' C177
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02-04-2009, 10:28 PM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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Quote:
Originally Posted by whifof100ll
...CS is more stable for IFR, but not a big deal if you have an autopilot...
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Maybe this should be on a different thread but I have to ask, why does a CS prop make IFR flight more stable?
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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02-05-2009, 05:00 AM
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Join Date: Jan 2005
Location: Lake St. Louis, MO.
Posts: 2,346
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Quote:
Originally Posted by whifof100ll
CS definitly slows down when you pull the throttle, but I don't view this as an issue at all. Anyone with moderate piloting skills can fly an FP and get into short strips just fine. If slowing down is a major factor, get a J3!
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Couldn't have said it better myself. All it takes to slow down a FP is a longer lead time compared to a CS and even then there should be plenty of time. If incapable of thinking 30 seconds ahead of the airplane...get a Cub.
There is one item of note I have not seen discussed that may be at least mildly interesting to some builders. My FP Sensenich has the 2600 RPM limitation and is fitted to the 160 HP 0-320-DIA. The data plate affixed to the Lycoming engine notes the following: At 2600 RPM the engine develops 155 hp.
__________________
Rick Galati
RV6A N307R"Darla!"
RV-8 N308R "LuLu"
EAA Technical Counselor
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02-05-2009, 06:17 AM
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Join Date: Apr 2005
Location: KSLC
Posts: 4,021
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Quote:
Originally Posted by whifof100ll
No doubt, CS is better than FP for cruise fuel economy and better short feild performance, though an FP RV is still a good short feild airplane.
CS definitly slows down when you pull the throttle, but I don't view this as an issue at all. Anyone with moderate piloting skills can fly an FP and get into short strips just fine. If slowing down is a major factor, get a J3!
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I'm sensing a pattern in this thread. Those that don't have C/S seem to make excuses as to why a C/S isn't all that great. I see that now were down to pilot skills, and no issues, and marketing as an "excuse". That's really rubbish!
To the newcomer,and uninitiated, this might be believable. To all my C/S friends that I brought this subject up to yesterday.................it's laughable! Fact is, we've all flown F/P for many years, and now we all fly C/S. The differences are overwhelming.............in what can be accomplished! I'd never go back to a fixed pitch prop period...............unless I indeed had a Cub or Cub variant.
L.Adamson ---- RV6A
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