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  #31  
Old 02-04-2009, 08:29 PM
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L.Adamson L.Adamson is offline
 
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Originally Posted by Webb View Post
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.
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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  #32  
Old 02-04-2009, 08:45 PM
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Quote:
Originally Posted by L.Adamson View Post
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
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?
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  #33  
Old 02-04-2009, 09:05 PM
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Quote:
Originally Posted by RV6_flyer View Post
...What makes less noise, a 320 turning 2300 RPM or a 360 turning 2500 RPM?
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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  #34  
Old 02-04-2009, 09:32 PM
whifof100ll whifof100ll is offline
 
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Default Nosie freq might be a factor as well

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Originally Posted by n5lp View Post
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.
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.
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  #35  
Old 02-04-2009, 10:07 PM
whifof100ll whifof100ll is offline
 
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Default Airspeed is the limiting factor for acro

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Originally Posted by n5lp View Post
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.
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.
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  #36  
Old 02-04-2009, 10:11 PM
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Garage Guy Garage Guy is offline
 
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Originally Posted by whifof100ll View Post
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.
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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  #37  
Old 02-04-2009, 10:14 PM
whifof100ll whifof100ll is offline
 
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Default Catto

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Originally Posted by Garage Guy View Post
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
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.
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  #38  
Old 02-04-2009, 10:28 PM
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N941WR N941WR is offline
 
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Quote:
Originally Posted by whifof100ll View Post
...CS is more stable for IFR, but not a big deal if you have an autopilot...
Maybe this should be on a different thread but I have to ask, why does a CS prop make IFR flight more stable?
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  #39  
Old 02-05-2009, 05:00 AM
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Rick6a Rick6a is offline
 
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Quote:
Originally Posted by whifof100ll View Post
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!
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.
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  #40  
Old 02-05-2009, 06:17 AM
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L.Adamson L.Adamson is offline
 
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Quote:
Originally Posted by whifof100ll View Post
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!
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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