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08-06-2010, 09:03 PM
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Join Date: Jan 2007
Location: Battle Ground
Posts: 480
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FP vs CS
I have been going round and round on this issue. FP, no CS, no FP, no really CS. Thanks for making the decision easier... FP it is!
__________________
Scott
RV-7 N818BG (flying)
Bearhawk Patrol (building)
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08-06-2010, 09:16 PM
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Join Date: Apr 2005
Location: KSLC
Posts: 4,021
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Quote:
Originally Posted by sahrens
I have been going round and round on this issue. FP, no CS, no FP, no really CS. Thanks for making the decision easier... FP it is!
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In California with sea level altitudes..............you might do okay...
Up here in the Rockies of the western US..........it's just no contest between a fixed pitch & constant speed. The C/S can do everything the F/P can't....
The C/S was one of the first items I ordered, at the expense of a few other priorities I would have liked. I'd do the same, again.
L.Adamson --- RV6A
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08-06-2010, 09:24 PM
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Join Date: Oct 2008
Location: Schaumburg, IL
Posts: 2,053
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Quote:
Originally Posted by sahrens
I have been going round and round on this issue. FP, no CS, no FP, no really CS. Thanks for making the decision easier... FP it is!
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Would you consider the new Sensenich ground adjustable? I am giving it some thought?
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Tony Phillips
N524AP, RV 9 (tail wheel)
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08-07-2010, 07:05 AM
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Join Date: Feb 2005
Location: Chesterfield, Missouri
Posts: 4,514
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Quote:
Originally Posted by apkp777
Would you consider the new Sensenich ground adjustable? I am giving it some thought?
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One of my friends saw one at OSH and has gone ga-ga over it. Evidently, it is a thing of beauty inside and out, and very easy to adjust.
__________________
RV-12 Build Helper
RV-7A...Sold #70374
The RV-8...Sold #83261
I'm in, dues paid 2019 This place is worth it!
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08-07-2010, 07:15 AM
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Join Date: Oct 2008
Location: Schaumburg, IL
Posts: 2,053
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Quote:
Originally Posted by David-aviator
One of my friends saw one at OSH and has gone ga-ga over it. Evidently, it is a thing of beauty inside and out, and very easy to adjust.
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Yes, it looks really nice. However, do you think it's worth $3700. My Catto needs to be re-pitched and my options are sell the Catto, go with the GAP or re-pitch the Catto.
__________________
Tony Phillips
N524AP, RV 9 (tail wheel)
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08-07-2010, 10:12 AM
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Join Date: Feb 2007
Location: San Diego, CA
Posts: 1,670
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The obvious advantage of the Ground Adjustable prop is that you can have several different FP props at your disposal without having to remove and reinstall the prop.
Cruise prop setting for long X/C from long runways in winter. Come summer, and you need better climb performance for a shorter hop from a shorter runway, you merely adjust the pitch of the prop accordingly.
If you need that capability, the GA prop makes sense.
I think Whirlwind makes a Ground Adjustable prop, as well.
__________________
Pete Hunt, [San Diego] VAF #1069
RV-6, RV-6A, T-6G
ATP, CFII, A&P
2020 Donation+, Gladly Sent
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08-07-2010, 12:16 PM
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Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
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Quote:
Originally Posted by L.Adamson
In California with sea level altitudes..............you might do okay...
Up here in the Rockies of the western US..........it's just no contest between a fixed pitch & constant speed. The C/S can do everything the F/P can't....
The C/S was one of the first items I ordered, at the expense of a few other priorities I would have liked. I'd do the same, again.
L.Adamson --- RV6A
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The question builders need to each answer for them selves is...do they need the added performance ?
Larry is correct. The CS prop gives an RV the maximum performance it is capable of with any specific engine.
In 17 years and 1300+ hours of flying RV's (both FP and CS), I have never, ever, found my self sitting at the end of a runway with the throttle in my hand, wishing I was in an RV that had a CS prop on the front (nor have I ever completed a takeoff and afterwords vowed to never do that again in a fixed pitch RV).
I have flown RV's in the Rocky mountains a lot. I just completed a trip to OSH and back with my 180 FP RV-6A. There is not a single airport in all of the Rocky's that I wont land at, but would if it had a CS.
I will admit there are times I somewhat wish I had a CS. I can cruise at the same speeds as someone with a CS at most any altitudes people usually fly RV's; I just have to do it at higher RPM's. It is a little bit noisier and more fatiguing but I feel it is a worthwhile trade off for the big difference in cost, maint, and slight difference in weight. The other trade-off is that the higher RPM's result in very slightly higher CHT's and oil temps, but in all operating modes it is not a factor.
I always come back to being satisfied with the performance I get considering the big difference in cost.
Choosing a FP prop in no way makes for a substandard RV, and it will not effect the utility/usefulness of the airplane. This is assuming the use of a metal Sensenich. The wood and composite props also have great performance but limit the airplane utility somewhat because they result in an empty C.G. position that reduces baggage capacity slightly (just the opposite of a constant speed where the airplane actually has better handling with some weight in the baggage compartment).
It is a big decision...
The great thing is that regardless of which way you choose, you get a great performing airplane either way.
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.
Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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08-07-2010, 12:20 PM
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Senior Curmudgeon
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Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 15,420
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Well said Scott.
Scott, that is one of the best statements concerning props I have ever seen.
Thanks.
__________________
Mike Starkey
VAF 909
Rv-10, N210LM.
Flying as of 12/4/2010
Phase 1 done, 2/4/2011 
Sold after 240+ wonderful hours of flight.
"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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08-07-2010, 12:43 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 rvbuilder2002
...In 17 years and 1300+ hours of flying RV's (both FP and CS), I have never, ever, found my self sitting at the end of a runway with the throttle in my hand, wishing I was in an RV that had a CS prop on the front (nor have I ever completed a takeoff and afterwords vowed to never do that again in a fixed pitch RV).
I have flown RV's in the Rocky mountains a lot. I just completed a trip to OSH and back with my 180 FP RV-6A. There is not a single airport in all of the Rocky's that I wont land at, but would if it had a CS...
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Very well said Scott. I have flown with a lot of RVs in a lot of places and at high altitudes. The fixed pitch prop has never caused me to not be able to keep up and has never caused me to not land someplace. The performance is terrific.
The picture below was snapped at 17,500 MSL in the middle of summer. If I am reading the instruments correctly the density alitude was over 19,000 feet. 120 knots indicated for a true of about 164 knots (GS of 206 knots). I think that is pretty good altitude performance.
The main thing I miss about a constant speed is the acceleration during the takeoff. That is fun for a few moments. I actually prefer the way a fixed pitch airplane acts during the landing.
__________________
Larry Pardue
Carlsbad, NM
RV-6 N441LP Flying
Last edited by n5lp : 08-07-2010 at 08:05 PM.
Reason: Spelling
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08-07-2010, 08:00 PM
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Join Date: Nov 2006
Location: Albuquerque
Posts: 297
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wood fp cg
just got done weighing my -9A with the Sterba wood prop.
I was worried I was too light in the nose to carry much behind the seat without exceeding the aft CG limit.
To my surprise, I couldn't exceed the aft CG with almost any combination of fuel, passengers or bags. Two 200 lb "bubbas", 30 lb of fuel and 100 lbs of bags and it still did not exceed the aft limits.
BTW, my total weight was 1044 and the nose had 262 lbs.
Dave
-9A ground testing
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