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  #41  
Old 08-07-2010, 08:33 PM
elippse elippse is offline
 
Join Date: Dec 2006
Location: Arroyo Grande, CA
Posts: 938
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There is an assumption in this discussion that a cruise prop cannot be a climb prop. This is based on old, outdated technology and is simply not true. The three blade prop on my plane has over 90% efficiency in cruise at over 200 mph and at least 82% efficiency in a climb at only 105 mph IAS. My plane has only 125 hp and a wing with only 77 sq. ft., but it will climb at over 1500 ft./min at 1350 lb and 2400 rpm, which is 86% of the available power. No existing propellers can claim that kind of efficiency in cruise; I know, for I have run tests on many different types. Efficiency is what turns horsepower into thrust. You must resign yourselves to the fact that this saying is no longer true. It's like saying that a car that gets great gas mileage on the highway gets poor mileage in town. The higher the peak efficiency, the higher will be the efficiency all along the curve below peak. If a propeller has high cruise efficiency, it will also have high climb efficiency. High efficiency is high efficiency and that's all there is to it!
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  #42  
Old 08-07-2010, 10:52 PM
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rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
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Quote:
Originally Posted by Daver View Post
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
Is this with an O-320?
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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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  #43  
Old 08-08-2010, 06:55 AM
Daver Daver is offline
 
Join Date: Nov 2006
Location: Albuquerque
Posts: 297
Default fp weight

Yes, Scott, the engine is an O-320E2A (150 HP). Its a few lbs lighter than the 160 HP versions

Dave
-9A ground testing
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  #44  
Old 09-06-2010, 05:55 AM
handkas handkas is offline
 
Join Date: Dec 2009
Location: Poland
Posts: 15
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Quote:
Originally Posted by Ron Lee View Post
180 HP or better engine

CS prop
why is that? I was told that a FP will never exploit max power of -360, but sensenich does make props for this engine (85") don't they?

considering the cost and all you said here, i also think a FP will be enough for my cross-country flying, but I am still wondernig which engine to use

I know the rpm limitations of props for -320 and I'll be satisfied with perfomace. Does -360, FP make a diffrence?

also, do you know anything about GT propellers (wood-composite)? I use one on my remos G3. I love the costs and maintainance.
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  #45  
Old 09-09-2010, 01:03 PM
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Sam Buchanan Sam Buchanan is offline
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Join Date: Dec 2004
Location: North Alabama
Posts: 4,301
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Quote:
Originally Posted by brian View Post
What do you folks think would be the pros and cons of choosing between fixed pitch and constant speed, particularly 160 HP fixed pitch and 180 HP C/S? Performance differences?
Brian,

Use the Search feature of the forum to find a ton of info concerning your question, it gets asked often. Here are some threads to get you started:


http://www.vansairforce.com/communit...constant+speed
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RV-6
Fokker D.VII replica

Last edited by Rosie : 09-09-2010 at 04:58 PM.
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  #46  
Old 09-09-2010, 01:20 PM
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MauiLvrs MauiLvrs is offline
 
Join Date: Jan 2008
Location: KTCY
Posts: 643
Default In love with our C/S on our 9

Quote:
Originally Posted by brian View Post
What do you folks think ...
I think, no, I know, that we are in love with our C/S on our 9 .... Because...
On a nice cool morning....
Flaps 20
Mixture forward
Prop forward
Roll onto runway and line up
Throtle 1/4 ... nose comes off
Throtle 1/2 ... plane get light
Throtle full ... plane jumps off the runway
Around 150 feet

And when we come blasting over the airport at 150 kts, it is no problem getting down to 70 kts on final after a break to downwind

Has anyone lately said how great Van's aircraft are
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RV-9A Flying - 330 Hrs. Painted Finishing the interior.

Last edited by MauiLvrs : 09-09-2010 at 01:23 PM.
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  #47  
Old 09-09-2010, 04:41 PM
Mile High Relic Mile High Relic is offline
 
Join Date: May 2010
Location: Denver area
Posts: 272
Default My advisor says...

I have been working with someone as I look for planes. I had found a really nice plane, but it had a fixed pitch prop. I'm in Denver, and my advisor said "I really think you will be happier in the long run if you buy an RV with a 180 HP engine and a constant speed prop. In Colorado, on take off, you are only pulling 24" of manifold pressure, and with a fixed prop, only 2250 RPM, which is about 60-65% power on take off. With a constant speed, you will pick up an extra 10% plus in power for take off and climb, cruise will not be much different."

If I still lived in the midwest I'd have gone with the fixed pitch, because for me, simple is good. A fixed pitch prop is stupid simple, both from a flying and maintenance perspective.

After talking to my advisor and some local builders, I have decided that I will hold out for a plane with a C/S prop.
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  #48  
Old 09-09-2010, 05:51 PM
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flyboy1963 flyboy1963 is offline
 
Join Date: Oct 2008
Location: Lake Country, B.C. Canada
Posts: 2,416
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[quote=MauiLvrs;465913]I think, no, I know, that we are in love with our C/S on our 9 .... Because...
On a nice cool morning....

Flaps 20
....etc
[quote]


Hey Dave,
as a -9a driver with little time on type, I am trying to assemble the correct operational data.

why 20 degrees of flap for takeoff? Have you tested this as the best lift for the wing? If so, that can't be easy to do, so I'd like to do the same for myself, and wonder how to go about it exactly.
I asked Van's what the best lift flap setting was, and they referred me to John Roncz. If I recall, he said that he expected best lift at somewhere between 15 and 20, ( I had guessed 10!) but that this should be verified. ( for the individual aircraft, CG , loading condition etc I assume)

sorry to hijack this thread, but if you or anyone knows, obviously it could be very important to use the right setting for critical obstacle clearance & hot & high ops.

regards,
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Perry Y.
RV-9a - SOLD!....
Lake Country, BC

Last edited by flyboy1963 : 09-09-2010 at 05:53 PM. Reason: quote fix?
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  #49  
Old 10-08-2010, 11:17 AM
HBpilot HBpilot is offline
 
Join Date: Apr 2010
Location: Ocala, FL
Posts: 76
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What does the extra maintenance for a CS involve ? (cost and work)
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  #50  
Old 10-08-2010, 11:29 AM
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Jamie Jamie is offline
 
Join Date: Jan 2005
Location: Atlanta, GA
Posts: 2,295
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Quote:
Originally Posted by HBpilot View Post
What does the extra maintenance for a CS involve ? (cost and work)
Lube at each annual and follow overhaul procedure (which can vary for each manufacturer or even prop model). Most Hartzell manuals say to overhaul every five years.
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Jamie | RV-7A First Flight: 7/27/2007 (Sold)
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