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  #1  
Old 06-26-2017, 07:44 PM
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9GT 9GT is offline
 
Join Date: Jan 2010
Location: Southern Michigan
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Default Propeller Performance: F/P vs C/S

Anybody have any performance comparison numbers switching from the Sensenich F/P propeller to a C/S prop on their RV-9 or -9A? My project, RV-9A, came with the Sensenich F/P prop, but the engine, Mattituck IO-320, is capable of C/S by removing the CS plug and adding a governor. I know the benefits of a C/S prop but just trying to figure out if I want to make the switch while the F/P prop is still new in the box. I would love some before and after the swap performance numbers to help me justify the added costs. Thanks! Dave
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Howell, MI

RV-9A: Under Construction
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  #2  
Old 06-27-2017, 08:24 AM
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MS19087 MS19087 is offline
 
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RV-9A; IO-320 w/ Whirlwind WW-151
(Flying since June 2011)
2017 =VAF= donor
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  #3  
Old 06-27-2017, 09:49 AM
Lars Lars is offline
 
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Watch the weight on the nosewheel.

I just finished an RV-9A for a friend. Vertical draft IO-320, Catto 3 blade prop. It does have a backup alternator and mufflers on the exhaust, but otherwise it's not an exceptionally equipped (read: heavy) airplane.

After weighing I was surprised to discover that, while it would be in the CG range for all conceivable loading conditions, the allowable weight on the nosewheel would be exceeded with more than 3/4 fuel unless at least 30 pounds was carried in the baggage compartment. Lighter passengers/pilots requiring more weight.

More info here: http://www.vansaircraft.com/pdf/Nose...ice_letter.pdf

Likely paint will move the CG far enough aft that it will cease to be a problem, but meanwhile I have 6 pounds of lead under the empennage fairing.

Point being that there is no way this airplane could be safely equipped with a constant speed prop without a serious diet forward of the current empty CG.
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  #4  
Old 06-27-2017, 12:00 PM
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Quote:
Originally Posted by Lars View Post
Point being that there is no way this airplane could be safely equipped with a constant speed prop without a serious diet forward of the current empty CG.
Move the battery aft of the baggage compartment rear wall, and most of the CG shift that you'll need is accomplished.
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Greg Niehues - VAF 2017 dues paid
Garden City, TX
N16GN flying! http://websites.expercraft.com/airguy/
Built an off-plan 9A with too much fuel and too much HP. Should drop dead any minute now.
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  #5  
Old 06-27-2017, 01:05 PM
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Will using a composite CS prop solve the nose wheel weight issue?
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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!
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  #6  
Old 06-27-2017, 01:17 PM
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N941WR N941WR is offline
 
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As for performance numbers, I have never flown my -9 with a CS prop but have flown it with two different engines and FP props.

The only advantage the CS prop gives you is on takeoff acceleration. Cruise speeds can be identical, with often the advantage going to the FP prop. However, to do that, you have to spin your FP prop on the redline, which the engine is designed to do.

If the cost is an issue, you can always install one later.
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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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  #7  
Old 06-27-2017, 01:39 PM
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RV6_flyer RV6_flyer is offline
 
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Default Kitplanes July 2016 Wind Tunnel

Read the Fixed pitch vs. constant speed article in "Wind Tunnel"column from the July 2016 issue of Kitplanes.

I believe that you must be a subscriber to Kitplanes to read the article or any back issue.
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KVVS RV-6
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To those who love aviation, the sky is home.

Last edited by RV6_flyer : 06-27-2017 at 02:51 PM.
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  #8  
Old 06-27-2017, 01:57 PM
rvsxer rvsxer is offline
 
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Quote:
Originally Posted by RV6_flyer View Post
Read the Fixed pitch vs. constant speed article in "Wind Tunnel"column from the July 2016 issue of Kitplanes.

I believe that you must be a subscriber to Kitplanes to read the article or any back issue.
Try this link...
http://www.kitplanes.com/issues/33_7...d_21591-1.html
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RV-6 N207AM w/G3X, 1,400 hours +
South St. Paul, MN (KSGS)
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  #9  
Old 06-27-2017, 03:22 PM
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Steve Melton Steve Melton is offline
 
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I have WW200 and a big 25lb battery. I carry some tools, a fly away parts kit and a fireX in the baggage . it's been good.

Empty Weight with oil included, no paint, with anti-splat nose brace and lip skid, firewall insulated with 1" ceramic fibre
Left 389.5 lb
Nose 280.8 lb
Right 411.5 lb

Total 1081.8 lb

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Steve Melton
Cincinnati, OH
RV-9A, Tip-up, Superior O-320, roller lifters, 160HP, WW 200RV, dual impulse slick mags, oil pressure = 65 psi, EGT = 1300F, flight hours = 600+ for all

Simplicity is the art in design.

Last edited by Steve Melton : 06-27-2017 at 03:30 PM.
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  #10  
Old 06-27-2017, 04:06 PM
Steve Koziol Steve Koziol is offline
 
Join Date: Sep 2011
Location: Doylestown, PA
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I haven't flown behind a Sensenich FP but I have over 700 hrs on a 3 blade Catto. Some specs on my airplane.
Total weight 1084 lbs
Right Main 395lbs
Left Main 394lbs
Nose Wheel 295lbs

AeroSport Power O320 D2A, roller tappets, dual Slick Mags, and a backup alternator where the vacuum pump would be attached on the rear of the engine. Climb performance at 100-110 knots is about 1200 to 1300 fpm at moderate weight. (1550lbs or so).

For me, the climb performance and cruise speeds are far better than anything that I flew in the past. I didn't see the need to drop another 8-10K for the prop and governor for what I felt was a minimal increase in performance. Just my thoughts. Good luck on your search.

Steve Koziol
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