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  #1  
Old 08-28-2017, 12:19 PM
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N333M N333M is offline
 
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Location: central Il
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Default Anybody using a 2 blade Catto?

I am wondering if anyone has any info on the 2 blade Catto, vs the standard 2 blade metal Sensenich prop on a 9A? I have the 79 pitch metal sensi, placarded for 2600 rpms max, and it seems a little ..well..just not optimal. My indicated airspeed is about 175 or so at 2600, and I do have to pull the throttle back a tad as it will exceed 2600 (160 hp). Climb performance seems a little sluggish, ( from the engine rpm standpoint ) And it takes a long time for the engine to bring it up to speed when leveling out..could be just my perception, as I have not had experience with an airframe with such a wide performance envelope before, admittedly.
Anyway, would like to hear of others experience.
One thing I am awfully happy about however, is the 2350 rpm cruise, at 155 to 160 mph indicated, and 6.7 gph! Not sure I would want to change anything if I had to give that up!
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  #2  
Old 08-28-2017, 01:28 PM
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AX-O AX-O is offline
 
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I have quantitative and qualitative data for the props on a -4. if you are interested, I can post some of the results. I did not want to derail this by posting for a different airframe although it should be similar enough.
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  #3  
Old 08-28-2017, 02:11 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by N333M View Post
I am wondering if anyone has any info on the 2 blade Catto, vs the standard 2 blade metal Sensenich prop on a 9A? I have the 79 pitch metal sensi, placarded for 2600 rpms max, and it seems a little ..well..just not optimal. My indicated airspeed is about 175 or so at 2600, and I do have to pull the throttle back a tad as it will exceed 2600 (160 hp). Climb performance seems a little sluggish, ( from the engine rpm standpoint ) And it takes a long time for the engine to bring it up to speed when leveling out..could be just my perception, as I have not had experience with an airframe with such a wide performance envelope before, admittedly.
Anyway, would like to hear of others experience.
One thing I am awfully happy about however, is the 2350 rpm cruise, at 155 to 160 mph indicated, and 6.7 gph! Not sure I would want to change anything if I had to give that up!
Indicated airspeed is a poor indicator to use as a comparison of performance.
I suggest you first start using true airspeed (best to do some testing first to confirm calibration of you ASI). Particularly when you are mentioning at what altitude that is at. At 10,500 my RV-6A indicates only 160 MPH but the true airspeed is over 190.
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Old 08-28-2017, 03:48 PM
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Raymo Raymo is offline
 
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Top end could certainly be impacted, from what you've said. Having to hold that horse back to avoid > 2600 RPM. Not a big deal in cruise flt above 8000 ft where you likely can't make it turn that fast.

Are you progressively leaning during WOT climb to maintain peak EGT minus 250 degrees ROP? Once below 65% or so (~8000 ft), you can lean for best power (RPMs) to improve a bit more.

John Deakin has a great article on this topic.

Hopefully I haven't misrepresented his information
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  #5  
Old 08-28-2017, 09:58 PM
rightrudder rightrudder is offline
 
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I've got a -9A (160-hp IO-320-D1A) with a 70x70 two-blade Catto. Going back to Oshkosh I achieved 145 KTAS at around 7.0-7.2 gph, and 155 KTAS at 8.0 gph, with DA ranging from 10,500 to 12,000 feet. It was spinning pretty fast at 155 kts, between 2600 and 2650 rpm IIRC. Very smooth at those engine speeds. At 8000' DA, it'll top out about 170 KTAS...just what Van's promised.
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  #6  
Old 08-29-2017, 08:53 AM
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I use a Catto 2-Blade. Here is some performance data. This is at 8,000 DA

KTAS 154
RPM 2600
MP 23.7
GPH 7.8
%Power 74
NM/G 19.74

"WOT"
KTAS 162
RPM 2740
MP 24.3
GPH 9.0
%Power 82
NM/G 18.00
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  #7  
Old 08-29-2017, 05:21 PM
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AX-o, Yes, Id love to see some stats on props info for your -4!

Scott, I understand, I just installed a new ASI..actually a Garmin G-5, and had it calibrated, along with the old ASI which I left in the panel. The avionics guy used a manometer. I was present, and will do it myself next time! The speeds I quoted are all at or below 3500 ft. An no, it wont turn that fast a 10k
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  #8  
Old 08-29-2017, 05:31 PM
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Raymo,
Thanks for the reply!
unfortunately, I dont have EGT monitoring yet, (which is killing me) so I am leaning the old fashioned way..pull till it coughs..then turn it back in a bit. And I have read Johns Pelican perch on leaning ..several times, trying to get it all to stick. At OSh this year I spent alot of time looking at several EIS methods..as when I bought the craft a few months ago, the avionics were a little buggy, (all steam gages) so its getting a panel upgrade..and after going back and forth between Dynon, GRT, MGL, and Garmin about 3 times each in two days..(till my wife just rolled her eyes and went back to the campgrounds) , I was trying to decide which way to proceed with the upgrade, I finally gave up, just bought a G-5 to get me by , and came home to digest all the choices..wow things are changing so fast I cant keep up, and it kind of , overwhelmed me..Had the money to buy..but couldnt decide.
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Last edited by N333M : 08-29-2017 at 05:45 PM. Reason: spelling
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  #9  
Old 08-29-2017, 05:41 PM
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Doug, and Tony Thanks for those numbers!
Doug, What is the engine turning at WOT..170 kts at 8000 DA?

Tony, What engine do you have in that beautiful Taildragger? And do you remember what pitch Catto you are running?
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  #10  
Old 08-29-2017, 09:49 PM
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Quote:
Originally Posted by N333M View Post
Scott, I understand, I just installed a new ASI..actually a Garmin G-5, and had it calibrated, along with the old ASI which I left in the panel. The avionics guy used a manometer. I was present, and will do it myself next time!
You still need to do an airborne GPS TAS check. A manometer will not show a static source installation location error. That can only be done while actually flying.

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