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  #11  
Old 09-11-2018, 04:18 PM
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snopercod snopercod is offline
 
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I've flown with both a 3-blade Catto and a 2-blade Aymar-Deumth (also Great American). The vibration was much less with the 3-blade, but the takeoff performance was wimpy. Since I ordered a "cruise" prop, that was probably my fault. All I know is that I was only getting 2300 RPM on takeoff and it took me 4,000' to break ground on a hot day in Denver. The big difference was the glide performance. At best glide speed my rate of descent was 1,800 fpm with the 3-blade Catto and only 200 fpm with the two blade. I have video for the non-believers.
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  #12  
Old 09-11-2018, 07:35 PM
N49ex N49ex is offline
 
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Default Hartzell 2 blade v.s.3 blade

I originally had a F7666-2 commonly used prop on an I/O-360 and replaced it with a 3 blade Hartzell scimitar prop. While the general wisdom is a 2 blade being faster than a 3 blade, my experience was the 3 blade climbs better AND achieves the same cruise speed. I attribute that ideal performance find to the improved design of the scimitar blades.

Reinhard Metz
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  #13  
Old 09-13-2018, 10:10 PM
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charosenz charosenz is offline
 
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Quote:
Originally Posted by snopercod View Post
I've flown with both a 3-blade Catto and a 2-blade Aymar-Deumth (also Great American). The vibration was much less with the 3-blade, but the takeoff performance was wimpy. Since I ordered a "cruise" prop, that was probably my fault. All I know is that I was only getting 2300 RPM on takeoff and it took me 4,000' to break ground on a hot day in Denver. The big difference was the glide performance. At best glide speed my rate of descent was 1,800 fpm with the 3-blade Catto and only 200 fpm with the two blade. I have video for the non-believers.
Thanks for sharing that is fascinating.

What was the diameter of the 2 blade and 3 blade props?
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  #14  
Old 09-14-2018, 10:19 AM
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snopercod snopercod is offline
 
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Originally Posted by charosenz View Post
What was the diameter of the 2 blade and 3 blade props?
Both were 62". The Lancair is so close to the ground that it requires a smaller prop. I still only have 7" clearance. The Catto 3-blade was a 62x76 and the two blade props were 62x75. I'm running the Great American 62x75 now. It's old and beat up but it really works well with my 140 HP high-compression O-290-D2. I see 2,300 rpm on takeoff vs. 2,140 with the Catto 3-blade.
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  #15  
Old 09-14-2018, 12:05 PM
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Originally Posted by charosenz View Post
Thanks for sharing that is fascinating.

What was the diameter of the 2 blade and 3 blade props?
Keep in mind that Snopercod is flying a Lancair so a direct comparison might not be appropriate. The Lancairs are very fast but also need higher speeds for takeoff and landing, due to the laminar flow wings.

I have a 3 blade Catto and spin ~2300 on take-off roll and off the ground in around 600 feet. I generally climb around 115-120 KIAS. Very smooth operation.
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  #16  
Old 09-14-2018, 01:40 PM
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Originally Posted by Raymo View Post
The Lancairs are very fast but also need higher speeds for takeoff and landing, due to the laminar flow wings.
For the record, My Lancair breaks ground at 65-70 KIAS and lands at 75-80 KIAS. I am convinced the reason my takeoff performance was so wimpy with the Catto 3-blade was that I told Nicole that I wanted a "cruise prop" and that's what they made for me. It worked great at cruise, especially up in the low teens.
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  #17  
Old 09-14-2018, 02:25 PM
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Greg Arehart Greg Arehart is offline
 
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A bit late getting back to you on the diameters. Sensenich was 72" diameter and Catto is 68" so I gained 2" of clearance. Seems like a lot more than that. Both of mine are pitched for cruise and turn around 2250 max near SL. I still have no issues getting off the ground and climbing. The other day (solo) I took off at around 9000 DA and was seeing 2100 fpm on climbout. Not bad for a cruise prop!

Greg
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  #18  
Old 09-14-2018, 11:14 PM
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charosenz charosenz is offline
 
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Originally Posted by Greg Arehart View Post
A bit late getting back to you on the diameters. Sensenich was 72" diameter and Catto is 68" so I gained 2" of clearance. Seems like a lot more than that. Both of mine are pitched for cruise and turn around 2250 max near SL. I still have no issues getting off the ground and climbing. The other day (solo) I took off at around 9000 DA and was seeing 2100 fpm on climbout. Not bad for a cruise prop!

Greg
Greg,

I really appreciate the follow up thank you.
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  #19  
Old 09-14-2018, 11:16 PM
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charosenz charosenz is offline
 
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Quote:
Originally Posted by Raymo View Post
Keep in mind that Snopercod is flying a Lancair so a direct comparison might not be appropriate. The Lancairs are very fast but also need higher speeds for takeoff and landing, due to the laminar flow wings.

I have a 3 blade Catto and spin ~2300 on take-off roll and off the ground in around 600 feet. I generally climb around 115-120 KIAS. Very smooth operation.
Quote:
Originally Posted by snopercod View Post
For the record, My Lancair breaks ground at 65-70 KIAS and lands at 75-80 KIAS. I am convinced the reason my takeoff performance was so wimpy with the Catto 3-blade was that I told Nicole that I wanted a "cruise prop" and that's what they made for me. It worked great at cruise, especially up in the low teens.
Thanks to both of you, great info, very helpful.

Charlie
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