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2 blade vs 3 blade. Ever tried both?

charosenz

Well Known Member
I know the general concept (all things equal) is that a 2 blade is generally considered "faster" and a 3 blade a better climb performance prop.

I would appreciate hearing from guys who have actual experience trying both a 2 blade prop and a 3 blade prop on the same plane and how they compared.

Thanks.

Charlie.
 
I know the general concept (all things equal) is that a 2 blade is generally considered "faster" and a 3 blade a better climb performance prop.

....
Thanks.

Charlie.

It depends.

If you are talking about one size fits all store bought props, you are correct.

If you are talking about custom cut props like a Cato, they.can be cut so they have equal performance. It all depends on what you order.
 
Data please

I would like to see the hard data on a fixed pitch prop being equivalent to a c/s prop. Call it engineering curiosity...or skepticism...
 
My first RV was a 7A that had a three blade MT prop. I sold that and then built an RV10 with a two blade prop. Both have been nice aircraft. I've put about 500 hours on each of them.
I think the 7A was a bit slow and I agree with the notion about top speed being slower. It was a good prop though and I was pleased with it.
The RV 10 performs nicely and I am happy with it also.
I liked the three blade because I liked the way it looked and of course the MT quality. However, it was really a pain to take off the lower cowl with the third blade.
The two blade performs a little better (I think) and I find cowl removal a lot easier now. Climb is not an issue for me, though the three blade may be better in that regard. I don't know, both aircraft could climb very well.
I would choose a two blade if I needed another prop, all things considered. Of course, YMMV.

John Koonce
N78MU
 
2 Blade vs 3 Blade

Hi Charlie,

I have done just that using Catto products. Do a search for:

2 Blade Catto vs 3 Blade Catto

My post is #15.

Hope this helps.

Cheers,

db
 
RV-9 with standard Sensenich aluminum prop vs. 3-blade Catto. Both have similar top speeds at 8500' DA (within measurement error). Both get me off the ground in about the same distance. I did not do specific climb tests, but don't think there was a lot of difference in climb performance. 3-blade is definitely smoother-running. And there is distinctly a weight/CG difference (42 lb for the aluminum prop vs. 14 for the Catto). 3-blade has more ground clearance, especially good if you are operating from non-paved strips.

That's my experience.

Greg
 
RV-9 with standard Sensenich aluminum prop vs. 3-blade Catto. Both have similar top speeds at 8500' DA (within measurement error). Both get me off the ground in about the same distance. I did not do specific climb tests, but don't think there was a lot of difference in climb performance. 3-blade is definitely smoother-running. And there is distinctly a weight/CG difference (42 lb for the aluminum prop vs. 14 for the Catto). 3-blade has more ground clearance, especially good if you are operating from non-paved strips.

That's my experience.

Greg

Greg what were the diameter of each prop. I.E. how much clearance did/do you gain switching to a 3 bladed prop?
 
I liked the three blade because I liked the way it looked and of course the MT quality. However, it was really a pain to take off the lower cowl with the third blade.

Finger nail polish takes care of the scratches. 3 blade Catto are cool and effective
 
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.
 
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
 
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?
 
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.
 
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.
 
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.
 
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
 
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.
 
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.

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
 
I just switched my RV8 over to a Catto 3 blade.. 66x77 from the Sensenich 72x85 FP aluminum..

Takeoff performance feels about the same.. Maybe a little stronger now. Both pulled about 2300 on the ground. Catto climbs better than the Sensenich by 600 fpm. 2700rpm at 6,000 msl gave me 6 mph slower than the Sensenich. The biggest change was how much better it slowed down into the pattern. It's MUCH easier now.. Still not like a CS prop but I'm happy. Low rpm thrust changes are more noticeable now as is rudder needed to keep the ball centered. I used to keep about 1200 rpm on it until the mains touched. If I do that now I seem to float half-way down the runway. Working that out now to get my landing length more under control.. Lol.

Oh, and I took 20 pounds off the nose.. Empty weight is down to 1074 and CG back a little for landing is nice when solo. Vibration is almost nonexistent too compared to the Sensenich.
 
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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.

With a 200 FPM rate of decent it will take you 40 minutes to descend from 8000 feet and roughly a 60 mile glide radius. Better yet if you can find a modest thermal you could stay up indefinitely. I suspect maybe you were in a very strong thermal during the testing. My 2 blade RV6 had about a 10 mile glide radius from 8000 feet.
 
I just switched my RV8 over to a Catto 3 blade.. 66x77 from the Sensenich 72x85 FP aluminum..

Takeoff performance feels about the same.. Maybe a little stronger now. Both pulled about 2300 on the ground. Catto climbs better than the Sensenich by 600 fpm. 2700rpm at 6,000 msl gave me 6 mph slower than the Sensenich. The biggest change was how much better it slowed down into the pattern. It's MUCH easier now.. Still not like a CS prop but I'm happy. Low rpm thrust changes are more noticeable now as is rudder needed to keep the ball centered. I used to keep about 1200 rpm on it until the mains touched. If I do that now I seem to float half-way down the runway. Working that out now to get my landing length more under control.. Lol.

Oh, and I took 20 pounds off the nose.. Empty weight is down to 1074 and CG back a little for landing is nice when solo. Vibration is almost nonexistent too compared to the Sensenich.

Doug,

Thanks for sharing your numbers, especially the climb and cruise comparisons.

Charlie
 
i have had a 2 blade wooden and a 3 blade warp on the same plane with a jab 3300. 2 blade was from a quality mfgr. performance wasn't fair to compare because the 3 blade was adjustable and it was ''dialed in '' perfectly. the 2 blade was a little too coarse. 2 blade was balanced but the 3 blade was easily noticed to be smoother.
 
i have had a 2 blade wooden and a 3 blade warp on the same plane with a jab 3300. 2 blade was from a quality mfgr. performance wasn't fair to compare because the 3 blade was adjustable and it was ''dialed in '' perfectly. the 2 blade was a little too coarse. 2 blade was balanced but the 3 blade was easily noticed to be smoother.

Bob, Thank you. I can see the two are hard to compare but for the sake of the discussion, I would be curious of the diameter of each?

Or to put this another way, how much shorter diameter could you reasonably expect for a 3 blade prop vs a 2 blade prop, all things similar....

Not looking for hard numbers but more of a water cooler discussion.

Charlie
 
uh,
i will be at hangar in next day or 2 and will look in the log book. all i remember is sixty something.
 
Two blades are more efficient than three. To absorb higher HP and/or reduce prop diameter more blades may be needed. The Piper Cub at one time had one bladed prop, with counter weight. It was even more efficient. Why? The prop does not have to run in the effect of other blade. However read the link, three like all things trade offs and demands based on aircraft which dictates more than 2 blades... Look at some of the new turboprops, 5 blades.

http://hartzellprop.com/are-more-propeller-blades-better/
 
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