CATTO 2 Blade vs 3 Blade

[toninialex]

I've personally pushed my company to make 3 blade G.A prop for RV and similar planes. Reading all your feedback from years I understand that I was right !
http://www.gt-propellers.com/wp-cont...P-GT3-G-37.pdf
Pitch selection, static RPM choice, diameters available, top cowling removal are much easier.
On my 4 with 320 I?m going with 2 blade CS light blades technology on HC.Y hub .

Cheers Alex

[Raymo]

Originally Posted by Reaver

Hi Dave,

Thanks for the fast response and details. I'm already sold on a Catto for my RV-7A, the only question is how to pitch it. Do you have any suggestions here? Stock IO-360 parallel valve engine and cowl, and the only exterior options I have planned so far are the extended rail for the sliding canopy and the step to help shorter people get on and off the wing.

I have the same setup with SJ cowl. Below is the data from my tag. I can just barely get 2700+ RPM at 5500' alt (haven't tried WOT any higher). Still working to clean up a few things to reduce drag a little more. One P-Mag, one Slick. Super tracks installed and dual steps as well. Planning for a Superior cold air sump later this year, which is said to add 7 HP.

Cruise is 160 KTAS @ 8.2 GPH @ 8500-12.5k DA. 2550-2600 RPM.

This is the prop Catto recommended with my setup. When I first started flying, without gear fairings, she was a lot slower (~20 MPH) and CHTs were difficult to control (have since properly tuned the P-Mag, as well).

Glass/2XCarbon Composite 3-B #09165272
Diameter: 68” Pitch: 75” NLE RV-7A
Engn :I0-360 180HP Dsgn RPM 2750
Red Line RPM max. 3200
Torque: 40 ft lbs. 7” Crush Plate Required
Manufacture Date: October 2016

[db1yg]

"Catto for my RV-7A, the only question is how to pitch it"

Alexander, I would recommend you give Nicole or Craig a call to discuss your typical flying performance needs (take off, cross country, racing, etc) and they can guide you in the right direction reference pitch. Both are incredibly knowledgeable and really want you to be satisfied with the Catto!

"effect of different propeller diameters"

Hey Steve, I think the 67" for the 160hp vs 68" for the 180hp is simply a way of reducing blade area for the slightly lower power engine -- but again, Nicole could give you the technical reason.

You guys have fun and fly safe!

Cheers,
db

[FLY6]

Could somebody who has tried both a 2 blade and 3 blade on their plane please chime in. Lots of post saying how the 3 blade makes it more difficult to remove the lower cowl. How difficult is it compared with a 2 blade, really difficult, just a bit more difficult? Just trying to get a good idea so I can make an educated decision.

Thx

[Mel]

Originally Posted by FLY6

Could somebody who has tried both a 2 blade and 3 blade on their plane please chime in. Lots of post saying how the 3 blade makes it more difficult to remove the lower cowl. How difficult is it compared with a 2 blade, really difficult, just a bit more difficult? Just trying to get a good idea so I can make an educated decision.
Thx

Looks like you have a taildragger. The difficulty removing the cowling with a 3-blade prop is directed to the nose gear airplanes. I have no problem removing the cowling on my -6.

[FLY6]

Thank you for the quick reply. I do have a tail dragged. Years back when I told Craig I had a 150 hp, he suggested a 2 blade. I will check back with him and see if he still suggests a 2 blade with my engine upgraded to 160 hp.

Thx again

[Lufthans]

We have a 3 bladed Catto on our -4. Removing the lower cowling is a bit of a pain, as you want to slide it forward to clear the gear legs, yet run into at least one prop blade then. Best is to have the prop with one blade pointing up. The cowling WILL clear the lower blades, but not by a big margin.

Having said that, I wouldn't want to swap the prop for a two blade. It is ultra smooth and seems to be very efficient. We're getting ridiculous performance from our 160 hp engine with it. Highly recommended!

(and how often do you remove your lower cowling, really?)

[charosenz]

Originally Posted by db1yg

Back in late 2013/early 2014 I did much of the testing for Craig on the gen 3 Catto Carbon Fiber three blade design for the side by side Rvs equipped with the 180 hp Lycoming--I think Axel was simultaneously testing the pitch/design options for the tandem RVs. After the testing was complete and Craig went into production I decided that the optimum prop for my RV9a/180 (James long cowl) to be a gen 3 with 74 1/2" pitch by 68" diameter 3 blade. If you would like to see the test results do a search for "2005 Catto 3 Blade vs. 2014 Catto 3 Blade".

Based on the performance I was getting with the 3 blade, a friend with an RV9a/180 also ordered a 74 1/2 pitch but he got a 2 blade. The point of all this is that eventually my friend opted to go constant speed and I tested his 2 blade on my plane back to back with my identically pitched 3 blade. The differences I noted where as follows:

The 3 blade was noticeably smoother in cruise
The 3 blade was quieter in cruise-due to the slower tip speed at same rpm
The 3 blade climb out was better--I recall around 150-200 fpm better climb
The 2 blade was 2 knots faster in my typical cruise-60-65% lop 8k+DA
I did not detect much difference in "braking action" at power down
On my plane, the 3 blade just looked great IMO.
Bottom cowl removal was more difficult with the 3 blade

I thought this info may be of value since the two props were tested on the same airframe in as near to identical conditions as possible.

Cheers,

db

Dave,

Was the 2 blade you tested also 68" diameter, or???

[500helicrazy]

Originally Posted by Lufthans

We have a 3 bladed Catto on our -4. Removing the lower cowling is a bit of a pain, as you want to slide it forward to clear the gear legs, yet run into at least one prop blade then. Best is to have the prop with one blade pointing up. The cowling WILL clear the lower blades, but not by a big margin.

Having said that, I wouldn't want to swap the prop for a two blade. It is ultra smooth and seems to be very efficient. We're getting ridiculous performance from our 160 hp engine with it. Highly recommended!

(and how often do you remove your lower cowling, really?)

Hans, what numbers are you getting with your 160hp -4? I have one with a 160, but mine has the early style cowl, so it might help with removal. Haven't flown it yet, but has a metal 2-blade at the moment.

Jared

[db1yg]

Hi Charlie,

Sorry, just saw your question on 2 blade diameter.

The 2 blade Catto I tested back to back with the 3 blade was the same blade design and pitch but the 2 blade was a 72" diameter while the 3 blade was 68.

Hope this helps.

Cheers,

db