Prop Quandry: Installation of 3-blade??

I am replacing my Sensenich wood 2-blade with a Catto 3-blade fp and I am wondering about how to do that.

Should the odd blade be pointing 'UP' or 'DOWN' when that O-360 A1A is stopped? Is there something critical about the #1 cyc. and TDC?

Hints and suggestions graciously accepted and appreciated.

Jim

Since it is a 3-blade and you have 4 compression strokes, it will stop different every time anyway, so....it doesn't matter.

Thanks, Mel.

I almost suspected as much, but before bolting that thing on, I wanted to plumb the depths here. I have no indications from Catto or anyone else there should be a preferrential mounting, but, I have made my share of blunders in the past; some rather costly.

What clock position is it.

Mel said:

Since it is a 3-blade and you have 4 compression strokes, it will stop different every time anyway, so....it doesn't matter.

Click to expand...

3 blades and four compression strokes. Not sure how that works.

I would suggest using the same logic that puts a typical two blade prop at 9 and 3 o'clock position- or thereabouts, for best hand prop-ing. Not a fan of hand propping high compression engines BTW, but the technique is pull the #1 cyl top plug out, pull engine thru with thumb over the hole. When you get near the compression stroke and TDC, mount the prop so the one of the 3 blade is near the 9 o'clock position.

The other reason for "Clocking" a prop is for vibration reasons. On a wood prop that's should not be an issue, I would guess? Last, do what every you think looks best. As Mel said or implied it does not matter.

PLEASE, if you get a chance could you record a before and after performance at say 8,000 feet density altitude, WOT, and please post the results. It would be interesting to not the speed difference. I guess the Sensenich from other flight test is several MPH faster. Thanks

I have the same setup and agonized over this question. Talked to folks at both Catto and Van's. They convinced me that no matter how you mount it it will always look the same when it stops. I've found this to be true - it always stops in the same position - albeit not always the same blade in the same position. I think it looks cooler with one blade straight up so I usually turn it to this position by hand when done flying.

John Miller

Prop me up...

Guys,

I was fortunate enough to be Craig Catto's first RV4 customer. I flew a 2 Blade 69X72 on my RV4 when I had a 150HP 0-320. My hangar mate bought the 3 blade Catto for his 160HP RV4 and we flew together alot. As you would figure, the 3 blade had slightly better t/o and climb, but the 2- blade had the edge in cruise by 5 knots or so with the same RPM. However comma, the 3 blade Catto was hands down the smoothest prop I have ever flown behind and a wonderful acro prop. Also, with the RV4 short gear it has better ground clearance.
I measure FP prop performance by the MP/RPM split at 2000' MSL. I have found that a prop that matches the 2 (or a slightly lower MP) at 2000' seems to give the best all around performance.
I have flown the 70 CM sensy metal and the "Sensy woodie" on several RV's. Both will have similar cruise numbers to the 2 and 3 blade Catto, albeit with both Catto's at higher RPM. In an all out drag race, my 2 blade Catto would beat a equal HP RV4 with a sensy metal every time, but at 2750-2800 RPM vs the Sensy's 2600 restriction. Recently I flew formation in a 150/ Sensy woodie RV4 with a 160HP RV4 with a 66X80 Catto 2 blade. The Catto again would leave me in the dust above 2500 RPM. If you do nothing but XC, fly very little or no acro, don't like torque wrenches and like flying through rain, the sensy metal is for you. If you ever ding the prop with a sensy metal, it's an engine teardown, not always so with the Catto, just buy another prop. Again, the sensy metal is alot heavier, vibrates a bit more, has a placarded 2600 RPM restriction, and a "no acro" recommendation by Sensy.
Those 4 things alone sold me on a composite prop and Craig Catto's are top notch. I think you will find the Catto 3 blade way outperforms your "woodie sensy" in almost every department.

I am running a 2 blade MT fixed pitch on my new 0-320 (170hp) which also works very well....

RR

RR, does the MT fixed pitch, being composite over wood, require retorquing every 25 hours or so like a wood prop?

Thanks, smokyray.

Your reply is greatly appreciated and valued.

Torque ethic...

Hi Randy,

Yes, The MT requires re-torqueing every 50 hours but like Craig Catto's props, they are alot harder and don't "squeeze" as much as wood prop. At 50 hours my torque wrench only moved 2 of the 6 nuts, the rest were still up. In 100 hours on the MT so far, the real strength is the SS leading edge and finish which is absolutely impervious to rain and grass/runway debris on my rough grass strip. Also, the engineering done on my prop is so close to the desired performance I put on my "dream sheet" it's amazing. It performs within 1% of the best prop I ever had on the airplane in cruise,and outclimbs that prop, a testament to MT's engineering dedication. The cost: within 10 bucks of the Sensy metal...
Looking forward to seeing your RV3 fly!

See ya!

RR

Why not check torque every time you do an oil change? cowls off, possibly spinner also. FWIW I check mine every 25- 30 hours @ oilchange and have yet to find loose prop bolts. Some require a tad of tightening or loosening but nothing to get excited about.
Tom
RV3 catto 2 blade, performance props 2 blade
2000+ hours

Rv4 Performance

Hey Smokey

What are the numbers for the Bandit?
Empty weight
Top speed @ 8000 msl
Stall speed
Best Climb performance
My RV4 will be finish soon and my O320 is about 170hp with a Catto 3 blade prop .My empty weight is around 930 lbs so I am looking for some bench mark for performance.
Also I am curious how my -4- will compare with my friends RV 6. There weights are 1100lbs and 1180 lbs they both have 180 hp C/S set up.

I too am curious about the Bandits performance. Also, I have just purchased a -4 with an Aerosport O320 (160hp) and 2 blade wood prop. Smokey, could you please comment on the performance differences between the 2 blade MT versus Catto 3 blade? I have narrowed the choice down to those props and really value your opinion (based on flying behind them both).

Steve Fitzgerald
[email protected]

Torque em...

You bet, first the big difference between the Catto and the MT (not that it matters to me) is the MT is a certified prop built in a factory by German dudes. They will probably be there in 10 years if you need it fixed. Craig Catto is a master craftsman building props at his home, if he retires, you're on your own. Both however, are works of art.
The flying comparison for me (after 5 props) begins with a static test followed by takeoff, climb cruise and the all important aerobatics. The Bandit weighs 955# empty stalls at 60 clean and bottom of the dial dirty. A very basic VFR RV4 overall.
The Catto 3 blade is a strong, light and extremely smooth prop, perfect for acro and climbing. It had 2200 static, 2350 climb@1500 fpm and maxed out at 2850/ 200 mph at SL. The MT however matches all of the numbers my Catto had in climb,(1500 fpm at 100 mph 90F)at 100 rpm lower and does great acro and cruises faster for the same RPM than the Catto. The MT maxes out at 2700 RPM/200 mph(173 knots GS) at SL. At 8500' the MT at full throttle gives me 2620 RPM at 175 mph/155 Knots indicated (172 knots true)8.8 GPH. I have noted the MT burns <>1 GPH less gas at equivalent speeds than my Catto. I wonder how fast the Bandit would be with Van's new wheelpants....hmmm.
I had very specific requirements for the MT engineers as I was their first Fixed Pitch Scimitar RV4 customer last year. The numbers I requested from my prop to MT were almost exactly what I experienced on the first flight, a testament to MT's engineers. What has really won me over on the MT is leading edge protection. After 1 year of "Southern US flying" my Catto was pitted from light rain, sand and grass where I fly. I installed leading edge tape on the Catto which worked but robbed performance noticeably. The MT so far cleans up with a rag with Windex and has nary a scratch even after several "shower skirts" at cruise RPM. The MT costs about $400 more than Craigs prop, I feel it is worth it.

I do check my bolt torque every oil change, I have a filter...its' 50 hours for me...Good Luck!

RR

[/URL][/IMG]

smokyray said:

I measure FP prop performance by the MP/RPM split at 2000' MSL. I have found that a prop that matches the 2 (or a slightly lower MP) at 2000' seems to give the best all around performance.
RR

Click to expand...

Can you explain what you mean by "matching the 2"?

Perfect Match...

Yes Sir, I have found with FP props that have an equal split of MP/RPM at SL to 1000' MSL at cruise is a very good prop combo for all around performance ie 24" and 2400 RPM. At 2000' MSL RPM should be 100 higher than the MP IE: 23" with 2400 RPM. At 8000' 20" and 2600 RPM is optimum performance for fuel efficiencyfor the Bandit. A higher split ie 20" and 2700 RPM at SL means you have a climb prop and cruise will suffer. If MP is 25" and RPM of 2200 you have too much bite and a high cruise prop. There comes a point where you lose efficiency with too much bite and that number seems to be 27" and 2300 rpm in level flight at SL with a max rpm less than 2500. You just won't get the most power out of your engine with too much bite.
The engineers at MT seem to have this process down to a science and nailed the performance I have searched for for 10 years the first try...

RR

Too New To Know

Excellent analysis and explanation. Now, as a total newbie to both aircraft ownership and the way cool RV world (this site is outstanding), I have what is probably a "roll your eyes" question. Does the MT prop, which I am now sold on, come from the factory as you described it or do I have to provide MT with additional engine information beyond the fact that it is an Aerosport O320? Again, thanks for your patience.

MT for thee...

Steve, When you fill out the order form for the MT prop it has a detailed questionaire with very specific questions as to: Type A/C, Horsepower, weight, cruise speed, stall speed, desired diameter, color (white,black,or grey) and desired maximum RPM. My recommendation is rated RPM for max (2700) and 69" diameter. You might get an email from the engineer in Germany asking even more detailed questions. You need to know fairly accurately how much HP your engine is slated to produce as it's critical to performance. Good Luck...

RR
http://www.mt-propeller.com/index.htm

MT Prop Question for "SmokyRay"

smokyray said:

Steve, When you fill out the order form for the MT prop it has a detailed questionaire with very specific questions as to: Type A/C, Horsepower, weight, cruise speed, stall speed, desired diameter, color (white,black,or grey) and desired maximum RPM. My recommendation is rated RPM for max (2700) and 69" diameter. You might get an email from the engineer in Germany asking even more detailed questions. You need to know fairly accurately how much HP your engine is slated to produce as it's critical to performance. Good Luck...

RR
http://www.mt-propeller.com/index.htm

Click to expand...

Rob,

What is the exact pitch on your RV4 prop? I need to compared it with what I have as I have TOO MUCH pitch!

Nice prop but mine is the wrong pitch for my plane. Awaiting response from Doug.

James

I heard Catto is moving his prop operation overseas, he will no longer be making props but will be supervising overseas production.
Tom
RV3
Catto 2 blade cutomer