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RV-4 Propeller Data?

ratc

Well Known Member
Hi,
Like a good number of builders I try and make one large purchase each year........... This year it's the prop! Although I've not purchased the engine I've settled on an 0-320 D1A (160HP) with Dual Pmags. At least the prop can be stored without fear of deterioration!
My propeller of choice is the Catto FP, speaking to Craig it seems that the the "standard" spec. for the -4 is a 70" diameter pitched at 70" for 160HP
(68" for the 150HP).

Clearly everything with a FP propeller is a compromise, what would be very useful to see are the data points other -4 operators have with 0-320
(160HP) engines and FP propeller combinations in terms of T/O, cruise and Max RPM's figures along with fuel burns if available.

What is the largest diameter propeller that has been used on the -4 turned by an 0-320? Not withstanding ground clearance and tip speeds I wonder what a 72" diameter propeller would produce!

My mission profile will be operating out of small grass strips (1200ft+), flying long (ecconomical) cross countries and doing gentlemans aerobatics/formation. Just what the -4 was designed for!


I have already gleaned a lot of useful information from Smokey Ray and I'm looking forward to seeing the data from his new project the RVX to which he is fitting a Craig Catto masterpiece.

As an aside, I've also asked my good friend Steve Sampson (who lives a little under 10 miles away) to provide me with the data he has for his similarly engined aircraft which is equipped with the MT C/S propeller.

I know that it's not the case of "one size fits all" but any data Vs propeller spec. would be gratefully received in order to make the big decision, thanks.
 
Hi Andy,

I have exchanged emails and phone calls with Steve. I suspect he would tell you to go CS. A fixed pitched prop is a compromise and your mission profile does not lend itself to choosing a FP propellor, no matter who makes it.

1200' runways, long economical cross countries, occasional aeros.

My advice to you, is if you need the above mission profile and are not prepared to compromise, is to bite the bullet and get an MT as Steve has done. You will have max power available when you want it and if you purchased an injected engine you will have the capability of going lean of peak, reliably, further enhancing your economy.

Take a look to at the source of major components. Catto Propeller, manufactured in the US. MT Propellers manufactured in Europe. Think about shipping costs and future repairs. Generally you will have to go to the US to source most of your components. If you choose an MT then you are taking a chunk out of the hassle factor of shipping and delays.

Saying this, build the plane you want to build.
 
Catto prop data?

A gentle push, just in case any 0-320 operators with Craig's propellers missed the thread!

Still looking for data, that is :-

Propeller Spec, Dia/Pitch.
Static (T/O) RPM at Full power (Density altitude would be useful).
Cruise RPM, Speed and Fuel Flow.

Anthony, I appreciate the advice but for the price difference between the FP propeller and the CS unit you can buy an awful lot of fuel, even at todays price!
Compromise will have to be made or perhaps slight variations in the way you operate with a FP propeller. I'm confident all of my requirements are achievable.
Besides, a light nosed -4 does allegedly fly a lot nicer!
 
Andy,

I have a light nose -4, Catto 68 x 74 two-blade, 4" Saber extension, O-320-D2J (160 hp). Generally cruise at 55-65%. Average fuel consumption 7.212 GPH over the past 128.4 hours of operation. Measured/corrected data: ROC @ 0' Density Altitude, 1500 lbs 1680 FPM. TAS: 7982' DA, 75% power 194 MPH; 8101' DA, 65% power 186; 8218' DA 55% power 178 MPH. Our plane has the old-style two-piece aluminum leg fairings, home-made uppers and old style wheel pants. I have collected data with an without fairings. Measured glide ratio: 13.2:1. Vx 81 MPH CAS at 1500 lbs; Vy 119 MPH CAS at 1500 lbs. Empty weight: 961.5. I don't have measured takeoff and landing performance data; but use a calculated distance (based on wing/power loading) of 850' to accellerate to lift off at nominal standard sea-level conditions (I live in Florida on the Gulf Coast) and add 500' per 1K above sea level as a ROT. I'm farily conservative and utilize a 2K minimum runway length. No suprise, but after extensive flight test, I've confirmed that the information/data provided for Van's prototype is right on the money. I chose a 68" diameter prop over the more popular 70" to accomodate the old, short-style gear on our plane. The prop is Craig's solution for "best all around performance." This prop produces 2200 RPM static, and has no problems reaching engine red line (2700 RPM). My power settings are determined utilizing a manifold pressure gauge and tach (Lycoming Curve 13381). Our prop is fitted with protective tape on outer 50% of span. Overall, I'm very happy with the engine propeller combination, and the only thing I would do differently is add Craig's new nickle leading edge protection.

Cheers,

Vac
 
Catto Prop data

Hi Vac,
Thank you for the data, just what I was looking for. It's quite impressive for a FP prop! I'm about 99% there with the Catto decision and your information confirms it.
 
Hi,
Like a good number of builders I try and make one large purchase each year........... This year it's the prop! Although I've not purchased the engine I've settled on an 0-320 D1A (160HP) with Dual Pmags. At least the prop can be stored without fear of deterioration!
My propeller of choice is the Catto FP, speaking to Craig it seems that the the "standard" spec. for the -4 is a 70" diameter pitched at 70" for 160HP
(68" for the 150HP).

Clearly everything with a FP propeller is a compromise, what would be very useful to see are the data points other -4 operators have with 0-320
(160HP) engines and FP propeller combinations in terms of T/O, cruise and Max RPM's figures along with fuel burns if available.

What is the largest diameter propeller that has been used on the -4 turned by an 0-320? Not withstanding ground clearance and tip speeds I wonder what a 72" diameter propeller would produce!

My mission profile will be operating out of small grass strips (1200ft+), flying long (ecconomical) cross countries and doing gentlemans aerobatics/formation. Just what the -4 was designed for!


I have already gleaned a lot of useful information from Smokey Ray and I'm looking forward to seeing the data from his new project the RVX to which he is fitting a Craig Catto masterpiece.

As an aside, I've also asked my good friend Steve Sampson (who lives a little under 10 miles away) to provide me with the data he has for his similarly engined aircraft which is equipped with the MT C/S propeller.

I know that it's not the case of "one size fits all" but any data Vs propeller spec. would be gratefully received in order to make the big decision, thanks.

A three-blade can be made smaller in diameter to reduce the high parasite drag at the tip to get better efficient operation, and it will have higher static thrust for better takeoff and climb.
 
I Understand the high speed benifit, but can you explain how a 3 or more blade makes more static thrust and low speed thrust?
 
I Understand the high speed benifit, but can you explain how a 3 or more blade makes more static thrust and low speed thrust?

Each blade intercepts a certain mass based upon the diameter. With more blades, you get more mass flow. Since efficiency is a result of the velocity of air which is thrown back, and since thrust is mass-flow times delta-v, the greater the mass flow, the less the delta-v for a given thrust, and the more efficient will be the prop. Now if you want to see how the Air Force and Navy are making use of that, do a search on the NP2000 propeller. You need to get some of the back issues of Contact! magazine where I explain pitch, planform, and multi-blade props, and the new issue due out soon will have an article on whether the inner few inches of the blade actually contributes lift/thrust. Most propeller articles will tell you no, in no uncertain terms. See for your self if that is true!
 
Catto Prop data?

Elippse, I can see the appeal of the 3 blade propeller in terms of reduced tip speeds and higher static thrust. But what about cruise efficiency?

Can you give a little more insight into your (shortly to be published) article regarding the "inner few inches"?

Being in the UK I'm not familiar with Contact! Magazine.

Using a 2 blade F/P propeller has all the appeal in terms of simplicity in both construction and operation. Clearly the drawbacks are that it can only be "perfect" for one phase of flight, if you choose one of the two extremes. The dilemma is to take the average and have a "good" all rounder, or bias the specification.

There is no doubt that 3 blade propellers look and perform very well but from a practicle viewpoint they are a nightmare to ship, work with during cowl removal or installation and you can never get a blade out of the way if hangar space is at a premium.

Having said all of that your inputs are invaluable. They concentrate the mind on areas that we have taken for granted or indeed misunderstood, thanks.
 
I've always been told to put a wood prop in the horizontal position when the plane is put away to help keep moisture from settling in the lower blade and throwing balance off. How does a three blade wood prop work out in that regard?
 
72" option

I'm working an RV-8 with only 150hp and Craig said, "I can run up to a 72" on the 150hp with the 2 bladed and this will give you better takeoff performance."

The 72" may or may not be an option on the -4 depending on ground clearance.
 
catto prop

I have an RV-4 160hp. Has a Catto 2 blade 68dia 76 pitch that I sent back as underpitched and Craig reworked it. ( I think he widened the cord )

It is still underpitched.

Sensi 70cm 81 pitch gave me 165kts TAS at 2600 rpm
Catto gives me 155 kts TAS at 2600 rpm

10 kt difference at each dens. alt tested. Sorry , no MP pressure gage.

The Catto clocked over 190 kts at less than full power ( at about standard atmosphere.)( more than 2700rpm)

Airplane weighs about 950 empty.

Chris M RACE 34
 
Say what you want from things you have heard, but the more blades you have of a similar planform outline, diameter, and pitch distribution, the more static thrust and the more rate of climb you will have. Science wins every time it's tried. Do an internet search on the 8-blade, narrow tip, NP2000 propeller that the Air force is trying on its C-130 and the Navy on its twin COD. The Air Force says that with the increased static and take-off thrust that it can probably do away with the Jato bottles that it sometimes has to use for short fields or overloads. We really need to get everybody into the new century on propeller technology and leave all of those old wives tales behind.
 
Catto Prop Data?

Elippse, I don't question the efficiency of a propeller with 3 (or more) blades in the static thrust/ROC phase of flight and clearly the 8-blade, narrow tip, NP2000 propeller is a great example. Since this is a C/S unit it can also be optimized for the cruise, my question relates to Fixed Pitch Propellers.
How efficient is a FP 3 (or more) blade propeller, pitched for optimum static thrust in cruise conditions?
I hope it's not just me that's getting an education out of this thread, hopefully we'll all get dragged into the 21st Century!
 
The thing that makes the difference is the amount of mass flow through the prop. More mass flow, more thrust, less delta-v, more efficiency. I designed Jim Smith's three-blade for best cruise. It had less static thrust beacause of the planform of my design, but higher ROC and cruise than his 68-72 Aymar DeMuth. At 8000' dalt the three-blade gave 190.5 mph GPS-determined TAS vs 186 mph for the A-D, even though the A-D was turning an average 100 rpm more. The speed increase was worth 7.5% and when you throw in the 2800 rpm/2700 rpm that gives an efficiency increase of 11.4%. Keep in mind that I said that multi-blade propellers with the same diameter, pitch distribution, and planform shape, that is, chord distribution but with reduced chords, will have more static thrust and ROC, whether FP or CS. BTW, with his new wingtips, Jim is doing 193.5 mph at 8000'dalt! You really need to read the articles I have written in Contact! magazine that go discuss planform, pitch, and multi-blades. I think you will learn a lot from them.
 
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