Catto Vs Borer floatplane

I ran a 8436 with 10:1's in a 320. Did good, until i had engine probs

Food for thought

I get it, Catto being a wood prop is lighter than the McCauley Borer which is aluminum. Less weight up front is good for two reasons. A lighter basic airframe weight and a CG which is further back. The Catto likely has better aerodynamics than the McCauley giving it the edge on performance.

A four cylinder large bore engine has power pulses 180 degrees apart which create a certain amount of stress on the rotating components. This is improved when the engine has six cylinders where the power impulses are reduced to 120 degrees separation. Have any of you flown behind the Lycoming IO-720 eight cylinder engine? It is smooooooooth.

Now in order to up your power a higher compression set of pistons is installed. This would automatically increase the torsion stresses on the components. Engines which do not have propellers have flywheels to absorb these stresses and higher impulses which helps the engine rotate to the next compression stroke in a smooth manner. Basically the bigger the fly wheel the smoother the idle. The Enstrom helicopter which I used to fly had no propeller and only a light cooling fan attached to the engine. It started roughly often kicking back (sometimes breaking starter housings) and idled at a very high rpm in order to keep running.

These higher stresses and impulses generated by the high compression pistons will change the natural resonance frequency of the engine and thus the entire airplane. This makes me wonder if there may be cracks forming somewhere, anywhere in the entire airplane because of the higher compression pistons and lighter prop combination?

Can anyone here answer these questions? Do more screws start falling out of the wraparound cowl or elsewhere?

In my opinion one must think of all of the possible consequences before making multiple modifications which in their mind is an improvement. Uneducated modifications can create troubles where you do not imagine. Just because any and all modifications may give an improvement, when they are combined you may get a result which turns around to bite you.

Just something for all of you to keep in mind when you make a change to your plane. Just because it works for one airplane doesn't mean that it will work on the next airplane. Think your ideas through. Look for the results of what might happen. Keep an open mind to the potential issues.

Well said. I have both a Catto and a Mac(Borer). My Cub has a 150/O-320. The Mac has a noticeably smoother idle. At cruise, both props are very smooth and there is no discernible difference, but I also realize that the harmonic anomalies that cause things to crack/break are almost never felt. These are torsional issues that happen in the plane of rotation, not balance issues. All that being said, I really like the Catto and am not worried about it on my little 7:1 motor. I think a 10:1 engine would be cause for concern with such little flywheel. Now on to my spin on the Catto, from a performance standpoint.

My Catto is an 82-39. My Borer is an 82-42. From a performance standpoint they are two peas in a pod. They both cruise 92@ 2400rpm. They both run out at 103@2750rpm. They both produced nearly identical time to climb numbers. I did 3 runs each from brake release to 1000' and the average time came out to within .45 sec. Both produced times of right around 1:05 (but I hate to tell you the Mac won). My biggest reason for the Catto was weight. My 12 has the long mount and I wanted to optimize my CG. I already had a Niagara cooler, Skytec started and B&C alternator. My empty CG is now in the upper 13's and I'm really happy with how it flys/handles.
I have been reading some pretty incredible things about the Catto in this thread that may be just a wee bit exaggerated. Its a great prop, but it won't take 20lb. off the nose (more like 16 which is still great) and it won't cruise faster AND climb better - aint happenin'. Well, now I've done it --- here it comes!!

P.S. - I do agree with the Catto having better aerodynamics because it does the same job with 3 inches less mechanical pitch. It also statics about 40 rpm lower but has the same run-out speed and rpm. It would appear to be grabbing more air at lower rpm (static) but then the Mac catches up as they go through translation.

For me the difference from a McCauley to Catto was 11lbs. Catto offered the option of trying several options to see what was best suited for my engine and my objective, including one no charge re-pitch if I choose. The performance difference would be comparing apples to oranges.

as far as harmonics the catto being a wood core prop will absorb the vibrations, where a metal prop will transfer them all the way to the tip. Their have been quiet a few cases of long metal props breaking( usually about 19" from the tip because of high comp pistons ect in 4 cyl engines. the worst culprits are the 0360's. shortly, like within 1/2 sec or so the engine tears off of the firewall from the imbalance. this same effect was seen in the canto's but only resulted in the leading edge sheath cracking and since then more carbon fibre was added to extinguish the problem. This is why the borer prop for an 0360 is so heavy but even at that i do believe all the vib testing was done with low comp pistons.

You guys continue to refer to a Catto prop as wood, even when Catto's label says otherwise. So here are a few questions. My Whirl Wind blades are foam core. Does that make it a foam prop? Skywagon's Whirl Wind blades are hollow. What do you call that? An air prop? How do the foam and air props handle vibration? I only know of one bad pirep for a Whirl Wind and that was on an aerobatic plane spinning 3300 rpm. No other negative reports that I've heard. I'm just curious because the truth is that I don't know diddley about props other than some go better than others. Somebody edyoukate me, please?

FWIW most of the EX high compression engines I looked at (360ci and above) use conterbalanced cranks. If that matters in the vibration discussion.

cub12,
You are correct in all that you said as far as the harmonics between the prop and the engine reacting together. The question is how does that power plant combination react with the entire air-frame?

stewart,
You are correct that Catto's data plate does not mention wood. The Catto is made up of multiple layers of wood topped with layers of glass and carbon fiber. The load paths and stresses are distributed among all of the layers.
Your Whirlwind has the structural stresses incorporated in the carbon layers which are in turn stabilized (stiffened) by the foam core.
My Whirlwind has the structural stresses incorporated in the carbon layers with a hollow core. The blade angles do not change during flight other than normal flexing.

While I'm not certain, I suspect that since your prop is constantly changing pitch (constant speed) while in use that there are variable loads which must be dampened. Thus the addition of the stabilizing non structural core.

There are reasons for calling the Catto "wood" which are not relevant to this discussion. If you wish to send me a PM I will be happy to explain my reason.

I don't know squat about load paths and tensile strength and elongation and yield. I am pretty sure a Catto prop isn't a wood prop, though.

I don't have any criticism of what other guys use. I chose what I have because I talked to guys about their experiences and dialed in on what was important to me. Community and honest pireps are a powerful tool.

we can call a catto wood or wood core, my point is that the wood is very effective at dealing with vibration over metal. As to what goes through the airframe that would depend on what type of engine mount an rubbers were being used. I have seen props go out of balance in flight to the point that the horizontal stab is going up and down 6". In fact the company our family used to own ran a fleet of aircraft using Mac's, we were seeing a lot of engine gearbox damage from prop vibration( yes i know not engine vibration going down prop but prop vibration going through the engine and airframe) this would transfer through the whole aircraft. So we started an MT program ( again a wood prop covered with fibreglass) and it saved huge money in engine o/h costs, as for the airframe and avionics we knew it was saving money and a lot safer but it's hard to put a $ figure to it. With the Mac's the vibration was a hub issue not necessarily because it was a metal prop but we are taking vibration here so it somewhat applies

This discussion is like herding cats. I'll leave y'all to it. Have a nice day.

stewartb said:

This discussion is like herding cats. I'll leave y'all to it. Have a nice day.

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Some just don't like being corralled.;-)

For what it is worth:
I was visiting with a fellow last summer at Lake Hood who was doing some flight testing with his 180+ HP cub. He does various testing for STC purposes so his cub was in a temporary "experimental" category for these tests. He was currently on floats so I was quizzing him about various changes such as props. He said that he had run a Catto prop on this cub for awhile but wound up removing it. It was not that it didn't perform good, but that he got tired of having the engine "kick back" during startup which it did not do with the big metal MaCulley prop. He said that the flywheel effect of the big Mac prevented this. He had to replace two starters do to extensive damage. The other dis-like was that when shutting down; the engine "slammed" to a halt. With the Mac and its flywheel effect shutdown was more normal.

From the Catto website------Catto Propellers are a fully encapsulated composite propeller protecting it from all the elements. A laminated wood core is CNC machined for precision and quality control, followed by glass/carbon fiber composite for structural integrity.

The other dis-like was that when shutting down; the engine "slammed" to a halt. With the Mac and its flywheel effect shutdown was more normal.

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Time will tell if that is like a sudden stop but my 180 Cessna with MT has been shut down many times and still seems to run okay. When I shut my 150 hp PA12 down the Sensenich prop usually backs up against compression so that seems kind of abrupt too.

cubpilot2 said:

The other dis-like was that when shutting down; the engine "slammed" to a halt. With the Mac and its flywheel effect shutdown was more normal.

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My Whirlwind hollow carbon blades on an IO-360 stops quickly also. But I would not call it "slammed" to a halt. Quick but smooth, yes. I attribute this to the electronic ignition. Mixture is pulled at idle with no O-360 shake. The lightweight blades and lack of flywheel effect is apparent.

cubpilot2 said:

For what it is worth:
I was visiting with a fellow last summer at Lake Hood who was doing some flight testing with his 180+ HP cub. He does various testing for STC purposes so his cub was in a temporary "experimental" category for these tests. He was currently on floats so I was quizzing him about various changes such as props. He said that he had run a Catto prop on this cub for awhile but wound up removing it. It was not that it didn't perform good, but that he got tired of having the engine "kick back" during startup which it did not do with the big metal MaCulley prop. He said that the flywheel effect of the big Mac prevented this. He had to replace two starters do to extensive damage. The other dis-like was that when shutting down; the engine "slammed" to a halt. With the Mac and its flywheel effect shutdown was more normal.

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I have had to change a couple of starters on Carbon Cubs because the engine kicked back at starting. The lighter of the skytech starters breaks pretty easy. Never had more than a shear pin break with metal props.

In the case of kickback, I have to wonder how many aircraft are being inadvertently started on both mags (assuming only ONE impulse). I've seen at least a couple of Bendix type switches that should've had the right mag shunt, that didn't. I've also seen a LOT of people hop in a plane with individual switches and flip them both on prior to starting.

PerryB said:

In the case of kickback, I have to wonder how many aircraft are being inadvertently started on both mags (assuming only ONE impulse). I've seen at least a couple of Bendix type switches that should've had the right mag shunt, that didn't. I've also seen a LOT of people hop in a plane with individual switches and flip them both on prior to starting.

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all the Cessnas that I work on have impulse couplings in both bags. Since they start with a key, they are both going to fire. I can't recall seeing anything in Pipers POH that suggests you start on one mag? Only one mag has an impulse on the 0-360s I work on in Pipers, however. As for the Carbon cubs, they have electronic ignition and both plugs are hot.

Den said:

Since they start with a key, they are both going to fire. As for the Carbon cubs, they have electronic ignition and both plugs are hot.

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??????

The key switch (which I referred to as Bendix type) has a ground while cranking terminal specifically for shunting out a non-impulse mag while cranking, so its not just automatically firing on both while cranking. If you have impulses in both mags then you leave the ground shunt out. In the case of individual switches you should only start on the impulse, otherwise you have one side trying to fire at +25° and a kickback is likely. The impulse side fires at zero.

I'd bet you a nickle the electronic systems have a start/retard mode, but I'm talking mags here. You kind of made my point for me. A lot of people don't know about only starting on the impulse. If the aircraft has duals all the better, but I know most Lyc's don't.

Den said:

Since they start with a key, they are both going to fire.

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There is a cut out in the key switch that cuts out the non-impulse magneto when starting.

Electronic ignition doesn't have static timing.

I started my Cub on both for a year before I knew not to. It's not in the POH or the Lycoming book.

Den said:

I have had to change a couple of starters on Carbon Cubs because the engine kicked back at starting. The lighter of the skytech starters breaks pretty easy. Never had more than a shear pin break with metal props.

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Den said:

As for the Carbon cubs, they have electronic ignition and both plugs are hot.

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Den,
Is there a possibility that the electronic ignition is not retarding the spark during the starting phase? Or that the timing is set incorrectly and that the retard position is still too far advanced? Electronic ignitions should not kick back during starting.

Eddie Foy said:

Electronic ignition doesn't have static timing.

I started my Cub on both for a year before I knew not to. It's not in the POH or the Lycoming book.

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Eddie that's one of those if we tell ya things... you just have to glean such knowledge by osmosis!

OLDCROWE said:

Eddie that's one of those if we tell ya things... you just have to glean such knowledge by osmosis!

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This whole Cub journey has had a lot of osmosis.

Den said:

all the Cessnas that I work on have impulse couplings in both bags. Since they start with a key, they are both going to fire. ....

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Generally speaking, in my experience Lycomings have one impulse coupling (usually on the LH mag) and Continentals have two.

skywagon8a said:

Den,
Is there a possibility that the electronic ignition is not retarding the spark during the starting phase? Or that the timing is set incorrectly and that the retard position is still too far advanced? Electronic ignitions should not kick back during starting.

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I don't know how the electronic retards the spark for starting. There is no way to control it as far as I can tell. Just a hall-effect sensor.

As far as the Cessnas. All the 172S that I have seen have identical mags on both sides. We have 125 of them at least; 20-25 in Mesa alone. The Seminoles have O-360 L2A and they use 4 different mags. PITA to stock 4 different mags for one airplane and all the rest use only one mag.


If there isn't an impulse coupling on the non-retarded mag, why will it try to fire during starting? I have never seen an L2A kick back even with both mag switches turned on.

The impulse coupler does two things. Retards the timing and produces a hotter spark at low speed
That being said, a healthy mag will produce plenty of spark to fire an engine without an impulse. I had my left mag (the only impulse on mine) throw a fit a couple years ago. Since I have the Bendix switch with a ground shunt, I had to pull the P lead off the right mag to get it to start, which it did quite readily.

Den said:

I don't know how the electronic retards the spark for starting. There is no way to control it as far as I can tell. Just a hall-effect sensor.

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My only electronic ignition experience in airplanes is with the P-mag. The P-mags are timed to top dead center. After that they automatically vary the timing as appropriate for the condition. Perhaps the system in the planes which you are working on was not timed correctly upon initial installation? One of the big advantages of electronic ignitions is to provide a more automotive like start without kickback.

Den said:

I don't know how the electronic retards the spark for starting. There is no way to control it as far as I can tell. Just a hall-effect sensor.

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There's a couple of ways to do it, sense the starter being engaged and retard timing, sense very low RPM and retard timing, etc.