Catto vs Sensenich or Hartzell?

[13brv3]

Greetings,

I've got an RV-8 QB on the way, and am starting to make decisions on the engine and prop. I built an RV-8 previously, with an O-360 and Sensenich aluminum prop, and had plenty of chances to compare it to my friends O-360/Hartzell RV-8. The Sensenich was just a few mph faster in top end, but of course his Hartzell outclimbed me by a few hundred fpm.

This time around, I had planned to go the CS route, but I've never flown a CS prop, and would really prefer the simplicity of fixed pitch. While the Senenich performed well, it was almost as heavy as the Hartzell (40lb vs 58lb).

I'm also looking at the Catto prop, since I've heard so many good things about it. Is it really only 18 lbs? That would be a huge savings (weight and money) over the Hartzell.

Now for the actual question- How does the performance of the Catto prop compare to either the Sensenich, or the Hartzell? Can anyone point me to a comparison test?

Thanks,
Rusty

[sprucemoose]

I have a 3-blade Catto on my O-360 RV-6. It does indeed weigh exactly 18 lbs. It also is very smooth compared to a metal prop. I can't point you to any scientific performance testing, but I can tell you that it performs favorably against the Sensenich prop, based on my own informal testing (ie- racing Sensenich guys.)

[gmcjetpilot]

As an observer of the obvious: D

You can throw out the Hartzell because that goes under the C/S vs. fixed pitch prop debate. It is an animal of a different fur.

I have a Hartzell by the way on my last RV and current RV and love it. The blended airfoil is the best performance you can get, and it has been documented (in the RVator). If you have an engine that can run a Hyd prop, at approx $5500 plus gov it is a bargain in my opinion. C/S props provide the best overall performance and efficiency (gas mileage, less noise with lower cruise RPM and wear and tear on engine). Not to mention doing aerobatics is a joy with no throttle jockeying.

If you don't want, need or can use a C/S prop, for what ever the reason, cost or engine capability, there are two other choices, both fixed, one is metal and the other is wood or wood with fiberglass skin (Catto).

The metal Sensenich is a known quantity. It has known performance and known material properties (aluminum). For the O-360, the Sensenich has documented known performance. The nice thing is the prop was designed for RV's and is well tested on RV's. You can't get much more durable and low maintenance than a fixed aluminum prop. We build aluminum RV's for are reason and not Glasair's, right.


Catto, I have heard good things, people like them and they are sexy. I think the painted finish attracts people, however you can get a metal prop custom painted. Custom Prop Paint (click the aircraft links on the bottom of page)


The debate now becomes wood vs. metal. Both props have pros and cons. I guess it's a matter of choice at this point. Things I do know are metal will be less maintenance, hands down. Minor repair like a rock ding will be less with metal. The only negative I have heard of regarding Catto, is one guy in another forum had one break or throw a piece off. To be fair he was racing at Reno or something like that in a formula racer, but the wood failed, which is always a concern. Let's face it, wood is a natural material and subject to small imperfections. Go to your favorite home-supply mega-store and look for good pieces of wood. It's hard to fine sometimes. Now add the fiberglass wrap and bonded erosion shield and you have a complex built-up bonded structure. Any bonded structure is very process depended, meaning any small variation or error in making it can cause serious defects.

Wood will be hands down lighter and feel a little smoother because wood dampens vibration very well. For solid wood props with no cover the biggest Con in my opinion is constant checking and re-torquing of the prop bolts. Wood expands and contracts with moisture content, which it will do year round with the sessions. The Catto fiberglass wood wrapped blades may or may not be subject to this also, but I don't know? They have an aluminum plate bonded in the hub area, so this may help.

Sensenich performance is well known, and a metal prop should out perform a wood prop. Why? Well metal prop blades can be made thinner than wood. It would be interesting to have a fly off between the Catto and Sensenich, where the props where switched out on one or two planes. The Sensenich was flown against several C/S props and did very well as shown in the RVator. There are no well documented fly off between a Sensenich and Catto I know of. However I looked at their site and they note that the top 3 Biplanes at race had Catto props.

Why was they?re so many wood props in the 80's and early 90's. Well they?re where no fixed pitch metal props available, period. Using metal props for slow planes cut down and re-pitched was not a good thing and even tragic. Metal props unlike wood is made of a similar material as the crankshaft, metal. So harmonic vibration and fatigue is of concern. (Wood by the way has good fatigue life and will die from decay not fatigue like metal can.) To make sure it's not an issue, metal props need to be well engineered and tested, that requires complex equipment and analysis. Sensenich stepped up and tested their line of RV metal props, which in a way made wood props obsolete for a large population of average RV builders. The price is also very good. A well-tested metal prop is very safe and fatigue not an issue. An experimental un-test metal prop is dangerous. Wood is so forgiving you can whittle a wood prop out and not worry about it, however there have been some wood prop experiments gone wrong in the past. The most popular wood props have a good safe record overall. However things like leading edge erosion strips do and have come off wood props, and it is not uncommon. If this happens it can shake the plane quite vigorously. I think the Catto does not use bonded leading edge strips like may wood or wood/fiberglass props do. This is a good thing.

Wood still has appeal, but it is a special appeal in the RV world. Many homebuilt planes are better suited for the Catto because frankly Sensenich does not make a prop for their application (Long-EZ). Also some homebuilts are very weight sensitive, which the RV is not. With the use of light alternators, starters and batteries and placing equipment aft when given the choice, the extra weight is not an issue for the RV. I know the RV-7 needs weight on the nose to allow full baggage and remain in the aft CG limit. Weight on the nose is good for the dash 7.

In the end it depends on how the company will support you. Hartzell will be there but will cost the most. In return have the best overall performance and efficiency (fuel economy), and that is not a debate but fact. To get this will cost weight on the nose (which is need on some RV's) and money. The Sensenich will be there down the road, and like Hartzell has tested their product on RV's and supports RV's specifically. The Sench is a known quantity and a unique feature wood does not have. If you make your plane a little faster with some drag reduction, like a fairing mod or the like, you can re-pitched the Sensenich fixed pitch prop. Wood has the advantage of smoother operation and lightweight. I would also add lower cost to the plus column of wood props, but the hybrid wood/composite props are not cheap and actually cost almost the same a metal props.

Also you have to think of maintenance. If there is some small damage who will repair it? Hartzell and Sensenich can be repaired at any prop shop. The custom wood prop will most likely need to be shipped to the manufacture. The last point is a toss up. Wood props tend to be totaled when they are hit on the ground, while metal may be able to be repaired. However if the "strike" is bad the wood prop will break and save the engine while a metal prop may cause damage to the engine crank in a hard strike condition. This of course is not something you want to happen in any form, but it is a small factor. Last and may be most important is what engine do you have (solid/hollow crank) and how much money do you have to spend on it.

George

[13brv3]

Thanks for the comments. George, perhaps yours should be the propeller FAQ

What I'm hearing is that the Catto is probably equal, or better to the Senensich in performance, though I know that it's not as durable.

Some composite prop makers claim a certain amount of "near constant speed" behavior, so comparison to the Hartzell is not completely off the wall. I realize they can't be equal to a CS prop, but if they could close the performance gap some, it would help justify a fixed pitch prop.

I'll almost certainly go with the blended airfoil Hartzell, but figure I should explore all the options.

Thanks,
Rusty

[gmcjetpilot]

Originally Posted by 13brv3

Thanks for the comments. George, perhaps yours should be the propeller FAQ

What I'm hearing is that the Catto is probably equal, or better to the Senensich in performance, though I know that it's not as durable.

Some composite prop makers claim a certain amount of "near constant speed" behavior ...

I'll almost certainly go with the blended airfoil Hartzell, but figure I should explore all the options. Thanks, Rusty

Thanks Rusty.

Yes I heard there might be some give or flex with wood props? I don't know. I do know 10-15 years ago someone made a radically swept Scimitar/helical propeller (scimitar = curved leading edge). The idea was under load (takeoff) the prop twists flatter for higher RPM. As you speed up the disk load is less and the prop twists back, making it coarser, keeping RPM lower. Well the radical design did not make it, because they broke (a lot). However mild scimitar shapes are popular and even Hartzell and McCauley make scimitar shaped blades for some of their C/S models. Until those who claim this quantify it, measure it and document it, it's just a possible theory or just a sales pitch. If wood props flex I would think the Catto would flex much less or at all with the fiberglass "structural" cover. In other words it is very stiff. How it performs is more important, along with the other important issues.

As far as claims of performance, unless you do a controlled flight test I tend not to believe the people who sell them 100%. Also even well minded builders tend to be proud of their plane and prop, so they may not be a source of unbiased info. However I hear folks are happy with the Catto's performance. The biggest Gotch-U with reported fixed pitch props is RPM. Many fixed pitch props, regardless of brand, allow you to Rev the engine quite a bit over 2,700, which makes your plane faster. For every 100-RPM you get an extra 3-5 HP. It is not uncommon to have guy's "racing" turn more RPM flat out WOT. The Reno guys are turning the little Continental O-200's up and over 4000 RPM. This of course is not practical normal operations, at least if you want to make TBO. So when there is racing ask what the RPM is. When I raced my RV-4 I tweaked my gov to allow 2800 RPM. The Hartzell is rated to 2,900 RPM. Lycoming (O-360A) is red lined at 2,700, but 100 over is not too critical. Lycoming talks about overspeed (over revving) in SB 369J. Under 5% or 2835 RPM no action is taken, but STOP THAT. Between 5%-10% requires immediate required inspections that are quite involved (Borescope). Over 10% (2970 RPM) Lycoming wants a tear down! DISCLAIMER, I do not recommend exceeding any limitations. Just keep these numbers in mind.

You do have to check all the avenues. Money is important and sometimes the choice is made for you when a good engine comes along and does not have c/s prop capability. The choice is made in part for you. Many don't relies or think of this, you are not married to your prop or engine. You can always sell your old FWF and upgrade. Changing a prop and/or engine down the road is not hard. Later when you have the money for a C/S prop and an engine that can support one, if need be, you can get it. In the mean time you are flying. That is what I think Doug Reeves did.

May I suggest if you have the money and desire for a C/S prop you go that way if at all possible for the start. It is easier to build it the way you want the first time. Even if you opt for a fixed prop at first, if you have the option to buy an engine with or with out c/s prop capability, I suggest you pay the premium and get the C/S prop capable, even if you do not use it at first. Conversion to c/s in the future would than be easy. Also resale would be higher.

Bottom line, get the engine and prop you want. If not get "A" prop and engine and go flying. George

[sprucemoose]

Originally Posted by gmcjetpilot

Bottom line, get the engine and prop you want. If not get "A" prop and engine and go flying. George

Probably the best advice you've ever given George. Would you rather dream about your dream plane, or fly one which is pretty **** close? I too had my heart set on a c/s prop, and in fact had the governor bought and installed. After a long heart to heart with my checkbook, I sold the governor, bought a second hand wood prop for $500, and happily flew it. It would have set me back at least a year, or more, to save up the money for a c/s. I did a lot of great flying in that year with my $500 wood prop.

[gmcjetpilot]

Originally Posted by sprucemoose

After a long heart to heart with my checkbook, I sold the governor, bought a second hand wood prop for $500, and happily flew it. It would have set me back at least a year, or more, to save up the money for a c/s. I did a lot of great flying in that year with my $500 wood prop.

Awesome, cool... Love that. Better flying than dreaming about flying. Folks, a 150HP fixed wood prop RV is a BLAST to fly. You don't NEED more HP or all the bells-N-whistles and EFIS stuff to fly. Go get'em. G

[13brv3]

Originally Posted by gmcjetpilot

Bottom line, get the engine and prop you want. If not get "A" prop and engine and go flying. George

Thanks George,

Now let's see:

Want = IO-390 with Hatzell blended and inverted oil.
Need = O-360 with Catto

I am leaning toward a new engine, and will certainly get it CS enabled, since that's not really much extra money at all. Most likely, I'll end up with an O-360, and Hartzell blended 74" prop.

Cheers,
Rusty

[gmcjetpilot]

Originally Posted by 13brv3

Most likely, I'll end up with an O-360, and Hartzell blended 74" prop. Cheers, Rusty

That sounds like a plan and lot's-A-bang for the buck's. Funny, That is almost exactly what I have, O-360A1A/HC-C2YK. I wanted the blended prop but got a steal on a rebuilt C2YK/7666. I also lucked out on a OH'ed woodward Gov for $400. Yes I am a picky cheepskate. G

[osxuser]

I still recommend going with a parallel valve FI engine over the straight O-360 A1A. BUT this is strictly from the viewpoint of running LOP operations to save fuel .