We have just managed to get our zenith 801 up and flying... it has an mt 3 blade, not good thrust at 2800 rpm... only 500 fpm with 220hp franklin. Pretty sad actually.

What recommendations do you guys have for a two blade ground adjustable composite prop.

I went with the Sensenich GA prop. It has 6 different pitches that can be adjusted in the field in under 15 minutes.

rsrguy3 wrote:We have just managed to get our zenith 801 up and flying... it has an mt 3 blade, not good thrust at 2700 rpm... only 500 fpm with 220hp franklin. Pretty sad actually.

What recommendations do you guys have for a two blade ground adjustable composite prop.

Seems like something is wrong with it. Should climb at at least twice that with practically any propeller.

MTs aren't perfect, but they typically perform quite well.

I would tend to agree with you about the mt... in this case it's a three blade and it just isn't climbing at full rpm. 2 blades are quite a bit more efficient in any case, I'm pretty sure we'll loose ground clearance though.. maybe need to build a taller fork and go with a taller tire.

What ground adjustable props does Zenith recommend? Unfortunately I’m not very familiar with them, not much help there.

What was the manifold pressure at wide open throttle and 2700rpm? If it wasn’t up close to 26” plus at sea level there’s probably something wrong with your prop governor.

If you’re not getting climb performance out of a 3 blade MT on a 220hp engine I’d be very surprised if you end up being satisfied with a fixed pitch 2 blade. Of course I’m wrong all the time though- ymmv.

What zenith says is irrelevant it's a 220 frank. We're maxing rpm and no climb with the mt. It's just not a large enough diameter to do the job plus.... three blade.

rsrguy3 wrote:What zenith says is irrelevant it's a 220 frank. We're maxing rpm and no climb with the mt. It's just not a large enough diameter to do the job plus.... three blade.

I'll repeat....what was the manifold pressure during takeoff? Sounds like maybe the engine isn't making power.....?

MTV

rsrguy3 wrote:I would tend to agree with you about the mt... in this case it's a three blade and it just isn't climbing at full rpm. 2 blades are quite a bit more efficient in any case, I'm pretty sure we'll loose ground clearance though.. maybe need to build a taller fork and go with a taller tire.

I seriously doubt that the prop efficiency delta between two and three blade props is causing your 801 to experience a max climb rate of 500 fpm.

Three blades are typically a little slower than two blades in cruise due to slightly reduced prop efficiency, but a three blade will generally produce more thrust during takeoff and climb when the engine is making rated power.

You can turn 2700 rpm at partial power spinning a constant speed propeller. I'd make sure that you are making rated power before searching for a new propeller.

Like others have asked, what MP are you seeing?

What is the full complete model number of the MT prop? it begins with MTV-##/###-##

The E-124 MT Owner manual tells how to set the prop pitch stops for proper RPM and then how to match your governor to the prop. Try that. We have seen many MT props on Franklin powered 170's and they work great.

John

john54724 wrote: We have seen many MT props on Franklin powered 170's and they work great.

Field approved installations? When I was prop shopping for my Franklin powered Maule, I was told by MT that they didn't have any approved props for the Franklin. I would've liked to have been able to take more weight off the nose.

OP: are you currently running a constant speed MT? Are you able to get full RPM (2800)?

24 inches at 4200 field elevation,
2800 rpm..
the motors fine and making gobs of power, it only has 10 hrs since out of the factory crate.
Not making metal, not using oil.

1:1 Scale wrote:

john54724 wrote:

OP: are you currently running a constant speed MT? Are you able to get full RPM (2800)?

Yup

Field approval isn't relevant. It's a Zenith 801

Factory crate? Has it been in there for 50 yrs?

There is something seriously wrong with that installation, and if it’s the prop, it might be because it wasn’t set up right. MT props pull hard….I don’t care what engine they’re on. I’d get a very knowledgeable mechanic to go through the thing. You can change props, but I’m betting you’ll see the same result.

MTV

Ross4289 wrote:Factory crate? Has it been in there for 50 yrs?

New pzl frank.. the plane has spent no time flying since it was completed. Maybe 2 flight hours when we trailered it home.

rsrguy3 wrote:

1:1 Scale wrote:

john54724 wrote:

OP: are you currently running a constant speed MT? Are you able to get full RPM (2800)?

Yup

Field approval isn't relevant. It's a Zenith 801

I was asking the other poster about MT's on the Franklin powered Cessna 170's he referenced.

Hi rsrguy3,

Lots of experienced folks here trying to help solve the mystery, which of course is not what you were asking for. It seems by your initial post you're committed to moving on to a fixed pitch (albeit adjustable) prop. There's certainly nothing wrong with that, specially if the name of the game is short leashed stol ops. The bc world is chock full of 75 mph cub types and most people seem to agree that low and slow need not be mutually exclusive.

Never the less, I *think* it may behoove you to get to the bottom of why the 500 fpm climb (and perhaps you have and simply haven't shed light on it) with the MT prop.

My brain works very Forresst Gumpy, and if it were me that sequence would go like this;

john54724 wrote:What is the full complete model number of the MT prop? it begins with MTV-##/###-##

John

This man will definitively know whether or not this prop engine combo are a match. He also happens to be in sales, so having a combination that does not match out there will not be in his best interest, so there is no reason for him to try and convince you otherwise.

Furthere more, he has offered information on how to get it turning right.

Next I'd verify this;

Scolopax wrote:You can turn 2700 rpm at partial power spinning a constant speed propeller. And this....
Like others have asked, what MP are you seeing?

and maybe you've done all this and it isn't reflected in your post, but I'd triple check the gauges before I abandoned a prop

Next I'd verify the engine thrust line, wing AOI, and rigging all make sense. FWIW, at work we have 4 identical airframes (up until the firewall fwd) powered by 4 engines of equal horsepower. The firewall forwards on these have 3 different engines mounts, and the performance difference from the poorest flyer to the best flyer is astonishing.

Lastly, I'd try and lean less on 'old wives tales', 'rules of thumb', and conjecture, and focus on fact and data that pertains to your specific airplane.

What I'm getting at is this comment;

rsrguy3 wrote: 2 blades are quite a bit more efficient in any case...

Firstly in my experience going from less to more blades on several airframes, As Scolo posted, the delta just isn't there to cause what you're seeing. More importantly, when engineering types use that quote, they are actually referring to a propellors efficiency, not a prop / engine / airframe efficiency, or lack there of which is more accurately what you are experiencing. let me say it this way, if you throw a 100% efficient single blade prop on there (yes I know even a 1 blade wouldn't be 100% efficient) and that solo blade made 75lbs of thrust
and then you tried a 45% efficient 10 blade prop that made 500 lbs. of thrust, all else being equal would you still want the 1 blade in the name of efficiency? I mean air isn't something we are paying for, this isn't like running a Rotax so you can save a bit of fuel.
I'm an average redneck American, I really don't give a rip how efficient my prop is, I want to know which one makes the whole package move best. And number of blades alone is almost irrelevant. Look at all the sky wagons out there that are running 3 blades, do you really think they are performing that much poorer than a 2 blade in any regime? Done correctly, most are performing better in most if not all regimes. The single deviation from this that I can think of is the uber light stol contest cub type. Because in that world, a longer prop is getting more of the actual wing blanketed in moving air (free airspeed) before the thing even leaves the hole. And of course with three blades (all else being equal) you're frequently shorter in dia.

Anyway, the reason for all this dribble that you did not ask for is because it sure would be a shame to go through all the hoop jumping and expense to have a lesser performing machine...

3 blades and six cylinder engines go hand in hand in the balancing department, and a composite one makes for a pretty tough to beat combination. I'd try looking at things from a different perspective for a day.

Take care, Rob