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Thread: C-180: MT vs Mac 401 Props

  1. #41
    Rob's Avatar
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    Quote Originally Posted by JohnnyR View Post
    Just curious if folks are still sold on the 3-blade MT performing best on a PPonk'd 180 vs. the 2-blade.

    We are spooling up for our engine switch from a tired old 470R to a new Ly-Con PPonk (Alaska engine deal fell through) and I'm musing on whether it's worth trading in or selling our current 2-blade MT prop.
    Thanks,
    Johnny
    Somebody on this site once correctly posted that the only reason we build better performing engines, is to be able to turn more propellor. Given that, define what part of performance you are trying to enhance, and your answer will be easy.

    The only three areas the 2 blade MT propellor out shines the 3 blade MT, are cost, speed and weight. Since the weight part of the propellor isn't effected by engine choice, then it can be concluded that the only reason to keep your two blade MT, would be to save a buck, or go faster (+/- 5 MPH)

    Comparing any other 2 blade to the MT 3 blade, or any other 3 blade to the MT 2 blade muddies the water, and only testing on your specific engine/airframe will yield meaningful results.

    Take care, Rob

  2. #42

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    My goal is shorter take-offs while hauling heavy loads from off-airport areas and high DA mountain strips without going to a different airframe than my 180. I don't want to spend over $50K for engine + install (not including new engine mount, exhaust & baffling).

    The PPonk we are planning to put in will have 7.5:1 pistons and LyCon's porting/flow balancing of cylinders. I'm expecting about 285hp.

    I've read your previous posts on the issue. MT's North America reps (John & Larry @ Flight Resources) have repeatedly stated that the PPonk doesn't effectively put out enough to warrant the 3-blade, citing negligible difference in performance with the penalty of more weight.

    You and Kevin (AKTahoe) state otherwise.

    How much HP is your engine producing, Rob? Did your before/after tests decisively confirm or refute what Flight Resources reports?

    Thanks,
    Johnny





    Quote Originally Posted by Rob View Post
    Somebody on this site once correctly posted that the only reason we build better performing engines, is to be able to turn more propellor. Given that, define what part of performance you are trying to enhance, and your answer will be easy.

    The only three areas the 2 blade MT propellor out shines the 3 blade MT, are cost, speed and weight. Since the weight part of the propellor isn't effected by engine choice, then it can be concluded that the only reason to keep your two blade MT, would be to save a buck, or go faster (+/- 5 MPH)

    Comparing any other 2 blade to the MT 3 blade, or any other 3 blade to the MT 2 blade muddies the water, and only testing on your specific engine/airframe will yield meaningful results.

    Take care, Rob

  3. #43
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    Quote Originally Posted by 46 Cub View Post
    I would keep the two-blade. I think the 3 blades are too much prop for these engines. If you would trade me a light two blade for my 3 blade (with approval) on my 0470-50 I would take it. Too much propeller area for a given amount of power will diminish performance because the blades have to go too flat to get performance (rpm) out of the engine. To get field approval I started with an 86" Mac. Next tbo run I had them cut it down to 84". The performance was better in every area. Next tbo, (the one I'm halfway through) I had them go to 82". Better takoff, better climb, better cruise speed.. I'll stop cutting there to preserve value (fits a 550-F 206) but the 0470-50 does not do it's best with the long 3 bladed prop... yep... my opinion...but formed by my experiences. FWIW only. I know everyone loves the long huge props.
    "

    Have you used both the MT 2 blade and MT 3 blade on your airplane?

    I have owned and used multiple copies of both. Fairly extensively, from Arizona to Alaska. My experience hasn't changed much from my original posts on this thread five years ago. That experience is pretty much opposite of yours.

    For my mission (getting a bigger load off the ground shorter and safer), there is no comparison between the two props. The 2 blade MT makes -50 powered 180 handle like a dream when light and playing. (best CG qualities of any prop I've had on it). But it simply runs out of poop to take advantage of the extra power the -50 makes. My opinion is that this prop (the 2 blade) is an outstanding match to the O-470 Skywagon. If it had a longer or more aggressive blade it would probably be perfect on a -50 powered 180, and as it is, it is an OK choice.

    With no load and 10 gallons of fuel they both leave the ground in short distances, too short to be concerned with the difference, probably in part due to how fast the little 2 blade spools up.

    At max gross weight the take off distance between the two is measured in hundreds of feet. Literally .... that is not insignificant.

    Take care, Rob

  4. #44
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    Quote Originally Posted by JohnnyR View Post

    How much HP is your engine producing, Rob? Did your before/after tests decisively confirm or refute what Flight Resources reports?

    Thanks,
    Johnny
    My engine was built by Steve Knopp and is running ported cylinders as well. I like to think Steve builds an excellent engine, but it is not likely to be anything more spectacular than yours. I have flown 2 Lycon built Pponks, near as I can tell, all 3 of these engines could be twins, triplets?

    The first time I did back to back flights with the MT's I only owned a 2 blade. It was convincing enough for me to immediately order the 3 blade even though John and Larry suggested it wasn't worth the extra money. I don't think they are wrong per se, and appreciate them trying to save a guy a buck. I simply think that tying the tail of an airplane to a fixed strain gauge bears little to no semblance of the actual mission I expect out of my airplane. Nor does them being in the drivers seat of the tied down airplane emulate my operation of the moving one.

    I prefer the flying qualities of the two blade, I prefer the cost of the two blade, and I prefer the sound of the two blade and have owned both at the same time. I suspected I would prefer the take off performance of the 3 blade, and arranged to test one. I would suggest if you are that much on the fence, you do the same. These are not nickel and dime items.

    Take care, Rob
    Thanks JohnnyR thanked for this post

  5. #45

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    Ya you are right Rob - I was steered wrong by the title of the thread. I have no personal experience with MT propellers. It was interesting to read your report regarding their comparison to each other.

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