Three-Blade Mooney Props

[Hank]

There has been some discussion on the forum lately that I can't find [granted, it may have been on one of the MAPA mailing lists] about 3-blade props and whether they are the same or shorter than the 2-blade models.

I'm in annual right now, and I took a ruler to my prop while the spinner is off. Granted, it's a ruler, and I had to measure the diameter across the middle, so allow a little tolerance both for the squint factor there and for general measurement error everywhere. There may be a little additional induced error because I left the paper in the hangar, but I still came pretty close with this re-creation. See the picture below for details.

Pretty much comes to 74" when measured to 1/8" accuracy. The center is 5¾" in diameter, more or less.

So we have 32¼ + 1-7/8 + 2-7/8 = 37" from center to tip; 37 x 2 = 74" diameter. It's just not as easy to measure as a 2-blade. Seems my scratchpad at the hangar last night came up to ~73-3/8 or so; I'll double-check the numbers tomorrow.

 

[carusoam]

Hank,

The conclusion was that the blade diameter for two and three were the same....

Search for threads with Norman (testwest).  He was also collecting data on blade width as well for computer modeling.

My 2 blade Hartzell on my M20C had 74" diameter

my 3 blade McCauley on my M20R has (details to be checked......)

Best regards,

-a-

[KSMooniac]

The MT is the only 3-blade prop for the J/K/pre-J models that is a smaller diameter than the OEM 2-blade props.  The Hartzell and McCauley 3-blade props are all 74" diameter.

[Hank]

Quote: carusoam

Search for threads with Norman (testwest).  He was also collecting data on blade width as well for computer modeling.

My 2 blade Hartzell on my M20C had 74" diameter

my 3 blade McCauley on my M20R has 76" diameter (75" min)

 

That would have been the one! I've already sent the measurements to Norman, that's how I was able to draw such a pretty prop blade . . .

[jetdriven]

So, a 3 blade prop "looks sexy" and perhaps adds climb performance (4 cylinder Mooney).   It is also slower, costs more, and has the same diameter.  The MT has issues with paint cracking and IA's rejecting blades for annual every year because MT wont release data.

  It seems to me you should keep your 2-blade prop or get a Hartzell top prop, and spend that extra 2K on pantyhose, little black dresses, and high heels. Those "look sexy" too.  Use the difference to buy a couple years avgas.

Oops did I just say that?

[Hank]

Some of our planes had 3-blades when we bought them . . . and high heels hurt my feet . . .