2 blade vs 3 bladed prop

[CajunMooneyguy]

Hello all. Newbie. First post. Just bought a '67 M20F. It has a three bladed prop and I love the looks and feel, but I'm reading a lot about the 2 bladed prop being faster, lighter, smoother, cheaper, etc... Why have the 3 blade prop? Can someone share the pros and cons of each? Is it worth converting back to a 2 blade? Is my 3 blade prop worth anything on the used market? Thanks in advance. Todd

[Hector]

Your 3 blade prop has better ground clearance and improved climb performance over 2 blade prop. However, you loose some in cruise performance. Can you tell us the OEM for your 3 blade prop? Depending on what type you have there are additional pros/cons. I would not change your prop unless there is a compelling reason to do so, and the slight differences in performance is not a compelling reason.

[CajunMooneyguy]

Im pretty sure It's a McCauley. The last guy painted over the prop stickers at annual a week ago. I'm in Tennessee till Wednesday and when I get home ill check the logbooks. Thanks!

[Lood]

Your 3 blade prop has better ground clearance and improved climb performance over 2 blade prop. However, you loose some in cruise performance. Can you tell us the OEM for your 3 blade prop? Depending on what type you have there are additional pros/cons. I would not change your prop unless there is a compelling reason to do so, and the slight differences in performance is not a compelling reason.

 

In the case of Hartzell props, there's no ground clearance advantage with a 3 blader. Both the 2 and 3 bladers are 74" in diameter.

[jetdriven]

Your 3 blade prop has better ground clearance and improved climb performance over 2 blade prop. However, you loose some in cruise performance. Can you tell us the OEM for your 3 blade prop? Depending on what type you have there are additional pros/cons. I would not change your prop unless there is a compelling reason to do so, and the slight differences in performance is not a compelling reason.

3-4 knots of cruise is not insignificant, its ~3%.   Also, with the exception of the MT prop, all 3-blade props have the same diameter.  Some also have a wierd 3-2 vibration harmonic due to the flat Lycoming crank and 4 cylinders working on a 3-blade vs. a 2-blade prop.

[Hank]

True, the 3-blade prop is the same diameter as the 2-blade with the pricey exception of the MT composite.

 

Apparently the 201-windshield offsets the 3-blade, as I have both and make book speed. 1300+ nm west at 127 knots; return trip east at 152 knots; book is ~140.

 

Vibration is a sometimes affair, seems to be airframe-specific [i don't have any] and may be reduced through dynamic balancing.

 

There should be a good market if you want to sell it, both to other Mooneys and to experimentals.

[rbridges]

I definitely don't think it's worth converting either way.  If the plane flies smooth, I'd be OK with it.  You gain some climb speed but lose a little cruise speed.  

 

Trying to find the perfect vintage plane is difficult and prop would be the last on my list.  Having the 3 blade prop, you shouldn't have the recurring AD.

[Alan Fox]

I converted from a two blade to a three blade in a Bonanza , on Beechtalk they all said better climb , and slower cruise ,   Both were imperceptable....The three blade is MUCH quieter and MUCH smoother , The harmonics of a three blade prop are different than a two blade prop , and you will notice the difference , just takes getting used to,,,,,Stick with the three blade unless you have a problem with it....

[CajunMooneyguy]

Great replies all! Thanks. I really prefer the "looks" of the three blade and the previous owner said the two blade was indeed louder and rougher. I'm ok with losing 3 potential knots to gain climb performance. My plane is a '67 M20F, and it has the tail fairings, wing tips with hidden antenaes, one piece windshield, wing root fairings, gap seals, lower cowl closure, and wing and flap hinge fairings. What other speed mods are there out there that I can install.....besides 201 windshield and cowl? I'm planning on those soon. I know there is a belly pan for the Cs, what about the Fs?

[rbridges]

Great replies all! Thanks. I really prefer the "looks" of the three blade and the previous owner said the two blade was indeed louder and rougher. I'm ok with losing 3 potential knots to gain climb performance. My plane is a '67 M20F, and it has the tail fairings, wing tips with hidden antenaes, one piece windshield, wing root fairings, gap seals, lower cowl closure, and wing and flap hinge fairings. What other speed mods are there out there that I can install.....besides 201 windshield and cowl? I'm planning on those soon. I know there is a belly pan for the Cs, what about the Fs?

 

201 cowl would be next to impossible and extremely costly.  You might as well sell and get a 201.  The windshield is probably one of the best bang for the buck upgrades.  It's one of the few that people will say definitely gives you a few knots.

[Alan Fox]

Dont get the windshield , you lose the access to the avionics and it is a great thing to have....The only speed mod worth its money is the cowl closure....I did all the mods to a B model , and the only one worth a dam is the cowl closure.... Good luck w/new bird...

[N601RX]

I'm about to install a 1pc belly and 201 Windshield.  I'm going to do some before and after test and will report what I see.

[Hank]

Dont get the windshield , you lose the access to the avionics and it is a great thing to have....

 

My 201 windshield has an avionics access panel on both sides. Guess it depends on whose STC you get [or which are still available].

 

Good luck with your mods. You'll love the belly at your first annual, especially if you get the Bill Wheat model with dzus fasteners. I didn't like removing the 52 screws in my belly until I both saw an original with 100+ screws, and removed/reinstalled mine twice using a ratcheting screwdriver powered only by my arm, replacing any screws with messed up heads or threads. Now they all go in and out nicely.

[Marauder]

My 201 windshield has an avionics access panel on both sides. Guess it depends on whose STC you get [or which are still available].

 

Good luck with your mods. You'll love the belly at your first annual, especially if you get the Bill Wheat model with dzus fasteners. I didn't like removing the 52 screws in my belly until I both saw an original with 100+ screws, and removed/reinstalled mine twice using a ratcheting screwdriver powered only by my arm, replacing any screws with messed up heads or threads. Now they all go in and out nicely.

 

 

I have the SWTA windshield mod with the access panel. You can get a hand down there but not much else.

 

Speaking of the one piece belly. I have been entertaining going with one until I saw the installed price for the Lasar version (~$10k). Are there cheaper alternatives other than the Lasar version?

[M20F-1968]

My plane is a '67 M20F, and it has the tail fairings, wing tips with hidden antenaes, one piece windshield, wing root fairings, gap seals, lower cowl closure, and wing and flap hinge fairings. What other speed mods are there out there that I can install....

 

The question was asked and I can not resist this answer --  take a look at my gallery -- there is not much more left in the way of mods...

 

I think the 201 windshield is best installed without the external access panels.  Onece you start putting money into avionics, you do not appreciate rain leaking in onto them.  There is pleanty of panel and avionics access from the instide if you design it right.

 

John Breda

[Alan Fox]

John I use foam weather stripping from home depot and my cover does not leak , also I replaced the three pieces with a single piece , so less possibility for leaks....Marauder the Belly is only about 3.5 K installed , but It is not a speed mod , just a cheaper  fix for a geared up airframe ,

[Marauder]

John I use foam weather stripping from home depot and my cover does not leak , also I replaced the three pieces with a single piece , so less possibility for leaks....Marauder the Belly is only about 3.5 K installed , but It is not a speed mod , just a cheaper  fix for a geared up airframe ,

 Alan -- where does one go about getting a single piece?

 

Also where did you see a belly pan for $3.5k installed? We talking about the same thing?

[Alan Fox]

 Alan -- where does one go about getting a single piece?

 

Also where did you see a belly pan for $3.5k installed? We talking about the same thing?

2350 from Lasar , 1500 to install , I ws a little light...

[Marauder]

2350 from Lasar , 1500 to install , I ws a little light...

Hmmm... I see where you got your price -- you are talking an C/E The longer bodies are a bit more expensive and labor intensive:

 

 

Parts Hardware & STC

$4,690.00

Labor Hours

70 * $70 (shop rate) = $4,900.00 Description

Replacement of the multi-segmented belly skins with a smooth aerodynamically contoured one-piece fairing. Eliminates needless hours of removing screws and can conceal various antennas. *This can account for up to 6 MPH by burying some typical antennas.

[N601RX]

I purchased the new one that Nels had for sale that had never been installed. I tracked down the STC owner and got him to supply me with the correct paperwork. It is made by Aero Mods. In talking with him he told me that he had not made any of them in a few years but would like to make some more of them. His price is $1800. It has 2 runners down the middle. For the short bodies, you just cut some length off the rear. He told me he could install one in a day, So I suspect it will take me a weekend. He said most people who installed reported a 2 knots increase. It also gives you access to the area under the rear seat which is not a removable skin on my F model. The install of it involves drilling out several rivets to remove a couple of formers and middle skin that are no longer used and the match drilling all the mounting holes. Unfortunately the holes are not the same on any 2 planes. I invited him to come here and provide more information.

[TTaylor]

I purchased the new one that Nels had for sale that had never been installed. I tracked down the STC owner and got him to supply me with the correct paperwork. It is made by Aero Mods. In talking with him he told me that he had not made any of them in a few years but would like to make some more of them. His price is $1800. It has 2 runners down the middle. For the short bodies, you just cut some length off the rear. He told me he could install one in a day, So I suspect it will take me a weekend. He said most people who installed reported a 2 knots increase. It also gives you access to the area under the rear seat which is not a removable skin on my F model. The install of it involves drilling out several rivets to remove a couple of formers and middle skin that are no longer used and the match drilling all the mounting holes. Unfortunately the holes are not the same on any 2 planes. I invited him to come here and provide more information.

 

What is the net weight difference according to the STC?  How many screws will be left when you are all done?

[N601RX]

10 lbs and no arm changes. I have not counted, but I think it will be around 40.

[Marauder]

10 lbs and no arm changes. I have not counted, but I think it will be around 40.

I hope your mystery guest accepts the invitation. The product and the installed pricing is something in my budget. Tell him he has potential customer(s)!

[N601RX]

Hopefully he will. His price was a lot more inline with what I thought most people were willing to spend than what the other companies are pricing theirs at. I believe there is a good market for reasonably priced mods.