C models with no dorsal fin - why??

[DXB]

Throwing this out for fun but largely pointless discussion:

Kerrville stopped putting dorsal fins on the M20C in my year (1968), and this omission remained through the last year of the model in 1978.  As far as I can tell, every single other metal wing M20 ever made has a dorsal fin. So why the heck did they take it off all the later Cs? They started making some other cost cutting changes that year, but i can't imagine not riveting that simple aluminum piece on one model saves very much.  

Google says dorsal fins add yaw stability. My short body has many wonderful traits, but yaw stability in turbulence is NOT one of them. In turbulence, the tail wags quite a bit and helps rear sear passengers who sit further off the CG axis get all pukey.  But I would imagine adding yaw stability also decreases rudder effectiveness?   

So, has anyone here put a dorsal fin on their '68-'78 C model?  Does it improve anything, other than help the plane feel like it fits in better with its siblings?  It's a $500 Lasar mod part that I bet is easy to install but hardly seems like a priority.

[bonal]

Mine has no fin 64 personally I think the short body looks leaner and more sleek without it. I do notice a slight bit of yaw waggle in light turbulence but it's never uncomfortable kind of lets me know the air is moving and reminds me to keep my feet on the rudder. Are you sure yours is a 68 I thought they had the extended rudder by then.

[DXB]

3 minutes ago, bonal said:

Mine has no fin 64 personally I think the short body looks leaner and more sleek without it. I do notice a slight bit of yaw waggle in light turbulence but it's never uncomfortable kind of lets me know the air is moving and reminds me to keep my feet on the rudder. Are you sure yours is a 68 I thought they had the extended rudder by then.

Full length rudder came on the C in '69.  I wonder if your fin was removed at some point. Here's both a '63 and a '64 that have them:

http://www.trade-a-plane.com/search?category_level1=Single+Engine+Piston&make=MOONEY&model=M20C&listing_id=1762504&s-type=aircraft

http://www.trade-a-plane.com/search?category_level1=Single+Engine+Piston&make=MOONEY&model=M20C&listing_id=2182488&s-type=aircraft

Even all the pix of B models that I find have them.

[Hank]

My 1970 C has a dorsal fin, and I've not noticed any tail waggle from the front seat (except sometimes turning final over the river just below the dam . . . ).

[mooniac15u]

My 1963 M20D did not have a dorsal fin. 

[1964-M20E]

My former  64 E model had the fin maybe with the 200HP they left it on.  I notices a slight wiggle or fish tail at cretin items but never much.

 

I have an old tail section with the fin should you want one it would take some effort to drill the rivets and remove it.

 

 

[carusoam]

It's size and location doesn't allow for much force compared to everything else...

But, it may provide a nice place to hide some antennae.

Best regards,

-a-

[gsxrpilot]

My 64 C had the LASAR fin.

[klystron]

I think my 62C has the LASAR fin. 

[Andy95W]

IIRC, the M20D didn't have the dorsal fin.

I have the LASAR mod but I also have tail waggle, especially in turbulence, so I don't really think it does much.  It does look cool, and you can hide your ELT antenna inside it- which is probably worth at least 8-10 knots.

[HRM]

Without the fin, the E is no longer Super.

[Raptor05121]

21 hours ago, mooniac15u said:

My 1963 M20D did not have a dorsal fin. 

Ditto.

I have an old picture with mine, with a different colored dorsal fin that says "201" on it, so obviously not factory.

[klystron]

On a similar note. Does anyone have any experience with putting the ELT antenna under the fiberglass LASAR dorsal fin? My local A&P told me he has seen it a few times on other moony's with that mod.

[Mooneymite]

My '74 C has the dorsal fin.

[Andy95W]

1 hour ago, klystron said:

On a similar note. Does anyone have any experience with putting the ELT antenna under the fiberglass LASAR dorsal fin? My local A&P told me he has seen it a few times on other moony's with that mod.

I did it on my first M20C.  Must've gained 8-10 knots.  Or maybe it just looked faster.

[M20F-1968]

Should you want a dorsal fin, I have the one that came on my 1967 F.  It is in excellent shape.  I removed it to put on the dorsal fin from a 1998 Ovation.

You can reach me at (617) 877-0025 or e-mail me at john.breda@gmail.com

Thanks,

John Breda

[rbuck]

I have a 70C, and I have a dorsal fin. I have never notice any tail waggle in my plane. I also have a curved piece in there so that it's not a 90 degree angle from the back of the plane to the front of the horizontal stabilizer. I have the full tail rudder, too. Maybe that makes up for the rudder authority if it really is an issue. 

[Andy95W]

2 minutes ago, rbuck said:

I have a 70C, and I have a dorsal fin. I have never notice any tail waggle in my plane. I also have a curved piece in there so that it's not a 90 degree angle from the back of the plane to the front of the horizontal stabilizer. I have the full tail rudder, too. Maybe that makes up for the rudder authority if it really is an issue. 

Nice looking airplane!

Your dorsal fin is either factory parts or (most likely) the LASAR mod.

[carusoam]

The small dorsal fin is factory.  At least it was in 1965...

The addition is the sealing pieces that close the large gap and allow the tail to move back and forth and minimize wind resistance in cruise.

I had to find some pictures of my old 65C...

Best regards,

-a-

[rbuck]

2 hours ago, N1395W said:

Nice looking airplane!

Your dorsal fin is either factory parts or (most likely) the LASAR mod.

Thanks!

[Andy95W]

From Those Remarkable Mooneys:

The M20D did not have the dorsal fin.  Not sure about the conversion process to a D/C, but I don't think the dorsal fin was included.

Beginning with 1968, the dorsal fin was removed through 1977 with the exception of the Butler year- 1971- that also included the "stinger" attachments:

1976:

1969:

M20D:

According to the book, there was no production in 1972 and 1973.

[StinkBug]

My 68 has it, but the paint doesn't match so I'm assuming it was added sometime after the 1975 strip and repaint. I do notice a little waggle in turbulence, but not much. 

[Mooneymite]

8 hours ago, N1395W said:

From Those Remarkable Mooneys:

Beginning with 1968, the dorsal fin was removed through 1977 with the exception of the Butler year- 1971- that also included the "stinger" attachments:

1976

According to the book, there was no production in 1972 and 1973.

Strange since my 74 definitely has one and Hank's 70 has it.

[Andy95W]

3 hours ago, Mooneymite said:

Strange since my 74 definitely has one and Hank's 70 has it.

No idea, just passing along what was in the book.  Entirely possible the information in the book is inaccurate, although the pictures don't lie- definitely 1970's vintage M20Cs without dorsal fins.

Any chance it was added to your and Hank's airplanes at a later date?

[carusoam]

There were large swings in the economy in those days.  The factory cut a lot of things like expensive flush rivets for less expensive round head rivets in some places...

Key words of the day were oil embargo and gas lines and odd and even days...

Remember those good old days?

Best regards,

-a-