Mooney tail

[Blue on Top]

49 minutes ago, Andy95W said:

I didn't realize the composite structure was so much heavier than the metal.  It ought to reduce man hours, at least- but what a waste of useful load.

My thoughts on speed had nothing to do with laminar flow, which is really nonexistent at the speeds our airplanes fly.  It was all about how fast the wood wings were, which I would assume was because of the smoothness.

When aircraft materials get down to minimum thickness (especially control surfaces) aluminum gets far lighter than composites … yes, even carbon fiber, for a couple reasons.  One, to get both the strength and the damage tolerance required, a composite layup minimum is 2 core 2 (2 fabric layers, a core layer and 2 fabric layers) which is heavier than 0.020 aluminum.  Second, because carbon is (somewhat) conductive a metallic mesh (normally copper … aluminum and carbon don't get along well) must be on the entire outside of each part for HIRF and lightning protecting.  Otherwise a lightning strike would burn a rather large hole in whatever it hits … including structure.

As for the labor savings, that is arguable (don't ask Mooney about it).  Yes, one doesn't need to buck rivets, but on the other hand, one doesn't need to layup, pressure cook and glue parts together either.  A lot of this is dependent on whether one is building 1 part; 10 parts; 100 parts; 1,000 parts; 10,000 parts; 100,000 parts; or 1,000,000 parts per year.  Another huge variable with that is the amount of tooling required and how the parts are assembled and are those tools different.

You're right on with the aerodynamics.  Not laminar flow, but smoother flow. 

[Blue on Top]

34 minutes ago, PT20J said:

Not clear about this -- wouldn't a spanwise flow component on the control surface reduce effectiveness either way?  -Skip

First of all, dang you're good!

In this case, spanwise flow direction does matter.  Just because the flow changes direction (especially with rudder deflection), it doesn't change surface static pressure (the real force).  BUT The vertical stabilizer is a very low aspect ratio wing.  If the flow is going up the vertical (swept back vertical), the tip losses are huge.  But if we force the flow down the vertical (Mooney tail), we have in essence end-plated the vertical stabilizer, making it much more efficient and effective.

[carusoam]

Way to go JIM!

Mixing applied composite construction technology and laminar aerodynamics!

Mooney was stepwise following your lead...

They chose the non-structural parts first...

• cowl
• wing tips
• cabin area

A wing or two or three would be interesting... main wing, and stabilizer and rudder...

• Ultra Smooth
• corrosion resistant, regarding lightning strike mesh...
• Leak resistant, and... fuel tanks more separated from the cabin

 

there is plenty of weight in composite structures... development isn’t always going to be easy.

There are charley weights in the back of my O that could be easily swapped for a nice smooth tail structure...

-a-

 

[bradp]

What spar design does the PA-24 utilize?  Probably not the problematic box of the Pa-28 and later...

Mooney had the right idea ... use composites in the right places- skins / cowls / etc and that keeps the weight down. 
 

Look at the Columbia / Corvallis / TTX line. Those things are tanks but they are very much over build and quite heavy @ 3600 lbs.  overbuilt except for that pesky debonded wing skin problem they had with their outsourced parts procurement.  

[PT20J]

10 hours ago, Blue on Top said:

First of all, dang you're good!

In this case, spanwise flow direction does matter.  Just because the flow changes direction (especially with rudder deflection), it doesn't change surface static pressure (the real force).  BUT The vertical stabilizer is a very low aspect ratio wing.  If the flow is going up the vertical (swept back vertical), the tip losses are huge.  But if we force the flow down the vertical (Mooney tail), we have in essence end-plated the vertical stabilizer, making it much more efficient and effective.

Thanks for the compliment, but I'm just trying to figure out stuff you probably knew 20 years ago!

I never considered the tip effects - thanks for the insight. So, the vertical tail gets to be smaller with less parasitic drag and yet has a longer "effective" span in a sideslip which recovers any loss in effectiveness due to the reduced area. I think that's the idea. Wonder if this would require a larger dorsal fin? Comparing the Mooney and Comanche 3-views, the Mooney does appear to have a larger dorsal, but it's a little hard to tell for sure.

Skip

[Blue on Top]

10 hours ago, PT20J said:

Wonder if this would require a larger dorsal fin? Comparing the Mooney and Comanche 3-views, the Mooney does appear to have a larger dorsal, but it's a little hard to tell for sure.

Skip

Dorsal fins are a unique animal.  Helpful for smaller sideslip angles, hurtful for larger sideslip angles (vortex shed by dorsal comes off the vertical and sucks the rudder over, decreasing control force) and helpful for spins (area is area).  I would take an (educated) guess that the dorsal was added for spins.  Sharpness on the upper edge is important.

[cliffy]

Let me drop in another anomaly on the Mooney tail-

In 1969 (sns 690000 +) the elevator up down angles were changed from up 24 up /10 dwn to up and dwn being  22 degrees

The bungee setting angles also changed from up 19 to up 10

What was the reason for this change> I've never found anyone with an answer except (I've been around long enough to slightly remember) that at that time I do remember something about Mooney having to retest the outer edges of the stall envelope and it seemed that with the less down angle before 69, recovery from a stall (spin?) didn't quite meet federal specs and requirements. 

I'd like to find some hard evidence other than just my recollection. Several years ago I posed this question at the factory and no one could "remember" why it was done. I'm going back 50 years now in memory.

OK brain trust, let me hear some answers :-) I'm all ears  Anyone else go that far back? 

[MooneyMitch]

1 hour ago, cliffy said:

Let me drop in another anomaly on the Mooney tail-

In 1969 (sns 690000 +) the elevator up down angles were changed from up 24 up /10 dwn to up and dwn being  22 degrees

The bungee setting angles also changed from up 19 to up 10

What was the reason for this change> I've never found anyone with an answer except (I've been around long enough to slightly remember) that at that time I do remember something about Mooney having to retest the outer edges of the stall envelope and it seemed that with the less down angle before 69, recovery from a stall (spin?) didn't quite meet federal specs and requirements. 

I'd like to find some hard evidence other than just my recollection. Several years ago I posed this question at the factory and no one could "remember" why it was done. I'm going back 50 years now in memory.

OK brain trust, let me hear some answers :-) I'm all ears  Anyone else go that far back? 

Wish our dear Bill Wheat was still with us for your question.

Curiosity....... did you speak to Bill years ago regarding your question? 

[cliffy]

Yes and he declined to say anything

[Blue on Top]

6 hours ago, MooneyMitch said:

Wish our dear Bill Wheat was still with us for your question.

And Mikey, too!

[Blue on Top]

8 hours ago, cliffy said:

Let me drop in another anomaly on the Mooney tail-

In 1969 (sns 690000 +) the elevator up down angleAll the s were changed from up 24 up /10 dwn to up and dwn being  22 degrees

The bungee setting angles also changed from up 19 to up 10

What was the reason for this change> I've never found anyone with an answer except (I've been around long enough to slightly remember) that at that time I do remember something about Mooney having to retest the outer edges of the stall envelope and it seemed that with the less down angle before 69, recovery from a stall (spin?) didn't quite meet federal specs and requirements. s

I'd like to find some hard evidence other than just my recollection. Several years ago I posed this question at the factory and no one could "remember" why it was done. I'm going back 50 years now in memory.

OK brain trust, let me hear some answers :-) I'm all ears  Anyone else go that far back? 

I don't go back that far (I was in kindergarten in 1969), but here is what I found in the TCDS (the bible for a certificated airplane - Type Certification Data Sheet).  All the changes that have been mentioned above (elevator travel, bungee changes, etc.) happened earlier (when I was 1 year old … 1965).  The changes occurred between the "E" (last short body) and "F" (first mid-body).  I hope this helps and jogs more memories.

Always learning,

Ron Blum

[cliffy]

7 minutes ago, Blue on Top said:

I don't go back that far (I was in kindergarten in 1969), but here is what I found in the TCDS (the bible for a certificated airplane - Type Certification Data Sheet).  All the changes that have been mentioned above (elevator travel, bungee changes, etc.) happened earlier (when I was 1 year old … 1965).  The changes occurred between the "E" (last short body) and "F" (first mid-body).  I hope this helps and jogs more memories.

Always learning,

Ron Blum

I also pulled up the TCDS many times and I find that the changes in elevator throw start at SN 690001 IIRC that makes it a 1969 change.

Go back and take a look at the C model listing in the TCDS That is what I am referring to. The changes between a short body and others can be easily understood due to the longer tail moment arm. BUT all went to 22 &22 at about 68/69 time frame. C, E. F. BUT NOT the D Even when the D was changed to a C. 

 Could be wrong but? Regardless of the date no one remembers for sure why it happened  

AND Mikey too AND others in Engineering that day. 

[MooneyMitch]

8 hours ago, cliffy said:

Yes and he declined to say anything

That’s interesting.  Hmmm.

Doesn’t sound like our Bill. 

[MooneyMitch]

48 minutes ago, Blue on Top said:

And Mikey, too!

Good to hear from you Ron. 

[Blue on Top]

14 minutes ago, cliffy said:

I also pulled up the TCDS many times and I find that the changes in elevator throw start at SN 690001 IIRC that makes it a 1969 change.

Go back and take a look at the C model listing in the TCDS That is what I am referring to. The changes between a short body and others can be easily understood due to the longer tail moment arm. BUT all went to 22 &22 at about 68/69 time frame. C, E. F. BUT NOT the D Even when the D was changed to a C. 

 Could be wrong but? Regardless of the date no one remembers for sure why it happened 

I agree that the changes appear on the earlier models in 69.  The "F" was certified in 1965 with the larger elevator travels.

I also see that the certification basis for the "F" was also made a later revision (earlier models were Amdt 54 and "F" is Amdt 59).   This could be the reasoning, too.  The down spring is in the system for low speed stability.

Could there have been an accident in '69 or, a more simple answer, were some control system parts made differently and it was easier to make all of them the same?

[Blue on Top]

4 minutes ago, MooneyMitch said:

Good to hear from you Ron. 

You, too, Mitch.  I must be too passionate, as I have run out of MooneySpace emojis  to respond to others' posts.  I'm good with that.

[Guest]

On 12/5/2019 at 12:05 AM, Andy95W said:

I didn't realize the composite structure was so much heavier than the metal.  It ought to reduce man hours, at least- but what a waste of useful load.

My thoughts on speed had nothing to do with laminar flow, which is really nonexistent at the speeds our airplanes fly.  It was all about how fast the wood wings were, which I would assume was because of the smoothness.

I would guess that a square foot of aluminum skin weighs less and is more consistent than a square foot of composite skin.

Clarence

[Blue on Top]

26 minutes ago, M20Doc said:

I would guess that a square foot of aluminum skin weighs less and is more consistent than a square foot of composite skin.

Clarence

Yep! … and that is before the lightning strike material is added to the composite.   Typical engineering weight tolerance on aluminum is 0%; 7% for composite material.  Same is true for thicknesses, too.

Clarence:  I would give you a "thumbs up" emoji, but I am too passionate and ran out of them for the rest of the day  ... Oh wait!  It must be tomorrow somewhere 

Edited December 7, 2019 by Blue on Top

[carusoam]

On 12/6/2019 at 3:15 PM, cliffy said:

Yes and he declined to say anything

Proof Cliffy actually knew Mr. Wheat!

 

Mr. Wheat knew the inner workings of the Mooney organization... as well as he knew the inner workings of the planes themselves...

Blue, I have an extra ‘chip’ so I threw it on Doc’s post!  

Best regards,

-a-

[MooneyMitch]

15 minutes ago, carusoam said:

Proof Cliffy actually knew Mr. Wheat!

 

Mr. Wheat knew the inner workings of the Mooney organization... as well as he knew the inner workings of the planes themselves...

Blue, I have an extra ‘chip’ so I through it on Doc’s post!  

Best regards,

-a-

A gem he was .

[cliffy]

Yes he was We had a very nice long visit at his home. This was after he stopped going in to the factory every day. 

I don't know of any down spring in the short bodies. 

Down springs for stability? I didn't know about that.  Always thought they were for CG  expansion. Piper Navajos have them also. Had one break on a zero zero takeoff one morning right at lift off. Interesting ride for a few minutes. 

Edited December 7, 2019 by cliffy

[Blue on Top]

On 12/4/2019 at 1:44 PM, MooneyMitch said:

The Ralph Harmon story is a great read, by the way.  He began his aviation career as a youth, by building a Pietenpol from  a Readers Digest kit !

@MooneyMitch Is there a book or something?  I would love to read it.  Thanks!

[Blue on Top]

On 12/7/2019 at 12:19 AM, cliffy said:

I don't know of any down spring in the short bodies. 

Down springs for stability? I didn't know about that.  Always thought they were for CG  expansion. Piper Navajos have them also. Had one break on a zero zero takeoff one morning right at lift off. Interesting ride for a few minutes. 

@cliffy  (didn't mean to leave you hanging)  The short bodies don't require them.  This is not a tail volume issue but rather a stall speed, geometry and HP issue (long story).  Mooney did a GREAT job implementing them as they vary force with empennage (trim) position.

[MooneyMitch]

44 minutes ago, Blue on Top said:

@MooneyMitch Is there a book or something?  I would love to read it.  Thanks!

When I interviewed Ken Harmon, son of Ralph Harmon at his home in Albuquerque in November of 2014, Ken gave me a CD of the Ralph Harmon Papers.  I cannot put my hands on that CD currently.

With that said, I believe you can read all at http://specialcollections.wichita.edu/collections/ms/2016-01/2016-1-a.html#summary

Incidentally, Ken Harmon was in charge of the Mooney R&D Department while his father Ralph was running Mooney.  Under Ken, the Mustang and the "H" model were created among many other projects.

[Blue on Top]

PS.  The Flying issue that @PT20J (Skip) posted the link is an AWESOME issue!  Not only does it have the referenced article, but it also has the speed challenge between a new Mooney and a sports car.

AND (starting on p.77) the coolest business jet ever made!  Yes, I am very bias.  That airplane (the Citation X prototype) was my baby.  It's really, really fast, and it stalls better than a C172.  Plus, I was privileged to get several hours in a T-38 flying formation with her.