Inner Gear Doors on a Johnson Bar Mooney

[M20F-1968]

I am considering putting inner gear doors on my 1968 F model with manual gear.  I am told that they do add some stiffness to the 

raising and lowering of the gear.  I have new main gear springs and the gear works very easily now.  What experience has the

group had with adding inner gear doors to a manual gear Mooney?  What speed increase do you see?

John Breda

[ragedracer1977]

I've thought about doing the same to my Johnson bar C. All the research I've done suggests it's not a great idea.

[Marauder]

I am considering putting inner gear doors on my 1968 F model with manual gear.  I am told that they do add some stiffness to the 
raising and lowering of the gear.  I have new main gear springs and the gear works very easily now.  What experience has the
group had with adding inner gear doors to a manual gear Mooney?  What speed increase do you see?
John Breda

John - take this for what it’s worth. I spoke to Dave Matheson at Air Mods about adding them on my F during my last annual. I was interested to see if the inner doors would allow a higher gear speed for me. His response was “don’t bother”. He said the inner gear doors are not what determines the gear speed (the gear ratio is) and there is no speed advantage installing them.


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[M20F-1968]

Chris,

I was told that they do increase the force needed to raise and lower the gear (in terms of work-load with the Johnson Bar).  As such, you need

to insure that you operate the gear at lower gear speeds.  The two questions are (1) Is there an airspeed increase with them? (2) is the increase in workload/management of the Johnson Bar manageable or does it just become a headache?  

Is there anyone out there that has the inner gear doors on a manual gear Mooney?

John Breda

[Marauder]

Chris,
I was told that they do increase the force needed to raise and lower the gear (in terms of work-load with the Johnson Bar).  As such, you need
to insure that you operate the gear at lower gear speeds.  The two questions are (1) Is there an airspeed increase with them? (2) is the increase in workload/management of the Johnson Bar manageable or does it just become a headache?  
Is there anyone out there that has the inner gear doors on a manual gear Mooney?
John Breda

John - I would call a few of the MSCs and find out from them. Inner gear doors are a rarity on vintage Mooneys. As I mentioned, Dave at Air Mods said there was no notable speed increase.


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[Bob_Belville]

6 hours ago, Marauder said:

 

John - I would call a few of the MSCs and find out from them. Inner gear doors are a rarity on vintage Mooneys. As I mentioned, Dave at Air Mods said there was no notable speed increase.


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Hum, if there is no speed gain I wonder why J owners don't just remove the inner doors. Is the "outer" gear door on the J the same as on an F? With no up side and at least some downside, e.g. operating on grass, load on gear motor, weight,... why have them? 

Calling Bob Kromer...

[ArtVandelay]

John - I would call a few of the MSCs and find out from them. Inner gear doors are a rarity on vintage Mooneys. As I mentioned, Dave at Air Mods said there was no notable speed increase.

I wonder if they tested without the wheel covers? Or with the brakes on the inside? Devil is in the details. Like what is notable? 2 knots, 4 knots?


Tom

[Marauder]

Hum, if there is no speed gain I wonder why J owners don't just remove the inner doors. Is the "outer" gear door on the J the same as on an F? With no up side and at least some downside, e.g. operating on grass, load on gear motor, weight,... why have them? 
Calling Bob Kromer...

And conversely, if they were capable of producing decent speed increases, why haven’t any of the mod shops like Lasar produced them? They have wheel well covers and brake rotation but no inner gear door mods.

I suspect for manual gear planes it increases the wind resistance making the gear throw harder and for the electric gear planes, none of the vintage (or not enough of the late Fs) have the J gear motor ratios. That is probably why there isn’t a retrofit kit.

As for removal, I do know one owner who does remove them when he operates out of a grass strip.


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[EricJ]

One of my hangar neighbors, with an M20A, told me that a previous hangar neighbor with an M20C was an aerospace engineer and did load computations regarding adding the J inner doors and determined that the gear springs needed to be changed to account for the load difference.   With the new springs fabricated from a local winder they added the inner doors with a 337.    Apparently this has been done a number of times and changing the springs is a key element.

In the context of this discussion my neighbor pointed out how the inner doors on my airplane are canted in the airstream and generate the force.   I'd honestly never noticed it before, but it was obvious when pointed out.

[SantosDumont]

I have the inner gear doors on my F with a Johnson bar.  I bought the plane with them so I can’t speak to any speed increase.  Over 75kts and the gear becomes impossible to stow without doing the Mooney dip. 

[DanM20C]

17 hours ago, Bob_Belville said:

Hum, if there is no speed gain I wonder why J owners don't just remove the inner doors. Is the "outer" gear door on the J the same as on an F? With no up side and at least some downside, e.g. operating on grass, load on gear motor, weight,... why have them? 

Calling Bob Kromer...

Some have removed them.  I think I’m going to remove them from my K along with the bulky wing fairings, then roatate the brakes.  It makes for a clean looking gear, easier maintenance, and no speed penalty.  

Cheers, 

Dan

[Marauder]

I have the inner gear doors on my F with a Johnson bar.  I bought the plane with them so I can’t speak to any speed increase.  Over 75kts and the gear becomes impossible to stow without doing the Mooney dip. 

What your describing makes sense. Those inner gear doors add more drag and I believe this is the reason the J models have a different ratio on their electric gear.


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[Captnmack]

Boy John, I figured you had them. My F had them installed and removed at some point. When I was buying my F we were doing the gear swing and noticed one of the aft fairings was missing, I could tell because on the paint shadow and the fact there was one on the rights side. Also the door brackets are still installed. I too called Lasar and spoke with Dan and I believe I also spoke to Paul Loewen. They both said the doors were $700 each and without an Electrical Gear it gets very difficult to raise as the previous comment indicated. Dan also said I should remove the existing “Spad” ( aft fairing) as without the door to seal it, it’s just a drag, so off it came. I did put it on the gear to remove the interior cover behind the J-Bar and looked while it was up. I can see that rotating the calipers will help a lot. So, I would rather spend the unnecessary dollars and put a 1 piece belly on!

 

Mack 68F

[M20F-1968]

I have a one piece belly.  The MOD-Works style doors are lower profile and do not require anything mounted on the wing.  I have new springs, and longer retraction rods (Mooney made 3 lengths back in the day) so the springs are contracted, I think, maximally. The gear moves easily now and can be locked up with 2 fingers.  Can anyone comment further.  Are there any manual gear Mooneys with the Mod-Works inner gear doors?

John Breda

[rbridges]

I have them on my C model.  Never flown without them, so I can't give a good comparison.  I'm not a weenie, but I do have to raise gear shortly after rotation or else it gets too hard.  When that happens, I do a nose over to relieve the wind pressure.  They look good IMO, but they probably add very little to speed.  I would guess a knot if you're lucky.  I've also heard some people mention ground clearance.  I had a flat tire, and it bound up on the inner door flap.