Anybody tried inner gear doors on a vintage?

[garytex]

Once again my mind wanders to the ignored elephant in the room, that giant hole in the bottom of the wing.  I have a SWTA modded F that runs pretty nice, and wonder about putting inner gear doors from a J on the gear.  It seems like such a no-brainer, but I never hear any gossip about it, and wonder if there isn't some fatal flaw with that bright idea.  Anybody tried this, how complex was the change?  I have heard from DaV8or that he has heard the gear gets hard to swing and from Jetdriven that they are good for 3 Kts.  Whats the skinney, guys?  I would appreciate hearing from anybody who has already invented that particular wheel (well cover).  

Thanks,

Gary

[jetdriven]

You can put the fiberglass low-profile gear doors on a vintage Mooney with the Modworks STC.  The STC costs you 250$, I heard,  from Mod Squad, and the doors themselves are 500$ for the pair.  Supposedly they are worth 2 MPH over the factory gear doors. I wouldnt put them on a manual gear Mooney nor a 20:1 electric gear airplane. It increases effort to retract vs. no doors at all, but the 40:1 gearset handles it fine.

 

I just did this to my machine. While you are at it, get the wheel well liners, thats another MPH or two, and I think the airplane is quieter but no data on that.

[jetdriven]

Well we decided to go whole hog and the list of mods follows:

• fiberglass inner gear doors
• wheel well liners
• aileron gap seals
• fiberglass dorsal fin with 406ELT compliant antenna under the fin
• horizontal tail root fairings
• wing root fairings
• complete rework of cowl
• new windshield
• a full strip and paint.

might just make the 201 number yet. First race was 183 MPH, now its 193 MPH.

 

 

[rbridges]

I have the inner fairings on my C model with a johnson bar.  I bought it this way, so everything I say is what the original owner said.  Good for about a knot or so; he didn't seem like it was that big of a difference.  He also mentioned retraction effort was much harder with the fairings.  I have to retract shortly after leaving the runway or I'd never get the gear up.

 

They look cool, but if I didn't already have them, I wouldn't pay to get them.

[Marauder]

I have the inner fairings on my C model with a johnson bar.  I bought it this way, so everything I say is what the original owner said.  Good for about a knot or so; he didn't seem like it was that big of a difference.  He also mentioned retraction effort was much harder with the fairings.  I have to retract shortly after leaving the runway or I'd never get the gear up.

 

They look cool, but if I didn't already have them, I wouldn't pay to get them.

 

Do they change the VLo speeds at all? I would love to get my gear speeds up closer to a J's.

[fantom]

Keep in mind, though, that J models with aluminum inner gear doors have tear drop fairings behind them that probably actually increase drag when the inner gear doors are removed, so it doesn't necessarily follow that their installation adds 5 knots.

 

 

Correct, and another reason for those with tear drop fairings to get the gear tucked up quickly.

[N201MKTurbo]

I will have to post the pictures of what Oshkosh did to my left door. My first leg going home, the plane seemed kind of slow. It flew fine after I bent the door back into shape. I think those doors are a PITA...

[garytex]

Thanks for all the Information guys.

Openskyflier: the calipers are already rotated I believe.

To all; I'm astounded that covering that really pretty giant hole In the bottom of the wing better is only good for a little more speed than one or two mph. Does that seem weird to anybody else? There must not be much going on In that area under the wing aerodynamically speaking.

Gary

[Alan Fox]

The only mod that gives any signifigant increase is the cowl mod , everything else is inconsequential.....

[rbridges]

The only mod that gives any signifigant increase is the cowl mod , everything else is inconsequential.....

 

I think the windshield mod is worth some, but maybe you were including that with the cowl mod.

[rbridges]

Do they change the VLo speeds at all? I would love to get my gear speeds up closer to a J's.

 

 

sorry, but I honestly don't know.  I still use the original speeds.

[yvesg]

Thanks for all the Information guys.

Openskyflier: the calipers are already rotated I believe.

To all; I'm astounded that covering that really pretty giant hole In the bottom of the wing better is only good for a little more speed than one or two mph. Does that seem weird to anybody else? There must not be much going on In that area under the wing aerodynamically speaking.

Gary

Looking at my bird from underneath like this picture... one can see that there is not much drag there.

Yves

[garytex]

Nice paint Yvegs.

I see what you mean. The uncovered part is not not huge, but it goes against what I think I know about aerodynamics. (And folks, me included, are always allergic to something that refutes what they think they KNOW). I imagine air buffeting in and out of the hole, generating more turbulent flow downstream of the hole, and air being accelerated, drug along by rather than merely pushed aside by a covered hole.  I think that I want to accelerate the airplane, not the air. In AR-15 rifles there is a hole in the barrel to bleed gas into a little tube that cycles the action.  With a borescope you can actually see erosion of barrel material downstream of the hole in a pattern that suggests turbulent flow.

Although I am suprised that the benifit is apparently so little, thats still a relatively cheap 3 mph, and I am also surprised that it is not a more widespread mod.

Gary

[orionflt]

Thanks for all the Information guys.

Openskyflier: the calipers are already rotated I believe.

To all; I'm astounded that covering that really pretty giant hole In the bottom of the wing better is only good for a little more speed than one or two mph. Does that seem weird to anybody else? There must not be much going on In that area under the wing aerodynamically speaking.

Gary

Even though there seems to be a big hole the under side of the wing is a high pressure area, between that and the boundry layer most of the air is speeding by the opening. What air does go into that area usually ends up in the dead space on the aft side of the wheel well with no where to go. the wheel well liners redirect the air around and back out of the well area reducing the amount of turbulance crwated by the trapped air,that is why the wheel well liners give an improvement in both airspeed and climb rate.

[Skypylott]

I installed the lower gear doors on several older manual gear Mooney's back in the old days. The mounting brackets were Mooney parts but the doors were fiberglass pieces made by Lake Aero Styling in California. They were a lower profile door and fit the wing tight and didn't need the extra bubble fairing aft of the door like Mooney used. The Johnson bar has to be modified by welding a 4130 steel strap around the T. The Johnson bar had to be annealed, welded and then reheatreated. Also the triangle shaped bell-cranks had to be replaced with heavier versions, also Mooney parts. Gear had to be retracted prior to 80 knots or it was very difficult. We fixed that by doubling the spring rate on the helper springs in the belly then once Johnson bar was unlocked gear almost put itself up. Worked well and whole thing was worth about 4 knots.

[garytex]

Orion That makes perfect sense to me

Skypylot Thanks that's exactly what I was looking for, thanks to all and specially to you for responding

Gary