Retro-fit iS Main Gear Seals to Legacy 12

[Tony_T]

For background, yes, I do know that intersection fairings are available and can be adapted. I am not interested in those, but have been interested in the RV12iS main gear seals since I saw them on the prototype iS airplane at Aurora. The hole in the fuselage for the main gear leg is large and unsightly. Also, there may be benefit of lowered CO getting into the cockpit. My airplane in normal cruise shows 3-4 ppm CO. I do have the firewall well sealed and wing seals installed so the gear openings are the largest openings and are in the exhaust slipstream especially on the starboard side. This level of CO is not alarming at all, I think OSHA limits for CO are something like 35-50 ppm for 8 hours. I know airplanes can go high where the CO matters more, but without researching I don't know if FAA has CO limits anywhere in the regs.

The iS gear seals can be installed on the legacy RV12. The only deviation from the iS installation are four screw locations on each side where it was impossible, for me anyway, to fish in plate nuts. I used Truss Head type A 8X1/2 SS SHT MTL screws from ACsprce for those locations. See picture. I am not real happy using sheet metal screws but they are a better option than rivnuts and won't prove to be a problem. The screw hole is small and the sheet metal screws can be replaced by LP4-3 rivets. There are several locations where CS4-4 flat head rivets are used. I removed the LP4-3 and countersunk those holes slightly with a deburring tool and pulled in the CS4-4.

I have many details of this retro-fit if there is any interest.

 

[GatorsR1]

Hi Tony
I have similarly lusted for the "new" main gear seals on my 12 (aerodynamics, critter blockers & the pleasure of upgrading).
Bought the parts required from Van's, then realized it'd take some magic to install those nutplates on a completed fuselage.
Figured sheet metal screws (or LP4's) would work but neither seemed as aesthetically pleasing (especially if those plates are ever to be removed/reinstalled).
Any further details/encouragement might entice me to finish that job (before OSH !)
Thanks
bob

 

[Tony_T]

Hi Bob
I installed nutplates on the fuselage gear bottom closeout. You can buy those with the holes already drilled. I used new closeouts for match drilling my painted parts. The other 4 screws on the bottom gear seal assembly are the Truss head SS that I detailed. Those look exactly like all the other SS 8X32 screws on the plane. No problem esthetically that I can see. That whole area also is a sea of LP4-3 rivets so even those would not seem to be out of place to attach the bottom gear seals in place. Attaching some more pictures. I felt the biggest issue was cutting the rubber parts out the exact size required. I scaled the paper templates from the digital plans and compared the templates to the physical parts to make sure the rubber bits would be an exact fit. Otherwise you problably would not be able to get the top gear seal especially to fit. Once I was satisfied that the paper templates were perfect, I used them to make metal templates out of 0.035 alum and used those to cut the rubbers. The plans suggest drilling the holes in the rubber, but I used a 1/4 inch leather punch instead. Those small fuel tank sealant packages are so expensive now that you need to find someone who has the bulk stuff and borrow a small amount for attaching the rubbers. You have to be kind of careful doing that as the parts assemblies are distinctly different.
Agree on the pleasure of upgrading, and there are other benefits as you suggest. This is a worthwhile and fun project.
.

 

[cactusman]

Good work and good write up as always Tony!

 

[DaveWelch]

For background, yes, I do know that intersection fairings are available and can be adapted. I am not interested in those, but have been interested in the RV12iS main gear seals since I saw them on the prototype iS airplane at Aurora. The hole in the fuselage for the main gear leg is large and unsightly. Also, there may be benefit of lowered CO getting into the cockpit. My airplane in normal cruise shows 3-4 ppm CO. I do have the firewall well sealed and wing seals installed so the gear openings are the largest openings and are in the exhaust slipstream especially on the starboard side. This level of CO is not alarming at all, I think OSHA limits for CO are something like 35-50 ppm for 8 hours. I know airplanes can go high where the CO matters more, but without researching I don't know if FAA has CO limits anywhere in the regs.

The iS gear seals can be installed on the legacy RV12. The only deviation from the iS installation are four screw locations on each side where it was impossible, for me anyway, to fish in plate nuts. I used Truss Head type A 8X1/2 SS SHT MTL screws from ACsprce for those locations. See picture. I am not real happy using sheet metal screws but they are a better option than rivnuts and won't prove to be a problem. The screw hole is small and the sheet metal screws can be replaced by LP4-3 rivets. There are several locations where CS4-4 flat head rivets are used. I removed the LP4-3 and countersunk those holes slightly with a deburring tool and pulled in the CS4-4.

I have many details of this retro-fit if there is any interest.
View attachment 64379View attachment 64378View attachment 64377

Much, much interest here Tony! I'm hoping to get my plane painted this fall so I'm looking to install/finish any mods that affect the exterior.
If you have any detail to add beyond what you've given Bob below, I'll much appreciate your sharing.
Oh BTW, would it be possible to reach the inside area of the skin to hold a Tinnerman Nut to screw into? Long skinny arms? A trained snake? Snakes on a plane, Yipes!
Thanks!
Dave

 

[DaveWelch]

Hi Tony
I have similarly lusted for the "new" main gear seals on my 12 (aerodynamics, critter blockers & the pleasure of upgrading).
Bought the parts required from Van's, then realized it'd take some magic to install those nutplates on a completed fuselage.
Figured sheet metal screws (or LP4's) would work but neither seemed as aesthetically pleasing (especially if those plates are ever to be removed/reinstalled).
Any further details/encouragement might entice me to finish that job (before OSH !)
Thanks
bob

Hey Bob! Come on down when the weather cools. We'll do the install together at 42J.
Many, many changes for the better at Moontown (3M5) I hear.
Dave

 

[Tony_T]

Dave. I doubt that it is possible to access those two spaces to install a nut plate or tinnerman. There are lightening holes in the structure, but it would take an inordinate amount of skill and patience to get in there.

The top seal can be fished in to place with a piece of safety wire in one of the nut plate holes, pulled up tight and the other screw started. It took most of a day to actually install the completed assemblies on the left side, the right side then only took about an hour.
Here is the starboard side, before and after...

 

[seagull]

Is there any reason not to use a foam rubber, install it from the inside on the 4 sides of the landing gear leg, push it out the openings and trimmed flush to the fuselage. It would seem a simple flexible light weight way to seal the gear leg. The gear bolt access panels would be a easy access way to install the foam. I'm thinking of doing this but asking in case I am missing something.

 

[12vaitor]

Is there any reason not to use a foam rubber, install it from the inside on the 4 sides of the landing gear leg, push it out the openings and trimmed flush to the fuselage. It would seem a simple flexible light weight way to seal the gear leg. The gear bolt access panels would be a easy access way to install the foam. I'm thinking of doing this but asking in case I am missing something.

I used some closed foam to stuff in the openings and combined that with a foam seal on the baggage compartment panel. It pretty much eliminated the exhaust fumes I had been smelling and cold drafts from behind the seats. Been flying that configuration for 3 years with no issues.

John Salak
RV-12 N896HS