Tail Fairing tinnerman nuts

[Shadrach]

I’m hoping that someone might offer advice on how to finesse a tinnerman nut into position for the lowest tail fairing fastener. The correct #4 sheet metal screws were replaced with #6s years ago. I have some extra tank sealant left over and thought I’d glue the correct #4 flat tinnermans in place. I am baffled as to how they were attached at the factory. I find it hard to believe the tail fairings were mounted before the empennage was attached but I can see no access with everything assembled. 
Any advice or link to an articulating tool that might work would be greatly appreciated.

 

 

Screw hole is behind bulkhead. My five-year-old would have a hard time getting his hands back there much less articulating.

 

outside view of the bulkhead rivet line and screw hole location.

 

Top view from inside. Screw hole location is at the bottom and on the side of the dark area below the arrow.
 

[M20F-1968]

There is no reason to sweat this one.  I would look to a more permanent fix.  I would think of installing a nut plate of the type that has 2 rivets, one each on the end of 90 degree legs.  Use a floating nut plate so there is some room for error.  Lay out the holes from the outside.  Rivet with whatever small blind rivet you can use.  It is only holding the last few inches os a fairing.  Even a quality industrial pop rivet from Grainger can work.  

John Breda

[PT20J]

My ‘78 J had sheet metal screws — No tinnermans. 

My ‘94 J has A6K75 rivnuts.

[buddy]

I used rivnuts on my 201 and they worked great, easy to install.

[Shadrach]

  On 9/12/2021 at 4:20 PM, bluehighwayflyer said:

We resorted to Rivnuts on our C decades ago, Ross, and my previous J came with them already installed.  I had to replace one once because it started spinning, but otherwise have had no issues with them whatsoever.  I actually prefer their machine screws to the factory sheet metal screws.  Just another option that I am sure you have already considered.  

I love all of your factory zinc chromating, by the way.  My previous ‘78 J was the same from the factory, but my ‘65 C was mostly bare aluminum skinned internally originally.  

I’ll be interested to learn your final solution. Good luck!
 

Jim

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I had considered using Rivnuts but was not sure if they might shim the leading edge of the fairing off the skin.  My fairing has “spacers” (#10 washers) glued to the inside of the fairing (90% sure they’re factory). My bird is sort of a time capsule so I try to keep it as original as possible.  However, I think  Rivnuts are likely the best solution.

[A64Pilot]

I hate rivnuts, they eventually spin, I favor floating nut plates.

‘But if you must use rivnuts, use a type called grip nuts, they have serrations that grip the parent material resisting the eventual spin.

‘This is just to show what a grip nut looks like, that is probably just the common name

https://www.boltdepot.com/Product-Details.aspx?product=27755&qty=100&gclid=CjwKCAjwyvaJBhBpEiwA8d38vKQ7F86DBscDSAVBqBtNjOTGsOtGNa1vEMVRpeOjHHMsIWun7XJAGhoCasYQAvD_wE

of course the common rivnut is smooth barreled with no knurl

https://www.aircraftspruce.com/catalog/hapages/rivetnuts.php?clickkey=3725

Edited September 12, 2021 by A64Pilot

[Shadrach]

  On 9/12/2021 at 4:28 PM, PT20J said:

My ‘78 J had sheet metal screws — No tinnermans. 

My ‘94 J has A6K75 rivnuts.

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I wonder what the chances are that your early J had tinnermans originally. The 

My bird continues to yield loose tinnermans in the belly and fuselage from maintenance past.

[Shadrach]

  On 9/12/2021 at 5:28 PM, A64Pilot said:

I hate rivnuts, they eventually spin, I favor floating nut plates.

‘But if you must use rivnuts, use a type called grip nuts, they have serrations that grip the parent material resisting the eventual spin.

‘This is just to show what a grip nut looks like, that is probably just the common name

https://www.boltdepot.com/Product-Details.aspx?product=27755&qty=100&gclid=CjwKCAjwyvaJBhBpEiwA8d38vKQ7F86DBscDSAVBqBtNjOTGsOtGNa1vEMVRpeOjHHMsIWun7XJAGhoCasYQAvD_wE

of course the common rivnut is smooth barreled with no knurl

https://www.aircraftspruce.com/catalog/hapages/rivetnuts.php?clickkey=3725

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I think in this application it’s the only real option. There’s so little torque involved I think a dab of PRC before squeezing will likely ensure it stays put.

[PT20J]

  On 9/12/2021 at 6:04 PM, Shadrach said:

I think in this application it’s the only real option. There’s so little torque involved I think a dab of PRC before squeezing will likely ensure it stays put.

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Ross,

The A6K75 has a key on the underside of the head so it won't turn if properly installed. After drilling the correct size hole, you can make a small notch for the key with a jeweler's file. Mine have held up for 27 years of annual inspections.

https://catalog.monroeaerospace.com/item/all-categories/blind-metal-fasteners-and-tooling-1/nas1329a06k75-1

Skip

[A64Pilot]

Whether you find grip nuts or file the notch, I believe the fuel tank sealant to be a good idea, although not a structural adhesive, anyone who has tried to separate parts that have been bonded with it know it’s a tenacious adhesive, with a lot of give and flexibility.

[EricJ]

+1 on rivnuts.   That seems like a very good application for them.

 

[Shadrach]

  On 9/12/2021 at 6:18 PM, PT20J said:

Ross,

The A6K75 has a key on the underside of the head so it won't turn if properly installed. After drilling the correct size hole, you can make a small notch for the key with a jeweler's file. Mine have held up for 27 years of annual inspections.

https://catalog.monroeaerospace.com/item/all-categories/blind-metal-fasteners-and-tooling-1/nas1329a06k75-1

Skip

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I’m familiar with keyed Rivnuts. A&Ps bitch about them spinning as well... This is a low stress application so I think they’ll be fine.  It so happens that one of my hangar neighbors has a squeezer so it looks like I’m off to the races!

Edited September 12, 2021 by Shadrach

[Shadrach]

  On 9/12/2021 at 6:56 PM, A64Pilot said:

Whether you find grip nuts or file the notch, I believe the fuel tank sealant to be a good idea, although not a structural adhesive, anyone who has tried to separate parts that have been bonded with it know it’s a tenacious adhesive, with a lot of give and flexibility.

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I have some 2216 in my cabinet (might be expired). Do you think it’s worth using that?

Edited September 12, 2021 by Shadrach

[carusoam]

+1 for really low stress…

65C probably had the tinnermans held in place by a second human being while the mechanic put the sheet metal screw in place with a rubber spacer…

The sheet metal probably vibrates a touch in the wind…

The unscrewed side probably has sheet metal sliding against paint…  there is probably a nice piece of polymer to improve the contact here… clear HDPE tape.  Just a couple of small pieces on the back of the faring piece will maintain enough space to avoid contact… thus maintaining the all original image…

 

My rubber spacers looked like yellowed polyurethane, and stuck nicely to the paint… they didn’t try to escape…

Some of my tinnermans had disappeared prior to my ownership and were replaced with larger sheet metal screws…

 

Wish MS were around back then….  
 

Best regards,

-a-

[EricJ]

  On 9/12/2021 at 8:04 PM, Shadrach said:

I’m familiar with keyed Rivnuts. A&Ps bitch about them spinning as well... This is a low stress environment so I think they’ll be fine.  It so happens that one of my hangar neighbors has a squeezer so it looks like I’m off to the races!

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Most/many rivnuts don't need a squeezer.   They self-squeeze on first application of sufficient torque.

[Shadrach]

  On 9/12/2021 at 8:15 PM, carusoam said:

+1 for really low stress…

65C probably had the tinnermans held in place by a second human being while the mechanic put the sheet metal screw in place with a rubber spacer…

The sheet metal probably vibrates a touch in the wind…

The unscrewed side probably has sheet metal sliding against paint…  there is probably a nice piece of polymer to improve the contact here… clear HDPE tape.  Just a couple of small pieces on the back of the faring piece will maintain enough space to avoid contact… thus maintaining the all original image…

 

My rubber spacers looked like yellowed polyurethane, and stuck nicely to the paint… they didn’t try to escape…

Some of my tinnermans had disappeared prior to my ownership and were replaced with larger sheet metal screws…

 

Wish MS were around back then….  
 

Best regards,

-a-

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I refinished the inside of the fairings 10 or so years ago with fresh zinc and 3” polyurethane tape. It’s held up well.

 

[Shadrach]

  On 9/12/2021 at 8:30 PM, EricJ said:

Most/many rivnuts don't need a squeezer.   They self-squeeze on first application of sufficient torque.

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Up until 20 minutes ago I thought that was the only way they worked. My IA hanger neighbor implied that he had a rivnut squeezer That could be used in blind applications but I could’ve misunderstood given this was a phone conversation. 

[Guest]

  On 9/12/2021 at 8:38 PM, Shadrach said:

Up until 20 minutes ago I thought that was the only way they worked. My IA hanger neighbor implied that he had a rivnut squeezer That could be used in blind applications but I could’ve misunderstood given this was a phone conversation. 

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There are a number of pullers for rivnuts, I suppose for the 6-32 you could use a long 6-32 screw and a good pop rivet gun to set them.  If you’re worried about then lifting the panel, they do come in a countersunk version.

Clarence

[PT20J]

Here are a couple of ways to set rivnuts without a tool if you have room to work the wrenches.

https://www.youtube.com/watch?v=heLMQYwE1_o

Skip

[EricJ]

  On 9/12/2021 at 8:57 PM, PT20J said:

Here are a couple of ways to set rivnuts without a tool if you have room to work the wrenches.

https://www.youtube.com/watch?v=heLMQYwE1_o

Skip

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I've never had to use a specialized tool to set a rivnut, but maybe I've been fortunate.   I've used his first method a few times.

[Shadrach]

  On 9/12/2021 at 8:42 PM, M20Doc said:

There are a number of pullers for rivnuts, I suppose for the 6-32 you could use a long 6-32 screw and a good pop rivet gun to set them.  If you’re worried about then lifting the panel, they do come in a countersunk version.

Clarence

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If there is a gap, I think the better solution is to remove the washers that are glued to the back of the faring.

[Shadrach]

  On 9/12/2021 at 8:57 PM, PT20J said:

Here are a couple of ways to set rivnuts without a tool if you have room to work the wrenches.

https://www.youtube.com/watch?v=heLMQYwE1_o

Skip

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That was helpful, thank you. After looking at the video I think it be be prudent to make a trip to Home Depot to buy extra long hardware to set the nuts.

[carusoam]

Is there any risk of accidentally tearing/cracking the sheet metal while installing the rivnut?

Rivnuts are probably designed to not damage the aluminum…

PP question only, not a mechanic…

Best regards,

-a-

[Guest]

  On 9/12/2021 at 9:47 PM, carusoam said:

Is there any risk of accidentally tearing/cracking the sheet metal while installing the rivnut?

Rivnuts are probably designed to not damage the aluminum…

PP question only, not a mechanic…

Best regards,

-a-

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I’ve never seen skin damaged from rivnut installation.  More often the threads are pulled out of the rivnut while installing them.

Clarence

[RLCarter]

+1 for rivnuts. If you want to use an adhesive to secure tinnermans in place, thread a piece of safety wire from the outside into the hole and then up where you can get to it, slide the tinnerman onto the safety wire and apply the adhesive, next twist a loop in the wire so the tinnerman can’t slide back off, but don’t capture the nut, pull the wire from the outside and it pull the tinnerman into place, once dry pull the wire out from the inside. This works with hard/ impossible to reach places with nuts and washers, use sewing thread the same as above to hold everything in place and run the screw in, the thread gets cut fairly quick.