Rivnuts question

[Tankerpilot75]

I?ve ordered some new oil and fuel hoses from TS Flightlines in preparation for my next CI. Replacement of my oil pressure sensor hose has me a little concerned. It runs against my firewall and is secured to it with two adell clamps with (I think) AN3 bolts running through the clamps and firewall with locking nuts on the inside. Getting to the nuts on the backside is going to be next to impossible but I think I can place a channel lock wrench on them and remove the two bolts. However reinstalling those two nuts and bolts will be impossible due to impossible access.

I?m thinking about putting two Stainless steel rivnuts in their place but I have some concerns about slippage when reinstalling the adell clamps around the new oil pressure sensor hose against the firewall. Have any of you done this and if so how has it worked out?

I could possibly install anchor nuts instead but I would have to use pull rivets. What?s the community think? I?m not the builder but have worked extensively on this RV.

[terrye]

Don't think rivnuts are a good idea:
1. Firewall is VERY thin
2. There are plain rivnuts and rivnuts with anti-rotation keys. Even a SS rivnut with anti-rotation keys will probably turn as the bolt is tightened
3. Rivnuts are not self locking

Depending on how far the adel clamps are, I would consider riveting platenuts to a .040-.063 thick aluminum plate. Then tape the plate temporarily in place on the back of the firewall, enough to start the bolts. Tighten bolts, remove tape.

[sjhurlbut]

Ever consider clickbond nutplates? A perfect application of what you're asking just make 100% sure to prepare the surface properly.

Firewall is too thin for rivnuts/nutserts.

Or just go with screws and nuts. If you ever need to remove them (rare) ask a friend to hold a screwdriver.

[azonic75]

I think if you can get a channel lock on the nuts to get them off....you can reinstall them.

Place them on a closed end wrench with a little tape holding them in, get the bolts just enough to engage the nut and start tightening

Finding someone to lay on their back under the panel will be the hard part.
Find someone who has bucked the turtledeck rivets in the back of an -8!

k

[Tankerpilot75]

Thanks for both of your suggestions. I think either of your approaches is better than the rivnuts or my original anchor nut approach. I?m not so sure that getting access to reinstall the nuts the same way I?ll have to use to remove them is too realistic given my age and general overall intolerance to being on my back in a cramped environment for very long. However, if I can get those nuts off who knows what possible when it comes to reinstallation.

I?m replacing my hoses with wire covered Teflon hoses from TS Flightline because I want to minimize the probability of having to repeat this process again during my tenure of remaining ownership. And hopefully when it comes time to sell, the purchaser will be satisfied that I went the extra mile to ensure quality products and materials were installed.

[rv8ch]

I used a few rivnuts here and there, but would avoid them in the future. My 0.02 USD.

[climberrn]

Could use pop rivets on regular nutplates to firewall. Also, I have riveted nutplates to a strip of 1/2” aluminum, and bonded it to the surface.

Agree with above. Rivnuts would not be a good idea on a SS firewall. Have used Clickbond fasteners on several locations. They are an awesome product but not cheap, and not fun if they spin in an inaccessible area! The regular nutplates on a strap of aluminum tied to at least 2 holes can’t slip.

Sorry, post #2 covered this.

[koupster]

I've just completed the installation of two nutplates on a strip of sheet metal that was then fished into a small space with no direct access from the backside. However, I was able to see when the first nutplate lined up with a hole, install a screw loosely, and rotate the strip until the second nutplate lined up with the second hole.

Given your situation, I would lay out nutplate holes from the engine side. Then put some matching threads on a piece of stiff wire either by threading the end of the wire or brazing on a machine screw with head cut off. Pass the wire with the threaded end through into the cockpit, and thread the nutplate loosely onto it. Pull the wire back from the engine side, rotate clockwise until the nutplate attach holes line up, and fasten with steel pull rivets. Repeat for the second hole.

Age and general overall intolerance to being on one's back in a cramped environment can sometimes be overcome by skill and cunning.

Cheers, David
RV-6A KBTF

[abwaldal@gmail.com]

I have used Rivnuts in the long ago past and I can tell you if you had been in my shop 8-10 years ago you could have watched as I chucked the tool, parts, and everything in the trash. I will never use them ever again. My 3 cents worth. Inflation Art