Convert Riveted Inspection Panel to Nut Plates

[Buckeyechuck]

I'm in the middle of a panel upgrade that includes two G5s. Tha means running wires in the right wing for the GMU 11 and future roll servo for a  Garmin 500 autopilot once it's approved for short bodies. All of the inspection panels ahead of the spar on my '62C were riveted. I've removed 8 of them leaving only the ones where the fuel tanks (O&N bladders) are. I'd like to convert these to nut plates. Is there any reason I can't? Also since these were round head cherry rivets, any reason I can't use a round or panhead screw, it would save having to dimple the holes in the wing.  My IA thought it would be a good idea to get some feedback from this group. 

[RLCarter]

I would dimple them, but then again it might just be an excuse to buy the dimples dies 

[0TreeLemur]

I vote dimples.  All inspection plates on our '67C are dimpled.

[Guest]

There should no issue with changing from rivets to screws, you’re just allowing easier future inspections.  Mooney has used many fastener variations over the years, rivets, round head screws, countersunk screws, internal and external covers.

Clarence

[jaylw314]

I don't know how helpful dimpling the inspection panels would be, unless you had a true dimple die (not just the little dimple sets).  When you use dimple sets, you make two identical dimples and these don't actually sit correctly together--the sheets become separated by a gap, with larger dimples giving you a larger gap.  In addition, the dimpling tends to buckle the surrounding area up a little. 

With a rivet line near the edge of a sheet, you actually have to bend the edge down a little to get the edge to stay flush to the adjacent sheet.  On a small inspection panel, that's harder or impossible to do, so I suspect you'll end up with a noticeable gap between the inspection panel and the surrounding skin.

One solution might be to use a slightly larger dimple on the inspection plate than on the skin, but I don't know if that's something you want to experiment with on your own plane...

[Guest]

There are dimple dies meant for all sizes of Aviation screws that I’ve encountered.

Clarence

 

[Buckeyechuck]

Thanks for the feedback.  I do have access to a rivet squeezer with dimple dies.  I'm finding out there is more to this than I ever thought. For instance, if I'm dimpling the inspection plate and the holes in the wing, are there offset nut plates that conform to the dimples?  How are those spec'd.  I'm planning to use no. 6 screws (heads to be determined), no. 40 flathead rivets for the nut plates, which means countersinking very thin plates.  I have the tool for that as well.  

I really appreciate this forum.  I'm sure I would not be into this major work and cost without the renewed interest I've gotten from all of you.  

 

 

[Yetti]

Why not do them like the fuel tank plates so they are smooth flush.  two layers of alum. 

[Guest]

9 hours ago, Buckeyechuck said:

Thanks for the feedback.  I do have access to a rivet squeezer with dimple dies.  I'm finding out there is more to this than I ever thought. For instance, if I'm dimpling the inspection plate and the holes in the wing, are there offset nut plates that conform to the dimples?  How are those spec'd.  I'm planning to use no. 6 screws (heads to be determined), no. 40 flathead rivets for the nut plates, which means countersinking very thin plates.  I have the tool for that as well.  

I really appreciate this forum.  I'm sure I would not be into this major work and cost without the renewed interest I've gotten from all of you.  

 

 

You’ll need to buy nut plates with dimpled rivet holes as well, you can’t countersink the very thin skin of the inspection covers.

Clarence

[jaylw314]

14 hours ago, Buckeyechuck said:

Thanks for the feedback.  I do have access to a rivet squeezer with dimple dies.  I'm finding out there is more to this than I ever thought. For instance, if I'm dimpling the inspection plate and the holes in the wing, are there offset nut plates that conform to the dimples?  How are those spec'd.  I'm planning to use no. 6 screws (heads to be determined), no. 40 flathead rivets for the nut plates, which means countersinking very thin plates.  I have the tool for that as well.  

I really appreciate this forum.  I'm sure I would not be into this major work and cost without the renewed interest I've gotten from all of you.  

 

 

You can dimple the skin on the inspection plate as well as the rivet holes on the nutplate with the dimple dies.  It will take more effort to dimple the nut plates--you'll need to grind off part of the female dimple die to allow it to clear the center section.  Sorry, I'm away from my toolbox so I don't have pictures, but it'll make sense when you have them in hand.

I don't believe there are standard nut plates that you can buy that are already dimpled for flat head rivets (I might be wrong on that, though).

[Guest]

You need MS21049L08K nutplates, for 8-32 countersunk screws with countersunk rivets.

Clarence

[jaylw314]

1 minute ago, M20Doc said:

You need MS21049L08K nutplates, for 8-32 countersunk screws with countersunk rivets.

Clarence

Holy cow!  That would have saved me a lot of time on the RV project! 

[Guest]

1 minute ago, jaylw314 said:

Holy cow!  That would have saved me a lot of time on the RV project! 

Checkout www.monroeaerospace.com

Clarence

[Aerodon]

I would use click bonds, my preferred supplier is:

https://www.theflightshop.com/c.Click.Bond.Authorized.Dealer.html

Expensive, but a lot easier to do in your situation.  Make sure you prep the surface to get a good bond.

 

Aerodon