Smoking rivets

[PT20J]

The original paint is flaking off my 1994 M20J. I'm going to get it painted this spring. During the annual inspection we noted some rivets on the bottom of the wings are loosening and starting to "smoke." I will replace the worst ones, of course, but I wonder if anyone has had luck rebucking rivets that are just starting to smoke.

[MikeOH]

Forgive the ignorant questions of a non A&P:

1) Can you get a bucking bar on the backside of most of them?  If not, are blind rivets allowed?

2) Anything in the FARs that allow or prohibit this?

It sure sounds a lot easier than drilling them out!

[N201MKTurbo]

It is just as easy to drill them out, clean the bore, maybe re-countersink them ever so slightly, and put in a new rivet.

My sheet metal guru. likes to drop the rivets in a Dixie cup with a little paint in it to coat the rivet with paint before setting it.

[N201MKTurbo]

6 minutes ago, MikeOH said:

Forgive the ignorant questions of a non A&P:

1) Can you get a bucking bar on the backside of most of them?  If not, are blind rivets allowed?

2) Anything in the FARs that allow or prohibit this?

It sure sounds a lot easier than drilling them out!

You can get a bucking bar in most of them, that's why there so many inspection panels under our wings.

[PT20J]

14 minutes ago, N201MKTurbo said:

You can get a bucking bar in most of them, that's why there so many inspection panels under our wings.

And that’s another issue. On later airplanes, Mooney took to pop riveting the panels that don’t require frequent removal for access to, and lubrication of, components. A lot of the Avex countersunk pop rivets are smoking and will have to be replaced. So, I might as well bite the bullet and just replace all the questionable solid ones and be sure. I’m kind of surprised there are so many. I didn’t count them, but there must be about 20 total. Maybe these were bucked on a Friday.

[EricJ]

1 hour ago, MikeOH said:

Forgive the ignorant questions of a non A&P:

1) Can you get a bucking bar on the backside of most of them?  If not, are blind rivets allowed?

2) Anything in the FARs that allow or prohibit this?

It sure sounds a lot easier than drilling them out!

Blind rivets are generally not allowed on a structural joint.    That said, you do see them once in a while in places you don't expect, but it'll be in a spot where (presumably) factory engineering determined it was appropriate.   e.g., many Mooney control surfaces are put together with blind rivets.

[Vance Harral]

2 hours ago, PT20J said:

I wonder if anyone has had luck rebucking rivets that are just starting to smoke.

I used to ask the A&P/IA who did our annual throughout our first 10 years of ownership, about our smoking wing rivets, basically every year.  We have a lot of them, but he was completely unconcerned about it, particularly given the ugly cosmetic condition of our airplane.  Finally, when I asked one too many times, he said something to the effect of, "Alright Junior, the straight dope is that if it's really bugging you that much, you can re-buck a rivet exactly one time, and it *might* stop the smoking, but no promises".  So I gave it a try, and it didn't seem to help.  For better or worse, I quit asking about it after that, which was over a decade ago.  The fact the wing hasn't come off since then doesn't necessarily mean it's OK to ignore the smoking rivets, but it's a data point.

The concept of re-bucking relies on the idea that the original installation didn't work harden the material enough to prevent it from further deformation, i.e. that there is still some "give" left in the rivet.  It also assumes the problem is a rivet that was never set correctly in the first place, rather than something else causing the rivet to move.  All of that is a crapshoot.  If you really want show-plane quality with absolutely no smoking rivets, I think you're in for a long haul of drilling and replacing, and you have to carefully examine each drilled out site to ensure the hole in excellent shape to receive a new rivet (which may not have been true even when it was built at the factory).  I've never been able to find official guidance that matches my mechanic's "you can only rebuck once" advice, maybe that was just lore.  But if true, it's irritating, since even the best maintenance logs are not going to identify re-bucking of individual rivets, especially given that the factory might have done some re-bucking themselves.

So in practice, I think it's essentially impossible to tell in advance if re-bucking is going to correct a smoking rivet or not - you're not necessarily going to have the same good/bad luck someone else had, there is too much variation in circumstance.  All you can do is try it.

[Paul Thomas]

Re-bucking is really limited to whether or not to shop head will still be in spec.

[EricJ]

40 minutes ago, Paul Thomas said:

Re-bucking is really limited to whether or not to shop head will still be in spec.

Exactly.   There are standards for what the shop head dimensions should be, and some simple go-no-go gauges to check.   If you don't wind up with an out-of-spec shop head, it can be re-squeezed or re-bucked or re-set or re-worked or re-shot or re-smashed or whatever you want to call it.    A rivet with a shop head that is already barely in tolerance of being over-worked (i.e., too wide) can't be reworked if it'll put it out of tolerance.   I think this is why a lot of people don't even bother and just drill out a suspect rivet and replace it.

It's not unusual to check existing repairs or even factory work and find rivets with bad or nearly-bad shop heads.   You can't assume any rivet can be re-shot without checking it.  

[wombat]

I've got similar problems on my plane.    Some rivets that are smoking a little, none too bad.   But also button-head pop rivets on some permanently mounted access panels on the bottom side of the wing, as well as some countersunk pop rivets on the other access panels.    

Really worried about how those will affect the paint over the next 15-30 years after I get it repainted.

[M20F]

Nicotine gum can help to quit smoking, just shape it around the rivets. 

[MikeOH]

3 minutes ago, M20F said:

Nicotine gum can help to quit smoking, just shape it around the rivets. 

Meh, that gum is pretty expensive for CB Mooney owners

[A64Pilot]

Ref shooting rivets with paint on them, by all means do so. I’ve had troublesome rivets on a fleet that I used to manage that replacing the Cherry Max rivets was a temp fix, but if we drilled them out cleaned out the hole with Trichloroethane (strong degreaser, I’m sure bad for the ozone layer) and dipped the rivets in Epoxy primer and shot them wet it was a permeant fix. Pretty sure oil or hydraulic fluid was getting into the rivets and that was allowing them to work, the primer sealed the rivet we think.

The other side of the vertical fin that was shot with solids wasn’t a problem.

Ref can a blind rivet replace a solid, yes a Cherry Max can replace an aluminum solid, but many special rivets like Monel I don’t think so, but a Cherry Max is a real PIA to remove so my advice is don’t use them unless there is no other way.

Edited November 4 by A64Pilot

[Jsno]

I would just drill them out and reshoot them.  They are working for a reason.  The Mooney Maintenance manual allows you to restrike a rivet if fuel leaks.  I haven’t had much luck because the rivet I probably hardened and you will just crack it.  As far as shooting wet, I have done that with rivets into fuel tanks.  You may even have to step up to the next size rivet.

[Paul Thomas]

You can shoot a wet rivet without enlarging the hole; most of the product ends up oozing out and very little is left in the hole. The make dimple dies that are a little bigger and I've tried them when building fuel tanks but they are not necessary.

If you are going to shoot them wet, make sure the product you use will be ok with the paint and pre-paint work.

[A64Pilot]

“Blind rivets” are any rivet that is set by pulling on a stem and that covers everything from cheap dept store “pop” rivets to Cherry Max rivets. So you just can’t make blanket statements about them as a group.

However Cherry Max rivets are a structural rivet and can replace an aluminum solid in any application that the drawing doesn’t specify a particular rivet. ( that I’m aware of anyway) Understand the drawing always takes precedence, if the drawing specifies something then that’s what you must use unless you get DER approval or similar. On edit, now that I think about it that’s not always true either I’ve deviated from drawings several times like installing nut plates where the drawing called for PK screws for example and if I had riveted on inspection covers I’d likely install nut plates and put them back on with screws too.

A Cherry Max rivet has a steel stem that when the rivet is pulled breaks off of course but there is also a steel collar that locks the stem in place, so the rivet has a steel “core” that makes it stronger than an aluminum solid, both in shear and tension although a rivet should never be put in a tension load.

However they are heavier and in my opinion uglier, a lot more expensive, often require special pullers to install, and are a PIA to drill out to remove. That steel locking ring must be removed, then you can punch out the steel stem, then you can drill the rivet. I grind the ring out of a button head one, but a countersunk one you can’t and it’s very difficult to drill out steel surrounded by aluminum without buggering up the hole, then it’s oversize rivet time.

In other words in my opinion a Cherry Max rivet is never used if a solid can be driven without excessive work to do so.

Edited November 5 by A64Pilot

[Pinecone]

I used to use stainless steel "pop" rivets on my boat.  You needed a hydraulic tool to pull them.

And they were used for some very high stress locations.  One that had me buying the tool was to install a new boom vang, that pulls down on the boom and main sail.  A LOT of stress when sailing.

[A64Pilot]

9 hours ago, Pinecone said:

I used to use stainless steel "pop" rivets on my boat.  You needed a hydraulic tool to pull them.

And they were used for some very high stress locations.  One that had me buying the tool was to install a new boom vang, that pulls down on the boom and main sail.  A LOT of stress when sailing.

I’m familiar we cruised an IP 38 and lived aboard for four years. Then my knees gave out, and Covid so I swallowed the anchor

But stainless steel in aluminum give you corrosion especially in salt water. It’s galvanic corrosion. I put Tefgel on any SS that came into contact with aluminum, it helped

Maules the sheet metal parts like the wings are built using cheap hardware store type SS pop rivets, if you look at the wings of most any Maule with a few years on it the rivets will have a ring of missing paint around them and if you look close that ring is corroded aluminum.

Cherry Max rivets of any decent size you need a Cheery Max gun, it’s pneumatic, you can shoot a couple with a good hand puller and then you’re done.

At $1,400 ea they aren’t real common for people who rarely need one https://www.aircraft-tool.com/detail?id=G704B

Huck bolt guns put them to shame though https://www.blindrivetsupply.com/hucktools.html

Edited November 6 by A64Pilot

[MikeOH]

@A64Pilot

Beautiful IP!  They are great passage makers!  I've been thinking about cruising in something 38-45 feet, but I haven't sailed in years...need to get my wife signed up for it!

[Pinecone]

I always liked the IP boats as cruisers.

But I was more into speed that could be cruised.  We were known to be doing a cruising weekend, towing a dinghy, with the spinnaker up.

[A64Pilot]

I wanted a boat that was above all comfortable and safe, hence the IP, over 40 and a boat is tough to single hand, an IP38 is actually 41’6” overall like most are measured.

The code zero really woke it up in lighter winds, but an IP just isn’t a light wind boat, too heavy, but in 6 or so kts of wind and the motor ticking over at 1200 RPM my Autoprop would have her motor sailing at hull speed and burning less than a half gl an hour and charging batteries to boot.

I carried four sails rigged, Main that was boom furling, Staysail that was my Storm sail too, 135% Genoa, and the Cruising code zero, cruising because it didn’t meet racing regs, but I was in no danger of racing my house. All sails were roller furling so I didn’t have to leave the cockpit for anything.

Speed wise towing a dinghy really slows you down more than you would believe because your dragging the thing above it’s hull speed and forget passage making towing, in any storm the dinghy will at least flip and invert, and not unlikely you will lose it. Best on deck tied down, second best on davits. I wanted a big fast RIB and I didn’t have near the deck space for that so davits was it, but they gave me room for four 250W Solar panels, I ended up being about 45 ft overall, maybe 46.

I miss cruising, if you have even the slightest inclination I say go, go now overwhelming majority wait too long and can’t. Don’t wait for the perfect boat, nobody needs a 50’  Condomoran, get a cheap 36’ boat and go if that’s all you have to spend, you’ll have just as much fun as the guy in the big Oyster, probably more really.

Edited November 7 by A64Pilot

[Pinecone]

My dinghy was an inflatable, so it was on plane when towed at hull speed, or higher, of the sail boat.

And yes, the Laser 28 would plane.  We have done 18.5 knots.

I like fast boats.  And cars.  And planes.