life span of a pop rivet

[Paul]

I recently picked up a partially completed Renegade and was excitedly bragging about it to anyone that would listen. Then an old metal fabricator friend that has built a few planes started telling me that pop rivets always come loose and aren't safe. I told him Murphy has been doing this for a long time, and I haven't heard of any problems. He just smiled and said "look into it". Does anyone have a good response to this guy or could he be right?

[Rebel541]

G'day Paul ....

The world is FULL of naysayers & doomsdayers ....... many of whom are just armchair experts ......

The short answer is HELL NO - pop rivets are just fine !

(but - just like ANY structure - everything has it's "design limitations" and limits)

Pop rivets aren't as STRONG as solids - but by using the right size (diameter) and numbers of - the overall structure IS as strong as ones using solids ......
(IE you make 'em bigger & put MORE of 'em IN - and the structure is 100% AOK)

How many aircraft are "out there" - built with pop rivets - HEAPS of them ....... and they don't just "fall apart" .....
(HELL - I've had two "hard arrivals" - and the skins tore through - but the rivets held together !!!)

Ignore the armchair experts son ...... get on with your project - and your life !

[Dale]

Paul....

The rivets Muphy uses are actually called an "Avex Rivet" and NOT a "POP" rivet.

Although an Avex rivet is a "pulled" rivet. .. It certainly is not in the same class as a pop rivet.

Finish your project with good faith in materials selected for the build.

[TongueTied]

My guess is the guy was referring to long term vibration and stress on the rivets over the course of many flying hours. Not the result of a single event causing loosening of rivets. With the Murphy aircraft, there has to be quite a few with high numbers of flying hours on them now that an issue such as this would have already arisen if it was going to. But, Biggus is right, if you put more rivets in, the stress is distributed more so each rivet is exposed to less and therefore, is less likely to weaken or loosen. Just look at the number of rivets in the Murphy designs :crazy: That is a lots more rivets than you see in most aircraft so a lot less likely for that to be a weakness. Just my $0.02 on the issue.

[Paul]

Yes, he was referring to long term vibration causing the rivets to loosen. I have heard of people taking the skin off and doing a complete overhaul on older planes. I am just wondering if that is an issue and at how many hours/years?

[Dale]

Paul....

We own Serial # 10, Renegade II. All rivets are accounted for. Currently in the midst of deciding on which material to recover her in.

[Paul]

Thanks, I'll let him know. Did any of the rivets come loose? What year was #10 finished?

[Dale]

Finished in 1986..... Replacing some tubing do to corrosion, but all rivets have done well.

[Walter Klatt]

I thought this myth was debunked 20 years ago,... certainly been a long time since I heard this question come up again... Guess there are still a few out there that don't know what Avex rivets are. Try drilling out an Avex rivet in a wing skin that was set in with chromate epoxy and I think you will be convinced.

Avex rivets will come loose in high vibration or stress areas if you use the wrong size or type, or if the area was indeed overstressed (crash or bad landing, but that is by design). And in some cases, mods are necessary. But I think the same would happen with solid rivets, if the sizing and type were done to their specs (less rivets). And in really critical spots, small bolts are used, often with fail safe designed fittings.

And do you really think Dick Hiscocks would have approved of using Avex rivets in a plane he designed if they weren't safe?

BTW, Vans now uses "pop rivets" in one of their newest planes, the RV12.

Having said all that, I think solid rivets are better (but only if the structure was designed to use them), as you would save weight, and easier to get cleaner surfaces. But then you have to deal with bucking them all, and need help for that.

[Linlei]

Hi Paul,

The onus is on your friend to come up with data to prove his statement.
There is no science behind "Smiling and saying look in to it".
Next time you talk get him to read over the Murphy manual and give specific instances
where he thinks the pulled rivets will fail. Then you have a specific area to address.
There are a heck of a lot pf Murphy airplanes flying...mine was built in 1995 and all the
rivets are accounted for.
Mike B.