Help finding article about rivet strength from Van's

Some time in the past year, either in an RVator or elsewhere, Van's printed an article about how strong even poorly set rivets are. Haven't found it in the few RVAtors I can find at home and don't see it here on the forums. Anybody know what I'm referring to and have a link or citation for it?

Every once in a while ( ) I set a rivet less than perfectly and wonder whether I should replace or leave it since it is probably already more than strong enough. Reading the article might help me decide.

Thanks.

Rivets - good and bad

Alpine(?)
One issue is defining what actually is a bad rivet. I've noticed builders sometimes fix rivets that meet specifications...

A some definitions are here on my web site....

http://home.earthlink.net/~gilalex/rivet_spec/rivet_a.htm

I think Van also published the dimple vs. countersink rivet shear strength data I posted on the Matronics RV-list a long time ago.... (11 years ago....)

http://www.matronics.com/searching/...HITNUMBER=6?SERIAL=2317091368?SHOWBUTTONS=YES

and here....

http://www.matronics.com/searching/...HITNUMBER=7?SERIAL=2321402435?SHOWBUTTONS=YES

gil in Tucson

Here's a really interesting read, a study conducted by my fellow SoCal RV builder/pilot Bill Marvel (also a Lycoming guru). He did a bunch of tests with properly set rivets, under-set rivets, and over-set rivets:

http://www.kilohotel.com/rv8/rvlinks/marvelrivets.html

alpinelakespilot2000 said:

Some time in the past year, either in an RVator or elsewhere, Van's printed an article about how strong even poorly set rivets are. Haven't found it in the few RVAtors I can find at home and don't see it here on the forums. Anybody know what I'm referring to and have a link or citation for it?

Every once in a while ( ) I set a rivet less than perfectly and wonder whether I should replace or leave it since it is probably already more than strong enough. Reading the article might help me decide.

Thanks.

Click to expand...

I can't recall it offhand but if it was in the RVAtor, it'll be listed in the RV Aviator index

in 24 years of the RVator

I found the article that you were looking for in 24 years of the RVator (which I think that everyone should have). It is under the hardware section on page 24. The article was writen by Alcoa, who makes the rivets. Basically, the article said that underset, deformed, and cracked rivet heads all had tensile strengths within 5% of "ideal" heads. In other words, drilling out and replacing a less than perfect rivet is usually not necessary or desireable.

Construction Manual, Section 5.

I believe what you are looking for is included in the latest revision (s5r9 12/08/05) of Van's Construction Manual, Section 5: Construction Materials, Processes, and Useful Information. An "EXCERPT from Alcoa Aluminum Rivet Book" has been added on the bottom of page 5-3.

To quote from the text: "It has been determined that even badly cracked heads are satisfactory from the standpoint of static strength, fatigue strength, and resistance to corrosion. (Poorly set and cracked) rivet heads were tested in tension to determine how well formed a head has to be in order to develop full strength. The tensile strength of all the rivets were within five percent of the strongest. The test indicated that minor deviations from the theoretically desired shape of head are not cause for concern or replacement. The second rivet that is driven in any one hole is likely to be more defective than the first because the hole is enlarged..."

Dave Cole
RV-7 wings

All great information. Thanks. I think it must have been in December when someone posted that Alcoa report from the new Section 5 of the manual. My section 5 doesn't have that.

The rivets that made me think this time were under the tailwheel mount where the tailcone skin and the last two bulkheads meet... these rivets were really hard to buck, both with the curving of the skin and the existence of the tailwheel mount. A couple of my rivets had shop heads that were a little tipped--not under or over set, just tipped some. What I wonder is, at what point is a shop head "too" tipped?

alpinelakespilot2000 said:

A couple of my rivets had shop heads that were a little tipped--not under or over set, just tipped some. What I wonder is, at what point is a shop head "too" tipped?

Click to expand...

When you can see the edge of the hole from the shop head side.... Tipped is OK, but it should cover the edge of the hole for 360 degrees.

Quoting Mil-Spec.... Alcoa is probably different...

gil in Tucson

Thanks Gil. If that's the case, then I have very few rivets on the plane that are a problem. That's good news. Sometimes it is hard to know whether you are seeing the edge of the hole or just part of the hole that was stretched in the dimpling process. Your link to the rivet specs was very helpful as well. Appreciate it.