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Rolling Edges, Breaking Edges, Whatever You Call It

dwollen89

Well Known Member
I'm getting close to riveting on my wing skins. I know that edges should be rolled on overlapping skins. However, I have a couple questions and can't seem to find an answer. Should your roll the edges for butt joints? For example, where the wing skins/leading edge/fuel tank skins butt up to each other? I rolled the edges on my fuel tank skins and the leading edge skins because I figure it can't hurt. However, I haven't riveted them on yet so hoping it wasn't a bad decision. If the skin ends at a flange, isn't that basically a lap joint? I didn't roll the trailing edge of my rudder skin and it didn't lay flat when I riveted it, so I don't want to repeat that.

I'm looking for some thoughts and feedback on what others are doing.

Also, for multiple layers, should your roll the edges on all layers? For example, the wing walk doubler.
 
Like you experienced with your rudder, you'll find that the edge of a riveted skin will "relax" (actually swell) from the expansion of the driven rivet and this may cause it to "lift."

Rolling the edges is a "good thing"

Best prep is getting new AD (read "soft") rivets, or annealing them just prior to riveting. (This step is technical and exacting, made easier with digital temp controllers).
 
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Be careful not to confuse “soft rivets” with actual soft rivets. Our aircraft use AD rivets, which are hard. We never want to use soft “A” rivets on anything structural. Some people use soft “A” rivets on fiberglass parts. The above post must mean “soft rivets” as in newly made and not 20 year old rivets that may have hardened over time. I don’t even think our AD rivets harden over time compared to younger, fresh rivets, but some people say they do.
 
You only need to "break" the edges on skins that overlap. If the skins butt up against each other, you don't need to do this. The slight break ensures that the skin edge is pulled flush with the skin it is sitting on. Go easy on the edge break. A little bit is all you need. Too much break and you have effectively added some stretch to the material and you can get some pillowing when you pull it tight with a rivet.
 
Before dimple

It seems to me to best to roll the edge before dimpling. I forgot to do it on a few skins before dimpling and they didnt come out as good. It should be very subtle, barely detectable.
 
Re - Post #2

Make sure you understand the difference between annealing and solution heat treating.

Annealing permanently softens the material being treated. Not a good thing re/the rivets we use for our builds.

Solution heat treatment temporarily (through careful application of precise heat settings), softens the rivet and increases its ductility. All of the rivet's original characteristics are returned through work hardening (the act of "bucking") & age hardening (naturally about 96 hours).

Annealing is a no no, and solution heat treatment should be left to those with the knowledge & equipment to do it properly.

If you are ever concerned about the condition of your rivets (prior to driving), a good rule of thumb is to turn one over, head down, on the top "face" of your vise, or on your back riveting plate and give it a (very) sharp rap with a large enough hammer to sufficiently deform the rivet for inspection. Upon doing so, if, when inspecting the head side, radial cracks are visible - the specimen is too brittle and not suitable for "driving".

YMMV - but shouldn't.

HFS
 
I consulted three NACA reports on Rivet aging and the description of the process I used, obtained from from the Alcoa Rivet Guide, and AMS Handbook #4, matches the point raised by HFS.

In the 70's, "new" rivets were delivered to Fullerton Air Parts on Thursday, about noon.

Rivets "fresh" from mfg, took 40-45 psi and about 4 (trigger tickle) rivet gun hits, (sounding like, "plop, plop, plop, plop) delivered a textbook shop head.

By Saturday, the pressure was 80 and the rivet was driven with a short pull, (brrrrrrttt!).

I tried driving a really old, long, AD-4 rivet (2") and it sheared at an angle with no appreciable swelling of the shank.

In any case "First Day" rivets did not appreciably swell the skin.

FWIW/YMMV
 
I consulted three NACA reports on Rivet aging and the description of the process I used, obtained from from the Alcoa Rivet Guide, and AMS Handbook #4, matches the point raised by HFS.

In the 70's, "new" rivets were delivered to Fullerton Air Parts on Thursday, about noon.

Rivets "fresh" from mfg, took 40-45 psi and about 4 (trigger tickle) rivet gun hits, (sounding like, "plop, plop, plop, plop) delivered a textbook shop head.

By Saturday, the pressure was 80 and the rivet was driven with a short pull, (brrrrrrttt!).

I tried driving a really old, long, AD-4 rivet (2") and it sheared at an angle with no appreciable swelling of the shank.

In any case "First Day" rivets did not appreciably swell the skin.

FWIW/YMMV

Were these AD Rivets that we use? There are other types of rivets that age harden I believe they call it.. I didn’t think our “AD” rivets age harden.

Edit: found this online:
Alloy 2117 rivets retain their characteristics indefinitely after heat treatment and can be driven anytime.
 
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Yes on all.

Most important
Buy good roller from Cleveland Tool
Vice grip style roller only.

Boomer
 
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