Squeeze universal rivet between two cupped sets?

filipo · Post by **filipo** » Wed Mar 22, 2006 11:06 am

Is it possible to squeeze AN470 universal rivets between two cupped sets and achieve a shop head that resembles the manufactured head?

If it's possible, is there a special set to be used for the shop head?

Thanks.

cjensen · Post by **cjensen** » Wed Mar 22, 2006 11:12 am

filipo!!

i'm not sure of the exact reason, but i don't think it should be done. i'm sure it can be done, but you're changing the composition of the metal when you squeeze a rivet, and the formed shop head is the strongest in it's flat set form. i would guess that a universal shaped shop head will not exhibit the same shear strength as the flat squeezed head. also, i think it would be awefully difficult to get a centered squeeze with a cupped set, and the rim of the cup would have to go right to the surface of the aluminum which sets up the good possibility of marring the surface.

just a few thoughts off the top of my head. good question! welcome to rivetbangers!!

captain_john · Post by **captain_john** » Wed Mar 22, 2006 9:58 pm

Omar... not a "standard" technique. These thibgs are best left "standard".

...I am guessin' it probably isn't "bad", but this is a time tested technique steeped in tradition. Why mess with perfection?

CJ

Dan A · Post by **Dan A** » Wed Mar 22, 2006 10:26 pm

I did it all the time. There isn't any reason you cannot use cups on both heads. In fact it makes the shop heads look much better. Strength wise it's the same either way. I set all my flush rivits with a flat set on the flush side and the cupped set on the shop head side. Try it, You'll like it!

Dan

tshort · Post by **tshort** » Thu Mar 23, 2006 11:14 am

I'm not so sure about that idea .... someone with more specific knowledge than me could speak up, but the criteria that define the shop head as acceptable or not are based on the ratio of the height to the diameter and depend on the rivet size. I would post links but I am on my brother's dial up in CO and it would take 30 minutes

.

Basically, I would be concerned that the strength of the rivet might not meet design specs if the shop head is "malformed" - i.e. cupped, sides not vertical, etc. The manufactured head is made that way; crushing the other side to look like that does not likely achieve the same results in terms of strength, etc.

YMMV, but I would do it the way that AC43.13 specifies.

Thomas
-8 wings

Marine · Post by **Marine** » Fri Mar 24, 2006 7:30 am

My tech counsellor who is a NADEP Airframes technical guy for the Marine Corps indicated that it is perfectly acceptable to use a cupped set on both sides of a rivet.

That said, I wouldn't do it on every rivet, nor would I do it only for cosmetic reasons.

filipo · Post by **filipo** » Mon Mar 27, 2006 11:31 am

I tried it, and the result was moderately unacceptable on a piece of scrap aluminum. I think the problem was that my two sets are not identical in shape - one has some extra flat area around the cup, while the other doesn't and it seems that this deforms the skins slightly. The shop head didn't form a perfect cup either - it has a convex top, but still has a little bit of a "straight wall".

Next on the agenda is to get another cupped set, identical to one of the two I already have with my next order from Spruce or Wicks, and try again.

Someone has also suggested using the softer "A" rivet, not "AD".

cjensen · Post by **cjensen** » Mon Mar 27, 2006 3:22 pm

are you wanting to do this for cosmetic reasons?? i really don't see any advantage to running through a series of trial and errors to perfect it, unless you are building a show plane and want a "prettier" shop head.

just curious...if it works out, let us know!

dan will probably be a bigger help than the rest of us...

filipo · Post by **filipo** » Mon Mar 27, 2006 10:57 pm

Yes, it's purely cosmetic on a GlaStar rudder trailing edge.

jim_geo · Post by **jim_geo** » Tue Mar 28, 2006 12:31 am

Filipo you need to do your trailing edge the way we do our 7's 8's and 9's here buddy.

filipo · Post by **filipo** » Tue Mar 28, 2006 12:48 am

How's that?

JohnR · Post by **JohnR** » Tue Mar 28, 2006 1:03 am

My 7 has an AEX wdge which you counter sink and then dimple both rudder skins. After that you use proseal or epoxy and cleco the trailing edge together then wait for it to setup. Once setup you use double flush rivets. This is done using a flush rivet and setting the shop head side in the dimple on the other side. It really is pretty simple and looks good also. Keeping it straight is the hardest part but it isn't that bad if you use a long backing plate.

Not a real good explanation but you should get the general idea.

I don't think it would work on a Glastar though!

(just kidding)

filipo · Post by **filipo** » Tue Mar 28, 2006 1:13 am

That sounds like a good way to do it.

The normal procedure on the Glastar is to apply epoxy at the trailing edge between the two skins, clamp between two straight edges and rivet with universal rivets after the epoxy has cured. The epoxy helps keep the edge straight.

I think doing it the RV way would work just fine.

jim_geo · Post by **jim_geo** » Tue Mar 28, 2006 2:11 am

I'll try to post some pix of the finished product soon. That is unless someone else beats me to it.

filipo · Post by **filipo** » Tue Mar 28, 2006 9:57 am

Found a couple pictorial descriptions:

http://home.teleport.com/~dianas-rv9a/C ... gedge.html

http://home.valornet.com/itworks/sewing_it_up.htm

cjensen · Post by **cjensen** » Tue Mar 28, 2006 10:08 am

man! you guys were up late last night!

night owls...

filipo · Post by **filipo** » Tue Mar 28, 2006 10:11 am

Sleep is over-rated.

jim_geo · Post by **jim_geo** » Tue Mar 28, 2006 12:59 pm

I was up changing chemistries in the lab last night anyway.

prestwich · Post by **prestwich** » Tue Mar 28, 2006 1:11 pm

jim_geo wrote:I was up changing chemistries in the lab last night anyway.

Is that rivetbanger code for "setting up the still for a fresh batch of white lightning?"

TomNativeNewYorker · Post by **TomNativeNewYorker** » Tue Mar 28, 2006 8:03 pm

Marine wrote:My tech counsellor who is a NADEP Airframes technical guy for the Marine Corps indicated that it is perfectly acceptable to use a cupped set on both sides of a rivet.

That said, I wouldn't do it on every rivet, nor would I do it only for cosmetic reasons.

I worked 13 years as an aircraft sheetmetal mechanic at two seperate NADEP's and I never saw cupped sets on both sides.