Solid riveting the main spar

[dbdevkc]

I have started 'smashing' the solid rivets in the main wing spar. Stressing over it quite a bit. I was at Oshkosh and got to see the riveting done on a factory assembled spar. To my eye - not much different than what I have done so far. But I went so far to measure each of the completed rivets 'upset' height and width to compare against textbook spec. This is what I have:

Spec: Height: .09375 - .0625 / Width: .281 - .203
Mine:
.092 / .232
.0975 / .223
.097 /.219
.094 / .246

I've included couple of pictures (there is a shadow at the base of the rivet that makes it look like the rivet is dumped over a bit, but they are not).

Am I overstressing about this? Are my rivets 'close enough' to spec? I am using a back rivet tool and it seems the collar is bottoming out so that is as far as it will mash the rivet.

rivet-kc-1.jpg (46.33 KiB) Viewed 5059 times

rivet-kc-2.jpg (38.43 KiB) Viewed 5059 times

[Bryan Cotton]

Kevin,
To my eye the rivets look slightly proud, meaning not squashed enough. Your measurements would confirm that. I would adjust the collar and get that extra bit of set. If you got that far you can get the rest of the way!

Solid rivets should nominally stick up 1.5 diameters before you set them, and of course their diameter starts off as 1.0 diameters. I never mic the amount they stick up. I place another rivet next to the one I am going to set. That shows me one diameter and I estimate the extra half. Same thing after I set it down to 0.5D, I measure it against a rivet. Good way to check the 1.5D width too. After a bunch/hundreds/thousands set you get a good eye for it.

If in doubt, practice on scrap! Rivets are cheap.

When I started building my RV4 tail I was a little unsure of myself. Everybody is. That only lasts a little while as long as you don't give up!

[ScottM-Sonex1629]

Kevin are you using the Sonex bolt method with 3-5lb sledge hammer or an actual 2x or 3x rivet gun? Bryan's response is helpful for the guns, but it using the Sonex recommend method you may just need to hammer harder or more blows.

They also sell very inexpensive rivet measuring gauges to let you know if it's been squashed enough. I got a set from Aircraft Spruce and it was helpful until I got the feel and eye for it.

[SvingenB]

The easiest (and fastest) is to get one of those head and length rivet gauges

http://www.aircraftspruce.com/menus/to/ ... auges.html

In general the upset diameter should be min 1.5*D and the upset length should be 0.65D, min 0.5*D The length of the shank should be 1.5*D (min 1D) outside the material before bucking it. 1.5D seems a lot if you are not used to riveting, but remember this is the minimum.

The rivet head gauges are made so you will get at or just larger than those minima, and are really easy to use. I guess it is possible to get a feel for it by just looking, but if you are as me with a dozen of near sight glasses around the hose with slightly different magnification, forget it :)

[n982sx]

I used a back riveting tool with a collar on my Sonex spar. The tool shank should not stop short of the back rivet collar. On all three back riveting tools I own - I'm now building an RV-14 - the tool head will come proud of the collar when you work it by hand. Check your back riveting tool. The collar seems wrong to me.

I find the sweet spot when riveting is to get the upset head larger than the minimum height and diameter. If you get the diameter larger than the minimum you are generally good. You don't want it so big that the rivet gets smashed lower than the minimum height.

That said, you clearly have margin to buck a little more on the high ones.

[eppre]

When I did mine I borrow a rivet gage from a friend who just finished an RV12. They take all the guess work out of the process. Aircraft Spruce has a set of them for around $20.

Pete Ellis