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Burndout11 11-18-2017 06:46 PM

Vertical Stabilizer help
Pretty much at the end of my rope here. When riveting the nose rib and root rib to the front spar, I canít seem to get the rivets to set right. Iíve now had to re-order the parts twice after enlarging the holes when drilling out the rivets. Iíve been bucking them with the gun after not being able to get the squeezer with a 3Ē yoke in there. Iím using the correct rivets that are called out in the plans yet my rivets are folding over or the flange on the rib is flexing and creating a gap between the rib and spar flanges. Been using a CP 3x gun at 55 psi with a tungsten bar. Only set I can get on the head is the offset.

Looking for some ideas, suggestions etc... how has everyone else set these rivets? Maybe a different yoke on the squeezer? Any help is much appreciated.


Aluminum 11-18-2017 07:14 PM

55 psi sounds too high for the 3x. I creep up on mid-30s with my 3x for -4 rivets. Nothing should be bouncing.

Use several short bursts until you get comfortable, reposition the gun and bucking bar between bursts.

Burndout11 11-18-2017 08:49 PM

Seems like I have to set it at 55 psi or the 4-6 rivets wonít set at all.

bkervaski 11-18-2017 08:51 PM

My 3x is set at 35psi for those ... at 55 I would be destroying rivets and skins.

BobTurner 11-18-2017 08:55 PM

How heavy is the bucking bar? For AN4 rivets you want a pretty heavy one.

Burndout11 11-18-2017 08:58 PM

Right around 2 pounds

HAL Pilot 11-18-2017 09:07 PM

If the rivet has a bit of wobble from being drilled out I take the next one and pre squeeze it just a hair to fatten it up and make a snug fit. this takes a few extra rivets to get one straight fat one. then put it in the hole.

also I got some real small O rings from the hardware store and put them on the rivet. this forces the flange under it to compress when your put the bucking bar on it.

Tom023 11-19-2017 02:55 AM

I know those rivets well. The issue I had were also clenched rivets. The parts being rivited are at angles other than 90 degrees making it difficult to hold a bucking bar correctly. I taped some plastic shims to my tungsten bar to keep it in proper alignment just by holding it against structure. Works well in other areas with angled pieces like the inner nose ribs on the horizontal stabilizer.

VNS 11-19-2017 03:41 AM

Sounds like you are applying all the force from the gun straight through to the bucking bar. You should set up the job so the gun provides pressure on the rivet countered with the rib and skin pressed together and only a light touch on the job end of the rivet with the tungsten bar. A third hand helps or try using clamps or your thumb and index finger to press the job against the gun and hold the bar with the other fingers. You need very little pressure on the bucking bar but don't let it bounce.

MED 11-19-2017 06:20 AM


Originally Posted by HAL Pilot (Post 1219825)
also I got some real small O rings from the hardware store and put them on the rivet. this forces the flange under it to compress when your put the bucking bar on it.

Instead of o-rings, get a piece of small diameter tubing - with the ID about the same size as a rivet. Then, you can cut off an unlimited supply of "o-rings". 🤗

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