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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 can?t seem to get the rivets to set right. I?ve now had to re-order the parts twice after enlarging the holes when drilling out the rivets. I?ve been bucking them with the gun after not being able to get the squeezer with a 3? yoke in there. I?m 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.

Tommy
 
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.
 
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.
 
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.
 
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". 🤗
 
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". 🤗

That's what I do - bought a couple different diameters of aquarium type tubing on Amazon - easy to fully drive rivet with these in place while pushing pieces together.
 
clamp it

When I first started a number of riveting troubles were caused by the parts not being clamped or secured very well. If the part is wobbling around and you are trying to support it, use the bucking bar and rivet gun... well, it doesn't work too well. If the parts are clamped and secured, you can see how everything lines up and you can get the bucking bar square to the rivet, then things go a lot easier.
 
on keeping the 'stack' tight:

Many things work; o rings, tubing, etc.

I use various thicknesses of rubber/neoprene sheet. I cut a small piece; ~1/2" square is usually plenty. I drill a hole near the edge using the same drill I'd use for the rivet hole. Then cut from edge into the hole using scissors or wire cutters. The hole ends up smaller than the rivet, but will slip over the rivet tail easily. I use a thickness that's roughly equal to tail length that's exposed when the stack is tight. A short burst with the gun will clinch the stack, then the rubber is removed & setting is finished.
 
A rivet should be stet with as few as possible blows from the gun. If not it will work harden to the point it will fail and pop the head off. That was a fellows problem on here a few months back. He could not figure out why it was happening thought it was bad rivets.
Just a thought when driving them. Boyd in Chiloquin Or
 
rivets

Hi Tommy, I am in Shafter and may be able to help. No expert but have completed a RV6A and currently working on RV6. Call if you want another opinion and/or help. 661 865-3529
David
 
On my VS I used my hand squeezer with the handles on the aft side of the front spar. I put the rivets in with the manufactured head on the front side. I think I had to bend the nose rib upward a bit in order to get the yoke onto it but not too much. One nice thing about the hand squeezer is you can go slowly (compared to pneumatic squeezer or rivet gun) to better control setting the shop head on the aft side of the spar, and by pulling the handles of the squeezer aft you can keep enough pressure on the manufactured head to keep the nose rib flange flush to the spar, no o-rings or other gadgets required...
 
When I had my fin inspected by the MDRA (Canada) I had a bit of a gap between the rib and the spar. They snagged it and I sent a picture to Vans. they answered that the purpose of those rivets was simply to hold the rib in place and that the loads were transmitted to the spars mostly via the skin. So, if you have the rib not lying down tight to the spar it is not a strength issue, it is only a "fussiness" issue. :)
 
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