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Andy_RR

Well Known Member
I'm having terrible grief with nailing the nose ribs to the main spar of my RV-8 wings.

So far, with the help of my brother we've managed to rivet the end ribs to the spar with not a huge degree of finesse, which is disappointing. We haven't even begun to attempt the "inner" ribs where the bucking bar is held at arms length through several lightening holes...

How are people doing this? There's nothing enlightening in the instructions and precious little in a VAF search. What am I doing wrong if noone else seems to be having issues with this?

Main issues are the amount of energy/time/pounding that's going into the rivets with very slow (and ultimately unsatisfactory) shop head formation. I'm doing this with the wing mounted conventionally in the frame and with the shop heads against the spar (i.e. rearwards) using a 1kg temporary bucking bar with a 470 die mounted in it and back riveting with the gun and back rivet set.

We can get the shop heads to form more quickly with increased gun pressure, but this dramatically increases the risk of the bucking bar bouncing off the other side.

I can't quite see how they can be rivetted the other way 'round since access to many of the manufactured heads from the rear of the spar with a universal rivet set would be impossible due to the proximity of some of the main ribs

What suggestions do you good folk have?
 
These are very awkward, but doable. I assume that yoiu have the leading edge structure with skin fully riveted on and one main wing skin off.
Suggestions:
1. use a 3X rivet gun, not a 2X - the 1/8 rivets combined with the stiff structure make a 2X inadequate - -I found that made a big difference in result;
2. use a bucking bar that you can position and judge orientation of by feel - I used a small rectangular bar;
3. have a mirror to check the result;
4 don't try to do it alone - have a helper (or whomever is less experienced in riveting) operate the gun;
5. I know I did not backrivet, the bucking bar was inside the leading edge structure, and the rivet gun on the manufactured head on the rear face of the spar;
6. I am sure someone posted somewhere that it was acceotabel to use blind rivets - but I didn't, and you should not have to.
Bill Brooks
Ottawa Canada
RV-6A finishing
 
I used a tungsten bucking bar taped up on all sides except for the bucking side. Set my 3x rivet gun on 52PSI and used a offset rivet set that I had to modify a bit because most of the rivet heads were too close to the wing rib. I had to grind down the rivet set a bit to get square on the rivet. Doing this helped prevent the smiley's. Also, make sure to hold the rivet gun firmly against the rivet throughout the entire operation. As Bill suggested and I agree, get someone with some bucking experience especially doing it blind. As you move to the wing skin, you will encounter "blind" bucking again.

Take your time and good luck.
 
You may use LP4-4 and/or LP4-3 pop rivets instead of solid rivets. I made so after contacting Gus at Van's who approved the substitution. Using pop rivets it's easier for a solo builder without affecting the strenght of the wing assembly.
 
Did mine solo

I did mine with the manufactured heads on the aft side of the spar so the shop heads were on the forward side of the spar. Used a 2x gun with a 12" rivet set (8" would have been better) and a tungsten bucking bar. Luckily I have small arms so I could get them through the lightening holes. The toughest ones were the rivets on the second outboard rib (RV-9A) where it is completely blind. I made a bucking bar guide out of wood and plywood to assist in keeping the bucking bar from bouncing off the rivet. Made the guide so it rested on the tie down AEX to keep it from walking outboard. In spite of the contortions the wooden guide was the real secret to this operation. Used a mirror and flashlight to inspect all rivets. Drilled out a few bad ones before I made the buckiing bar guide.
 
terrye said:
I did mine with the manufactured heads on the aft side of the spar so the shop heads were on the forward side of the spar. Used a 2x gun with a 12" rivet set (8" would have been better) and a tungsten bucking bar. Luckily I have small arms so I could get them through the lightening holes. The toughest ones were the rivets on the second outboard rib (RV-9A) where it is completely blind. I made a bucking bar guide out of wood and plywood to assist in keeping the bucking bar from bouncing off the rivet. Made the guide so it rested on the tie down AEX to keep it from walking outboard. In spite of the contortions the wooden guide was the real secret to this operation. Used a mirror and flashlight to inspect all rivets. Drilled out a few bad ones before I made the buckiing bar guide.
Click to expand...

Terrye - do you have some pictures that you could share of the wooden guide you made? I never thought of doing that but I can see a guide would come in handy.
 
Bucking bar guide for nose ribs

Hi snoopyflys,
No, sorry, I don't have a picture of my bucking bar guide and I also don't have a digital camera, but I'll try to describe it.
Base part is a piece of 2x4 wood x 6" long. Cut the width down to 2-3/8" so now it measures 2-3/8" x 1-1/2" x 6". The 2-3/8" wide face goes against the spar web. On the bottom corner router (or table saw) a cut 1/16" deep x 9/16" wide. This is for clearance on the tiedown AEX flange. In this cut I machined four slots to provide clearance for the bolt heads and platenuts in the AEX. Now measure your tungsten bucking bar and the pitch on the AN470-4 rivets between the rib flange and the spar web. I found that I had to do the operation in two parts because of the bucking bar width and the rivet pitch. If we number the rivet pattern from top of the wing to bottom of the wing 1 through 6, the first operation sets rivets 1, 3, 4 and 6. The second operation sets rivets 2 and 5. So to do this I made the actual rivet guide out of 1/8" plywood x 2" x 7" with slots in it for the bucking bar. One edge has 4 slots for operation 1 and the other edge has 2 slots for operation 2. This guide overhangs the base by a little less than the depth of the bucking bar also allowing clearance for the nose rib lightening hole flanges. It is screwed onto the top of the base piece so it can be reversed for operations 1 and 2.

For the third outboard rib in the bay with the AEX tie down, this guide assembly rests between the AEX and the rib. For the second outboard rib you need a spacer that goes beween the guide and the third outboard rib to hold it in place.

So the guide does a couple of things. It locates the bucking bar on the center of the rivet being driven (well, only if you put it in the right slot) and you can hold the bucking bar with your fingertips and it won't walk off the rivet.

Well, that was long winded, I guess I need to get a digital camera.
 
Thanks for all the tips! I haven't made any progress with this yet and it seems it will be difficult however I choose to do it.

I like Terry's wooden jig idea. I'll give this one some thought.

I'm also considering making up a bucking bar to back rivet universal rivets that looks something like this:

62569_436906647803_540947803_5417194_7211944_n.jpg


Anyone interested in one?

A
 
AN470 Back Riveting

I have only had success back riveting the AN426AD3 rivets on the control surface skins. I have found that the factory head on AN470AD4 rivets tends to back off the surface if you try to back rivet them. Had lots of fun (?!?) with this on my elevator counterweight extensions. So try it on some scrap aluminum and perfect the technique before you do it on some real parts.
 
I have had reasonable success back riveting AN470's out in the open using a spare lump of phosphor bronze drilled to accept the 470 riveting die being mounted onto it.

The problem is that the whole caboodle is too bulky inside the leading edge and also the centre of mass (and probably also the center of mass...;)) is too far away from the rivet axis. Using tungsten will allow the bar axis to be much closer to the rivet axis and still allow back riveting up close to the ribs.

I've calculated that a 1"dia. x 4" bar will be slightly heavier (900g, or about 2 pound thngs) than the "prototype" but much more wieldy. I'm sure it will also be very easy to drop onto the inside of the wing skins too...:eek:
 
just do it

Andy,
I would suggest that you are making too much of this - to form a good rivet, you need the right size hole, the right length rivet, a bucking bar held properly against the shop head, and a rivet gun (3X in this case) held perpendicular to the manufactured head. The suggestion in an earlier post to use an offset (bent) rivet set is a good one. If you use an offset rivet set, put some duct tape around the set and nose of the gun to prevent the set from rotating. Put some hockey shin pad tape (or any thick tape) over the end of the universal set to minimize marking.
Once set up, bar and gun perpendicular, right pressure, with two people, it really can't go wrong.
Special jigs, backrivetting, etc.*are clever, but shouldn't be necessary.
If one (or a few) rivets are screwed up so that the holes are enlarged, use a blind rivet for those, or a cherrymax if you want something more "structural".
Bill Brooks
Ottawa, Canada
RV-6A finishing
 
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