Riveting the Left Wing Main Ribs

We had a warm day and I took advantage of it to get the left wing’s main ribs primed.

I used a different method of metal prep for priming that saved me a lot of time. Instead of scuffing and acetone-cleaning each rib prior to priming (the method I’ve used up until now), I used PreKote to prep the metal and then a water rinse for cleaning. I was able to prime all 14 ribs in one four hour session. This would have taken several days using the old method. When I do the right wing, I’ll try to photo-document the process to show here.

Once the ribs were fully cured, it was time to assemble the main section of this wing. I began by assembling the section using clecoes to make sure everything fit correctly.

The instructions say to put tape along the heavy spar bars to protect them from damage while setting the upper and lower-most rivets.

Almost all of the rivets in the main spar need to be set using the rivet gun and a bucking bar. The spar is much too large to accommodate a squeezer yoke.

Because the rivets are very close to the webs of the ribs, I’m using an offset rivet set to reach them.

Notice the jog at the tip of the set. This is the offset that makes it possible to reach rivets that are right up against a surface. After bucking a couple of rivets, I noticed that the offset set rotates as the rivet gun hammers. This was defeating the purpose of the offset and causing less-than-perfect results. I found that wrapping a couple of rubber bands around the shaft right where the retention spring sits kept it from turning.

If I was riveting with a partner, I could use two hands. One to hold the tool and the other to hold the set to keep it aligned. But, I’m solo riveting and I need the other hand to hold the bucking bar. Here’s how the tool is applied to a rivet head. I’ve been putting a small piece of tape over the rivet heads to protect their finish during riveting.

Here are a the factory heads of the rivets after being set. I put the factory heads on the side with the thinnest metal. In this case it’s the ribs.

The shop heads, formed by the bucking bar, are on the spar side.

After setting all the rivets in the main spar, I moved to the rear spar and started riveting the rear of the ribs. There are holes that still need to be left open to allow for later attaching of the flap brace and aileron gap fairing.

On the outboard rib, flush rivets need to be used. This is because the outboard aileron hinge bracket will be attached there and big round rivet heads would get in the way.

The last task in assembling the wing section is to bolt on a temporary bracket to hold the outboard end of the wing to the wing stand. I drilled two holes in the rib to hold the bolts. These holes will not cause any structural problem with the wing later.

It’s now time to put the wing on the stand! I’ve measured and placed the stands at the correct distance and bolted them with strong concrete anchors to the floor. Here’s the left wing in its stand.

Once the wing was secured on the stand, I adjusted the threaded rods to get everything level.

The center of the wing sags down from its own weight. I put a piece of 4×4 and a pair of wood shims to adjust the lift on the center. With the wing supported and straight, the skins will attach easily.

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