August 4, 2007

Finished cleaning ribs, Priming, riveted left wing skeleton - 11.0 hrs.

Today was a huge day, with a lot of visible progress accomplished. I started where I left off yesterday, cleaning and scrubbing the rest of the ribs. They dried quickly, and I proceeded to prime them all. This was a perfect day for this work. Sunny, warm, about 75 degrees, and a very light breeze.

After the scrubbing operation was finished, I cleaned everything up and pulled out my chicken-wire priming frame again. I was able to lay out about 10 ribs at a time, as you can see above. So I did batches of about 10 until I had them all primed.

The primer dried quickly enough that I was able to turn them over almost immediately and spray the other side. Then I moved them onto the bench behind the table and stacked them with others previously primed while I did another batch. This whole job went quickly with no problems. It took almost a whole quart of primer to do all the ribs.

Now, after cleaning everything up, I took the ribs back to the shop for the moment I've been waiting for for nearly a month. Here you see the ribs being clecoed onto the main spar for the last time, in preparation for riveting.

The rear spar isn't clecoed on yet. You want to rivet the ribs to the main spar first, and it's easier to rivet if you can gently bend each rib to the side and allow a straight rivet set to be used straight-on. The riveting method I'm using is one I saw described on Dustin Bolton's website. Thanks, Dustin! It's a "stationary bucking bar" method. The idea is to put the spar up on blocks at a height just right so your largest bucking bar can slide underneath, leaving about 1/4" clearance under the rivets. You use shims and different sized blocks to get it just right. You can see my big bucking bar on the far left in the picture above, standing up on end. Rivets are now inserted in the holes. I put tape over each rivet head to avoid marring, and I wrapped the rivet gun in a shop towel to prevent it from scratching up the freshly primed ribs.

Here's another shot of the process. The idea is to slide the bucking bar under a rivet, press down on the rivet gun until the rivet tail contacts the bucking bar, and then hammer away. The spar will flex enough to allow you to do this. If done correctly, it's kind of like back riveting, and produces perfect rivets every time. Plus, it's a one-man operation! No help needed. You can also see that I put some masking tape on the side of the bucking bar, to help prevent scratching the stiffener plate on the underside of the spar. Some of the rivets are very close to this stiffener.

Check it out... perfect rivets! Aren't they purdy? Not a scratch, ding, smiley, or bent shop head underneath. I have to confess, however, that not all of mine came out perfect the first time. I had to drill out a few of them when I ended up with smilies on the rivet heads. This happens when you don't push down hard enough (or you don't have enough flexure) and the rivet isn't in firm contact with the bucking bar underneath. The rivet gun will bounce off the rivet head and make a mess of it. Fortunately, the damage was only to the rivet head (not the rib or spar) and I was able to carefully drill them out and do them over. Then they came out great. Go carefully and take your time and this won't happen. The results are worth it! I'm very pleased.

Once they were all done, I moved the assembly over to my little workbench. It was time to cleco the rear spar in place and rivet it together. I switched from the rivet gun to the squeezer. I'm squeezing the rivets in place in the photo above. All the rivets on the rear spar can be reached with the squeezer and a longeron yoke. It's straight forward and no big deal at this point. Just study the plans carefully because there are a lot of changes in rivet sizes as you go along, and there are a lot of holes left empty at this point.

Here's the left wing skeleton, all done. This sucker is finished! One down; one left. I'm calling it a night, though. It really feels good to have accomplished this much today.

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