Riveting primed ribs
After all of the wing main ribs were primed, we could get to work riveting the ribs to the main spar and rear spar. First the rear spar doublers had to be riveted on. The only trick here was figuring out which holes to leave open.
Here is a side note about how I kept the ribs in order through pre-assembly, priming, and final assembly: As I did with the empennage parts, when taking the ribs apart after pre-assembly and match drilling, I took them off in order and defined a measurement datum on the ribs. I picked the forward most edge of the rib. Then, I made a very small single punch mark in the rib with an automatic center punch. This punch mark was made a measured distance from the forward edge of the rib (my datum). Each successive ordered rib got a similar punch mark slightly further from the datum (about 1/8″ further). This way, we didn’t have to worry about order identification. All we had to do after primer was to put the increasing punch mark distances in order. Once they were in order, we put a little piece of tape on the rib with the rib number for final assembly. This is my general method for parts identification. The punch marks that I use are so small that you really need to know where to look for it in order to find the mark. I usually make note on the plans as to where to find the identification punch marks.
I used a double offset rivet set to drive the main spar rivets. The manufactured head goes on the rib side. Tanya did a perfect job bucking the other side which I had taped off to protect the spar against scratching. I drove these rivets with about 65lbs. of air pressure. Thicker material seems to equal higher pressure. I did struggle (meaning I didn’t fully succeed) to keep from banging up the rivet heads with the set. I drilled out a couple of rivets because I beat the crap out of the head with the gun. I also left a couple that don’t look very pretty but will be fine. Don’t get me wrong, most of the rivets look totally fine (pictures always make them look worse). I always seem to struggle with the double offset rivet set. It isn’t very square or true. I am thinking about ordering another one from somebody else to see if it is any better.
I waited to rivet the rear spar to the ribs until the ribs were riveted to the main spar. This is the way to go, as Dan C. found out and thankfully made my life easier. You very much want to be able to get into the rib and deflect it a bit when driving the rivets. This would have been very difficult with the rear spar already on. The temptation was very much there as I was itching to do some riveting before Tanya was ready to help.
Both main wing skeletons are now riveted together and back up on the wing stand. Now it is an exercise in alignment so hopefully as skins start to go on, we end up with straight and true wings.
