Thursday, April 6, 2017

head...shoulders..ribs and spars

Much work has been accomplished.
I drilled out the fuel tank ribs for better venting during fueling. I used a Forstner bit so that I could get close to the rib flange. And I enlarged the wire routing holes as per the previous blog post using a home made jig to center punch all the ribs in the same location and a step drill . Easy Peasy.


The main ribs were primed with no drama. Wings stands were bolted to the floor (shhhh don't tell mom). I am building both wings at the same time so it goes pretty quick; once the tooling is set up for the left wing, it is a breeze to finish the task for the right wing. I flipped the wings up right to rivet the main ribs to the spars. This provided good access. My son was home from college on spring break, so we were able to do 1 and 3/4 wings in a few hours. I used a double offset on the gun and this seemed to really suck up the driving power. I had to crank up the pressure to 60 psi and crank up the flow. This was manageable with two of us, but the bar was bucking quite a bit. Could not have done it without a tungsten bar; that compact extra mass really help make up for the double offset power suck up.

I had to drill out two rivets just because; I should have drilled out only one... the second was best before I touched it :-(
To rivet the remaining five ribs, I  got creative and made some simple tooling. I used a sheet of hobby plywood from the aviation isle of Hobby Shack with the thickness chosen to match the no go rivet gauge. This allowed me to hold the bar on the underside and not have to worry about scratching the spar or setting the rivet too thin. I also taped the double offset to the gun so it wouldn't rotate. I used two layers of duct tape on the end to try and help prevent smileys on the rib. In addition, I used one finger around the rib and operated the trigger with my middle finger. This kept me from tilting the gun over inadvertently as I watched the bucking bar dance around. Each rivet seem to take forever to set. I was concerned about work hardening the rivets, but no problem. I also did not assembly all the last ribs at once, but rather as I went. This allowed much better access to the rivets.
I still need to squeeze the rear spar rivets, but expect no drama with that. Onward.