July 18, 2018 – I think I’m on the home stretch for the cowl. 🙂
I like the fit all the way around, so I decided to go ahead and drill for the Skybolt fasteners around the firewall.
Before that, though, I drilled holes for the screws in the area behind the spinner. This also helps to support the cowl so I can accurately drill for the other fasteners.
Skybolt gives you little tools that fit in the fastener holes of the flanges so that you can drill a centered pilot hole. They’re kind of like drill bushings that I’ve used elsewhere on the airplane. You secure them in the holes you want to drill, then do the pilot holes. The holes will later be taken up to size with a Unibit.
I back-drilled through these bushings, but there are areas where you can’t get on the backside because of the engine mount. So I used my triangulation trick that I’ve used before for blind holes. You basically mark two or three lines that center on the hole you want to drill, and mark the dimension on that line.
Drill at the intersection, and you should have a centered hole in the correct location.
I’ve got all the holes piloted except for the ones right adjacent to the gear legs. I’m going to see if I can investigate at Oshkosh whether I need fasteners that will ultimately be underneath the gear leg fairings.
I previously left off the flanges on the firewall that are in line with the horizontal split of the cowl, because I wanted to make sure those flanges were in the correct location. I marked on the skin where the split line was, then I located, drilled and installed these two flanges.
The Skybolt instructions say to install all the fasteners at the firewall, then do the fasteners at the horizontal split lines toward the front. I’m going to do it that way. But I believe I’m done now until after Oshkosh. Good thing I don’t have money yet for a panel… 🙂