September 14-17, 2020
This is a completely optional add-on that most people can just skip. There have been some accident reports that mention a melted floor during engine fires in the past. Since we’re planning on using this plane for Sportsman aerobatic competitions, we felt it was a solid modification to increase safety. RV-10 users have also reported lower foot box temperatures after this mod as well.
I ordered some 0.020″ Ti skin online. I started with a 24″x24″ sheet knowing I would cut it down a bit. I would suggest figuring out exactly what size you want and just ordering it direct, as the local sheet metal place wouldn’t actually cut it for me. They said its too hard and could chip the blade on their shear. I took it another place and they did it without any hesitation though.
I took some measurements to lay out where I wanted all my rivets. I decided on 4 row of rivets. You have to take care to get the spacing right though so you don’t hit the floor stiffener ribs or the rib going across the front of the cockpit behind the firewall. You’ll notice near the top of this picture that there’s a bigger gap between the horizontal row of rivets and where the vertical columns of rivets start. This was done intentionally to avoid that firewall stiffener. I also left 2 rivets out of the bottom horizontal row that would go under the floor stiffeners. I’m going to drill a 1/4″ slot there to allow any trapped water to drain out.
It’s really hard to drill over 100 new holes in a perfectly good floor, but it came out looking decent once I was done. The next step was to cut a piece of 1/8″ thick FiberFrax to go between the Ti and the belly skin. I cut the FiberFrax 1″ smaller on all sides than the Ti skin. This will allow me to get a gapless install around the edge of the Ti skin and keep water out. If I cut the FiberFrax full size, the Ti skin would be 1/8″ off the surface of the skin all the way around and I would have to seal it up with Proseal or something else. I also took an edge roller and added a little bit of a bent lip around the whole thing.
I taped off the bottom of the fuselage and added a layer of primer. Ti and Aluminum don’t mix well, so having primer here should prevent any future issues from forming due to galvanic corrosion. I then cleco’d the skin in place to see how it all looks. Unfortunately all these holes have to be dimpled with a pop rivet dimpler, and that took a lot of stand-up/sit-down cycles to get these all done.
It actually gave such a good fit around the edges after the rivets went in that I don’t think I need to seal it up with anything. Its in a warm area so any water that does get in will get evaporated during the next engine run, and the two drain slots in the back side will let huge amounts of water out if it ever does find its way in there.
I had to wait a day or two before Kacy was able to come out and run the rivet gun while I bucked, so I decided to go ahead and install the pitch servo mount for the autopilot. We don’t have the servo yet, but it’s hard to mess up where this goes even without having all the parts here.
-Paul
(Total Build Time: 620.6