I started today by fitting the attach angles to the bottom of the cabin frame. These two angles are clamped to the outer edges of the channels and then drilled to each other. After these were drilled, I countersunk the bottom face and riveted them together.
To ensure that the angles were mounted in the right position, I clamped some scrap angle to the longerons with some pieces of hinge material underneath to tip the angle back to match the slope of the side skin.
Here you can see that the angle is flush with the skin.
I then used some scrap 0.063″ aluminum (the thickness of the cabin frame channels) to space the attach angles back so that the forward edge of the cabin frame will be flush with the side skin.
I then drilled/reamed the attach angles to the rest of the structure.
I then temporarily installed the cabin frame to see how it fit. As I measured yesterday, it was slightly narrow, but a small amount of pressure from a clamp could spread it into position. The attach angles hang over the sides of the longerons. I marked the overhang and then removed the attach angles to start filing them down.
I took a break from the filing and laid out a cover for the cabin frame channel. I’m going to be installing a cover on this channel so that I can install a cabin light into it.
