I dry fit the roof spars and finalized their positions. I doubled up the spars near the galley and the top of the roof where the fan would be mounted to provide extra support.
I used 1-5/8″ deck screws which were countersunk to hold them in place for the fitting. I will use Loctite PL Premium to glue them to the top of the headliner and the walls a bit later on.
Building the frame for the window and fan. As you can see the window will be placed so the seam in the headliner will be hidden for the length of the window. The transition from a curved roof to a flat window frame made me trim the cross spars in the frame slightly so they would meet up flush with the top of the roof spars while allowing the birch headliner to contour itself from the curved to the flat surface.
I glued the roof spars into position with Loctite PL Premium in sections allow one group to dry before moving onto the next. The tie down straps kept them snugly up against the headliner for the construction adhesive to dry correctly.
I then made some corner framing for the skylight using the windows’s trim ring as a template and a band saw. They were glued with PL Premium and secured with brad nails.
The roof blocking will be installed on the inside edge of the wall between the roof spars. They will provide greater rigidity and greater surface area for the outside skin to be glued upon. I clamped the roof blocking strip to the outside of the wall and planned my relief cuts I would make so the individual blocks would fit between the spars.
Making marks to cut the blocking.
I cut the blocking with a chop/mitre saw. I also made sure to allow for holes for my wiring that I had drilled in the walls. The blocks were then permanently glued them using PL Premium and held by brad nails.