The first step in installing the bathroom window. We purchased a marine window from the Fuller Brush company. The standard spigot length (the part of the window that extends through the wall) is 2.5", which is the exact thickness of our walls.
The marine window is different from the other Hehr windows we've installed in the following ways:
-The trim ring goes on the outside, instead of the inside.
-The spigot has a downward slope of 15º
I used the inside shape of the trim ring to trace the window shape onto the bus exterior, then used a jig saw to cut ONLY the outside wall (since the inside will be offset slightly). The insulation has been removed in this photo -- you see the back of the interior birch paneling.
I then placed the window in the opening (upside down) to trace the opening shape onto the back of the paneling. This way I could duplicate the slope from the outside, and get the vertical offset just right.