I’ve always liked the look of jalousie windows on a vintage camper, but the ones on either side of the ’65 Avion truck camper have a flaw that can cause them to leak. They are high enough on the wall that they slant inwards at the top, and since the sill is designed to be horizontal when the window is installed, it actually slants inward about 6°. This means that water that gets onto the window sill is likely to pool rather than drain away to the outside. If your window is perfectly sealed the water should just sit there until it evaporates, but chances are the seal will not be perfect and the water is going to find its way into the wall.
Some jalousie windows, like the ones in our 1964 Airstream, have a sill that slants outwards so the water drains. To solve this problem I made an aluminum ‘cover’ for the sill that allowed it to slant out for drainage. There may be better ways to do this, but I used 3/8″ aluminum bar stock which I shaped on the milling machine. It was time consuming, but not as bad as having the new wings rot out again.
I did this to the two windows on the curb side and the single window on the street side. The bathroom also has a jalousie window in the back wall, but that wall is vertical so it doesn’t share the same problem.