|Project by Wolfdrool||posted 08-27-2012 05:51 PM||1526 views||4 times favorited||3 comments|
The finished cupola includes four separate subassemblies: the saddle base, the louvered house, the roof assembly with weathervane mast already attached, and the sailboat weathervane. Each is carried to the roof separately and then screwed together. I sketched out the design before building, but upgraded components and the design along the way. Hence, I built almost all the components at least twice. My goal was to make this so that the subassemblies could be assembled easily and in only one way up on the roof. It all has worked out in the end, but my scrap heap is a little bigger than desired.
The weathervane and mast were recovered from our old cupola that was destroyed in a storm about a year ago. The weathervane components survived with minimal damage, luckily.
The house louvers are simply house trim with a triangular cross section glued and screwed with countersunk screws to cleats along the house frames. Easy and fast “faux” louvers. These are well sealed with epoxy, particularly the end grain, to help survive the weather.
Indeed, all parts are sealed with three coats of epoxy, two primer coats, and two finish coats. The cupola took longer to seal and finish than to build. Building took a while, though.
The roof panels are ¾ ply that are assembled using stitch and glue techniques, including generous, inside glue fillets on the inside seams and fiberglass and epoxy on the outside seams. The mating surfaces of the triangle panels also are glued and screwed with countersunk screws. Quarter inch ply is more typical. But, the thicker ply is stronger, makes it easier to attache the weathervane hardware, and uses a very simple rafter simple. Even with the thicker plywood, the roof assembly is no heavier than the old roof assembly with its more complicated rafter system and heavier roofing.
The roof is sheathed monolithically with a composite made from two coating materials not normally used together. Individually, neither coating was acceptable in terms of both adhesion and durability. Together, they work great in panel tests, surviving hammer blows and hail tests (i.e., pelting with rocks). Four total coats were used to get an even texture. It remains to be seen how well this will hold up. The condition of this sheathing next spring after a cold winter should tell the story. If things look good then, the roof should last a long time. I used this approach instead of copper because copper sheet is just too expensive right now.
The small copper cap on the peak, unlike copper sheeti, is not too expensive and cost around $5 at Home Depot. The peak of the cap was sanded down to create the hole to fit over the mast. The copper sanded easily, to my surprise. Instead of sanding, I cut an earlier version, but this produced a jagged hole. The small gap remaining between mast and copper is caulked.
The weathervane mast is mounted to the inside of a roof panel using an articulating arm that is bolted tightly to lock the arm in the final position. A solid, large glue plug at the peak helps to secure the mast in position, like a mast step on a sailboat mast. The mast is thus stabilized by both the arm and the glue plug. I like this set up better than mounting to the outside of the roof, as is more common. It looks cleaner. Also, the lag screw holes, soaked with epoxy before driving the screws, are more protected from the weather.
This was a fun project with some challenges (both building and design) along the way.