Cowling Par Deux
At the end of the previous post I described how I'd managed to somehow over trim the fiberglass, in spite of countless trial fitting iterations, along the seam where the top and bottom cowls join. For a while I thought I'd come up with a solution. Before drilling the rivet holes for the piano hinges which hold the
two halves together, I used clear packing tape to hold the cowl halves in alignment while drilling the upper cowling and piano hinge. The pin had been inserted into the two hinge halves, holding everything in place.
It seemed to work well, drilling and clecoing front to back
With the drilling done and all the countersinking done in the fiberglass, I squeezed all the solid rivets and proceeded to install, for the first time, both cowlings with all pins inserted.
Since everything was riveted in place now, with no room for adjustments, the two curved pins along the aft edge of the top cowl were, to put it mildly, a (suppressing the urge to swear) problem. They had been difficult before but now seemed impossible. Dry Boelube helped, but not enough. I ended up inserting some spare pin material into the hinges, chucking it up in my drill, and spinning it a bit. This opened up the holes in the hinges enough to allow insertion of the curved pins. The gaps between cowl halves looked good as did the gap between the prop spinner and the front face of the cowl.
What a clever builder I am! I got to enjoy this fantasy until doing the next step: Fiberglass in the cooling duct.
The cooling duct as supplied is of necessity too large, requiring another iterative session of fit-mark-trim-fit-repeat.
The duct takes in the ram air just behind the prop and directs some of it to the oil cooler, which attaches to the duct, and the rest to the coolant heat exchanger which doubles as a heater core for cabin heat.
The fit between the duct and the lower cowl doesn't have to be perfect since the duct is epoxied to the cowl along with fiberglass cloth, making it easy to fill any gap.
The hard part is getting the duct to interface correctly with the face of the coolant heat exchanger which is attached to the airframe. A deformable rubber seal helps a little.
When the duct is satisfactorily fiberglassed to the lower cowl, before the epoxy sets up, the upper and lower cowls are attached to the airplane with all piano hinge pins and screws inserted. This is supposed to ensure that the final fit is good. The problem is that the duct is a large, rigid piece which inevitably distorts the lower cowl a bit, screwing up the perfect fit which I bragged about earlier. Now the seems are no longer perfect. C'est la vie.
At this point I fabricated and riveted in the oil cooler door, using the RV-12iS plans which include a nice holder for the oil cap riveted to the inside of the door.
The NACA duct used to cool the voltage regulator was fitted and glassed in. I'm siffck of fiberglass.
Off Topic: more Colorado wild life.
My home in North Carolina was waterfront on beautiful Badin Lake, a 5500 acre reservoir 25 miles east of Charlotte. There were quite a few nesting pairs of Bald Eagles there, so seeing them fly by was common, but never got old. I never had one land on my house, however, until I moved to Colorado.
