First order of business is to establish a template for the cutline between the lower and upper cowl halves. I used the green painters tape to establish a 1 inch boundary along the lower cowl.
Next, the upper cowl was lowered into place with the spinner template to hold a common position between the halves.
The green tape was also used as a marker for the upper firewall/cowl junction.
I never did get a picture of the second layer of green tape on the upper cowl overlaying the lower cowl's green tape. With everything in place, it was time to begin marking the cutline along the second layer of green tape, which was projecting the edge of the lower cowl upon the upper cowl. I used an Exacto knife held on its non-cutting edge to scribe a cutline in the upper cowl.
Next, I sprayed some black paint on to the cowl's scribe line to try to get some contrast to aid in seeing the precise location. I had mixed results with this technique and eventually ended up just lightly scraping it off. I just ran another length of tape along the scribe/cutline to visualize where to cut.
After making the cut with my ever faithful Dremel tool, I decided to begin drilling the hinge line to see how close I was able to mate the cowl to the upper firewall edge. I actually was quite pleased with the result. I had to just smooth out a few spots with a sanding block and it all came out pretty nice and tight to the edge.
More clecos as I move along the periphery drilling the two hinge lines.
All holes drilled and cleco'd.
Now it was time to cut and test fit the cowl halves with their respective hinges. Below is a shot of the pilot side getting its hinge drilled and cleco'd into place.
Lots of holes and clecos! I put a rivet in every "link" of the hinge line in all locations, especially as needed in the areas with a tighter radius.
A shot of the solid riveting of the hinge to the cowl.
Hinges in place on the lower cowl.
Hinge in place on the upper cowl/upper firewall.
An important shot follows. The hinge pin that comes with the assembly is .089 inches in diameter. Unfortunately, I have not been able to use that pin to mate the hinges that either attach the cowling to the upper firewall or the cowl halves to one another because of the severity of the curves. The hinge pin will just not make the tight radius bends. I resorted to ordering some smaller diameter piano wire (0.071 inches diameter) to join the cowl to the firewall and the cowling halves together. The penalty one pays for such a "maneuver" is the resulting photo below. You will readily note the 1/32 - 3/64 inch gaps that now appear with the sloppier fit between the hinge halves using the smaller diameter piano wire for the hinge pin. I don't know if I will be able to overcome this unsightly limitation. It will definitely require more work to see if there are any other options. I am not a real happy camper.
The upper cowl half now gets its hinge drilled and cleco'd into place.
Rivet time!
Next up were the corners of the upper cowl where they meet with the lower cowl/spinner area. This nasty vertical split line needs all the help one can muster to make it look like a tight joint. I resorted to some backing plates with a Southco fastner (quarter turn) assembly riveted to the lower cowl. Below is a shot of the blank, before riveting the Southco fastener.
Backing plate assembly riveted onto lower cowl to facilitate a tight joint with the upper cowl.
Backside of the backing plate with the business end of the Southco fastener "nutplate". (I later ended up discarding the Southco fastener assembly in favor of a conventional nutplate and #8 machine screw).
The finished joint.
A relatively uneven split line...but it was the best I could manage. I do not like this cowl with the vertical jog in the split line - a very poor design if I say so myself. The next generation RV-12 cowl from Viking does away with this approach in favor of a more conventional "continuous" split line (although it is still not a straight line!). I may want to pursue the second generation cowl at some other point in time, after I see one up close and personal.
Its a decent "5-foot" cowl job...I hope.
And another other "hindsight is 20/20" viewpoint. The reveal of the prop extension is uneven from top to bottom by probably 1/8 inch. I was so worried about the lack of any excess material on the lower cowl (I did not have any to trim off!) that I mounted it as it was cut from the factory to the firewall. I should have probably trimmed off 1/8 inch or so, to allow the upper cowl to reach it evenly. Or more precisely, I probably should have added another 1/8 to 1/4 inch to the backplate of the spinner (plywood) template, to push everything back toward the firewall. As it stands, I have about 3/8 inch clearance between the cowl and the face of the prop extension as shown below. This may prove to be a problem I had not anticipated....time will tell the tale.
The requisite "Jimmy Durante" nose shot.
Another backing plate assembly was needed at the firewall shelf and the upper cowl. The picture below details my approach. Again, a Southco fastener assembly was incorporated into the backing plate, which was later replace with a conventional nutplate and #8 machine screw.
Installation of the backing plate, pilot side of the firewall shelf.
A close up of the cleco'd assembly on the top of the upper cowl.
The inlet ramp attached from the inside of the upper cowl.
Yet another glamor shot of the cowling...subconsciously hoping it will grow on me and I will like it better. Next up will be the struggle to concoct a duct from the upper cowl to the face of the oil cooler.
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