Our experimental downdraft cooling system worked so now we’ll make it official. Starting with the intake plenum, the left and right intakes need to be framed up. Note the fiberglass frame. The outer edge is vertical but the inner is angled so the upper cowl will find its way ‘home’ when we set it in place.
The dip stick is always in the way. The big improvement is to seal it off so no pressure is lost to the lower side.
Frame on the right side. These will be riveted in place and silicone sealed.
Next we replace the sheet aluminum lid with fiberglass. The shape was too complex for a single sheet. I started by lining the surface with duct tape and building a flox corner, kind of reverse engineering. After it hardens I’ll sand it flush with the edge to give us a surface to attach the lid.
Here’s an idea from the old days of covering with Ceconite. It is tacked down around the edges and heat shrunk to remove wrinkles. Next, two plies of fiberglass are wetted out right on top.
Incidentally, I’ve heard that the plenum lid is necessary because using only the upper cowl as a lid creates internal pressures in flight that would be worrisome at least.
When this hardens, it is removed, Ceconite and all. The Ceconite is natural peel ply. It rips right off.
