I have been struggling to figure out the best method of transitioning the incoming air into the fuel servo as I have a very small amount of space between the forward end of the ALT AIR duct and the lower inside edge of the air filter element. I needed a plenum that incorporated a rubber boot to permit movement between the engine and the nose cowl.
After reviewing and discarding many ideas, I found a rubber boot intended for sealing pipes coming through the roof of houses. This boot was rated for temperatures up to 250 degrees, had a flexible base, and could be cut down to the exact size I needed to go around my ALT AIR duct.
With the rubber boot in hand, I fabricated the back wall of a plenum, cut the opening and made a flange to smoothly direct incoming air directly into the ALT AIR/Fuel Servo ducts. I cleco'd the parts in place for a test fit and I was very happy with the results. Now I need to finish the sides of the plenum, trim up all parts and assemble.
