With the engine in its final mount position, we can now work on enclosing the engine for cooling air flow by working on the nose bowl, engine cowling and firewall. Our current classes Metallic Structures and Induction/Exhaust Systems fit well with these tasks.
Here you see photos of the nose bowl before and after creating the inlet for engine cooling air. The process was fairly simple but time consuming. 1. Roll aluminum tubing in a circle to the desired inlet diameter then weld ends together. 2. Center circle inside of nose bowl and secure (tack weld). 3. Mark and cut out metal about 1-2 inches less than inner diameter of rolled tube circle. 4. Turn nose bowl over (fwd surface facing up) using leather mallet start to form inner metal edge around tack welded tube. Small hammer blows will start metal to bend as desired. Too large an area will cause creases and poor results. The aluminum will get harder with each blow so you stop hammering, light your torch and heat the entire area being worked to soften (anneal) the metal then do some more. With hammers, heat, patience and time the process worked great.
These are views of the engine accessory section before and after making the firewall pieces. Students in our metallic structures class are fitting the pieces in place, riveting some areas and installing nut plates in other areas so pieces of the firewall can be removed allowing access for maintenance and inspections.
In our last blog we were trying to check our weight distribution in near level flight attitude after relocating the engine further aft. The final picture shows the amount of weight on the tail wheel (skid) yes 25lbs!! When the horizontal surfaces and brace wires are added, we’re seeing about 35-38lbs. Looks like the engine moving aft 7-8 inches did exactly what we planned (hoped wished prayed) for.