This morning, I started on engine cooling. In a conventional airplane (with the engine in front), there are openings at the front to allow ram air into the engine compartment to cool the engine. Since aircraft engines are air cooled, this is very important. Because the Velocity has a rear mounted engine, cooling is a challenge. The early Velocities used a pair of scoops on top of the fuselage just forward of the engine compartment. The scoops were similar to the hood scoops that you used to see on some high performance cars. The problem with scoops is that they aren’t very efficient and since they protrude into the airstream, they cause drag.
So instead of air scoops, we will use NACA Ducts. NACA (National Advisory Committee for Aeronautics) was the precursor of NASA. They discovered that if you create a recessed opening with the right shape, you can get more air with no drag.
So my first task was to cut out the two openings for the NACA ducts to the engine compartment and one for fresh air to the cabin.
From the back looking towards the front at the top of the fuselage. You can see where the two large ducts will be. There’s also a smaller fresh air duct in the middle. The tan colored area is the rear of the fuselage (also know as the firewall) where the engine will be mounted. I’ve also marked the openings in the firewall for the ducts.
Here, I’ve cut out the engine cooling ducts on top of the fuselage. At this point, I haven’t done the fresh air duct or the firewall openings (although they are marked).
After cutting the small NACA duct and the firewall openings, I prepared the surfaces mounted all three ducts with structural epoxy.
One of the things I’ve got be better at is taking pictures. When I get rolling on a task, I forget to pull the camera out and take pictures. This is why there are no pictures of the installed ducts and flight controls in the keel.