February was “tunnel month” on my Bede BD-4C project. The floor of the airplane will look like an old fashioned rear wheel drive car, with a tunnel down the middle. The difference is that the BD-4C’s tunnel will house controls, brake lines, and electrical cables instead of a drive shaft.
I started by making a panel to cover the back of the nose gear box. This photo shows the panel in process. I have clecoed it to the sides of the nose gear box and taped a piece of aluminum in position which will be the stop to keep the rudder pedals from being pushed to far forward. (Click on this photo, or any other, to see the picture larger and in more detail.)
The stop bar for the rudder pedals is wide enough that I was able to fasten it through the thin metal of the front tunnel wall and onto the nose gear angles. You can see the nut plates in this shot. The nut plates are very cool, giving you a way to put a nut in a position where you will not be able to get a wrench when it is time to tighten up the bolt.
Here is the forward tunnel wall with the rudder pedal stop bar bolted into position.
With the forward tunnel wall complete and clecoed onto the airplane, I mocked up the forward tunnel wall using poster board. These walls are 3½ feet long and seriously lacking in square angles.
The front of the forward tunnel wall was the most challenging part.
I trimmed and folded and taped and trimmed some more until the mock-up fit neatly around the rudder pedal torque tubes and the tab against the front tunnel wall did not have a gap under either end.
Turning the poster board mock-up into aluminum proved even more challenging than I thought it would be. It took me several tries to get the front tabs bent properly. I would bend the tab, try to fit the wall into the plane, flatten the tab out, rebend it, re-fit, and repeat. Since the tunnel walls do not support anything more massive than the extremely light plastic brake lines, I am not worried that I have weakened the metal with all of the bending and straightening. Here is a close-up of the final result.
This photo shows the forward and middle tunnel walls clecoed into position.
Last, I ran the brake lines between the pilot’s and copilot’s brake cylinders and through the tunnel and down the backs of the main gear legs to the brakes on the wheels. Then I coiled the lines up and out of the way. Once I fabricate the tops of the tunnel and rivet the tunnel walls to the fuselage floor, I will attach the brake lines to the walls.
