Picking up where we left off on the assembly of a ProCub Rear Fuselage….
In similar manner, we will glue on each of the remaining rear fuselage bulkheads. Remember, the placement distances are measured along the centerline, not along the slant edge.
After all of the five bulkheads are glued in place, it will look like this.
Now it is time to make the hardpoints for the attachment of the rear fuselage. They are constructed from baltic birch plywood. The size of each hardpoint is 2″ x 18″ x 12mm; use two pieces of 6mm thick baltic birch plywood for each hardpoint and glue them together using a superior grade of wood glue.
Now it is time to glue on the side plank of the rear fuselage. You will want to test fit it first (using helpers and / or clamps) and ensure that the fit is flush. You may need to slightly trim the bulkheads for a perfect fit using sandpaper and a foam rasp. After the test fit is perfect, it is time to glue the side plank as shown below:
In an identical manner, glue on the other side plank. (Not shown.)
It is time to glue in place the left and right side jigsaw extensions, which were CNC milled from 1″ foam. At the very rear of the fuselage, where they mate together, you must make a bevel which allows them to symmetrically join together.
The rudder front square post is glued to the most rearward bulkhead, on the most rearward side. It is a 36″ length piece of 1″ square aluminum thinwall tubing, and it protrudes 2″ above the bulkhead, as shown in the following photo. This ensures that it will be merely flush when the remaining bottom plank is glued in place. Also, you’ll need to cut a hole in the existing plank, so that it can poke through as the assembly overhangs the table.
A 1″ hole must be bored in the foam at the location shown in the photo below. This is done on one side of the rear fuselage only; it is the exit hole for the elevator pushrod.
It is now time to bore out a series of holes which will provide for the elevator push-pull torque tube passage. It is our plan to eventually include the placement of these holes in the bulkheads, so that you don’t have to do it. But as of this writing (January 2015) we have not yet programmed the CAD and routing to do that on the bulkheads. So it has to be done manually by the builder.
Please remember that you are building this rear fuselage assembly upside down, and the objective is to provide a ‘straight shot’ bore hole from the elevator reverser bellcrank to the elevator. The elevator push-pull tube will pass through this series of holes.
Following are the hole locations which must be drilled into each bulkhead.
The other bulkheads are drilled as follows:
After each hole is made, the lineup of holes will look like the following photo. (Ignore the gorilla glue!)
Now it is time to glue on the remaining bottom rear fuselage plank. Start by making a hole for the 2″ proud front rudder post.
Don’t forget surface preparation: sanding, test fitting. There’s a lot of Gorilla glue to apply, so a helper may be useful.
After the glue sets, remove the weights, pins, clamps from the assembly and turn the assembly over. It is time to attach the rear rudder post, which is also 36″ long.
In order to do that, the foam must be trimmed. We’ll mark the trim location by borrowing the partially assembled horizontal stabilizer, setting it in position, and noting the trim spot.
After noting the trim location, we start making a cut using an Exacto saw.
After some sanding, it is time to glue the rear rudder post in place. This is done with Gorilla glue, a helper, and lots of masking tape. Ensure that the post is perfectly flush and square, or your rudder will crooked!!
To be continued…