With the templates made and parts cut out, building the fuselage with the jig is “Super Easy”. The jig holds the sides nice and square resulting in a very professional fuselage. See the Fuselage Jig Use posting on the Fuselage Jig post.
The firewall can be installed with the fuselage removed from the jig. It is glued in using 30 minute epoxy. Epoxy is applied to both parts and is clamped firmly in place while the epoxy cures.
Now that the fuselage is formed and tacked together, it will need to be permanently glued. Strategically drip medium CA into all the corners along all the parts letting it run along the corners. Do not breathe the fumes. Do this with proper ventilation and wear a proper respirator. CA fumes will hurt you!
The fuselage will need extra support and strength in a few areas.
The rear section of the fuse will be reinforced with 3mm carbon fiber tubes or rods. They are installed along the bottom side corners from the rear of the fuselage to the former where the fuselage starts to taper. The formers are notched to accept the rod prior to installing the bottom side. CA is used to hold the rods in place.
The firewall and landing gear areas will also need reinforcement. 1/16″ x 1.5″ aluminum angle and flat stock are used to reinforce the firewall. 1/16″ x 1″ aluminum angle is used to reinforce the bottom for the landing gear attachments. These materials are available at McMaster-Carr. The part numbers for the sections used here are:
|8975K199||Multipurpose 6061 Aluminum, 1/16″ Thick x 1-1/2″ Wide, 3 Feet Long|
|8982K7||Multipurpose 6061 Aluminum 90 Degree Angle with Round Edge, 1/16″ Thickness, 1.5″ Outside Height, 4′ Long|
|8982K39||Multipurpose 6061 Aluminum 90 Degree Angle with Round Edge, 1/16″ Thickness, 1″ Outside Height, 4′ Long|
The aluminum supports are glued with 30 minute epoxy to the inside of the fuselage.
The firewall angle supports are about 1/4″ shorter than the firewall and the flat stock runs from the angle to the first former.
The firewall angle and flat support pieces are welded together or brazed together. A MIG welder with the proper setup can be used to weld them. Brazing them together requires some Alumaweld rods and a map gas torch.
Welding or brazing requires the metal to be clean and bright. Oxidation and dirt will keep both from working. A dedicated stainless steel brush for use only on aluminum can be used to remove the oxidation. This firewall has a 1.5 degree down thrust angle so for the parts to fit the angle must be included in the support pieces. Care must be taken to make a right and left piece to be sure the angles are correct for each side.
Here is a quick video on how to braze them.
For detailed instruction on how to use the Alumaweld process, see the first 12 minutes of this video on Fuselage Construction.
Here are some pictures of the welding process.
The weld on the side to be glued to the wood is ground flat. The support parts are then roughed up to ensure a good mechanical bond with the epoxy.
Test fit them first.
I noticed the angle was not a true 90 degree angle when I test fitted these. So, I had to bend them into shape to ensure a proper fit.
Then glue the supports in with 30 minute epoxy. Use LOTS of clamps and a block where needed. They must be firmly attached to the wood. Wrap the block in waxed paper to keep it from gluing to the support.
The landing gear supports will be glued in later. Fuel tank and ignition supports will be installed first. The gear support angles are cut to fit from the firewall to the first former. They will need some trimming to allow them to fit at the firewall end. The bottom edges may also be trimmed later to make more hand room for an access door.
Here are some pictures of the fuselage after reinforcement and final gluing.
Now the fuselage is ready to be fitted with all the rigging and parts to make it into an airplane.