After finishing up the top wing by making and installing the laminated center cutaway bow, it’s time to mate top wing to the fuselage. The struts that support the center of the wing (and set the wing incidence), are called the cabane struts. These work together with the outer interplane struts near the wing tips to support the entire upper and lower wing installations. Here’s how I do it.
I start off by installing all the plywood hard points for the attachment bolts in the wing. Using the plan’s side view I made up the plywood rib doublers and notched them to accept the plywood plates so they would be relatively flush with the bottom surface of the top wing. I installed 4 for the cabanes and 4 for the interplane struts.
Also using the sideview of the plans I made this alignment jig that supports the wing at the proper height and incidence angle (3 degrees).
Here you see the alignment jig in place supporting the top wing. The jig rests on the platform that’s under the main fuselage hatch cover.
Here you see the opening at the base of the jig that allows access to the holes where the cabane strut wires will be inserted.
To prevent the wing from being burned while soldering the attachment tabs to the cabane wires, I replaced the wing with these plywood strips. They are marked precisely for the locations of the attachment points.
Here is one of the blind nuts inserted in the attachment hole. Note that the plywood strip is also supported by some balsa spar material glued in place to prevent the strip from warping.
So here is the front right cabane wire and attachment lug in place on the model. The attachment tab is a steel solder tab available from Balsa USA. it fits precisely onto the 1/8 inch music wire.
Here’s the aft cabane wire. As you can see, it is bent to align with the inside of the fuselage and extends into the radio compartment about 1 1/2 inches.
Before soldering the wires, the bases have to be secured. I made this slotted plate from 1/8 inch lite ply and glued it in place.
A second lite ply plate is epoxied over the first to bury the wire securely. I used 5 minute epoxy to fill in the “pocket”.
The base wire in front of the firewall, is shown here. It is glued in place and the balsa section that I removed, will be replaced and glued with more epoxy to secure the front cabane wire.
Here the right front and rear cabanes are now in place. The jig sets the length and angles of the cabane wires.
Close up of the cabane wire and solder/attachment tab. The attachment bolts are 6-32 cap head screws and I use a lock washer between the tab and bolt head.
Before soldering, I also made the cross rigging wires. The ends are bent to match the angles of the cabanes.
I first solder the 4 tabs in place to stabilize the wires. Once cooled, I clamp the cross bracing in place, wrap with thin copper wire and solder the bracing in place.
Here’s the finished front left cabane attachment junction.
Here’s the bottom aft left cabane with bracing wire in position.
Bottom aft cabane juncture all soldered up.
Here’s the completed left side of the cabane assembly. Notice that I also soldered together the two bracing wires where they cross.
Here is one of the bass wood fairing strips that will be glued to the cabane wires. it is grooved to match the wire and are available from Balsa USA.
So with the soldering all done, I removed the plywood strips and placed the wing in the alignment jig. With the wing centered in the jig, I clamped it in place and measured from the tips to the tail post. Once everything was aligned, I drill through the attachment tabs into the top wing attachment plates. Then I removed the wing from the jig, removed the jig from the fuselage and installed the blind nuts in the wing plates. With that done, the wing was bolted in place and the alignment distances from the tips to the tail were checked again. The distance on either side is within 1/16 inch, so that’s close enough for me.\
The last step is to fit the hatch cover back into place.
A little at a time, these notches are made to clear the cabane wires.
That’s it. The openings will be enlarged a bit more after the wood fairing strips are glued into place.
Using the wing alignment jig is another advantage from designing the model with CAD and laser cutting out the parts.