We continue our workshop build-along with the assembly of the rudder. This project is my 85-inch version of the Ziroli Plans Skyraider. As with most of Ziroli giant scale warbird designs, the Skyraider’s rudder uses inset plywood hinge tabs that support an internal metal hinge wire that runs the full length of the control surface. The setup is very strong and also makes the control surface removable should you need to repair.
This setup provides a very smooth friction free pivot action while retaining the scale outline of the control surface. Let’s build the rudder.
Using a LaserCutUSA.com laser cut parts, all the pieces are nicely identified and match the plans precisely. Start by gathering all the parts needed including a length of 1/16 inch wire, (I used welding wire), and a Sullivan Products Gold-N-Rod yellow pushrod tube.
The majority of the rudder’s area is built just like the elevators were with the ribs being glued on top of the sheeting and then the leading edge glued in place as shown. I use Zap Glue throughout. To make sure I got the ribs in the correct place, I drew extension guide lines on the plans.
Once the basic rudder is glued together, the pivot tube and wire are centered on the sub-leading edge and glued in place. Here you see that one of the balsa filler strips has been glued in place under the tube. Another one will be glued above the tube.
Here the rudder is ready for the leading edge blocks to be added. Laminated blocks are stiffer and the lamination lines help with keeping the blocks symmetrical when cutting and sanding them to shape.
Using yellow glue, I laminated several pieces of balsa to form the blocks.
Once the glue has dried the blocks are cut to length and then the ends are sanded smooth and square. Use the plans as a guide.
Here you see the leading edge block has been glued in place and shaped into a rounded leading edge.
Again, using the plans as a guide, I glued the blocks in place forming the required slots to fit the plywood hinge support tabs.
Remove the pivot wire and then cut through the yellow sleeve with a razor saw. This will expose the wire in the slot as shown above. Next, using a hobby knife, and a thin grinding bit and Motor-Tool, remove enough material from within the slots to allow the support tabs to mate with the wire and move freely.
Once the rudder is complete, it can then be used as a guide to glue the tabs in their proper positions in the vertical fin and rudder post areas during the fuselage build. There are three attachment (hinge pivot) points and the wire maintains perfect alignment for a very smooth and friction free hinge setup.
After the fuselage is framed up, but before the final sheeting has been installed, you can install and align the rudder control linkage, Here I am using Sullivan 4-40 Steel Rod pushrods coupled with Robart ball-link control horns and clevises. For even control throw in both directions, it is important to keep the control horn attachment point for the clevis is aligned with the pivot wire within the rudder assembly.