Sport Rocketry

SPORT ROCKETRY MAY/JUNE 2017 43 Lay the stabilizer flat, and CA the fuselage to it; use accelerator. Fillet the joint as neces- sary. Don't put on the rudder yet. Wing Cut two wing halves from 3/32" balsa. Round the edges of the wing (not the roots). No air- foil is required. If you don't have 6" wide sheet balsa, glue two 3" wide pieces together (flat) and use that. It helps to put a strip of aluminum foil on the table under the glue joint to prevent gluing the balsa to the table. Place the wing halves on your sanding table, and raise the wingtips 2". A 9V bat- tery works as a spacer to prop up the wing tips. Sand the root bevels. Fit check the wing joint and adjust the bevels as needed; minimize gaps. Lay one wing on the table, with aluminum foil under the joint area. Apply CA to both wing roots. Position the second wing, and elevate the tip about 4". Hold the wing halves together and apply accelerator. Make sure the alignment is perfect. Wait five minutes, then peel off the foil, and then sand the bottom of joint. Mark the fuselage 6.6" from the stab leading edge. This is where the wing trail- ing edge will be. Lay the stab/fuse assembly on the table with the fuselage on top. Ap- ply CA to the wing root and fuse, and then position the wing (level). Apply accelera- tor. Fillet the joint as required. This must be a strong joint. Pod Mounting Epoxy the pylon to the fuselage, with the 7/8"-high end against the leading edge of the wing. Radio Module Remove the receiver board from its case (note that the markings on the case label the connector pins referred to below). Cut the male pins to 0.1" long. The pins for CH5, RUD, and THR can be cut off com- pletely. Use hot melt glue (so the assembly is easy to take apart later, if de- sired) to attach the board to the 1/32" plywood ra- dio plate. Cut the servo wires to 1.5", and strip ends 0.1". You need 28-30 gauge strippers; ones for wirewrap wire will work. Tin the ends of the wires with solder. Tin the remaining six re- ceiver pins. The battery cable with the pico connector is difficult to find, but HobbyKing has a charg- ing adapter with six such connectors on it—so you can cut a connec- tor and length of battery cable from one of those. Trim the battery cable to 0.9", and strip and tin the ends 0.1". Solder the wires to the re- ceiver—the red (+) wire goes to the mid- dle of the ELE connector. Solder the servo leads on—the red goes to the middle of the AIL connector. The black leads go to the pins near the end of the board (see photo). Test the operation of the RC system before gluing the servo down. In case it is faulty, you can solder on a new one (buy a spare). Use hot melt glue to attach the ser- vo. Be careful not to get any glue "strings" in the gears where they would cause the gears to jam. Cut a 2" piece of BT-20, and epoxy the radio pylon onto the tube. Tape the BT-20 nose cone on to the tube. Plug the battery into the module, and then push the ra- dio plate into the tube, battery first, until it stops (the battery fits up inside the hol- Side view of the RumbleBee-C. Detail view of the rudder tape hinge, control horn, and push rod assembly.

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