M. K. Bengtson Sopwith Pup 40 Model Instructions - page 6
Sopwith Pup 40” Page 5
Copyright© 2005‐11 M.K. Bengtson All Rights Reserved Rev 09/11
WHEELS
Gluing the ply sides on the 3/8” balsa core makes the basis
for the wheels. Use the brass hub for alignment. Epoxy the
hubs in place and add a sufficient amount of epoxy
around the base of the hub to reinforce the connection of
the hub to the ply. Plywood reinforcing hubs are provided
that are to slip over the brass tubing as shown. Next, CA
glue the neoprene cording together to from a “tire”. Use
thin CA sparingly as the CA bonds very aggressively to
the rubber. Press the CA wetted ends together for an
instant bond. The best way to align the ends is to glue
them while they are in place on the wheel. Then attach the
tires to the wheels and CA in place. A thin bead of CA
around the rim makes for a secure tire.
Wheel Construction Detail
Paper cones are cut out. Use a ball point pen to score each
line on the back to make an impression of “spokes” It is
helpful to do this operation on a paper tablet so that the
pen makes a good crease. Fold the paper along the crease
lines to exaggerate the raised lines. One of the sections
forming a wedge is cut out. Make cuts to the center of the
circle along a pair of the spokes. Close the paper cutout to
form a cone and tape the joint inside the cone.
Wheel Assembly Detail
The inside cones may now be attached to the wheels. The
outside cones may be attached at this point if wheel
collars are to be used. Alternatively, after installing the
wheels on the landing gear, a washer may be soldered to
hold the wheel in place and then the cone is attached. This
method makes a very nice scale appearance.
INSTALLING THE RADIO CONTROL GEAR
Servo Bay
Get the R/C gear fitted at this stage, and also the motor.
Aileron Servos
Aileron servos are mounted in wing and attached with
short threaded rods to the ailerons. Use a “Y” wiring
harness connector to wire the servos to a single radio
connection. Alternatively, two RC channels can be used
when mixed electronically. If differential aileron throws
are desired, rotate each servo horn forward about 20
degrees, while maintaining the neutral position of the
aileron. This should counter any adverse aileron yaw.
Aileron Servos are mounted in Wing
Battery Tray
After all the above has been placed, mount the battery
tray made from 1/8” balsa and use the battery position to
balance the model as shown on the plan.
ASSEMBLY
Fitting Tail Surfaces
Attach the rudder to the vertical stabilizer using 1/8”
strips of CA hinges. Similarly, attach the elevator to the