User Manual

Cut the main spars from 1/8” sheet balsa and join together over the plan so that the dihedral
angle is correct. At each end of this section of the main spar, build the box that will receive the
plug in outer wing sections. At this point the spars for the outer wing sections should be made,
and the hardwood tongues attached that plug into the box that was made on the main wing
section. It is easier to make these fittings at this point than later in the construction. Now glue
hardwood strips to the top and bottom edges of the wing spar as shown in the plan.
Cut all the ribs in two at the point where they join the spar. Assemble one half of the main wing
section with the spar of the other half propped up, just as was done for the stab. Notice that the
leading edge consists of two strips of 3/16” sheet balsa. Only the first (inner) strip should be
applied at this time. Attach the trailing edge. Next assemble the other half of the wing. Sheeting
is now applied to the lower surface of the wing from the leading edge to the main spar. At this
point the wiring should be installed for the motors. It will be noted that the wing is still not
torsionally strong, meaning that it can easily be twisted. After the sheeting is applied to the
upper surface of the same area, the wing will be very rigid and difficult to twist. Hence it is very
important when applying the sheeting to the upper surface, to weight that section of the wing
down on a surface that is perfectly flat. The remaining strip of 3/16” sheet balsa that forms the
leading edge is now glued to the one in place and contoured to shape. Finally, cap strips are
added to the rear sections of the ribs, and sheeting to the centre section where indicated.
The outer wing panels are built in a similar manner, but noticing two things. When applying the
sheeting to the upper surface of the panel, the trailing edge at the tip should be propped up ¼” to
provide the correct washout. Then notice that the outer strip on the leading edge is ¼” thick
instead of 3/16” to allow for the larger radius of the leading edge in the area of the NACA cuff.
The tongue and box sections for the secondary spar need to be added to the outer wing panels as
well as the main wing section.
The construction of the tip floats, nacelles and cowlings is fairly basic. The nose ring of the
cowling starts like a doughnut, and can be of one piece of thick balsa, or laminations.
CONTROL THROWS
Control travel for the elevators is 1” up and down. For the rudder it is 2½” each way. The
ailerons should travel 7/8” up, and no more than 3/8” down. Importance must be given to this
amount of differential in the ailerons, and it will be achieved if the control arm on the aileron
servo is made as shown. At the start of the take off run in a flying boat, one of the tip floats will
be in the water. It is necessary to lift this float out of the water using ailerons, or the model will
want to turn in the direction of this float that is dragging in the water. Poor aileron design
aggravates this problem in many models because of the adverse yaw that is inherent at larger
angles of attack, such as while getting on the step. Two things are done in the design of the Mars
to overcome this problem. Frise ailerons are used, and a substantial amount of differential is used
in the aileron linkage. At the start of the take off run, while holding up elevator to get on the step,
advance the throttle just a small amount at first until the wings are levelled with both tip floats
out of the water. When this is under control, advance the throttle further and relax on the up
elevator as the model accelerates on the step. With practice this becomes one smooth continuous