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the tip). Use a straight edge (ruler) held against the wingtip to mark the correct width
(25mm) and correct angle onto the balsa trailing edge and then cut along this line.
7.
Repeat for the second wingtip using the other length of balsa trailing edge. Keep both
remaining pieces for the elevons.
8.
The leading edge face of each of these
balsa fin support pieces needs to be shaved
or sanded slightly so that it meets its top
and bottom surface at the same angle ie. so
its cross-section forms an isosceles triangle
9.
Round off the top and bottom edges of the
inner end only of each balsa trailing edge
fin support piece (not at the wingtip).
10.
Use 5 minute epoxy to glue on the two
balsa trailing edge fin support pieces. They
should be attached so that they form a
reflexed (trailing edge raised) airfoil shape
at the tips. The trailing edge should be raised about 2mm or 3mm above a straight edge
(ruler) held on the underside of the airfoil.
11.
The remaining two lengths of balsa trailing edge will now be used to form the two elevons.
Hold one of the pieces so that it is firmly up against the foam sub-trailing edge with its
angled end up against the outer end of the fixed trailing edge piece. They should match up
perfectly ie. the cuts should be parallel. Now slide it away slightly so that there’s a gap of
about 2mm (3/32”) between it and the fixed trailing edge, with its other end underneath the
trailing edge fin support. Mark a line on the elevon piece that is parallel to the fin support
with a 2mm gap ie. the elevon should have a 2mm gap at each end. Now cut out the elevon
along the angled line you just marked.
12.
Repeat for the second elevon on the other
wing half.
13.
Using a sanding block with rough
sandpaper (or a balsa plane), sand/plane a
45 degree bevel along the leading edge of
each elevon, with the 45 degree opening on
their bottom surface (ie. they’ll be hinged
on the top surface).
