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3.
Locate the plastic spar joiner and place it
on top of the central wing join. Align so
that the spar joiner’s hole is centered over
the wing join line and that both ends are
centered on top of the spar channel.
4.
Trace around the wing joiner with a pen
and then use a sharp utility knife to cut
along this outline all the way through the
foam. Push out the resulting foam plug and
put it aside to be used later.
5.
Also trace the outline of the spar joiner on
a scrap piece of EPP (perhaps from the top
part of a wing bed) for possible use later.
6.
Glue both 9mm spars into the spar joiner
using 5 minute epoxy glue. Ensure that
each spar is pushed all the way into the
spar joiner.
7.
Gently bend open the spar slot and run a
bead of goop/goo glue (30 minute epoxy is
also fine but not quite as good) inside the
spar channels of both wing halves. Starting
at one wing tip, bend open the spar slot and
push the spar assembly into the spar
channel. Once the whole spar assembly has
been inserted, use a piece of dowel, or
back of a pen or pencil, to firmly push the spar assembly all the way down into the channel
so that the glue is forced up and around the spars, coating them entirely. This process can
also be helped by bending the wing chord-wise, temporarily opening and closing the spar
slot. Wipe off any excess glue.
8.
Place the entire wing back into its foam beds and rest it on a completely flat hard surface
(eg. table or floor). We suggest removing the top portion of the wing beds by cutting along
the leading edge. Weight it down so that the wing is kept flat and completely snug with the
bottom curve of its foam beds. To avoid deforming the foam make sure the weights aren’t
too heavy and that they are spread fairly evenly. Bags of sand are ideal because they contour
to the top of the wing. Leave overnight (or as per glue’s instructions) in this position while
the glue fully cures.
WING ASSEMBLY
There are a couple of options here regarding the spruce drag spars (sub-trailing edge spars). If you
want to build your S-15 as light as possible they can be omitted entirely. As a “standard” build we
suggest at least attaching spruce drag spars to the outer panels’ sub-trailing edge. Attaching them to
the inner panel’s sub-trailing edge as well (prior to installing the balsa fixed trailing edge pieces)
increases strength even further with only a small increase in weight.
For those that like being a bit different, you also have the option of building the S-15 with a single
fin on a central boom instead of the standard dual fins (most robust). These instructions won’t detail
the single fin option but it’s a relatively simple matter of using the provided 5mm diameter carbon
tube as a boom embedded into the bottom surface of the wing (into both the balsa trailing edge and
