Quickie Q2 Lite, Construction Manual

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Q2 Plans - Chapter 3 - Page 3-14
SURFACE FINISHING
INTRODUCTION
..... Finishing the composite airplane is more important than simply
obtaining an attractive paint job. The finish on a composite aircraft
serves to protect the structure from deterioration due to ultra
violet radiation (sunlight). The finishing materials also give the
airplane its final aerodynamic shape. Using the proper materials and
techniques, the finishing process is pleasing (both esthetically and
aerodynamically), and provides for long maintenance-free service. Use
of sub-standard materials can limit the life of the finish, result in
an overweight airplane, and even limit the service life of the
airframe. Sanding is done frequently during-the finishing process and
extreme caution must be exercised to avoid damaging the structure. A
poorly executed finishing job can destroy the structural integrity of
the airframe. Even the finished color of the composite aircraft can
effect its structure. The finishing process is as important to the
structure of the composite airplane as basic materials and techniques
used in fabrication are. Proper techniques must be adhered to for
safety as well as to obtain an attractive airplane.
..... The Q2 is sensitive to weight growth. You may easily add 50
pounds during the finishing process if you try to finish the entire
aircraft to sailplane standards (smooth, wave-free surfaces).
..... There is one part of the aircraft that must be finished to a
smooth and wave-free surface - the canard. We have found that unless
the canard is smooth and wave-free, serious degradation of
performance and flying qualities results. This section will tell you
how to obtain a smooth and wave-free finish on the canard.
..... The rest of the airplane, in order to keep it as light as
possible, should be sanded with very little filling, then primed. and
then painted. This will allow some of the fiberglass weave to remain
showing, but your Q2 will still look good.
..... Remember, build it light and finish it light; every pound of
weight that you save during the construction and finishing will make
the aircraft much more fun to fly in the coming years.
FINISH COLORS AND HEAT
..... The materials used in amateur-built composite airframes are
predominately epoxy resin systems with fiberglass reinforcement over
a variety of plastic foam cores. The epoxies and the foams are all
sensitive to high temperatures. Some epoxies, cured at elevated
temperatures, retain their physical strength to temperatures not
found outside an oven. Others, including most room temperature curing
epoxies such as the Safe-T-Pox system, soften and loose their
rigidity at only moderate temperatures. The common plastic foams are
also heat sensitive and. tend to soften and (some) swell with
moderately elevated temperature. Elevated temperatures could
potentially cause a softening of the fiberglass load bearing
material, a swelling of the foam core, and general distortion of the
airframe. To achieve elevated temperatures you would have to bake
your airplane or find some other means of heating it. The sun is a