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  Back in the early to mid 1970s, I built
a Sterling Cirrus sailplane kit. Shortly thereafter I bought my first radio control
system (a used 3-channel
OS Digitron set), and in a somewhat desperate attempt to fly an RC glider,
actually managed to cram two of its huge servos, a huge metal-cased receiver, and a NiCad
airborne battery pack (the only part that has not gotten smaller in the intervening
50 years) into the cockpit area. Although the cockpit was very spacious, the balsa
frame construction was way too weak to support a radio system, but that didn't stop
me... well, not right away anyway. The ready-to-fly weight was probably three times
the recommended 12 ounce nominal. (Here is the
Graupner Cirrus sailplane kit)
 Although the Cirrus has a generous 87-5/16"
wingspan, with it 25:1 aspect ratio, the root chord is only a little over 4" and
the wingtip chord is around 1". Even with vertical sheer webbing between the upper
and lower main spars, the wing was far too weak for so much weight. After much work
covering the undercambered airfoil and compound curves around the fuselage with
Japanese tissue and brushing on a few coats of clear dope, it was finally ready
to fly.
The first couple "flights" consisted of tossing the Sterling Cirrus off a little
ridge about 3 feet high, at
Klinkin's Field,
in Mayo, Maryland. The flimsy wings flexed up into an extreme curve - it's amazing
that they didn't break. The landings were in soft, long grass, so the craft survived.
That was all well and good, but it was not exactly satisfying flying. Somehow, I
talked my father, who was skinny and no athlete, into running with a tow line in
an attempt to get it aloft. Between the two of us, the Cirrus was rendered unusable
after about an hour. Oh well, live and learn (or don't learn).
May 12, 2021 Update: At long last I managed to get a nice Sterling Cirrus
Sailplane kit on an eBay auction at a reasonable price! All the photos shown here
are from my kit.
  
  
  
  
  
  
  
Posted May 8, 2019
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