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“Micro”
ultralight sailplane
The Micro is a concept
for an all composite ultralight sailplane. At this stage it is truly a “blue
sky” exercise, since I have neither the expertise or resources to complete
such an ambitious project. It was inspired by existing ultralight sailplanes
such as the LightHawk, and SparrowHawk. This class of aircraft is
designed to take advantage of the FAA’s Part 103 rules, which allow
unlicensed operation and are exempt from normal FAA type certification
requirements. Among other limitations, the empty weight must not exceed
70.4kg or 155lbs. Having flown gliders
briefly as a student pilot in the late 80s, I became acutely aware of the
high cost of the hobby. Since then, I have hoped for a low cost alternative
to the beautiful, but high priced European sailplanes. In addition to lower
cost, ultralights offer the potential to work “microlift” or lift that is too
weak to be exploited by traditional “heavy” gliders. This has been shown to
be possible with aircraft such as the Carbon Dragon, SparrowHawk and others.
Given that we have very few “booming” days up here in N. Calif., the low wing
loading of the ultralights have even more appeal. The structure would be
carbon fiber prepreg and Nomex honeycomb cores, done in female molds. Though
not shown, full span flaperons, like the LightHawk would be used, as well as
spoilers. I believe retractable gear is possible without exceeding the weight
target. Though apparently abandoned by the other production UL gliders, I
like the idea of “bomb bay” doors for foot launch capability, though it’s
hard to imagine self launching off a hill trying to support a 150lb glider
while sprinting at top speed! A 15mph breeze would lighten the load by half
though. Estimated specs follow.
All disclaimers apply, the
above are only WAGs at best, and wanton violations of the laws of physics at
worst. Wing
Analysis Plus was used to design and tweak the airfoil. The foil has got a
decent l/d, but a wicked and rather early stall. I can improve the stall
behavior somewhat, but at the expense of the l/d needed to achieve reasonable
performance at these low Reynolds numbers. I have gained a great deal of
respect for the pros who do this for a living, particularly guys like Dr.
Mark Drela, who tweaked the
LightHawk foils, and has worked on many pioneering projects such as the
endurance record breaking MIT Daedalus human powered aircraft. |
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All trademarks are the property
of their respective owners, and are used here only for identification
purposes ©2003 Dave Design |
