Helicopter Duration at
Science Olympiad Nationals 2010
Thomas Stokes, Jackson Amodeo
11th Place, 2010 Nationals
Kenwood Trail Middle School, Lakeville MN
Hap Stokes, Mentor, hapstokes@gmail.com
MN Science Olympiad 2010 Student & Coach Workshop
13-Nov-2010
Typical Science Olympiad Designs
Wright Bat –
1 rotor means
time bonus
Parlor Copter – 2 Rotors
Whirlibird – 2 rotors
Adding a center spar on top allows the helicopter to rise to
the ceiling and spin freely, making it a “Ceiling Walker”
Early rejected designs
Penni Helicopter
Heavy, Complex, Gimmicky
Parlor Helicopter with tube motor stick
Difficult to wind, Very heavy
Our helicopters
Designed for trial and error with adjustable rotor pitch.
6.1 gm helicopter and 2 gm rubber motor = 8.1 gm
Helicopter Design
Variables
Discussion
What we did
Weight
Min. 4 gms total, including rubber
2 gms max. Balsa wood.
We always made 2 gm motors. Copter was
6.1 gms, = 8.1 grams total. Too heavy.
Rotor shape & type
Fixed vs. variable pitch vs. airfoil.
Solid balsa vs. film on frame.
For simplicity of construction we used flat
rotors, film on frame.
Rotor diameter
40 cm max
We used it all.
Rotor surface area
Big surface adds more lift, but also
more weight and drag.
We kept this constant. In hindsight we
should have had less surface area.
Rotor angle of attack
If you have enough power, increase
angle until it stalls
This was our primary variable, and our
helicopter had adjustable angles. We ran at
18-20 degrees.
Motor (rubber band)
thickness
The more rubber you have, the
more power you can deliver, but
also the more tension must be
withstood by the motor stick,
which might require thicker stick
(adds weight).
We used 1/8” rubber, lubricated with
ArmorAll.
Motor length
Determines how many winds can
be stored in the motor
We used doubled rubber bands 22.5”. Too
short.
Motor # winds
Determines flight time. More
winds means more stress on the
motor stick.
With our heavy rubber and large rotors, we
could only crank about 240 winds max, which
limited our flight time. Best at Nationals was
36 seconds, enough for 11th place.
We used plastic O rings to make it easier to
transfer from winder to tail hook.
Math – Lift Equations
• www.aerospaceweb.org
Variable
Description
L
lift force
air density
V
aircraft velocity
Sref
reference area
CL
coefficient of lift
• “The Propeller Propulsion Science Olympiad” by Lew Gitlow
• For 6th graders, this math is too complicated.
• We chose “Trial and Error” strategy
Recommendations
1.
Buy a kit, build it
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2.
Fly the kit, try not to break it, learn from it
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3.
To make sure partners are clear, write commands for winding & launching
KISS (keep it simple stupid)
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8.
Weight is everything (target 4 grams total)
Power is everything else. More winds for better duration don’t matter if it doesn’t fly.
Build a stooge to hold the copter during winding
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7.
center mast for “ceiling walker” vs. slow climber because of rafters
Decide what you can design with math
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6.
scioly.org, soinc.org
look for Jeff Anderson, Livonia, MI
Learn about the ceiling, design for the ceiling
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5.
We couldn’t get the kit to fly. Why not?
We broke the kit before we could really learn why
Read Blogs
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4.
One source A2Z Corp, Englewood, CO, USA
Learn about building jigs, balsa strength,
glue types, glue techniques
Fix some variables
Don’t sweat the fine tuning the blogs talk about. Focus on weight and power to getting it
flying first.
Plan to build more than one, as you will break them
Design for the Ceiling
Nationals 2010
Univ Illinois Armory - 98ft ceiling
Minnesota State 2011
McCarthy Gym, St. Thomas
Support Equipment Design
Jigs (foam core board)
Carriers
• Rotor angle jig
• Protractor Angle Gauge
• 1:1 scale rotor patterns
(below)
• Travel Bin
• Winding Stooge (below)
Regular Pins
Push Pins
1
3
5
6
4
2
Misc
• Winder
• Scale
The Ultimate Goal
• Light = 4 grams
• Variable pitch
rotors = higher
efficiency
• Heavy motor stick
to allow many
winds
• Center spar to
allow long ceiling
walks