Safety Comes First - 2009/02

106 MODEL AVIATION
Sperzel must have gotten an A in both classes, because he showed and
explained the math.
The propeller diameter (and pi) gives you the distance that the tip
travels, and then the engine rpm tells you the speed. A typical gas
engine can easily drive the propeller tip faster than 500 mph, and a hot
engine with a large
propeller can exceed
600 mph.
There are several
options for dealing
with this fact. We
can take up RC
gliders, which are
great fun and quiet.
We could all meet at
my indoor site,
which is relaxing
and even quieter. Or
we could keep our
hands out of the
propeller arc!
Imagine the harm that a 600 mph piece of wood or plastic could do
to a finger. Propeller strikes continue to be a common occurrence,
despite the fact that all of us know to keep clear of such an obvious
hazard. I would love to have an entire month go by without a report of
some bloodshed from an otherwise experienced and alert modeler.
I do not claim to have experience or alertness, but the finger that
types these words of warning still bears a little scar from when I put
my own hand into a running propeller. It was long ago, but I do not
recommend it.
We modelers have unique viewpoints on some matters, don’t we? We
accept that our models may harm us a little or a lot if we are
inattentive. Our miniature flying machines tend to have fairly short
lives, despite the long labor we sometimes put into their construction.
They might crash or just fly away, and we are (usually) okay with
those possibilities. A typical modeler is almost as impressed with a
Safety Comes First Dave Gee | [email protected]
Also included in this column:
• A “Tale of Two Tethers”
• Shrubbery for safety
• Do small children belong at
the field?
Clocking the speed of propeller tips
Blurry photo, golden moment as Pat Kinne
visits the field with his grandson, Andrew.
Small children require extremely close
attention near powered models.
Science teachers try the AMA AeroLab program at a convention. Note the nice cone,
replaced by a makeshift trash-can tether pylon, which works better.
Ralph Gee built this tether rig for middle school kids to fly rubber
ROG models in confined spaces. Racing two at once guarantees a
crash finish.
HAVE YOU EVER wondered exactly how fast the tips of our
propellers go? I lurked through an Internet discussion on this subject,
and, sure enough, somebody did the math and shared the answer. The
formula is not difficult, if you passed geometry and algebra. Hank
02sig4.QXD 12/22/08 12:29 PM Page 106
nice piece of support equipment as with a
beautiful aircraft.
These attitudes set us apart from normal
people, and we should be aware of the
different ways the nonflying public sees our
hobby and us. To illustrate, following is the
“Tale of Two Tethers.”
The AMA, always looking to promote the
hobby, has developed an excellent program
that uses simple model airplanes to teach
middle school math and science. The
AeroLab CD contains instructional videos,
classroom handouts, and more, so that a
nonmodeler teacher can help kids build and
fly tethered, rubber-powered model airplanes.
They use the flights to scientifically
determine airspeed, distance flown, and how
variables (such as ballast) affect results.
I have helped present this program to
teachers across the country. They are excited
to see it, and they rave about the response
from their students.
The AeroLab CD shows the tether rig as
an ultrasimple nail in a wood block, taped to
an upended trashcan. Being modelers, the
demo team initially got spiffy custom-printed
traffic cones with specially made tether
assemblies that fit neatly into the tops of the
cones. They looked great.
The teachers were impressed but kept
asking where they could get the orange rubber
cones and the machined tether pins. After
awhile it occurred to us that this was another
instance of nonmodelers seeing things
differently from how we do. The teachers
couldn’t imagine doing without the fancy
equipment we had shown them.
We model airplane people figured that
since we would be using the demo setup so
much, it was worth making a rig of which we
could be proud. We expected the schoolroom
tether to be more makeshift, since it was
temporary.
After adjusting our mind-set to match that
of our clientele, we relegated the cones to
traffic control around the circle and got an old
box or trashcan to serve as the tether tower.
Sure, it looks lousy, but the whole
demonstration is now more effective than
ever. The teachers see an easy-to-replicate
setup instead of the fancy special stuff that
modelers love.
I built my own tether tower for local use,
and my utter lack of craftsmanship produced a
primitive-looking rig. Perfect! Then my
father, Ralph (happy 85th birthday, dad), asked
to borrow it, just to “throw some paint on it.”
A consummate builder, he sanded and
finished my shoddy product into a furnituregrade
masterpiece, complete with telescoping
tether pole and a folding carry handle at the
balance point. I love to use this classy setup
for fun-flying, but I hate to see Dad’s face
when I tape a block of wood to an upsidedown
paint bucket for teacher
demonstrations.
This difference in viewpoints between
modelers and the public can also be seen
when someone sees RC flight for the first
time. Kids will commonly ask, “Can I try it?”
with the expectation that they can instantly fly
as well as the pilot.
Although they probably can fly better than
I can, it proves that the training and effort we
put into our hobby does not always show to
outsiders. They see things differently.
The Skyhawks RC club in West Virginia
understands this “viewpoint” issue. The
members carefully arranged their flying field
with protective barriers in the right spots and
then realized that their lush climate would
allow a more scenic treatment. The club
upgraded the field landscaping with bushes
and shrubbery to augment and conceal the
flight-station guard structures.
The grass in front of the flightline is left
higher than normal to detain errant models. A
maze pattern of hedges between the flight
station and the pits provides protection and
beauty. Visitors must be impressed with the
extra-green airfield.
Club President Neil Gibbins says that the
cost was low because the group used extra
plantings donated from members’ homes. The
phrase “going green” is overused, but these
modelers did it with style and practicality.
It’s time again to scare the legal department
with my politically incorrect opinions. I’ve
been corresponding with several people lately
about the kids-on-the-field issue. The AMA
Safety Code is clear; it reads, “Children under
six (6) years old are only allowed on a
flightline or in a flight area as a pilot or while
under flight instruction.”
What about kids running loose in the pits?
That can be a more dangerous spot than a
pilot station. Is the pit area a flightline? Why
the arbitrary age of 6? Eight-year-olds aren’t
known for their mature judgment. (By that
standard, I should be required to remain in the
car.)
This is a rule for which I tend to make
108 MODEL AVIATION
exceptions based on circumstances. I
remember being taken to the field as a small
child and the dazzling, thrilling place it
seemed to be. I was even allowed to operate
the transmitter for a moment. The joyful
impression has lasted all these years, and I
would like all youngsters to experience that
pleasure.
It isn’t tough to figure out the reasoning
behind the AMA rule. Kids have a tendency to
escape our attention and get into trouble.
There’s plenty of trouble available at a busy
RC field.
The Valley Flyers members took on quite a
mission recently at the local field. They hosted
more than 100 children aged 5-10 and made
sure that the kids found out what fun our
hobby is.
The highly organized event had a rubberpowered
FF airplane for each child to build
and fly while waiting his or her turn on a
buddy box with a real gas RC airplane. The
kids were carefully supervised and kept in safe
areas until they could be escorted to the
flightline. How those children will cherish the
memory of their day.
Check out the blurry photo of the guys
chatting in the pit area. I had to take it in a
hurry with my cell phone camera to capture
the moment. Look carefully, and you will see
Pat Kinne with his grandson, Andrew, tucked
close.
Andrew has his hands over his ears and a
big grin on his face as he takes in the scene.
Pat is chatting with the guys, but he keeps one
or both hands on Andrew at all times.
There was a very strong bond between the
two. It was clear that Pat would have lifted the
boy from harm or shielded him with his own
body if need be. It doesn’t get any better than
this, and I would have a hard time strictly
applying the AMA rule to such a
circumstance.
This is not an official AMA position, but I
think that sometimes there can be flexibility in
the rules, depending on the situation. In this
case, the risk was so tiny and the benefit was
so large that an exception was in order.
I’ve got my flak jacket on now, ready for
dissenting e-mail. Please put “MA” in the
subject line so I know that your message isn’t
from some lowlife spammer. Paper letters can
be sent to the address below. Your comments,
suggestions, and corrections are always
welcome. MA
Sources:
Dave Gee
Box 7081
Van Nuys CA 91409
AMA’s AeroLab program:
www.modelaircraft.org/education.aspx
Tri State Model Flyers Inc./Skyhawks Limited
Partnership
Robert Garner
[email protected]
AMA Safety Code:
www.modelaircraft.org/files/105.pdf
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