Safety Comes First - 2012/03

98 Model Aviation March 2012 www.ModelAviation.com
Prevent uncontrolled energy releases
safety comes first
Dave Gee
[email protected]
I was told this column would appear
in the first newly revamped issue of
MA—completely redesigned and
everything. I am still allowed to type the
column while wearing my lucky T-shirt
with the stains, but I am now required
to wear a necktie as well.
In all seriousness, I get a tremendous
kick from this gig. When I was younger,
I was inspired by model magazine
columnists such as Bill Hannan, and
now he occasionally sends kind words of
encouragement and advises me to keep
my day job. Cool!
Thanks to all of you loyal readers, and
please keep those emails coming.
Energy Sources
One of the earliest challenges of
aeromodeling was to find ways to safely
carry sufficient energy in miniature flying
machines. Flight requires plenty of power,
and pioneer modelers tried running
models on everything
from acetylene gas to
gunpowder. Exciting is
not a strong enough word.
Rubber bands were
found to be the best way
to store power, at least
until gasoline engines
became small enough.
Today, high-tech battery
systems are big. What
will be next?
Every method of storing and carrying
power has its own advantages and risks.
A novice modeler must learn how to
safely refuel his or her model’s power
system. Even glider pilots use stored
energy to get their models off the
ground. A miniature energy system can
be troublesome if not given proper care.
“Uncontrolled release of stored
energy” is a nice way of saying that
something bad happened. Many of our
hobby’s safety issues involve
the unexpected release of
energy. When it’s a surprise,
it’s usually a bad surprise.
I had an email discussion
about storing energy via
rubber winders with Mike
Pykelny, who runs Starlink-
FliteTech International
Model Products. He had
some extra winders to give
to the middle school airplane club with
which I work. The geared winders he
sent are for smaller models with up to
two loops of 1/8-inch rubber.
Mike’s customers fly rubber-powered
aircraft, but not like the little sport
airplanes you might see in a school yard.
These big models range from P-30s to
F1Bs to Unlimited, and their rubber
motors have enormous power packed
into the twisted strands. Mike sells
heavy-duty winding stooges to hold the
PLUS:
> Propeller bites owner
> Expansion motors
bursting into popularity
> Two Kens, two emails
> Identify an airplane
and get plans
They say that aviation is growing, and this topiary jet airliner proves it. Is this
photo real or is it a plant?www.ModelAviation.com March 2012 Model Aviation 99
models, and beefy, geared winders that
can handle the load.
If you visit a field when these airplanes
are being “fueled,” you’ll notice that
people stay away from either end of the
stretched rubber bands. Those motors
sometimes have bobbins or metal hooks
on the ends and can suddenly break,
snapping someone into the next county.
Sometimes there is just a broken strand
or two in a larger motor, so there is only
a partial “uncontrolled release” of energy.
I’ve heard that rubber has a higher
power-to-weight ratio than gasoline, and
pilots take this danger seriously. They
may joke about protecting the model
before their own fingers.
Those who fly smaller, rubberpowered
models understand that even
a tiny broken motor can cause an injury,
especially to one’s eyes, so winding is
done at the safest angle and direction.
When gas engines came into fashion,
modelers had to learn to deal with
highly explosive liquid fuel and fumes
that could ignite from unexpected
sources. There have been some hard
lessons learned throughout the years,
but pilots still take chances at the field
by carelessly handling flammable fuel.
There is no excuse for having ignition
sources near a fueling area, and we
should all know better. I’ve heard
more than one report about a fire that
mentioned how the lawn mower gas
was in a proper can, but the airplane
fuel was stored unsafely—contributing
to structural damage. In one case, it
caused a fire.
The new leader in our hobby is
electric power, and batteries have
improved by leaps and bounds. The
early LiPo cells were involved in
numerous fires, but now either the
packs are getting better or we are
getting wiser and more cautious about
handling, storing, and charging these
high-tech batteries.
I am wary of even the little ones I use
on my indoor RC airplanes. I can only
imagine the damage that could result
from one of them igniting, so I keep
them in a storage box that (I hope)
would contain an uncontrolled release of
energy without burning my home down.
Pilots who use larger packs must
worry after seeing Internet videos of
bursting/flaming batteries. There are
plenty of good storage products available
now, and it is easier than ever to see that
LiPo cells are properly contained during
storage, travel, and charging.
We seem to be coming full circle,
because now there is renewed interest
in some old power systems. CO2
motors are generally small, but the refill
tanks can be big. Using compressed,
pressurized liquid at a hot airfield brings
new problems.
The paintball industry has helped.
Modern tanks have pressure/
temperature relief valves, and are
inexpensive compared to welding-type
tanks. I use paintball tanks and refill
services for my CO2 needs.
Compressed-air systems are gaining
popularity. Mass-produced units are
found in Air Hogs toys, which can be fun
despite their limited power and duration.
Some skilled modelers are working on
refined compressed-air motors that have
astounding power and long runs.
In the past, a brass tank was
handmade and sometimes wrapped
with wire for extra strength. Modern
fliers found that certain metal beverage
cans can be cut and joined into strong,
lightweight cylinders that will reliably
hold the “fuel” for an expansion motor.
Deliberate abuse of the new tanks
showed that even when they fail, there
is no dangerous shrapnel because the
lightweight material is so flexible.
Most pilots take great care when
making and filling the tanks. I have
one of the new prototype motors and
it is truly a gas to run! If they become
available for purchase, you will see a
plug here.
We have a body of knowledge
in our sport from many decades
of experimentation, successes, and
mistakes. Whether we are using the
newest high-tech gadget or a replica of
something 100 years old, let’s learn from
the mistakes of others so we don’t have
our own incidents.
Hobby Knife
Sharp-eyed Ken Achee sent me an
email about a hobby knife he saw in one
of my photographs a few months back.
He noticed that it had a triangular rubber
piece slipped over the round handle
to keep it from rolling off the table
and stabbing my foot. It’s been a while
since the last mention of this simple, yet
Can the rubber motor in this OFFC Pursuit store more energy per pound
than gasoline? It depends on how you measure it.
Guess what airplane this is and win
a set of plans. Hint: The photo was
taken at the Flying Leatherneck
Historical Foundation and Aviation
Museum in San Diego.effective, trick and Ken wanted to know
where to find an anti-roll sleeve.
Commercial products such as this can
be hard to find. Your local art store might
have a bottle of them next to the cash
register. I couldn’t find any sellers on the
Internet. Some modelers just add a “flag”
of heavy tape to the handle. Others glue
a piece of dowel crosswise onto the knife,
or screw a small bolt into the side of it.
Propeller versus Wrist
A different Ken also wrote to me.
Kenneth “Kep” Kepner told me about a
past moment of inattention that still fills
him with embarrassment. Despite that,
he still wanted to share his tale with the
world, hoping that someone else can
avoid making the same mistake.
Kep said that sometimes the
adrenaline and excitement of the first
flight of your latest pride and joy can
cause cerebral disconnect. He wrote:
“Fifteen years ago I was tinkering
with my then-new Astro Hog in the
pits. The O.S. .91 was purring at the
first flip and a buddy was holding the
tail. I reached right over that brandnew
14 x 6-inch maple prop to finetune
it right there, and with God as
my witness, I reached right over the
whirring prop. I heard it hit and then
felt my right wrist burn.
“I was afraid to look down, but only
saw the skin scratched enough just to
leave a little red line of blood. It ended
up leaving a 1½-inch lifelong white scar
that I see every time I look at my arm.
I consider it a very lucky and cheap
reminder. That was over 15 years ago
and I still fly the old Hog.”
Kep did a generous thing by sharing
his accident with us. Please take it to
heart and keep in mind that this could
happen to any of us if we drop our
guard. If you have a close-call story, a
suggestion, or a correction, please drop
me an email. Your name can be withheld
if you prefer to avoid the thrill of
national embarrassment.
Aircraft Photo Quiz
I was overwhelmed by the response
from the last aircraft-identification photo
quiz. It showed the landing gear of anF-82 Twin Mustang, and hundreds of
readers correctly guessed it and received
a Marlow Shark model plan via email.
Want to try it once more? Look at the
cropped photo and tell me what aircraft
it shows. Hint: this airplane was seen at
the Flying Leatherneck museum.
This time the prize is one of my own
designs, so don’t get too excited. As part
of my continuing and transparent plot
to encourage Rubber Sport models,
everyone who emails me will receive
plans for the OFFC Pursuit.
This profile low-winger will fly in
small gymnasiums and easily launch
from the floor. Outdoors, it is stable and
looks racy in the air. You don’t have to
correctly guess to get the digital plans;
just ask for it.
SourceS:
Starlink-FliteTech International Model Products
(858) 231-4994
www.starlink-flitetech.com/index.htm