A Guide to Silent Flight

[Zach]

A Guide to Silent Flight

Feeling down? Petrol prices, mortgage and credit card payments
all going up? Get a lift back up in the air. Get an eco-friendly
model sailplane.

Sailplanes, also called gliders, fly atop rising air. There is no
engine noise, only the sound of your heartbeat as you watch your
model sailplane become a speck in the sky. How do you get your
model sailplane back? How did you get it up there in the first
place? What sort of things can you do with your model sailplane
when it is in the air?

A model sailplane, just like the real thing, is constantly flying
downwards through the air. It must do so to maintain airspeed to
provide lift for the wings and airflow over the control surfaces
to give the pilot control. But when the air is rising faster than
the sailplane is falling then the sailplane can also rise, riding
atop the rising air.

Rising air occurs either through thermal lift or slope lift.
Thermal lift involves heat. Even in the winter months, there are
occasions when the ground warms to temperatures higher than the
air above. As you know with a hot-air balloon, warm air rises.
These pockets of air make perfect elevators for a model sailplane
to rise on. But such rising columns of air are invisible. So the
art of thermal soaring is to find a strong thermal, and then to
stay in it to rise as far as you can. If you are flying 'point to
point' then to leave that thermal to fly in the direction you
want to go while at the same time seeking out your next thermal
to lift you up again before the prevailing force of gravity
brings your model sailplane inevitably back to earth.

Slope lift, by contrast, relies on the wind and a hill. The hill
forces the approaching wind upwards, along with your plane. Great
slope soaring sites are invariably found where there is a
prevailing wind and a long ridge to create a smooth and constant
upward wave of air.

Without thermal lift or slope lift, a model sailplane will fall
inexorably back to earth. The radio controls allow you to guide
your plane to seek out lift and if you are flying from point to
point, to move from one source of lift to another in the
direction you want to go. And eventually, of course, to bring
your sky warrior down to a smooth landing.

There are several methods of launching a model sailplane for a
ride on air. The most basic and obvious method is to simply throw
the plane with either a javelin or discus style launch. The plane
gains about 50 feet of altitude from the momentum of the throw –
then you have to hope like crazy that you are going to find lift
before gravity brings it inevitably earthward again. This is
where slope soaring has a major advantage because as you launch
your model sailplane off the slope you know the lift is there
from the oncoming breeze.

Bungee, or hi-start, launching sends a model sailplane skywards
like an arrow. The plane is attached to a line connected to
elastic tubing that is secured to the ground, or to a winch. Pull
the plane back, let it zoom into the air, and grab the radio
control. Better, of course to have two people involved so you
have control at all times.

Another launch method which emulates full size gliders involves a
second powered model airplane to tow the sailplane up and away.
This is a nice way of combining a number of modelling and flying
disciplines with the towline released by a separate servo
actuation.

And yes, though some view it as cheating, there are model
sailplanes that feature an electric motor for initial launching
and for regaining altitude whenever required. The motor has
folding propeller blades that fold back when the motor is not
running to remove the propeller blades from the airflow where
they would otherwise contribute nothing but drag.

Though it is quite thrilling to watch your model sailplane soar
ever upwards, and to remain there due to your skill in seeking
out new thermals, there is still more your model sailplane can
show you. Slope soaring off a hill usually involves a constant
wind and lift, so flyers are not so concerned about losing
altitude in a hurry. So diving from altitude makes for speeds up
to 100 mph. Then that competitive edge creeps in again and the
slope is where most gliders compete.

Racing is either done style where your plane’s flight is
timed, or man-on-man style where you actually race another plane.
Sailplane combat, (SSC), is something else again where your
objective is to knock your opponent out of the sky and score a
‘kill’. Because they obviously crash often, combat sailplanes are
made out of foam for easy rebuilds and will literally bounce off
the ground due to their forgiving and robust construction.

The Academy of Model Aeronautics, (AMA), features several Special
Interest Groups to assist the silent flier. The League of Silent
Flight (LSF) provides rules for racing, aerobatics, and a series
of thermal tasks. The RCCA offers combat guidance and events. The
NEAC offers guidance for electric-powered sailplanes.

(LSF) League of Silent Flight: http://www.silentflight.org
(RCCA)Radio Control Combat Association, http://www.rccombat.com
(NEAC) National Electric Aircraft Council,
http://www.electricaircraft.org

So there you have it, beautiful, elegant, thermal soaring model
sailplanes or robust, knock 'em down combat kills with cheap,
quick to build foamies. Model sailplane soaring is just as
exciting as powered flight. So get yourself a model sailplane and
get out there and give it a go.

Bruce Bird makes it easy for the beginner to quickly get a grasp
of the broad range of exciting activities that make up airplane
modeling. To receive his free 5 part mini-series visit
http://www.modelairplanesecrets.com/soaring.html