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flying yoUr Model
Preflight Trimming
We strongly recommend that before you fly your new
model, you first perform a test glide. Pick a flat spot
that has soft, tall grass and is free from obstructions.
You should always check out the performance of
the aircraft, as well as your performance as a pilot.
The test glide will allow you to make corrections to
any building or control defects that may have been
overlooked. The test glide should be done with an
assistant on a calm day.
Tip
: A good time for a test glide is either very early
in the morning or at dusk when the wind is calm. It
is important to concentrate on what the model is
doing while still having time to think about what you’re
doing. We will assume you have an assistant during
the following steps:
1. Range check your radio system and check the
control throws. Make sure the control surfaces move
in the proper direction.
2. Have the assistant hold the model under the wing
near the CG and run forward until they can sense
the wing developing lift. Don’t release the glider yet.
See if the model wants to lift. If not, add a bit of up
elevator trim and try again.
3. Have the assistant run forward again, this time
a bit faster with the wings level and the nose of the
plane pointed at the horizon. Once the assistant feels
enough lift being generated, have him/her thrust the
model forward in a straight line toward the horizon
and release the aircraft.
4. When the assistant releases the model, watch it
carefully. A properly trimmed aircraft will fly straight,
gliding to a smooth landing about 50 feet away.
If the model pitches nose down, the CG is too far
forward and you have a nose heavy condition. Remove
some weight from the nose, shift the battery aft or
add weight to the tail. If the model pitches nose up
sharply and stalls, you have a tail-heavy condition (the
CG is too far aft), and you need to remove weight
from the tail, move the battery and receiver further
forward, or add nose weight.
5. Turns to the left or right after launch can be
adjusted through the use of right or left rudder trim.
Important
: Make any trim adjustments in small
increments. Large changes can result in abrupt
turns, causing tip stalls and loss of control.
6. If you have to make large trim adjustments on
your transmitter, you may have other problems, such
as warps. Check the wings, elevator and rudder to
make sure there are no warps in the airframe. Make
sure the wings are aligned and mounted properly
on the fuselage. When you have the model trimmed
and the CG adjusted so it glides properly in a “hands
off” manner, return your transmitter trim switches
to their neutral position. Make the appropriate
mechanical linkage corrections to return the control
surfaces to their test glide positions.
7. After you have made the necessary corrections,
test glide the model again to make sure it is trimmed
properly with the transmitter trims in neutral.
Simple Soaring
What are thermals
The first step to thermal flying is to have a basic
understanding of what thermals are and how they
work. If you have some concept of how a thermal
works, it will help you know where to search for them.
A thermal is basically rising air. The temperature
of the ground is not consistent. Different textures,
colors and even weather condition can cause uneven
ground temperature. Warmer ground temperatures
heat up and form warm air bubbles. The bubble will
hug the ground until something causes it to break
from the surface tension and release into the air,
much like a soap bubble breaking away from the
water’s surface. Once released, perhaps by a tree
line, shed, building, etc., the thermal bubble rises up
and continues to gain energy until it is fully developed
many thousands of feet above.
Thermals are typically stronger later in the day,
since after a day of sitting in the sun, the ground
has more time to generate heat. There are still
thermals in the morning and evening; however, and
they behave differently. Morning thermals are very
narrow, meaning they have a small diameter and do
not typically go very high; perhaps 20–400’. However,
there are many small thermals in the morning,
making it an excellent time of day for learning how
to fly sailplanes. Morning thermals are very defined
and are more safe, as they typically don’t go too high
and not as violent as fully-developed thermals. Also,
there are many smaller thermals close together in
the morning, and this will allow you to hop from one
thermal to another with ease.
Evening thermals are typically large, warm air
masses meandering through the sky. They are usually
very smooth with soft edges. The middle of the day
(noon to 4:00 p.m.) is when the thermals are at
their strongest. The flip side to this is that with every
thermal there is also sink. Sink is the surrounding air
that is left by the thermal leaving the ground. Typically
sink is on the downwind side of the thermal. Sink is
created when warm, rising air is displaced by colder,
descending air. This is not necessarily a bad thing,
because where there is sink, there is also lift close
by. The trick is to find lift before you have to land.
Thermals can also start at ground level. And if you
are skillful enough, you can catch a thermal from 20
or so feet and ride it up to 1000’.
How to catch a thermal
One of the best pieces of advice we could give you
is to always have a planned search pattern when
looking for thermals. Even the most seasoned thermal
competition pilots will have a search plan before
launching. This is one of the basics of thermal flying.
If you have a plan based on sound thermal logic,
chances are you will more than likely find a thermal.
As thermals don’t typically stay in the same location
for long, you can’t just go to the last place you found
a thermal. Often we hear pilots say, “Fly over those
trees. There is always lift there.” In reality, this may
have been a location where they did in fact find a
thermal; however, it may not always be there. Our
advice is to have a planned search pattern, ensuring
you cover as much ground as the model is capable of
before landing. Many people just fly straight upwind.
This is ok, yet we would suggest working in an “S”
pattern, which will increase your search pattern. You
can still keep working your model upwind; however,
you are going to cover a lot more sky for the same
loss of height if you work your model in an “S” type
flight pattern. You don’t have to go out of sight each
way either; perhaps 300’ either side of center will be
sufficient. Also, be on the lookout for ground markers.
You can’t see thermals, yet you can see things that
identify them. These are your ground markers.
Wind direction and velocity are also great thermal
indicators. Often colder, descending air fills in the
hole that a thermal leaves as it moves along the
ground. Traveling downwind of a cooler air mass
might be a good indication of where a thermal may
be. If the wind has been steady in your face and you
feel a distinct change of direction, perhaps shifting
more from your left, then there is a good chance
that the thermal is to your right and slightly behind
you. The same would apply if the wind shifted to blow
from the right, as there would be a good chance that
the thermal is to your left and slightly behind you. If
you feel the wind strength increase, yet stay blowing
straight into your face, then the thermal is directly
behind you. Finally, if the wind reduces in velocity, or
even stops from a steady breeze, then the thermal
is either ahead of you or right above you. Basically,
the thermal will be where the wind is blowing toward.
Always pay attention to the general wind direction and
look for changes in both its direction and velocity for
signs of thermals.
Other good indicators are birds. Many birds are
capable of soaring, and you will often see them
soaring on the thermals. Before launching, always
check for birds. Pay close attention to how they are
flying. If they are flapping hard, chances are they
are also looking for lift. If they are soaring without
flapping, then there is a good chance they are in lift.
Birds also like to feed on small insects. As thermals
initiate from the ground, birds will suck up small
insects sent into the air. A circling bird is a great sign
that there is lift.
Another idea that works well is to fly over areas that
are darker, often a freshly ploughed field, a parking
lot, dirt, or anything with a dark color. Since darker
colors absorb more heat, they could be a good source
of generating thermals. One little test you may like
to do is to paint various colors on a sheet of paper
and place them in the sun. After 30 minutes or so,
go and check which colors absorb the most heat.
Once you know what colors make the most heat, look
for natural areas on the ground that match these
colors and use those as locations for thermal hunting.
While these are just a few helpful search options for
you, we are confident that as your knowledge and
understanding of thermals improve, you will start to
have your own special thermal hunting locations.
