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Thermal soaring is one of the most intriguing of all aspects
of flying and the Fling DL ARF was designed to excel at
thermal soaring even in the hands of a novice. It can be hard
for the average person to understand how a plane can fly for
hours and gain altitude without a motor! 

Thermals are a natural phenomenon that happen outside, by
the millions, every single day of the year. Thermals are
responsible for many things including forming several types of
clouds, creating breezes, and distributing plant seeds and
pollen. If you have ever seen a dust devil (which is nothing
more than a thermal that has picked up some dust), you have
seen a thermal in action. Their swirling action is very similar to
that of a tornado but of course much gentler. Most thermals
have updrafts rising in the 200 – 700 feet per minute range but
they have been known to produce updrafts of over 5,000 feet
per minute (that’s over 50 miles/hour straight up!) These strong
thermals can rip a plane apart or carry the plane out of sight
before the pilot can get out of the updraft.

Thermals are formed by the uneven heating of the earth and
buildings, etc. by the sun. The darker colored surfaces
absorb heat faster than the lighter colors, which reflect a
great deal of the sun’s energy back into space. These darker
areas (plowed fields, asphalt parking lots, tar roofs, etc.) get
warmer than the lighter areas (lakes, grassy fields, forests,
etc.). This causes the air above the darker areas to be
warmer than the air over the lighter areas and the more
buoyant warm air rises as the cooler, denser air forces its
way underneath the warmer air. As this warm air is forced
upward, it contacts the cooler air of the higher altitudes and
this larger temperature difference makes the thermal rise
quicker. The thermal is gradually cooled by the surrounding
cooler air and its strength diminishes. Eventually the
thermal stops rising and any moisture contained in the once
warm air condenses and forms a puffy cumulus cloud.
These clouds, which mark the tops of thermals, are usually
between 2000 and 5000 feet high.

It takes a lot of concentration to thermal soar effectively. A
sailplane can fly along the edge of a thermal and unless the
pilot is carefully watching the model he may not realize the
opportunity to gain some altitude. Because most thermals are
relatively small (a couple hundred feet in diameter or less at
400’ altitude) compared to the rest of the sky, the sailplanes will
rarely fly directly into the thermal and start rising. Generally, the
sailplane will fly into the edge or near a thermal and the effects
the thermal has on the plane may be almost unnoticeable. As
the sailplane approaches a thermal, the wing tip that reaches
the rising air first will be lifted before the opposite wing tip. This
causes the plane to “bank” and turn away from where we would
like the plane to go.

When you are thermal soaring, try to fly as smoothly and
straight as possible. Trim the plane to fly in a straight line
and  only  touch the controls when you have to. Watch the
sailplane carefully and it will tell you what it is encountering.

When the sailplane flies directly into a thermal it will either
start rising or stop sinking. Either case is reason enough to
start circling (especially in a contest where every second
counts). Fly straight ahead until you feel like you are in the
strongest lift, fly a couple of seconds farther (so your
circle will be centered in the strongest lift) and then start
circling in a fairly tight but smooth turn. When the sailplane
is low the turns have to be tighter to stay in the strongest lift.
As the plane gains altitude, the turns can be larger and
flatter. The flatter the turn, the more efficient the plane is
flying, but don’t be afraid to really “crank” it into a steep bank
when you are low. If you see the plane falling off on one side
of the turn, move your circle over into the stronger lift.
Thermals move along with the wind so as you circle you will
be swept along with it. Be careful when thermaling, that you
don’t get so far downwind you can’t make it back to the field
to land.

If the sailplane is flying along straight and all of a sudden
turns, let the plane continue to bank (you may have to give
it some rudder to keep it banking) until it has turned 270-
degrees (3/4 of a full circle). Straighten out the bank and fly
into whatever turned the plane. If you encounter lift, and you
won’t every time, start circling just as you did when flying
directly into a thermal.

Thermals are generated all day long, but the strongest
thermals are produced when the sun is directly overhead.
10:00 am – 2:00 pm seems to be the best time to get those
“killer” thermals. Some of these thermals can be very large
and you may find it hard to get out of them. If you find
yourself getting too high, don’t dive the plane to get out of
the lift. Sailplanes are very efficient aircraft and they will
build up a lot of speed and could “blow up” in the rough air
of a thermal. The easiest way to lose altitude is to apply full
rudder and full up elevator. This will put the plane into a tight
spin that will not over stress the airframe but it will enable it
to lose altitude very quickly. This is especially helpful if the
sailplane gets sucked into a cloud or it gets too high to see.
The twirling action will give the sun a better chance of
flashing off of the wing and catching your attention. When
you are high enough and want to leave the thermal, add a
little down trim to pick up some speed and fly 90 degrees to
the direction of the wind. If you are not real high and want to
find another thermal, you may want to look upwind of the
last thermal. The same source that generated this thermal
is probably producing another. Just watch out for “sink”
which is often found behind and between thermals.

As you might expect, with all this air rising, there is also air
sinking. This air is the sailplane pilot’s nightmare that can
really make soaring challenging. “Sink” is usually not as
strong as the thermals in the same area, but it can be very
strong. Down drafts of many hundreds of feet per minute are
common on a good soaring day. These down drafts can

Thermal Soaring

Facts about Thermals

THERMAL FLYING

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Summary of Contents for Fling DL ARF

Page 1: ...ct the buyer is advised to return this kit immediately in new and unused condition to the place of purchase To make a warranty claim send the defective Hobby Services part or item to Hobby Services at this address 3002 N Apollo Dr Suite 1 Champaign IL 61822 USA Include a letter stating your name return shipping address as much contact information as possible daytime telephone number fax number e m...

Page 2: ...d in the Radio Equipment section of the manual Have a friend get a Fling DL ARF too and you can have first up last down contests or compete against each other trying to land the Fling DL ARF closest to a certain place a spot landing Have fun with your new Fling DL ARF For the latest technical updates or manual corrections to the Fling DL ARF visit the Great Planes web site at www greatplanes com O...

Page 3: ...ke your time and follow the instructions to end up with a well built model that is straight and true This is a partial list of items required to finish the Fling DL ARF that may require planning or decision making before starting to build Order numbers are provided in parentheses 4 channel radio Y harness HCAM2500 or two 12 300mm extensions HCAM2100 utilizing a radio with flaperon mixing Great Pla...

Page 4: ...dealer If a hobby shop is not available replacement parts may also be ordered from Tower Hobbies at www towerhobbies com or by calling toll free 800 637 6050 Parts may also be ordered directly from Hobby Services by calling 217 398 0007 or via facsimile at 217 398 7721 but full retail prices and shipping and handling charges will apply Illinois and Nevada residents will also be charged sales tax I...

Page 5: ...lastic pull pull elevator turnaround 8 Decal sheet Before starting to build take an inventory of this kit to make sure it is complete and inspect the parts to make sure they are of acceptable quality If any parts are missing or are not of acceptable quality or if you need assistance with assembly contact Product Support When reporting defective or missing parts use the part names exactly as they a...

Page 6: ... Use the pushrod and servo cover to position the servo NOTE If the CA is not spread thin enough it might wick into the servo and cause the gears to bind Do Not Use Thin CA 6 From the 1 16 x 6 1 6mm x 150mm pushrod make a pushrod with Z bends on each end that goes from the servo arm to the center of the hinge line 7 Cut the covering from the control horn slot on the bottom of the aileron Fit the pl...

Page 7: ...ive amount of 30 minute epoxy Join the wing halves together Ensure that the left wing remains flat and that the right wing tip is 3 1 8 79mm from your work bench and can remain that way undisturbed until the epoxy has hardened Remove any excess epoxy with a paper towel and denatured alcohol being careful not to disturb the joint Hint Use masking tape to hold the wing together while the epoxy harde...

Page 8: ...face Align the carbon support in the fin with the carbon fuse Check that the fin is perpendicular to the work surface If the fin is not perpendicular adjust the fin slot so that it is perpendicular Glue the fin to the fuse with thin CA DO NOT remove the covering from the fin 5 Drill four 1 16 1 6mm holes in the locations shown in the sketch 6 Slide the plastic elevator turnaround through the 1 8 3...

Page 9: ... CA 9 Glue the stab to the fuse making sure it is aligned with the wing and that the TE of the elevator is 1 8 3mm in front of the fin 1 Trim the covering and slide the two sided plywood control horn through the rudder center it and then glue it with thin CA 2 Slide the single sided plywood control horn into the elevator and glue with thin CA 3 Install the aileron extensions under the servo tray A...

Page 10: ...left side and cut it midway back on the fin 8 Slide the cut string that is on the right side of the fuse through the elevator turnaround 9 Plug the servos and battery into your receiver Turn on the transmitter to center the rudder and elevator servos 10 Tie the cut ends of the string to the elevator control horn The strings need to have some tension on them and the elevator needs to be aligned wit...

Page 11: ...mix steel shot with epoxy and then pour the correct amount into the nose Work in small increments of weight double checking the CG each time 3 Route the antenna outside the fuselage and tape it to the carbon fiber rod 1 Use scissors or a sharp hobby knife to cut the decals from the sheet 2 Be certain the model is clean and free from oily fingerprints and dust Prepare a dishpan or small bucket with...

Page 12: ... on you should be able to walk at least 100 feet away from the model and still have control Have an assistant stand by your model and while you work the controls tell you what the control surfaces are doing If the control surfaces do not respond correctly do not fly Find and correct the problem first Look for loose servo connections or broken wires corroded wires on old servo connectors poor solde...

Page 13: ... aircraft are allowed at or in the front of the flight line Intentional flying behind the flight line is prohibited 4 I will operate my model using only radio control frequencies currently allowed by the Federal Communications Commission 5 I will not knowingly operate my model within three miles of any pre existing flying site except in accordance with the frequency sharing agreement listed in the...

Page 14: ...sible for a good high launch Do not use too much arm in this section Just let the rotation of your torso speed the plane up Release Foot position 5 By this time in the launch the plane will be trying to climb on its own Just release your fingers and let the plane fly out of your hand Try to release it directly into the wind Recovery Foot position 6 This last step is just to catch your balance and ...

Page 15: ...the controls when you have to Watch the sailplane carefully and it will tell you what it is encountering When the sailplane flies directly into a thermal it will either start rising or stop sinking Either case is reason enough to start circling especially in a contest where every second counts Fly straight ahead until you feel like you are in the strongest lift fly a couple of seconds farther so y...

Page 16: ...o try to fly in The faster the wind is blowing the stronger the lift and turbulence will be To fly off a slope stand near the edge and throw the sailplane nose down into the wind As the sailplane flies out into the band of lift it will begin to gain altitude Turn and fly parallel to the slope and make all of your turns into the wind especially when you are close to the slope You will be surprised ...

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