Instructions

29
Building instructions
in it. You will need to control the glider constantly to keep it centred, as
you can expect the most rapid climb rate in the core of the thermal. Once
again, this technique does demand some skill.
To avoid losing sight of the machine be sure to leave the thermal in good
time. Remember that a glider is always easier to see under a cloud than
against a clear blue sky. If you have to lose height in a hurry, do bear the
following in mind:
The structural strength of the LENTUS is very great for this class of model,
but it is not innite. If you attempt to destroy the model forcibly, please
don’t expect any sympathy or compensation from us (alas, we speak from
experience).
59. Flying at the slope
Ridge soaring is an extremely attractive form of model ying. Soaring for
hours on end in slope lift, without needing any outside aid for launch-
ing, must be one of the nest of modelling experiences. But to “milk” a
thermal to the limits of vision, bring it down again in a continuous series
of aerobatic manoeuvres, and then repeat the whole show - that must
surely be the last word in model ying.
But take care - there are dangers for your model lurking at the slope.
Firstly, in most cases landing is much more difcult than at a at eld site.
It is usually necessary to land in the lee of the hill where the air is turbulent;
this calls for concentration and a high-speed approach with last-minute
airbrake extension. A landing on the slope face, i.e. right in the slope lift,
is even more difcult. Here the trick is to approach slightly downwind, up
the slope, and are at exactly the right moment, just before touch-down.
60. Aero-towing
An ideal combination for learning to aero-tow, and for actual aero-tow-
ing, is a FunCub XL and a LENTUS.
For the tow you require a 20 m length of braided cable of 1 to 1.5 mm Ø.
Tie a loop of nylon line (0.5 mm Ø) to the glider end of the cable; this acts
as a “weak link”, in case the tow should go badly wrong.
A loop in the other end of the towline should be connected to the aero-
tow coupling of the FunCub XL. Assemble the models, connect them as
described, and set them up directly into wind, the glider behind the tug.
Check that the towline is resting on top of the FunCub’s tailplane. The
tug now rolls forward until the towline is taut, and only then should the
tug’s pilot apply full-throttle. Both aeroplanes accelerate: the tug stays
on the ground initially, while the glider lifts off, but the glider pilot keeps
his model ying low above the ground, directly in the wake of the tug;
the tug can now lift off safely. The two models should be kept climbing
steadily, even through turns. Avoid ying directly over your heads during
the rst few attempts at aero-towing, as it is difcult to detect the models’
attitudes from this angle. To drop the tow, operate the transmitter control
which opens the tow release mechanism.
61. Electric flying
With the electric version you have the optimum level of autonomy and
independence. You can y from a at eld and carry out about seven
climbs to a sensible gliding height (around 150 m) from a single battery
charge. At the slope you can also keep the electric power system as a
“lifebelt”, i.e. you only use the motor to “keep aoat”, and avoid landing
out, i.e. landing at the bottom of the slope when the lift fails.
62. Flight performance
What is meant by a glider’s performance?
The two most important parameters are sinking speed and glide angle.
Sinking speed is a measure of the vertical height lost per second relative
to the surrounding air. The sinking speed is primarily determined by the
wing loading (weight relative to wing area). Here the LENTUS offers a
really excellent performance - much better than conventional models - as
its wing loading is so low. This means that only slight thermal assistance
is necessary (warm air rising) to cause the model to gain height. Wing
loading is also the main factor in determining the model’s airspeed -
the lower the loading, the slower the model. Low airspeed means that
the model can be turned extremely tightly, and this is also advantageous
when thermal ying, as areas of lift are usually very small when close to
the ground.
The other important parameter in glider performance is the glide angle.
This is stated as a ratio, i.e. from a particular altitude the model ies such
and such a distance. The glide angle increases as wing loading rises,
and at the same time - of course - the model’s airspeed increases. This
becomes necessary if you wish to y in relatively strong winds, and when
you need “energy retention” for ying aerobatics.
For thermal ying you need a good glide angle too, as this is the key to
ying across areas of “sink” (the opposite of a thermal) quickly, so that
you can seek out another thermal.
63. Safety
Safety is the First Commandment when ying any model aircraft. Third
party insurance is mandatory. If you join a model club, suitable cover
will usually be available through the organisation. It is your personal re-
sponsibility to ensure that your insurance is adequate (i.e. that its cover
includes powered model aircraft). Make it your job to keep your models
and your radio control system in perfect order at all times. Check and
observe the correct charging procedure for the batteries you are using.
Make use of all sensible safety systems and precautions which are
advised for your system. An excellent source of practical accessories is
the MULTIPLEX main catalogue or our website www.multiplex.de
MULTIPLEX products are designed and manufactured exclusively by
active modellers for practising modellers. Always y with a responsible
attitude. You may think that ying low over other people’s heads is proof
of your piloting skill; others know better. The real expert does not need
to prove himself in such childish ways. Let other pilots know that this is
what you think too, as it is in all our interests. Always y in such a way that
you do not endanger yourself or others. Bear in mind that even the best
RC system in the world is subject to outside interference. No matter how
many years of accident-free ying you have under your belt, you have no
idea what will happen in the next minute.
Before every ight, check that the battery, the wings and the tailplane
are attached and rmly seated. Check in turn that each control surface is
operating correctly!
We - the MULTIPLEX team - hope you have many hours of pleasure
building and ying your new model.
MULTIPLEX Modellsport GmbH &Co. KG
EN