Gliders or sailplanes are a kind of aircraft that differ from the rest
by their ability to fly great distances without the need for an engine
or propulsion of any kind
even gaining altitude during their flight
but, how is this possible?
That is what I will answer today in this video.
Welcome to Joyplanes RC 2.
[INTRO]
Personally, gliders are my favorite aircraft
because they don't need an engine to fly
and because of the long impressive wingspan they have
but their long wings have a reason to be.
Let's start with the basics
we know that an airplane can fly or glide without an engine
but in the process it will gradually lose altitude and depending on its weight
aerodynamics and other physical facts it can go down faster
this happens with every airplane
regardless of whether they are gliders or not
without an engine it is possible to fly for some distance and land
as long as a constant speed and descent rate is maintained
to be in a stable flight
but the gliders are designed to take full advantage
of this balance of forces
the gliders are made with lightweight materials
and the weight is distributed at strategic points
in an efficient manner to improve air penetration
and the configuration of their wings allow them to have
more lift with less aerodynamic drag
as a result their glide ratio is one of the most efficient
among all airplanes
The glide ratio is the distance that the aircraft can travel
in respect to the lost altitude
for example a Cessna 172 has a glide ratio of 9 or 9: 1
which means that if its engine stops working
it can fly from 100 meters of height for about 900 horizontal meters
in modern gliders this gliding ratio
can be between 40: 1 to 70: 1
which means that if a glider has a 50: 1 ratio
then it could fly for 50km if it starts at 1km high
making it capable of covering long distances in this way
Still it is impossible to gain altitude for an aircraft
that moves through a static atmosphere
without the use of propulsion of some kind
luckily our atmosphere is not static at all
to gain altitude
gliders can take advantage of various atmospheric phenomena
There are three main phenomena
the ridge lift
thermals
and wave lift
Thermals are the most mentioned way
to gain altitude in a glider
these are columns of hot air that is generated by a surface
heated by the sun
this air becomes less dense
than the surrounding air
and begins to rise rapidly
the glider when entering a thermal
can begin to fly in a circular pattern
to stay inside it and gain altitude
until the thermal disappears or weakens
the other way to gain altitude is with the ascending
currents of air on the slopes of the mountains
this is simply air that is forced to climb the mountain
and a glider can take advantage of this current
to gain or maintain altitude
the closer to the slope the stronger the climbing rate
the last form is the use of air waves that are generated
after the air passes through the mountain
these waves extend for several kilometers
and are invisible waves
similar to the waves of the sea
Using these strategies to gain altitude
a glider can stay in flight for many hours
this is totally free and clean energy
that glider pilots gather and manage
to get the most out of it
However
to make a glider take off
you need an airplane
that will tow it to an acceptable altitude
where the glider can start by itself
another way is to take off with a tow winch from the ground
but the altitude that it gains is not as much
as that of the first method
hopefully on a sunny day the glider can take a thermal
that makes it fly longer
others Wways to take off a glider is from a mountain
with a system of elastic ropes on a hillside
or by having a retractable propulsion system
integrated into the glider that is only used to take off
or gain the altitude needed
Why long and thin wings?
the thin wings
generate less induced aerodynamic drag
than the common wings that are seen in self-propelled airplanes
this way the glider can pass through the air with less difficulty
obtaining the same lift and losing less speed than other airplanes
another factor that helps for better Aerodynamics
is the design of the fuselage
making everything as smooth
thin and aerodynamic as possible
which is why the pilot enters the cockpit
in much the same way as a Formula 1 driver in his car
(almost lying down).
the wings are also measured by aspect ratio
glider wings have a high aspect ratio
and war airplanes wings have a low aspect ratio
war or acrobatic aircraft wings generate
more induced drag than thin wings of gliders
but because they are short wings
they are more maneuverable
maneuverability is a priority in warplanes rather than fuel efficiency
in the case of gliders it isn’t necessary to make quick maneuvers
so priority is given to efficiency sacrificing maneuverability
The wings end up being naturally long
because a large wing area is required
with the restriction of a reduced cord wing
to minimize drag
Gliders are built to be very light but strong at the same time
they even become so light
that you have to put more weight on the wings
to improve their penetration and speed characteristics
this is done by filling the glider with water ballast
in special tanks inside the wings
the total weight of this ballast can be even higher than the pilot's weight
the water can be drained during the flight
in case the thermals are not so strong
and must also be drained before landing
In the beginning gliders were made out of wood with fabrics or metal
and then the use of composite materials
Fiberglass
carbon fiber and kevlar was introduced
achieving a huge resistance with a very light weight
Flight instruments
Gliders are equipped with the basic instruments
that can be found on any other aircraft
except for flight instruments associated
with the use of an engine
the most used and necessary instruments
are the anemometer
Altimeter
Variometer
and compass
You can also find a turn coordinator
Sometimes an accelerometer
and tools such as a radio
and a GPS
One of the most basic indicators
that are still used even in high-performance gliders
is the yaw string
it is a small string that is placed on the outside
in front of the pilot that indicates the wind direction
in regarding to the glider flight
if the string is not centered
it must be corrected using the rudder
and that way the pilot makes sure that he is flying efficiently
Otherwise
that means that the fuselage is off
by some degrees in respect to the flow of air
and that generates a lot of drag
It is important to be aware of the speed at all times
since if the glider gets to slow than recommended
it is possible to lose some control and go into a stall
also depending on the design
there is a specific speed in which the glider
has the maximum efficiency between descent and distance traveled
to measure the speed at which the glider goes with respect to the wind
the anemometer is used
the airspeed is different from groundspeed
the variometer indicates the speed of climb and descent
this instrument is super important
to know when the glider is beginning to climb
usually when it enters a thermal
and thus stay within the thermal
the gliders are equipped with a system that generates a sound
depending on the speed of ascent or descent
with this sound you can more easily identify
if the glider is going up or down
without having to look at the indicator all the time
as you have already seen in this video
gliders are a very interesting type of aircraft
especially because they don’t burn any type of fuel
to stay in flight
only the natural energy available in air currents
nowadays gliders are used for sports and recreational purposes
I give special thanks to Stefan Langer
who is a glider pilot
you can see his channel in the description of this video
Making the animations
the editing and post production in general of this video
has taken me a couple of months
it would be great if you could support me
through a small donation
link in the description
or even a like and share is also appreciated
also consider subscribing to not miss more videos like this
or videos in which I make rc airplanes
drones or similar projects
for now I will see you in the next project