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Basic introduction to aero-modelling
This is a very basic
introduction to aero-modelling.
Hopefully
I have tried to cover all the basics. As my knowledge of electrickery is
limited I have only briefly discussed it. If you have any questions
please contact me, or speak to an experienced fellow member. Chris Berry, November 2010
Engines There are 2 main types of engine.
Glow engines
which use a glow plug to ignite a methanol, and oil based model fuel.
The fuel is bought ready mixed and often contains Nitro, usually of
around 5% or 10% to give more power. There are lots of type to choose
from.
Petrol engines
which use a spark to ignite a petrol and oil mix. This fuel is mixed by
using normal high octane unleaded petrol and a good quality 2 stroke
motorbike oil. Glow engines are generally 2 stoke, or 4 stroke.
2 stroke engines
are very basic engines and are used mostly in sport models. They are the cheapest engine available and are the
sort of engine you would use in your first model.
4 stroke engines
are generally used in scale models, as the noise more realistic. These engines generally cost a little more than 2
stroke and give slightly less power. There are many manufacturers and hundreds of engines
to choose from. Examples of 2 stroke engines are Irvine, ASP, OS,
Thunder Tiger, Super Tigre, SC. Examples of 4 stroke engines are Saito,
ASP, OS, SC, Magnum, Laser For your
first model you will use around a
40
to
46 size engine.
What does that mean? Model aircraft engines are measured in cubic inches.
There are 16cc (cubic centimetres) to the cubic inch. So, a 40 size
engine is actually 0.40 of 16cc which equates to 6.4cc. So, a large
engine, a Saito 125 for example is a 1.25 engine, therefore is 1.25 x
16cc which is 20cc. I have had
3 Petrol
engines are generally used for bigger models, which require engines of
more than 20cc. Examples include Zenoah,
Radio There are 5 basic elements to a radio system:
·
Transmitter or
tranny/TX: The box with the sticks and an aerial
·
Receiver or RX:
The black box in the aircraft
·
Servos: The
motors that plug into the receiver and are connected via pushrods to the
control surface
·
·
Switch: To get
things going. There are two types of radio that are available for
model aircraft use. The first and more traditional is 35mhz, this is a
very reliable system that has been around for many years.
35MHZ SHOULD ONLY BE USED FOR MODEL AIRCRAFT. The second is 2.4ghz, this is relatively new and is
becoming more common by the day. Both systems use the above components. The difference
between them is the frequency band.
35mhz: Within the
35mhz FM band there are 36 separate channels numbered 55-90, in theory
each channel is capable of being used at the same time at the same site.
HOWEVER;
if a 37th
operator tries to switch their transmitter on, they will be interfering
with an existing user, causing a frequency clash which could result in a
crash. The range of a transmitter is about 2 miles.
FREQUENCY CONTROL.
At our flying site, like many others, a peg board is used to ensure that
people operating on the same channel, do not switch on their
transmitters at the same time and cause a crash. The process is very
simple. If you wish to fly, place a peg on the channel you
wish to use on the peg board. If there
is already a peg there, then that channel is in use and you
MUST NOT switch
your transmitter on. My advice
is to
ALWAYS CHECK with
fellow modellers at the field before you fly, to ensure that the risk of
any clash is reduced. Do not just rely on the peg board. Most 35mhz radios now use a synthesised channel
selection method, rather than the old way of fitting channel specific
crystals into the RX and TX. The synthesised method involves you
selecting the channel you want to use on the TX and then activating that
channel on the RX.
I WOULD ALWAYS USE THE SAME FREQUENCY AS THIS
REDUCES THE RISK OF HUMAN ERROR AND CLASHES WITH OTHER USERS. You can only fly one model at a time. 2.4ghz operates in a different way. When you switch
your transmitter on it scans for a free channel within that band, and
therefore locks that channel out of the reach of other transmitters,
this elevates the risk of a "shoot down". The peg board system is therefore Semi-redundant,
other than to place a black peg on the top of the board to indicate you
will be flying. I have no experience with 2.4ghz, so will not comment
any further on this method. Anyone wishing to purchase a 2.4ghz radio
should speak to an experienced user of 2.4ghz. Servos There are many different types of radio, receivers
and servos that you can use. For your first model, you are likely to be using 4 or
5 servos, of around 3 to 5 kg/cm torque. (The larger and more
high-performance the aircraft the more force needed to move the control
surfaces and therefore the larger and more powerful the servo needs to
be) Standard servos of around 3 to 5kg will be the sort
you will use for your first few models. Typically they will be priced at
around £8 to £10 each. Popular types are Hitec HS322, HS485, HS81, JR 591,
Futaba 3001. All are perfect for general training and sport
models. Transmitters Transmitters vary in the number of functions. A 6
channel transmitter is perfect for most people. 6 channels means that
the transmitter is capable of operating 6 functions on the aircraft. 4
of these functions will be the basic flying controls; which is all you
will need to begin with. The remaining functions can operate auxiliary
functions such as retracting undercarriage, landing lights or a pilots
arm waving. All transmitters now have model memories. This is effectively a hard disk that stores the
setting for each model. So when you have more than one aircraft, you don’t
have to change the settings, you just switch on and select the model you
want to fly. For your first transmitter I would recommend a JR
2610 (This means 2 aircraft types, Heli and fixed wing, 6 channels, 10
model memories), or a Futaba FF6. However there are many others to choose from. Receivers Similar to that of transmitters, receivers vary in
the numbers of channels they will handle. You can use a receiver with
less or more channels than your transmitter. There are a huge number of
receivers available. I use JR radio and generally use a JR 70 receiver
which is a 7 channel receiver. Other people use different. Batteries There is a vast array of batteries available.
Receivers run on a voltage of 4.8v and 6v. The difference is purely to
do with the torque and speed of the servos. For your first few models you will only need to use
4.8v batteries. These will generally be Nickel Metal Hydrides (NIMH)
and will be AA size. They will be a sealed pack with a lead and plug
pre-fitted. Capacities vary, but for an aircraft with 5 standard servos
ideally you should use a battery of between 1100 and 1800mah. For
aircraft with lots of servos, or high power servos, you should ideally
use a SUB C pack, either 4.8v, or 6v with a capacity of around 3000mah.
The higher the capacity the less quick the battery
will drain. There are a variety of other batteries you can use,
but they should be suitable for model use. I would recommend you fit a battery checker to your
aircraft. These have a row of red, yellow and green led's and
monitor the condition of the battery. When you switch on, one single
green led should stay lit, and when you work the servos, therefore
putting them under load, you should see only green lights and not yellow
or red. If you don’t see green you shouldn't fly.
Aircraft First and foremost, your
first, second and probably third model will not be a Spitfire!!! Your first model will be a basic training aircraft.
Typically it will have banded on wings, tricycle undercarriage and be
high wing. Examples include the Ripmax Trainer, and Irvine Tutor 40. I have taught people to fly on aircraft like these as
well as a very popular aircraft called a WOT 4. This is slightly
different, in that it is a tail dragger, and is therefore slightly more
difficult to handle on the ground. However it is a very capable trainer
and all round general sport aircraft. There are several ways of getting an aircraft:
Plans: You buy
the plans and then separately buy the wood and parts. You need some experience of building and interpreting
drawings.
Semi-Kit: You buy
some wooden and pre-formed parts, plans and drawings and then
prefabricate much of the aircraft yourself.
Kit: You buy a
big box with everything you will need to complete the basic wooden
airframe, including instructions, plans and photos.
ARTF: By far the
most common method, Almost Ready to Fly aircraft have been around for
10years or so. They are mass produced to a high quality and require
minimal assembly of wings, hinges, control surfaces and undercarriage
etc. They are pre-covered, and all you then need to do is
select and fit your radio and engine.
Second Hand:
Often a cheap and easy way to get in the air, used models are often sold
complete. BE VERY CAREFULL,
when buying used aircraft. You don’t
know the aircrafts
HISTORY, ask a
more experienced modeller to assist as they will know the sorts of
things to look for when buying a second hand model.
Electric Models This isn’t my speciality, so it's not a long section
but essentially there are 3 basic components:
Motor
Speed Controller:
this acts as the throttle/motor control and is plugged into the RX. It
is given an AMP rating. So if a motor with a given size prop draws
50amps from the battery, then the controller should be a minimum of 50
amps. A 30 amp controller would probably melt due to the current draw.
Lipo
It is highly recommended that you charge a lipo in
an environment free from combustibles,
ideally on your drive/garden slabs etc. There have been several cases of
lipos exploding, so care and advice should be taken. Servos and receivers are the same as for glow models. How do you know what motor/controller lipo
combination to go for? It's basically about the power of the battery and
the size of the propeller. I much prefer smoke, oil and
noise. If you want more info on electric then again, speak to someone
who knows a bit more about the topic.
General Tips
Covering This is a self adhesive film or fabric which when
ironed shrinks to form a drum tight covering over the aircraft.
Plugs and sockets Make sure that plugs and sockets will not come apart.
There are several ways to do this. Tape, cotton bound or preparatory
fittings that you slide the connected joint into and it locks the
assembly into place. You remove it by unclipping tongues.
Propellers Always ensure you propeller is balanced. Buy a prop
balancer and check the balance of the prop in all directions. Using a scalpel blade, shave the leading edges of the
heavy side until it balances. NEVER add weight to a prop. In extreme
cases you may need to shorten the TIP of the prop in order to balance.
Batteries Always fully charge a new battery (not lipo) for
around 24hrs using the standard wall charger that comes with your radio
set (see later). I fly on a weekly basis and usually charge for about 4
hours. If it hasn't been charged for a while, then I usually charge for
8 hours. Periodically it's worth cycling the battery to keep its
performance. Always use a battery checker and check each flight
that the green lights are showing when the servos are all under load.
Hinges Always use a minimum of 3 hinges per surface, that
way if 1 fails the control surface will continue to operate. There are 5 types of hinge that can be used
Robart:
These
are barbed hinges and circular in shape, they are also glued using
epoxy.
Hairy hinge:
These are thin strips of plastic with a hairy film which when glued with
super glue assist with helping to wick the glue deep into the hinge
Film hinge: This
is less common but is used to hinge the top half of a control surface as
part of the covering on the aircraft.
Mylar Strip: This
is a mylar strip that is cut to size and glued in place. I have had several hairy and mylar hinges break and
no longer use them. Most ARTF models come with these type of hinges. Always pin the hinge from the underside; this adds
extra security should the glue fail. I use small map/dress maker's pins.
Glues When building a model most people use PVA wood glue. For certain high stress applications such as wing
joining, engine bulkhead and tail fitting, 2 pack epoxy glue is used.
This comes in a variety of drying times. 5min, 30min, 1/2hr, 1hr, 2hr,
12hr and 24hr. For all high stress joints I always use 24hr epoxy. Generally a glue is stronger, the longer it takes to
dry. Super Glue or (Cyano) sets quickly and is generally
used for minor repairs, and construction in low stress areas.
What do you need to get started? Firstly you will need to get talking to people and
visit the field. See what others do and how they do it. Then you will need to join the British Model Flying
Association (BMFA). They will then provide you with the relevant third
party insurance, help, information and magazines to get you on your way. I would then advise you to buy some magazines. RCME,
Radio Controlled Model World, Aviation Modeller International. Have a read. Use the internet, visit websites and get
used to terms and phrases. Then you will need to make further important choices. You will
need to choose and aircraft, the Ripmax trainer, You will need to choose a radio. JR, Futaba and Hitec
are very popular, as are Spektrum 2.4 and Multiplex. When you buy a
radio, I would advise you get a complete set. This will include a
transmitter, receiver, battery, charger, servos and switch. You will need to choose an
engine. You will then need a variety of other bits and bobs
for use in the field and at home.
Home: Glues,
spanners, nuts, bolts, clevises, horns, wood, spare covering etc
Field: You will
need a toolbox with basic tools such as spanners, screw drivers, allen
keys etc. Spare and balanced propellers, A starter motor and 12v battery to power the starter. A 2v battery, for providing power to your glow plug. A fuel pump, either electric or hand powered Fuel Most people use flight boxes. These are designed to
hold a 12v battery, power panel (with integral pump, and glow driver)
and a gallon of fuel, plus tools etc. This is by far the best option. Most model shops (both local and nationwide) will
sell everything you need to get going. Most will offer deal packages, which will include
engine, RC, aircraft tools and even fuel. A price of around £300 should
be more than enough to get you in the air. Ask for advice from fellow club mates first.
How long does it take? It will take as long as it takes. Most people will take between 4 and 8 months to learn
to fly solo. But everyone is different. It all depends on the time
you can give to it. The more you fly, the better you'll become. It's exactly like learning to drive. Some weeks good,
some weeks bad, but overall with regular (once, twice a week) practice,
you'll become more proficient. The longer the gaps between flying, the more you'll
forget and the longer it will take.
GOLDEN RULES
Never switch on your transmitter until you have
checked for definite that the channel is free!
Never take your eyes off the plane!
Useful contacts British Model Flying Association Steve Webb Models: For general model items including
servos. Als Hobbies: For general model items Just Engines: for a wide range of engines and
associated items Inwood Models: For general model items DB Sport and Scale: For traditional kit built
aircraft. Nexus Modelling Supplies: For lots of bits and bobs Model Fixings: For nuts, bolts, screws tools etc
Local shops/suppliers Modelpower: Based in Mancetter and useful for
batteries, leads, plugs etc Kits and Bits, Binley Coventry Punctilio
Model Spot, Tonys
Models and Hobbies, Steves Models: Ashby de la Zouch Midland
Helicopters:
I hope I have provided clear advice and have
explained everything. If you have any questions please contact me, or a
fellow club mate. I have not gone beyond the basics and everyone has
their own approach to aero-modelling, but hopefully I've given you a few
points in the right direction. Chris Berry |
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Copyright 2012 Nuneaton Aeromodellers Club
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