Twin edf Airbus A320 - RC

Transcription

Airbus A320
The following articles present the design and construction of a scratch built semi-scale twin edf Airbus A320. Plans are
available in various formats.
Twin edf Airbus A320 rc
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Category: Airbus A320
Introduction
These pages describe the building of a semi-scale model of an Airbus A320 radio-controlled plane.
You should find enough information both in the plans and in the following pages to build this plane if you have enough
motivation. But don't forget: This project is not easy and not for a beginner. There are quite a lot of parts to cut
(RTF lovers this is not for you) and you will need some scratch building experience to build this plane.
Radio installation is not detailled. A modeller who wants to build such a model should be capable to make his/her own
choices about installing and cabling RC equipment in a flying model.
This plane is (was) a great flier. Sadly she crashed only one month after maiden flight due to a radio failure. If you build
one, please send some pictures to continue the story.
Airbus A320
Twin edf Airbus A320 - Download the plans
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Download the plans of the Airbus A320 rc model
If you want to build this beautiful bird, start by downloading the plans and study them carefully.
The plans and drawings to build this electric RC Airbus A320
are available in DXF, DWG and PDF format.
Order a set of printed plans
Airbus A320
Twin edf Airbus A320 - 3D modeling the plane
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Modeling the plane and designing the parts
A few images of the 3d model to explain the design process that made possible to build this plane.
3D model of the Airbus A320
I've designed a 3D model to build virtually the
plane.
The same 3D model will also provide
theconstruction drawings and the CNC files to
cut the different parts.
The airframe is built in two halves, using 3mm
depron foam for the ribs and balsa spars. The
structure is then be sheeted with 1.5mm balsa.
Depron foam offer the following advantages:
It's about 4 times lighter than balsa in the same
thickness.
It's much cheaper than balsa.
But it is quite fragile, doesn't resist great stress
and get easily scratched. Well you cannot get it
all...
Front view of the 3D model
Top view of the 3D model
Some might notice that the wing are not 100%
scale.I've tried to keep scale proportions, but
still, I needed to cheat a bit and make the wings
bigger.
Don't forget that the real A320 cruises at 900
km/h
My first plan was to use 2 Vasafan 65G EDF
as powerplants. Those edf units can take 400 or
480 class brushed or brushless motors and they
have a nice scale look for easy installation on
the plane.
But finally I decided to use 2 Mega 16-15-5
brushless motors with APC 6x4 props instead.
Airbus A320
Twin edf Airbus A320 - The airframe
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Building the fuselage
Since we have to start with
something, why not the
fuselage?
The fuselage is made of two
halves sheeted with 15/10
mm balsa. Once completed
these two halves are glued
together to form the
airframe.
This method is very efficient
and let you build very
impressive airframes. It is also
particularly adapted for
rounded bodies like this A320
we're about to build.
Building the fuselage using
this method is not difficult as
long as you are patient and
careful with your work.
Don't forget that you need to
build two symetrical parts!
Like for the wings ;-)
Airbus A320
Twin edf Airbus A320 - Fuselage continued
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Assembling the two halves of the shell
Now that you spent a few hours building these parts, it's time for the assembly.
First, you have to double and triple check that everything fits correctly. If you
did a good job, there should not be any problem here! Once everything is
adjusted, the parts are glued together to form the fuselage.
Nose gear has to be installed before assembly. A further installation would be
difficult.
The nose of the plane is shaped from a balsa block. I used the same technique
for the tail and the fake APU (see plan).
Bare fuselage weighs 240g (8.46 oz). Which is more than reasonable for a 1m35 (53.15 in) long piece and 15 cm diameter.
Airbus A320
Twin edf Airbus A320 - Vertical fin and rudder
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The vertical fin is a balsa structure sheeted with
10/10 balsa
It has a scale section. This is going to be more work,
but the result is much more accurate than a
deceptive flat section.
All the parts needed are detailed in the plans. you
will have to pay a lot of attention when building this
part if you don't want to end up with a twisted fin.
All the spars are cut from balsa planks (see plan for
thickness)
Use a jigsaw or a milling machine to create the slots
in the spars.
It is best to use a milling machine to create the slots.
Using the right diameter bit, you will mill exactly
the correct width for the slot, but you can also
precisely adjust depth and milling angle.
Once built the vertical fin is sheeted with 10/10 mm
balsa. The rudder is only covered with the material
of your choice (solar, oracover, monokote, silk...)
After you sheeted the structure, plane the spars
down then sand leading and trailing edges to the
right shape.
Airbus A320
Twin edf Airbus A320 - Horizontal stabilizer and elevator
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Horizontal stabilizer and elevator are built like a
small wing on the plan.
The airfoil is NACA 0009 at the stabilizer root and
NACA 0012 at stabilizer tip.
There is nothing really difficult here. All parts
needed are drawn on the plan as the holds needed to
position the ribs.
As for the vertical fin I've cut slots in the spars to
precisely position the ribs. This technique also
strenghtens the whole structure.
The stabilizer is sheeted with 10/10 balsa. the
elevator control surfaces are simply covered as the
rudder.
Airbus A320
Twin edf Airbus A320 - Wings
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The wings
And you thought you were done?
You still have to build a pair of wings and add a few
more hours of work before your bird is ready to take
off.
The wings are built using the traditional method of
balsa ribs and spars.
Once again a CNC milling machine is very helpful
to cut all the parts needed.
Because of the sweep you have to file the slots for
the spars.
the root rib is positioned at 85° because of the
diedral angle( 5°).
As for the root rib, the ones that support the engines
are also positioned with an angle. By doing so, once
the wings are completed and installed on the plane,
the two fans will be vertical.
I've used a traditional design to build the wings. You shouldn't have any difficulty here if you are
familiar with balsa construction.
detail of one aileron.
The main spar is sheeted with 15/10 balsa
Le longeron principal de l'aile est cloisonné avec du
balsa de 15/10. Le fil du bois est vertical.
This wing is almost ready. I still need to add the wing tip shaped from a balsa block and to sheet
the wing with 15/10 balsa on the forepart. I'm sure it's going to be much faster for the second one.
Airbus A320
Twin edf Airbus A320 - assembling the airframe components
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Assembling the components
By now, you should have built a fuselage, the
stabilizer and the vertical fin plus tail control surfaces.
Just glue all that together and the fuselage is done!
I have not sheeted yet the rear part of the fuselage to
properly position tail surfaces.
The last two depron formers have slots to properly
align the stabilizer.
Checking geometry and alignment of the tail surfaces.
Once the tail surfaces are glued we can install
pushrods and control horns for the elevator and
rudder.
Pushrods are made with carbon rods and piano wires
at each end. A ball linkage is used instead of a
standard control horn. This ensures a smooth link with
no gap.
The rudder pushrod is placed inside the fuselage. It is
important to install this part before sheeting the
fuselage as nothing will be accessible from outside the
plane.
Airbus A320
Twin edf Airbus A320 - Central part of the wings
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In order to complete the wings for this bird, we need to
build the central part that will links the two wings
together.
I have also installed most of the radio equipment inside
the central "box".
It is mandatory to use the building beds as they are
drawn on the plans to build the central part of the wing.
I have made some updates and modifications to the
plans after I built this prototype. The pictures shown
here differ a bit from the final version on the plans. but
the building method remains the same.
Wing joiners are installed on the central part. Once this part is finished, we will glue the wing to
the central box.
I've used foam to fill the sides of the box and give it its
final shape.
I suggest to use light balsa blocks. It will be more
resistant and durable.
Sanding the foam blocks to get the right shape
Once the box is built, I've used 1.5mm balsa to sheet it. It's not necessary to sheet the upper part
as shown on the photo above.
Note the foam blocks used to fill the side of the box. As noted before, balsa blocks would be a
better choice.
As the box is very thick,I've made balsa rolled tubes to
guide the screws to the assembly holes.
You may want to improve thi, and find a better solution
to attach the wing to the fuselage...
Trial fit of one wing to the central box.
On the final version of the wing, I didn't sheet the whole wing with balsa. Although I think it
gives a better aspect to the wing, and it doesn't add so much extra weight.
Airbus A320
Twin edf Airbus A320 - Dummy engines & Landing gear
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Dummy engines
Turning a master shape from a balsa block.The
master shape will be used to make a vacuum
formed plastic cowl. I finally didn't use this
solution.
You need to build the fake engines only if you decide to equip your plane with propellers
instead of ducted fans. In flight nobody will notice the 2 props anyway.
If you use ducted fans like the VasaFan 65 G you won't need those parts.
The master is placed on the vacuum table to shape
the cowl.
The custom built vaccum table and the plastic sheet
cooling down on the master shape. I finally didn't
use this solution, but the result wasn't bad at all.
I've applied several coats of nitrocellulosic primer.
Then I've sprayed one coat of Tamiya "Flat
aluminium" and finally the red color
The fake fan is built using plywood rings and spars joining the rings together. The whole
structure is sheeted with 10/10 balsa.
The overall result is quite pleasing.
The Speed 400 motor visible on the picture is used only to check the location of the different
components. I've used 2 Mega 16-15-5 with apc 6x5 props to power this plane.
On the foreground one "engine" is finished and painted using the SAS color scheme
.
Landing gear
I've made the main landing gear with the parts
shown on the left photo. If I build a new version of
this bird, I will definitely install retracts and edf
engines.
We now have built all the parts needed for our plane. Next step is gonna be the assembly, making sure everything is straight.
Airbus A320
Twin edf Airbus A320 - The airframe
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Wing alignement
If you followed me until here, you should have something looking like the bird on the photo below.
Finally it looks like an Airbus
This bird is definitely too big for you, Cat!
We still have to do the covering and paint work...
Airbus A320
Twin edf Airbus A320 - paintwork
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La finition
Almost done!
I've covered the fuselage with "Japan paper" and applied several coats of nitrocellulosic varnish before the paint work.
Same method was used for the wings. Light fiber glass and epoxy resin will give even better results.
If you want to do a decent paintjob, don't hesitate to invest in a decent airbrush! Most "airbrushes" and spray guns sold
in DIY stores don't deserve their name. I finally bought a touch-up gun ANEST IWATA LPH 50 and since then I have
beautiful results.
For detailing a good double action airbrush is also a great tool. The Iwata Revolution series are affordable and perfect
for our use
I decided to paint this model using the SAS color scheme. Which is not very "scale" since SAS doesn't own any A320 at
the moment it their fleet.
If you don't feel comfortable with painitng, you can use thermo film like Solar, Oracover or Monokote It's also easier to
repair in case of damage to the plane.
The doors and windows are stickers printed on a color inkjet printer and applied to the fuselage.
Last step, is motor and radio installation. For this version, I didn't use Vasafan edf as initally planned.
Instead I've installed 2 brushless Mega 16-15-5 turning APC 6x4 props.
Because of the propellers, i had to make the landing gear slightly higher. But the clearance between the
props and the ground is only 15mm (5/8''). Don't expect to take off from grass with this plane.
Page 13 of 16
Airbus A320
Twin edf Airbus A320 - Maiden flight
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6th Décember 2004: Ready for maiden flight
Model data:
Matérial: depron foam and balsa
Finishing: japan paper and paint
Weight: 1.860 kg
Wingspan: 150 cm
Wing airfoil: NACA 4412
Stabilizer airfoil: NACA 0009 to NACA 0012 at tip
Wing area : 25.2 dm2
Wing loading : 73.8 g/dm2
Engines: Mega 16-15-5 avec hélices APC 6 x 4
Batteries: Lithium Polymere IRATE 2600 3S2P
Max consumption : 13 amperes per moteur
RPM max: 16500 t.min-1
Controllers: 2 controleurs Castle Creations Phoenix 35
Receiver: Multiplex IPD 7 voies
Servos: 2 x Waypoint W-150 (elevator and rudder) et 2 x Waypoint W-084 (ailerons)
A few more pics before to take off
You never know what might happen...
Airbus A320
Twin edf Airbus A320 - Maiden flight videos
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First take off. It could have been the last one...
Video of the A320 tail heavy
This is what happens when a plane is too rear balanced (tail heavy).
That was my lucky day! The A320 made an attempt to fly like a 3D plane and hit the ground abruplty on her wheels. The airframe was not damaged.
Only the front wheel was bent. It took a minute to fix it.
Only my pride was a bit scratched ! What a stupid mistake. I had placed the battery pack much too rear on the plane.
This one is the right one!
After we moved the battery pack to the front, we checked the balance of the plane. It looked fine. Last check and take off.
This time it worked fine and the A320 made a fantastic maiden flight.
Airbus A320
Twin edf Airbus A320 - Sad day
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Sad day for the A320
Sunday 9th January 2005
Following a complete radio failure, the plane went out of control and crashed in the trees nearby our flying field. It's
really sad, this plane was a great flier. The right wing is damaged beyond repair.The airframe shows a few cracks but
would be repairable. Consiering the violence of the crash, I can say that it is a robust design.
The plane would need major repair to fly again. After one year of work I lack motivation to fix it or rebuild a new one...
What probably happened
A few seconds after the take off, the plane made a first tip stall. I recovered easily and thought of some radio glitch. I
took the wrong decision and decided to continue flying.
But a few seconds later the plane did not react at all to the radio and continued to fly on its own, flying perfeclty straight
and smooth but becoming smaller and smaller in the sky. After 30 seconds of free flight, the radio decided to work
again, and I was able to manage a large turn and bring the model back above the flying field. When I started the
descent for the approach, again the radio stopped functioning. This time the plane was banking in the turn and there
was no possible recovery. She crashed in the hill facing our flying field.
Final word
To save weight, I didn't use a separate receiver battery. the radio was fed using the BEC on one of the two ESC. The
voltage regulator of the BEC was probably unable to cope with current draw from the 4 servos, especially during takeoff or landing approach. That's why the radio was cut at those critical moments.
I also noted later, that on a twin engine model, it is much safer to have one battery for each motor. I've noticed The
Castle Creations ESC don't like to be plugged in parallel
My recommendations for a model like this are:
One separate battery for the radio. 40 grams for a 1000 MAH NIMH battery pack wont change anything to the
performance of your plane
Keep the two motors independent. It means one ESC per motor and one battery pack per motor. It's better to install two
2 amps packs than one single 4 amps pack and connect everything to that single pack.
Despite the crash, the project was very succesful. This A320 model is a great flier, and i can only encourage you to
build yours.

Twin edf Airbus A320 - RC

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