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Composite-ARF Extra 260 (2.6m span)
Instruction Manual
Composite-ARF Extra 260, 2.6 m
TAVS Technology
Version 1.0
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Instructions for Extra 260 IMAC-Airplane
Thank you very much for purchasing our Composite-ARF Extra 260 all composite aircraft, made
with the revolutionary Total Area Vacuum Sandwich (TAVS) technology. It is based on our 3m
version of the Extra 260, but reduced in size to suit the most popular 75 - 120cc engine sizes.
A few of the photos in this instructions that explain ‘standard’ techniques and methods are actually of parts from different planes, and this will be obvious from the paint colors/schemes - so
please don’t get confused !
Before you get started building and setting-up your aircraft, please make sure you have read
this instruction manual several times, and understood it. If you have any questions, please
don’t hesitate to contact us. Below are the contact details:
Email: [email protected]
or [email protected]
Telephone: Phone your C-ARF Rep!!! He will be there for you.
Website: http://www.composite-arf.com
Liability Exclusion and Damages
You have acquired a kit, which can be assembled into a fully working R/C model when fitted out
with suitable accessories, as described in the instruction manual with the kit.
However, as manufacturers, we at Composite-ARF are not in a position to influence the way you
build and operate your model, and we have no control over the methods you use to install,
operate and maintain the radio control system components. For this reason we are obliged to
deny all liability for loss, damage or costs which are incurred due to the incompetent or incorrect
application and operation of our products, or which are connected with such operation in any
way. Unless otherwise prescribed by binding law, the obligation of the Composite-ARF company to pay compensation is excluded, regardless of the legal argument employed.
This applies to personal injury, death, damage to buildings, loss of turnover and business,
interruption of business or other direct and indirect consequent damages. In all circumstances
our total liability is limited to the amount which you actually paid for this model.
BY OPERATING THIS MODEL YOU ASSUME FULL RESPONSIBILITY FOR YOUR ACTIONS.
It is important to understand that Composite-ARF Co., Ltd, is unable to monitor whether you
follow the instructions contained in this instruction manual regarding the construction, operation
and maintenance of the aircraft, nor whether you install and use the radio control system
correctly. For this reason we at Composite-ARF are unable to guarantee or provide a
contractual agreement with any individual or company that the model you have made will
function correctly and safely. You, as operator of the model, must rely upon your own expertise
and judgement in acquiring and operating this model.
Supplementary Safety Notes
Pre-flight checking:
Before every flying session check that all the model’s working systems function correctly, and be
sure to carry out a range check.
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The first time you fly any new model aircraft we strongly recommend that you enlist the help of
an experienced modeller to help you check the model and offer advice while you are flying. He
should be capable of detecting potential weak points and errors.
Be certain to keep to the recommended CG position and control surface travels. If adjustments
are required, carry them out before operating the model.
Be aware of any instructions and warnings of other manufacturers, whose product(s) you use to
fly this particular aircraft, especially engines and radio equipment.
Please don’t ignore our warnings, or those provided by other manufacturers. They refer to things
and processes which, if ignored, could result in permanent damage or fatal injury.
Attention !
This IMAC-Aircraft is a high-end product and can create an enormous risk for both pilot and
spectators, if not handled with care, and used according to the instructions. Make sure that you
operate your Extra according to the AMA rules, or those laws and regulations governing the
model flying in the country of use.
The engine, servos and control surfaces have to be attached properly. Please use only the
recommended engines, servos, propellers, and accessories supplied in the kit.
Make sure that the ‘Centre of Gravity’ is located in the recommended place. Use the nose
heavy end of the CG range for your first flights,
before you start moving the CG back to a more
critical position for 3D-maneouvers. If you find
that you need to relocate your batteries or even
add weight in the aircraft to move the CG to the
recommended position, please do so and don’t
try to save weight or hassle. A tail heavy plane,
in a first flight, can be an enormous danger for
you and all spectators. Fix any weights, and
heavy items like batteries, very securely to the
plane.
Make sure that the plane is secured properly when you start the engine. Have at least 2 helpers
hold your plane from the tail end, or from behind the wing tips, before you start the engine. Make
sure that all spectators are behind, or far in front, of the aircraft when running up the engine.
Make sure that you range check your R/C system thoroughly before the first flight. It is absolutely necessary to range check your complete R/C installation first WITHOUT the engine running.
Leave the transmitter antenna retracted, and check the distance you can walk before ‘fail-safe’
occurs. Then start up the engine, run it at about half throttle and repeat this range check with the
engine running. Make sure that there is no range reduction before ‘fail-safe’ occurs. Only then
make the 1st flight. If you feel that the range with engine running is less then with the engine off,
please contact the radio supplier and the engine manufacturer and DON’T FLY at that time.
Check for vibrations through the whole throttle range. The engine should run smoothly with no
unusual vibration. If you think that there are any excessive vibrations at any engine rpm’s, DON’T
FLY at this time and check your engine, spinner and propeller for proper balancing. The light-
Composite-ARF Extra 260 (2.6m span)
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NO !!!
Secure the plane
before starting the engine.
DANGER ZONES
NO
NO
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Composite-ARF Extra 260 (2.6m span)
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weight sandwich composite parts don’t like too much vibration and they can suffer damage. The
low mass of all the parts results in a low physical inertia, so that any excess vibrations can affect
the servos and linkages.
Make sure that your main and stab tubes are not damaged. Check that the front and rear antirotation pins for the wings and horizontal stabiliser are located correctly in their holes, and are
not loose. Check that the 4 plastic wing retaining nuts are tight, that the M3 bolts retaining the
horizontal stablisers on to the aluminium tube are installed and tight, and that the hinge wires for
the rudder and elevators cannot come out.
If you carefully checked all the points above and followed our advice exactly, you will have a safe
and successful first flight - and many hours of pleasure with your Composite-ARF Extra 260.
General information about
fully-composite aircraft structure and design
All the parts are produced in negative molds, manufactured using vacuum-bagged sandwich
construction technology. All parts are painted in the moulds, either single colour or designer
colour schemes. A new production method, called TAVS (Total Area Vacuum Sandwich), enables
us to present this aircraft with incredible built-in strength, while still being lightweight, and for a
price that nobody could even consider some years ago. This production process has huge
advantages, but a few disadvantages as well. These facts need to be explained in advance for
your better understanding.
Description of Parts
The Wings:
Both wing halves are made in negative moulds, fully vacuum-bagged, using only 2 layers of cloth
in combination with a hard 2mm foam sandwich to form a hard and durable outer skin. Because
of this TAVS technology no additional structural parts are needed except for the main spar tube.
The ailerons are already hinged for you. They are laminated in the wing mould and are attached
to the main wing with a special nylon hinge-cloth, sandwiched between the outer skin and the
foam. This nylon hinge is 100% safe and durable. You never have to worry about breaking it, or
wearing it out. There is no gap at all on the top wing surface, and there is a very narrow slot in
the bottom surface, where the aileron slides under the main wing skin during down throw. This
hinge setup is the cleanest you can ever obtain, but you have to take some care during assembly for proper installation and servo set up.
First, the hinge line is on the top surface of the wing, not in the centre. This is NOT a disadvantage, if you set in about 10% NEGATIVE aileron differential in your transmitter program. This
means that the ‘down’ throw needs to be about 10% more than the up throw.
Why? Because the axis of the hinge is not at the centreline of the aileron, so it moves slightly
in and out when it travels, and the aileron gets a little "bigger" in surface area when moving up,
and "smaller" when moving down. This is why you have to set the negative differential in your
transmitter to compensate for the size changing. 10% is a good starting point, and you will find
out the exact setting during the first flights, doing fast vertical rolls and watching the fuselage
rolling in a perfect line. You can set it perfectly, this is guaranteed.
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The bottom slot needs some explanation, too. The cut line
is exactly in the correct position so that the aileron slides
under the wing skin smoothly. If the cut was a few mm forward or back, it would not work properly. So, make sure that
the lip is not damaged, and that the aileron slides under this
lip perfectly. It will NOT lock at any time, as long as the lip
is not damaged. If damage occurs to the lip, you can cut off
2-3 mm, but you should NEVER need to cut off more than
this.
Make sure that the control horns are glued into the ailerons properly. The hole in the phenolic
horn for the quick-link needs to be exactly perpendicular to the hinge axis line, and in this manual we show you a simple way to ensure that the horns in all pairs of control surfaces will be identical, making it easy to set up your R/C for accurate flying manoeuvres.
The wings are already set-up with servo covers and hatches for 2 servos per aileron, and we recommend a pair of high-torque servos, for example the JR DS8411, in each wing. Our servo covers and milled plywood mounts make installation, and exchange if necessary, very quick and
easy and provide a rock solid servo mounting and linkage system.
The wings are attached to the fuselage with the 4 threaded
aluminium dowel anti-rotation pins, with 4 plastic nuts
inside the fuselage. If the aluminium dowels come loose in
the wing, the wing will slide outwards, away from the fuselage, and the main spar tube will definitely break. So take
great care to inspect the glue joints of these anti-rotation
dowels in the wing REGULARLY. Excessive vibrations or
hard shocks can cause the glue joints to weaken or break.
Monitor these joints whenever you set up your plane. Never
forget to tighten the nuts inside the fuselage. Please DO
NOT modify these attachment dowels in any way, their perfect function is proven for many years.
The Fuselage:
The fuselage is also made in negative moulds, and is all
constructed using TAVS technology. All the loadbearing
internal parts are installed during manufacture, to ensure
accurate location and reduce your assembly time. The
fibreglass tubes in the wings to receive the wing spar tube,
the stab spar tubes, and the holes and reinforcement plates
for the anti-rotation dowels, are already installed. There is
no need to even check the incidences - you can be assured
that these are already set in the moulds so that no adjustment is necessary.
The landing gear mount is strong and doesn’t need any extra reinforcement. The fuselage is
extremely light weight, and the gear loads need to be led into the structure gently. No glue joint
needs to be stronger than the materials that it is attached to, as it would just result in increased
weight for no advantage. The landing gear is a fairly flexible design, which works very much like
shock absorbers. This plane is not made for crashing, but the landing gear will take some hard
landings without problems. Do not change or modify it, as the results would only be negative. We
had plenty of time and experience to engineer the strength needed in this area - and we did !
The motordome and firewall are a fully integral parts of the fuselage, and provide plenty of
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Centreline of hinge axis
Phenolic control horn
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strength for any engines up to 120cc on the market today.
See the Engine Installation section for details of engine and
setting thrust angles.
The engine cowling should be attached using the method
shown. It is only a little work and this mounting has been
tested and proven for many years.
The Stabilisers:
The stab parts are also vacuum bagged sandwiched. The
rudder and the elevator control surfaces are hinged with
4mmØ tubes, fitted through phenolic hinge bearing plates
which are jig-installed during manufacture for perfect alignment.
The rudder and elevator design allows for at least 50
degrees throw. For the Extra it is mandatory that the tail
area is extraordinarily light weight, so the stab is designed
for one powerful servo installed in each half. All the structural parts are preinstalled. The horizontal stabs are mounted with one 20mm aluminum tube and one 10mm carbon
anti-rotation pin each.
Servo Screws:
Fix the all the servos into the milled plywood servo mounts
using the 2.9 Ø x13mm sheet metal screws provided in the
kit, not the standard screws normally supplied with servos
by the servo manufacturer. This is because all the holes in
our milled servo mounts are 2mm diameter, due to our CNC
manufacturing process, and this is too big for the normal
screws.
Take Care:
Composite sandwich parts are extremely strong, but fragile
at the same time. Always keep in mind that these contest
airplanes are designed for minimum weight and maximum
strength in flight. Please take care of it, especially when it
is being transported, to make sure that none of the critical
parts and linkages are damaged. Always handle your airplane with great care, especially on the ground and during
transport, so you will have many hours of pleasure with it.
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(above) The lightweight fin-post
has the phenolic rudder hinge
posts already installed and aligned
at the factory. The corresponding
tubes are also installed in the rudder for the hinge tube.
(below) The elevator and rudder
hinging uses 4mm diameter aluminum tubes, inside phenolic
hinge posts that are factoryinstalled and aligned.
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Accessories
Below are the things you may need to get your Composite-ARF Extra 260 (2.6m) in the air. Some
of them are mandatory, some of them can be chosen by you. What we list here are highly recommended parts, and have been thoroughly tested.
1. Power servos (min. 8 required). We highly recommend JR 8411 or 8511/8611 for all con
trol surfaces. For Futaba users, we recommend 2 x S9351’s for each Aileron, 1 x S9351
for each elevator, and 2 x S3951’s for rudder.
2. Aluminium servo output discs, or full metal arms (8 pieces). We strongly recommend that
you attach the phenolic servo extension arms provided in the kit to metal servo output
discs, or use full metal servo arms (eg: SWB ‘Double-Loc’ type). The rudder phenolic servo
horns must be attached to metal servo output discs (eg:‘Hangar 9’ #HAN3526 or 3520).
3. Throttle servo. Any standard servo will do (eg: JR/Graupner 4041/5391)
4. Aluminum Spinner 115 - 125 mm/4.5 - 5” dia. eg: Tru-Turn. (Ø120mm carbon spinner
& CNC T6 alu. backplate available from C-ARF as an option, #810100 - 810105+)
5. Main wheels 115 - 125 mm (4.5 - 5"). Kavan Light or Dubro wheels are recommended.
6. Engine 75 - 100cc. The DA-100 is probably the most commonly used engine for our 2.6m
span Extras, and the mounting dimensions are shown for this motor. However in these
instructions we also show the installation of a lightweight option with a 3W 80cc single
cylinder and tuned pipe set-up.
7. Muffler/Canister or Tuned pipe(s) and headers. (Headers, canisters, tuned pipes and
Teflon joiners are available from C-ARF as options. See our webpage for availability)
8. Tailwheel assembly. (Available as an option from C-ARF. Product # 801000.)
9. High quality heavy-duty servo extension cables, with gold connectors. High quality
receiver and ignition switches, etc.
10. Receiver and Ignition batteries.
11. Powerbox and dual powerswitches for dual batteries (available from C-ARF as an option)
12. Fuel tank (750 - 900 ml) with gasoline stopper. We used a Dubro #690 in this plane.
13. Cable ties in various lengths.
14. Propeller. Carbon Meijzlik or Menz 28 x10 for DA-100. 26 x 12 or 27 x 10 for 3W 80cc.
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Tools
This is a very quick and easy plane to build, not requiring difficult techniques or special equipment, but even the building of Composite-ARF aircraft requires some suitable tools! You will
probably have all these tools in your workshop anyway, but if not, they should be available in all
good hobby shops, or hardware stores like "Home Depot" or similar.
1. Sharp knife (X-Acto or similar)
2. Allen key set (metric) 2.5mm, 3mm, 4mm & 5mm.
3. Sharp scissors
4. Pliers (various types)
5. Wrenches (metric)
6. Slotted and Phillips screwdrivers (various sizes)
7. M3 tapping tool (metric)
8. Drills of various sizes
9. Small spirit level, or incidence meter.
10. Dremel tool (or Proxxon, or similar) with cutting discs, sanding tools and mills.
11. Sandpaper (various grits), or Permagrit sanding tools (high quality).
12. Carpet, bubble wrap or soft cloth to cover your work bench (most important !)
13. Car wax polish (clear)
14. Paper masking tape
15. Denaturised alcohol, or similar (for cleaning joints before gluing)
Adhesives and Solvents
Not all types of glues are suited to working with composite parts. Here is a selection of what we
normally use, and what we can truly recommend. Please don’t use inferior quality glues - you will
end up with an inferior quality plane, that is not so strong or safe.
High performance models require good gluing techniques. We highly recommend that you use
either a slow (minimum 30 minute cure) epoxy resin and milled fibre mixture, or a slow filled
thixotropic epoxy for gluing highly stressed joints (eg: Hysol 9462). The self-mixing nozzles make
it easy to apply exactly the required amount, in exactly the right place, and it will not run or flow
onto places where you don’t want it! It takes about 1 - 2 hours to start to harden so it also gives
plenty of time for accurate assembly. Finally it gives a superb bond on all fibreglass and wood
surfaces. Of course there are many similar glues available, and you can use your favourite type.
1. CA glue ‘Thin’ and ‘Thick’ types. We recommend ZAP, as this is very high quality.
2. ZAP-O or Plasti-ZAP, odourless, or ZAP canopy glue 560 (for clear canopy)
3. 30 minute epoxy (stressed joints must be glued with at least 30 min & NOT 5 min epoxy).
4. Loctite Hysol 9462 or equivalent (optional, but highly recommended)
5. Epoxy laminating resin (12 - 24 hr cure) with hardener.
6. Milled glass fibre, for adding to slow epoxy for stronger joints.
7. Micro-balloons, for adding to slow epoxy for lightweight filling.
8. Thread-locking compound (Loctite 243, ZAP Z-42, or equivalent)
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We take great care during production and Quality Control at the factory to ensure that all joints
are properly glued, but of course it is wise to check these yourself and re-glue any that might just
have been missed.
When sanding areas on the inside of the composite sandwich parts to prepare the surface for gluing something onto
it, do NOT sand through the layer of lightweight glasscloth
on the inside foam sandwich. It is only necessary to rough
up the surface, with 80/120 grit, and wipe off any dust with
acetone or de-natured alcohol (or similar) before gluing to
make a perfect joint. Of course, you should always prepare
both parts to be joined before gluing for the highest quality
joints. Don’t use Acetone for cleaning external, painted,
surfaces as you will damage the paint.
Tip: For cleaning small (uncured) glue spots or marks off the
painted surfaces you can use old-fashioned liquid cigarettelighter fuel, like ‘Ronsonol’ or equivalent. This does not damage the paint, as Acetone and many other solvents will, and
this is what we use at the factory.
At Composite-ARF we try our best to offer you a high quality kit, with outstanding value-formoney, and as complete as possible. However, if you feel that some additional or different hardware should be included, please feel free to let us know.
Email us: [email protected].
We know that even good things can be made better !
Did you read the hints and warnings above and the instructions carefully?
Did you understand everything in this manual completely?
Then, and only then, let’s start assembling your Composite-ARF Extra 260
Composite-ARF Extra 260 (2.6m span)
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TIP: Lighter fluid is excellent for
cleaning small marks, clear wax,
uncured glue, or similar off the
painted surface of the plane without damaging the paint.
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Building Instructions
General Tips:
We recommend that you follow the order of construction shown in this manual for the fuselage,
as it makes access to everything easier and saves time in the end. The wings and stabs can be
done at almost any point, and only need servos and control horns installing anyway.
The first thing to do is protect the finished paint on the outside of the model from scratches and
dents during building - so cover your work table with a piece of soft carpet, cloth or bubble-plastic. The best way to stop small spots of glue getting stuck to the outside of the fuselage is to give
the whole model 2 good coats of clear car wax first, but of course you must be sure to remove
this 100% completely before adding any decals or markings. Additionally you can cover the
majority of the fuselage with the bubble-plastic used to pack your model for shipping, fixed with
paper masking tape, which also protects it very well.
When sanding any areas of the inside of the fuselage to prepare the surface for gluing something onto it, do NOT sand right through the layer of glasscloth on the inside foam sandwich !
It is only necessary to rough up the surface, with 60/80 grit or equivalent, and wipe off any dust
with alcohol (or similar) before gluing to make a perfect joint.
Before starting construction it is a good idea to check inside the fuselage for any loose glass
fibres that could cut your hands, and a quick scuff over any of these with a coarse Scotchbrite
pad will remove them.
Note: It is very important to prepare the inside of the fuselage properly, by roughing up and
cleaning the surface, before gluing any parts to it.
Landing Gear
The 1st job is to fit the landing gear legs, and you can leave
these in place, as they will protect the bottom of the fuselage during assembly and gear installation.
The Composite-ARF landing gear for the Extras consists of
45 deg laminated carbon fibre and fibreglass cloth and a
huge number of rovings inside, all made under vacuum and
heat-cured. However it is still light weight, and retains
enough flexibility to take the shock out of any landings that
are less-than-perfect!
The 4 undercarriage fixing bolts are installed from the outside, bottom, of the fuselage, as shown in photo P1.
Mark the position of the holes on each carbon
leg, and drill the holes with a sharp 6.5mm Ø
drill. The centres of the holes are measured
from the centre of the bend in the leg that will
be positioned about 8mm outside the fuselage
surface (photo P1). The outer holes are 33mm
from the bend, and the inner holes are 81mm
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(above) The main parts used to
assemble the Landing Gear.
(below) Drill 2 x 6.5mm Ø holes for
bolting in the Landing Gear.
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Composite-ARF Extra 260 (2.6m span)
inside them. The centre of the holes should be 18mm from
the front edge of the carbon (photo above).
The legs are fixed to the plane with the M6 x 20 bolts and
13mm Ø washers into the blind nuts that are installed in the
plywood supports during manufacture (photo P2). Both
main legs are identical, until you have drilled the mounting
holes, and can be used either side.
The method of fixing the wheelpants and axles to the landing gear legs is slightly different to the method we have
described in the past, but it is even easier and works better. The wheelpants have a moulded-in recess for the end
of the landing gear legs, which also sets the correct angle
relative to the ground. Drill an 8mm Ø hole through the
moulded-in ‘dimple’ for the axle, and another 8mm hole
directly opposite, on the outside surface of the wheelpant
for inserting the axle bolt. You can spin the head of the axle
bolt against a sander to reduce the diameter a little if you
wish (see photo right).
Prepare the inner surface of the wheelpants by sanding the
kevlar patch. Take the 2 milled plywood ‘U’ shaped pieces
and enlarge the 6mm Ø holes to 8mm diameter. Press the
M6 T-nuts into the holes, just far enough so that the end of
the T-nut projects through the hole a maximum of 1mm.
The ‘spikes’ will still engage in the plywood, and the gap
between the T’ nut and the plywood is filled with epoxy and
microballoons mixture. (see photo P3)
Glue the 2 ‘U’ shaped milled plywood pieces to the inside
surface of the wheelpants with 30 minute epoxy and
microballoons mixture, over the kevlar reinforcement, in
line with the moulded recess, and so that the hole in the
plywood is exactly in line with the 8mm hole you have
drilled in the wheelpant. Temporarily use the LG mounting
bolts to secure the plywood to the wheelpant while the glue
dries. At the same time secure the T-nut to the plywood with
some of the thick epoxy/micro mixture, as shown.
Drill 6mm Ø through the centre of the moulded dimples in
the bottom of the carbon legs, and bolt to the wheelpants
temporarily with the axle bolt. You might need to sand the
ends of the carbon LG legs a little so that they fit into the
molded recesses in the wheelpants perfectly.
Bolt the LG legs to the wheelpants, and drill a 3mm hole
thru’ the carbon leg and wheelpant, about 25mm above the
axle. Fit an M3 bolt and washer, and use an M3 T-nut inside - also secured to the plywood ‘U’
shape with epoxy/micro mixture. This bolt sets the precise angle of the wheelpant to the carbon
landing gear leg. Do not use a bolt of larger diameter, as a larger hole required could weaken
the leg.
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(above) Glue the milled plywood
reinforcements to the inside of the
wheelpant as shown, using a 30
minute epoxy and microbaloons
mixture.
(above) The moulded dimple in
the bottom of the carbon legs. Drill
a central hole of 6mm diameter.
(below) shows the M3 bolt thru’
the carbon leg, into the T-nut
glued inside the wheelpant.
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Install your chosen wheels (Ø5” Dubro 500TL
shown), inserting the M6 x 70mm steel axle
bolt through the hole you drilled in the outside
surface of the wheelpant. Depending on the
thickness of your chosen wheel, you will need
2 or 3 of the M6 washers either side of the
wheel to centre it - and also an M6 wheel collar (supplied) on the inner side as well,
between the washers and the ‘T’ nut.
Tighten the axle bolt securely into the T-nut,
and then secure the assembled wheelpant to
the carbon leg using an M6 washer and M6 locknut as
shown right. A drop of loctite on the M6 lock-nut is good
insurance. Finally insert the M3 bolt thru’ the carbon leg into
the T-nut.
You can use any 4.5” - 5" main wheels. Kavan wheels are
very lightweight, but not very durable on asphalt runways,
and Dubro wheels are a little heavier but much more solid.
Tailwheel
The tail wheel setup shown in these photos is an optional
part available from C-ARF (# 801000), and is mounted with
2 sheet metal screws and 2 plastic ‘U’ brackets under the
fuselage, screwed into the plywood reinforcement that’s
installed in the fuselage at the factory. Drill a 4.8mm diameter hole, 55mm in front of the finpost and insert the tailwheel wire (photo right).
You don’t need to make the tailwheel steerable if flying from grass surfaces, a simple
castoring action is fine. However, for hard runways you may prefer to connect it either to the
rudder horn with 2 small springs, or even better to the rudder pull-pull cables about 130mm
in front of the rudder leading edge - as shown
here. It’s easy to make the springs, if necessary, by winding some 0.5 - 0.8mm Ø piano
wire around a 5mm drill bit, turned slowly in a
battery-drill, with a small hook in each end to
connect to the tailwheel steering arms. (see
also photo P4)
Remember - keep it lightweight at the tail end!
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(below) Tailwheel assembly
installed. It can be connected to
rudder horn OR rudder cables with
springs for improved steering.
(above) Completed wheel pant.
(below) Position of Ø 4.8mm hole
for C-ARF optional tailwheel.
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Cowling
The 1 piece cowling is already cut and trimmed at the factory, and should need very little adjustment for a perfect fit.
With the main undercarriage legs bolted into place, install
the wing tube in the fuselage sleeve and place a small spirit or incidence meter level on top of it to set the plane exactly level (side to side). Pack under one undercarriage leg as
necessary to get it level on your building table.
If necessary, sand the fibreglass joining tapes inside the
back edge of the cowl slightly to get a perfectly flush fit
between the cowling and the fuselage sides. Trial fit the
cowling, and use a straight-edge on the lower (flat) part of
the cutout at the front of the cowl to make sure that it is parallel with the wing tube, or stab, and properly centred. Tape
the cowl firmly into position, and mark a centreline on the
top of the cowl and the fuselage, on masking tape.
The cowling is held in place with 9 bolts (M3 x 12mm),
washers and blind nuts. Drill one 3mm diameter hole at the
top/centreline of the cowl, approx. 8mm (5/16”) in front of
the back edge of the cowling, and insert an M3 x 12mm
bolt. Thread a T-nut onto the bolt inside the fuselage, and
secure it to the fuselage with one small drop of thick CA.
Note that the blind nuts are fitted reversed, with the spikes
pointing inwards! Check alignment again, and then drill and
fit the other 8 bolts in the same way, securing the blind nuts
to the inside of the fuselage with a single drop of thick CA.
Space the 9 bolts 110mm (4.5”) apart, so that the lowest 2
bolts will be about 25mm from the edges of the square
cutout in the bottom of the cowling, to retain it properly.
Don’t forget to wax, or oil, the M3 bolts first, to make sure
that you don’t accidentally glue any of the bolts to the cowling or into the blind nuts! Finally glue the 9 blind nuts in
place properly using a medium-thick mixture of 30 minute
epoxy and micro-balloons, as shown. During final assembly, add the supplied M3 washers under the heads of all the
M3 bolts.
Composite-ARF Extra 260 (2.6m span)
13
(above) Check cowl opening is
parallel to stab or wing tube, and
tape in position.
(below) Secure with 9 equallyspaced M3 x 12 bolts, into T-nuts
glued inside the fuselage.
(above & below) Tack glue the Tnuts in position with a small drop
of thick CA first. When cowling is
correct, secure all the T-nuts with
a drop of, fairly wet, epoxy and
microballoons mixture as shown.
M3 T-nut
M3 bolt
cowl/fuselage
Epoxy
& micro
mixture.
Page 14
Composite-ARF Extra 260 (2.6m span)
Canopy Frame
The fibreglass canopy frame mountings are already completed for you at the factory. It is secured to the fuselage
with four M4 x 10mm allen bolts, fitted from the outside of
the fuselage, through the plywood tabs that are glued to the
canopy frame, into M4 T-nuts. This system has been very
well proven on all of our aerobatic planes, and is a strong
and rigid solution.
Fitting the clear canopy into the frame can be a little bit
tricky, and this is a step by step guide of how we do it. Of
course you can use own your favourite glue and method if
you prefer.
Sand the inside edges of the canopy frame carefully with
120 grit sandpaper, especially the fibreglass joining tapes,
to ensure a perfect fit of the canopy. Fit the canopy frame
on the fuselage and secure with all 4 bolts. Lay the canopy
on top of the frame, view from the front to check that it is
centred and symettrically positioned, and then mark the
approx. shape with a felt pen or wax crayon. There is an
approx. ‘cut-line’ molded into in the edges of the canopy to
assist you, and you should start by trimming 4 - 6mm outside this line. Unless you are in a very warm room, we recommend that the canopy is slightly warmed up with a hair
dryer to prevent cracking - but be careful not to melt or
deform it! When the canopy fits inside the frame, tape it
into position temporarily, and accurately mark the edge of
the frame on the canopy with a wax crayon. Remove the
canopy and trim exactly to shape, leaving about 6mm overlap outside the line all around.
Refit the canopy into the frame, and tape into position from
the inside. Push the canopy up tightly inside the back of the
frame and fix the bottom 2 back corners with
one small drop of odorless CA each (ZAP-O
recommended).
Note: Do NOT use any CA accelerator/kicker
- you will immediately ‘fog’ the clear canopy!
Make visual check from the front and back to
make sure sure that the canopy is straight.
Make several hand-holds with strong tape to
make holding and positioning the canopy
easy. Remount the frame to the fuselage (use
all 4 bolts), and tape the canopy frame tightly
to the fuselage all around.
Tip: The sides of the fuselage and canopy frame are almost straight and so, if you wish, you can
temporarily stiffen the edges of the canopy frame (while gluing the canopy in) by tacking some
14
(above) Mark centrelines on the
clear canopy at front and back and
visually check that it is straight.
(below) Duct-tape handles used to
pull clear canopy against the
canopy frame while gluing it in
position with a few small drops of
odorless-CA. Remove canopy and
secure the edges of the clear
canopy with a bead of epoxy to
trap it in place (see above)
(above) The canopy frame is
secured to the fuselage with 4
tabs, M4 bolts and T-nuts, all finished at the factory for you. Also
note the bead of epoxy to secure
the canopy to the inside of the
fibreglass frame.
Page 15
Composite-ARF Extra 260 (2.6m span)
strips of 10mm balsa to masking tape on the fuselage sides. This makes it easier to pull the clear
canopy against the frame, using the tape ‘handles’ while tacking it in to place - without deforming the canopy frame.
Using the tape handles to pull the canopy outwards firmly against the frame, working from the
back towards the front, glue the edges of the canopy in place in 2 more places each side, with
just a single small drop of CA at each position, all the time checking that the edge of the canopy
is tight up against the frame at the front.
Now that the canopy is fixed in position and cannot twist or warp anymore, you can carefully
remove the canopy frame from the fuselage, and use a 30 minute or 24hr epoxy and micro-balloon mixture for gluing all the edges to the frame on the inside surface (see photo above). It is
most important that the canopy cannot come off in flight, so make sure that the bead of glue traps
the clear canopy firmly in place. Re-secure the canopy frame onto the fuselage with all 4 bolts
while the epoxy-microballoons mixture is curing to prevent any warps or twists.
If you want a completely rattle-free canopy, you can fill the slight gaps at the front and back of
the frame with a bead of clear silicone. Apply shiny brown plastic tape to the front and back
edges of the opening in the fuselage and wax twice with clear car wax. Sand lightly, and degrease edges of canopy frame where the silicone will be applied. Apply a small bead of clear silicone to the front end of the frame only, and secure the frame into position wthl all 4 bolts until
cured. Remove frame, and trim off excess silicone with a very sharp knife. Then repeat for the
back edge. Do not try to do the back and front at the same time - or you will find it very difficult
to get the canopy frame off the fuselage! See photo P5.
If you wish you can tint the inside of the canopy using one of the aerosol spray paints used for
painting the inside of polycarbonate car bodies (eg: the Tamiya or Lexanit ranges). Degrease and
clean the the surface very carefully, removing all finger-prints, and use many very light ‘mist’
coats to get even coverage.
Horizontal Stabs
The stabilisers are 95% finished at the factory, and only need the servos, horns and linkages
installing. Insert the Ø20 x 330mm long aluminium tube spar in the fuselage sleeve, and slide on
both stabs to check the fit between the root ribs and
the fuselage. You can sand the root of the stabs
slightly to make a perfect joint if needed, and if the
spar tube is a fraction long you must shorten it.
The elevators are hinged to each stab using the Ø
4mm aluminium tubes provided. Make sure there is
no burr on either end of the tubes, and chamfer one
end slightly with fine sandpaper to make it easier to
get them through the holes in the phenolic hinge
plates. Be careful inserting them, and if they are a bit
stiff, then use a little grease on the tubes. Don’t use
too much force, otherwise a phenolic hinge post
inside might break loose. Leave the tubes a bit too
long during assembly, and cut them to exact length
when the model is finished.
15
(above) Bell/splay one end of each tube,
countersink the hole in the root end of
the elevator, & use clear tape to fix the
tube in position during final assembly.
Page 16
During final assembly, you can retain both ends of the
tubes with small pieces of clear tape on the root and tip
ends of the elevators. An alternative method is the ‘bell’ one
end of each aluminium tube, and countersink the hole in the
root end of the stab. Then you only need to tape the inner
end of the hinge tube (photo above).
Servos
You have a choice of elevator servos; either a hi-power digital JR8511/8611 in each stab, or an JR8411, which is also
sufficient. Although the JR8511/8611 servos are about 1
mm longer and wider than the 8411, both sizes will fit in the
milled servo cutouts in the ribs. If using Futaba servos, we
recommend that you use S9351’s, which also fit the milled
servo cutouts. Please do not use inferior quality servos, or
servo arms, in this plane. It will result in an aircraft that does
not fly accurately, reliably or safely.
The servos are installed with the output shafts towards the
stab trailing edge, and they must be installed using the
2.9mm Ø x 13mm sheetmetal screws provided in the kit,
not the standard screws provided with the servos which are
too small for the Ø 2mm milled holes.
Servo arms
To obtain sufficient elevator throws, quite long servo output
arms are needed (30 - 35mm/1.25 -1.5”). In the kit we supply phenolic servo arm extensions for this purpose, which
can be fitted onto your servo output discs to achieve the
throws. However, it is mandatory to secure these to metal
servo output discs, or to use full metal servo arms (like
those shown below from SWB) - and not the standard plastic output discs supplied with the servos. The extreme
torque of the current hi-torque digital servos can strip the
plastic splines from the inside of the disc - which will result
in immediate flutter and destruction of your Extra. Several
reputable accessory companies make aluminium discs and
servo arms, but you should check that the CNC machined
splines fit onto the servo output shaft tightly, with a minimum of lost movement/play.
Secure the phenolic arms to the servo output discs as follows: Fit the metal discs to the servos.
Centre both elevator servos using your R/C and attach the phenolic servo arms to the outside of
the metal discs temporarily with a couple of drops of CA, making sure that the servo arms are
both at 90° to the bottom surface of the stabs using a set square. Then remove the arms and
discs, drill through both, and secure with at least 2 small bolts, washers, locknuts and Loctite (M2
bolts and nuts included). Add a drop of Loctite to the bolt that secures the discs to the servos.
Use this same method to attach the phenolic extension arms to metal discs for the aileron &
rudder surfaces also.
At Composite-ARF we only use the aluminium ‘Double-Loc’ servo arms from SWB manufactur-
Composite-ARF Extra 260 (2.6m span)
16
(above) Servo is screwed into the
milled cutout in the inner rib.
*
(above) If you use the phenolic
servo arm extensions, you MUST
bolt these to metal servo discs.
(below) The alternative is full metal
servo arms, such as these SWB
‘Double-Loc’ types that we use on
most of our factory planes.
Page 17
ing (USA) and we highly recommend them. These arms
clamp onto the servo output shaft with no lost movement
(play) at all. These are high quality, properly engineered
arms, and are available from many good hobby stores.
With your chosen servo arm secured to the servos, fit them
in place in the milled cutouts in the stabs and secure with
the 2.9 Ø x 13mm sheetmetal screws we have included.
It is most important that the linkage from the servo arms
is exactly in-line with the phenolic control surface horns in
the elevators, as any ‘side-load’ or ‘twisting’ could weaken
or even break them, causing flutter and destruction of your
Extra. If you have chosen to fit full metal servo arms, (eg:
SWB), you can fit a single-sided ball-link onto the servo arm
to adjust the line of the linkage if necessary - but you must
not fit a ball-link to a phenolic or plastic servo extension
arm, or phenolic control surface horn.
If your chosen servo arm system does not line up perfectly
with the factory-milled slots for the phenolic control horns,
you can either fill the slots and mill new ones - or even pack
the servo off the rib slightly inside the stabiliser (with thin
plywood) to adjust the alignment. Make up the elevator linkages from the hardware supplied, using M3 x 45mm
threaded rods, and M3 steel clevises and nuts at both ends.
If you use a full metal servo arm, then you may need to use
a wider clevise with a separate pin and E-clip, because of
the thickness of the arm and the sizes of the holes - as
shown on the SWB arms here. This also applies to the
aileron horns, of course.
Control Horns
The slots for the phenolic elevator control horns are already
partly milled in the elevators for you, and may be adjusted
or repositioned if required. Extend the slot for the elevator
horn to least 20mm deep, using a Dremel mill or small
Permagrit file, checking alignment with the servo arm/linkage as you work. Trim the length of one of the phenolic control arms so that the hole for the clevise is approx. 25mm
from the surface of the elevator, and rough-sand the part
that will be glued into the balsa block inside the elevator.
Ideally the hole in the horn for the clevise should be exactly perpendicular to the centre of the hinge tube.(see P7)
Wax the area with clear car wax, cover with a layer of plastic parcel tape over the area of the milled slot, re-wax the
tape carefully, and then cut through the tape with a very
sharp knife to allow the horn to be glued into the slots. The
tape stops excess glue getting on the painted elevator, and
makes the clean-up easy and quick.
Composite-ARF Extra 260 (2.6m span)
17
(above) Elevator horn alignment
template from scrap plywood. Line
is hinge tube axis. Use for both elevators to ensure same throws.
(below) Stab retaining bolt, with
clear tape over it secure for flight.
The small pieces of tubing stop the
quick-links from opening.
(above) You can ONLY use a balllink on a full metal servo arm to
adjust linkage alignment. Do NOT
use on phenolic arms or horns.
(below) Use brown parcel tape
and a coat of clear wax to protect
paint & make easy clean-up when
gluing in all control surface horns.
(NB: Extra 300SX shown here)
Page 18
Make up the servo linkage from the hardware provided, and connect your servo arm to the control horn, which helps to hold the horn in exactly the correct position while the glue cures. Fill the
slot in the elevator with slow epoxy and micro-balloons (at least 30 minute cure), or a thixotropic resin like Loctite Hysol 9462, insert the horn, and then wipe away excess glue. Check that it
is aligned perfectly with the linkage, the clevise hole is 25mm from the surface of the elevator,
and is perpendicular to the hinge axis. View from the back or front to check that the horn is at 90
degrees to the surface of the elevator. See photos P6 and P7 for ideal linkage.
When cured, remove the plastic parcel tape and make a template, as shown above, so that you
can copy the position to the horn on the other elevator. In this way you will get exactly equal elevator throws without lots of mixing and linkage adjustment when setting up your plane. You can
make the template from scrap plywood, and use an old 1.5mm (1/16”) drill bit to insert into the
clevise hole, secured with a drop of CA. Using the template, glue the horn into the other elevator in exactly the same way.
The linkages between the servo arms and elevator horns are made from the 45mm x M3 allthread, with 2 steel clevises and 2 x M3 nuts for each stab. ‘Loctite’ the quick-link and lock-nut
on one end of each linkage. If using full metal arms, like the SWB arms shown, you will need to
replace the steel clevise on the servo end with a larger type as shown here. If using clevises with
aluminium pins in aluminum servo arms, we highly recommend that you apply a little grease on
these joints to give smooth movement and prevent any chance of the aluminium pin binding in
the servo arm hole.
Use this same technique described above, using templates for the inner/outer aileron horns.
Throws
If you need more travel on the elevators than the factory
assembly allows (about 40°) you will need to increase the
length of the slots in the composite/balsa false leading
edge of the elevators with a small file. The outer 2 slots in
particular will need to be longer, and you can extend them
almost right out to the composite skin. Unfortunately it’s not
possible for us to mill these slots longer during manufacture
- as the L.E. spar would fall apart on the CNC milling table.
However, this is a very quick job with a Permagrit file, or
similar (see photos right), and you can easily achieve 50
degree throws if you wish.
Note: Several photos of the stabs in these instructions
show the 1.5” SWB arms on JR8511 servos, with the clevise in the outer hole - and this was used for extreme testing of the model and stabiliser servo system, with more
than 50 degrees throw possible.
Stab Tube
The last job is to fit the M3 stab retaining bolts. Inside the
stabs you will see the small ply reinforcement plates
between the spar sleeve and the bottom surface of the
stab. Mark the bottom of both stabs in the centre of this plywood. Install the aluminium tube into 1 stab, and drill a
2.4mm hole right through the stab surface, the plywood
plate, fibreglass sleeve and the 20mm aluminium tube. The
Composite-ARF Extra 260 (2.6m span)
18
(above/below) You can increase
available throws by lengthening
the slots in the leading edge of the
elevators, especially the 2 outer
slots. Use a fine flat file, such as a
Permagrit, and be careful not to
make the slots any wider. (Extra
300SX elevator shown)
*
Page 19
centre of the hole will be 26 - 28mm from the stab T.E.
Thread the hole with an M3 tap and secure it with an M3 x
16 bolt. Then glue an M3 blind nut (included) inside the
spar tube, with some 30 minute epoxy and micro-balloons.
Wax or oil the bolt first! Fit both stabs to the fuselage, check
that they fit tightly to the fuselage at the roots, and then drill
the hole in the other stab and spar tube, and tap the thread
as before. Counterbore the holes in the bottom surface of
the stabs for the boltheads so that they sit flush on the
small plywood plates.
TIP: Try to always leave the stab tube fixed into one stab,
and never remove that one bolt, as it is difficult to find the
right position for the stab tube again if it is removed from
both stabs!
Rudder
Trial fit the the double-sided phenolic control horn in the slot
that is already milled in the base of the rudder, mark the
central part that will be glued in, and scuff it well with coarse
sandpaper. There is a balsa block above the horn position
inside the rudder, and this should also be scuffed with
sandpaper or a small file. Adjust the milled slot in the rudder so that it is a little higher than the phenolic control horn
thickness, so that all the glue is not scraped off the horn
when you insert it into the rudder !
Cover the rudder both sides around the slot area with
masking tape, wax the area, and then cut through the tape
to expose the slot with a sharp knife - in the same way as
described for the elevators. You can also protect the outsides of the phenolic horn with tape, and this makes it easy
to clean off excess glue afterwards. Glue the horn in position with slow (min. 30 minute) epoxy & micro-balloon mix,
making sure that it is perfectly centred and level in the rudder. (Photo P8.)
When the glue has cured, fit the rudder to the vertical stabiliser with the Ø 4mm aluminum hinge tube. Check for
smooth movement. You can increase the lengths of the
slots in the rudder L.E. in same way as for the elevators for
extra throw if necessary.
The rudder servo mounting tray can be installed in 2 different positions, and the milled parts are
supplied for both options. If using a lightweight engine, such as the 3W shown here, you will definitely need to install the rudder tray as far forward as possible for correct Centre of Gravity,
against the back of the landing gear mount. If using a 100 - 125cc twin, then you may be able
Composite-ARF Extra 260 (2.6m span)
19
(above) Scuff up the gluing surfaces on the phenolic rudder horn
and glue into the slot in rudder.
(below) The Tank base/Rudder tray
is assembled from the milled parts
included. Shown here with the
bulkhead glued to the front of the
tray, for fitting in the rear position
(for large motors)
(below) M3 blind nut glued into
elevator spar tube.
Page 20
install it at the back of the cockpit, as shown in the photo
right, but this will also depend on the weight and position of
your batteries and exhaust system.
Assemble the tray and install the servos and phenolic arms
outside the model, and decide which position you will install
it in. Lightly sand all composite balsa milled parts, and glue
together with thin CA. Add the 3mm thick plywood strips
underneath each servo rail, cut from the 12mm wide ply
strips provided. Then reinforce all joints with 30 minute
epoxy. (see photo P9)
Servos
The recommended choice of servos is similar to that for the
elevators, either a pair of JR/Graupner 8411/8511/8611’s or
a pair of Futaba S9351’s.
Servo arms
The supplied phenolic rudder servo output arms must be
bolted to 1” or 1.25” diameter metal servo output discs in
the same way as the elevators. We used ‘Hangar 9’ #
3520’s. Please do not use the standard plastic discs for
this, as there is a chance that the internal plastic splines
can be stripped by the current hi-torque servos - causing
instant rudder flutter, and probable loss of your plane.
Fit the 2 rudder servos into the tray, with the output shafts
nearest to the tailplane, and screw into position using the
2.9mm Ø x 13mm long sheet-metal screws supplied. Fit the
metal servo discs, and centre both servos using your R/C.
Rough sand and clean the bottom surface of the 2 phenolic horns, and the top of the metal discs.
With the R/C still switched ‘ON’, place the C-ARF rudder
servo horns on top of the output discs, with the ‘hooks’ of
the back arm facing forwards, and align them exactly parallel. Tack glue the phenolic arms on top of the output discs
with a couple of drops of thick CA. When the glue has
cured, remove the arms and discs, drill through both and secure with at least 2 small bolts, washers, locknuts and Loctite (M2 bolts and nuts included). Finally add a drop of Loctite to the bolts
that secure the discs to the servos.
Make up the linkages between the phenolic 2 arms from the M3 ball-links, threaded rod and steel
clevises included, as shown above. You will need to drill the inner holes on the back arm out to
3mm diameter for the M3 x 16mm bolts that secure the ball-links. Fit just one of the linkages
between the phenolic arms, and adjust the length of the linkage very carefully until so that there
is minimal buzzing or humming from the servos at idle, and at full throw. When satisfied, add the
other linkage and follow the same method of adjustment.
Install the completed tray in the fuselage, prepare the area for gluing with sanding, and glue the
assembly in position with at least 30 minute epoxy. Fit the small balsa sub-bulkhead to the back
of the tray if in the forward position, or the front if the tray is in the rear position (photo P10).
Composite-ARF Extra 260 (2.6m span)
20
(above) Make sure that the phenolic arms are parallel when you glue
them onto the discs.
(below) Scuff the discs and arms
before gluing. Secure with at least
two M2 bolts provided.
(above) Rudder tray and sub-bulkhead shown in the (optional) rearwards position.
Page 21
The pull-pull cables that connect the rear arm
to the rudder horn should be crossed, so that
they exit under the stabs. With the rudder
servo tray fitted in the forward position, then
the back of the slots that you must cut for the
pull-pull cables to the rudder is 195mm (7
3/4”) forward of the back edge of vertical fin,
and 40mm (1 5/8“) up from the bottom of the
fuselage. If the servo tray is in the rearwards
position, then the slots will need to be about
10-15mm further back. Cut out a small slot
first with a very sharp knife, check the position
using the pull-pull wire, and then adjust and
open up the slots with a small file as needed.
The slots should be about 3mm high and
35mm long.
Make the pull-pull wires from the hardware supplied, with a loop at the front that goes over the
hooks on the output arms, and a quick-link with threaded extender (turnbuckle) and locknut at
the rudder end.
Pass the closed loop cable through the supplied ‘crimping tubes’ 2 times before squashing flat
with pliers (see photo). Make sure that the wires are tight, and check and adjust after the first
few flights as the cables straighten out. Even a small amount of slop will prevent your Extra from
perfect tracking. You can glue a very small scrap of ply or balsa across the front of the slots on
the servo arms with a drop of CA to prevent the wires coming out of the slots accidentally.
Wings
The wings are 95% finished at the factory, and have
already been installed on your fuselage to set the alignment. Slide the wings onto the wing tube, fit the 4 plastic
wing retaining nuts onto the M6 threaded aluminium wing
dowels, and check for a perfect fit. You can sand the edges
of the wing roots a little if needed.
Wing Tube
The wing tube is a 40mmØ T6 alloy tube, which slides
inside a fibreglass tube in each wing, and it should be
980mm (38.5”) long. Please check the length to make sure
that it passes through both plywood ribs in the wing, that
are about 325mm (13”) from the root, otherwise the wing
could fail in flight.
Each wing has 2 servos for each aileron, and the openings
for the servos and hatches are already pre-cut in the wing
for you, and supplied with matching servo covers and milled
Composite-ARF Extra 260 (2.6m span)
21
(above) Each aileron has 2 servos,
mounted on hatches in the molded-in pockets in the wings.
(below) Cable exit slots in the fuselage, for the
rudder servo tray in the forwards position. Slots
move back approx. 10mm for rear tray position.
Page 22
plywood servo mounts (photo P11). Sand and clean the
inside surface of the servo hatch covers very well, and the
milled plywood parts that make up the servo mounts to
make sure you have a good gluing surface. This is very
important ! We highly recommend that you mark the 4
hatch covers now so that they are always fitted in the correct positions (eg: Starboard Inner/Outer etc).
Servos
The choice of servos is similar to that for the elevators, a
pair of JR/Graupner 8411/8511/8611’s or a pair of Futaba
S9351’s in each wing. The servos are installed with the output shafts towards the wing leading edge. The ailerons have
enough torsional flexibility to prevent servo damage if each
pair is not perfectly matched.
Servo arms
To obtain the maximum possible aileron throws quite long
servo output arms are needed (30 - 35mm/1.25 -1.5”). In
the kit we supply phenolic servo arm extensions for this
purpose, which can be fitted onto your servo output discs to
achieve the throws. However, it is mandatory to secure
these to metal servo output discs, or to use full metal servo
arms (like those shown from SWB) - and not the standard
plastic output discs supplied with the servos. Secure the
phenolic servo arm extensions to the metal output discs in
the same manner as used for the elevators, centering the
servos with the R/C and making sure that all 4 arms are all
at 90° to the side surface of the servos.
Assemble the servo mounts from the 3 CNC milled plywood
parts supplied for each servo, using thin CA, as shown in
the photos here, and P11. Fix the servos into the mounts
with the 2.9mm Ø screws provided in the kit, and secure
your chosen type of servo output arm to the servos.
Place the servos in their mounts on the inverted hatch covers to check the alignment so that the servo output arms
are exactly in-line with the pre-milled slots in the wing for
the control surface horns. The same principles apply here
as for the elevators, and you can adjust the slots in the
ailerons, or the slots in the hatch covers slightly, if necessary, depending on your servo arm type. Tack the mounts
in place onto the hatch covers with a drop of thin CA.
When satisfied, glue the servo mounts to the hatch covers
permanently, with thin CA, and then remove the servos,
and reinforce the glue joints between the servo mount and
the servo cover plate with slow (at least 30 minute) epoxy
and milled fibre, with a nice glue fillet all around. These are
important glue joints!
Composite-ARF Extra 260 (2.6m span)
22
(above) Aileron horns must extend
into the wing by at least 18mm
(3/4”). Inner & outer horns shown.
(below) Make sure control horns
are perpendicular to aileron surface and parallel to servo arm.
(above) Adjust position of servo
mounts on hatch covers so that
servo output arms align exactly
with phenolic aileron horns.
(below) Phenolic servo arm extensions may only be fixed to metal
servo output discs.
Page 23
Each servo hatch is fixed to the underside of the wing with
of the 4 sheet-metal screws provided, Ø2.9 x 10mm. These
servo mounts allow you to change a servo within a few minutes, if needed, easily within the time between 2 flying
rounds of a contest.
Control Horns
The slots for all 4 phenolic control horns are already partly
milled in the ailerons for you, but may be adjusted if
required. Extend the slots for the horns to least 18mm (3/4”)
deep, using a Dremel mill or small Permagrit file, checking
alignment with the linkage as you work.
Fit just one inner control surface horn to start with, using the
same method as described for the elevators. Trim the length
of one of the phenolic control arms so that the hole for the
clevise is approx. 23mm from the surface of the aileron,
and rough-sand the part that will be glued into the balsa
block inside the aileron. Ideally the hole in the horn for the
clevise should be exactly perpendicular to the centre of the
hinge axis on the top of the wing. (P12)
Use a layer of parcel tape and clear wax to protect the
aileron surface. Install the corresponding servo and hatch,
make up the linkage from the M3 clevises, 45mm long
threaded rod and nuts provided - and connect the linkage
from the servo arm to the control surface horn while the
glue is curing to help maintain perfect alignment. When
cured, remove the plastic parcel tape and make a plywood
template, as shown right, so that you can copy the position
for gluing in the inboard horn on the other aileron.
The 2 outer control surface horns are completed using the
same method, first finishing one, and then using a template
to glue in the other one. However, the distance between the
clevise holes in the phenolic horns to the hinge axis line (top
surface of the wing) should be the same for the inner and
outer horns. However, because the wing/aileron is 7mm
(5/16”) thinner at the position of the outer horns, these outer
horns must project of the aileron 7mm more than the inner
horns. This is to ensure that the aileron servo throws are
similar and that the servos don’t ‘fight’ against each other.
Because of the difference between the inner and outer
horns, the easiest method is to make the template for the
inner horns and glue them both in place first, and then drill
another hole in the same template 7mm higher, exactly on
a line drawn on the template that is perpendicular to the
hinge axis - and use this for the outer horns.
Composite-ARF Extra 260 (2.6m span)
23
(above) The aileron horn template
used to position the inner horns
for gluing in place. The line is perpendicular to the hinge axis.
(below) Same template, with an
extra hole drilled exactly 7mm
higher, for installing outer horns.
(above) Outer aileron horn. Clevise
hole is 30mm from aileron surface.
(below) Inner aileron horn. Clevise
hole is 23mm from aileron surface.
Page 24
Engine and Exhaust Installation
We strongly advise you to complete the motor and exhaust
installation before the fuel tank base is installed, as it provides much easier access.
The most commonly installed motor in our 2.6m Extras
seems to be the DA-100, very often with a pair of MTW
TD75k canisters, and this is an excellent combination. We
have shown photos of the installation of this popular setup below.
For the 260 prototype we chose to use a single-cylinder
3W 80cc Xi, and single ‘Greve’ tuned pipe set-up, to show
a lightweight and lower cost option. This has proven to be
a very nice combination, having plenty of power - and a
weight reduction of about 800 grams over the DA-100 version. Full details of this installation are also described
below. Any similar 75 - 85cc single-cylinder motor could
also be used, for example the ZDZ 80 or the EVO80.
The complete motor-dome is an integral part of the fuselage molding - which saves weight, increases rigidity and
ensures accurate alignment of the firewall. The front face
of the molded motor-dome/firewall on the Extra 260 is set
at 0 degrees downthrust, and 0 degrees sidethrust.
Whichever motor you are using the vertical location of the
centre of the motor on the firewall can be set as follows:
Lay a steel straight-edge on top of of the fuselage (on the
joint seam) in front of the canopy as shown in the photo
above, and measure vertically downwards 88mm. If using
a 120mm diameter spinner (as we used here) this will
make the top edge of the spinner backplate about 5 - 8mm
below the top surface of the installed cowling.
If you are using a smaller diameter spinner, then you can
raise this line by half of the difference in diameter between
your spinner and 120mm. Mark the horizontal centreline
(for your choice of spinner diameter) on the tape on the
front of the firewall now, making sure that the line is level by
eyeing thru’ a steel ruler and the wing tube.
The side-to-side location of the centre of your motor is also
easily set. It is 7mm to the (pilots) left of the central vertical
seam of the motor-dome. (see photo right). With the correct
length stand-offs to set sidethrust at 2.5 - 3 degrees then
spinner will be centred on the cowling horizontally.
Note: We installed both motors in the same fuselage for
these instructions, so you may notice some extra holes
and cutouts in the photos.
Composite-ARF Extra 260 (2.6m span)
24
(above) The top of the spinner
should be about 5- 8mm below a
straight edge laid on the cowling.
(above) For a 120mmØ spinner,
measure 88mm down from a steel
straight edge placed on the fuselage in front of the canopy frame.
This is the vertical centreline of the
motor position.
(below) The side-to-side centre of
the motor should be 7mm to the
pilots left of the motordome seam.
The cutout shown here is for the
rear-mounted 3W carburettor.
5- 8mm
7mm
Page 25
3W 80cc Xi.
For this set-up we used a C-ARF 120mm diameter carbon
spinner (# 810105), a Greve tuned pipe (# 910200), with
the original manifold supplied with the 3W motor, and a
Mejzlik 27 x 10 carbon 2-blade prop.
3W state in their instructions that the engine must not be
mounted directly to metal stand-offs, as unequal lengths, or
unequal tightening of the bolts could cause crankcase distortion. Therefore we made a mounting plate from 2 layers
of 3mm carbon-composite plywood, glued together with
24hr laminating epoxy, and bolted the engine to this with
M5 bolts, washers and lock-nuts. Then the carbon-ply
mounting plate was secured to the firewall using 4 standoffs of 20mm length, with the M6 bolts and washers included in the hardware. (see P13 - P16)
As it is a single-cylinder engine we chose to use anti-vibration mounts in the carbon-plywood mounting plate, made
from the usual ‘well-nuts’ (or short lengths of hard silicone
or rubber tube) to isolate the mount from the firewall, and it
certainly does helps to prevent transmission of vibrations to
the airframe.
Four 9.5mm diameter holes were drilled in the carbon plate
for the M6 bolts, and the well-nuts were inserted from the
front face, with the excess length trimmed flush with the
back surface. The M6 bolts should be a fairly tight fit inside
the well-nuts or tubes used. If you use short lengths of hard
rubber or silicone tube, instead of the well-nuts, then you
will need to add a rubber washer on the front face, instead
of the flange on the well-nuts. Rubber washers can be easily cut from motorcycle tire inner tube with a sharpened
brass tube. An M6 steel washer is used on the front face,
under the head of the M6 bolt.
On the back face, between the carbon/ply plate and the aluminum standoffs, another 16mm (5/8”) Ø rubber washer
was added. Use Loctite on the M6 bolts that pass thru’ the
isolation mounts in the carbon plate to secure them firmly
into the stand-offs - and be careful not to tighten the bolts
up so much that you completely compress the rubber and
eliminate the anti-vibration system! Make sure that you add
Loctite to all the M5 and M6 engine mounting bolts, and
check them regularly. The photo (above) shows the order of assembly of the parts.
You need to cut a hole in the firewall for the rear-mounted 3W carburettor, and the 3W instructions include a full-scale drawing of the engine mount positions and carburettor which is very
useful when making the mounting plate and carb cut-out. We highly recommend that you fuelproof all bare wood inside the motordome/tank base area with a thin coat of laminating resin, as
these carbs can spray a thin mist of gas (petrol) from the venturi.
Composite-ARF Extra 260 (2.6m span)
25
(above) Shows the cutout for the
3W carb, and also the holes from
the DA-100 mount plugged with
6mm hardwood dowels.
(above) Shows the order of assembly of the anti-vibration mounts in
the carbon-ply mounting plate.
(below) Sidethrust and upthrust
are set with stacks of large diameter washers between the 20mm
standoffs and firewall. The wire
below operates the choke.
Page 26
To set the sidethrust we added a stack of large diameter
washers between the left-hand two standoffs and the firewall, of 5.5mm thickness. To add a very slight upthrust, we
also added one thin washer (0.7mm thick) behind the lower
2 standoffs. These can be adjusted by adding or removing
washers to finalise the thrustline after first flights.
The header/manifold used was the original aluminium
PEFA item, supplied with the motor. If used, you will need
to carefully bend it - opening up the bend a little, to fit as
shown in this installation. Approx. dimensions of the header used are on page 45 oif this Instruction manual.
Tuned Pipe.
Although a bit more complicated to install than a canister
muffler, we fitted a tuned pipe as it gives some increased
power, improved throttling characteristics and reduced
noise levels - especially important in Europe where there
are quite strict laws on this. We used the Greve pipe as it is
quite small diameter (49mm). Using the layout shown here
you would be able to install a pipe of up to about 55mm
diameter. You must maintain a gap of at least 6mm
between the pipe and the wing tube sleeve, and also above
the landing gear mount and carbon legs.
The pipe is supported at the front and back on 2 cnc milled
plywood mounts which are included in the kit (to suit Ø
49mm pipes), together with enough of the 10mm Ø hard silicone tube to make the isolation mounts. Cut the silicone
tube into 20mm lengths and insert in the milled slots as
shown in the photos below/right. The front pipe mount is
secured to the back face of the plywood landing gear mount
with 2 large sheetmetal screws (Ø 3.5 x 18mm).
The rear mount must be secured to a 3mm thick plywood
reinforcing plate (cut from the 12mm wide strip supplied)
glued firmly onto the side of the fuselage, on the back face
of the rear cockpit bulkhead, as shown - and you can use
two of the M3 bolts and T-nuts included in the spare hardware pack for this.
Make sure that the tuned pipe cannot move forward (or
backwards) and touch against the end of the manifold, as
the metal-to-metal contact could cause terminal R/C interference! 2 small sheet metal screws through the teflon joiners and pipe/manifold side walls prevent this.
Canister mount
Depending on your motor and header, you should find that
a single canister (MTW TD110K shown here) will fit in front
of the wing tube sleeve, but you will may need put the canister on the opposite side of the fuselage to the cylinder -
Composite-ARF Extra 260 (2.6m span)
26
(above) Prevent the canisters or
tuned pipe moving forwards or
backwards with 2 small sheetmetal
screws thru’ the teflon coupler.
(below) Rear pipe mount is
secured with two M3 bolts and Tnuts to a 3mm thick plywood plate
glued securely to the fuselage side
behind the rear cockpit bulkhead.
(only 1 T-nut shown here)
(above) Front pipe mount is
screwed to back of LG mount.
Page 27
and use a ‘cross-over’ header to give you enough length.
Included in the kit is one cnc milled plywood mount to suit
the TD110K, or similar 80mm diameter canister. Insert
20mm lengths of the hard silicone tube in the corner slots
to make the isolation mounts, in the same way as shown for
tuned pipe mounts. The plywood mount can be screwed to
the front of the landing gear mount bulkhead with 2 of the
Ø3.5 x 18mm sheetmetal screws included in the hardware
pack. 2 small holes drilled in the bottom of the motor dome
allow access from the front with a long screwdriver. If necessary you can sand a small notch in the top of the forward
landing gear mount bulkhead to maintain at least 6mm
clearance between the plywood and the canister/pipe.
Desert Aircraft DA-100
The DA-100 installation and set-up uses the same principles and motor centreline positions as detailed above.
Because it is a twin-cylinder motor it has lower vibration levels and it is not necessary to incorporate an anti-vibration
mount. The motor fits fully enclosed in the cowling (see
P20). For this set-up we recommend a C-ARF 120mm
diameter spinner, MTW TD75k cans and headers, and a
Mejzlik 28 x 10 carbon 2-blade prop.
Mark the horizontal and vertical motor centreline positions
accurately on the front of the firewall in same manner as
described at the beginning of this section, dependant on
your spinner diameter. The 4 mounting holes for the DA100 are 70mm apart horizontally, and 80mm apart vertically. Mark half of these dimensions equidistant either side of
the centrelines and bolt the motor to the stand-offs. Drill the
4 mounting holes through the firewall, 6mm diameter, and
secure the 20mm long standoffs using the M6 x 16mm allen
bolts and washers supplied in the hardware pack, with a little Loctite for security. Set the side and up thrust using
stacks of large diameter washers, in the same way as
described above. (see photos P17, P18 and P19)
Fit your headers/manifolds to the motor and cut the necessary holes in the lower part of the motor dome to suit.
Canister and Header Installation
Shown here is the installation of a pair of MTW headers and
TD75k canisters, as included in the optional set available
from Composite-ARF. (see relevant webpage for details of
currently available accessories & options).
The assembled canisters and headers are inserted into the
fuselage through holes that you need to cut in the lower
Composite-ARF Extra 260 (2.6m span)
27
(above) A single 80mm Ø canister
(TD110K shown) can be fitted - but
you may need to use a cross-over
header to get the correct length.
(below) You can sand shallow
notches in the forward landing
gear mount, if necessary, for
exhaust system clearance.
(below) MTW headers & canisters
are available as optional items from
C-ARF. Shown here are the TD75K
cans and headers for the DA-100.
Page 28
surface of the motordome, as shown in the photo below, but
do not cut through the 25mm fibreglass joining tape in the
centre of the motordome.
Included in the kit are 2 cnc milled plywood mounts to suit
the TD75K canisters, or similar 70mm diameter cans (eg:
Zimmerman). Insert 20mm lengths of the (included) hard
silicone tube in the corner slots to make the isolation
mounts, in the same way as shown for tuned pipe mounts.
The plywood mounts can be screwed to the front of the
landing gear mount bulkhead with 2 of the Ø3.5 x 18mm
sheetmetal screws included in the hardware pack. No other
support is needed. Install 2 of the small sheetmetal screws
though each the teflon joiner into the canister entries and
headers to make sure that the cans cannot slide forwards
or backwards.
Motor Cooling
It is imperative that your chosen motor not only receives
sufficient air to cool it through the opening in the front of the
cowl, but that the air is forced to go through the cooling fins
of the cylinder(s) - otherwise the air will just take the easiest route and exit the bottom of the cowl without doing any
cooling. In this case you will overheat, and damage, your
valuable motor.
Depending on your motor you will need to make some sort
of baffle to force the air through the cooling fins, and this
can be made from scrap 1.5mm plywood or 3mm balsa.
The full-size template at the end of this manual fits the
cowling, positioned about 6mm below the bottom of the
front cutout, and the back edge of the baffle can be adjusted slightly to suit your chosen motor.
Make the back edge of the baffle about 6mm (1/4”) clear of
the cooling fins of the cylinder(s) and the crankcase. Glue
the baffle plate into the cowl with epoxy. It looks neater if
you paint it matt black first, using heat-proof spray paint (as
used for car manifolds/exhausts).
The air exit at the bottom/rear of the cowl is rather small on the Extra 260 and, especially if you
fly in a warm climate, we recommend that you extend it to the front by 50mm - as shown in the
photo below. Cut the cowl, following the shape of the original molded sides as shown.
Exhaust Cooling
Whatever type of exhaust system you chose to fit, make sure that the assembled headers and
canisters, or pipe, can be inserted from the front, through the motor-dome - and make the hole(s)
at least 18mm (3/4”) bigger than the exhaust all around to ensure enough air enters the fuselage
to cool the exhaust system. For the tuned pipe set-up described above, we cut a hole of 85mm
(3.25”) diameter.
Of course, this warm air must also exit the fuselage - so you also need to cut sufficient air exits
Composite-ARF Extra 260 (2.6m span)
28
(above) Plenty of room to install a
pair of MTW 75K cans in front of
the wing tube, supported with the
milled mounts supplied in the kit.
(below) Typical cnc milled plywood canister/tuned pipe mount
& hard silicone tubing included in
the kit to suit Ø 49mm pipes, and
both Ø 70mm & 80mm canisters.
(above/below) Baffle installed in
the cowl for the 3W motor.
Page 29
in the bottom of the fuselage. As a general rule the total
area of the air exits must be at least double the inlet area.
For example if the hole in the motor dome for the tuned
pipe is 75mm (3”) diameter (area = 4400mm
2
), then the
total air exit area should be minimum 8800mm
2
. This is
equal to 2 slots of 50mm (2”) wide x 90mm (4”) long. The
slots shown here for the single tuned pipe are 35mm wide
and 150mm long.
The balsa fin post also has cnc milled cut-outs in it, to help
prevent a build-up of hot air inside the fuselage. From our
experience we have found that 2 slots, each of about
150mm x 35 - 40mm wide provide excellent cooling for both
the 3W and DA-100 set-ups shown here. If you fit dual canisters, then the slots will need to be positioned just behind
the landing gear mount, either side of the rudder servo tray.
Cut the air exit slots in the bottom of the fuselage with a
sharp knife, or mill with a dremel tool, and sand the edges
to shape with 240 grit sandpaper - remembering to radius
all the corners to help prevent tearing of the composite
sandwich skin. It is advisable to reinforce the edges of the
cutouts inside the fuselage with a few carbon rovings, or
narrow strips of plywood. (photo P21)
It is also helpful to make small tabs at the front of the cooling slots to make sure that the warm air is sucked out of the
fuselage. These can easily be made by making 2 cuts in the
skin, about 20mm long, bending the skin outwards about 30
degrees, and creasing the inner surface with the back
(blunt) edge of the knife blade. Hold in position, and apply
a couple of drops of thin CA to the sandwich from inside the
fuselage to maintain the angle. (photo above)
Firewall Brace
Included in the kit is a milled 3mm thick plywood firewall
brace, which should be securely glued between the bottom
back edge of the firewall and the front of the landing gear
mount, with slow epoxy and micro-balloons mixture. You
may need to adjust the length slightly due to manufacturing
tolerances. This brace helps to eliminate vibrations, and is
especially important if you fit twin canisters as there will be
2 quite large holes in the bottom of the motordome.
Composite-ARF Extra 260 (2.6m span)
29
(above) Extend the exit in the bottom of the cowl by 50mm, following the line of the original moulding
for additional cooling. Note the
Ignition Nicad securely fixed to the
bottom of the baffle, and small slot
for access to the choke arm.
(below) Radius the corners of all
air exits, and cut angled tabs at the
front to create some turbulence &
make sure the air is sucked out.
Glue the plywood brace securely
between the firewall & LG mount.
(below) The milled plywood firewall brace is supplied in the kit.
Page 30
Fuel Tank Base
The Fuel tank base supplied is a cnc milled balsa/composite assembly, that also provides space for mounting the
receiver and Powerbus system. It is reversible - so you can
fit the Rx and Powerbus on either side of the fuselage.
It is sized to fit a Dubro 950 cc tank (part #690), but can be
adjusted to suit your choice. Depending on the size of your
fuel tank, glue a scrap balsa block at the front of the tank
base to stop the tank moving forwards. Secure the fuel tank
to the tank base with cable-ties through the milled slots, as
shown in the R/C installation section.
Lightly sand all the parts, assemble with thin CA as shown,
and then reinforce all joints with a fillet of 30 minute epoxy
and micro-balloons. If fitting a motor with a rear mounted
carburettor - then don’t forget to seal the bare edges of the
balsa sheet with a brushed-on coat of thin epoxy.
You can choose to permanently glue the tank base in place
to the sides of the fuselage, or make it removable - which
is more convenient for maintenance and access - especially if you have the rudder servo tray in the forward position.
If you want to make it removable you can use the 10mm
thick balsa strip and 8 of the 20 x 20mm milled plywood
squares included in the kit to make 4 mounting blocks as
shown. Glue 2 of the milled ply squares to the top of each
balsa block. Sand the blocks to fit against the fuselage
sides, prepare the areas well for good glue adhesion, and
glue in position with at least 30 minute epoxy and microballoon mixture.
When cured, the complete tank base assembly is held in
position with 4 of the large (Ø3.5 x 18mm) sheetmetal
screws provided. Use washers under the screw heads, and
glue some some scrap 1.5mm (1/16”) plywood plates to the
top of the tank base in the position of the screws to spread
the load over the surface. (see photo right). Make sure that
the tank base is very securely fixed in position.
See also photos P22 and P23.
Composite-ARF Extra 260 (2.6m span)
30
(above/below) Make 4 blocks from
the balsa & plywood parts - and
glue securely into position.
(bottom) Tank base is fixed to the
blocks with 4 of the large sheetmetal screws, and washers.
(above) Tank base assembled.
Production base is larger giving
space for receiver and Powerbox.
Page 31
R/C & Gear Installation
Everyone has their own favourite methods
and layouts when fitting the R/C and gear. The
installation shown here, and on the full-color
photosheets, are just a guide, but have
worked perfectly in all of our planes flown by
C-ARF factory staff, and many of our customers.
You have several choices of R/C system. You
could keep it simple, and use Dual receiver
batteries and a Powerbox sensor switch,
which includes a regulator and battery-backer,
or you could go for a ‘full-house’ set-up using
a high-quality servo powerbus system for the
ultimate in safety and security. It’s your
choice, but the dual Nicad and powerbus
installation does give extra ‘peace of mind’
and protects your investment, and therefore
this is what C-ARF recommend and have
shown here.
The PowerBox Evolution power control unit is
designed especially for large models and provides dual battery inputs with hi-amp connectors, multiple outputs for
5channels/18 outputs (no ‘Y’ leads needed), automatic voltage regulation and stability, built-in servo amplifiers for
those long servo cables, as well as dual visual LED battery
displays. It comes complete with hi-current connectors and
is fitted with anti-suppression chokes on all channels. The
full ‘PowerBox’ range is available from C-ARF as an option.
Please visit our website for more details.
Ignition Batteries
We always use 2400 (sub-C sized cells) for the ignition system. The 4-cell pack for the DA-100 should be secured
inside the front of the motor dome with cable-ties, and the
5-cell pack for the 3W motor was fixed to the underside of
the motor baffle plate in the cowling to move it as far forward as possible - for correct Centre of Gravity. Small plywood strips were glued to the balsa baffle to spread the
load of the cable ties (photos on page 28 and 29). The battery cable plugs into a Multiplex connector that is glued into
the bottom of the motor dome, for ease of removing the
cowling.
Receiver Batteries
To save weight in the 3W powered plane, we chose two 5cell (AA+ sized) 1400 mAH packs - and these were both
fixed inside the front of the motor dome, using cable-ties
thru’ the fibreglass fuselage skin. All battery packs should
Composite-ARF Extra 260 (2.6m span)
31
(above) There is plenty of space to
fit the Powerbox Evolution and Rx
on the right (or left) side of the fuel
tank base.
(below) An alternative method of
securing the Rx to the mounting
plate, using 2 rubber bands.
(below) 2 Rx batteries wrapped in
foam & secured in cowl with cableties for the 3W powered plane.
Page 32
be wrapped in foam to isolate the soldered connections from vibration as much as possible.
For a DA-100 powered example you should find that with all 3 batteries (2400 sub-C size)
secured in the cowling, and the rudder tray in rear position, will easily give you the correct forward ‘pattern’ CG position.
Make sure that all batteries, and other heavy items, are very securely fixed in the plane - remember how much they will effectively weigh when subjected to 4 or 5 G’s!
Receiver
C-ARF strongly advise that you position the receiver as far away from the high-voltage ignition
unit as possible - at least 200mm (8”) for the minimum interference risk. We positioned the
Powerbox Evolution and the RX on the balsa-composite plate on the right side of the tank base.
Please mount the sensitive Receiver on a rubber or foam
sheet, at least 3mm thick, to isolate it from vibrations. You
can easily secure the Rx either using 2 small cable-ties, or
by gluing a plywood stick across 2 large holes in the mounting plate - using 2 rubber bands around the Rx case. (see
photo above)
RX Antenna
The Rx antenna was routed to the side of the fuselage,
then backwards along the fuselage side and out of the top
of the fuselage immediately behind the canopy - and taped
to the top of the fuselage. Secure it in short lengths of silicone tube to make sure it cannot be cut through by any
sharp edges. Keep it as far away as possible from the
cables for the elevator servos and the closed-loop rudder
wires.
Switches
Often regarded as the ‘weakest-link’ in an R/C system, it is
very important to use quality switches for both
Receiver/Powerbox and motor ignition, and we only use
high quality switches from Power box. The electronic switch
included with the Powerbox Evolution is a ‘Fail-ON’ type, as
is the Powerbox ‘Sensor’ switch. We use the analog 20
Amp power-switches, also from Powerbox, for the ignition
system.
If fitting the switches into the outside surface of the fuselage, as shown, please reinforce the area inside with a
small patch of 3mm thick plywood to reduce vibration transmissions to the switches. It only adds a few grams. The
Powerbox switches come with paper templates, making it
easy to cut the slots in the fuselage accurately.
Servo Extension leads etc.
Please make sure that you use good quality twisted-cable
extension leads, of heavy gauge wire with gold-contact
connectors, to all the servos. Certainly we recommend that
all servo leads and extensions longer than about 30cms
Composite-ARF Extra 260 (2.6m span)
32
(above) PB Switch mounted in
fuselage side, with ply reinforcement. Antenna wire and stab
extension cables are routed thru’
silicone protection sleeves and
fixed securely.
(above) Protect all wires and tubes
where they pass thru’ bulkheads,
or near sharp composite parts,
with a short length of silicone tube,
and cable-tie firmly in position.
(below) Secure all hidden servo
plugs/sockets with heatshrink.
Page 33
(12”) are fitted with ceramic chokes (ferrite rings) to prevent
RF noise, at the receiver end - normally within 100mm (4”)
of the receiver. Of course, if you are using a ‘Powerbox’ this
unit is already fitted with all the ceramic chokes. Also no ‘Y’
leads are needed, as the powerbox provides multiple inputs
for each channel.
At C-ARF we hard-wire all our servos with twisted cable
leads of the exact length required and Multiplex 6-pin connectors (see photo right). For the 2 aileron servos you can
use 1 pin for each wire, and for the elevators you can gently squeeze pairs of adjacent pins together and use a pair
of pins for each cable. We glue the female connectors into
small plywood plates in the sides of the fuselage for connecting the stabs and ailerons when assembling the plane.
Making up the proper extension cables and connectors is
only a little work, if you are proficient with a small solderingiron, and makes assembly of the model at the airfield very
quick and easy! Once all wires are soldered to the goldplated pins, fit a short length of heat-shrink tube over each
one. Finally protect all the connections from vibrations etc
with a nice blob of glue from a hot-glue gun. Job done.
Make sure that any plug/socket servo cable connections
that cannot be easily seen and regularly checked, for
example the servo connections in the wings, are secured
together with tape - or a short length of heatshrink tubing as
shown here. Also tape down any loose cables that could
get trapped or caught in linkages.
Throttle servo
You can install the throttle servo anywhere you chose,
using the milled plywood mount that we supply (photo
right). In the 260 for the 3W motor we glued it securely to
the underside of the top of the fuselage, on a 10mm
thick balsa block, with epoxy/milled fibre mixture, in
front of the fuel tank.
In a plane with a DA-100 and dual canisters, you
could glue the mount to the side of the fuel tank base
and use a balsa or carbon-tube pushrod through the
firewall to the carburettor. We advise you not to
mount it directly on the back of the firewall, due to
higher vibration levels which can quickly ‘kill’ the
servo. Note that all DA motors need quite a lot of
servo throw to get the full throttle range, so make
sure you can fit a long output arm on the servo.
M3 all-thread, steel clevises and locknuts are included in the hardware pack to make up your
throttle pushrod.
Make up a wire lever so that you can operate the ‘Choke’ for starting thru’ the cut-out in the front
of the cowling. In the 3W installation this wire is very long, because of the rear-mounted carb, so
Composite-ARF Extra 260 (2.6m span)
33
(above) Throttle servo mount
assembled from milled plywood.
(below) In the 3W set-up this was
glued to the top of the fuselage
6-pin MPX connectors are used for
extension leads, with one half
mounted in the fuselage sides.
Page 34
the wire pushrod passes through a length of silicone tube in
the bottom of the carbon plate to support and isolate it. (see
photo on page 25, and P16)
Motor Ignition System
The ignition unit is normally fixed to the motordome, as
close to the engine as possible - because of the length of
the HT leads that connect to the spark plug(s). Mount it on
a foam pad and secure with cable-ties, or use sheetmetal
screws into small plywood pads with rubber grommets for
vibration isolation. Don’t forget that the ignition unit also
gets warm during use, so it is wise to put it in a location
where there is some cooling airflow. Keep the ignition unit
as far away from the receiver as possible.
Use a very small cable tie, ‘safety clip’, or a length of heatshrink tubing to securely connect the plug and socket from
the motor pick-up to the ignition unit.
Fuel Tank
The fuel tank is held to the tank base with 2 large and 2
small able-ties. Drill a hole in the motor firewall if necessary
for the fuel feed tube from the tank to the carburettor, and
protect it where it passes through the hole using a rubber
grommet or similar. Fix the tubing securely to the underside
of the top of the fuselage with a couple of cable-ties or
equivalent, to make sure that it cannot come in contact with
the headers or hot exhausts.
Fit the correct stopper to the fuel tank for the fuel type used.
(If using Dubro tank the gasoline stopper has a small ‘O’
moulded in the top of it). We use the excellent ‘Tygon’ brand
of fuel tubing for all our aerobatic models. It is totally gasoline and kerosene-proof, and does not go hard and crack
with age. Secure the feed tube inside the tank to the clunk with a small cable tie. If the tube is
even a little loose on the brass tubes though the stopper, you can be sure it will come off at just
the wrong moment and your engine will quit ! Therefore please solder some small rings onto both
ends of the brass tubing (easily made from the soft wire of a paperclip wrapped around a small
screwdriver, or short lengths of brass tube) and also secure with a fuel-line clamp or cable-tie.
Don’t miss this small detail - it could cost you your plane !
We use the normal 3 tube plumbing system, one from the clunk to feed the motor, one out of the
bottom of the plane (vent/overflow - leave open) and one at the top for filling (close for flight).
Final Check
Now check that you have fixed all components securely. Keep in mind that all the components
inside the aircraft are loaded with the same G’s as the wing and the wing spar during aerobatic
maneouvers. Check engine, cowling, wing and stab mounts carefully again.
- Are all extension leads, cables & fuel tubes securely fixed to the side of the fuselage
and cannot come loose when subjected to high ‘G’ forces during flight.
Composite-ARF Extra 260 (2.6m span)
34
(below) Secure the connectors
between the motor & ignition unit.
(below) Fit barbs to all brass tubes
and fuel connections for safety.
Easily made from a paper-clip, soldered onto the brass tubes.
Page 35
- Are all tubes and wires protected from chafing where they pass thru’ the holes in fibre
glass parts or bulkheads with rubber grommets, or short lengths of split silicone tubing?
- Especially if you have installed the internal mini-pipe set-up, you also must make sure
that no fuel tubing or wires can come into contact the exhausts. Use the plastic spiralwrap to tidy up groups of cables and make sure that they cannot move around in the
plane under high ’G’ manoeuvres by fixing them to the sides with small cable ties. If using
the easily-available cable-tie plastic fixing plates, please do not trust the double-sided
tape that they usually have on them which can fail under vibrations. Peel it off, rough up
the back face with coarse sandpaper and glue to the fuselage sides with 30min. epoxy.
- Did you fit small Tygon or silicone tube pieces over all the clevises?
- Did you tighten the M3 locknuts against all the clevises to make sure they cannot turn?
- Are the swages crimped up nice and tight on the rudder cables?
- For added security add one small drop of loctite/thread locking compound on all the bolts
that hold the servo arms to the servos, especially important with digital types.
Then you can go on set up all the linkages, control throws and R/C system as described below.
Setting Up Your Aircraft
Centre of Gravity:
Set the Centre of Gravity to 90 - 95mm (3.5 - 3.75”) from the leading edge at the wingtip for the
1st flights. Hold it with a helper at both wing tips in this position and make sure the plane balances horizontally. This is the ‘pattern’ CG position.
After you are confident with the plane, you
can move it backwards by up to 15mm (5/8”)
maximum, but this is definitely a ‘3D Freestyle’ CG setting and should not be used
for the first flights. With this rearward CG you
will need to use the high rate control throws
shown below.
Don’t forget to balance the plane laterally,
holding the spinner central bolt and a fingertip
under the rudder and, if necessary, add a
small weight to the light wing tip to make it
track correctly.
Composite-ARF Extra 260 (2.6m span)
35
C of G range:
90 - 95 mm
from Leading Edge at Wing Tip.
CENTRE of GRAVITY
90-95mm
Page 36
Engine Thrustline:
Already given in the instructions, upthrust should initially be
set at 0.5° degrees and right thrust 3 degrees, depending
on the prop used. We recommend a 27 x 10 on a 75 - 80cc
motor, and a 28 x10 carbon prop for any 100cc engine. It is
a very quiet and powerful solution. They are normally CNCdesigned, so the prop is balanced perfectly statically,
dynamically and aerodynamically, which keeps the vibration down to a minimum.
Control Throws:
All measurements are at the root/trailing edge
position. All controls should be set with a dual
rate switch.
Elevator
On high rate the elevator should really be at
maximum, up to 50 degrees both sides
(approx. 110mm), but in this case with 50%
exponential. Low rate should be no more than
50mm (2") both sides. This is the perfect
throw for nice and crisp snaps. If you like you
can add about 20% exponential to the low rate
setting as well.
Rudder
Set the high rate to maximum throw (about
190mm) both sides, and at low rate reduced
to about 140mm. The Extra needs quite a lot
of rudder for nice stall turns, so you should at
least add 25% exponential for smooth tracking corrections. At the same time you should
remember that the Extra rudder is very sensitive, and the plane starts shaking at high
speed if the rudder linkage is not really rock
solid. So check your linkages and closed-loop
cables again and make sure that there is NO
slop at all ! On the other hand these characteristics are also the reason for best rudder
sensitivity at the slowest 3D-speeds.
Ailerons
Aileron throw for high rate is 65mm up
and down (measured at root). Use at
least 30% exponential at high rate.
For low rate you should decrease the
throw to the TOP to 45mm, to the
BOTTOM to 50mm. Yes, you’re right this is a reversed differential due to
the hinge line being in the top skin
instead of on the centre line. You will
have to finalise this differential figure
Composite-ARF Extra 260 (2.6m span)
36
2.5 - 3° depending on propeller
SIDETHRUST
ELEVATOR THROWS
high rate: 110mm (max.)
low rate: 50mm
low rate: 50mm
high rate: 110mm (max.)
RUDDER THROWS
high rate: 190mm (max.)
low rate: 140mm
low rate: 140mm
high rate: 190mm (max.)
AILERON THROWS
low rate: 50mm down
high rate: 65mm (max.)
high rate: 65mm up (max.)
low rate: 45mm up
Page 37
during flight, as mentioned earlier in this instruction book. At high rate, for 3D maneouvers, this
doesn’t effect the rolling too much, so you can maximize the throws to whatever is mechanically possible, even more up than down if you wish. You may need to lengthen the slots in the servo
hatches by 2mm or so at the front to obtain these high rate throws.
General
Your Extra has very large control surfaces. This makes it very sensitive and reactive. It is always
possible that these huge control surfaces can flutter at high speeds if the assembly, servo installation and linkages are not made perfectly, and if a servo gear or output disc/arm strips the flutter will not stop until the plane hits the ground….
So please do yourself a favour, and make sure that you only use the best servos available, and
take the utmost care making your linkages. Check every linkage for slop, and rather reduce the
maximum throw than risking a high speed flutter due to sloppy servo gear or linkages. To prevent this for sure, we recommend reduced control travels (reduced by using short servo arms,
not by using electronic settings). Using 2 servos per aileron as described in this manual will
never overload or damage high quality servos, even if the maximum travel of each servo is slightly off. The aileron control surfaces have enough torsion flexibility so that damage to the servos
should not occur.
Flying the Extra 260
The Composite-ARF 2.6m span Extra 260 builds on the experience with our 3m Extra 260, Extra
300’s and Yak’s. The structural design is very similar, combining the incredible strength of the airframe with light weight. Lots of input from Jason Shulman, who's basic design it is, and from
Frazer Briggs, who has been flying Extra 260’s for as long as he can remember, united with 15
years of composite production experience, has made this plane structurally and aerodynamically unique.
The advantage of a 260 over all 300’s is the mid-wing design. The full scale aircraft had to abandon this design because of the poor visibility, and the limited space in the cockpit due to the wing
spar. That’s why Extra have moved the wing down, which was never an advantage for us modellers, since we watch our plane from the ground, and visibility is not a problem there. Still, the
260 had a very low profile fuselage, due to the small canopy, and this had to be changed slightly in our model. We tried to move the canopy forward as much as the 10% rule would allow, and
also raised the turtle deck, to get an even better knife-edge and rolling performance than what
the mid-wing design itself would already promise.
So now the Composite-ARF Extra 260 really is even more than expected. The performance in
rolling circles, knife edge and point rolls is really breathtaking. This was also confirmed by the
long time TOC competitor Frazer Briggs from New Zealand, who has up already had many, many
hours on our 3m version. And he really had tried to push the 260 to the point where we would
see what is the limit of this design: There is no limit. The only limit is the pilot....
However, some mixing is required to compensate for the rudder coupling. Depending from your
CG settings, we have found that about 4% opposite aileron and 6% up elevator is a good starting point (taken from the low rates, that’s why you almost don’t see the deflection). Thrust lines
are quite standard, and a slight up thrust will reduce the need to mix 1 - 2% down elevator at idle
for the perfectly straight downlines. But again, this depends very much on your preferred CG settings. With the settings given in this manual, you can go right into your first IMAC contest and
will feel great with the plane.
Composite-ARF Extra 260 (2.6m span)
37
Page 38
3D capabilities are unlimited. Since the elevators do not have a counter balance, we only could
hope that the efficiency would be enough. We were positively surprised after the first serious 3D
maneouvers, what this plane can do. Harriers are rock stable, tumbles and knife edge spins are
so easy to perform. We tried to keep the stab size at the lower end, so it would not be "overstable", and this might be the deciding factor for how great the 3D capabilities of this 260 are.
And the huge wing makes the plane feel even lighter than it really is, especially in High-Alpha
Rollers and other slow-motion stuff.
So, it is again one of those best flying planes on the planet... and you will just love it from the
first day on you fly it.
We hope that you enjoyed building your Extra 260. Please let us know if you think that any hardware is missing or inadequate. We tried to make this airplane as complete as possible. With good
feedback from customers you will help us to continue making good things even better. We appreciate your comments very much.
Email: [email protected]
Have Fun!
Your Composite-ARF Team
Composite-ARF Extra 260 (2.6m span)
38
Page 39
Appendix:
Extra 260, 2.6m Kit (version 1.0)
Kit Contents
Quantity Description
1 Fuselage
1 Wing, right (with 2 servo hatches taped in place)
1 Wing, left (with 2 servo hatches taped in place)
1 Stab, right
1 Stab, left
1 Elevator, right
1 Elevator, left
1 Rudder
1 Cowling
1 Protection bag set (wings, stabs and rudder)
1 Canopy frame
1 Wheel pant, right
1 Wheel pant, left
1 Landing gear, carbon, right
1 Landing gear, carbon, left
1 Wing tube aluminum Ø 40mm x 980mm.
1 Stab tube aluminium Ø 20mm x 330mm.
1 Clear canopy
2 Elevator hinge, aluminum tube, Ø 4mm x 475mm. (packed in elevators)
1 Rudder hinge, aluminum tube, Ø 4mm x 550mm (packed in rudder)
1 Milled wood/phenolic parts bag
1 Hardware bag
1 Instruction Manual (English)
Composite-ARF Extra 260 (2.6m span)
39
(above) Contents of the complete kit, Kiwi yellow, #712000
Page 40
Hardware List
Fuselage Pack
Quantity Description
4 Allen Bolt M6 x 30mm (engine mounting)
8 Allen bolt M6 x 16mm (engine mounting/standoffs)
8 Washers, M6, large (engine mounting)
4 T-nut, M6 (engine mounting)
9 Allen bolt, M3 x 12 (cowling)
9 Washer, M3 (cowling)
9 T-nut, M3 (cowling)
4 Allen bolt, M6 x 20mm (landing gear fixing)
4 Washer, M6 (landing gear fixing)
2 Allen bolt, M6 x 70mm (wheel axle)
4 Wheel collar, 6mm I.D, no set-screws. (wheelpants)
8 Washer, M6 (wheelpants)
2 Nut, M6 (wheelpants)
2 Stop-Nut, M6 (wheelpants)
2 Allen bolt, M3 x 16mm (wheelpants)
2 T-nut, M3 (wheelpants)
2 Washer, M3 (wheelpants)
2 Silicone tube, Ø10 x 150mm (muffler/pipe mounts)
2 Allen bolt, M3 x 16mm (pipe mounts)
2 T-nut, M3 (pipe mounts)
4 Allen bolt, M4 x 8mm (canopy frame fixing)
4 Plastic Nut, M6 (wing mounting)
2 Nut, M3 (throttle linkage)
1 Clevise steel, M3 (throttle linkage)
1 All thread, M3 x 125mm (throttle linkage)
1 Ball-link, M3 (throttle linkage)
1 Stop Nut, M3 (throttle linkage)
1 Fibreglass band, 25mm x 300mm (tank base fixing etc)
8 Sheetmetal screws, Ø3.5 x 18mm (exhaust mount & tank base fixing)
4 Washer, M4 (tank base fixing)
Wing Pack (2 sets)
Quantity Description
8 Sheetmetal screws, Ø2.9 x 10mm (servo hatch fixing)
8 Sheetmetal screws, Ø2.9 x 13mm (aileron servo fixing)
4 Bolts, M2 x 15mm (secure phenolic arms to servo discs)
4 Nuts, M2 (secure phenolic arms to servo discs)
2 All-thread, M3 x 45mm (linkages)
4 Clevise, steel, M3 (linkages)
4 Nut, M3 (linkages)
Stab Pack (2 sets)
Quantity Description
4 Sheetmetal screws, Ø2.9 x 13mm (elevator servo fixing)
3 Bolts, M2 x 15mm (secure phenolic arms to servo discs)
3 Nuts, M2 (secure phenolic arms to servo discs)
1 Allen bolt, M3 x 20mm (stab tube security)
1 T-nut, M3 (stab tube security)
1 All-thread, M3 x 45mm (linkages)
2 Clevise, steel, M3 (linkages)
2 Nut, M3 (linkages)
Composite-ARF Extra 260 (2.6m span)
40
Page 41
Rudder Pack
Quantity Description
8 Sheetmetal screws Ø2.9 x 13mm (rudder servo fixing)
2 Allen bolts M3 x 16 mm (ball-links to rear phenolic arm)
5 Bolts, M2 x 15mm (secure phenolic arms to metal servo discs)
5 Nuts, M2 (secure phenolic arms to servo discs)
2 Nuts, M3 (to lock clevises onto threaded rods)
2 Stop Nuts, M3 (ball-links to phenolic arms)
2 All thread, M3 x 45mm (ball-link to clevise)
2 Ball-links, M3 (servo linkages)
1 Steel pull-pull cable, 1.0 mm x 3300mm (rudder linkage)
4 Crimping tubes, I.D. 2.6mm (rudder pull-pull linkage)
2 Threaded ends for cables, M3 (rudder pull-pull linkage)
2 Nuts, M3 (to lock threaded ends)
4 Clevise, steel, M3 (rudder and servo linkage connections)
‘Spare’ hardware pack
* This bag contains a few extra items that might be useful in the event of future maintenance or repair.
2 Plastic Nut, M6 (wing mounting)
2 Ball-links, M3
2 Phenolic control surface horns
2 All-thread, M3 x 150mm
2 Allen-bolt M3 x 20mm
2 Stop Nut, M3
1 Allen Bolt M6 x 70mm
2 Allen bolt, M4 x 12mm
2 T-nut, M4
2 T-nut, M3
Available Accessories:
Tail gear setup with 50mm Ø wheel, size ’L’. (product #801000)
Spinner, Ø 120mm, alu. backplate & carbon spinner (product #810100 - 810103)
Desert Aircraft DA-100 motor (product #950000)
Canister set for DA-100 (product # 910100)
PowerBox 40/24, dual NiCad crossover unit. (product #960200)
PowerSwitch, pair, 20A, for dual NiCads (product #960300)
* Please check our website : www.composite-arf.com, for current availability of options and accessories.
Composite-ARF Extra 260 (2.6m span)
41
Page 42
Composite-ARF Extra 260 (2.6m span)
42
Contents of Wing Hardware
pack (2 sets)
Contents of Stab Hardware
pack (2 sets)
(above) Contents of Rudder
Hardware pack
(above) Contents of Spare
Hardware pack
(above) Contents of Milled wood and Phenolic pack
(above) Contents of Fuselage hardware pack
Page 43
Composite-ARF Extra 260 (2.6m span)
43
312 mm
Full-sized Baffle template for Extra 260, 2.6m span.
Adjust back edge of baffle
so that it is 6mm (1/4”)
from cooling fins and
crankcase of your motor.
(This line suits 3W 80cc
Xi motor)
Page 44
Page 45
Composite-ARF Extra 260 (2.6m span)
45
Dimensions of header used with 3W X1 80cc motor and Greve tuned pipe.
Mike C (16 January 2007) Mac
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