Composite-ARF Yak-55 SP User manual

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Composite-ARF Yak-55 SP (2.6m span)
Instruction Manual
Composite-ARF Yak-55 SP, 2.6m
TAVS Technology version: Preliminary

Instructions for Yak-55 SP IMAC-Airplane
Thank you very much for purchasing our Composite-ARF Yak-55SP all composite aircraft, made
with the revolutionary Total Area Vacuum Sandwich (TAVS) technology
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
This instruction manual aims to do 3 things:
1) Show you how to build your aircraft accurately and properly.
2) To explain about your fully-composite aircraft, and how to handle and maintain it.
3) How to set up and trim your finished IMAC type aircraft perfectly to give you the most enjoy-
ment from it.
The new Composite-ARF 2.6m Yak-55 SP is based on our very successful 3.3m Yak-55SP (seen
below in our limited edition ’Honeycomb’ design), which is one of the most revered planes in the
IMAC and aerobatic scene, and uses the latest moulding technology and techniques to make it
easy for you to get this plane in the air quickly, and on a very reasonable budget. We have taken
advice from many of the top TOC and IMAC pilots to improve our original design even further,
and wish to thank all those experts for their assistance.
Composite-ARF Yak-55 SP (2.6m span) [email protected]
2

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 compa-
ny 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 session check that all the model’s working systems function correctly, and be sure
to carry out a range check.
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.
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Composite-ARF Yak-55 SP (2.6m span) [email protected]
4
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 the 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-maneouvres. 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 up 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-
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 spar tube and sleeve are not damaged. Check that the front and rear
anti-rotation 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 tubes
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 Yak-55SP.
NO !!!
Secure the plane
before starting the engine.
DANGER ZONES
NO NO

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, and fully
vacuum bagged, using only 2 layers of 2 oz. cloth in com-
bination with a very hard 2 mm foam sandwich form a hard
and durable outer skin. Because of this TAVS technology
no additional structural parts are needed except for main
spar, which is a large anodized 40mm Ø Aluminium (6061
alloy) tube with a 1.4mm wall thickness.
The ailerons are hinged already for you. They are laminat-
ed 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 will never have to worry about breaking it, or
wearing it out. There is no gap at all on the top wing sur-
face, 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 disadvan-
tage, 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.
The bottom hinge slot needs some explanation, too. The cut line is exactly in the correct posi-
tion so that the aileron slides under the wing skin smoothly. If the cut was a few mm forward or
back, it wouldn't 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
Composite-ARF Yak-55 SP (2.6m span) [email protected]
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Centreline of hinge axis
Phenolic control horn
(above) Super-Xtra wings shown
with minimal internal structure.

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 rec-
ommend a pair of high-torque servos, like the JR D8411, in each wing. Our servo covers and
milled plywood mounts make both 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 fuse-
lage, and the main spar 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. Your flight will
end after 100 ft and you will have to fix a hole in your club’s
runway. 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 it is all constructed using TAVS technology.
All the loadbearing internal parts are glued in during manufacture, to ensure accurate location
and reduce the assembly time for you. The sleeve in the fuselage that takes the main 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. You have an
extremely light weight fuselage, 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 experi-
ence to engineer the strength needed in this
area - and we did !
The motordome and firewall are preinstalled,
and provide plenty of strength for any
engines up to 100cc on the market today.
See the Engine Installation section for details
of engine and setting thrust angles.
The engine cowling and canopy frame
should be attached using the method shown.
It is only a little work and this mounting has
been tested and proven for many years.
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(above) Yak-55SP full-composite
wings and 40mm Ø 6061 alloy
main spar tube.

The Stabilisers:
The stab parts are also vacuum bagged sandwiched. The
rudder and elevator control surfaces are hinged with 4mm
ø aluminium tubes, fitted through phenolic hinge bearing
plates which are installed during manufacture for perfect
alignment.
The rudder and elevator design allows for at least 50
degrees throw. All the structural parts are preinstalled. The
horizontal stabs are mounted with one 20mm tube and one
aluminium anti-rotation pin each. Please remember during
assembly of the plane that every gram of weight should be
saved in the tail area.
Take Care:
Composite sandwich parts are extremely strong, but fragile
at the same time. Always keep in mind that these contest air-
planes 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 air-
plane 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) A general view of the
Yak-55SP stabilisers.
(below) The lightweight fin-post
has the phenolic rudder hinges
already installed at the factory
ensuring perfect alignment.
A couple of views inside the new
factory, showing the a small part of the
Finishing area, and the Quality
Control/Assembly areas with the 2.6m
Yak-55SP, 2.6m Extra 330L, 2.3m Extra
and Rookie production lines.

The ‘Paint Job’
Occasionally customers notice certain problem areas with composite parts.
But the question is: Are these real problems, or are they just a misunderstood sign of high-tech
construction, proving the high-end composite technology?
Seams:
ALL composite parts have seams.
They are there today, and they will
be there forever. You will have to get
used to them ... or you’ll have to
touch up the paint yourself !
But what is a seam? A seam on the
fuselage, especially already painted
in the mould, proves that this is a
vacuum-bagged high-tech part,
made in negative moulds. Our
seams are fine and straight, no neg-
ative impression at all ... but they are
there. When possible we include
5mm wide strips of self-adhesive
vinyl, painted in exactly the same
colour as the plane for you to cover
the seams if you want.
Paint flaws:
If the aircraft is painted in the
moulds, you can save a lot of
weight. At least 2 lbs ... and that is
definitely worth saving !
A negative paint job is very compli-
cated to make. The painter never
sees the result of his job. He cannot
see the design growing and devel-
oping - he is painting ‘blind’. He
even cannot see little mistakes and
flaws, and even if he COULD, he
could not correct them. The maxi-
mum time to apply a designer paint
scheme in the mould is no more
than 20 minutes. It is a big rush
against time, because even if it is
just few minutes too slow then the
masking cannot be removed without
pulling off the paint itself ! This is a
BIG challenge, but the result is
extraordinarily impressive. Even
with slight flaws the general appear-
ance of these one-of-a-kind paint
jobs is unique.
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(above) An example of one of our big Yak-55’s in the
honeycomb ‘limited’ edition’ scheme ... all painted in the
moulds !
(below) One of our customers with the 3.3m Yak-55SP
practising his tail-in hovering on a very windy day !

In a ‘positive’ paint job some effects can never
be done. Just think about the shadows, peel
backs, highlights, and 3D effects - and all with
a perfectly flat and uniform surface for opti-
mum airflow and aerodynamics.
Truly hard to do, but still possible, are the
paint jobs which seem to be so simple at first
glance: Schemes with straight lines and
stripes. Quite easy with positive painting, but
it’s very hard masking the lines in the negative
moulds, because we cannot assemble the
parts before masking. To get the stripes lining
up exactly at the rudder, wing and cowling
joints is therefore almost impossible. This is
why we suggest using thin vinyl trim to make
sure that these stripes line up perfectly.
Sometimes it is necessary to do that, and it is
definitely not a quality problem or a "flaw". It
comes back to what is possible, and what is
impossible.
If you want to have a really
perfect paint job, then you
might decide to have a sin-
gle colour version and have
it painted by yourself or
your friend.
But don’t forget: Consider
the additional cost, consid-
er the additional weight,
consider that even if it is
painted ‘positive’ there will
be areas you won’t be
happy with.
Of course you won’t com-
plain, because you created
these flaws yourself… !
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This is the FiberClassics (now ‘Composite-ARF’) force at the TOC
2000, with all models painted in the moulds.
(above) Another view of our big Yak-55SP
showing some of the details of the incredibly
complex colour scheme - but still all painted in
the moulds.

Tools and Adhesives
Tools etc:
This is a very quick and easy plane to build, not requiring difficult techniques or special equip-
ment, 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 are 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:
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.
1. CA-Glue ‘Thin’ and ‘Thick’ types. We recommend ZAP, as this is a very high quality.
2. ZAP-O or PlastiZAP, odourless (for gluing on the clear canopy)
3. 5 minute-epoxy (highest quality seems to be Z-Poxy)
4. 30 minute epoxy (stressed joints must be glued with 30 min and NOT 5 min epoxy).
5. Epoxy laminating resin (12 - 24 hr cure) with hardener.
6. Milled glass fibre, for adding to slow epoxy for stronger joints.
7. Microballoons, for adding to slow epoxy for lightweight filling.
At Composite-ARF we try our best to offer you a high quality kit, with outstanding value-for-
money, 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: feedback@composite-
arf.com. We know that even good things can be made better !
Composite-ARF Yak-55 SP (2.6m span) [email protected]
10

Composite-ARF Yak-55 SP (2.6m span) [email protected]
Accessories
Here is a list of the things you may need to get your Composite-ARF Yak-55SP 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 recommend JR 8411’s for the ailerons and rudder, and
either 8411 or 8511/8611 for the elevators.
2. Throttle servo (1) Any standard servo will do (eg: JR/Graupner 4041)
3. Aluminium Spinner 125 - 140mm dia (5 - 5.75”). eg: Tru-Turn.
4. Main wheels 125 mm ( 5"). Dubro wheels are recommended.
5. Engine DA-100. This is the recommended engine for your Yak-55SP. The instructions
refer to that engine several times, but you could use any other 80 - 100cc engine.
6. Mini-Pipe or Tuned-pipe set. (Consists of 2 canisters/pipes, 2 aluminium headers, 2
Teflon couplers, 4 spring clamps, and mounting hardware. Available from C-ARF)
7. Standard exhaust muffler. (optional, if noise is not a problem at your field)
8. High quality heavy-duty servo extension cables, with gold connectors. High quality
receiver and ignition switches, ‘Y’ leads, ceramic/ferrite chokes etc.
9. Receiver battery. Either one 2800 mAH pack, or 2 x 1800 mAH packs if preferred.
10. Powerbox 40/24 and dual powerswitches for dual batteries if prefered.
11. Fuel tank (900 - 1000 ml) with gasoline stopper. We use Dubro.
12. Cable ties in various lengths.
13. Propeller. 2-blade Carbon Meijzlik or Menz 28” x10” for DA-100.
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 Yak-55 SP.
If not, please read it again before you start the assembly.
11

Building Instructions
Preliminary Instructions:
This instruction manual is a ‘preliminary’ version, and will be followed shortly by a fully detailed
manual - which will be downloadable from our website as a .pdf file, with full colour photos, dia-
grams, and photo-sheets with larger images to stick on your workshop wall to provide quick
reference during construction.
As you will see in a few places some of the construction photos were taken from the prototype,
which had ‘diagon-technique’ carbon reinforcing on the inside surface of the fuselage moulding
- but this was found to be completely un-necessary. The ‘production’ Yak 2.6m fuselage is
extremely torsionally strong and rigid, and does not need any further reinforcement.
With experience of the prototype we also redesigned some of the internal wood parts for the fuel
tank tray and rudder servo mounting plates, etc, to save overall weight, make it quicker and
easier to assemble, and also move the weight of these items backwards as the prototype was a
bit nose-heavy.
If you have any questions during assembly of the Yak-55SP, or can suggest any information or
details that should be included in these instructions, please don’t hesitate to email us at:
[email protected] or [email protected]
We know that even a great product can be made better !
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-plas-
tic. 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% properly before adding any decals or markings. Additionally you can cover the major-
ity 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 some-
thing 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.
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Landing Gear Finished in 2 hours
The 1st job is to fit the landing gear legs (wheel pants can
be done later) - and you can leave these in place, as they
will protect the bottom of the fuselage during assembly.
Composite-ARF developed a new carbon fibre landing gear
for the Yak 2.6m. It consists of 45 deg laminated carbon
fibre cloth and a huge number of carbon tows 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 legs are fitted through the glassfibre sleeves that are
installed at the factory, and bolted to the plywood bulk-
heads and plates shown here with M6 x 20mm bolts and
13mm Ø washers. Both main legs are identical, and can be
used either side.
Fit the wheelpants to the legs as follows: Set the fuselage
on a level surface with the tailwheel (optional tailwheel
assembly available from C-ARF) in place. Pack the bottom
of the landing gear legs up by a bit less than half the diam-
eter of the wheels used (approx. 50mm/ 2”). Position the
wheelpant against the main leg and hold in place with the
M6 x 70mm axle bolt, screwed into the threaded inserts that
are moulded into the legs during manufacture.
Set the angle of the wheelpants, with the bottom edge
angled up a little bit rather than parallel to the ground, and
secure with 2 small 2.2 x 9.5mm sheet metal screws into
the landing gear leg (see photo).
Fit the wheels of your choice. You can use any 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, and this is what we use at C-
ARF. The head of the axle bolt goes on the outside of the
wheel. The order of the items on the bolt is: Bolthead,
washer, wheel hub, 2 or 3 washers, M6 nut, washer, wheel-
pant, carbon landing gear leg. You may need to adjust the
number of washers, or add a 6mm wheel collar behind the
wheel to maintain free wheel movement and centre the
wheel against the wheelpant, depending on the actual
wheels used. A drop of loctite on the M6 axle bolt where it
goes into the threaded insert in the leg is good insurance.
Any standard tailwheel assembly from a good hobby store
is suitable for your Extra. The tail wheel setup shown in
these photos is an optional part available from C-ARF, and
is mounted with 4 sheet metal screws and 2 plastic ‘U’
brackets under the fuselage, screwed into the plywood
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(above) The wheel pant is held to
the main leg with 2 small sheet-
metal screws as shown.
(below) The completed wheel
pant and wheel (5” Dubro shown)
(above) The main landing gear legs
are bolted to plywood bulkheads
that are factory-installed.
(below) Wheel axles are M6 bolts,
which fit into threaded inserts in
the moulded carbon legs.

reinforcement installed in the fuselage at the factory.
You do not need to make the tailwheel steerable, a simple
castoring action is fine. However, for asphalt runways you
may prefer to connect it to the rudder horn with 2 springs as
shown. It’s easy to make these by winding some 0.8mm or
1.0mm 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 and the rudder horn.
Remember - keep it lightweight at the tail end!
Cowling and Grilles Finished in 2 hours
Attaching the 1 piece cowling is quite easy, as it is already
cut and trimmed at the factory, and should need almost no
adjustment for a perfect fit. With the fuselage set on it’s
main undercarriage legs, on a level table, trial fit the
cowling on the fuselage, checking that the moulded lip on
the cowl sits properly into the groove moulded into the front
edge of the fuselage. If necessary, sand the inside back
edge of the cowl slightly to get a perfectly flush fit between
the cowling and the fuselage.
Mark a centreline on the top of the cowl and the fuselage,
on small pieces of masking tape. File a small slot in the top
centre of the fuselage lip, as shown here, to take the loca-
tion tab on the milled plywood part that will be glued inside
the cowling to locate it. Tape the cowling firmly in place on
the fuselage, and glued the milled plywood tab onto the
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Optional tailwheel assembly from
Composite-ARF. It is simply fixed to
the bottom of the fuselage with
the clamps supplied, and 4 small
screws into the plywood plate that
is installed at the factory.
(above) Notice the small notch
that must be filed in the front lip of
the fuselage to take the milled ply-
wood location tab in the cowl. The
ignition system location is also
shown here.

Composite-ARF Yak-55 SP (2.6m span) [email protected]
inside of the cowl with 30 minute epoxy and milled fibre. Be
careful not to glue the cowling on permanently! This tab
makes it easy to locate the cowling in the proper place, so
that the bolts in the bottom line up with the securing M3
blind nuts etc.
The split joint at the bottom of the cowling is reinforced with
the CNC milled plywood parts supplied, glued on with thick
CA, and then reinforced with 30 minute epoxy and milled
fibre. The location of the milled plywood parts should be
clear from the photo here.
When dry the joint in the cowling is held together using 2
strong steel paper clips as shown in the photo. This system
makes it very quick and easy to remove the cowl for motor
access if needed.
The cowl is secured onto the fuselage with two M3 x16mm
bolts into M3 blind nuts in small scrap 3mm plywood
squares at the bottom as shown here. Install the cowling
and secure the joint with the 2 paper-clamps, then drill two
3mm Ø holes from the bottom of the fuselage, through the
moulded groove, into the cowling flange. Glue the blind
nuts into two small (15mm x 15mm) plywood squares, and
glue them onto the inner edge of the cowling with a 30
minute epoxy and micro-balloon mix.
The 6 vacuum-formed grilles (louvres) for the cowling come
pre-painted and trimmed approx. to size from the factory.
However you need to cut out the vertical face behind each
angled blade on the louvres - easily done with a very sharp
X-Acto knife in a couple of hours. It is important not to for-
get this as it allows the cooling air to escape.
Mask each of the 6 pre-cut openings in the fuselage about
5mm (1/4”) outside the cut-out, with masking tape as
shown, scuff up the exposed surface a little with coarse
sandpaper. Prepare the bottom surface edges of the grilles
in the same way and glue the grilles in place with slow CA.
The last photo here shows the completed cowling and
grilles, and you can also see the position of the dual Rx bat-
tery switches. The Ignition battery switch is on the other
side of the fuselage in a similar position. ‘Powerswitches’
were used for both Rx batteries and ignition switches, and
are available as an optional items from C-ARF., and highly
recommended.
15
(above) tape off about 5mm (1/4”)
around grilles and sand to ensure a
good glue bond.
(above) Joining method of the
bottom of the cowling with the
supplied milled plywood parts.
(above) Milled plywood tab glued
to inside of cowling to locate it.

Canopy Frame and Canopy Finished in 3 hours
The canopy frame fits the fuselage already. It is important
to finish the mounts step by step as advised below. The
parts shown in the photo here are from the prototype, and
production versions may look slightly different.
Mill 6 slots (3mm wide x 20mm long) in the canopy frame in
the positions shown, with the outside edge of the slots
approx. 3 - 4 mm inside the outer edge. Then tape the
canopy frame to the fuselage in the correct position, and
mark through all 6 slots onto the fuselage with a felt pen.
Take off the canopy frame and mill the 4 front and back
only in the fuselage, making them about 4.5mm wide
(1.5mm wider towards the centre of the fuselage).
Then mill the 2 middle slots in the fuselage also, but only
3mm wide, so that the 20mm square plywood parts are a
sliding fit in the slots.
Now glue 4 of the 20mm square milled plywood pieces to
the inside of the fuselage directly below the front and back
4 slots, making sure that the inner faces are exactly verti-
cal. Because of the shape of the fuselage you will need to
thicken the epoxy (30 minute type with some milled fibre
and microballoons), especially for the front mounts. Make
sure that these are properly glued in place and that the
space between the plywood plates and fuselage is com-
pletely filled with epoxy.
Drill a 3mm hole through the side of the fuselage in the cen-
tre of the 4 front and rear mounting plates only (not the mid-
dle 2 plates). Take the 4 plywood rectangles with the milled
holes, and glue the four M3 blind nuts in place with 30
minute epoxy. Bolt the 4 plates inside the plywood plates
that are glued inside the fuselage with M3 x 12 bolts, so
that the top of the plates stick up through the milled slots in
the fuselage by 5mm. Cut off excess length if necessary.
Put some clear tape around all 6 slots on the fuselage and
frame and wax these areas carefully, without getting wax
on the plywood plates. Sand the areas around the 6 slots
inside the canopy frame with rough sandpaper. Clamp and
tape the canopy frame in place and then glue the 4 plywood
parts to the canopy frame with 30 minute epoxy and some
milled glassfibre.
Slide in the 2 centre guides (20 x 20mm plywood squares,
no hole) and glue them to the canopy frame with 30 min
epoxy and milled-fibre also. These centre guides just make
sure the middle of the canopy frame stays aligned properly
with the edges of the fuselage.
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16
(above) Milled plywood parts for
the canopy frame fixing.
(below) One of the finished rear
mounting tongues in place.

If the joint area was waxed carefully, you can
take off the canopy frame in about 1 hour.
Fitting the clear canopy into the frame is a lit-
tle bit tricky, but this is a step by step guide of
how to do it successfully:
Sand the inside edges of the canopy frame
carefully with rough sandpaper, to ensure a
perfect fit of the canopy inside. Lay the
canopy on top of the frame, and mark the
rough shape with a felt pen or wax crayon. Cut
the outer border of the clear canopy with
sharp scissors, about 12mm (1/2”) too big all
around. Unless you are in a very warm room,
we recommend that the canopy is slightly
warmed up with a hair dryer to prevent crack-
ing - but be careful not to melt or deform it!
When the canopy fits inside the frame rough-
ly, mark the final cut line on the clear plastic.
Then cut it to exact shape with a 6 mm over-
lap all around.
Make several hand-holds with paper masking tape (see
photo) to make holding and positioning the canopy easy.
Push the canopy up tightly inside the back of the frame and
fix the bottom 2 back corners with one drop of slow CA
each (ZAP-O or Plasti-ZAP recommended).
Note: Do NOT use any CA accelerator/kicker - you will
immediately ‘fog’ the clear canopy!
Tape the front of the canopy to the frame temporarily.
Mount the canopy frame to the fuselage (use all 4 bolts),
and tape the back of the canopy frame tightly to the fuse-
lage. Using the masking 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.
Then make visual check from the front and back to make
sure that the canopy is straight. Now that the canopy is
fixed in position and cannot twist or warp anymore, you can
carefully glue the rest of the canopy firmly in place. You can
either complete the gluing from the outside, allowing the CA
glue to wick into the joint between the frame and the clear
plastic or, if you prefer, 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. Even if you use the CA glue method,
we recommend that you also glue the inside edges with the the epoxy mixture to be sure that
the canopy cannot come off in flight.
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17
(above) Clamp the canopy frame
securely in position while the
epoxy/microballoons mix dries.
(below) Use masking-tape handles
to pull the clear canopy tightly
against the canopy frame while glu-
ing it in position with a few small
drops of thick odourless CA.
CANOPY FRAME FIXING
canopy frame
plywood plate
epoxy glue
plywood plate
M3 blind nut
fuselage side
M3 x 12 bolt

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). Use many very light coats to get even coverage.
Finally the 4 holes for the heads of the M3 bolts that hold
the canopy frame in place need to be ‘counterbored’ into
the outside surface of the fuselage, so that the boltheads
do not squash the relatively soft foam cored vacuum
moulding.
Counterboring means making a larger hole for the bolt-
head to go in, so it sits flush with the outside surface of
the fuselage, and the head sits against a flat surface
inside the hole - not an angled surface like that made with
a normal countersink. The easiest way to do this is with a
Dremel and a small mill. Make the counterbored bored
holes 6mm Ø and about 5mm deep, so that the bolt head
sits against the plywood squares in the fuselage. Even bet-
ter is to glue metal washers into the holes for the bolts to sit
flat against.
Note: This ‘counterboring’ technique also needs to be used
in the bottom surface of both horizontal stabs for the M3
bolts that hold them onto the 20mm aluminium tube.
Horizontal Stabs Finished in 2.5 hours
The stabs are 99% finished at the factory, and only need
the servos, horns and linkages installing. Insert the 20mm
aluminium tube spar into the fuselage sleeve, and install
both stabs to check the fit between the root ribs and the
fuselage. You might have to sand the root of the stabs
slightly to make a perfect joint. If the spar tube is too long
you will have to shorten it a little.
Attach the elevators to each stab using the 4mm aluminium
tubes provided. Be careful inserting the tubes, and if they
are a bit stiff, then use a little grease on the wire. Don’t use
too much force, otherwise some of the phenolic plates
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(above) Finally secure the canopy
to the frame with an epoxy and
microballoons mixture inside.
(below) Counterbore the 4 holes
for the M3 canopy bolts so that the
heads sit against the plywood
plates in the fuselage.
(above) Completed stabs showing
linkage, sleeve for aluminium spar
tube and front anti-rotation pin.

inside might break loose. Leave the tubes a bit long during
construction, and cut them to length later. During final
assembly, retain the ends of the tubes with a small piece of
clear tape at the root and tip ends.
Fit the servos into the stabs in the root rib, and screw in
place using the 2.8mm Ø x 14mm screws we supply in the
kit, instead of the standard screws that come with the ser-
vos. The ribs are milled for a standard sized servo, just
slide the servo in from the root and screw in place. Because
of the thin profile you must install servo arms through the
slots in the bottom of the stab, and you might need to make
the slots 1mm wider when using C-ARF servo arms.
The slots are already milled in the elevators for the eleva-
tor horns, but may be adjusted if required. Put a layer of
clear tape over the area of the milled slot, wax it carefully,
and then cut through the tape with a very sharp knife to
allow the horns to be glued into the slots. This stops the
glue getting on the surface of the elevator.
Make the horn alignment template from thin scrap plywood
(see photo) and mark the position for the quick-link hole in
the horn exactly perpendicular to the hinge axis line on the
tape. The hole should be about 22 - 25 mm from the bot-
tom surface of the elevator. Drill a 1.5 mm Ø hole in the
alignment template, and glue in a short piece of 1.5 mm
wire with a drop of thin CA.
Trial fit the horn in the slot, and make sure that the wire in
the alignment template fits into the hole that is milled in the
horn. Mark the part of the horn that will be glued inside the
elevator, and then remove it and scuff up both sides with
coarse (60 grit) sandpaper or a Permagrit tool. Protect the
template with clear plastic tape so that it does not get glued
to the horn or elevator!
Glue the horn in place with slow epoxy (minimum 30 min.
cure) mixed with milled fibreglass, or a filled thixotropic
epoxy (eg: Loctite/Hysol 9462 or BVM Aeropoxy). Check
that horn is at 90° to the surface of the elevator, and wipe
excess glue off before cure. Repeat for the other elevator
horn, using the same alignment template. This method
makes sure that both surfaces have identical control movements, and a similar method is also
used for the aileron horns.
Servo choice: The elevators can travel more than 50 degrees, and it is up to you whether you
want to use this throw or not. The throw defines the kind of servo. If you are going to use the
maximum throw for 3D manoeuvres, we definitely recommend digital servos like JR8411. It is not
just that the torque of a standard servo is not enough - it is the play in the gears which could
cause problems centering, and high speed flutter might be the result.
When using the powerful digital servos and larger throws we highly recommend that you use our
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19
(above) JR8411 servo fitted into
stab with phenolic C-ARF horn.
(below) Another view of the com-
pleted stabs. Note the position of
the counterbored hole for the stab
retaining bolt, which should have
clear tape over it to prevent it
coming out in flight.
(above) Elevator horn alignment
template from scrap plywood. Line
is hinge axis. Use for both elevators
to ensure same throws. (2.6m Extra
shown)

Composite-ARF phenolic servo arms, designed for this kind
of aircraft and included in the kit. These must be fixed to the
standard (25 mm/1” Ø) plastic output arms supplied with
the servo with 2 small sheet-metal screws each. Rough up
the bottom surface of the C-ARF servo arm and the top
surface of the standard servo arm. With servos installed,
centre the standard servo arms (using your R/C) at 90° to
the btm. surface of the stabs.
Then glue the phenolic C-ARF arms in place with a couple
of drops of thick CA, making sure they are centred on the
servo arm bolt in the shaft and also at 90° to the stab sur-
face. Finally remove them from the servo and secure the
phenolic arms to the standard plastic arms with at least 2 of
the very small (2.2mm Ø x10) sheet metal screws provided
in the kit. Make up the linkages from the 80mm long M3
threaded rods, with 2 quicklinks and 2 x M3 locknuts for
each stab. Don’t forget to ‘Loctite’ the quick-link and lock-
nut on one end of each linkage. Do NOT use ball-links on
the servo arms or the control-surface horns, because they
will twist the servo arm/horn and cause flutter. This is a
solid experience and you should consider it a FACT.
The last job is to fit the M3 stab retaining bolts. Inside the
stabs and you will see the small square plywood reinforce-
ment 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, sleeve and into the 20mm aluminium tube. Thread the hole with an M3 tap and secure it
with an M3 x 16 bolt. To be really safe, you can glue an M3 blind nut inside the stab spar tube,
with some 30 minute epoxy/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, thread as before, and secure with another bolt.
Counterbore the holes in the bottom surface of the stabs for the boltheads so that they fit flush.
Note: Try to always leave the stab tube fixed in one stab, and never remove that one bolt, as it
is very difficult to find the right position for the stab tube again if it is removed from both stabs!
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20
(above) Shows C-ARF servo arm
glued and screwed onto standard
25mm diameter servo output arm.
(below) M3 blind nut glued into
the 20mm Ø elevator spar tube
with epoxy and milled fibre.