Composite-ARF SPARK User manual

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Composite-ARF SPARK
Instruction Manual
Composite-ARF SPARK
TAVS Technology version 1.0

Instructions for SPARK Jet airplane
Thank you very much for purchasing our Composite-ARF Spark all composite jet aircraft, made
with the revolutionary Total Area Vacuum Sandwich (TAVS) technology
If you want a full-color version of this manual, you can download it free from our website as an
Adobe Acrobat .pdf file and print it (paper size A4). Just go to the ‘Spark’ page on our website,
and click on the link named ‘Download Instructions’ above the top photo of the product.
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 your Rep., or 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 CARF-Models Co. Ltd. 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 opera-
tion in any way. Unless otherwise prescribed by binding law, the obligation of the CARF-Models
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 CARF-Models 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 CARF-Models 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.
Composite-ARF SPARK [email protected]
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Important Supplementary Notes
Pre-Flight Checks:
Before every session check that all the model’s 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. Be certain to use the recommended CG position and control surface travels. If
adjustments are required, carry them out before operating the model. Be aware of any instruc-
tions and warnings of other manufacturers, whose product(s) you use to fly this aircraft.
Check very carefully that the flight batteries are securely held into the model, and cannot come
loose during flight maneouvres. Check that the 6mm carbon pins in the front of the the wings and
stabiliser are not loose. Check that the wing and stab retaining bolts are tight, that the canopy
frame is securely held onto the fuselage with the wire from the nose.
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 jet aircraft is a high-end product and can create an enormous risk for both pilot and spec-
tators, if not handled with care, and used according to the instructions. Make sure that you oper-
ate your Spark according to the the laws and regulations governing model flying in the country
of use.
The fan unit (or turbine), servos, R/C equipment, batteries and landing gear have to be attached
properly. Please use only the recommended EDF unit and accessories. Make sure that the
‘Centre of Gravity’ is located in the recommended place. A tail heavy plane, especially in the first
flight, can be an enormous danger for you and all spectators. Fix any weights, and heavy items
like batteries, very securely into the plane. Make sure that the plane is secured properly before
you switch on the Fan unit or start the turbine. Check for vibrations through the whole throttle
range - there should be no vibration at all from an EDF or turbine.
Make sure that you range check your R/C system thoroughly before the 1st flight. It is absolute-
ly 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 fan unit or turbine, run it at about half power and repeat this range check with
the motor running. Make sure that there is no range reduction before ‘fail-safe’ occurs. Only then
make the 1st flight. If the range with motor running is less then with the motor off, please contact
the radio supplier/engine manufacturer and DON’T FLY at that time.
Please read the whole of the this Instruction Manual completely, and make sure
that you understand it all fully, before starting the assembly of your Composite-
ARF ‘Spark’. It will save you time, effort and $$ in the end !
Composite-ARF SPARK [email protected]
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Composite-ARF SPARK [email protected]
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Fully-composite aircraft structure
The fuselage, wing and stabiliser are produced in negative molds, manufactured using vacuum-
bagged sandwich construction technology. Due to very careful design, material selection and
lamination processes the Spark has incredible strength, yet an extremely lightweight airframe.
The 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 or stored by covering the fly-
ing surfaces with the protective padded bags included in the kit, to make sure that none of the
critical parts and linkages are damaged.
All parts are painted in the molds, either single color or designer schemes. A production method
called TAVS (Total Area Vacuum Sandwich), enables us to present this aircraft with incredible
built-in strength, while still being extraordinarily lightweight, and for a price that nobody could
even consider some years ago. This production process has huge advantages, but a few disad-
vantages also. These facts need to be explained in advance for your 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 combination with a
very hard 2 mm foam sandwich to form a hard
and durable outer skin.
The ailerons and speedbrake are hinged, cut
loose and trimmed already for you - laminated
in the mould and attached to the 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 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
means that the hinge axis line is on the top surface of the
wing, not in the centre. This is NOT a disadvantage, if you
program in about 10% NEGATIVE aileron differential in
your transmitter. 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 operated, and the aileron gets a little "bigger" in surface area when mov-
ing up, and "smaller" when moving down.
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, if 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.
Centreline of hinge axis
Phenolic control horn

The Fuselage:
The fuselage is also made in negative moulds; with the main fuselage from composite laminates,
and the vertical fin using TAVS construction. The main internal parts and bulkheads for the fan
unit/turbine mount, nosegear, wing and stabiliser fixings etc are glued in during manufacture, to
ensure accurate location and reduce the assembly time for you. Very careful use of reinforce-
ment at the critical places results in a strong and stiff fuselage, but still extremely lightweight.
The Stabilisers:
The stabiliser is also vacuum bagged sandwiched, and the elevator is elastic-hinged in the same
manner as the ailerons. The horizontal stab is mounted with one Ø 6mm carbon rod at the front
and two M4 bolts at the back, which screw into threaded inserts that are laminated into the fuse-
lage during manufacture.
Tools and Adhesives
Tools etc:
This is a very quick and easy plane to build, not requiring special techniques or 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 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 and 3mm
3. Sharp scissors
4. Pliers (various types)
5. Slotted and Phillips screwdrivers (various sizes)
6. Drills of various sizes
7. Dremel tool (or Proxxon, or similar) with cutting discs, sanding tools and mills.
8. Sandpaper (various grits), or Permagrit sanding tools (high quality).
9. Carpet, bubble wrap or soft cloth to cover your work bench (most important !)
10. Clear Car wax polish (for protecting painted areas close to glue joints).
11. 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. 5 minute-epoxy (highest quality seems to be Z-Poxy)
3. 30 minute epoxy (stressed joints must be glued with 30 min and NOT 5 min epoxy).
4. Epoxy laminating resin (12 - 24 hr cure) with hardener.
5. Microballoons, for adding to slow epoxy for lightweight filling.
We take great care during Production and Quality Control at the factory to ensure that all joints
are properly glued, but recommend that you double-check these yourself and re-glue any that
might just have been missed. If you find any areas that need additional glue, sand and clean the
area carefully first, and re-glue with a thick mixture of slow epoxy and micro-balloons.
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
Composite-ARF SPARK [email protected]
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foam sandwich. It is only necessary to rough up the sur-
face, with 120/180 grit, and clean off any dust with ace-
tone or de-natured alcohol (or similar) before gluing to
make a perfect joint. You should always prepare both
parts to be joined before gluing for the highest strength
joints. Don’t use Acetone or paint ‘thinners’ 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 cig-
arette-lighter fuel, (eg: ‘Ronsonol’ or equivalent). This
does not damage the paint, as Acetone and many other sol-
vents will, and this is what we use at the factory.
At Composite-ARF we try our best to offer you a high quali-
ty kit, with outstanding value-for-money, and as complete as
possible. However, if you feel that some additional or differ-
ent hardware should be included, please feel free to let us
know. We know that even good things can be made better !
Email us: [email protected].
About the Spark (EDF version)
The focus on the design of a high performance electric jet needs to be different than on a tur-
bine powered jet. So CARF came up with a decisive new design, taking electric sport jet per-
formance to a new level. The Composite-ARF Spark.
The Spark is consequently designed as a very lightweight all-composite structure, with fea-
tures similar to a world class F3A-Pattern plane. Lightest lay-ups, perfectly engineered aerody-
namics and structural reinforcements only where they are needed; the Spark is perfectly suited
for electric ducted fan flying (EDF).
We designed our Spark around the Schübeler DS-75 Ducted Fan, developing a static thrust of
approx. 5 kg. Perfect ducting, molded intake lips and carefully calculated exhaust duct make
sure this thrust is used with maximum efficiency to propel the Spark through the air, with an
impressive 1:1 thrust:weight ratio.
The airplane's geometry and airfoils are designed for a very wide speed range at minimum
drag, allowing fast fly-bys as well as precise aerobatics. Landing speeds are very low, due to
the airfoil design and the speed-brake in the center of wing, just below the fuselage.
Our Spark's size is very carefully planned, so that you can fly with the performance of the real
big guys, but can stay with just that slightly smaller fan, that slightly smaller battery, that slightly
smaller motor - which saves you serious money on the one hand, and converts the power of
these just slightly smaller components into breathtaking flight performance.
Of course, as usual, the CARF Spark is highly prefabricated and builds very easily and quickly,
supported by a very detailed instruction manual, which also guides you through the electrical
installation with lots of hints and tips. With a CARF Models Spark you barely can do anything
wrong, whether its your first jet, your first electric, your toy for the weekday evenings, or your
high-performance contest tool.
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Lighter fluid is excellent for clean-
ing small marks, clear wax, uncured
glue, or similar off the painted sur-
face of the plane.

Accessories
This is a list of the things you may need to get your Composite-ARF EDF-powered Spark into
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. DS-75 EDF unit, Lehner 2240-15 motor & 100 Amp speed-controller
We strongly recommend that you use this EDF unit as the Spark is totally designed around
it. It is available as an option from C-ARF, and comes fully wired, balanced and tested -
and packed with the Jeti Spin 99 controller. (Product #864003).
2. Flight batteries. We recommend two 5S Lipo packs of minimum 5000mAH, with maximum
dimensions of 165 x 45 x 60mm, and max. weight 675 grams each. A pair of high-quality
HDHE Lipo packs of 5200mAH is available as an option from C-ARF (Product #865001).
3. Spring-Air 301 ‘Firewall’ retractable landing gear set. The Spark was designed around this
economical, lightweight and reliable gear, and it is available as an option from C-ARF.
(Product #740500)
4. Servos (min. 8). We recommend JR DS3328 or 3301’s for the elevators, ailerons and rud
der. Due to the slim section of the stabiliser it is necessary to use a max.15mm thick servo
with an integral wing-mount bracket. An alternative for the elevators is the JR DS161 or
DS168 servo which also incorporates wing mount brackets. The speedbrake requires a
standard sized servo with minimum 5kg torque (eg: JR 5391 or 8311). We used a JR3341
for the nosegear steering. The retract/brake valve can be controlled with any small servo
of minimum 2kg torque - such as a JR3341 or JR331 micro servo.
5. 5 heavy duty plastic servo output arms (single-sided), for the aileron, elevator and speed-
brake servos. (eg: Graupner # 3544 or JR # 0315)
6. Main and Nose wheels 55 - 60mm (2.25 - 2.5"). You can use any high quality plastic
wheels. An optional set of Behotec ‘slim’ wheels, designed specially for the Spark is avail
able from C-ARF (Product #740550). The set includes 3 dual ball-raced wheels @ 60mm
diameter, 3 bolt-on axles, 2 brake units and a very compact combined retract/brake valve.
7. Receiver battery. We recommend a 2S Lipo of around 1500mAH, as the Spark only draws
about 80 - 100mAH per flight from the small servos.
8. Switch for Receiver battery. We highly recommend the Powerbox Digi-Switch for a 2S 7.4
volt Lipo, or the Powerbox Smart-Switch if using a NiCD or NiMH pack. The Digi-switch is
available from C-ARF as an option (Product # 960610)
9. Charger & balancers for Lipo Flight batteries. (eg: Orbit, Schulze, Graupner, Emcotec etc)
Suitable large cross-section charging cables with Ø 4mm gold connectors.
10. High quality servo extension cables, with gold connectors.
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Building Instructions
General Tips
We recommend that you follow the order of construction shown in this manual, generally start-
ing at the back of the plane and working forward - as it makes access to everything easier and
saves time.
Protect the finished paint on the outside of the model from scratches and dents during building
by covering 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 painted surfaces 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% proper-
ly before adding any additional paint, decals or trim.
When sanding areas inside of the wing or stab to prepare for gluing something onto it, do NOT
sand right through the layer of lightweight glasscloth on the inside foam sandwich! It is only nec-
essary to rough up the surface, with 120 - 180 grit, and wipe off any dust with denatured alcohol
(or similar) before gluing to make a perfect joint. 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.
Don’t use activator (‘kicker’) when applying CA glue to the lightweight foam sandwich structure
of the wing, stabs and fin, or the fibreglass skin of the fuselage, as it can cause the glue to get
hot, and could cause a blemish on the outer painted surface.
Make sure that all bulkheads and parts that you glue into the fuselage are a loose fit (1 - 2mm
gap all around) and glue them in with a mixture of slow epoxy and micro-balloons - otherwise
you may be able to see a mark on the outside of the fuselage.
Be very careful not to add any uneccessary weight in the nose area (EDF version Spark), other-
wise you may need to add lead in the tail to set the Centre of Gravity correctly.
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A view of the complete SPARK kit contents - Product #742000

Rudder
Install the rudder servo and linkage first, so you won’t have
to remove the thrust tube again later. The Fin is very narrow
and it it only possible to fit a servo of up to 15mm (5/8”) thick.
We recommend a digital servo of not less than 4 kg (55
oz/in) torque, for example the JR/Graupner DS3328, 3301
or 3401. If using a servo with an integral wing-mount brack-
et (eg: DS3328) then you can cut, or file, this off.
The servo is mounted inverted, and screwed
onto a pair of small 6mm thick plywood rails
made by gluing two short lengths of the supplied
3mm thick plywood strips together as shown in
the photo. The upper one is normal plywood and
the lower one is liteply. Glue them together with
thin CA, and sand the lengths to fit inside the fin
and against the back face of the fin spar. Secure
the servo using the screws supplied by the servo
manufacturer, with the servo output shaft
towards the back of the plane. Fit a short plastic
servo horn, and centre it with your R/C.
Apply masking tape to the left outside surface of
the Fin, and draw a line exactly at 90 degrees to
the rudder hinge line, in line with the factory-
installed rudder horn. Measure from the back of
the fuselage to the fin spar and then mark this on
the tape, as shown. Using the servo that is
already screwed to the ply mounts you can eas-
ily determine the position of the 25mm long x
5mm high slot to cut for the servo arm. Cut it out
with a sharp knife, and sand to final size.
Lightly sand and clean the inside of the fin where
the servo rails will be glued, and then tack the
complete servo and rails assembly in place with
a little thick CA, aligning the servo arm with the
centre of the slot and the rudder horn. Remove
the servo and reinforce the joints carefully with a
fillet of slow epoxy.
Make up the linkage from the M3 x 60mm
threaded rod, M3 nuts and steel clevises as
shown. The clevise on the linkage needs to be in
the hole that is 13mm (1/2”) from the centre of the servo. Test the servo travel, throws and cen-
tering, loctite one end of the linkage - and then trim and glue the painted plastic fairing over the
front of the linkage with a drop of thick CA. You do not need to scuff the painted surface of the
fin, the CA sticks to it fine !!
Make up the extension lead needed from your servo to the nose area, for RX connection, and
route it down the side of the fuselage now.
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(above) Rudder servo mounting plates must
be securely glued to both skins of the fin, and
also the back of the fin spar, with epoxy.
(below) Rudder linkage can be covered with
the small painted fairing supplied in the kit.

EDF installation
Start the main assembly of the Spark by
installing your EDF (Electric Ducted fan) unit,
and completing the inlet and exhaust ducting.
The inlet ducts have been factory installed for
you, and the clear fibreglass ‘Inlet Joiner’ tube
connects these to the EDF. The milled plywood
fan mounting rails are already installed in the
fuselage.
The Spark is designed around the 115mm (out-
side diameter) Schübeler DS-75 unit, which is
available directly from composite-arf as an
option (Product #864003). The EDF unit comes
with the Lehner motor installed, and the 4-blade
carbon fan attached and balanced, and needs
no work from you - except for attaching the light-
weight molded carbon fan mount to the shroud.
It is very important that the that mount is accu-
rately assembled and glued to the shroud, and
that the completed unit is carefully bolted to the
ply mounting rails to ensure that there is no dis-
tortion of the shroud, which would affect the
clearances between the blade tips and the
shroud.
Lightly sand and clean all 3 pieces of the mount-
ing bracket carefully, using 400 grit paper, or
better is green Scotchbrite. Assemble the 3 car-
bon parts as shown, exactly at 90 degrees to
each other. Tack together with a very little thin
CA, working on a waxed plastic/glass sheet so
you don’t glue the mount to the table!
IMPORTANT: The 2 carbon mounting tabs that
will be bolted to the ply mounting rails in the
fuselage must be positioned in line with 2 oppo-
site carbon stators in the shroud, as shown in
the photo on the next page. The back edge of
the tabs should be positioned 6 - 7mm from the
back edge of the shroud - NOT flush with the
back of the shroud as shown in the instructions
that come with the Fan unit.
Mask off the area where the mount will be glued
to the shroud, very lightly scuff the gluing areas,
and clean off all dust carefully. Tack glue the
mount to the shroud with 2 or 3 small drops of
thin CA and check alignment. When satisfied
glue the joints fully with a little thin CA, and then
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(top) Schübeler DS-75 EDF unit comes fully
assembled, balanced, wired and tested.
(above) Assemble the fan mount with thin
CA, working on a plastic sheet or waxed glass.
(below) Mask off shroud and scuff with green
Scotchbrite for good glue adhesion.
(btm) The back edge of the fan mount should
be 6 - 7mm from back edge of shroud.
6 - 7mm