Composite-ARF SPARK

Composite-ARF SPARK
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Instruction Manual
Composite-ARF SPARK
TAVS Technology
version 1.0
Composite-ARF SPARK
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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:
or
Telephone:
Website:
[email protected]
[email protected]
Phone your C-ARF Rep!!! He will be there for you.
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 operation 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.
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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 instructions 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 spectators, if not handled with care, and used according to the instructions. Make sure that you operate 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 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 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 CompositeARF ‘Spark’. It will save you time, effort and $$ in the end !
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Fully-composite aircraft structure
The fuselage, wing and stabiliser are produced in negative molds, manufactured using vacuumbagged 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 flying 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 disadvantages 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.
Centreline of hinge axis
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
Phenolic control horn
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 moving 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.
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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 reinforcement 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 fuselage 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.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Sharp knife (X-Acto or similar)
Allen key set (metric) 2.5mm and 3mm
Sharp scissors
Pliers (various types)
Slotted and Phillips screwdrivers (various sizes)
Drills of various sizes
Dremel tool (or Proxxon, or similar) with cutting discs, sanding tools and mills.
Sandpaper (various grits), or Permagrit sanding tools (high quality).
Carpet, bubble wrap or soft cloth to cover your work bench (most important !)
Clear Car wax polish (for protecting painted areas close to glue joints).
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.
2.
3.
4.
5.
CA-Glue ‘Thin’ and ‘Thick’ types. We recommend ZAP, as this is a very high quality.
5 minute-epoxy (highest quality seems to be Z-Poxy)
30 minute epoxy (stressed joints must be glued with 30 min and NOT 5 min epoxy).
Epoxy laminating resin (12 - 24 hr cure) with hardener.
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
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foam sandwich. It is only necessary to rough up the surface, with 120/180 grit, and clean off any dust with acetone 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 cigarette-lighter fuel, (eg: ‘Ronsonol’ or equivalent). This
does not damage the paint, as Acetone and many other sol- Lighter fluid is excellent for cleaning small marks, clear wax, uncured
vents will, and this is what we use at the factory.
glue, or similar off the painted surAt Composite-ARF we try our best to offer you a high quali- face of the plane.
ty 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. 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 turbine powered jet. So CARF came up with a decisive new design, taking electric sport jet performance to a new level. The Composite-ARF Spark.
The Spark is consequently designed as a very lightweight all-composite structure, with features similar to a world class F3A-Pattern plane. Lightest lay-ups, perfectly engineered aerodynamics 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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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 speedbrake 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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A view of the complete SPARK kit contents - Product #742000
Building Instructions
General Tips
We recommend that you follow the order of construction shown in this manual, generally starting 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% properly 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 necessary 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), otherwise you may need to add lead in the tail to set the Centre of Gravity correctly.
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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 bracket (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 factoryinstalled 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 easily 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.
(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.
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 centering, 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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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 (outside 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 lightweight molded carbon fan mount to the shroud.
It is very important that the that mount is accurately 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 distortion of the shroud, which would affect the
clearances between the blade tips and the
shroud.
(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.
Lightly sand and clean all 3 pieces of the mount- (btm) The back edge of the fan mount should
ing bracket carefully, using 400 grit paper, or be 6 - 7mm from back edge of shroud.
better is green Scotchbrite. Assemble the 3 carbon 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 opposite 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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6 - 7mm
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reinforce with a small bead of medium CA. Do
NOT use any activator/kicker or the CA glue and
shroud will turn white and ugly, and the heat produced could even deform the shroud.
Now take the clear fiberglass inlet joiner and
sand the front and back flanges to 10mm wide.
Trial install the inlet joiner over the back of the
inlets and check for a smooth fit. The joining
flange should be at the top, on the fuselage centreline, and you can sand this flange down to
about 6mm high everywhere. Also check that
the back of the inlet joiner fits smoothly over the
front of the fan shroud, and sand it a little if necessary.
(above) The carbon fan mounting tabs should
be positioned opposite to 2 of the stators.
(below) A step-by-step view of how to insert
the EDF unit and inlet joiner into the fuselage.
With the fuselage upside down, place the fan
right at the back of the plywood mounting rails
and tilt it upwards about 30 degrees as shown,
and then slide the inlet joiner over it. Then you
can push both parts down and forward together,
until the inlet joiner fits over the back of the
inlets. If necessary you can reduce the width of
the flange on the front of the inlet joiner to 5 or
6mm allow easier fitting.
Step 1
Check carefully that the 2 carbon fan mounts sit
completely flush on the plywood mounting rails,
and cannot distort the shroud when they are
bolted down. If there is any small gap under the
mounts then you must pack this out with a shim
made from thin plywood or plastic sheet.
Step 2
With the fan unit and inlet joiner in their final
position, carefully mark the 4 mounting hole
positions, remove the fan and drill the holes Ø
4.5mm. Fit four M3 T-nuts under the ply mounting rails and hold in place with a drop of 5 minute
epoxy while you re-install the fan unit and tighten the M3 x 12mm allen bolts (with washers) to
set perfect alignment. The fan shroud should not
touch the plywood mounting rails at any position. The inner edges of the T-nuts project inside
the mounting rails a little, and can be ground off
afterwards.
Step 3
Thrust tube
The thrust tube is made from very thin mylar sheet, and there are 2 sheets included in the kit,
already cut to shape - to allow you to make a spare tube if necessary. The front should slide tightly over the outside of the fan shroud (Ø 115mm), and the back should be approx. 89mm diameter. During prototype flight testing we tried many different diameters of thrust tube outlet, but
89mm proved the best compromise between static and dynamic thrust with the Schübeler DS-
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75 EDF unit. The tube should be joined using
contact adhesive at the overlap, and also a
length of clear tape on both the inside and outside surfaces of the overlapping joint.
Make up the jig used to join the thrust tube using
the 2 milled plywood discs included in the wood
pack. The front disc is 115.25mm diameter, and
the rear disc is 89mm. There is a 12mm diameter hole milled centrally in each disc. Join them
using a straight length of suitable tube (wood,
fibreglass etc) of at least 12mm (1/2”) diameter,
spaced apart at 560m (22”). Tack glue a balsa
sheet stiffener onto one side, as shown, to provide a straight edge for the 20mm wide overlap
of the mylar sheet where you will glue and tape
it together.
Very lightly sand and clean the overlapping parts
of the mylar with 400 grit sandpaper, to provide
a good key for the contact-adhesive. We used
‘Zap-a-dap-a-Goo’ to join all the tubes of the prototypes, and this works very well indeed. Apply a
very thin layer to both surfaces at the overlap,
wait until they are dry to the touch (2 - 4 minutes), and then join together with the mylar
sheet wrapped tightly around the jig. With the
tube still on the jig apply 1 piece of strong clear
tape along the overlapping joint for the whole
length of the tube. Before removing the tube
from the jig, mark both ends at the position of the
wood discs with a permanent marker - to give
you a guide line for final trimming later. Slide the
tube off the jig and apply another length of clear
tape on the inside of the overlapping joint.
Trim the front of the thrust tube so that it slides
over the fan shroud by about 12mm. You will
need to make 2 small ‘U-shaped’ notches in the
front edge of the thrust tube, as shown, 180
degrees apart, to locate over the carbon fan
mounts. It is easier to install the thrust tube if
you leave the front edge a bit longer on the
upper side of the shroud than on the bottom, and
make sure there are no sharp corners.
Cut an oval hole in the top surface of the tube,
approx. 25mm behind the back of the shroud, for
the 3 motor wires to exit. Protect the wires by
inserting one of the large grommets included in
the hardware bag, secured with thin CA.
Now slide the thrust-tube into the fuselage,
12
(above) 2 cnc-milled ply discs of 89 and
115mm diameter are included, together with
2 sheets of mylar sheet to make thrust tubes.
(below) Glue the 2 discs onto any suitable Ø
12mm tube or rod, and make at least 1 brace
with 10mm thick balsa to support the overlap
joint while gluing and taping it together.
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install the fan unit and slide the front of the tube
over the shroud into the final position - so that
you can mark and cut the outlet end so that it is
flush with the back of the fuselage.
The thrust tube should clear the fibreglass cloth
that attaches the stab bolt insert nuts by 3 4mm, but if there is any interference you can
sand away the underside of the fibreglass without any risk (see arrow on photo right).
The thrust tube should be clear of the curved
section at the bottom of the Fin spar by 2 or 3
mm, but if necessary you can sand it a little for
clearance.
During final assembly the inlet joiner and the
thrust tube are secured to the fan shroud with a
piece of duct tape, or similar.
Note: It is quite easy to insert the thrust tube
from the back of the fuselage during normal
maintenance etc. Just use a length of round rod,
or tube, to squeeze the tube into an ‘omega’
shape, and then you can pull the sides together
into a ‘U’ shape, and insert it. Push in with the
tube on the opposite side from the glued and
taped joint of the thrust-tube, so that you don’t
stress it unduly. (see diagram right)
Use tube to push mylar into a ‘U’ shape,
on opposite side to joint.
mylar thrust tube
Clear tape both sides of overlap joint
(right) The Schübeler DS-75
EDF unit installed, secured
with four M3 x 12 allen bolts
into T-nuts under the mounting rails - also with the inlet
joiner and thrust tube in
place. You can also see the
plywood tongue and T-nut
that the single M4 wing fixing
bolt screws into here, which
is factory-installed for you.
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Horizontal Stabiliser
The one-piece stab is factory-finished for you. It
is secured to the fuselage by a 6mm carbon
dowel at the front, that fits into an 8mm carbon
tube in the fuselage, and a pair of M4 Allen bolts
at the back - which screw into threaded metal
inserts that have been laminated to the fuselage
sides. The phenolic control horns are glued in
place, and jig-aligned, and even the cutouts for
the servos are started to save you a little time.
The stabiliser is quite thin and will only accept a
15mm thick ‘wing-mount type’ servo if you want
it to fit completely flush. The servo should have
at least 4 kg torque and a strong, slop-free, gear
train. Therefore we also highly recommend the
Graupner/JR DS 3328/3301 for this application.
Make up the servo mounts from 2 layers of the
milled 3mm Liteply pieces, with a layer of the
1.5mm thick ply strip glued to the bottom if necessary to match to exact height of your servos.
Laminate them all together with thin CA, and
then file the slot thru’ the 1.5mm ply (if used) to
make sure the servo fits absolutely flush against
the upper skin of the stab. Sand a small groove
in the top of the mounts for the servo extension
cable exit. Screw the wing-mount brackets of the
servos to the mounts using the small Ø 2.2 x
10mm sheetmetal screws supplied in the hardware packs, and sand off any excess that comes
thru’ the top surface of the mounts. Then remove
the screws and apply 1 very small drop of thin
CA to all of the screw holes - which will harden
the wood around the edges of the hole to give a
more secure fixing. Use this technique on all
screw fixings into Liteply throughout the plane.
(above) Shape the servo mounts to fit against
the rear spar in the stab.
(below) Align servo output arm carefully with
the phenolic elevator horn, parallel to the
fuselage centreline.
Note: The aileron servo mounts are made up in
exactly the same way, if you are also using JR
DS3328 or 3301 wing-mount type servos.
Fit a JR heavy duty servo arm to each servo,
and centre them now with your R/C so that they
will be at 90 degrees to the bottom surface of the
stab. Apply masking tape to the bottom surface
of the stab and mark on the lines of the linkages,
in line with the elevator horns and exactly parallel to the fuselage centreline.
There are factory-made cutouts in the underside of the stab for the servos, but these will proba-
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bly need to be enlarged a little, depending on
your servo choice. Do not cut through the carbon rovings on the top and bottom edges of the
balsa spars if you enlarge these servo hatches.
Sand the front edge of the forward servo mount
so that it is only 4 - 5mm wider than the servo,
so that the servo is positioned as far forward as
possible in the stab, where the profile is thickest.
Check for a good fit against the back of the forward spar. Then mark where the back mount
needs to be sanded at an acute angle to clear
the rear spar, and sand it to fit also. Check that
the servo output arm is exactly in line with the
fuselage centreline and elevator horns.
(above) The servo cables exit close to the
side of the fuselage, thru’ plastic grommets.
(below) The servos are covered with the prepainted fibreglass sheet included, secured
with clear tape as shown here.
Carefully prepare the inside
surface of the foam sandwich
for gluing, by sanding lightly
with 120 grit and cleaning off
any dust with a little Acetone or
equivalent (eg: Lighter fuel).
Glue the complete servo
mount assemblies into the
stab using a little slow epoxy
and micro-balloon mixture being careful not to use too
much or you will glue the servos in also! When cured,
remove the servos and reinforce all joints with a small fillet
of epoxy.
Run the 2 short servo extension cables out thru’ the top surface of the stab, just inside the edges
of the fuselage, using the 6mm rubber grommets supplied. Open them up with needle-nosed pliers to get the connectors through them. Make up the linkages from the M3 x 60mm threaded
rod, M3 nuts and steel clevises as shown. Test the servo travel, throws and centering, not forgetting to add a drop of Loctite to one end. The clevise on the linkage needs to be in the hole
that is 16mm (5/8”) from the centre of the servo.
Cut the servo covers from the painted fibreglass sheets supplied in the kit, and secure them to
the stab surface with clear tape as shown.
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 to the nose area now.
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Wing
The wing is also 99% factory-completed for you.
All wing fixings are completed, phenolic aileron
horns are jig-installed, and the elastic-hinged
speedbrake is already cut out in the front of the
wing centre-section. Strong laminated plywood
landing gear mounts are installed during the
molding process, and carefully integrated with
the wing structure.
The cutouts for the retractable landing gear and
aileron servos have been made at the factory for
you, also to facilitate our Structural QC inspections, but you may need to enlarge them slightly
by trimming or sanding the edges to suit your
choice of gear.
The wing is fixed to the fuselage with a pair of
6mm diameter carbon dowels at the front, which
fit into carbon tubes in the fuselage, and a single
M4 x 20 allen bolt at the back that passes thru’
a 6mm thick ply tab in the fuselage and into an
M4 T-nut. The wing fixings are totally completed
(above/below) Shape the front servo mount
at the factory for you.
to fit against the spar. Glue securely to the
wing skin, spar and plywood rib with epoxy.
Ailerons
The wing is thick enough to install full-size servos, but it is not necessary on this EDF jet, and
would only add weight, cost and increase the
current drain on the receiver battery.
6 -7mm
We highly recommend that you chose similar
servos to the elevators, of at least 4kg (55
oz/inch) torque, such as the JR/Graupner 3328
or 3301’s - and the wing-mount servo type
makes installation easy also. You could fit any
‘normal-mount’ mini-servo (eg: JR3401), but
then you will have to modify the servo mounting
slightly as shown on the next page.
(below) Completed aileron linkage shown.
Install the 2 aileron servos first, making up the
servo mounts from the milled plywood parts and
1.5mm strip in the same way as the elevator servos. This time it is the front face of the front
servo mounts that need to be sanded at an
angle to match the back of the main spar, keeping the servo output arm exactly in line with the
aileron horn, and parallel to the fuselage centreline. Keep the servo bracket at least 6mm back
from the spar to make sure that the servo arms
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don’t hit the spar at 45° throw.
If you chose to fit servos without integral wingmount brackets, you can just add a couple of
extra milled liteply pieces to increase the mount
height to flush with the top of the servo, and then
secure using the small screws thru’ a small strip
of the 1.5mm plywood (see photos right).
Fit a heavy duty servo arm to each servo, and
centre them now with your R/C so that they will
be close to 90 degrees to the bottom surface of (above/below) Alternative mounting method
for servos without integral ‘wing mount’ lugs.
the wing.
Prepare the surfaces for gluing by sanding and
cleaning, and glue the complete servo and
mount assemblies into the wing with a little slow
epoxy and micro-balloons mixture, firmly against
the main spar and also against the plywood rib
that is on the outside of the landing gear mount.
When cured, remove the servos and then reinforce all the joints with a small fillet of epoxy.
The servos will need extension cables of about
275mm (11”), so that they can pass through one
of the milled cutouts in the main spar, and then
to the centre section of the wing, and finally into
the fuselage for approx 125 mm. Tape the extension cables and connectors in place so that they
cannot come loose, or foul the aileron linkages.
Carefully drill and file the slots in the bottom
wing surface, just behind the servo cutouts, for
the pushrods to exit and connect to the aileron
horns. Make up the aileron linkages from the
hardware supplied, using M3 x 65mm all-threaded rods, M3 nuts and steel clevises. Loctite the
clevise onto the aileron end of the linkage after
you have set up you have set up your linkages
and throws, as this removes the need for an M3
locking nut here - which would need a much bigger slot in the wing for clearance.
After the landing gear is completed, the retract
units and aileron servos are covered using the
thin painted fibreglass sheet supplied in the kit,
fixed with clear tape, in the same manner as for
the Stabilisers.
Speedbrake
The speedbrake is elastic-hinged in the laminating process, and is already cut free for you. It is
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Hinge Axis
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very effective, and is needed on landing as the
specially designed wing profile for the Spark has
extremely low drag at high loads - and the plane
tends to float on and on if you don’t use it.
However, that fact is very useful to know if you
run out of power during a flight and need to glide
back to the strip ! In production kits the speedbrake is 10mm deeper than shown here.
Open the speedbrake and mark a centreline on
it, for attaching the phenolic horn. Scuff the area
on the centreline and the gluing area on the phenolic horn, and tack glue the horn to the speedbrake with just 2 very small drops of thin CA, as
shown. Note that the small milled notch in the
bottom of the horn should be in line with the
hinge axis! When the speedbrake assembly is
completed, and the throws checked, you must
reinforce the joint between the phenolic horn
and the speedbrake with a good fillet of 30 (above) Shape the balsa strips on the botminute epoxy and micro-balloons.
tom of the mount to fit the curved wing skin.
(below) View of the open speedbrake, also
Cut 3 pieces of the narrow clear fibreglass strip showing servo extension cables and Rx antenand glue them inside the lower wing skin on the na (yellow) extension in the wing.
back and sides of the speedbrake opening to
form a 3 - 4mm wide lip. Sand the fibreglass
strip, and inside the wing, carefully and glue the
strips in place with a little thin CA. Make sure
you don’t deform the shape of the wing while
doing this.
The speedbrake is designed to be controlled by
a standard sized servo of minimum 5kg torque.
If you are using JR servos then items such as
DS5391, 5491, 8231, or 8311 are suitable. The
servo should be mounted onto the milled composite plywood-fibreglass plate, using the 2 aluminum angle brackets and M3 bolts supplied,
and then the complete assembly is glued into
the wing - against the upper surface of the wing.
It is possible to remove the servo for maintenance, but it is quite tricky and needs a small
hole making in the wing center section for allen
key access - so we recommend that you doublecheck the installation and servo centering carefully before gluing it into position.
First secure the servo, loosely, to the 2 aluminium brackets using the M3 x 12mm allen bolts
and washers as shown, into the threaded holes.
Then secure the 2 angles to the milled plywood
plate, from the underside, using the M3 x 8mm
button-head bolts. Tighten these firmly first, and
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then tighten the 4 bolts that secure the servo.
Because of the curved shape of the upper wing
skin in this area you need to glue a couple of 5
x 5mm balsa strips to the bottom of the ply plate
and sand them to fit the wing skin, as shown in
the photos. Fit a heavy duty JR servo arm to the
servo and centre it using your R/C. Make up the
linkage as shown, using the M3 x 40mm allthread, steel clevises and M3 nuts. Loctite the
clevise that will be clipped onto to the servo arm
now. The clevise on the linkage at the servo end
usually needs to go on the outer hole of the
servo arm, 20mm out from the servo centre.
(above) A small hole allows access to rear
servo bolts with a long ball-driver if necessary.
(below) Wing is fixed to fuselage by a pair of
6mm carbon pins at the front. Wrap the servo
extension leads & air tubes together to make
Adjust the linkage carefully so that the servo arm it easier to insert them into the fuselage cable
does not go ‘over-centre’ when the speedbrake duct when fitting the wing for flying.
is closed, and make it difficult to open it by hand
to make the Rx antenna connection when
assembling the plane.
You can make small semi-circular ‘finger-hole’
cut-out in the wing skin behind the speedbrake
to make it easy to open it when assembling the
model at the airfield. (see photo below/right )
Main Landing Gear
The Spark was designed to use low-cost, lightweight and reliable retractable landing gear, and
the Spring Air 301’s fit this specification perfectly. They were used in both prototypes without
any problems at all; one set was fitted with lightweight plastic wheels, and the other with the
optional 60mm Behotec ‘slim’ aluminum wheels
and brakes especially designed for the Spark. (below) View of Landing gear installed.
It is your choice what to fit, but of course the
plastic wheels (without brakes) are more than
adequate for grass airfields - whereas the
Behotec wheels and brakes will be more suitable and durable for hard runways. Both wheel
types were fitted to the standard Ø 4mm wire
legs supplied with the Spring Air set. The Spring
Air 301 ‘Firewall set’ and the Behotec wheels &
brake set are both available from CompositeARF as options.
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The main retract units should be secured to the
integral plywood mounts using the M3 x 12mm
allen bolts and T-nuts supplied, in the usual way.
You can trim the bottom wing skin a little more
around the retract openings, if necessary, to get
them into position. Use a straight edge to make
sure that both units are exactly in line with each
other, and also centred on the cutouts in the
wing skin that are already made for the wheels
(which can be enlarged a little as needed).
Fit the retracts as outboard as possible, to give
the maximum leg length - and therefore the
biggest rotation angle before the stabiliser tips
touch the runway. For the same reason, only
leave a minimum of 10 - 13mm space between
the retracted wheels in the centre of the wing.
(above) The Spring-Air 301 ‘Firewall’ retract
set fits the Spark perfectly and is available as
an option directly from Composite-ARF.
(below) The optional Behotec ‘slim’ wheel &
brake set also includes 3 bolt-on axles and a
compact combined retract/brake valve that is
Drill Ø 3mm through one of the mounting holes designed for air-in/spring-out systems. Wheels
in the retract unit, and insert one of the M3 x 12 are 60mm Ø and double ball-raced.
allen bolts to hold it in position. Then drill the
other 3 holes, also inserting a bolt to keep the
correct alignment after each hole is drilled.
Remove the retract unit and open up all the
holes to Ø 4.5mm for the M3 T-nuts. Using a M3
bolt and a large washer, pull the spikes of each
T-nut into the top surface of the mounting rails
just a little, with a drop of 30 minute epoxy on
each. Re-install the retracts and tighten all four
bolts, which will make sure that the T-nuts are
perfectly aligned when the glue has cured.
Fit the Ø 4mm wire legs to the retracts, with the
coils oriented as shown in the photo here. Only
file a very small flat spot on the legs for the set
screw to sit against. Make a small semi-circular
cutout behind each leg to accommodate the coil
when the legs are retracted.
If you chose to install plastic wheels, then you
need to bend the legs to form the axles in the
usual way, solder a Ø 4mm washer to the leg on
the inside of the wheel, and secure the outside
with a Ø 4mm wheel collar, or similar. Note that (above) Maintain at least 10mm of wing skin
the wheels are fitted on the outside of the legs, between the 2 main wheel wells. Balsa scraps
and are completely hidden in the central section used to retain tubes are seen here.
of the wing when retracted.
If you have the optional Behotec aluminum wheels and brakes, then proceed as follows:
Clean the wire legs well with green Scotchbrite or fine sandpaper in the approx. position that the
axles will be fitted, and degrease both parts using Acetone or equivalent. Fit the bolt-on axles to
the legs loosely, and slide the brake units onto these, followed by the short Ø 6mm aluminum
tube spacer included, and then the wheels and finally the ‘E-clip’ that retains the wheels onto the
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axles. Retract the legs to check for the exact
position that the axles need to be secured to the
legs, and then tighten the set screws in the ends
of the axles.
Remove the legs from the retract units and also
the wheels and brake units. Now solder the
axles in position using quality soft solder and
non-acid flux; even better is a low-temperature
silver solder that can be used with an electrical (above) Order of assembly of Behotec wheels
soldering iron (eg: Stay-Brite).
and brakes. Don’t forget the spacer tubes!
(below) Ø 6mm steel axles are bolted on,
Fit the brakes with the nipples to the rear of the and then soldered to the Ø 4mm wire legs
wheels, tape the air tube to the wire legs, and
run it through the coil in the wire leg at the bottom so that it cannot get ‘kinked’ during retract
operation. You can use some small scraps of the
5 x 5mm balsa strip to secure the retract tubing
inside the wheel wells, to make sure it cannot
get caught during operation.
When finally installing the main legs and wheels,
set a little bit of ‘toe-in’ on both, about 1 degree
or so, for best ground tracking and handling.
Servo and retracts
covers are made in
same way as for the
stab; cut them from
the thin painted fibreglass sheet included,
and tape them onto
the wing using clear
tape (eg: TESA)
Collect the extension
cables
from
the
aileron and speedbrake servos with the
retract/brake air lines,
and route them thru’ a
plastic
grommet
glued into a hole on
the center-section of
the wing.
They all need to extend into the fuselage for 125 - 150mm (5 - 6”) and can be bundled together
in a length of ‘spiral-wrap’ to make it easier to pass them into the fuselage area when assembling the plane at the field.
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Cockpit Canopy
The fibreglass canopy frame has already been trimmed at
the factory, and the fixings completed. The front is secured
with a wire through a plastic tube from the nose, the upper
back end with a small plywood tongue, and the sides are
aligned with 2 small phenolic tabs into slots in the cockpit
flange. You can add another pair of very small tabs at the
lower back corners, using the phenolic strip included, if you
wish. Cut the 2mm wire to length, sand it smooth, and solder the brass ball from the plastic ball-link (in the hardware)
onto the end of the wire. Mill a small countersink in the nose
for the ball to sit in. This method makes it quick and easy to
get the canopy off, and does not require any tools on the
field.
Fitting the clear canopy is quite simple, as it is small and
rigid. However the fibreglass
(below) Tape handles on the canopy are used to pull it into
canopy frame is extremely
place while tack gluing in 6 places with odourless CA.
lightweight, and you need to
be careful not to deform it
when gluing in the canopy. You
can use your own favourite
method and glue if you wish,
but here is how we do it.
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 and a good gluing surface. Fit the canopy frame on
the fuselage and secure it with
the wire, and masking tape all around. Trim the clear canopy very roughly to size so that it is bigger than the edges of the cutout in the canopy frame all around. There is a faint ‘cut line’ molded into the clear canopies to guide you, but you definitely need to cut at least 6mm outside that
line to begin with.
Lay the canopy on top of the frame, and view from the front and back to check that it is centred.
Trim as necessary. When the canopy fits inside the frame, tape it into position temporarily, check
alignment, and then accurately mark the edge of the frame on the canopy with a wax crayon.
Remove the canopy and trim exactly to shape, leaving only a 6mm overlap outside the line.
Unless you are in a 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!
With the canopy frame still secured to the fuselage, tack the canopy into position with a couple
of very small drops of ‘odourless’ CA, at the back and front lower corners. Make some ‘handles’
from strong tape (see photo) to allow you to ‘pull’ the canopy in position while you do this. Apply
the glue to the inside of the fibreglass canopy frame (not the clear canopy) and then use the tape
‘handles’ to pull the canopy out against the frame into the correct position.
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When the canopy is tacked into the frame, and it
cannot twist any more, you can carefully remove
the compete canopy frame and secure the
inside edge of the clear canopy with a small
bead of slow (24hr) epoxy and microballoons.
Alternatively you can use a specialist canopy
glue that dries clear and bonds well the the clear
plastic. Whichever method you chose, make
sure to secure the canopy frame in it’s final position on the fuselage while the glue dries to
ensure that nothing can deform.
(below) Clear canopy is trapped in place with
epoxy/micro-balloons mixture. Also note the
short tube that accepts the nose fixing wire.
Make sure that this is securely glued in place !
* Please see page 29 of these instructions for
details of cutting the cooling inlet slots and
installing the baffle for the speed-controller.
Fuselage
We recommend that you complete the remainder of the fuselage assembly and R/C installation in the order shown below.
Cable Duct:
(above) Cable duct in fuselage is lined with
split silicone tube to protect extension wires
and air lines from sharp edges.
(below) Correct assembly of the Spring-Air
301 firewall mount noseleg unit.
Make the route for the extension leads and air
tubes from the wing by trimming away the flanges on the
inside of the inlet ducts, behind the plywood bulkhead - leaving approx. 5mm width for strength, and protecting the
edges. Split the length of silicone tube (included in the hardware) with a sharp knife, and glue it on to the remaining narrow flange with a little thin CA, as shown here.
Nosegear
The factory-installed nosegear bulkhead is 6mm thick laminated aircraft-grade plywood, with the mounting holes predrilled and the M3 T-nuts glued to the front face of it. The
hole centres match the Spring-Air 301 series ‘Firewall’
mount, and if you chose to fit a different retract unit then you
will need to push out the T-nuts and redrill to suit the mounting centres of your nose unit.
Assemble the nose retract unit as shown, with the steering
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arm on the right side. File only a very small ‘flat’
for the set screws in the wheel collars (in the
trunion block and steering arm) to grip onto, otherwise you will weaken the wire leg. Make sure
that the plastic bracket slides up and down the
steering arm smoothly.
Install the retract onto the bulkhead. Fit the wing
onto the fuselage, with the main gear extended,
and set the plane on a level surface to set the
length of the nose gear leg. It is preferable to
have a little positive angle (+0.5 - 1 degree) on
the wing root, especially if flying from grass
strips, and we suggest that you make the noseleg 4 - 5mm longer than the length required for
0 degree wing incidence.
We also recommend that you bend the noseleg
back a little, at about a 5 degree angle, at about
35mm (1.5”) above the axle position. This not
only improves the steering, but also makes sure
that larger wheels retract completely into the
fuselage.
(above) Spring-Air 301 ‘firewall’ retract bolted
to the 6mm ply factory-installed bulkhead
with the M3 allen bolts and T-nuts.
(below) Bend the nose leg back about 5 7mm, starting just above the wheel, for
improved ground handling.
If using plastic wheels, then bend the wire leg to
form the axle for the wheel in the usual way.
If you are fitting the optional Behotec wheels,
then secure the axle to the leg and solder it on
as described in the wing section. There are 2
very short Ø 6mm aluminum tube spacers in the
set that must be fitted on either side of the wheel
hub to centre it on the axle.
The steering servo installation is described at
the end of this section, as it must be installed
after the battery support bulkhead is completed.
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approx. 128mm
approx. 65mm
5 - 7mm
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Speed-Controller
The ‘Jeti Spin 99’ Speed-controller is mounted
right at the back of the cockpit as shown, on top
of the ducting, and it is also used to secure the
fibreglass Inlet joiner to the inlets, as the inlet
joiner is not glued into the plane.
Please read the ‘Cooling’ section later in this
manual before installing the speed-controller, as
it might affect the exact mounting of it - depending on the ambient temperatures that you will
operate your Spark in.
Make up the 3 small 6mm thick mounting blocks by gluing short lengths of the 3mm Liteply strip
together with thin CA, and sand to shape to fit on the ducts. Secure the controller to the 3 blocks
using the 2.9 x 10mm sheetmetal screws thru’ the rubber mounting grommets.
Sand the gluing areas on both duct parts, and then glue the complete assembly in place using
30 minute epoxy and micro-balloon mixture, keeping it exactly central in the cockpit opening. Of
course you should have the fan unit installed and fixed in position while you do this to ensure
correct alignment of the Inlet joiner. See photos on page 28 and 29.
* Please see the ‘Cooling’ section on page 27, 28 and 29 for details of the air vents and cutouts
needed for cooling the speed-controller.
Flight Battery Installation
The Lipo Flight batteries are the
heaviest item in the plane, and
must be fixed very securely, as
they will weigh several times their
actual weight under ‘G’ forces.
This EDF system used is
designed to use a pair of 5S
packs of approx. 5200 mAH, as
shown here, and these are available from us as an option (product
#865001). Of course you can
choose your own packs, which
might be a different size or shape
to the ones shown - and in that
case we advise you to follow the
basic design principle shown here
if you make your own battery tray
and supports.
The 5200 mAH packs shown (above) View of the completed dual Lipo Flight battery
weigh 660 grams each and, when installation. The 2 wires with yellow heatshrink on them are
positioned as shown, the Centre joined together to ‘arm’ the system ready for flight.
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of Gravity location is almost perfect, only need- (below) Rear battery support bulkhead is facing the small RX battery for final adjustment. If tory-installed. The battery tray has a milled tab
fitting your own larger packs it is important to that fits in the central slot, arrowed here.
position them as far back as possible in the nose
area, to maintain the correct CG without having
to add weight in the tail.
The following instructions assume that you are
using a pair of packs of maximum size 165mm
long, 45mm wide and 55mm high, which can be
fitted onto the milled parts supplied in the kit
without any modifications.
Lightly sand the battery tray and make sure that
the small tab on the tapered end of it fits easily
into the milled slot in the rear bulkhead, which is
factory installed for you. In case you need to
reposition the slot in this bulkhead to suit different shape Lipo packs we have included a small
ply plate with milled slot in it, that you can use a
‘doubler’ if necessary on the new slot position.
Glue 4 strips of the 5 x 5mm balsa onto the top
and bottom of the battery tray where your packs
will be, with thin CA, to maintain the air gap all
around the packs. They also stiffen the battery
tray considerably. Secure your packs onto the
tray using the double-sided Velcro band supplied, with the connection wires at the rear end.
Do not secure the Lipos to the tray with cableties, because the high pressure can damage
them. Of course you can modify the battery trays
a little to suit the shape and size of your packs,
and we have included 2 in the wood pack.
Assemble the front support bulkhead from the
milled ply parts as shown in the photo, and just
tack together with a little thin CA. Check that
your nose gear steering servo fits into the milled
plywood mount, and then also glue this to the
bulkhead. It is milled to fit a 15mm wide JR3341
or 3328 sized servo.
The battery tray is secured to the front support
using an M6 plastic bolt and large plastic nut,
supplied in the kit. Trial fit the bulkhead in the
fuselage, using your completed battery tray (with
batteries) to find the exact position it must be
glued into the fuselage.
IMPORTANT ! You must leave at least 10mm
clear space between the front of the lower battery pack and the back edge of the horizontal rail
26
(above) The 2 packs of 5200mAH 5S Lipos
secured to the milled battery tray.
(below) Battery tray is secured to the front
support with an M6 plastic bolt & large plastic
nut. Steering servo mount is glued into the
slot in the right side of the bulkhead.
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that the M6 plastic bolt is screwed into, because (btm) View of underside of the front support
you need this space to move the battery plate assembly and battery tray.
forward out of the rear slot, and angle it upwards
to get it out of the plane. Check this carefully
before drilling the holes for the 6mm bolt, and
gluing the front support bulkhead permanently in
place.
When you have determined the position, drill Ø
5mm right thru’ the rounded tab on the front of
the battery tray and the plywood rail on the back
of the front support bulkhead, that the plastic
bolt will be screwed into. Remove the tray and
open the hole out to Ø 6mm in the tab only. Use
the short M6 bolt supplied, or an M6 tap, to
Battery tray moves forwards & then up
thread the Ø 5mm
milled hole in the horiPlastic nut
zontal rail, and then
screw the plastic bolt
Front support
in from the underside.
bulkhead
Do not glue the bolt in
place.
Plastic bolt
Battery tray
Balsa strips
Make sure that the
bulkhead is not tight in
the fuselage and sand
as necessary to mainMin. 10mm gap
tain a 1 - 2mm gap all
around it for gluing.
Sideview of battery tray mounting
We have supplied it a
little too large to allow
it to be fitted in different positions, depending on
the length of your flight packs and battery tray.
Prepare the area carefully by sanding and
cleaning, and then glue the front support bulkhead into the fuselage with a thick mixture of
slow epoxy and micro-balloons, using the battery plate (without the Lipo packs on it) as a
spacer to ensure perfect position while the glue
cures. Also glue the nose steering servo mount
to the fuselage side now.
Cooling
Remember that all the waste energy dissipated by the LiPo batteries, Speed-controller and electric motor that power your Spark is expelled as heat inside the fuselage. It is normally the Speedcontroller that has the hardest job, and gets the hottest, and it is very important that you make
adequate provision for enough cooling air to enter, and exit, the fuselage - and make sure that it
is directed over these 3 critical components, especially the speed-controller. Certainly the batteries must not get warmer than 50°C maximum, the Speed-controller gets warmer than this - but
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it will automatically cut-off if it gets too hot to protect itself anyway.
Our prototype Sparks have been flown many
times in very warm ambient temperatures
(35+°C, 100° F) with the set-up shown here, and
the temperatures of the speed-controller, flight
batteries and motor remained inside acceptable
levels with careful use of part-throttle. In more
temperate climates this set-up should have larger safety margin, even when using a lot of partthrottle. It is most important to make the small
‘baffle’ over the top of the speed-controller to
make sure that the cooling air is directed thru’
the fins of the heatsink.
(above) A digital laser Infrared thermometer is
very useful for accurately checking speedcontroller & motor temperatures after flight.
(below) If flying in temperate weather these
two holes behind the controller should provide enough cooling airflow, in conjunction
We use a digital infrared thermometer to check with the air inlet slots in the canopy frame
the temperatures of all components carefully
immediately after flight, and this is an invaluable
tool and not expensive (available at good hobby
stores that sell quality R/C electric cars). As a
rule-of-thumb you definitely should be able to
hold the batteries without burning your fingers.
Likewise you should be able to touch the
heatsink of the speed-controller for several seconds without burning your fingers.
Speed Controller - Cooling
This is usually the most critical component, because if the temperature becomes too high during
flight the electronic sensors in the speed-controller will automatically cut the power off completely until the temperature reduces, which usually only takes a few seconds - and then it will perform normally again. This prevents damage to the speed-controller unit.
It is important to remember that the controller becomes hottest when using half-power, and this
also reduces the cooling to the unit. It is best to adjust your flying style slightly and use a combination of 90 - 100% power for most of the time, and pull the throttle right back for a few seconds during each circuit to allow the controller to cool a little. Certainly we strongly recommend
that you check the temperature of the speed-controller immediately after landing for at least the
first few flights, and increase the cooling airflow over it if necessary due to high temperatures.
The amount of air needed to cool the controller will also depend on the ambient temperatures
where you will fly your Spark. The inlet cooling air enters thru’ both the nosegear opening, and
also from the small slots that you must cut on either side of the canopy frame (see below).
To provide a strong flow of cooling air over the speed-controller you can cut 2 small oval shaped
holes in the top of the inlet joiner, about 25mm behind it as shown in the photo above. These are
25mm long and 15mm wide. However you must install the baffle (see below) glued into the
canopy frame above the controller, to make sure that all the air entering the fuselage is sucked
right through the cooling fins - and not just around and over the top of the controller.
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Increased Cooling
If the speed controller still becomes too warm during normal flying, or you will operate in very
warm ambient temperatures, we recommend that you use the following method to increase the
cooling flow thru’ the heat sink fins on the speed-controller (see diagram below).
Increase the depth of the 3 mounting blocks by another 5 - 6mm, so that you can fit the speedcontroller inverted, with the cooling fins on the bottom, making sure that they are only clear of
the duct top surface by 1 - 1.5mm in the centre. Cut a rectangular hole (with radiused corners)
in the top of the inlet joiner under the back 30 - 40% of the area of the controller. Start by making the size of the hole approx. 35mm wide and 25mm deep, and enlarge if needed. In conjunction with the inlet slots in the canopy frame, and the baffle above the speed-controller, this will
promote a very strong airflow through the cooling fins.
NB: If using this method, then you do not need the 2 small holes in the duct 25mm behind the
controller, as mentioned above, and if already cut they can be covered or taped over.
baffle to force all air
to pass thru’ heatsink
Increased Cooling Airflow
Cooling air from
canopy slots
speed-controller
mounted inverted, with
heatsink underneath
hole in duct approx.
35mm wide and
25mm deep.
Cooling air from
nosegear opening
Cooling Baffle and Slots
Although some air enters the fuselage thru’ the nose gear opening, and travels around the battery packs to cool them and then towards the rear of the fuselage, it is normally necessary to
have more inlet area than this.
We advise you to cut a pair of small slots on both sides of the canopy frame as shown, about
15mm behind the clear canopy, to increase the
cooling inlet air volume. As the canopy frame is
very lightweight you will need to reinforce these
areas first, by laminating one layer of 160 gram
fibreglass cloth just onto the area of the slots
(about 60 x 60mm).
Sand and clean the areas carefully and laminate
the cloth with slow (24 hr) epoxy resin; only just
enough epoxy to wet out the cloth is needed.
When the resin is fully cured, mill and file the 4
slots, each approx. 6mm wide and 40mm long,
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parallel to the back of the canopy opening. If you
wish you can reinforce the narrow strips
between the slots with one carbon roving, as
shown. We have included some 160 gram fibreglass cloth and carbon roving in the hardware.
The baffle is designed to force all the inlet air to
pass thru’ the cooling fins on the heatsink rather than just passing it by without doing any
cooling, as the air will take the easiest route.
Glue a length of the 5 x 5mm balsa strip across
the canopy frame, about 5 or 6mm above the
centre of the speed-controller, being careful not
to deform the canopy frame. Cut a semi-circular
shaped piece of the thin fibreglass sheet (included in the hardware pack) and glue it into the
canopy frame at an angle of about 30°, as
shown, extending past the balsa strip so there is
only a 1mm gap between it and the speed-controller cooling fins. Tack these parts in position
with a little CA, and when finalised reinforce the
joints with a very little 30 minute epoxy and
micro-balloons mixture. Remember to keep the
weight down at the front of the plane.
(above) Cut 4 cooling slots in the sides of the
canopy frame, reinforced as described, to
make sure there is enough airflow over the
speed-controller.
(below) A simple baffle plate to direct the air
thru’ the heatsink cooling fins, made with the
thin fibreglass sheet included, helps to keep
the temperatures in check.
Flight batteries - Cooling
The Lipo batteries don’t normally have too much
of a problem getting hot, and we have not had
our packs become more than 10 - 15 degrees
above ambient air temperature after a long
flight. However, if you do overheat them they will
be permanently damaged, so it is wise to check
them carefully after the first few flights. If you
cannot hold the packs, comfortably, in your hand
after flight then they are too hot! Battery temperature should not exceed 50° C.
Install them on either side of the milled plywood tray that we include (not forgetting the 5 x 5mm
balsa strips under each pack), with at least 8 - 10mm of clear space all around them, then the
air entering the fuselage through the nosegear opening is more than enough to keep these cool
when used normally. The air continues backwards in the fuselage over the speed-controller, and
exits both through the slots cut in the inlet joiner behind (or under) the speed-controller - and also
around the outside of the thrust tube and out of the top of the back of the fuselage.
Remember that the cooler your batteries run, the longer the life-cycle of them.
Motor - Cooling
The fan motor already has well-designed cooling flow through the vents in the engine mount and
this normally provides enough to prevent any chance of damage to the motor due to over-temperature. However, we also recommend that you check the motor after the first few flights to
make sure that it is not getting too hot. The rear bell of the motor should never exceed 75°
Celsius. The infrared thermometer makes this an easy job!
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Nose steering servo
The nose gear steering servo is normally fitted
inverted on the milled plywood mount that you
have installed, but if you want to use a single RX
channel to control Rudder and Steering, then
you must mount the servo the other way up.
We used a JR 334 in the prototypes, and that is
more than strong enough - and very lightweight.
Fit the shortest standard servo arm, centre it
now with your R/C, and screw the servo to the
(above) It is important to fit the small support
ply mount with the normal screws.
plate for the steering pushrod, so that the
The steering pushrod is made using the M2 nosewheel stays centred when it is retracted.
threaded rod and M2 steel clevises included. (below) A view of the steering support from
Cut to length and solder one clevise onto the the underneath, also showing the nosegear
retract steering arm end, and the M2 nut and steering servo, which is mounted inverted.
other clevise onto the servo
end. Fit the clevise into the
inner hole in the servo arm, as
only a small throw is needed.
Now retract the nose gear,
making sure that the wheel
stays centred and straight.
Take the small milled liteply
steering support and file a
2mm wide slot in it that corresponds to the height of the
steering push rod when the
gear is retracted, and make a
lightening hole. Tack glue to the side of the fuselage, as shown in the photo, with one drop of CA
and check for correct operation. When correct, glue it in place with thick CA, or 5 minute epoxy.
This small support will make sure that the nose wheels stays centred when retracted, and therefore comes down every time for landing, so don’t forget to install it !
Receiver and Switch plate
Included in the kit are the 4 milled parts to make
up the removable receiver plate, as shown in the
photo here. The small tab on the front of it slides
into the slot in the sub-bulkhead, which you glue
into the nose, and the rear is secured onto 2
small plywood tabs on the front battery support
bulkhead with M3 bolts and T-nuts.
This plate is designed to only have the RX and
switch on it, to keep the front of the plane very
lightweight, and it is recommended to install the
RX and the antenna as far away from the
Speed-controller and motor as possible to pre-
31
(above) Milled liteply parts for the Receiver
and Switch plate. The front of the plate fits
into a slot in the bulkhead, which is glued
into the nose, and the back is secured with
two M3 bolts and T-nuts.
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vent any possible interference.
Fit your receiver and switch to the plate as
shown, with a small foam pad under the Rx, and
make cutouts to save as much weight as possible. Installed here is the Powerbox Digi-switch,
which is an ic-controlled electronic switch (which
fails ‘ON’) that has a built-in linear voltage regulator (to 5.5 volts) designed specially for use with
2 cell (7.4volt) Lipo batteries for the receiver.
The single LED glows in 4 different colors and
sequences to indicate the status, including a low
battery warning, and is highly recommended. It
is available from C-ARF as an option (Product #
960610)
Glue the 2 small plywood tabs into the milled
slots in the top of the battery support bulkhead
with epoxy. Fit the Rx plate into the slot in the
front bulkhead, and insert into the fuselage a
shown. With the fuselage upside down, reach
thru’ the nose wheel opening and tack glue the
bulkhead to the nose, and then remove the Rx
plate and reinforce the joint with a little 30
minute epoxy and micro-balloons. Reinstall the
RX plate and drill the two Ø 3mm holes through
the rear tabs. Open the holes in the plywood
tabs on the battery bulkhead up to Ø 4.5mm and
insert the T-nuts with a little 5 minute epoxy.
Reinstall the Rx plate and bolt into position,
using the M3 bolts and washers to set perfect
alignment of the T-nuts before the epoxy cures.
RX Antenna
The location of the RX antenna is your choice,
but in any case a very careful range check must
be carried out before flying your Spark, both with
the motor running and off. Electric models are
always more critical in this respect, and it is most
important to keep the antenna as far away from
the motor and speed-controller as possible.
If using a ‘normal frequency’ receiver (eg:
35MHz or 72Mhz), with a full-length wire antenna, we strongly recommend that it is installed in
a ‘L-shape’ and kept as far away from any possible RF or EMI interference by installing part of
it in the leading edge of the wing. On our prototypes we cut the antenna, and soldered on
miniature gold connectors at the junction where
it enters the wing. We ran the antenna along the
side of the fuselage (opposite side from all the
32
(above) Receiver and Switch plate installation
is easy and neat using the milled liteply parts.
(below) The Rx antenna was cut at the wing
seat, had a small gold connector soldered to
it, and is connected to the remainder in a
tube in the wing leading edge when assembling the plane at the field.
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servo cables), on the outside of the inlet, down (below) The Rx antenna in the wing is in a
to the front of the wing opening. Here we cut the plastic tube in the leading edge.
antenna, leaving about 75mm extra before soldering on the plug, and this is inserted into the
wing thru’ a small plastic grommet when assembling the plane, and connected to the other part
in the wing. In the wing we glued a plastic outer
snake, supported on a liteply tab, in the leading
edge and slid the remaining antenna inside it.
(also see page 18)
Don’t forget to reach in thru’ the speedbrake
opening & connect the antenna when putting the
wing on at the airfield !!
Another alternative would be to use the 2.4 GHz
radio system.
Note: The additional miniature connector soldered close to the Rx in our plane is because we
often have to change the Rx to different frequencies for Demos in several countries.
Retracts and Valve
Connect the retracts following the manufacturers instructions in the usual way, and fit a single
quick-connector to the tube that comes out of
the wing with the servo extension cables. Of
course, if you are installing the optional Behotec
wheels and brakes, then there will be 2 air
tubes, and you can use the compact combined
brake and retract valve that is included in the
set, so that you only need one servo to operate
both systems. The air tank can be glued to the
side of the fuselage on one side of the inlet joiner using double-sided foam tape.
(above) Retract valve & servo mounted on
small milled liteply plate, and secured to the
fuselage side with double-sided velcro pads.
(below) All servo extension leads are on the
opposite side of the fuselage to the RX antenna. The extension leads and air tube for connection to the wing are shown here.
We mounted the Spring-Air retract valve with a
mini servo (JR 3341) on a small liteply plate in
the fuselage on the other side of the inlet joiner,
using some self-adhesive velcro pads so that it
is easily removable. Included in the kit are the 4
milled liteply parts to make up the retract servo
mount, as shown here, and they can be glued
together with thin CA.
Extension leads etc
Even though this is an electric model, and there should be no vibration, we highly recommend
that you install the plastic grommets that we have included (or equivalent) in all positions where
wires can rub against the edges of composite or fibreglass material, as it can easily cut through
the insulation of important servo leads or electrical cables. The photo of Rx antenna location
(above) shows the 2 grommets installed in the top of the wing.
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(below) A 2 cell Lipo of about 1500mAH is
The receiver battery is positioned to set the enough for the RX power, as the small servos
exact CG of the model, and in our prototypes it draw very little current.
needed to be installed just behind the EDF unit.
Rx Battery
We used a 1500mAH 2 cell Lipo pack (7.4 volt),
which only weighs around 70 grams, and fixed it
securely to the bottom of the fuselage, under the
thrust tube. An extension cable is then routed
along the fuselage side to the Digi-switch in the
nose. Typical current draw from these small servos for a 5 minute flight is less than 80 mAH.
Disconnect the Rx Lipo battery from the DigiSwitch when the plane is not in use.
EDF Connections and Operation
The Schübeler DS-75 fan unit and the Jeti Spin 99 speed-controller come pre-wired for you, at
the correct length for this set-up in the Spark. The gold connectors are already soldered on to
the correct length wires for you; the 3 connectors between the speed controller and fan motor
are Ø 3.5mm, and the ones on the Lipo packs and input to the speed controller are Ø 4mm.
The Speed-controller has one long JR-type extension lead from the front of it, which must be
connected to the throttle channel of your RX, using an extension cable. The other (shorter) cable
from the controller has a red plug on the end of it, and this is for connecting to a Jeti-Box display
terminal that can display various data, and adjust motor timing etc. When not in use we suggest
that you apply a small piece of tape over this red connector to prevent accidental short circuits.
The 3 black wires from the motor run along the top of the inlet joiner and plug into the 3 colorcoded (red, yellow and black) wires of the speed-controller. It does not matter which of the black
wires is plugged into which color wire of the controller the first time, but if the fan unit runs in
reverse the first time you switch it on, then you must swap any 2 of the 3 wires to reverse the
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rotation direction. After that you
should always make these 3 connections in the same orientation,
and you can slip short lengths of colored heatshrink over the the black
wires to mark this for the future.
The two 5S Lipo cells are connected
together (in series) to provide a 10
cell pack (37 volts). Connect the
negative (black) cable from one of
the flight packs to the black cable on
the front of the speed-controller.
Connect the positive (red) cable
from the other pack to the red cable
on the front of the speed controller.
The remaining red and black cables
are connected together for flight,
using the short ‘jumper’ cable (sup- (above) View of the battery & speed-controller connecplied) with the male 4mm gold con- tions. The positive and negative wires from the Lipos with
nectors on both ends. This is, in yellow heatshrink on them are joined together to switch
effect, the ‘arming’ cable that switch- on (or ‘arm’) the EDF system ready for flight.
es ‘on’ the EDF system, and is the (below) View of the finished Rx & Digi-Switch installation.
last cable to be connected before
every flight, and disconnected immediately afterwards. Make this final connection quickly - or
you will get small spark, which is not dangerous
- but can cause you some ‘surprise’ the first time
it happens!
When the system is correctly connected and
armed you will get a short musical ‘chime’ from
the speed-controller to confirm that everything is
OK. Be extremely careful carrying and transporting charged Lipo cells, and at least one of the
connectors on each battery must be taped over,
or protected, so that it is not possible to cause an accidental short circuit.
Make sure that the throttle stick on your transmitter is at the ‘idle’ position when arming the batteries and connecting the power system, and secure or have a helper hold the plane. Until the
Jeti 99 speed-controller has recognised that the Tx throttle stick on has been set at ‘idle’ it will
not power up the system, for safety reasons.
Battery Charging
Please exercise extreme caution when charging Lipo batteries, and strictly follow the battery
suppliers instructions. Never charge the Flight battery packs in the plane.
Normally Lipo cells must not be fully discharged, or they will be damaged forever, and should not
be charged at more than 1C. Therefore a 5200mAH pack must not be charged at more than 5.2
Amps. Aim not to use more than 80% of the capacity of each pack - for example if using 5200
packs you should not need to recharge more than 4150mAH each time.
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Inspect your batteries regularly to make sure they are not damaged, and have not expanded
anywhere. Be careful not to drop them or puncture the outer surface, which will damage them
irrepairably.
Certainly we strongly advise that you use a quality charger, and balance the Flight packs at least
every 2nd time that they are charged using a high-quality balancer with a safety cut-off.
We use the Orbit Microlader Pro (available from C-ARF as product #961200) and a pair of
Schulze balancers and charge the packs in series as a 10S cell. Quality balancers are available
from many sources, including Orbit, Graupner, Schulze, Emcotec etc.
Setting Up Your Spark
Centre of Gravity:
C of G range: 145 - 150mm
from front of wing at centre.
Set the Centre of Gravity at 145 - 150mm
back from the front edge of the centre
section of the wing. At this position it
should balance slightly nose-down.
Don’t forget to balance the plane laterally also, and if needed add a small weight
inside the light wing tip.
150mm
Control Throws:
All throw measurements shown below
are made at the root/trailing edge position. We did not find it necessary to use
dual rates, but instead added some
exponential to all main flight controls.
These throws are not too sensitive, and
you can fine-tune them to your personal
preference after the trimming flight.
CENTRE of GRAVITY
Elevator
Elevator throw should be about 16mm ‘up’ and 14mm ‘down’, with 30 - 40% exponential.
Rudder
Rudder throw should be about 25 - 28mm both sides, with 25% exponential.
Ailerons
Aileron throw should be about 13mm ‘up’ and 15mm ‘down’, with 40% exponential.
The reversed differential is to take into account that the hinge line being in the top skin instead
of on the centre line, so the aileron gets a little smaller as it moves down.
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During take-off and landing both ailerons can be lowered 5 - 8mm, at the root, to act as ‘flaperons’ if you wish.
Speed brake
The speedbrake should open at least 80 degrees, and 90 degrees is possible. We set it on a
slider on the Transmitter for easy adjustment - depending on the wind conditions.
You can also open the speedbrake about 20 degrees during take-off, which helps the plane to
rotate at slower speeds.
Flying the Spark
The CARF Spark is designed for powerful jet-flying with both electric and turbine propulsion. It
is not a "compromised EDF", where absolute light weight allows you to fly "low cost" with minimum power, at the expense of rigidity and overall performance. It is a full blown Jet airplane, and
can be flown as such.
The structural integrity and aerodynamic design allows speeds up to 200 mph (320 km/h) with
both electric ducted fan and turbine. The control surfaces in size and deflection are well adjusted to such flying, thus the Spark handles the different speeds very smoothly. At the slowest
speeds with high angles of attack it is still very controllable with the quite small control surfaces,
and at high speeds it does not feel "twitchy" at all. Despite its small size it's the smoothest flyer
you can imagine throughout the whole speed range - which is very wide.
The airfoil was developed by Robert Vess in the US for scale model race planes. Its minimum
drag at high loads made us choose this airfoil for the Spark. Large stab surfaces make the Spark
an uncritical flyer. The wings’ geometry with the low drag tips accounts for the Spark's agility and
performance.
Aerobatic performance is unlimited. All kinds of rolling maneouvers are easy, vertical maneouvers are breathtaking due to the huge propulsion power we designed the Spark for. Even snaps
work great, but one must keep in mind that with such a small plane at such high speeds the snap
roll rate is unbelievable, therefore only the most experienced pilots should attempt snap rolls at
all - especially because it puts the highest possible stress on the airframe, if not done correctly.
Takeoffs and landings are easy, the plane tracks perfectly on the ground and slows down nicely
with the speedbrake. For slower take-off and landing speeds the ailerons can be lowered 5-8 mm
at the root. This increases the lift of the wing and slows the plane down, without making it critical. Also a 20% extended speed brake helps to rotate the plane during take-off at slower speeds.
With the speedbrake fully deployed, the plane still needs to be brought in with a quite high angle
of attack to slow it down for small flying fields. So, don't worry about slowing the plane down and
getting the nose up in the last turn, even before the final approach.
When we test flew the first prototypes we found the performance and agility that we hadn’t even
dreamed of. You will love the flying characteristics of the Spark - that's our promise to you.
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(left) A nice fly-by with a preproduction Spark, owned and
flown by one of our UK Reps,
Dave Wilshere of Motors and
Rotors.
(above) A couple of views of the 1st prototype, taken just before the extremely successful test flights. This is similar to the production ‘Prototype’ paint scheme.
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Appendix:
Kit Contents: SPARK Kit
Quantity
1
1
1
1
1
1
1
2
1
1
1
1
1
Description
Fuselage
Wing
Fibreglass sheet, painted (servo cover set)
Stabiliser
Linkage cover, painted (for Rudder)
Canopy frame (fiberglass)
Clear canopy
Thrust Tubes (pre-cut mylar sheet)
Inlet Joiner (fibreglass)
Set of Protection bags (wings, stabs and rudder) 5 pieces
Hardware bag
Milled wood parts bag
Instruction Manual (English)
Hardware Pack
Fuselage bag
Quantity
1
1
4
2
2
2
1
1
2
1
1
2
1
1
1
1
3
6
4
4
1
2
1
1
1
1
1
1
Description
Hinge Wire, Ø 2 x 500mm (canopy fixing)
Ball-link, Plastic, 2mm (canopy fixing)
Allen bolt M3 x 12mm (nose retract fixing)
Allen bolt M3 x 12mm (RX plate fixing)
T-nut M3 (RX plate fixing)
Washer M3 (RX plate fixing)
Velcro band, double-sided, 18 x 650mm (RX & battery fixing etc)
Bolt, Plastic, M6 x 25mm (battery plate fixing)
Nut, Plastic M6 (battery plate fixing + 1 spare)
Allen bolt, M6 x 20mm (to thread hole for plastic bolt)
Pushrod, M2 x 150mm (nosegear steering)
Clevise, steel, M2 (nosegear steering)
Nut, M2 (nosegear steering)
Silicone tube Ø 6 x 300mm (cable protection)
Grommmet O.D. 14mm (cable protection)
Grommmet O.D. 6mm (cable protection)
Sheetmetal screw Ø 2.9 x 10mm (to secure Speed-controller)
Allen bolt M3 x 12mm (EDF fixing + 2 spare)
Washer M3 (EDF fixing)
T-nut M3 (EDF fixing)
All-thread, M3 x 60mm (rudder linkage)
Clevise, steel, M3 (rudder linkage)
Nut, M3 (rudder linkage)
Fibreglass cloth 160 gm 100 x 150mm (canopy frame reinforce)
Carbon Roving x 400mm (inlet reinforce etc)
Fibreglass band 20 x 250mm (reinforcement)
Phenolic strip 15 x 50mm (extra canopy frame alignment)
Wheel collar I.D. 4mm + set screw (nosewheel retaining)
39
Composite-ARF SPARK
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Wing bag
Quantity
2
1
1
1
1
1
4
4
4
1
2
2
14
2
4
4
8
8
2
1
1
Description
Allen bolt M4 x 20 (wing fixing bolt + 1 spare)
Washer, M4 (wing fixing)
Phenolic horn (speedbrake horn)
Servo mounting plate for speedbrake (1.5mm ply/fibreglass)
Aluminum angle bracket, left (speedbrake servo mounting)
Aluminum angle bracket, right (speedbrake servo mounting)
Allen bolt, M3 x 12mm (speedbrake servo mounting)
Washer, M3 (speedbrake servo mounting)
Button-head bolt, M3 x 8mm (speedbrake servo mounting)
All-thread, M3 x 40mm (speedbrake linkage)
Clevise, steel, M3 (speedbrake linkage)
Nut, M3 (speedbrake linkage)
Sheetmetal screw Ø 2.2 x 10mm (wing-mount servo fixing + 4 spare)
All-thread, M3 x 65mm (aileron linkages)
Nut, M3 (aileron linkages)
Clevise, steel, M3 (aileron linkages)
Allen bolt, M3 x 12mm (retract fixing)
T-nut, M3 (retract fixing)
Wheel collar I.D. 4mm + set screws (wheel retaining)
Grommmet O.D. 14mm (cable protection)
Grommmet O.D. 6mm (cable protection)
Quantity
2
2
4
4
2
8
2
Description
Allen bolt, M4 x 20m (stab fixing bolts)
Washer, M4 (stab fixing)
Clevise, steel, M3 (elevator linkages)
Nut, M3 (elevator linkages)
All-thread, M3 x 40mm (elevator linkages)
Sheetmetal screw Ø 2.2 x 10mm (wing-mount servo fixing)
Grommmet O.D. 6mm (cable protection)
Stabiliser bag
Available Accessories:
(please check our website for current list of options and accessories)
Schübeler DS-75 EDF unit & speed-controller set
Set two HDHE Lipos 5200 mAH
Powerbox Digi-Switch
Orbit Microlader Pro Lipo charger
Spring-Air 301 Firewall set
Behotec ‘slim’ Spark wheels, brakes, axles & valve set
Turbine upgrade set (check website for availability)
40
Composite-ARF SPARK
[email protected]
Standard Wood parts included in the kit
Fuselage hardware pack
Wing hardware pack
Stabilisers hardware pack
41
Composite-ARF SPARK
[email protected]
OPTIONAL ITEMS
EDF set (item #864003)
Schübeler DS-75 with motor installed, & Jeti Spin 99 Speed-Controller, all wired.
Flight battery set (item #865001)
two 5200mAH 5S Lipo packs, wired.
Landing gear set (item #740500)
Spring Air 301 ‘Firewall mount’ set
AVAILABLE LATER.
Please watch our website
for news of this item.
Wheels and Brakes set (item #740550)
Behotec Ø 60mm wheels, brakes, axles
and retract/brake valve
Turbine Upgrade Set
Mike C (27 Sept 2007) - version 1.0
42