Cermark Super ViperJet MkII PART1 - RC Universe

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VIPERJET
MKII
AUTHOR:
KEITH WHIDDETT
PHOTOGRAPHER:
KEITH WHIDDETT
Cermark Super
ViperJet MkII PART 1
A scale ARTF that has sport-jet looks
he Cermark ViperJet MkII is a near scale
‘T(1:4.3) model of an American full-size
home-build kit. The full size version is built to
a very high specification which includes oven
cured vacuumed carbon fibre with a 1/2 inch
honeycomb core. Built by subassemblies, it
allows the customer to complete their project
and spend more time flying and less time
dreaming about it. The astonishing performance
demonstrates the outstanding design and
engineering skills that have gone into the project.
With a choice of power plants from mild to
wild it can be tailored to individual taste. An
estimated rate of climb of 12,000 ft/min and
speeds of 500 mph make this a must have on
any pilot’s list.’
That’s a description of the full-size aircraft.
The model version is much the same - it is
without doubt an ARTF of the best quality. It
comes in the normal coffin sized cardboard
box, with everything individually packed in
bubble wrap bags which will make good covers
once the model is finished.
The construction notes (24 pages with 54
photographs) are mainly photographs with not
much in the way of instructions. I think that
the manufacturer has assumed that anyone
building this model has some experience of jet
modelling. So this review will cover some
important points in case they could be of help
to those who might find the instructions lacking.
Some of my suggestions reflect personal
preferences, but they are all included for safety
reasons above all else.
When I start to build a scale model the first
things I look for are details of the full size.
Colour schemes, undercarriage, lights, cockpit
detail – these are just a few things that spring
to mind. This is where the full-size ViperJet
scores high as it has its own web site - (go to
www.viperjet.com) This has loads of first class
pictures of everything of interest and will be a
big help to all those scale purists amongst us.
Fuselage
The fuselage is of gel coated epoxy fibreglass
construction with carbon fibre reinforcement
at all critical stress areas. All the laser
cut aircraft grade ply formers are supplied
glued in place, with the glue fillet reinforced
with carbon fibre tows, making a very strong
structure. The only work to do here is to care-
The space under the cockpit shows the reinforcing
of the former bonds. Viewed from the front,
showing the bifurcated air intake
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VIPERJET
MKII
Kit Specification
Wing span: 74" (188 cm)
Length: 80" (203 cm)
Take-off weight: 22.25 lb (10 kg)
Engine: 18-27 lb (80 – 120 Newtons)
thrust
Radio: 6-8 channel
Servos: 8 required
Basic components:
Fuselage moulding and separate nosecone
Engine hatch
Tail-plane halves and elevators
Wings, ailerons and flaps
Fin and rudder
Cockpit floor and canopy
Equipment tray (in two parts)
Servo mounts, control surface horns and
retaining screws
Engine by-pass
Optional equipment:
Winglets
Ventral fins
Conformal tanks
Twin wall exhaust duct
Retracts, legs, wheels and brakes
Strobe lights
Scale pilots
Smoke system
fully sand the joint between the two fuselage
halves and touch-up the finish with an airbrush.
The conformal tanks and the winglets shown here are optional extras – otherwise this is the basic kit
Cockpit
The cockpit is a nice piece of work. The
seats are all formed in fibreglass, the floor is
recessed below the canopy line, which gives a
full depth impression, and a sheet of decals
for the instrument panels finishes it off. All
that is left to do is to find a pilot. I found one
in a Carrefour supermarket while on holiday
in Spain. Am I alone, when in the unfamiliar
surroundings of a supermarket, in that I
search for drinks’ bottles that will make fuel
tanks, tea strainers that will become FOD
guards and toy dolls to fill jet cockpits? I
The nose-gear mounting tray bonds are also
heavily reinforced
The cockpit tub is glass fibre, not vac-formed ABS. The decals add realism
Adapter plates and spacers will have to be made to suit the engine installed. These are for the
Frank 70/14
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VIPERJET
MKII
Fitting the bypass duct was simple. All that
was needed was to cut slots in the sides to
allow it to slip over the adaptor plates.
The recommended engines are the JetCat
P80 or the P120. I think that it would be asking
too much of the P80 - it would no doubt fly
it, but it would lack vertical performance.
The Frank engine strap trial-fitted to the by-pass duct and engine mount
Tanks
There are three fibre glass conformal tanks
supplied as optional extras, two of which go
each side of the engine, the other sits in
between the inlet ducting. All three are very
close to the C of G so trim changes during
flight should be a non-event. All three tanks
have to be glued into place with silicone
sealant but first be sure to roughen up the
areas to be glued on both tank and fuselage to
remove any traces of mould release.
I employed my usual method of connecting
each of the saddle tanks to a Y connector then
connecting that to the central tank in order to
minimise fuel flow restrictions.
The central tank has the bung and feed pipes
exiting at the top, which makes for a short
length of pipe inside the tank. It is quite difficult
to get the clunk to drop down to the “top”
when the tank is inverted so I ended up wrapping
solder around the clunk to increase its
weight, which should help.
No hopper tank was supplied and the central
front tank could be connected directly to the
fuel pump, in which case a membrane (filter)
clunk of the Graupner or Orbit type would be
preferred to the plain clunk. I choose to install
a hopper tank, as recommended by Cermark,
before the pump. Always try to keep fuel lines
short to minimise restrictions.
The three conformal fuel tanks are an essential
option
Weight has been added to the clunk fitted to
the central tank
found a suitable pilot and with a little surgery
I soon had him in the seat complete with sunglasses
and flying helmet. The pilot is one of
the Power Elite team from the World
Peacekeepers set. He is called the Helicopter
Commander, should any body want one. The
cost was 7!!
Engine installation
I found that the ply engine mounts were
positioned too far apart for the Frank 70/14
that I intend to use. I had to extend these by
using 3 mm thick aluminium sheet bolted to
the underside of the original mounts. A spacer
was added to bring the engine up to the
thrust line, ensuring that the by-pass duct
lined up with the centre of the engine.
Further checks found that the by-pass ducting
was a snug fit between the factory installed
ply mounts. It is now obvious that an engine
big enough to fit without the need for adaptor
plates would completely fill the by-pass! All
engines will require adaptor plates and packers.
For the record the gap between the
mounts is 140 mm, the by-pass duct diameter
is 132 mm and a JetCat P120 is 112 mm in
diameter.
Tail feathers
Both the fin/rudder and tail-plane/elevators
are made to a very high standard in gel-coated
epoxy resin impregnated carbon fibre cloth.
They come with the holes pre-drilled for the
‘Robart’ pin hinges. I found that most of the
holes were not drilled on the centreline and
some were over-size. Holes requiring correction
were opened out so that I could fill them
with a piece of balsa glued into the over sized
holes, which were then re-drilled to the correct
size and on the centreline. For this
process I find the Robart Hinge Jig a very useful
tool as it aligns the hole to the centre as
well as ensuring that the hole is square to the
hinge line. I found that the inner Robart
hinges on both tail-plane halves needed shortening
as they protrude into the hole which has
been left for the servo lead.
I mass balanced the elevators before attaching
them to the tailplane halves as a precaution
against flutter. To do this I drilled a 5 mm hole
into the side of each elevator aerodynamic balance
tab. I took some ‘heavy powder’ which I
had left over from my helicopter days. This was
used for weighting rotor blades. I mixed 30
gms of this with some epoxy resin, loaded it
into a syringe and squeezed it into the hole.
The elevator was held upright with the leading
edge down so that the mass would solidify at
the leading edge of the balance tab. I understand
that heavy powder is no longer available
so small shot would make a suitable substitute.
There are two aluminium spars factory-fitted
to each tailplane half that slide into tubing fixed
in the fuselage. This leaves very little other
work to do, just clean up the joint seams on tailplane
halves and elevators and then install the
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VIPERJET
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Countersunk Allen head screws sit flush in load-bearing washers in the
fuselage, retaining the tailplane
Aileron and flap linkages with lock-nuts and clevis retainer sleeves all
correctly fitted
supplied epoxy fibre board horns in the elevators
to line up with the servo output arms. I cut
slots with a razor saw and epoxied the horns in
place, taking care to make sure the holes in the
horn lined up with the hinge line. The servos
are fixed using the aluminium brackets supplied,
and wooden blocks set in the pre-cut
holes in the underside of the tailplane halves.
The elevators and fin are held in the fuselage
by counter sunk 3 mm bolts which screw into
the aluminium spars previously mentioned. A
nice metal insert is imbedded into the fuselage
at each screw position which gives a positive
and solid fixing. This also makes everything
easy to take apart for transportation.
Wings
The wings are constructed in the same way
as the tailplane. This really is quality moulding
at its best. Only the joints between the wing
upper and lower halves need cleaning up. The
epoxy fibre board horns are installed in the
same way as for the elevators. Again the holes
for the Robart hinges for the ailerons and flaps
An aileron and a flap servo will be fitted to the
hatch cover. Note the glue on the protruding
hinge ends
are all pre-drilled, all you are left to do is glue
them in. However, the factory-installed balsa
blocks for the hinges are too small, in my opinion
as the Robart hinges protrude 10 mm into
the wing space, so when glue is put into the
hole it is pushed out into the wing. It would
have been much better to have had bigger
blocks so that any glue put into the hinge hole
would have remained in contact with the hinge.
Before gluing any hinges always put a smear of
Vaseline on to the pivot area to stop any glue
from jamming them solid. I shall cross-pin my
hinges to be sure that they will not pull out.
When installing the flaps I had to remove
some of the edge of the lower wing surface so
that the flap did not foul the wing skin when
fully deployed. I removed 3 mm to give me the
required movement. The servo hatch is precut,
the flap and aileron servos are mounted on
the inside surface with the supplied aluminium
brackets and wooden blocks. I found that if a
servo is positioned in the middle of the hatch
there is a good chance that it will foul the top
wing skin. More space can be found for the
servos by moving them forward.
There is a very nice wing fairing that attaches
to the root wing rib. This is simply put on over
the wing root and super glued in place, making
for a very nice transition from wing to fuselage.
The winglets at the tips are pushed on and held
in place with two bolts. A nice touch are the
lenses for the lights or strobes, whichever you
prefer to fit. I lined the inside of the lens cavities
with sticky backed silver paper to act as a
reflector for the lights that I will fit at a later
date. A screened single core wire had been
installed in each wing, this could be used to
connect to the lights or strobes, but the screen
would have to carry the electric current. It may
be more sensible to use this wire as a pull-wire
to pull in a screened two-core cable, especially
if strobe lights are installed.
All that remains is to install the landing gear
and jet-pipe and test fly the aircraft. This will
be described in the next issue.
Likes
A model which is very pleasing to the eye
and a good choice of jet scale subject
Big compartments for engine and radio
installation
Cockpit and seats, not made from ABS.
Fixing of fin and tailplane, easily taken
apart for transportation.
General finish of the whole model
Dislikes
Instruction manual - very little in the way
of written instructions
Balsa blocks for pin hinges too small, but
hinges could be pinned
Optional extras could be included in the
kit as they are all needed
Contacts:
Manufacturer: Cermark.
e-mail: cermark@aol.com
Technical Support: tamjets@yahoo.com
UK distributor: CML Distribution
www.cmldistribution.co.uk
E-mail: cml@cmldistribution.co.uk
Tel: 01527 575349
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