Cermark Super ViperJet MkII PART1 - RC Universe

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RCJI viperjet art. 11/3/05 12:59 pm Page 25 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 APRIL/MAY 2005 RCJI 25
RCJI viperjet art. 11/3/05 1:48 pm Page 26 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 26 RCJI APRIL/MAY 2005
Page 1: RCJI viperjet art. 11/3/05 12:58 pm

Cermark Super ViperJet MkII PART1 - RC Universe

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