BY ADAM GRACE
PROP & MODELMAKER
As the full size helicopter took shape in the workshop, a smaller team began work on the 1:4 helicopter. The model was scheduled for its pyrotechnic demise at a fire department testing facility on the outskirts of Sydney. It was planned to be shot using multiple high-speed camera positions, so it was required to be fully detailed inside and out. The model shop would also be involved with preparing pieces for the 1:4 building the helicopter would crash into.
Construction of the helicopter began with sectional outline drawings provided by the art department. These were sourced from a Bell 212 service and maintenance manual. The sectional outlines were at even intervals and were enlarged to the correct size, glued to plywood sheets and cut out with a jigsaw. Sheet styrene foam at the correct thickness was alternatively glued to the plywood forms, with dowel used to keep alignment along the pattern length. Once dry, the whole assembly was sanded back to the plywood, and so in turn producing accurate patterns for the body, tail, and engine cowling.
The patterns were then sealed in aluminium foil and fiberglassed, filed and sanded till smooth. Details were added using Evergreen, K&S; metal sections, styrene and foamex sheet. Sandpaper was used to duplicate the non-skid lining on the roof. Rivets were achieved by drilling and inserting dressmaking pins.
When the patterns had been completed, they then had multi-piece fibreglass molds taken from them, and then fibreglass copies were pulled from the molds.
Using the full size helicopter and photographs as reference, patterns were also produced for the rear stabilizers, engine intakes and exhausts, rotor mechanicals and other external details. The various pieces were scratch built from acrylic, styrene and foamex, filed where necessary and then given a coat of primer. When completed they were molded in silicone rubber, from which urethane resin copies were produced.
The windows were made by vac-forming clear P.V.C sheet over male plugs taken from the appropriate areas of the helicopter molds.
While the exterior patterns and details were being made, interior pieces were also being constructed. The instrument panel and dash were made from foamex sheet and detailed with artwork prepared by the art department. The full size steel and fabric seats were duplicated in heat-bent acrylic rod and Evergreen with cotton seat covers. Other instrument housings, air conditioning ducts and interior details were made in, yes, foamex, styrene and acrylic.
The door exterior panels were carefully cut from the body shell, and the interior details built up in grey cardboard with sewing pin rivets. The interior wall linings were also finished in black and grey cardboard. The floor and ceiling were achieved by using a heavy gauge embossed black aluminium foil. These materials were selected so that they would tear more easily than sheet plastic, and they would be a consistent color through the material, avoiding tell-tale white debris when blown up.
The model was fitted with an aluminium frame incorporating the mounting point for the special effects designed crash rig. It was also fitted with a hinging mechanism so it would split open upon impact at the point where the tail joined the body.
The front left nose section of the model was cast in latex with a fibreglass tissue backing to enable that part of the helicopter to crush in when it hit the building. The landing skids were fashioned in annealed copper to realistically fold and twist.
The rotors were cast in fibreglass, balanced, and fitted to electric motors housed within the helicopter body. The main rotors were electrically driven off the motor shaft, while the tail rotors were driven via a flexible shaft coupled to a bevel gear located within the model gearbox housing.
Four helicopter shells were pulled from the molds. Two were sent to the special effects department for pyrotechnic tests and trial fitting of effects rigs. The model shop retained the other two, of which only one was completely detailed and finished. The remaining model was kept in the case of a second take being required. Fortunately, the first take was a success and therefore the second model was not used.
THE 1:4 BUILDING FACADE
As well as the helicopter, the model shop was also involved with the construction of a section of office building in 1:4 scale. Working in conjunction with the steel and construction departments and special effects riggers, the structure became a 12 metre tall scaffold frame on which the building facade was attached.
Within the facade frame were toughened glass panels that had been mirrored on the top half of the panel, and then back sprayed on the clear lower half to match the real building. The central impact area had breakaway glass panels and was similarly prepared. The glass panels were secured to the frame with silicone.
Placed behind the breakaway glass panels were scaled pieces of office furniture such as desks, chairs, computers, shelving units and stacks of paper. These pieces were not highly detailed, typically being constructed from MDF and sheet styrene and foamex. They were not expected to be seen in close-up, but nonetheless included as an extra level of detail within the building should they be seen during the explosion.
At the fire testing facility, the model facade and its support scaffolding was surrounded by large greenscreen painted flats. These were placed so that the mirrored portions of the glass would reflect only the helicopter and the surrounding green flats. This enabled the C.G. effects artists to have complete control over the matting in appropriate backgrounds complete with realistic distortions.
Cameras were placed behind the greenscreen flats with just the lens protruding through a hole, or within green painted boxes suspended from various points on the building. Various positions were chosen to capture the most dramatic angles for editing.
The special effects department had built a rig that would swing the helicopter into the building on a predetermined arc. This enabled precise positioning of all elements for pyrotechnics and for camera angle placement. The effects crew rigged the interior of the building facade with concentric rings of detonator cord and placed air motors to blow the shattered glass outward. The hinged mechanism within the model tail-body join was fitted with an explosive release. All the pyrotechnic effects were triggered by computerised timer, reprogrammed for the various explosive events by the millisecond.
After months of planning, construction, and extensive tests, all the elements were ready. Everything was set in their positions, awaiting the narrow filming at midday when there were no shadows cast on the greenscreens. The crews were in designated safe positions and the explosions were armed. The cameras were switched on, and when they had reached speed, action was called. A spectacular crash and explosion was affected, with everything going according to plan. It was all over in less than ten seconds!
When the rushes were viewed, the resulting footage was impressive. This was before any visual effects were added. The final stunning sequence was seamlessly composited by D Film, a Sydney based C.G effects facility. A subtle ripple effect during the explosion was added completing the helicopter crash sequence and alluding to the computer controlled world of THE MATRIX.