Nice work Tony, it looks like a mini
Airfix kit in many way. I too had hours and hours of sanding and filling.
As for the mystery of that 'gap' at the intake. Bearing in mind my latest experience is on turboprops so I am a bit rusty on turbojets. If I recall correctly, aircraft travelling at high subsonic and supersonic speeds require changes to the intakes to control the changing volumes of air. Basically as speed approaches the speed of sound (Mach 1) shock waves form ahead of the aircraft. These shock waves also form ahead of the jet intakes, which causes disturbed airflow and reduces the intake efficiency of the engine. Any further acceleration increases the intake/compression ratio (the velocity of the airflow at high speed is higher than the engine can use). One way of dealing with this is to incorporate a variable throat intake and spill valves. Variable-throat-area intakes vary with aircraft speed and position the shock waves to decrease air velocity at the engine inlet and maintain maximum pressure recovery at the inlet. The spill valves control the volume of air inside the duct by by releasing some intake flow to prevent turbulent airflow (turbulent airflow is both inefficient and can cause compressor blade stalls).
In the case of our Phantoms, that intake wedge has a hinge. At supersonic speeds (Mach 1 and above) the wedge is pushed outwards to reduce the throat area and therefore also the volume of air entering the inlet. At subsonic speeds (below Mach 1), the wedge is retracted towards the fuselage, increasing the throat area and the volume of air able to enter the inlet.
Hope this makes sense!
