discussion Tony's tiddler: Tamiya 1/100 F4 E/J

[Guest]

Kit turned up during the week, and it's not as small as I was expecting. Then again, the Phantom was a big old bus.

Just one sprue, (plus a canopy) but the parts look quite well detailed. No cockpit details, and I'm not sure my skills will allow me to improve on it much. I expect to get started when work allows.

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[flyjoe180]

Looks to be a nice little kit Tony. I was also surprised by the size of the Phantom even in 72. I could fit four Boomerangs onto it, and it requires no nose weight

 

[Guest]

Made some progress recently. The kit goes together fast as there are so few parts, which is good really, as I reckon I'll spend twice as long filling and sanding. Maybe I should have spent more time working on the fit.

In picture 3, should that gap (behind what I assume is the airbrake) be filled? I can't find a definitive image.

Also, has anyone got an idea how I could get a couple of pilot figures in 1/100? Is there some other figure I could use instead?

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[Dave W]

Which gap are you referring to Tony?.The airbrakes are the engraved shapes on the wing undersides just aft of the undercarriage bays.

 

[Ian M]

If you are referring to the gap between the fuselage and the Intake behind the baffle or splitter, I think that's what they're called, then no it should not be filled.

As for pilots in 1/100 might I suggest ants!!! lol.

Ian M

 

[Guest]

If you are referring to the gap between the fuselage and the Intake behind the baffle or splitter, I think that's what they're called, then no it should not be filled. As for pilots in 1/100 might I suggest ants!!! lol.

Ian M

Thanks Ian and Dave,

Ian, that is the gap I meant - just below where the back-seater would be (if I could find one small enough) I was confused by seeing some photos with them covered, and some models with them filled.

As for the "baffle" things that seem to stick out of the air intakes, what are they for?

 

[Ian M]

I think they are to direct the air into the Intakes. They might also have a function that adds to the compression, forcing more air than would normally fit in the hole.

Come on Dave help me out here, I am way out of my zone LOL.

Ian M

 

[flyjoe180]

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!

 

[Dave W]

I think they are to direct the air into the Intakes. They might also have a function that adds to the compression, forcing more air than would normally fit in the hole.Come on Dave help me out here, I am way out of my zone LOL.

Ian M

When the aircraft approaches supersonic speed the intake ramps move outwards making the intake smaller and causing a shock wave to form.This shock wave slows down the air as it reaches the engine.For the engine to operate the air entering it has to be kept below supersonic speeds.This way aircraft can fly faster than the speed of sound,But the air entering the engine is always subsonic.Difficult to explain and it's years since I studied this stuff when I was doing my licensed engineer exams.

 

[flyjoe180]

Dave's explanation is much easier to understand. As an aside, another way of controlling the intake flow volume and shock waves is using a cone, as on the Lightning. It works in the same way, at high speed it extends, retarding a shock wave and reducing the volume and velocity of air into the inlet. At lower speeds it retracts, allowing a higher volume of air into the engine.

 

[Dave W]

I can tell your aircrew Joe,as you make it sound very complicated!.Good explanation though.i spent a number of years giving Arabs on the job training.So I tend to over simplify things.

 

[flyjoe180]

Nothing wrong with simplification. Cheers.

 

[colin m]

Whilst not a supersonic aircraft, have a look at the air intakes of a Victor. Lots of things going on there slowing the air down.

 

[papa 695]

Hi Tony hows the tiddler coming along ?

 

[Guest]

Hi Ian, thanks for asking. Work has got in the way a bit, but I'm trying to prepare myself mentally for masking the canopy! I've never done it before, but there's plenty of good advice on here - new blade etc. I plan to do my 'copter windows at the same time, so I can prime them together.

 

[flyjoe180]

How did you get on with the masking Tony? I'm a fan of Roman's 'masking tape and new blade' method, it works well.