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Rizon

Namibian Air Force Chengdu F-7

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I had this idea of building a Chengdu F-7 of the Namibian Air Force for some time now. Seeing that a 1/72 scale F-7 does not seem to be on the horizon, the original plan was to convert an old Academy MiG-21 that is lying in my stash to the F-7. Problem is that that stash is some 1600 km away from me in the capital of Namibia. And unfortunately I don’t get many a chance to go home to my home town these days (Job, life, you know the story...). Then a local stationary store had one of these Academy kits in stock, and my wife convinced me to acquire it and start to do some model building again, after a 3 year break.

So, armed with some nice plans of the F-7 that someone was so kind to put on the internet and the kit I set off to work – and a very big surprise awaited. I know the Academy MiG-21 is not the greatest, but this was an odd one. Somehow the kit parts and the plans did not match up at all. Double checking that I printed the plans to the correct scale, the problem quickly became apparent: who ever scaled the kit used the overall length, including that very long Pitot tube, to scale the fuselage. The result is a VERY long fuselage, bit deeper than required, and approximately the correct width. Due to the stretched and distorted fuselage, the wings were also over-scale, but strangely the horizontal and vertical stabs were pretty much bang-on scale. Go figure....

Considering shelving the project, I spent an evening studying the fuselage, and found a way of salvaging the kit. Since this project would in any case require the liberal use of a hacksaw, I might as well go all the way and go mad on the fuselage. Muhahaha....

This compares the scale plans to the kit fuselage and the parts that need to be trimmed:

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And this is the result of all the chopping on one half of the fuselage. With the whole other side to compare:

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And gluing it all together again.... Gives a good idea of the size difference!

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The Academy kit also models the fuselage with a distinct Coke bottle shape, something that is not really present on the MiG-21. This was corrected by chopping the fuselage (again!) into 3 pieces after it had been assembled and inserting plastic card in the centre section to “fatten” the mid fuselage. Visible in the photo by the white pits of plastic:

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At this stage one begins to wonder why subject oneself to all of this torture. Well, it is fun. But one day, one day I’m gonna build one of these kits where you put a tube of glue in the box, shake the whole box and out comes a perfect model. One day...

Oh, and I am the new guy here; so HELLO! :bye:

Edited by Rizon

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Facinating work there and brave with it. Will be watching your continued progress :thumbsup:

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Your wife convinced you???

Where do I buy one of those - I have a PayPal account so can organise Mail order!!

Cheers.. And look forward to your progress.

Dave.

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Rustywelder,, I don't have a link ot the drawings - I remember stubling upon them via Google on some modeling website, possibly Master194.com or so. I downloaded them and was happy,... The thouht never crossed my mind to place a bookmark. I do however remember that the plans originate from some Eastern European aviation magazine. If I find the link again I'll update.

Rabbit Leader, don't think you can buy them, only find them if you are very, very, very lucky!

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When you had cut the fuselage up, did you sit back and think 'bloody hell...' I know I would have.

God work by the way...

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wow, great work!

kind a like imaginative work like yours! :)

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Next up were the cannons. Already indicated in the first post were the blast panels on the fuselage. These were fashioned from thin plastic card and glued to the fuselage surface. Once dry they were sanded down to an even thinner thickness. Not done so easily though, keeping the thickness the same, without removing parts of the fuselage is somewhat challenging.

The cannon housings/blisters were fashioned from styrene tubes and heat stretched sprue. In this kit I used a lot of sprue or parts of the chopped off fuselage pieces to build parts for the conversion. Never mind the recycling aspect of it, Evergreen styrene is hard to come by and bloody expensive in this far corner of Africa... So I don’t have much choice in that regard...

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Once the canon housings were installed, the rearward part was sanded to a slightly square-ish section, as some photos of the F-7 suggest. But here the photo resources are pretty thin, so how correctly the end product came out is subject to debate. Anny comments from out there?

The air brake also needed to be repositioned, and the big hole of the kit part filled with sprue and a little bit of filler. The kit airbrake was then simply fitted to the surface and faired in with plastic card, as the real thing does sit in a blister, almost as if the airbrake was added as an afterthought.

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The air intake was another mini-project in its own. The original kit part was a single piece, and not all that representative. Fortunately however, it was of the correct inlet lip diameter, so it was useful as a starting point. First the shock cone was removed:

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And then the shock cone was remodelled and the outer part cleaned up.

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Finally a bit of pipe was glued to the shock cone, the splitter plate added before the whole thing could be glued together and installed. The intake is not built to have the full length ducting including cockpit tub etc. Primarily to save my patience and simply because it will simply not be visible...

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I added the nose weight to the inside of the shock cone and once the intake bit is installed a bit of sanding is required to remove the step where it joins onto the fuselage.

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At this point most of the work to convert the "Academy MiG-21" into a "1/72 scale MiG-21" so I can convert it into a "Chengdu F-7NM" was done....

OK, maybe not the wings, but that was simple, as I’ll be showing soon....

Edited by Rizon

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Wow,

Very nice work there! I have a Bilek kit that I am thinking of converting into an F-7MG with the "cranked" wing but I also thought of doing a Namibian NM because it looks cool and I wanted to do an African bird vice perhaps a Bangladeshi one, initially. I hope I don't have to put that much work into the Bilek kit though. I have some extra parts from the old KP MiG-21 and will probably put a resin nose cone and cockpit in (modified) to bring it up to snuff. I do wonder if the Revell MiG-21 is a better starting point though.

Looking forward to seeing more, keep up the good work!

WARDOG

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This is great stuff!

The namibian f-7s are very cool. I do wnder how often they ever get airborne however...

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Hello Rizon

I have been dreaming about this project for a long time, watching your steps eagerly.

I have a question for you, did you examine Revell's Mig 21 F-13 ? is it an option to begin as Wargdog stated?

Second, can you share F-7 scale drawings with me? my e mail address is omererkmen@superonline.com

Best

Omer ERKMEN

From TURKEY

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Thanks for the link sharkmouth! Yup, those are the plans I work from, now all of you can join in :winkgrin:

As for the choice of kit, pretty much anything will be better. The Revell MiG looks like a good choice from the pictures I have seen. For me it is simply a matter for lack of choice. One isn't spoiled for choice in this part of the world, that kit was what was available. And then there is of course the the matter of blunt ignorance - I didn't know better... Had I known beforehand of the shape problem I most probably would have avoided the project. But now I somehow have to extricate myself from this mission... :coolio:

As to decals, probably print them myself - that will be a first for me. Along with some other challenges, like vacuum forming the canopy. I'll cross that bridge when I get there....

I dunno how often they fly. I don't know anyone in Grootfontein that can answer that as to how often the jets rattle the town. Google Earth does show one of the trainer variants doing some flying, so they do fly them! But I know that the helicopter squadrons are quite active.

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Next up was the vertical stabiliser and the spine. As already mentioned, the vertical stabiliser is very close to the correct outline, so only a small amount of modification is required – the majority of that effort being directed at thinning width at the root of the vertical stabiliser. Attention was also given to the fairing at the rear top, it is somewhat oversized in the kit. I simply replaced it with the oversized flutter weights of the horizontal stabs from the kit.....

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The rudder line is not quite correct, so I first filled up the lines with some stretched sprue, sanded it down and then trimmed off the entire rudder. Separating the control surface of course gives a much more convincing effect in the end that a merely scribed panel line. The fin root extension also received a bit of attention to shape it into the peculiar “folded” transition from the spine to the vertical stabiliser by adding strips of styrene and subsequently sanding them down to blend in. Complicated description I know – best look at the photos of the real thing to see what I am getting at... Another major modification, this time however F-7 related, is the drag chute housing, which I constructed from a bit of 3.5 mm tube and sprue. Finally a bit of surface detail like the radar warning receiver antennas and so forth were installed...

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The spine is fashioned from the kit part; it however needs to be increased in height by approximately 2 mm. Easily done with the aid of sheet styrene. The whole fin and spine assembly was then glued into place:

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A method I started using in this build is using heat stretched sprue as filler. I doubt it that I am the first rocket scientist to come up with this idea, but I find this a neat trick to quickly and easily seal up gaps. Simply take a bit of heat stretched sprue and glue it into the gap with liquid cement of Tamya’s Extra Thin Cement. I would advise using a marginally thicker piece of stretched sprue than the gap and then letting the cement dissolve the piece a bit as one pushes it into place using a blunt knife or similar. Apart from the homogeneous material properties of the fix, the method requires an exceptionally minimal amount of sanding. On some cases no sanding was required at all if a bit of care was taken when gluing the stretched sprue in.

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Thats all for the moment...

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That's a great start. Can't remember my missus every suggesting I do a bit of modelling !!!!!

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The wings. First they needed to be trimmed down to size. Easily accomplished.

The trick however is in ensuring that the main gear attachment point is in the correct position. For this the bottom piece of the wing needs to be repositioned relative to the original position; the attachment point is not in the correct position if one only shortens the wings. On the left the pieces of the trimmed wing, with the still complete wing on the right:

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The outer part of the “cranked arrow” wing I built from 0.5 mm sheet in a monocoque fashion, with some piano wire forming the main spar. The piano wire was anchored deeply in the inboard part of the wing. At the same time I cut off the flaps from the wing and built the leading edge slats and ailerons separately from the wing itself. The wing root fairing was also added, again made from sheet styrene (barely visible in the photos)

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Some piano wire is again commissioned as the main carry trough spar and secondary spar for the main wings. The two “spars” simply slot into the cavity left inside of the wing between the top and bottom wing parts. Here the wings have already received a light first coat of Tamya rattle can primer and been scribed with some panel details:

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Edited by Rizon

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Just a small update:

Fuselage got a coat of Tamya primer to check for imperfections owing from the plastic reconstructive surgery. There were surprisingly few places that needed attention.

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The white primer paint made it easier to scribe/re-scribe panel lines. I’ve never done this before, so still very much in the learning phase here. What currently works best for me is to use a blunt knife to score the lines. I merely am looking for a surface imperfection, not a properly deep engraved line. The knife also makes it possible for some free-hand scribing. Saves on the tedious masking! Here an example of the scribing on the vertical stabiliser. Also added some smaller details like ram air intakes for the engine bay.

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Then it was time to glue the wings on, again making use of my stretched-sprue-filler trick to close the small gaps between wing and fuselage:

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The horizontal stabilisers were modified by replacing the out of shape flutter weights with styrene rod and adding the bulges at the root of the wings:

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And this is what it looks like all together at the moment. Including a balsa wood plug for the canopy. Still have to figure out how exactly to vacuum form the thing. Still one of the big challenges lying ahead...

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Seeing her all together as a main airframe brings home how much work you are doing to modify the basic base kit to produce an accurate F-7. Brave work done well and very entertaining to watch.

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