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 Rank: Super-Elite        Groups: Registered
Joined: 30/01/2013 Posts: 4,604 Points: 13,607 Location: Monmouthshire UK
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Hi I love civil aviation models and came across this kit - a 1/72 scale vac form of the 747-300 with available mod kit for the 400 version too. It's mostly vac formed but has metal, resin and PE also. I never knew that this was available in this large a scale, does anyone know anything about these kits? The size of the finished model is not mentioned but im sure its huge. Also, am i right in thinking that with vac formed kits you have to scribe the panel lines on yourself etc? The kit is by Aircraft in Miniature and can be seen here- http://www.aim72.co.uk/page233.html They also have a couple of nice versions of the DH Comet too! Cheers Steve
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 Rank: Pro Groups: Joined: 24/08/2009 Posts: 48,051 Points: -13,308
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Can't say I have come across this kit, but vac form kits can be a real pain to build and generally void of fine detail, though in this instance could be reasonable depending on the amount of PE it has. Its unlikely to have defined panel lines, so scribing is probable.
That said, if you like a challlenge then go for it..
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 Rank: Master Groups: Registered
Joined: 15/04/2010 Posts: 1,266 Points: 3,841 Location: The Quantock Hills,Somerset
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The reason for the scribing is due to the limited detail that can be added to vac moulds as the more that is added the less definition can be achieved. Vac moulding is all very well for things like cake & biscuit containers etc but why anyone thought that it would be a good idea to make model kits using such an inefficient way of producing them is beyond me,compression moulding would be better than that. By far the best medium is injection moulding especially on nice crisp moulds,the amount of detail that can be added as most of us know is fantastic. I worked in the plastics industry for many years doing all the above types of moulding as well as extrusion & the technological leaps that appeared with the advent of new plastics,better ways of making dies,moulds etc was unbelievable...except for vac forming...that just seemed to stay stuck in the rut to some extent. Rob Nolli Illigitimi Carborundum!!!Current Builds: HMS Victory, SV Thermopylae
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A friend of mine has built a vac formed kit, the detail is terrible!!!  
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Rank: Pro Groups: Joined: 24/08/2009 Posts: 48,051 Points: -13,308
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Hello Steve,
Generally speaking, they are more difficult to build than injection moulded plastic kits. For starters the way they are produced makes things more difficult for the builder from the very beginning!! The parts are moulded from flat sheets of plastic, which is heated until it is soft and then placed over a 'master' of the parts to be moulded, which is inside a sealed chamber and the air is then rapidly sucked out from beneath the sheet which draws it quickly down over the master to form the parts and then when cooled, the parts need to be cut out from the rest of the sheet by the builder, which is nothing like as easy as just cutting them from a sprue!! I have built two vac-forms in the past, both were aircraft and you have to be so careful to make sure that both halves of a fuselage or wing have the excess plastic trimmed back equally, otherwise you might have a 'fit' problem when gluing the two halves together as the profiles could end up asymmetrical. The best way is usually to trim around the part leaving a small lip of plastic then sand the part carefully on a flat surface until the lip is sanded down to the thickness of paper and just falls away, leaving the part you need - that should be the point where each half is identical, but it is all too easy to get it wrong!!
Even then the problems continue as there will be no locating pins/holes in the two halves of an assembly so you will need to add some strips along the inside of a joint to strengthen and locate the parts together properly. Also, with the fuselages especially, it is usual to have a few internal formers fitted along their length again for strength and also to maintain the shape. Something the size of a 1:72 'Jumbo' will need a lot of internal formers fitted otherwise you could end up with a Boeing 747 'Banana'!! Also, with the wings on this model being so big you would be wise to fit some plasticard main spars inside them if they aren't already supplied in the kit as you might find that they sag over time if you don't which again, is more work!! As the others have said, panel lines will also need to be scribed and extra details added as these kits are usually void of any worthwhile detail due to the way that they are made!!
I wouldn't say don't attempt it if you've really got your heart set on that kit, but in 1:72 scale it is a big plane and the guy who built the model has put in a lot of work to get it to that standard, so if you've never built a vac-form before, it might be a more sensible idea to try something a bit smaller first, just to get an idea of what is involved in building this type of kit?
It is possible to get a really nice model at the end of it, but boy do you have to work for it and even experienced modellers tend to shy away from vac-forms nowadays.
It's a bit like trying to make a high-tec Formula 1 car out of cast-iron parts if you ask me!! 
Kev
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Rank: Super-Elite Groups: Registered
Joined: 30/01/2013 Posts: 4,604 Points: 13,607 Location: Monmouthshire UK
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Hi Thanks for all the info, I have come across a build log of that kit since i last posted and it does look a lot of work, you are right - panel lines have to be scribed plus locating strips and strengtheners etc. The log is here - http://s362974870.onlinehome.us...howtopic=239569&st=0I still dont know the exact size but the diary shows the tail section to be around 30cm wide and a single engine assembly is shown compared to a 1/72 spitfire! So, thanks for all the info, but at around £150 for a base kit i think i'll leave it. Steve
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