Vacuform Basics
by: Rowan Baylis

The case for vacuforms hasn't been helped by their reputation for being particularly difficult to build - I think this is largely fostered by people who've never actually built one. In reality, vacuform kits aren't particularly harder to tackle than most short-run kits and, by ignoring them, modellers are depriving themselves of many exciting subjects that have yet to appear in other forms.

Through talking with many modellers, it seems to be right at "square one" where things go wrong... just getting parts ready to use. The aim of this introductory article is to try to dispel some of the fear in which vacuforms are held, set out some easy techniques for getting over this first hurdle and so encourage more people to have a go at this enjoyable and, ultimately, very satisfying style of modelling. Obviously, I'm primarily an aircraft modeller, but I think the techniques will be basically applicable to all types of model.

The pain is in the parting?...
The first task with any vacuform model is to remove the parts from the surrounding sheet of plastic. The way almost all commercial vacuforms are moulded means that when the parts are cut out they also include the thickness of the plastic sheet. This excess must be removed to achieve the true size of the parts and there are two popular methods which make it easy to see just how much plastic to remove:

1. The first way is to use a permanent marker, ink or thinned paint to mark the outlines of parts on the sheet.

2. The second way is to spray the entire sheet with an aerosol primer. Some modellers prefer this method because it also highlights any blemishes which will need attention later.

Both methods work equally well and the only important thing with either technique is to make sure the paint or ink reaches right into the angle at the base of the parts; if it doesn't, you'll hit problems in the following stage.
Cutting out the parts
The next stage stage is to carefully run a new blade around the the outline of the parts. Don't try to cut right through - there's no need and you'll probably just mess things up if you try; just score gently with a number of light strokes.

Obviously, the closer you cut to the parts, the less spare plastic you'll need to get rid of later. One neat trick to reduce the clean-up is to score around the parts at an angle of about 45%. Also, for complex shapes I normally run a few extra score-marks out to the edge of the sheet so it's easier to work on tight areas.

Now for the moment of truth! Once you've scored right around the part, gently flex the styrene sheet. As you flex it, the part will begin to separate from the sheet - don't rush it, but the plastic will split accurately along your score-marks and the parts will drop free. Once the parts are removed from the sheet, the purpose of earlier ink/paint stage is obvious - all the excess is highlighted as bare plastic.

The parts will be moulded with any windows and cockpit cutouts solid - whatever you do, don't be tempted to open these up yet, because they help maintain the rigidity of the parts, which helps you sand them accurately.

Sanding & trimming
There's no escaping this stage... but it really isn't as tedious as many would have you believe. Some modellers like to work on a flat surface, other's prefer to hold the parts and use a tool like Handvik Handy Sander or wet 'n dry paper attached to a piece of tile (as in the photos) - either way, work steadily and sand the parts with a "figure of eight" technique. Check your progress frequently to make sure you don't sand away too much. On large parts try to maintain an even pressure across the surface and shift your grip regularly to avoid "pressure points".
Opening up cockpits and other areas
With the parts cut out, now's the time for a test fit and to start thinking about opening up the cockpit and other openings like wheel-wells etc. I do a test fit first to make sure areas like the cockpit actually line up - there's nothing more fun than to carefully clean up the openings in each fuselage half and then find they don't match!

The "score & flex" method works fine if the cockpit reaches the edge of part (as in the case of Koster's Martin Maryland in the photos) - just be careful you don't bend the part too much, but areas like windows and undercarriage openings need a different approach...

To clean out these openings, whatever you do - don't try to cut it them straight out - it's all too easy for the knife to slip and cause an accident to you or the model. What I do is drill a series of small holes inside the edge of the scrap area. Once the holes are all drilled, simply joint them up by "nibbling" and scoring with a scalpel and clean up the jagged edge with a file and wet 'n dry. This method takes a little longer, but it's much more controllable than just hacking with a knife.

Conclusion
Hopefully that wasn't too painful... I normally have the have the main parts of a vacuformed kit cut out and clean in an hour or so. The encouraging thing is that, with the parts prepared correctly, you're all ready to tackle the rest of the build, safe in the knowledge that the two most dreaded tasks in vacuform modelling are behind you. From here on it's up to your own skills - like any short-run kit, what you get out is largely down to what you put in. But that's why we're modellers, isn't it!



This article comes from Armorama
http://www.armorama.co.uk