Hanovale AHC Kit Assembly Tips

Polyurethane Kits
How hard are polyurethane kits to build?
In general polyurethane (PU) kits should be considered more difficult to build than the same kits would be in polystyrene. There are a number of reasons for this, not least being the fact that PU kits need to be assembled using superglue (cyano acrylate). Superglue is unforgiving, you don't get the opportunity to redo a piece that didn't fit together perfectly the first time. Errors can sometimes be resolved using acetone to dissolve the glue however exposure to acetone can damage some polyurethanes.

Other factors that cause PU kits to be a little more difficult include the fact that the rubber moulds that the liquid PU is poured into can change size slightly, and to a lesser extent, shape over time and in different weather conditions. The mould releases commonly used in PU casting also mean that, unless the models are scrupulously cleaned before painting, blemishes can occur in the paint job. These are typically circular marks with a core of very poor paint coverage surrounded by a rim of thicker paint. These blemishes are commonly known as "birds eyes" or "fried eggs".

If you have some recent experience, however little, of assembling polystyrene kits then you can, with a little extra care, assemble the simpler PU kits and then work your way up to the more difficult kits.
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Basic tips for working with polyurethane kits
Perhaps the most important habit to get into when working with polyurethane is to test fit everything, repeatedly, until the fit is perfect. Because of the manufacturing method and the fact that the mould is not absolutely constant as it is with the metal dies used in polystyrene kit manufacture, you will need to adjust the fit of pieces slightly. Most of the time this will require no more than a few passes over a sheet of wet-and-dry abrasive paper or a little remedial action with a small file. In either case it is imperative, if you are to build a model you're proud of, that you test fit the two pieces frequently before gluing.

You do not need to apply much superglue to the job to get it to stick together (assuming the two pieces are reasonably well mated) One of the most common errors is to use too much glue. The best technique is to make a little pool of the glue on a tile or piece of glass and to transfer the glue from the pool to the job with a toothpick or similar sized object. Don't apply glue directly to the job from the superglue bottle or tube. This is a sure way to end up with, at least, superglue runs and fingerprints on the face of the job, possibly even with your fingers stuck to the model. To make matters worse, hardened superglue is harder than PU so it is extremely difficult to sand the glue off the face of the model.

There are a few things that superglue is not good at. The first is that superglue does not stick well to hardened superglue. If you have to separate a previously glued piece then sand all of the (semi-)hardened superglue off before trying again. Superglue is not the appropriate adhesive for gluing clear parts onto anything. This is because the superglue fumes as it sets (and for quite a time afterwards) and will leave a white coating on the clear part, making it opaque. Assuming the clear part is not structurally important (and for windows etc the strength of the clear part is generally unimportant) use either an acrylic cement or a silicone sealant/adhesive. The silicones are good because any excess can be peeled off when dry.

There will normally be a covering of flash wherever there are windows on a model. With Hanovale kits the preferred method of removing the flash is to work the back of the model in a figure 8 manner on a sheet of medium to fine abrasive paper until the flash is thin enough to remove without using a knife. Kits from other manufacturers may require different techniques. In either case you should read the instructions as there may be reasons why the technique recommended here is not appropriate.
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To straighten a bent casting
From time to time long castings can bend while in the retail packaging. It is a fairly simple matter to straighten bent PU castings, requiring nothing more than heat and a flat surface on which the casting will cool. Urethane needs a temperature in excess of 60 degrees Celsius to soften. You can achieve this temperature using hot water (hotter than can be obtained from the hot tap though) or by heating the casting in an oven. The oven method is probably the simplest and safest: place the casting on a flat surface and heat in an oven at 60 to 80 degrees Celsius for 20 minutes then turn the oven off and allow the casting to cool slowly. If necessary you can weight the casting down to ensure it sets straight but this is normally not required. Occasionally you might come across a casting that cannot be straightened by this method. In these rare cases the casting has been bent before it set and the "memory" it retains is of the bent position. If this happens contact the manufacturer for a replacement part.
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Laser-Cut Styrene Kits
Laser cut styrene kits can be considered an introduction to scratch building in styrene. The two most difficult steps in scratch building have been done for you - the marking out and the cutting. Styrene, when laser cut, develops a rolled edge on both sides at the point of the cut, much as it does when cut with a blade. For best results this rolled edge must be removed by sanding both faces lightly with 600 grit wet and dry abrasive paper. It will only require a couple of passes of the model over the paper to remove the protruding edge. At this time you should also check for saw tooth edges and remove these as well with the abrasive paper or a fine file. To assemble laser cut styrene kits you will require a solvent cement such as MEK or EFD Simply Glues' Tetra. For detail made of other materials (eg the awning braces) use superglue. As mentioned above, you should not use superglue to attach clear glazing as it will cause a white smoke on the windows

Low Relief Buildings Probably the easiest of all laser cut styrene kits to assemble are the low relief buildings. The AHC low relief building kits consist of a facade with decorative and structural components to be laminated onto the facade. In most cases there is also an awning to be attached to the front. The kits also contain clear glazing which could be made from any one of a number of clear plastics. If it hasn't been identified for you then the safest adhesive to attach the glazing to the model would be clear silicone sealant.

The room required on your layout for these kits is indicated on the appropriate web page. Where the kit includes an awning you should allow another 4mm between the front of the awning and the kerbing.

Some of the low relief building kits also form a good test bed for further modification and decoration. For ideas on this topic see articles by Alan Downes in Model Rail October 2006 (Commercial Breakdown) and July 2007 (Plastic Rules, OK!)

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