Here are the photos of making the plug for the tailbox. The plug is the mock-up of the final shape of the tailbox - just the shape. A mould will be taken from the plug and then actual parts will be laminated inside the mould.

Framing: Different parts of the plug are made in different ways. The main part is made from planking on frames and here the frames are being marked-out and cut. The whole tailbox has been designed on CAD (computer-aided design) software and the marking-out is done by a combination of manual marking (very easy with pencil on MDF, which has a good surface for drawing on) and full-size templates printed from the PC.

The main 'body' of the tailbox is assembled from 'egg-boxed' frames slotted together - nobody uses interlocking cardboard to package eggs anymore, but the name has stuck. The flat panel the helmet is sitting on will be the opening in the (fixed) lower body - the edges of this panel will be the upstand on which the seal to the (hinged) upper body will fit.

The whole tailbox must be lifted to get access to the fuel tank underneath and, rather than screw on a nasty handle, I spent a whole day building this 'socket'. When combined with the hole in the under-panel, this forms a recessed handhold by which to lift the tailbox.

The two different bits of planking on the top are the opening (dark MDF) as above, and the top of the lower part of the 'body' (lighter plywood) - this has a shallow curve that delineates the yellow and black colours (see the drawing).

On the right, the first bits of planking go on the frames - exciting!

This plug is a bit unusual in that it will be used to form three different moulds - one for the lower (fixed) body, as above, one for the (hinged) upper body which is shown in frames below, and an alternative upper body (just a lid, really) that does not have the tall helmet fairing - unbelievably, some people do not like this! The reason for not making three separate plugs is that I am not a good enough craftsman to make all three bits fit together exactly, so I will use the one plug to make all three moulds which will therefore fit each other.

This is just a plug and only its shape matters, so it is made by any convenient means - assembly uses some glue, some wooden blocks, some plastic furniture blocks and some crude fillets made of car body filler. Part of this work is complicated by the need to be able to remove, for example, the helmet fairing and yet leave the framing that will make the alternative lid. This will need to be done carefully - not with a hammer!

The top of the helmet fairing (think of the Jaguar C- and D-type to get the idea) is heavily curved in all directions and so cannot be made from planking. For this part, I have reverted to a modelling technique from my childhood - bread-and-butter construction. The fairing shape is chopped up into 18mm thick slices, plotted off the PC and cut out in 18mm MDF - 15 pieces in all. Most of the slices have the inside cut away to lighten them (I wish I had done this with the frames as now I can only just lift the whole plug!). Stick all the pieces (slices of bread) together with glue (butter) and you've got yourself an armadillo.

Ten minutes with a sanding disc in an angle grinder (and a good quality face mask!) covers the whole workshop in dust. Then a good half hour with some 40 grit paper and you've got a (fairly) fair, smooth armadillo. Final fairing will be done when it's in place. The saw-tooth recess down both sides is where the plywood planking of the upper tailbox sides laps onto the armadillo.

The lower side planking is now on and it's beginning to look like a tailbox. In the left photo it's propped up at about its installed angle on the bike. Fitting the bread-and-butter top has revealed that the 18mm MDF sheet I've used has an average thickness of 18.4mm (of course it was 18.0mm at the one point I measured), so the armadillo is too long and will require some on-the-job altertions!

The middle photo shows the 'cleats' needed to hold the curve in the plywood, which is only 4mm thick. (The screws through the cleats explains the holes in the finished planking!) The difficulty in bending 4mm plywood round the relatively shallow curves of the tailbox suggests a trip down to a model shop to get some thinner ply for the front bodywork.

The right photo shows all the main planking finished and the helmet fairing in place. The grey-green colour is the first bit of car body filler applied and sanded down - the depressing truth is that this is about half the work on this bit of the plug completed, with surface fairing and finishing being the other half!

The front edge of the box needs a good-sized radius to help the airflow attach to the box - hopeful perhaps, but worth a try! Incorporating this in the basic box structure seemed too tricky, so it is an add-on. Before fitting it to the top half, a bit of hacking-and-hewing corrected the over-length helmet fairing [left].

A grid of 18mm MDF strips is shown fitted to the bottom half of the box in the middle photo. Some work with plane, file and sandpaper gives the smooth 25mm radius shown in the right photo, and a lot more dust to clear up.

Like the bottom half, the top half of the front of the tailbox is fitted with the same MDF strips and ply facing - and the last piece of wood has been added. Now for some finishing work...

The completed wooden plug is shown in the left-hand photo. The right-hand photo shows two things: a large patch of (thin) body filler filling-in a noticeable hollow in the 'planking', and the whole plug covered with a layer of epoxy resin - this really seals the wood grain (and substantially reinforces it) prior to rubbing down and applying high-build primer. But the epoxy hasn't gone rock hard after being applied last night and cannot be sanded without clogging the sandpaper, so today's a rest day!

An hour or two's work sees the high-build primer on the whole upper surface of the tailbox rubbed flat. This reveals some very slight high-spots and hollows that were not previously detectable - hence the two bare areas in the left-hand photo. So what I hope are the final coats of primer go on the plug (right).

So, the phrase "final coats" was wild optimism... However after some more 'final' coats and hour upon hour of rubbing with wet and dry (240, 400, 600, 800, 1000, 1200) and cutting compound, the top part of the plug is finally ready to make a mould for the top section of the tail box. The bare MDF is a temporary flange added to make a flange in the mould that can be used for de-moulding parts.