Materials are as follows:
34 Sheets of 160gsm A4 card (Some call it cardstock)
150cm x 3cm Aluminium or PVC tubing
Several metres of Steel or Aluminium tubing (1-1.5cm diameter, square or round)
500ml can of expanding insulation foam (May require more if it is a low expansion variety)
Fibreglass and resin (Optional)
5mm Thick modelling foam for the head details
Spray / Acrylic paints (Greys, silvers, blue, black, white)
Fabric / Leather swatches for the handle grips
Step 1: Papercraft
There's no point in me providing a step by step guide to Pepakura, as there are already so many guides, but the basic idea is print, cut out, and stick together. I prefer superglue as a method of sticking tabs, because it sets faster than hot glue, and has a negligible separation between the layers of card/paper.
The model I used was composed from about 6 main pieces, all intersecting on the virtual model, So I had to decide which I would create my own cuts/tabs for (All of the head, some bits on the shaft, and the hilt), and which I would make exactly as the net dictated, and cut to fit the main model after (Two blocks between the head and the blade). The blade itself only needed some holes cutting to fit the steel tubing through.
Step 2: Metal Reinforcment
The steel tubes all had a cutout running down them (They were from a swimming pool wall's rim) and so they were very prone to twisting/kinking when bent. I'd strongly suggest square, complete cross-sectioned tubing insead.
All were attached using 2 to 3 small bolts, by drilling a bolt-width-hole all the way through first, then widening the side that the screwdriver needed to go through (After marking out their required positions). Holding the paper sections up to it was vital to making sure they'd all fit together after.
For the larger sections like the head and the blade, it's worth creating several small holes to fit the nozzle from the can of expanding foam right into the corners of the shape (For the blade, I actually left one side un-constructed, and built it only when the completed sections had been filled). It also helped to clamp the blade between some flat pieces of acrylic to stop it bulging outwards when the foam expanded, and to string the head of the hammer up to the main shaft as the foam set.
I'd taped the joins between sections that I hadn't made tabs for to prevent the foam seeping out.
In the last picture, I filled the part with foam completely separate from the rest of the hammer, then cut it in half, and carved out the right parts to allow it to fit on after.
Step 4: 3D Detailing & Hardening
Thin card details can be cut and stuck on wherever you feel is appropriate. All the details on the blade are meant to be recessed, but I felt it would be easier to have them protrude rather than engrave them, or cut out a whole sheet to stick over the blade (Although this would give a much smoother finish).
The 3 braces on each side (2 at the bottom, 1 at the top) were made from spare plastic rods (With a very wide "I" shaped profile, though rectangular would be just as good) and bent into shape using a soldering iron to melt it at the crease lines (Tsk tsk!)
I used screws and multi purpose glue to fix the braces and the block above the lower 2 braces, which were both authentic looking, and strengthening.
I used a polyester based filling compound to repair any dents caused by warping, and coated the whole thing in resin to harden it (Don't resin the foam though, as it will certainly crack and leave you having to repaint it later). I finally applied a single layer of fibreglass strips to the upper handle, becuase with the force of gripping it, the card and expanding foam would likely suffer some denting.
Step 5: Painting - Base Coats
I gave it a silver spray coat for the blade and raised details, and a dark acrylic coat for most of the shaft, and recessed sections. Ideally, refer to screenshots for these, because the actual shaft is more of a dark grey/brown.
Step 6: Painting - Details
Paint on the blue "lights" in the head's grooves, and on the blade. If you mask them off, be careful not to let it build up too thick before removing the tape (I did, and I actually had to score the edges to get them off). If you have the spray paints available for these tasks, it will look much more professional, but I only had acrylics at hand.
Finally, the all important silver dry brush to give the idea of wear and scrapes. Try to only put it on the edges which actually stick out. Edges that are actually protected by other edges all around would only experience wear from the user, and not from the environment (Eg, being dropped). To protect all the layers of paint, I used a clear coat of spray on lacquer, and lightly sanded the areas the were supposed to be matte (All but the blade).
Step 7: Handle Grips
I ended each strip at an angle, and atteched the beginning by covering it in multipurpose glue, and performing a complete wrap around before starting to spiral upwards. I was running low on strong multi purpose glue, so I used PVA for the entire middle section, which, although slower to dry, seems to hold just as strong.
After gluing the ends down, I held them in place with a tightly wound velcro strap (Winding string around would work too). I sanded the overlapping sections to give them a scuffed look.
Step 8: Finished!
Anyway, after all those steps the hammer is finally complete
The final hammer is 160cm tall, and my old MA37 is just 80cm. I'm 182cm (6ft exactly), so it only just reaches my chin.
Its final weight is 2.08kg, and it's pretty difficult to hold horizontal with an outstretched arm (Picture 3!), but at least I'd be able to carry it around all day at a comic con without destroying my arm!