24 September, 2015

Props for LARP and Cosplay (Part 4)

I'm trying a new material on this project; it's a surface coating called SR92. It dries as a flexible smooth surface, sticks to foam and resin, and functions as a basecoat when a layer of paint is required. In the bottle, the SR92 has a similar consistency to watered down PVA/wood-glue, It dries with a similar feel as well; I'm actually trying to work out the difference between the two...except that the SR92 it roughly three times the price. 


I paint the SR92 on the outside of the yoga block, and will use the same stuff to coat the shaft's hammer. The aim here is to ensure a consistent outer layer of material regardless of what lies within. This will pull the final product together as a single unit rather than looking like assorted bits thrown together. make the final product look more. Coating the shaft will be done a different way. 


I'm moulding the shaft by using a length of PVC plumbing pipe cut lengthwise in half. The inside of the pipe is smooth, so that means the shaft will be smooth. I've considered carving the inside of the pipe using my Dremel (rotary tool), to give a wood grain effect to shafts that are cast within it, but not for this particular project.

I pour the SR92 inside the pipe, allowing it to run the length, partially dry, then twist the pipe left so that the liquid coats that side, then right to complete the process, it takes about an hour to do the whole lot...I'm basically doing a rotary casting of the inside of the pipe. I then stick the two pipe halves back together, pour a bot more of the SR92 into it and rotate the whole pipe around a few times. The theory here is to get a decent coating around the whole inside, and dampen the inner material. After half an hour when that last inner coating of SR92 should be tacky, I'll start mixing up the foam. If I was making a sword (or something other than a smooth shaft), I could paint the inside of the mould with the SR92 to pick up the detail.


While I'm waiting that half hour, I measure up the yoga block for the inner rod the pass through it. The path through the yoga block is almost twice as long as most of my drill bits. So I mark centre points on either side of the block, with the aim of drilling in just over half way from each side, and hoping that the two holes will meet up in the middle.


I don't trust using my hand drill to get a perfectly perpendicular hole, so it's a job for the drill press. Normally this would be punching holes in hard timber or metal, so this feels like a lot of overkill, but I know the lines of the holes will be exactly where I need them.  


I've got some polycarbonate rod from a local supplier that will form the core for the hammer. I've tried using metal rods, which might be fine for cosplay but after a few hits in a LARP situation, they suffer from plastic deformation (that means they bend and don't bend back). This makes metal cores dangerous and often banned in many LARP groups.

Some people use PVC rods as their cores, but these can prove too flexible. When pulling blows in a LARP conflict, a PVC core tends to act more like a whip. Apparently bamboo can be used, but can become brittle with time.

This is the first time I've used polycarbonate. The rods I'm using are 12mm (roughly 1/2 inch), somthe hole I'm drilling through the hammer head is 10mm. Since the hole is slightly smaller than the rod, the foam has to expand around it as it plunges through, and it naturally tries to contract around the rod to reform it's natural shape.
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