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So basically, here's how it goes. I'm planning on scaring the living buhjeezus out of the neighbor kids this coming Halloween, so I'm getting a head start. I want to make a costume of some kind of Tyranid or Eldar, perhaps a Tyrant or Carnifex? Even better, how about a Lictor or Broodlord. For the eldar part, I was thinking something along the lines of a Death Jester, Maugan Ra, Avatar of Khaine, Eldrad, Warp Spiders, Karandras, ooohhh the choices... Any opinions? Also, how should I go about making this beast?
I'd go with something nurgle, it would give you room to move in it, if you can be creative enough it'll look good. Get your guts pouring out... Find some real rotted foods for the authentic smell.
The Emperor Protects
IG Best Gen 1st overall of 10 DE 4th overall of 6
Eldar 3rd Overall/Best General of 26--2nd Overall/Best General of 7--1st Overall/Best General of 11
Kevin's Nurgle idea, while being rather disgusting (You have to put up with the smell too!), might be just the ticket if you really want to freak people out. Though a really well crafted Maugan Ra outfit would certainly fit Halloween down to a T.
I'm not sure quite how you'd pull either of these off though. What I could recommend is a bit of a trundle around the internet. I know there are some cosplay resource sites out there and, while people may not have built something along the lines of what you're looking in to, some of the techniques or materials they've used may give you some inspiration. Maybe not, too, but there can't be much harm in giving that a go!
For materials, I'd suggest polyfoam (you can get it in 8x4' rolls meant to be used as underpadding for sleeping bags; contact cement bonds it pretty well). Paper mache is also pretty fly, and has the virtue of being dirt cheap. Chicken wire can be useful, but it can also be sharp, so you'll want something between it and skin (like the previously mentioned polyfoam). Using all three together is the ticket for armour; basically build a layer of polyfoam to wear over normal clothing- you can shape it to some degree as well, but what you're looking for at this stage is a comfortable under layer that will flex with you. Once you've got that, use the chicken wire to provide rigidity to specific plates that make up the armour. You can paper mache directly over that if you want, but sometimes this will let the underlying layer of chicken wire show through, so if it doesn't make the costume too bulky, you might almost want another layer of foam before the mache. The final step is detailing, where you put the relief sculpting onto the plates; small cuts of polyfoam in the shapes of the sculpted detail are your best bet- you'll have to play around with it to bevel the edges of your shapes so that they don't rise up off the armour plates at a 90 degree angle. Then just paper mache over the detail work. The last stage is painting- you'll want the paint to go on thick to conceal any seams between paper mache strips, and it'll take a few coats.
Now if you go with a tyranid beasty, you could still use much the same process, but you may want to spray it with a liquid latex instead of using paper mache. The first big problems with nids is that their legs usually have an extra joint and don't bend the same way human legs do. The second is the extra set of limbs and whether you want them to move. It can be done, but it's really difficult, even for an experienced cosplayer with a big shop to work in. An armour plated humanoid is a lot easier.
hmmmm... I'm planning on making this look like a professional job, and I'm not too concerned about prices. I also plan on walking around in it quite a bit; would your idea last? Could I take it on and off multiple times without it being completrly destroyed? Perhaps some titanium poles for the bones?
If money isn't an object then there are most likely better ways to go about it; I've never had an opportunity to work with anything too pricey, so I can't really offer any solid advice on how to do it. Cosplay sites are a good idea, and if you're looking for armour, try the SCA- I once downloaded a free tutorial for samurai armour made from paint barrel plastic that had been shaped with a heat gun- never got a chance to try it, but the idea sounded solid enough. SCA armour is built very tough, because they not only have to wear it multiple times, they have to fight in it. You won't find plans for anything sc-fi, but you will get lists of techniques and materials, as well as suggestions on where the materials can be found.
A lot of how durable it's going to be would probably depend greatly on how the outfit is designed, I would think. Something that's built in one piece is going to be difficult to get on and off and could quite possibly be broken in the process. Might be worth getting some professional advice for the design, at the very least, even if you're intent on building this yourself.
On a slightly random aside, there's this add I've seen on TV at the moment which features someone wearing a termite suit - I'm wondering if you could look in to using something similar as a base and building that up in to what you want.