Step 3: From Polygons to Smooth Curved Surfaces

Once you've built up enough layers of fiberglass to make your pieces nice and strong, the next thing you need to do is smooth out the faceted surface of the pieces so they'll stop looking like low-poly computer models and start looking like heavy pieces of armor. 

Here's what you'll need:

A grinder with a sanding flapwheel
Automotive body filler (commonly known by the brand-name "Bondo" and available at your local hardware store)
A smooth surface and putty knife to mix your Bondo
A flexible plastic spreader (probably for sale on the shelf right next to the Bondo)
80-grit sandpaper
100-grit sandpaper
150-grit sandpaper
Eye, ear, nose, and throat protection so you don't fill your delicate parts with nasty, nasty glassfibers.

Use the grinder to take down the corners on the paper model.  An 80-grit flapwheel will make quick work of the fiberglass and paper, but it will also make a huge mess of nasty, toxic dust.  It's best to work in an outdoor area and you'll still want to wear eye, hearing, and respiratory protection.

Once you've knocked down the high parts, you'll want to build up the low, flat spots with some Bondo.  Use a flexible spatula to spread the material out over the surface and build up a smooth curved surface.

When working with Bondo, make sure that you only mix up as much as you can use in about ten or fifteen minutes.  After that it'll turn solid and you'll end up wasting a lot of material.    If you add too much, you can always sand or grind it off after it hardens.  If you add too little, you can simply add more after it hardens as well.

Once you're satisfied with the smooth surface you've created, it's a good idea to spray on a coat of primer to get a uniform color to get a better impression of how smooth the actual surface really is.  Chances are you'll discover that you're not as done as you thought you were and you'll want to add more Bondo and do more sanding.

You'll repeat all these repetitive steps repeatedly for all of the individual armor components.  It's going to make a mess wherever you're working as well as quite a ways downwind.  Consider this when choosing your workspace.

If you're like me, you never make one of anything.  To make these forms into the basis of an army, proceed to the next step.

If you're a rational, sane person, you can skip ahead to step 8 and use the smoothed, reinforced paper models as one wearable costume. 

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