Pepakura's sharp folds leave you with a very angular product at the end of the day. To make your cardstock/paper/cardboard more durable and look closer to the textured game model, here are a few steps to toughen and smooth that armor.
This process works best with cardstock though it will work with all types of paper.
Once you have completed folding and glueing/tapeing your paper armor you will need these supplies.
1. Polyurethane Resin (Fiberglass Resin)
2. Fiberglass cloth of some kind
3. Minimum of 2 Paintbrushes *at least one inch in diameter
4. Something to sand with that has a med-fine grit (power sander preferred, also sanding sponges, and or sandpaper)
5. Disposable container to mix resin in
6. Poster board or something that you can set the piece on while you work on it and not get resin everywhere
7. Proper safety equipment (resperator, protective eyewear etc.) this stuff is TOXIC/carcinogenic/etc.
optionals
8. some bondo body filler can make life easier by reinforcing some pieces
9. resin is clear so spraying it with a primer after it has hardened will give you a better idea of how smooth it is and what areas should be concentrated on
Make sure before you start that you are in a well ventelated area
*If you are using any type of flimsy paper, make sure and reinforce the armor before beginning or the piece will likely end up warped. Glueing cardboard to the inside works well
*If you have a printed texture that you wish to preserve for later modifications, score areas of interest lightly with a blade, continue to do so after every external resin coat. This resin is an organic solvent and will smear most types of ink used by pens or printers once it has been in contact with the texture for a few seconds. If you are very careful and only take one pass when applying the resin, it is possible to preserve the texture.
Starting with helm only paper w/ visor.
Step 1- Resin coat to harden paper
Depending on the size the piece, the amount you will need will vary, but it doesn't take much. A whole bicep will only take a little over an ounce and a half.
1. Follow the instructions on the resin container to mix the appropriate proportion of hardener/catalyst to resin in your disposable container.
You won't have a lot of time before it starts to harden so even on large pieces never mix too much at once, just a couple of ounces is okay. You can repeat this step as many times as needed to cover the piece.
2. Take the brush and paint a thin even coat over the paper until you have covered the entire outside of the piece (leave the inside untouched). Make sure that enough is on the armor so that it not only soaks into the paper but that there is a layer on it as well. Resin is runny and will try to collect in the niches and lowspots in the piece so take the brush and keep brushing the excess to the outside until the resin begins to become very sticky. Then stop as it is starting to harden.
3. Just leave it to dry. Give it several hours to really cure before going on to Step 2.
Helm w/ first resin coat (now you know what I mean about flimsy paper warping even though this was still reinforced, I strongly suggest cardstock or cardboard instead)
Step 2- Fiberglassing the inside
1. Cut pieces of fiberglass cloth that will fit the inside of the piece and cover it completely. Don't worry about a little excess sticking out of the side. That can always be removed later. You want to cover the inside completely and make sure that the cloth is flush with the paper. If you are having trouble with this, a little bit of glue can temporarily hold it in place.
2. Mix the resin again in the same fashion as step one. This time you will need a little more (about 2 ounces for a bicep). Paint a
heavy coat of resin onto the fiberglass cloth making sure that the cloth is soaked. Don't worry about evenness or smoothness, just make sure everything is covered and flush.
3. Let cure for a good amount of time, at least several hours.
Step 3- The first sanding
1. The first thing you want is to determine which parts to keep the most angular and which ones should be smoothest (using reference pics is helpful). If any of the angles are particularly sharp and smoothing them will cut through the armor, smooth them only as much as possible. (reinforcing those areas with more resin or bondo will alleviate this problem)
* To properly smooth Pepakura Armor, you will be sanding through the original paper armor on the corners. This is why the armor MUST be fiberglassed first.
*If you have some primer, spraying it on will give you a better idea of the true roughness of the piece
***Right bicep pics after priming and reinforcement before first sanding
2. Use your sanding material to smooth your problem areas. The key in the technique is to use a curving motion when you sand, otherwise you will simply bevel/flatten the edge and have two slightly smaller angle edges.
3. Smooth everything as best you can, then wipe the dust off and continue to Step 4
Your pointy edges should now look like this. Notice that the paper is gone and only fiberglass remains.
First sanding Helm
Step 4- Coat the Outside with resin again
Repeat the same process as used in Step 1 then continue to Step 5
Step 5- The Final Sanding
1. The second coat of resin has itself smoothed out a number of the smaller angles that were left. Use your sandpaper again to go over it one more time and perfect your work.
*Steps 4 and 5 can be repeated as many times as possible, though I think that for most they should be okay. If you put tape of the outside, one repeat should fix it
Step 6- Cleaning and Paint Prep
1. Use a finer grit for a final fine smoothing and primer your piece. It's ready to go.
Smoothed edges Helm (still needs a little trimming for symmetry)
I hope that this helps anybody interested in working on fiberglassed pepakura armor.
Edited : w/ pic goodness
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