Go Back   Cosplay.com > Cosplay Construction > Props/Accessories/Armor

Reply
Thread Tools Rating: Thread Rating: 6 votes, 5.00 average.
Unread 03-12-2013, 11:05 PM   #1
Amaterasu
Mecha-head
 
Amaterasu's Avatar
 
Join Date: Jun 2004
Posts: 284
Vacuum forming over an EVA master?

I'm looking to thermo-form over EVA foam armour for the purpose of quickly casting a breastplate. I am aware that the foam is soft and susceptible to the heat and pressure of the thermo-forming process.

I am giving the thought of sealing the foam with a brushed or rolled layer of polyester resin to give it a hard shell so that it could retain its form during the pull. I have also given a thought to leaving it coated in a thin layer of resin, and using the master as the armour - however, I have read much about cracking when the foam moves. So - that rules out the fantasy.

Then still - what about a thin layer of paper maché over the EVA foam followed by resin? But I also realise that the more I add to the surface, the more muddled and ruined the details will become.

I have also given thought to making some kind of mould of the EVA foam, and then casting it out of a hard material. However, RTV rubbers are expensive, and I am apprehensive for that reason.

Anyway, I look forward to whatever suggestions you can give me.
__________________
I like little plastic robots that make things go (fictionally) boom. Do you?
Amaterasu is offline   Reply With Quote
 
Unread 03-13-2013, 12:35 AM   #2
KOTSProps
Kin of the Stars
 
KOTSProps's Avatar
 
Join Date: Feb 2013
Posts: 88
In your situation, I'd be most likely to try the coating of PE resin so the EVA holds shape under the pressure. Just...be careful, I don't work with the stuff, so I don't know if polyester resin will eat at EVA like it does other foams (insulation board, for example, needs an acrylic sealer before any PE resin/bondo touches it...or it dissolves). If it comes out a little rough, it can be sanded as long as doing so won't wreck the details.


Now, if you want to get every detail without adding materials to your master, RTV...
It is, as you said, somewhat cost-inhibitive (1 US gallon unit is ~$153 US. Note that it actually mixes to 2 gallon volume so it does last a while). Depending on the size of the piece, you could do a mold of it with under a quart (the trial size on amazon is probably enough) as long as you have a support shell material.

As an aside, I DO NOT recommend casting large pieces with polyester resin. I did a 9" x 1" x 1/4" part for a weapon prop in PE. It shrank HORRIBLY and distorted about just as badly. PE shrinks up to 20% over the full cure time. While also cost-inhibitive at $85/gallon, polyurethane resin has a much more manageable shrink rate (about 0.01" average) and cures about 20 times faster (10 minutes vs 24 hours) without the noxious fumes PE resin (and bondo by association) give off.

The downside, other than the cost, is that RTV picks up every last stinking detail, from scuff marks and scratches you didn't think existed to the texture on whatever material you're molding. I have some small parts cut from sintra that I molded, and I should have sanded the matte finish off first...it shows up when cast. Porous materials (wood...foam depending on the cell size/closure) also need to be sealed before pouring the RTV, or one of two things happen in my experience: You break the master demolding it, or the mold stretches and tears a bit before it's fully cured (demold time for what I use is 25 minutes, but it the outer parts stay tacky for a few hours since my workshop is a bit under 73F).

I only mentioned OOMOO since I don't personally have a degassing pot right now. It doesn't require one, other RTVs I'm researched need degassed to get the air bubbles out.
__________________
Facebook Page - WIP pics, and general rants.
Commissions

2014 Events
KATSUCON 20
ZENKAIKON 2014
OTAKON 2014

Projects:
FFXIV: A Realm Reborn, Bard and Dragoon
KOTSProps is offline   Reply With Quote
Unread 03-13-2013, 02:06 PM   #3
Amaterasu
Mecha-head
 
Amaterasu's Avatar
 
Join Date: Jun 2004
Posts: 284
Thank you KOTSProps for making the time to answer my question at such length and detail.

Per your suggestion: those are my thoughts as well. I have examined some armour making sites and links thus far and I came across Volpin Props.

http://volpinprops.blogspot.ca/2012/...-claymore.html

For his Claire armour, he vacuum formed styrene over foam thinly coated with resin (Bondo, in his case, which is extended PE). I suppose this means that my EVA foam should stand more than half a chance (of course, I'll use a test piece) after coating it in resin. I intend to add to its rigidity by backing it with spray-expanding foam so that it does not warp under pressure. (Think "Mono" brand spray foam).

I am making this armour while watching my budget, as my friend for whom this is for, has recently lost her job. If I had a movie making budget, things would be much more accurate the first time, and I can't help but grin at the slice of heaven that I'm thinking about here. But I digress!

I have a pressure / degassing chamber pre-built, and I was fantasizing about the idea of using brush-on silicone to make a mould - or to even use silicone window-caulking. However, both instances are labour and money intensive. Right now, my breast plate is prototyped out of EVA and there are blobs of hot glue here, there, and major gaps and seams that would make fine reproduction a waste of time and money.

I'm hoping to get my hands on some fiber-filled PE resin, and mix it with some Bondo to create a somewhat-stronger "Rondo" sludge and built up on top of this outfit. However, that said, I don't want my breastplate to keep getting bigger and bigger as I'm expanding out with every coat.

Thanks for your feedback -- really appreciated!
__________________
I like little plastic robots that make things go (fictionally) boom. Do you?
Amaterasu is offline   Reply With Quote
Unread 03-13-2013, 11:56 PM   #4
KOTSProps
Kin of the Stars
 
KOTSProps's Avatar
 
Join Date: Feb 2013
Posts: 88
Heh, I remember reading that build last year--Harrison Krix (Volpin) is one of the guys who inspired me to get off my butt and start building props with more than foam-core and duct tape. While I'm just starting out by doing my personal pieces right now, his build blogs have a lot of valuable information on various items that I'm trying to utilize. It's also Cathy's (from God Save the Queen Fashions...another role model I follow since I'm personally a horrible tailor and looking to get better...just made my first purchases on sewing equipment this week) who did the leather/cloth parts of it. :P

And I stumbled on that guy when I was playing Final Fantasy XI...someone linked his Kraken Club and Light Staff builds on a fan-site forum. Been watching his work since. I'm actually planning on trying to replicate the staff build over the next few months once my SAO props are done.

On-topic, it does prove you can do it, but like you said...test piece first. That includes the resin coating since, like I said, I'm not sure if it's going to eat EVA like it would insulation board. Just...try to fill in any gaps in your master along the way, or they might show up in the formed piece depending on your vacuum pressure.

Since we're on the subject of vacforming, what in the hell are you using for a heat source? I can't find IR bulbs 21-23" long around here that aren't going to cost a fortune, and I'm a little scared of playing with nichrome wire and making my own heating element given that I'm limited to 110V/20A. I suppose I could use the kitchen oven, but that's 30 feet and a flight of stairs from my workshop...and I'm sure my parents would NOT approve of me doing that. My platen is about 22" square, 648 1/8" holes drilled into it...I have everything together for it to pull 28 inHg and just lack the heat source...and I need to start working on Lambent Light's hilt soon, the 0.060 styrene is staring at me like it wants to be worked with >_<;

And no, a heat gun won't do, too small for be consistent.
__________________
Facebook Page - WIP pics, and general rants.
Commissions

2014 Events
KATSUCON 20
ZENKAIKON 2014
OTAKON 2014

Projects:
FFXIV: A Realm Reborn, Bard and Dragoon

Last edited by KOTSProps : 03-13-2013 at 11:59 PM.
KOTSProps is offline   Reply With Quote
Unread 03-15-2013, 02:51 PM   #5
Amaterasu
Mecha-head
 
Amaterasu's Avatar
 
Join Date: Jun 2004
Posts: 284
Harrison is some-kind-of-awesome, he has a whole slew of tools that I have no access to. But he is someone with skills and the budget to go with RTV builds. I continue to surf is Blog and learn a tip here-and-there. Many of the methods he uses I cannot employ (laser cutting, router tables, band saws) but we can probably find a slower-less precise way of accomplishing that task at home. I'm sure he'll say that he has a lot to learn (like all guru-types) but I have a lot to learn from him. I hope to get to his level of prowess one day.

About heating the plastic:
I have seen a British fellow who looks a bit like Christian Bale on the Replica Prop Forums (can't remember his user name) that has a series of Youtube videos on this topic. He's used a space heater and a long wooden (I think) box lined with aluminium foil to reflect heat off the sides. So he places the space heater on the ground (the kind that you plug in, with ceramic-ferrous filaments) face-up and in this open ended "box" (rectangular prism) he would have a sort-of-neck that would hold the piece of plastic card in a frame. He'd allow something like 10 minutes for it to heat, uncover the lid and place his plastic card onto it with the frame. It seems like a wonderful idea.

Personally, I am hoping to use this large oven we have -- it's gas based and larger than a conventional at-home type of oven - but not by terribly much. We have about 6-7 inches more than most people - but that can only go so far. Of course, I can always make said apparatus to heat my plastic, but I'd prefer to cop-out for my initial batch. But I just may have to.

As for the gaps and imperfections in my suit, I hope that the Bondo will do the trick. I have read and seen YT videos on how Polyester resin does not *seem* to attack EVA foam. But it may depend on the specific chemistry between brands. It'd be far safer to seal the damned thing with a few coats of PVA glue mixed with flour, right? Probably. I'll do a Bondo - Fiberglass resin test on a scrap part before I ruin the suit of armour.
__________________
I like little plastic robots that make things go (fictionally) boom. Do you?
Amaterasu is offline   Reply With Quote
Unread 03-16-2013, 12:19 AM   #6
KOTSProps
Kin of the Stars
 
KOTSProps's Avatar
 
Join Date: Feb 2013
Posts: 88
Bondo should fill the gaps, though I've found it easier to be sloppy putting it on and sand it back down.

And I think I know the guy you mentioned...did a video vacforming C3PO's...bottom. Of all the parts to use in a video, it's a protocol droid's ass end. If I recall, the box is MDF lined with aluminum foil with 2 sides set to a V-shape so they sit closer to the heater....

I'm probably going to end up going that route if I can find that style of heater. I don't like it, because the rest of my setup is modeled on a cross between both of Harrison's (the shopvac-and-toaster-oven miniformer and the Protoform), but eh...sacrifices. I did my vacuum setup the way he does on the protoform. Hurt the wallet a bit, but I shouldn't have any problems with 0.060" Styrene.
__________________
Facebook Page - WIP pics, and general rants.
Commissions

2014 Events
KATSUCON 20
ZENKAIKON 2014
OTAKON 2014

Projects:
FFXIV: A Realm Reborn, Bard and Dragoon

Last edited by KOTSProps : 03-16-2013 at 12:21 AM.
KOTSProps is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -5. The time now is 07:28 PM.


Copyright 2002-2013 Cosplay.com, LLC. All Rights Reserved.
All comments and posts in our forums are the opinion of the respective poster.