Is casting this my only option?

Discussion in 'Replica Props' started by Risu, Feb 4, 2012.

  1. Risu

    Risu Master Member RPF PREMIUM MEMBER

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    I'm about half way done with this helmet I'm working on and I've hit a wall. The base helmet has gaps where the ears are, and in the finished piece they've been covered with these plugs. I'm attempting to scratch build the plugs, and not having much luck. I was planning to stack three 1/2" foam exercise mats, cut off the beveled edge, and curve the back part around the helmet, then coat it with fiberglass resin. Unfortunately, in my tests the resin does nothing to harden the foam, even with fiberglass cloth added in. My original plan was to figure out a way to create a "pep file" drawn by hand on some card stock that I could fold into the shape, but I can't figure out how to do that. I've also got some pink insulation foam that I could carve into the shape, but EVERYTHING melts that foam, even regular Krylon primer. Anything I sculpt out of it will be incredibly fragile and will melt in short order. I've got sheet styrene, but not enough to stack up to the 1.5" thickness of the plug. Normally I would just bite the bullet and flush $50 worth of silicone down the drain to mold the foam and do a resin cast of each ear, but I don't know if I have the time for that whole process and the curved section in the back might make that plan impossible. I'm open to suggestions right now, can anybody recommend a way for me to do this?

    Oh, and I'm just talking about the basic shape of it, all those little details and greeblies will be added later.

    Photos thanks to Primrodo.
    [​IMG]

    [​IMG]
     
  2. Ozymandius

    Ozymandius Sr Member RPF PREMIUM MEMBER

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    Fortunately there is a very cheap and simple solution.

    You had the right idea with the foam, but just used the wrong kind. Go to a craft store and pick up some green floral foam. It's rigid, carves easily, and doesn't melt when coated with fiberglass resin. Best part is that it you can get it for just a few bucks.

    One note though. Most places will carry two different kinds of green foam. One has big open pours, and the other looks like packed blocks of sand. You want the sand like blocks as the resin will adhere to the surface better.
     
  3. clonesix

    clonesix Sr Member

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    Let me see if I understand your question after reading all that. You want to make an ear piece for the above helmet? Is that the same as the audio pick up, or the black hemi-sphere next to it? You want to make to fit into or onto the base helmet?

    Polystyrene foam (pink foam) will melt if you use any type of solvent based paint, and you don't want to use sheet stock.

    Can you get some polyurethane foam? It will not melt

    Can you use 1/4" acrylic and stack it? I get scraps for free.
     
  4. Risu

    Risu Master Member RPF PREMIUM MEMBER

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    I have some "1/4" thick" acrylic (its actually more like 1/8", great honest marketing there) that I was considering using. I might possibly stack 3 sheets of it, carve the bevels, and then glue some card stock around the edge of it, fiberglass, and maybe rondo it for added strength. That was the last resort though as that 2' by 4' sheet of acrylic cost me close to $100 and I've been meaning to make stands for my blasters and whatnot with it.

    The green floral foam won't melt!? That's news to me. How's the surface after it's coated with fiberglass resin? Is it smooth? What about rigidity? Since it is a helmet, I want it to be able to withstand the kind of abuse caused by taking it on and off, putting it down on tables, bumping into stuff, and possibly even getting smacked over the head, some con-goers can't be trusted to behave like adults. As for which section I'm talking about, I mean the big chunk there. Here's a picture of the original base helmet that I'm modifying. The big section missing at the side there is what I need to fill in.

    [​IMG]
     
  5. robstyle

    robstyle Master Member

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    Risu, how about using MDF as the base. If your handy with a dremel you can avoid the hot shards of doom acrylic will nuke at you when trying to shape it.
     
  6. Risu

    Risu Master Member RPF PREMIUM MEMBER

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    Does MDF cut easier than wood? I tried shaping some wood grips for my Mal gun a while back and didn't get very far. I went through about one cutoff wheel per inch of material.

    I'm going to try to find the floral foam today, I've never seen the dense kind before, but I've never actually looked. That feels like my best bet right now. If that fails I'll move on to the next option.
     
  7. Nwerke

    Nwerke Master Member

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    The florist's foam is phenolic resin IIRC. It definitely won't melt from paint or resin. It can be a bit soft sometimes so take care not to crush it, or buy a harder grade if there is a choice. A slab of urethane foam would be the perfect solution if you have any suppliers (signwriters use a lot of it and may have scraps for free). Get some of that stuff in stock and it will change your life.
     
  8. robstyle

    robstyle Master Member

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    MDF is basically saw dust mixed with glue. Ive seen both amazing things created with it and utterly mind numbingly horrible things done with it as well. You dont want Ikea press board but actual MDF. Its sold is small sections at Home Labyrinth.
     
  9. Ozymandius

    Ozymandius Sr Member RPF PREMIUM MEMBER

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    Floral foam is actually quite fragile and will break and crumble easily. So don't think of it as a structural material, but as a form to build something structural on. In other words, it's only going to be as strong as the material you put on top of it.

    Polyester resin alone is going to be brittle. But layer in a little fiberglass and you've got a very strong piece.

    Ideally, you could lay a single layer of fiberglass on top. Then remove the foam from underneath and reinforce the underside so that you don't add extra mass to the surface.



    The best way to use it for this application would be as a buck to build your panel on top of, and then remove the foam when it's done. This way you would have access to the underside so that you can reinforce it.
     
  10. NormanF

    NormanF Master Member RPF PREMIUM MEMBER

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    There are two densities of floral foam that I am familiar with: one that will dent while you just look at it on the shelf and another that is more rigid. The stuff I used as a core for the Mini-Nuke I am working on is "Desert Foam" made by FloraCraft. It's not as rigid as styrene foam or the pink stuff so you still need to be a little careful with it. I used one layer of resin on top of that and it was a bit rough. I would think you could use two or three coats and then sand the final coat. Or do like I am and cover it with body filler and sand that smooth with 320 grit paper.

    I like the idea of using the foam as just a form and removing the foam later. Hope I remember it when I need it.
     
  11. Risu

    Risu Master Member RPF PREMIUM MEMBER

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    Thanks for the advice everybody. I'm about to head out to get some stuff at Home Depot and Michael's, so I'll check out the foam and MDF.
     
  12. Risu

    Risu Master Member RPF PREMIUM MEMBER

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    I did a test with the resin on the sand-like floral foam and the results were excellent. I'm not sure yet if I'll just put several coats of resin on or if I'll hollow it out and fill it with some rondo. I'll play it by ear. Fiberglassing the outside probably won't happen though, because getting the cloth to stick to the surface and not get bubbles underneath seems impossible. It would just mess up the shape. I'll do the carving tomorrow. The bricks are kind of small though, can anybody tell me what type of glue works best to hold two bricks together long enough to resin them? I've got Elmer's, 2-part epoxy, E6000, 3M 77, Super glue, JB Weld, hot glue, and Barge.
     
  13. FakeBritishAccent

    FakeBritishAccent Sr Member

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    I always use Bondo over green floral foam and I haven't had a problem with melting.
     
  14. Ozymandius

    Ozymandius Sr Member RPF PREMIUM MEMBER

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    The surface of the green foam is so crumbly that glue is next to useless. Best bet is to pin the pieces together with some skewers. Popsicle sticks or something similar.

    And you can always put the fiberglass on the inside to reinforce your part so you don't mess up your surface. I like to lay the glass out on a pallete and wet it down with resin before applying it to the part.
     
  15. NormanF

    NormanF Master Member RPF PREMIUM MEMBER

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    If you got the super soft stuff, I don't know what to tell you. The desert foam you can use Elmers, but it takes at least over night to dry.
     
  16. Risu

    Risu Master Member RPF PREMIUM MEMBER

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    I got the dry sand, not the wet stuff. I'll do a test with Elmer's, but I don't really have that long. Maybe I'll coat a popsicle sick in 2-part and stick it in to pin them together.
     
  17. Risu

    Risu Master Member RPF PREMIUM MEMBER

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    This stuff is incredibly frustrating to work with and I'm doubting it's durability. Tomorrow I'm going to pick up a sheet of MDF and try my hand at that. So long as I can finish the job with a dremel tool and I don't need any kind of fancy saws, I should be fine. Way less work to get it paint ready, too.
     
  18. robstyle

    robstyle Master Member

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    be easy with the dremel on MDF as it will sand like nothing with that high speed and paper grit. You can bondo MDF to repair the surface or coat it if need be. You will need to seal it if your after a usable part and not a master for molding. If so you want a filler primer. Ive cheated around that before and used gloss coat but again, only when molding MDF and not as a usable part.
     
  19. Risu

    Risu Master Member RPF PREMIUM MEMBER

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    What kind of negative effects would I expect if I only primed the MDF with regular Krylon primer? Would multiple coats of that still get the job done? Basically I just don't want to go out and buy an $8 can of primer if I don't have to. $8 is a pretty large percentage of my monthly budget right now.
     
  20. NormanF

    NormanF Master Member RPF PREMIUM MEMBER

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    I was afraid that soft foam would not hold up. Even the stuff I use is mostly there as a base for resin and body filler.

    Make sure you wear a respirator while you work on the mdf.
     
  21. robstyle

    robstyle Master Member

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    MDF is wood based regardless if its sawdust and glue. It is porous so it should be treated as if your treating wood. If that krylon primer works, go for it. If not, youll know quickly as it will seep in.
     
  22. Ozymandius

    Ozymandius Sr Member RPF PREMIUM MEMBER

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    No one ever said it would hold up. It's not a structural material. Just a base to build something structrual on and then throw away.

    No offense, but you guys seem reall intent on making this as hard as possible. :unsure
     
  23. Risu

    Risu Master Member RPF PREMIUM MEMBER

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    I don't have the proper dremel attachments for wood, so this is slow going, but I've got the layers of MDF glued together and the shape drawn out, I've started cutting the basic shape. I'm not too worried about that or the beveled edge because I've got a dremel trio, but I haven't figured out exactly how I'm going to accomplish the slightly slanted surface where it tapers down toward the chin. I've got some rasp files, those are probably my best bet so long as I take it slow. The MDF turned out to be pretty weighted, which is probably a good thing because it will help balance the weight of the helmet out once the hose is attached. As is, the hose pulls the helmet back on the head slightly and the hard hat rigging inside isn't quite tight enough to stop it.

    Rob, would it help at all for me to paint Elmer's onto the surface of the finished MDF piece and let it dry on before priming it, or would that not be a good idea?
     
  24. robstyle

    robstyle Master Member

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    I dont think Elmers is a good idea as its not a solid surface. Maybe some have had luck that route but me personally I wouldnt do it if your after a final item and not molding it for castings.

    You also dont really need any proper dremel wood bits. Get the rough shape then go at it with the sanding barrels. You could make yourself a simple jig to attach the tool to if your hands not too steady or breathing too heavy. Its a tedious task but slow and steady is whats called for. If you have to walk away for a few minutes inbetween, do it.
     
  25. Risu

    Risu Master Member RPF PREMIUM MEMBER

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    Yea, steady hands is what it will come down to for sure. I'll probably just get in the ballpark and go the rest of the way with some low grit sandpaper on a block.
     
  26. LDR

    LDR Sr Member

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    What is the helmet from? It looks very cool.

    And what is the base helmet called? Looks like a nice project.
     
  27. LDR

    LDR Sr Member

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    found it! Dr Who!

    heres a couple more pics from the guy who made the original:

    Doctor Who 2
     
  28. Risu

    Risu Master Member RPF PREMIUM MEMBER

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    Yep, Doctor Who. The reference pics would have been very useful to me a week ago. Oh well, I'll just have to live with the inaccuracies.

    The original helmet was a Scott respirator helmet from the UK. Unless you're as obsessed with the show and this costume in particular as much as I am, I wouldn't recommend the build. The helmet cost somewhere in the vicinity of 200 pounds and I had to have it shipped over by a friend because they won't send it to the US. Scratch building isn't a very realistic option either, since the inside and outside of the helmet are both visible and there are a lot of complex parts. Maybe with a hard hat as a base it could be managed.
     
  29. drmoreau

    drmoreau Active Member

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    +1 for carving green floral foam and covering it with fiberglass. i've done that before to pretty good effect. also lightweight and strong.
     
  30. LDR

    LDR Sr Member

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  31. Risu

    Risu Master Member RPF PREMIUM MEMBER

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    Wow, I wish that place had been selling them when I bought mine.
     
  32. LDR

    LDR Sr Member

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    might be worth emailing the guy who made it and see what he used for greeblies and things.
     
  33. Risu

    Risu Master Member RPF PREMIUM MEMBER

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    It's a little late for my build, but I have been thinking about maybe stripping the whole thing down to repaint it later. My light box is definitely different from the real thing, it's way too narrow. Maybe he could give me some info I could use on the rebuild.
     
  34. Risu

    Risu Master Member RPF PREMIUM MEMBER

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    Well that went nowhere. He responded promptly, but said he couldn't help because most of it he found randomly and the stuff that was made custom wasn't actually made by him, just given to him for final assembly.
     
  35. LDR

    LDR Sr Member

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    Thats a shame.

    Was worth a try anyway.
     
  36. Risu

    Risu Master Member RPF PREMIUM MEMBER

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    Yea. The pictures will come in handy. Knowing now how much wider the top light box is than the one I scratch built actually helped me figure out how they made the thing fit the helmet. The respirator has an abnormal shape on the top that totally messes up the curve. I thought the box was 1.75" in the back, but it looks like it's actually closer to 2.5", which means to make the whole thing work they probably just removed the entire bulging section and used the light to cover up the hole.
     

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