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Unread 08-22-2017, 03:54 PM   #1
walkerofdarknes
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Material change.

So after my costume suffered...well, catastrophic results from the heat and sun, I need to rebuild it. Because it bugs me to death not having the costume to show for a lot of work put into it. Here's a pic of it:

https://thewalkerofdarkness.devianta...im-2-697625150

Now I know I can trim it up some because of the open space in there (you can't see it, but there's about 2, maybe 3, inches separation around me and the costume and more in different spots). But at the time, I used mostly EVA foam and corrugated plastic. Maybe it caused the failure, I'm not sure. I blame the environment.

To break down the costume completely, there's a backboard of double-thickness corrugated plastic with straps, plus 2 inverted-L connectors to rest it on my shoulders. The front section is connected to the back at the top (if you look at the pic, it's the green crossbars under the helm) and lower sides by velcro (where the silver midriff is).

Having given the TLDR version, on to my questions:

1. I know I'm going to have to redo the backboard. I'm debating between using sintra or balsa wood. Would sintra have enough rigidity to let it support....probably upwards of 30 pounds (maybe more, I never weighed myself in it) in that configuration? What kind of weight difference might there be in using one or the other?

2. If you carefully look at the right side shoulder (it's on the left in the picture, holding the gun), you can see the shoulder pauldron dislodging the support. Would that still happen happen with sintra, or would I need the balsa for better support (there's actually additional pieces missing from the design, long story short, it would have probably failed sooner)?

3. I do have some pieces that I can salvage from the old costume during the rebuild, but would there be an inherently visible difference in alternating the old materials with the new ones? I'm not against using all the new material, but I'd love to save what I can and use it for additional projects later on.

4. For something of this...scale for lack of a better term, if not sintra/balsa, then what?
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Unread 08-24-2017, 07:52 AM   #2
Penlowe
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Plastics will always be affected by heat. The specific ones you worked with are not very warp resistant under those conditions.

You have a few options:
I can't speak to sintra as I haven't used it.

wood: you can buy 'cabinet veneer plywood' (also called Luan- a brand name) which is a 1/4" thick plywood with REALLY nice smooth surfaces. As it's very thin, it does warp, but because it's wood you can un-warp it with a little moisture and some weights and time.
Balsa sheets sold in craft stores are not structurally sound at the sizes and weights you need them to be. Those same craft stores sell the above mentioned Luan in smaller pieces and greatly exaggerated prices, buy it at the big box home improvement store in full sheets. I bought a 1/4 sheet recently (2' x 4') and it was $8? not terribly expensive.

cardboard: strangely enough, this might be a better choice. Provided your corners and joins are strong enough/ well strengthened underneath this might be both easier and cheaper with the same end result. Just start with really good large boxes*

*Michael's frame shops get really nice large boxes Monday through Friday. Call in the morning and they will (usually, most framers are pretty nice) save you one. Just get it the same day, their policy is to break down everything and get it in the compactor before close.
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Unread 08-24-2017, 12:39 PM   #3
nathancarter
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Sintra will work for the structural components. You'll need to be careful to design it in a way that makes sense, but it'll work. You'll need 1/4" material at least, and might even scale up to 3/8" for the pieces that need the most structural rigidity. You might also add reinforcements of some sort to minimize flexing - inch-wide strips of 1/4" Sintra, or even aluminum strips. For non-structural components you can use 1/8" (3mm) Sintra, or even the 2mm or 1mm stuff for just decorative layering.

Unlike EVA, you can drill and bolt directly into Sintra. You can screw into it too, but I wouldn't do that for any real structural components: The PVC foam is a little bit soft and the threads may pull out. Bolting through it with a machine screw or carriage bolt, and washer and locknut, will give you plenty of structural strength.

You can glue it with high-temp hot glue or cyanoacrylate (krazy glue, super glue, etc). The hot glue works better for adding volume where your mating surfaces don't precisely line up, but you always run the risk of hot glue softening of you leave pieces in a hot car (never use low-temp or dual-temp hot glue). Cyanoacrylate requires your parts to line up more precisely, but will result in a more permanent bond. For structural joins that will be under significant stress, use a combination of glue and a mechanical join (screws, bolts, nails).

For straps, I use nylon or cotton webbing, construction staples, and Dritz heavy-duty snaps. Use a combination of cyanoacrylate and a small screw (computer case screw or an assembly screw out of a plastic toy) to secure the male side of the snap directly into 1/4" Sintra, and use the snap setting tool to put the female side of the snap into your strapping. You can also use 1/4" staples to glue and staple the webbing directly to the Sintra - the thickness of the webbing will prevent the staple from poking out the other side of the Sintra (test first, of course). Glue+staples will be a stronger bond, but a single snap will allow some rotational movement while still holding the snap securely.

See this photo and the comments on it for using a snap to secure your strapping (should all be public, let me know if not):
https://www.facebook.com/photo.php?f...type=3&theater
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Last edited by nathancarter : 08-24-2017 at 12:42 PM.
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Unread 08-25-2017, 06:45 AM   #4
walkerofdarknes
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When you say 1/4" and 3/8" you mean the 3mm and 6mm boards?

The straps I had were some industrial cargo straps (found a pack of them cheap at the hardware store) that I had sewn parachute clips onto (like your straps head).

What really failed in my build was that I had used corrugated plastic and I think, hot glue. I'm not sure if you've used/seen corrugated plastic, but it looks exactly like cardboard except for its material. The hot glue probably didn't have enough surface area to maintain a hold. Or else it just died from a very, very hot and humid day. (To describe my failure completely, if you take your two hands and hold the fingertips together at a L shape, that's the shoulder supports that separated right along those lines.)

Is there going to be a visible difference in painting the sintra versus keeping the old pieces made from EVA foam? I'd hate for it to look "patchwork" in the rebuild, and will need to know if I need more material than I plan on now.
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Unread 08-25-2017, 09:02 AM   #5
Penlowe
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oooohhhhh I see.

That was not a materials fail of the corrugated plastic. I was a glue and engineering fail.

That means you can separate the sections, use better glue and reinforce the joins, and not need to completely rebuild from scratch. A little touch up paint, but not much more than that.

So, first: find the correct glue.
Second: determine what kind of reinforcing material you need/ Maybe cardboard, maybe even fabric. Something to adhere to and overlap the inside of each major seam or join where the sections come together.

Did the shoulder section sit directly on your shoulders? or is there something like shoulder pads underneath? Attaching the costume to a simple shoulder pad will reduce torque put on the costume by normal movement when wearing it. Recycle some of these cheap knee pads as that kind of buffer part.
https://www.walmart.com/ip/Tommyco-N...epads/16879692
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Unread 08-25-2017, 10:31 AM   #6
walkerofdarknes
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The supports did sit directly on my own shoulders, with a marginal curvature of more corrugated plastic to provide some additional support for me and help secure the pieces together. BUT, the corrugated plastic pretty much offered only....gods, a pencil mark's worth of contact, even dumping as much glue as I could into it. If I had to guess, there was maybe 1mm of connection between the two points from the shoulder and the board.

I did end up laying some self-adhering vinyl across all of the corrugated plastic to help reduce the "wavy" appearance (when I test painted some pieces, you could see stripes where the thicker lines of plastic were). As for glue, I had tried liquid nails, superglue, E6000 and a couple epoxies. The high temp hot glue was about the only thing that held, and all of them had a strong tendency to fail on the edge tests (because the corrugated plastic has so many holes you get a very slight contact on an edge, literally, it's like gluing cardboard on an edge). But it still failed after the heat and humidity in the area. Which is why I was thinking of using different materials, to remove the problems with the corrugated plastic. The sintra or wood would at least be solid pieces necessary to let it bond better, wouldn't it?

As for repairing over rebuilding? At this point, both supports are ruined, the chest section is questionable, parts of the backing suspect and some of the overall elements NEED a redesign. About the only parts I can use are certain armor pieces (not pictured) the arms and maybe the helmet with some repairs. I figure that I can trim down something like 10-20% off the size of the costume at a whole. And address the flaws I made in the first build. Hence the option of changing my materials.
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Unread 08-26-2017, 07:31 AM   #7
Penlowe
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Quote:
BUT, the corrugated plastic pretty much offered only....gods, a pencil mark's worth of contact,
That is the engineering failure I referenced. The reinforcing layer needs to be something that provides large scale contact/
I've somehow over used the ability to post attachments but I'll see if I can find a picture to link.
http://www.ripsdiy.co.za/woodjoins.shtml

Ok those are wood. What you did was a Butt Join, but because of the material it was weak. Scroll down to the bottom where it says "strengthening joints" that's what you need to do.
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Unread 08-26-2017, 04:08 PM   #8
walkerofdarknes
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Yeah, I did a variation of the angle brace on mine. The glue still failed enough to let it all come apart. I didn't think of putting dowels in every (or even every other) hole, but I'm not sure how much that would have helped. Or where I could find enough dowels the right size to fit in a 1/4" slot. And truly, even though I told the judges at the contest repeatedly it was corrugated plastic, they kept calling it cardboard. So a material change is justified in the mark 2 of this costume.
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Unread 08-29-2017, 12:44 PM   #9
nathancarter
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Quote:
Originally Posted by walkerofdarknes View Post
When you say 1/4" and 3/8" you mean the 3mm and 6mm boards?
1/8" = 3mm
1/4" = 6mm
3/8" will be 9 or 10mm.

The 1/8" is easy to work with, less weight (obvs), and less expensive, but not extremely sturdy. Use it for any non-structural, non-supporting pieces.

Quote:
Originally Posted by walkerofdarknes View Post
Is there going to be a visible difference in painting the sintra versus keeping the old pieces made from EVA foam? I'd hate for it to look "patchwork" in the rebuild, and will need to know if I need more material than I plan on now.
It may be different. It depends on how you prepared the EVA foam's surface before painting.


Quote:
Originally Posted by walkerofdarknes View Post
As for repairing over rebuilding? At this point, both supports are ruined, the chest section is questionable, parts of the backing suspect and some of the overall elements NEED a redesign. About the only parts I can use are certain armor pieces (not pictured) the arms and maybe the helmet with some repairs. I figure that I can trim down something like 10-20% off the size of the costume at a whole. And address the flaws I made in the first build. Hence the option of changing my materials.
It ain't my money or time, but in the long run you'll likely be way happier with a complete rebuild using the right materials and a more appropriate scale.

You can heat-form a 90-degree angle in a single sheet of Sintra, instead of doing a butt join. For a long straight angle you'll need to form it over a buck or guide of some sort (the edge of a countertop will probably work just fine). Or you can use a combination of glue and mechanical fasteners such as little metal L-brackets, to make a sturdy angled join between two pieces.

If you're heat-forming an angle, and you need your left and right sides to be identical (but mirrored), make sure to cut them from the same direction of the material - exactly like cutting pattern pieces out of a sheet of folded fabric, you want the nap and the grain of the fabric to be identical (but flipped horizontally) for the left and right sides.

I found out the hard way that Sintra has an invisible internal "grain" from the extrustion/manufacturing process, and as you work it with heat, it will very slightly shrink along one axis and expand along the others. This is mostly imperceptible, but can be noticeable if you cut two identical shapes from two different directions of the material, then try to identically heat-form them.
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Unread 08-30-2017, 10:48 PM   #10
walkerofdarknes
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So if I sandwiched some 1/4" into 1/2", it'd be good enough for the structure?

As for money...well, I found a place that quoted me a price of $29 for a 4'x8' 3mm. When I go to pick it up, I can always get a thicker piece or two while I'm there.

And about the EVA foam...I didn't really prepare the foam. Which might have hurt some of the color. I just cut it, applied some compound joint on any seams I really didn't like even after grinding them, and then spray painted it. Should I have done something else to make it more...metallic in appearance?
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