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Unread 01-03-2013, 12:36 PM   #1
AllieFarrell
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Question Crack in fiberglass, what to do?

I recently commissioned armor; the armor was made from fiberglass. One of my stealthy kittens snuck into my off-limits closet and managed to knock it over and crack a segment of it off. I glued it back together, added something to the back to hopefully keep the crack from recurring, and sanded it down to hide anything. I thought that was that!
I was wrong
On my way back to school from winter break it broke again on the train because the person in front of me insisted having their chair at a 13 degree angle. (I brought the armor home in the first place because that is where my tools to fix it were, in case you were wondering why I'd have it on a train).

Bottom line: how can I fix this without fear of kittens or con glomps or any other thing?

I have no experience with fiberglass, hence I commissioned this in the first place.
I was considering paper macheing over it but I was unsure if that would stick on plastic.
Can anyone suggest something to reinforce this thing?

Also, I'll attach two pictures so you can conceive of what I'm working with. The part that is white-ish, is where the crack was, which has been sanded down.
http://i94.photobucket.com/albums/l8...psa38b2f74.jpg
http://i94.photobucket.com/albums/l8...ps3230988a.jpg
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Unread 01-09-2013, 03:05 PM   #2
StabbityBlkMage
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Working with fiberglass is exactly like paper mache. Just toxic.

Buy: Fiberglass resin, fiberglass mat or cloth (I would prefer cloth for this application), paint brushes, disposable cups, latex gloves.

Apply fiberglass resin (follow the directions on the can for catalyst to resin ratio) to the piece. Get it wet. Apply pieces of fiberglass cloth to the repair area. Paint resin over that. Done.

I suggest only putting it on the back since this sort of repair will most likely not look particularly pretty.

I suppose the easiest way would be to get some apoxie sculpt (http://www.avesstudio.com/index.php?...chk=1&Itemid=1) then just apply it liberally to the back over the crack, and then very smoothly on the front over the crack to close the seam. In all honesty since the crack is on such a small piece I'd do it there. And since I assume that this is an Asuka chest piece it needs to be very flush to your chest for the plugsuit.

TLDR. Use apoxie sculpt. It's awesome.

The blade in this picture was sat on and broken, but fixed with apoxie sculpt and sanding.



xoxo
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Unread 01-09-2013, 05:29 PM   #3
verdatum
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Ouch. A properly made fiberglass piece shouldn't crack that easily. And even if you do manage to damage it, the fiber reinforcement should prevent any damage from spreading. Have you tried contacting the builder? They might be willing to repair/reinforce it for little or no charge beyond shipping.

Assuming that isn't the case, I agree with StabbityBlkMage. Though you don't need to purchase a whole tub of Apoxie for a small fix. Hardware stores sell small tubes containing about 2oz of epoxy putty to use for household repairs. It's in the adhesives section. It works pretty much the same as Apoxie, only it has a faster cure time once mixed, usually something like 15 minutes.

For repair situations, instead of trying to smooth the putty while pliable, I prefer to apply it with just a fraction of a milimeter of excess. Then once it hardens, you can sand it perfectly flush.
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Unread 01-11-2013, 06:43 PM   #4
Wolfmagicx
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I have had to rebuild lower side fairings on a few sport bikes i have had over the years, the way i did it on the cheap was sand the back of the 2 parts rough ( at min 2 inches beyond break) with like 80 grit paper. then used painters tape on the front to hold the parts in place while i covered the cracks and at min 2 inches around the break with fiberglass mesh tape. then mixed up some jb weld and coated the mesh tape smooth and let set for 24 hrs. then fix paint and other stuff. that repair worked and held on a bike that was not unusual for me to be going 130mph+ so its durable, tip though the more strength extend out to like 4 inches http://www.walmart.com/ip/J-B-Weld-Cold-Weld-Compounds-j-b-weld-skin-card/19283655?ci_src=14110944&ci_sku=19283655&sourceid= 1500000000000003260430
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Unread 01-12-2013, 05:10 PM   #5
AllieFarrell
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Quote:
Originally Posted by verdatum View Post
Ouch. A properly made fiberglass piece shouldn't crack that easily. And even if you do manage to damage it, the fiber reinforcement should prevent any damage from spreading. Have you tried contacting the builder? They might be willing to repair/reinforce it for little or no charge beyond shipping.
Verdatum...oh gosh. Let's not even get into that XD. When I contacted the builder, I was told to "super glue and paint over it", and that "any kind of paint would do". Now mind you that, although I don't frequent cosplay.com often, I have been cosplaying for ~8 years, and I was very open in telling the builder I was willing to sand/buy appropriate resin/glue/etc to fix the piece if they were unwilling to send a new one....but nope, super glue and paint...that's my magic bullet apparently .
Anyway....

Because this post went through a spam filter and I did not receive replies for some time I took matters into my own hands and bondo'd both the left cracked side and its right counterpart, front and back on both sides. (If this was a huge mistake, please don't rub it in, haha ^.^; as I said I'm new to fiberglassing). Would you all still recommend apoxie sculpt? Ironically, the side that did not break now appears to be increasingly weak; I guess because it doesn't have any reinforcing cheese cloth behind it, like the side that initially broke does.

Also, another question, somewhat off topic but now inevitably relevant to my piece, is it unwise to use spackling paste to fill small gaps in bondo that sanding just doesn't seem to get rid of? A carpenter friend of mine suggested that but I felt unsure.
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Unread 01-12-2013, 07:07 PM   #6
Millions_Knives
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lol
"Working with fiberglass is exactly like paper mache. Just toxic"
so basic but true
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Unread 01-12-2013, 09:45 PM   #7
StabbityBlkMage
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I've never personally used spackling paste. I've always just used bondo, sanded the crap out of it, then used Rustoleum's Filler Primer to take out the remaining little bubbles. As per 3M's "system" they have some sort of putty I've never really messed around with, but you can try that if you want. It has it listed on the can as part of "3M's car restoration system" or some nonsense.

Yeah apoxie sculpt should still work, stuff sticks to damn near anything. I think you should be fairly liberal with your apoxie in order to make it more durable. The red is your broken piece and the gray is the apoxie sculpt. Have it lead slightly over the crack, and you should be able to sand it to a nice gradient on the top so that it matches well with the rest of the armor.



From a physics standpoint this should be stronger. I won't go into detail, but it's essentially about counteracting shear forces and bending moments equally regardless of applied loading. I'm an engineer by trade, so this is what I specialize in.

TLDR use apoxie sculpt. Use a lot of apoxie sculpt. It's awesome.

Good luck to you!!!

PS. I guess to just spit in their face you could always repair the crack, then make a mold and recast the entire thing. Totally viable since they already did the hard part (the sculpt) and making molds / casts is just following directions on the back of a bottle.

www.smoothon.com has a ton of vids if you want to do that. I learned how to cast entirely on the internet, so it's doable.

But yeah might be overkill hahahaha.
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Last edited by StabbityBlkMage : 01-12-2013 at 09:48 PM.
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Unread 01-13-2013, 01:36 AM   #8
verdatum
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What you did with the Bondo was perfectly reasonable. A better product would've been that other variety of bondo that has the fiberglass strands mixed in...well...sorta better. That stuff destroys sandpaper, so you kinda apply it more minimally, and then slap regular bondo over that to get a surface that can be sanded smooth. But I digress.

Superglue then paint actually can work for small cracks. There are just a couple problems with it. It tends to be far too thin to use for very much beyond a hairline crack. Most formulations are designed to seep into cracks via capillary action, so you'll often get a concave surface. You want a convex surface that you can sand smooth. The problem here, is that even if you do get a convex surface from superglue, the stuff is very hard when cured. Harder than the fiberglass resin. So when sanding, it is very easy to start sanding away at the fiberglass resin when you mean to be sanding the superglue flush.

Spackling paste is a little less flexible than the bondo or epoxy clay. But for small asthetic cracks, it can be used.
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Unread 01-13-2013, 12:33 PM   #9
AllieFarrell
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Do you guys have a specific primer filler you recommend? RustOleum punches you in the face with options..
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