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Thread: Expanding Foam Tutorial

  1. #1
    Join Date
    Mar 2008
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    This is a Tutorial on basic Expanding Foam knowledge and how to incorporate it correctly into your Pepakura Weapons, Grenades, and Equipment. I've gotten many PMs asking the same question on "How to use Expanding Foam without turning my rifle into a balloon". So I thought I'd finally share my knowledge on the subject with the rest of the community. Everything in this tutorial is step-by-step.

    <span style="color:#FF0000">***Pictures will come at a later time!***</span>

    NOTE: If you&#39;ve never used expanding foam before you might want to take everything i&#39;m about to say to heart. Also, this method works with all the weapons (including grenades, and equipment).


    First thing to know, there are 2 main ways of goin about strengthening your weapon. There are some other ways to get this done that I DO NOT RECOMMEND.

    <span style="font-size:14pt;line-height:100%">Method 1:</span>

    1. Resin the outside of your COMPLETED pep piece about 6 times in light/thin coats to make it semi-sturdy
    2. Get a saw or dremel (with a diamond wheel cutting bit) and cut your weapon in half (if you are filling a grenade you dont need to do this step)
    3. Fiberglass the 2 halves on the inside about 3-4 layers, you may or may not use expanding foam at this point to fill in the cavity, there really isnt a need to since you just glassed it a few times.
    4. To put it back together just line up the pieces and epoxy them back together. I recomend an epoxy putty with a work time of 20 minutes (ex: AquaMend)

    Method 1 notes: I personally dont like to do it this way, because when you cut it in half your gonna lose some of the body and you&#39;ll have to just hope you line everythign up correctly when you put it back together... you may even have to improvise and build a "filler" in the gap between the pieces with Epoxy putty or Body Filler. It can get complicated...


    <span style="font-size:14pt;line-height:100%">Method 2:</span>

    1. Resin the outside of your pep weapon, grenade, or equipment about 4-5 times in light/thin layers.
    2. Drill a hole, using a 1/4 inch drill bit, every 10 inches on one side of the weapon (for grenades, you only need 1 hole, for equipment, depending on which one, you will need up to 2 holes, max)
    3. Using the expanding foam straw, place it into the first hole.

    Fill ONLY one section at a time!!!!!!!

    3.2. When that first section is about 1/2 full (remember this is EXPANDING foam, it is reallllllllllllly important that you dont over fill) stop and pull out the straw and let that section cure before moving onto the next one.

    And for the love of Halo, DON&#39;T fill the whole weapon with foam in one go.... you do that and you might as well kiss it goodbye.


    <span style="font-size:14pt;line-height:100%">Expanding Foam Important Information:</span> This is the most important part of Method 2

    Expanding foam cures over a 10 hour period (it says 8 hours on the can but it LIES).... therefore you need to keep your eye on your weapon, grenade, or equipment for <u>10 hours </u>. About once every 30 minutes, during those 10 hours, you need to check on your weapon (grenade, or equipment). You <u>NEED</u> to "gas-out" the foam in all your 30 minute check ups. To "gas-out" all you need to do is unbend a paper clip or get a metal BBQ skewer and poke at the curing foam, Poke it so the metal goes all the way into the foam and gently hits the other side of the weapon (grenade or equipment). When you do this you will usually hear a pop and then an escape of air. That is what "gasing-out" is.

    If you DON&#39;T "gas-out" your weapon (grenade or equipment) it&#39;s shell (resined pep)will usually first balloon outward and eventually (when the air escapes, uncontrolled) it will be vaccuumed inward and it will litterally suck itself into itself (trust me it happend with my SR and I had to repair that damage with an ungodly amount of bondo, and in the end still turned out to be an epic FAIL). After 10 hours and 30 minute increments of poking your foam, you&#39;r pretty safe to do another section of the weapon (grenade or equipment). Once your weapon (blahblahblah) if full and completely cured all you have to do is fill the holes during the next step (Bondoing). Doing it this way will be much more time consuming but the end result will be perfect.

    And just as a side note, depending on which weapon you build, you might want to make an internal skeleton using PVC pipe. For example: my SR&#39;s barrel is also my rifle&#39;s "spine", it runs the entire length of the body internally to help with structure.




    That&#39;s it for my tutorial right now, I will continue to add/edit this as time goes along, I will be updating it with step-by-step pictures soon.

  2. #2
    nice tut there kelly but where are some pics? jk i know you have them on the way....see ya soon!

  3. #3
    I have another trick up my sleeve that you might find handy!

    It&#39;s a securing method used by concrete workers when setting up a concrete wall. They use metal rods to hold the wall securely in place so it won&#39;t expand when the concrete is poured in:
    | = Wall
    --- = Rod
    <> = Pins

    ---<|--|>---
    ---<|--|>---

    As you can see, the rod and pins won&#39;t allow the wall to go anywhere. Use this same method with weapons and equipment, but a strong fishing line as Rods, thick cardboard as pins, and the Pepakura weapon will serve as the wall. Use a needle to guide the fishing line through the weapon, and tie one piece of Cardboard on one end. Now tie the other side of the fishing line with another piece of cardboard. Don&#39;t make it too slack or tight, but just so it holds it&#39;s original shape. Make the knots tight, though. Now you&#39;re ready to add the expanding Foam. After all sections have cured, just cut on side of the fishing line and pull the Line through the weapon. [img]style_emoticons/<#EMO_DIR#>/wink.gif[/img]

    Now you can experiment with this, and see if it holds up. Pre-coat your wepons with 2 layers of resin just in case. I hope everyone knows what the hell I just explained! xD

  4. #4
    Join Date
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    Putting pressure on either side doesnt always work though....unless you use a vice grip, maybe.

    I recall trying to set up some sort of system with my SR but it failed tremendously. I didnt, however, sew through my rifle....

  5. BRI great tut. I think there more application then just using it for weapons

    PSBeretta used foam for his cog chest and it help perfect

    "Yeah, the foam was the black can of "Great Stuff". Do it in sections so it dosen&#39;t distort on you. Once it dries, it hardy weighs anything. Put the tip of the straw right on the card stalk at an angle and lay the foam down in 1/4" lines.
    You can see the foam on the inside in this pic."

    post: 159
    http://405th.com/forums/index.php?showtopic=8197&st=140

    but it seams like you might be able to skip the resin step?

  6. #6
    <div class='quotetop'>QUOTE(BlacRoseImmortal @ Sep 30 2008, 06:34 PM) <{POST_SNAPBACK}></div><div class='quotemain'>Putting pressure on either side doesnt always work though....unless you use a vice grip, maybe.

    I recall trying to set up some sort of system with my SR but it failed tremendously. I didnt, however, sew through my rifle....</div>

    Aw poo... I was so sure it might work!
    Damnit...

  7. #7
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    <div class='quotetop'>QUOTE(Spartan 051 @ Sep 30 2008, 03:03 PM) <{POST_SNAPBACK}></div><div class='quotemain'>BRI great tut. I think there more application then just using it for weapons

    PSBeretta used foam for his cog chest and it help perfect

    "Yeah, the foam was the black can of "Great Stuff". Do it in sections so it dosen&#39;t distort on you. Once it dries, it hardy weighs anything. Put the tip of the straw right on the card stalk at an angle and lay the foam down in 1/4" lines.
    You can see the foam on the inside in this pic."

    post: 159
    http://405th.com/forums/index.php?showtopic=8197&st=140

    but it seams like you might be able to skip the resin step?</div>


    Yes you can use expanding foam for more than just filling weapons. It also makes a great insulator and padding. if you have room in your armor that you dont want just fill it with foam. If you have alittle excess then just cut of the stuff you don&#39;t need :]

    I just get PMs all the time about filling weapons thats all.. like i said i&#39;ll be editing and adding to my tutorial for awhile to make sure it covers everything... I just wanted to get that part up there lol

    @ S1l3nt V1p3r: it&#39;s a good odea... it might work better for very experienced people, I&#39;m targeting noobs with the basics lol

  8. #8
    Join Date
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    I&#39;d be interested to see if people would try something they could slush cast in it like Flexifoamit-25. I don&#39;t think it would have the degas problem from what I"ve seen in my molded stuff. Slightly shorter curing time I think (3 hrs).

  9. #9
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    Wow that would be great!... it does get alittle annoying having to check in on the Great Stuff expanding foam for 10 straight hours >.<

    I&#39;ll have to try that out it sounds like! :]

  10. #10
    <div class='quotetop'>QUOTE</div><div class='quotemain'>(it says 8 hours on the can but it LIES</div>

    It lieded! lol

    No , great tutorial.

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