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  1. NovaDom's Avatar
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    Dec 27, 2013, 10:52 PM - Strengthening Pepakura: Bondo, Rondo, Resins (Polyester, Epoxy, Urethane) +Fiberglass #1

    Hello guys, first time poster here!

    I've been on the board for about a month now and I've been reading pretty much everything I could about Pepakura.

    I think I'm about ready to begin playing with Pep and, like so many others before me, I'm trying to plan what material I need before jumping in.

    Alright so, putting aside the obvious (cardstock, scissor, exacto, glue, etc), I'd like to know if I'm on the right track with the "chemicals" used to harden the outside, then the inside of my Pep parts..

    I never used or owned any of those products before.

    Here the summary of what I understood:
    (I've read to stay away from water based resin for Pep parts, so that's why I'm not referring to them at all)

    Ok so, Bondo is a (car putty) filler, polyester based.
    Rondo is the result of polyester resin mixed with bondo.
    I'd like to know if Rondo is only "doable" with polyester resin?
    From what I read, polyester resin stink pretty badly (still smells after its cured.. bad for a helmet).
    I'm guessing that the reason that both chemicals mix no problem is because both products are polyester based.

    So, especially for the smell "problem", I'm leaning toward Epoxy resin for the inside of my Pep parts.
    I know that it won’t be a problem to use fiberglass cloth with epoxy resin for my "strength" layer..
    But I'd like to try "slush casting" the first layers inside the Pep parts..
    So, basically I'd like to know what would happen if I mix epoxy resin and bondo to create an alternate type of Rondo ? Am I thinking too much about this, and it’s going to work no problem?
    Or am I looking at an epic failure waiting to happen?

    When researching about slush casting or rotocasting, everything I read is either about rondo, or urethane resin.
    My gut feeling tells me that if Rondo (made with epoxy resin and bondo) is doable, it would be stronger than slush casting urethane. I can totally be wrong, that's why I'm looking for the expert knowledge of the RPF users!

    Like I said before, slush casting would be the first layer inside, then fiberglassing.


    Now, that would cover the strengthening of the inside of my Pep parts..

    For the outside of the parts:
    I'm leaning toward Urethane resin. From what I've read, urethane resin can be applied very thin to give some strength to Pep parts, but can also be used to cast solid pieces.

    For example; let’s say I'm building an Iron man helmet..
    I could do the actual helmet in Pep, but I could cast the "ears" in solid urethane, and then install them on the helmet.

    Am I somewhat on the right track?

    I should say that while shopping online, I've came across polyurethane resin and urethane resin.
    I have assumed that they are the same thing. Please correct me if I'm wrong.


    Should I expect so type of weird reaction between the urethane resin and the epoxy resin / bondo & fiberglass combination?

    Am I complicating things for nothing and should just stick with epoxy resin, applied all over the parts with a brush, then fiberglassing?

    Your comments are very welcomed
  2. KamikazeBr's Avatar
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    Dec 28, 2013, 8:55 AM - Re: Strengthening Pepakura: Bondo, Rondo, Resins (Polyester, Epoxy, Urethane) +Fiberg #2

    I would not mix two types of resin! They usually have different drying time and use different catalyst.

    In my pieces I like to apply a layer of resin inside and out. To prevent paper deforming. Like most resins shrink a little when dry, if the two sides together dry, decreases the risks!

    Regarding the smell of the polyester resin, the smell with time decreases greatly.


    Hope can help you!
  3. Member Since
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    Dec 28, 2013, 12:44 PM - Re: Strengthening Pepakura: Bondo, Rondo, Resins (Polyester, Epoxy, Urethane) +Fiberg #3

    Bondo or polyester putty almost smells as bad as polyester resin. Maybe polyurethane resin might be a solution. Not really sure if that's ideal for paper pep though.
  4. mdb's Avatar
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    Dec 29, 2013, 10:33 PM - Re: Strengthening Pepakura: Bondo, Rondo, Resins (Polyester, Epoxy, Urethane) +Fiberg #4

    Don't mix! But you can make your own rondo from Epoxy.

    Epoxy resin with a little tissue/matting soaked in it til it gels then mix through some microballoons/fairing powder, voila! My videos of doing this are bad bad bad as I had to resort to my netbook's webcam. But it's a very light and tough material. I tried to break off excess from my wig head and failed.

    There are dyes, pigments, matting/cloth etc. and fillers (even a glue powder) and it has just enough flex when cured to avoid any issues with breakage- my Shae Vizla helmet bounces off hard surfaces, it's resin and cabosil slushed then backed with cloth. It winds up pretty much being comparable to real armour when used right.
    neimhaille-female turian- mass effect | The Plain Jane Costume Chronicles
    shae vizla | The Plain Jane Costume Chronicles
  5. laxman09's Avatar
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    Dec 29, 2013, 11:50 PM - Re: Strengthening Pepakura: Bondo, Rondo, Resins (Polyester, Epoxy, Urethane) +Fiberg #5

    I typically just resin the outside with one layer, then one layer of resin on the inside. then i go back on the inside with a fiberglass mat coat, and another layer of fiberglass mat over that one. that usually makes it nice and strong. Not really cheap or the lightest, but it wont break on you!
  6. RPF Premium Member Blaxmyth's Avatar
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    Wanganui, New Zealand
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    Dec 30, 2013, 12:30 AM - Re: Strengthening Pepakura: Bondo, Rondo, Resins (Polyester, Epoxy, Urethane) +Fiberg #6

    I am limited to using polyester resin due to the cost of epoxy here in New Zealand, but it's a good starting point as you can get a lot more experimenting done for a lot less outlay. I suggest using your first pep project as an experiment and not worrying too much if it does not turn out perfect.

    My current preferred method is to
    (1) Stiffen the outside of the pep with two coats of resin, just to make it easier to handle without distorting its shape.
    (2) Next I use car polish - the runny paste type - and brush it all over the inside of the pep, waiting for a day or so for it to dry out properly. I check by brushing the inside with a dry cloth, just in case of bits in the corners that have not yet dried.
    (3) make a 50/50 mix of bondo and resin (known as rondo), stirring it well and using the resin hardener to kick off the reaction. I pour this inside the mould and rotate it round by hand until it has set sufficiently to not pool in the bottom. Usually need a couple of applications.
    (4) Next is to apply a couple of layers of cloth or mat all over the inside. I try to do several helmets or pieces at once, so I can get the rondo and fibreglass all done in the one day. This is because the finished item will shrink away slightly from the inside of the pep, and also because polyseter does not adhere well to itself once it has cured past a week or so.
    (5) Lastly I peel off the pep card, leaving the rondo as an exposed outer surface, which I can then sand and buildup with bondo where necessary.

    This method is one I have evolved over a couple of years. It works for me, but most others leave the card in situ and apply bondo over the top. Comes down to personal preference, but the whole process allows lots of variation.

    One thing to insist on is using a decent carbon-filter gas mask certified for organic vapours for the whole time you're dealing with the resin. Otherwise you will cough continually for about 36 hours. (Another thing I learned the hard way.) The smell does diminish after a couple of days as the solvent(?) evaporates out of the hardened resin. If you can work outside, that's good too, or in a shed away from the house. I use a sealed cabinet heated by an 80 watt light bulb in the cooler months, which gets the temperature up to about 30 degrees Celcius, allowing the resin to harden nicely in about an hour.

    Anyway, dive in and have a go - epoxy if you can afford it, polyester if you're on a budget like me. You're in for a lot of fun either way! Cheers!
  7. Member Since
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    Dec 30, 2013, 7:43 AM - Re: Strengthening Pepakura: Bondo, Rondo, Resins (Polyester, Epoxy, Urethane) +Fiberg #7

    I did a stargate horus guard helmet for last halloween and slushed the inside with a hybrid Rondo.
    Speak Polyester based car putty and epoxy resin.
    Didnīt have any issues with it. Just make sure you first mix the parts individually, the Bondo and the epoxy resin. Then mix the 2 parts together for your rondo. This way both parts get their related activation and the final product is thoroughly hardened.

    The helmet was a fast build, made a week before halloween and I just had epoxy resin at home. now itīs on display. up until now itīs strong and remains itīs original form. And I donīt think that will change
    Last edited by benjaminvegeta; Dec 30, 2013 at 7:49 AM.
  8. NovaDom's Avatar
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    Dec 30, 2013, 8:42 AM - Re: Strengthening Pepakura: Bondo, Rondo, Resins (Polyester, Epoxy, Urethane) +Fiberg #8

    Thank you for your inputs!

    I think I'll simply go with epoxy resin (and fiberglass cloth) for now..

    It's going to be simpler to learn if I use only one type of product at a time.


    There IS a price difference with polyester resin, but the smell of the finished part is important to me.

    I have a helmet which was done with polyester resin and fiberglass (made by somebody else, at least two years ago).. and the smell still bothers me


    I don't have a finished part done with epoxy resin to compare, so I can't be sure.. but it is many people's opinion that epoxy resin smell isn’t as bad as polyester's


    I'm pretty sure I'll try slush casting in the future, but I guess that every product and every technique has its own learning curve..

    I'm just really excited to try them all! :P


    benjaminvegeta: I'll keep your "recipe" in mind for "hybrid rondo", thank you
  9. Member Since
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    Dec 30, 2013, 9:31 AM - Re: Strengthening Pepakura: Bondo, Rondo, Resins (Polyester, Epoxy, Urethane) +Fiberg #9

    Hey everybody I have done nothing but foam builds since i started pep and I really want to move forward and do a resin, fiberglass, and bondo build. I do need to ask though what are the best and easiest to use bondos and resins?
  10. NovaDom's Avatar
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    Dec 30, 2013, 10:10 AM - Re: Strengthening Pepakura: Bondo, Rondo, Resins (Polyester, Epoxy, Urethane) +Fiberg #10

    I can answer with what I learned while reading, altough I never used any of those products before..

    Bondo is actually a brand name.. most people, when they talk about Bondo, actually mean Bondo auto body filler putty.
    I mention it because it was faily confusing for me at first, since the brand Bondo sell all kind of product, including resin, filler, glazing and spot putty etc.

    I know that Bondo (the auto body filler) isnt available worldwide .. so depending on where you live, you might have to look for another product that does the same thing. There's obviously other brands that offer auto body filler, you just need to look for what's available to you locally.

    for resins, the cheapest is "regular" fiberglassing resin (which is really polyester resin). (Supposedly, it smells horrible - and shrink a little - when drying).

    other choices could be epoxy resin (a bit more expensive - supposed to not shrink as much when drying), water-based resin (like Aqua-Resin brand, people says its not the best solution as it tend to deform Pep models), etc

    I only read of a couples of persons who used urethane resin to strengthen Pep models, so I guess its not a really good choice for noobs like you and me!


    There are other alternatives too (you can find them using the forum search function), but the one I listed here are the most widely used.

    Hope that helps!
    Last edited by NovaDom; Dec 30, 2013 at 10:23 AM.
  11. Member Since
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    Dec 30, 2013, 1:43 PM - Re: Strengthening Pepakura: Bondo, Rondo, Resins (Polyester, Epoxy, Urethane) +Fiberg #11

    Wow thanks for your help man!
  12. RPF Premium Member Knowone251's Avatar
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    Dec 30, 2013, 3:38 PM - Re: Strengthening Pepakura: Bondo, Rondo, Resins (Polyester, Epoxy, Urethane) +Fiberg #12

    Ok, so a big warning to anyone using polyester based resins and fillers! The "stink" from them is actually a harmful vapor that causes nerve damage. It is also has an accumulative effect in the body. Multiple small exposures over the course of time will cause damage, and can even lead to serious allergic reactions. When using these products, ALWAYS wear an respirator rated for organic vapors, and give the pieces plenty of time to cure before wearing them.
  13. RPF Premium Member Knowone251's Avatar
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    Dec 30, 2013, 3:58 PM - Re: Strengthening Pepakura: Bondo, Rondo, Resins (Polyester, Epoxy, Urethane) +Fiberg #13

    Oh and it absorbs through the skin, so wear gloves. Urethane resins will work just fine for hardening pep, but they tend to be the most expensive of the 3. If you have a Hobby Lobby near you, get their smart phone app. It always has a %40 off coupon, and they sell big bottles of the 5min and 30min two part epoxy resin. If you don't have a dedicated workspace, I would suggest using these over polyester resins. Still need ventilation, but not as toxic. For smoothing and surface work, both Elmer's and PC sell a two part, epoxy based wood filler that has over an hour pot life, 24 hour cure, no shrink, and sands really easily.

    http://amzn.to/1kWylKP
    http://amzn.to/19WLoYp
    Last edited by Knowone251; Dec 30, 2013 at 4:11 PM.
  14. Member Since
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    Mar 22, 2014, 7:13 PM - Re: Strengthening Pepakura: Bondo, Rondo, Resins (Polyester, Epoxy, Urethane) +Fiberg #14

    Knowone251 said: View Post
    If you have a Hobby Lobby near you, get their smart phone app. It always has a %40 off coupon, and they sell big bottles of the 5min and 30min two part epoxy resin. If you don't have a dedicated workspace, I would suggest using these over polyester resins.
    Hi Knowone251 - have you used those Hobby Lobby epoxy resins for a pep build before? I'm asking because I am working on my first project and don't want to invest in the Smooth-On brand stuff just yet. Thank you.
  15. Tinman's Avatar
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    Mar 22, 2014, 8:37 PM - Re: Strengthening Pepakura: Bondo, Rondo, Resins (Polyester, Epoxy, Urethane) +Fiberg #15

    If your looking for some extra strength, what i like to do is take some basic 1/8 in thick acrylic from Home Depot and break it into 1/2 wide strips. Hit them with a heatgun and (with gloves on) lay them inside your armor while its malleable, pushing it into the contour of the piece, and let it harden again. Then hot glue it into place over top of your fiberglass layer. I do this a sort of "H" pattern inside say, a breastplate or something, and it gives me a nice strong bracing inside, for added strength.
  16. RPF Premium Member Knowone251's Avatar
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    Mar 24, 2014, 11:19 AM - Re: Strengthening Pepakura: Bondo, Rondo, Resins (Polyester, Epoxy, Urethane) +Fiberg #16

    ChikSolo said: View Post
    Hi Knowone251 - have you used those Hobby Lobby epoxy resins for a pep build before? I'm asking because I am working on my first project and don't want to invest in the Smooth-On brand stuff just yet. Thank you.
    Yes I have, here is a pick of a cowl I'm working on. I used both West Systems epoxy and the 5 min epoxy, along with some burlap for strength.
    Click image for larger version. 

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  17. Member Since
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    Mar 24, 2014, 1:36 PM - Re: Strengthening Pepakura: Bondo, Rondo, Resins (Polyester, Epoxy, Urethane) +Fiberg #17

    Thanks for the reply - good luck finishing your cowl!
  18. Member Since
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    Mar 29, 2014, 10:08 AM - Re: Strengthening Pepakura: Bondo, Rondo, Resins (Polyester, Epoxy, Urethane) +Fiberg #18

    Hey guys, i just want to say that the non- toxic aqua resin type brands will not deform your pepakura if you do a couple of layers of spray on clear coat to seal the paper, as aqua resin is water based.

    - - - Updated - - -

    Also if you have a hollow piece, like a thigh or forearm, it would be a good idea to use something like a balloon to keep its general integrity.

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