Resin Procedure Question

[Sdgibbs]

Ok so i'm just about done with my first pepakura and i wanted to make sure i was going to be doing the next step right after putting so much time into it.

I know the difference between resin, bondo, and rondo as well as poly vs epoxy but there are a few things i've seen differing instructions on and I want to know if as of today there is a generally accepting "best practice"



1) Someone said don't do an entire coat of resin at once because it will weaken the structure instead divide it into sections, however from what i've seen this applies to large objects like chest pieces, not a helmet correct?

2) Both epoxy and poly heat up and can stress the paper foundation if done carelessly?

3) Only mix epoxy based resin with epoxy based bondo, and poly based resin with poly based bondo right?


Any last advice? Thank you. Picture attached

 

[Meatwad]

1) Even smaller projects, such as a helmet, can warp under the weight of a coat of resin. Not only are you wetting the paper, weakening it, but you're also adding weight. I've seen people split the areas on the helmet into quarters and do 2 opposite sections at a time.

2) The curing process of both does produce heat, but this brings us back to point #1. Moisture + paper + excess weight = warping. I've always started with a very light exterior resin coat followed by a thickened coat on the inside.

3) That is correct. Do not mix bondo with epoxy resin. As far as i know, there are no epoxy body fillers, though i could be wrong. I have seen people mix bondo with epoxy resin, but it tends to end in tragedy more often than not.

 

[PerniciousDuke]

Sweet helmet! I can only offer advice on the first question since I have poly refined and fiberglassed a chest and helmet with great success. You don't need to do partial coats on the helmet. You do need to do as thin of a coat as possible and use supports in areas that might sag (popsicle sticks and those black bendable paper clips work really well). I would also recommend working in 1oz batches of the resin.

Also note the new recruit sticky that has links to Help! Threads where questions like this should be posted instead of creating a whole new thread.

Best of luck and I hope you find the answers you need.

 

[Sdgibbs]

Awesome, thank you for the help!

 

[PerniciousDuke]

I do agree with Meatwad, thin coat on the outside then once that's hard go to town on the inside. I found Cereal Kill3r YouTube channel to be really helpful on this part. He described it as making it "look wet" on the outside, where as on the inside you want to "saturate" the paper.

 

[peterthethinker]

Yup Leave 2part epoxy for just fiberglass .

also be aware the bondo brand polyester resin has wax in it. If you do lay any thing on it beside more polyester based stuff use some iso and some pads and remove the wax.

2 part epoxy does not adhear very well to a poly resin item.

* the reverse is not a issue*


Peter

 

[Sdgibbs]

also be aware the bondo brand polyester resin has wax in it. If you do lay any thing on it beside more polyester based stuff use some iso and some pads and remove the wax.
Peter

Dumb question, does this include paint primer?

Also if I rondo the inside should do fiberglass on the inside? Or just resin the inside, let it set, then rondo?

And if I were to do fiberglass it goes resin, dry, resin + fiberglass dry correct? I don't use fiberglass in the first inside coat do i?

 

[peterthethinker]

Ive not done a full peped suit .. only parts for a friends armor . My data on the wax is based on boat work I did in College.

The stresses we see in armor are not as bad as in a raceboat so the issues with super duper proper adhesion and wax may never be a issue in our use in armor.

Still, its good practice to prep all stuff .

There is no real harm in a good isoprpol wash when you are ready to prime and paint .




Rondo is a void filler mostly.

you can add it after you fully cure the outside and also inside coats.

so here is how I did a pepped part:


so you first coat the outside lightly!
just enough to add some ..not soak. let dry
then you coat the inside. let dry

then lay a coat in the inside and lay the glass and then add more resin to fully wet the glass. this is one full step
by pre coating it it helps hold the glass in place and also assures you fully wet the glass.
at this point you can shape the outside with bondo.

If you feel you wanna add more glass then ( coat glass coat )again .
you CAN add more then one glass layer at a time but its not easy. more to go wrong .


ALSO If the parts have small features you wanna re enforce you can use rondo to void fill . I prefer microballons as they are glass based and are lighter

 

[Sdgibbs]

ah ok i didnt know you used fiberglass AND rondo i assumed it was one or the other thank you

 

[FlyinPhil]

Ehhhhhhhhhhhh I used rondo as my main form of hardening, then did a 2" strip of fiberglass around the base of the helmet for some extra strength. I went with rondo because it was the easier method at the time. Were I to do it over again, I would not use rondo at all, just fiberglass. It will be stronger and lighter. Using both isn't necessary.