Epoxy Resin over Bondo?

[Pyrotechx]

Here is the issue I am currently trying to solve. Basically I have taken a foam helmet, covered it it epoxy resin, and then bondo'd over that. I did NOT cover the inside of the helmet with resin, so it is still foam.

I am about to cut the visor out and now I am stuck with the thought that removing that much visor might give the bondo too much flex to eventually crack. I am wondering if anyone has ever attempted to used epoxy resin over bondo.

The stuff I currently have is not like fiberglass, it is able to hold nicely, but it also gives some slight, very small flex. I used a test foam piece before and coated it in wall putty, which cracks easily. I covered it in resin and even though it is cracked under it, the top is still nice and smooth.

So, any thoughts on this move? Don't want to destroy my helmet.

Here is a test piece with the easily "crackable" putty... This is one coat that is dried. This was after flexing the piece and it still holding its top without cracks.

I just need to know if this still will work on Bondo. I might even test another piece when I get home, with bondo on it.

http://www.therpf.com/attachments/f24/tron-rinzler-costume-wip-imag0362.jpg-235149d1379952314

 

[Onephattsi2]

If the helmet is simply foam, with plain resin, meaning no mat or cloth, and body filler, I would say the chances of it cracking are very high..... Resin alone isn't inherently strong. The mat or cloth is where you get your strength. So plain resin will flex pretty bad, and if the filler has any thickness to it at all, it becomes brittle... And will break and peel easily if flexed...

 

[Pyrotechx]

If the helmet is simply foam, with plain resin, meaning no mat or cloth, and body filler, I would say the chances of it cracking are very high..... Resin alone isn't inherently strong. The mat or cloth is where you get your strength. So plain resin will flex pretty bad, and if the filler has any thickness to it at all, it becomes brittle... And will break and peel easily if flexed...

So, maybe a good plan after I cut the visor out, will be to resin the inside of the helmet with epoxy resin, use matting on the inside, and then resin over the bondo on the outside with no matting?

 

[Onephattsi2]

Even with resin over bondo over resin on the exterior. I'm afraid you may be able to crack it if you handle it too much... You may test it on another piece of foam before you get too far into it.......

 

[Pyrotechx]

Even with resin over bondo over resin on the exterior. I'm afraid you may be able to crack it if you handle it too much... You may test it on another piece of foam before you get too far into it.......

I might do that, because I have probably 20+ hours and about $40 worth of resin, bondo, and foam into this helmet. I need to make sure it does not get destroyed or cracked. I thought about vacuum forming the entire thing, but if I did that, I would have to get it 100% perfect the first time since the main form would be destroyed trying to get the helmet out.

I might just try to cover it all in epoxy resin and hope for the best, after I cut out the visor for vacuum forming.