Gap filling super glue?

[juntari]

Hi, I have a large seam that I need to glue together on a helmet that also needs large gaps filled. Can someone suggest the best method to guide me in the right direction? The seam goes all around the helmet and the two pieces only make contact at a few places. The rest of the seam has gaps ranging from paper thin to as much as 3mm (1/8th). I was thinking I could glue the contact areas with super glue to hold it in place, then fill the gaps with some rigid material. I want to avoid hot glue or epoxy glue because I find that it has a bit of a soft feel to it when dry and I'm worried that the slight amount of flex would crack the bondo that i plan to lay over it. I was also considering pouring smooth cast into the cracks but I can't figure out how to have it pour evenly into a curve without leveling off when drying.
Here is an image of the seam at one of the bigger gaps:

I'm open to new materials and techniques, as long as it makes a rock hard super bond like if the two halves were always meant to be together.

 

[Ozymandius]

The best thing to do is to fix the seam so that it seals properly with a tight fit.

Spread petroleum jelly on one half of the helmet where it contacts (ie: top half) with a good 1 to 2 inch flange for spillage. Then spread a thin bead of bondo on the seam for the bottom half. Press together and let sit until the bondo has set. The petroleum jelly will allow you to seperate the two halves and then you will have a nice tight seam that fits perfectly.

You may need to repeat this a few times to fill in all the gaps. If you do, make sure you clean the bottom part well to remove any residual jelly, else the new bondo won't stick.

Once you've got your seam cleaned up and tight, you can glue together with epoxy.

Oz

 

[blue2k]

Epoxy putty, or Car body filler. May require some sanding to retain the smooth look.

 

[robn1]

I'd just use epoxy gel, it's thick like Vaseline so it won't run. Then smooth the seem with Bondo.

 

[juntari]

Ozymandius: thats a clever idea, do you think the bondo would be strong enough though and not eventually crack? What type of bondo are you talking about, the 2-part automotive filler or the spot putty that comes in a tube?

 

[Ozymandius]

Depends on the usage. For regular dispaly purposes, no problem. If however this is a costume piece, then I'd reinforce the seam on the inside with a strip of fiberglass (assuming the helmet is fiberglass). If the helmet is plastic, then you can do the same reinforcemnt with some Shell-Shock or plastipaste.

From what I can see of the visor area the helmet looks pretty rigid, so I assumed fiberglass. Is any part of it flexible at all?

Oz

 

[hansicle]

How about some 2 part epoxy. You can get it in different set times, the stuff tends to be on the thick side, and in 5-10 min, you could probably get the gap filled and bonded. The other trick, use super glue with baking soda....you put on a little glue, sprinkle on some baking soda, and it will harden up pretty good, but it can get brittle.

 

[Ozymandius]

Ozymandius: thats a clever idea, do you think the bondo would be strong enough though and not eventually crack? What type of bondo are you talking about, the 2-part automotive filler or the spot putty that comes in a tube?

Oops, forgot to reply that I was talking about the two-part body filler. Spot filler in the tube is only good for small pinholes.