Iron man helmet build in need of advice using plaster and/or bondo

[CharlesK]

Hi, this is my first post on the forum . i started on an iron man pep build a couple of weeks ago and i was pleased with the result so decided to fiberglass it. i removed the faceplate for better access for fiber glassing. once done i noticed the faceplate didn't fit on the helmet properly anymore. it had been slightly flattened because the weight of the resin flattened the face a bit (face down while fiber glassing). i was not very happy about the rigidness of the helmet so i put a big layer of plaster on the inside which worked like a charm.

so, i decided to use plaster on the outside instead on bondo, i used a car body repair filler on my bike once and it took ages to sand down. now that I've used plaster I've noticed it's very brittle. what should i do from here?

here you can see the gap between the faceplate and the helmet.
View attachment 104195

the gap filled up nicely with plaster but I'm scared it will brake and it's hard to get clean edges without chips.
View attachment 104196

also, the eyes were a nightmare. ignore them :confused

 

[Helagak]

That's a nice shape. Good pep work. You should have left the face on when you fiberglassed to hold the shape.
All your fears about chipping and cracking are the reason people don't use plaster. Bondo has much more flex than plaster does. And cuts better too. I'm not sure what you can do to fix this. Maybe a couple light coats of bondo will help. But honestly, I am no pep/glass/bondo expert. Maybe someone with more experience can chime in.
Good luck!

 

[CharlesK]

That's a nice shape. Good pep work. You should have left the face on when you fiberglassed to hold the shape.
All your fears about chipping and cracking are the reason people don't use plaster. Bondo has much more flex than plaster does. And cuts better too. I'm not sure what you can do to fix this. Maybe a couple light coats of bondo will help. But honestly, I am no pep/glass/bondo expert. Maybe someone with more experience can chime in.
Good luck!

thanks, i could try and break/sand most of the plaster off and start over with bondo. how easily does bondo sand compared to plaster? i had one experience with some a couple years ago and it was a nightmare. maybe i got the wrong stuff back then. it was rock hard plastic.

 

[CharlesK]

oh man, I'm really stuck. i don't know if i should continue or what. would it be possible to apply a thin layer of fiberglass resin on the plaster to stop it from cracking? then continue with bondo?

 

[Powerhouse70]

TBH I wouldnt chance it, even with the layer of resin on top, plaster is a very soft material...it might not crack .....just deform under the resin and it would be almost as bad.

Youre not that far along at this point that you cant start over and maybe fix the eyes while youre at it.

Only other advice that i can give you is that make sure you put the bondo on thinner than you did the plaster (try using an old credit card and wipe it on in small strokes) or its going to be hell to sand.

 

[Helagak]

Also, a power sander is your friend. I would try to take most of the plaster off and do bondo. Yes, bondo is a pain to sand. But if you use a power sander for the main work and hand sand the fine details, it's doable. An multiple thin coats are much better than one thick coat.

 

[CharlesK]

Ok, thanks guys. I'm going to give it a go tomorrow. I'll update after I've made some progress.

and by the way, I'm assuming you mean one of those triangle mouse sanders. and what would you recommend i do to the eyes?

 

[Darran Murray]

I know it's an old post put it might help some one else with the same issues --->>>Sand off the plaster an get easy sand car filler. Use a stanly knife to shape "carve" the bondo when it's semi dry kinda like a putty it will take a lot of work out of sanding a chicle and rasp set will help a lot.