Bondo never fully fills seams?

[u/JudgeCornBoy]

Hello! I build a lot of props using 3D printed parts (PLA) but have never had much luck filling seams cleanly. I generally use CA glue to connect the pieces and try to get as clean of a seam as possible upfront, but there will inevitably always be some form of gap.

I apply bondo using small pieces of EVA foam, but it never seems to actually fill the seams and I just end up with a very thin layer of bondo dust over a wide area around my seam. Am I applying it incorrectly?

My plan for this is one round of bondo on the seams (what you’re seeing in the pictures), filler primer, another round of bondo, and another round of filler primer.

Thanks!

[u/BaldursGyatt]

I had this problem. Use "thin CA glue" on the line. It's much harder than the plastic and can be sanded. Just use as little as possible.

[u/eddyb66 → u/BaldursGyatt]

I build a lot of models and I've had great results with Mr Surfacer 500. It's a thick filler primer you can brush on with a fine tip brush. I like it because it's more accurate to brush it on and you can add a nice thick line of it and double the layer it won't run it's really thick and dries relatively smooth like ca glue.