Instructables

How strong is bondo body filler?

How strong is the bondo body filler? Im looking into making custom molded handles with a castable plastic or rubber and was looking at bondo. Would it suffice for making a light handle? Whats it like when its dry in terms of wear and tear,texture.care,and strenght?

Burf4 years ago
Bondo has has decent compressive strength, but it has poor tensile strength.
You can use it to support a load under compression with reasonable results but unreinforced, subjecting it any bending forces will break it down quite easily.
NachoMahma Burf4 years ago
.  In English, it's too brittle to take much stress.
.  And, when applied in thick layers, it tends to crack as it dries.
jvincent62 years ago
Bondo is tough stuff, but if you're worried about strength, consider using one of the reinforced versions like Bondo Hair or Bondo Glass -- they have small strands of fiberglass that add to the strength. Burf is sort-of right, twisting forces might result in a short life.

As for cracking. I don't know. Plenty of people use it as a molding and modeling medium -- even sculpting. Scan the web and you'll find some schools use it in art classes. The most common source of problems is people adding too much hardener, it speeds things up but can cause errors.

As for wear and tear, Bondo is water resistant, but not waterproof unless you paint it. Consider that cars go decades with painted Bondo parts. Think abut all the expansion and contraction a car goes through over a lifetime.

Sanding: You can begin to sand and shape Bondo after about 15 minutes, while it is still somewhat sift.