What should i use to fix this dent* before painting?

[JJ08]

Don't ask me how it happened. It makes me sound stupid, but i did what i needed to in the end.

It's on the edge of the control cavity. I'm gonna be painting the body black, so it doesn't need to be a perfect repair (besides, everything else on the bass is super ugly so it would fit in nicely).

I'm currently thinking either wood filler or a mix of glue and sawdust, but I'm not entirely sure if it would resist cracking and flaking, which would mess with the paint job.

 

[jdjk7]

Funny Bocchi profile picture.

Also, the issue I've heard of when trying to fix dents like this, is that the filler material as to have enough thickness to be structurally sound, or else it'll do as you describe-- break, flake, etc. Now, if the dent is not particularly deep, what you could try is to carve it slightly to make it deeper. This would give you more volume for the filler. You would then need to sand the filling flat. I've had a bass with a small dent that I was already thinking of refinishing, and this is what I was going to try. I'm certain that one of the actual luthier types around here has a more informed opinion than me though.

 

[Matt Liebenau]

You could try steaming the dent out first, it looks like the wood might be mostly there. Use the highest setting your soldering iron has, place a wet cloth or paper towel over the dent, touch the soldering iron to the cloth for a few seconds until you hear the water start to steam, remove and check. It can take 2 or 3 treatments but that can work wonders.

If the wood is missing or for anything steaming doesn’t remove the best method is to use a good marine epoxy like West Systems or Total Boat. That will also work as grain filler for the rest of the body. Having said that, I have used Timber Mate filler, and Bondo glazing and spot putty like you’d use on a car. I also just tried JB Weld Kwikwood on the body I’m currently painting so no long term results with it but it seemed to work well enough. Not significantly better than West Systems but it worked.

 

[jTrolt]

Hit your local hardware store for some epoxy putty, if you don't already have some on the shelf. I use a fast set from Mohawk, but there's a JB Weld version in almost every hardware store, but may need the better part of an hour to completely solidify.
When applying, leave it proud on both the edge of the cavity and on the surface of the slab body. Give it the prescribed time to harden completely. Wrap some sandpaper on a flat block and level it out. Grind it true on the inside of the cavity if needed. Finish as you would normally from there.
Hands down, the fastest, easiest to sand, and lasts forever, like a freakin' rock.

 

[Dirk Diggler]

+1 on trying to steam it out with a cloth and soldering iron.
If all that fails then consider filling with a slurry of glue and sanding dust.

 

[KidAmnesia]

I dropped one of my first guitar builds while finishing it and got a dent a bit bigger than yours on the edge of the body.

I scrapped the lacquer and steamed it out with a damp cloth and a clothes iron (better heat distribution than a soldering iron). It's faster and has better results than filling it with something.