Dealing with tank corner dents?

[Lucien Harpress]

Interesting story. I was cleaning up a "new" (to me) tank that Mr. DriverRay so graciously sent to me (thanks again!), and discovered something rather interesting about it. Apart from having about 50 layers of paint on it, it seems both rear corners were dented in quite far, and consisted about 90% of what I'm pretty sure is Bondo. Because I'd already removed most of the material, and figured that any future puttying should go on as much bare metal as possible, I got rid of as much of it as I felt safe doing.

Of course, this means that I'm going to have to eventually build these corners back up and sand them back to shape. Problem is, I've never worked with Bondo, or any other filler putty for that matter, so I'm not sure how easily you can "build" shapes with it. My question is, what would be the best way to build these corners back up?

(Pulling them back out is definitely out of the question. They aren't shallow. In fact, the corners are pretty much inverted. They could be popped back out, but it would be FAR more trouble than it's worth.)

[Silent]

If you're going to fill them without pulling them, use thin layers and allow them to cure completly between layers. If you just spoon it on thick it won't cure properly. Past that it's just filing and sanding to get the shape you want.

[fredintoon]

3 different layers of pudding mix

If you're going to fill them without pulling them, use thin layers and allow them to cure completely between layers. If you just spoon it on thick it won't cure properly. Past that it's just filing and sanding to get the shape you want.

Hi Ray,
It's only the one part body filler that will not dry if it's daubed on too thick.
The two-part filler sets up regardless; it's problem with deep dents is that it ain't very strong.
I would use the two-part filler that has glass fiber strands in it to give it strength.
Leave it under-full and when it's set finish off with two-part lightweight filler.
Sand that to the proper contour and spread air-drying spot putty over it.
Wet-sand the spot putty smooth before spraying with primer.

[Larrym]

Skippy or Jif?

I agree with Fred about the two part filler. It doesn't need air to "dry" but instead uses a catalyst to "cure". (Totally different process) The key is to spend the time/effort to mix the two parts thoroughly.

About the building process...with no pictures I have to just imagine a large inverted dent. I'd say to first make sure that the metal surface is sanded well with a coarse 80 grit carbide paper. (The aluminum coated stuff works ok on wood but we're talking about metal prep here.)

After dusting it off and wiping it down with acetone you're ready to apply the two part bondo with the "kitty hair" in it. The key thing here is to have and use one of those plastic bendable spreaders. Use it flat to push/spread the bondo into the depression and then bend the spreader into an arc to make the bondo curve into the right "roundness" of the tank. Key here is to not fuss with it too much to try and get it into the right shape while it's still pliable. Just take a stab at it and what you get is what you get.

Then wait the required time for it to get partially hard. Chances are it will be warm or even hot depending on how much filler material you have used. At this stage you can use a sharp knife or even a "grater" to remove anything which is obviously out of shape. It's a lot easier to do the removal at this stage rather than waiting for a full cure where you'd have to file or sand a lot of material off.

Then depending on how much a perfectionist you are, you can apply more material which will not require the filler to be sanded beforehand as the next layer will interact with the previous layer and chemically bond. (Way stronger than the mechanical bonding one get's by waiting for the material to cure completely and then sanding it again...)

In the end after the bondo has completely hardened/cured you'll prob'ly have to use a "finishing" putty to make it smooth enough for painting. This stuff usually comes in a tube like toothpaste and does require air to dry. Same rules apply about just putting it on and not trying to fuss with it while it's "wet."

The first time through the gate using this stuff is not that tough and you'll end up with something you can live with.

Practice spreading peanut butter beforehand and you'll have a good idea of what to expect....

[Larrym]

Batch Size!!

Don't mix up a huge pile of the two part stuff and expect to put it in all in at once. The technical term for the way this stuff works is "Exothermic": it puts out heat as it cures. A big wad of this goo can get really hot really fast.

Make small amounts of the stuff and apply it. Wait for it to "kick"/get sorta hard and begin to cool down before you make up some more. Then add more of the filler.

Fill....wait....shape...fill....wait...shape. This save a lot of elbow grease/sanding and the overall strength is much better.

Lots more fun than Playdoh but not as edible.....

[xs11bobber]

I just tackled this for the first time myself about 3 months ago. It took me almost 2 weeks to get the shape. I had 2 huge right top side dents, 1-3 inch dent on the right front and a dent on the left front almost looking like scaled down eyeglasses. They all filed pretty easily, but the eyeglass shaped one took me the most time. You can't always tell it looks like azz until you prime it either. Needless to say it's a lot of waiting. Have a power sander ready. I sanded by hand the first 3 days until I said F THAT. I used high-build automotive rattle can primer too just because I could get it at walmart.

If I had it to do over... I'd throw some dollars at it and let someone else do it. Not a pleasant experience for me, lol.