3M Bondo/ filler

[FishStretcher]

Originally Posted by FishStretcher

I had a bunch of screw holes to fill in the roof of the cabin of the 25, and I wanted to re-gel coat. So I thought I would try Bondo. Home depot had a 3M filler that sat next to the Bondo. 2nd ingredient was polyester resin (unsaturated, I think). So I gave it a try. Judging by the MSDS, it is different from the Bondo and Dynalite products. They didn't have something I could ID as polyester resin in them. A little digging (ok a lot) shows one has some maleimide chemistry (Bondo), and another has an acrylic in it. From what I can tell- which isn't much. But I did figure I wanted polyester. It looks like the 3M Platinum series automotive filler is the same stuff, so if this isn't a train wreck, it might be good to know. 3M makes a marine vinylester filler, too. But I didn't know that until just now.


It isn't in a structural location, so rather than epoxy then vinylester barrier, then gelcoat, I figured I would just gel coat over this. It sticks pretty well and of course sands great. We will see about gel coat tomorrow.

For the record- This isn't glazing putty. It is two part filler with uncured polyester resin as a listed ingredient.

Gel coat went over it quite nicely. A few drops of brown tint in a quart of Mar-Pro white unwaxed gel coat laid down, with a healthy layer of PVA on top worked quite well. It looks like a good color match. It looked far too dark going on. Weird. That was catalyzed probably at 2.25% as it is still cold up here. The MEKP was a little old, so I am not quite sure what the effective percentage was. I think more than 2%

As for the Duratec Vinylester Primer over the PC-11 "epoxy" putty on the deck- it discolored. I need to look at it after a week of curing. Catalyzed with old catalyst a bit north of 4%, but gel time was still 12-15 minutes. Not sure about the discoloration, but if it holds up fine and covers with gel coat, I don't care. Color match is decent over the white gel coat, but stains brown over the PC-11, but not the JB Weld brand "Water Putty", which is much less runny.