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Fiberglass, resin and bondo

Posted: Tue Oct 24, 2017 7:07 pm
by Eric3501
I am a bit new to body work, and am in the middle of undoing some work someone else did...I purchased a 7 pierce Baja body kit and removing some molded in tail lights that the individual did a number on. Anyway my question is on a gel coated panel of fiberglass is it normal to not scuff the gel coat and paint resin on then add the Bondi over the resin?

Re: Fiberglass, resin and bondo

Posted: Wed Oct 25, 2017 10:42 am
by risk
what are you trying to fill with the bondo? You might be better off with a more flexible filler. Bondo on some thin fiberglass fenders is asking for cracks.

Re: Fiberglass, resin and bondo

Posted: Sun Nov 05, 2017 2:10 am
by Eric3501
I am not try to Bondi anything as I am more removing a mess someone else made. In the process of removing this mess I encountered a lot I had never seen and was asking more if it was common practice or more he really was clueless as I suspect. There were no detectable sand or scuff marks on the fiberglass gel coat, then they applied resin to it then some Bondi over kind of glass cloth at that point at all, just the body filler...after about 1/2 an inch they decided to start with the resin and glass, then top it off with more body filler...took me 2 weeks to get that mess off. The body filler on the resin was like sanding through cement...I have read a couple body working books and quite a few YouTube videos but never heard or seen of this practice...did I miss something along the way? Thanks for the reply...

Re: Fiberglass, resin and bondo

Posted: Sun Nov 05, 2017 8:40 am
by Ol'fogasaurus
There are some new bonding materials (and I am not talking about basic FG resins here) that are far stronger than even a long line of fasteners used for joining parts together. It is extremely possible that one of those little jewels could have been used and it wouldn't surprise me at all. I would scuff up the bare FG before using a Bondo (a brand name but used as a general term for other brands of fillers []) product and I don't think I would use even a FG repair style of Bondo over gelcoat as the gelcoat is stiff and can come loose/the bond fail from the FG itself. Layering, like you say you have, is done but it isn't a good idea.

If I remember correctly, the gelcoat is first sprayed into the mold then the FG and resin is then added and built up.

If it is as hard as you say you might be stuck using power sanders to break the layers of "stuff" up.

Re: Fiberglass, resin and bondo

Posted: Sun Nov 05, 2017 9:44 am
Sounds like someone used JB weld to fill and build with... either way, it is Common for people (who have no clue what they're doing) to improvise using products and materials that are not truly suitable for the job.

Anyone who knows what they're doing would not have applied the fillers that were used on that, I don't think. Fiberglass is a pretty amazing product to begin with, and todays fiberglass resins are very good at making pretty nearly any shape you want... if you know what you're doing.