Minor Body Repair Question - Fiberglass on metal?

[SVTY SVN]

Gurus,

New EB owner here. Couldn’t find this topic already addressed. After the lift, and the cooling issue, oh and dash, and, and…

After all THAT, need a way forward w small rust through areas behind each wheel well and rocker. Local, reputable restoration shop recommended grinding/neutralizing area then applying black tinted fiberglass over it for seamlessness. Seems plausible but I’ve never heard of mixing metal and fb.

Your thoughts?

 

[DirtDonk]

It’s generally considered the incorrect way to do it. Even though it’s viable, and has been utilized for as long as people have known how to work fiberglass, it’s still considered second fiddle to patching steel with steel.
And with the availability of pre-stamped panels, as well as the sheer number of people that know how to cut a piece of sheet metal and weld it in as a patch, it doesn’t make sense to me anymore to use fiberglass.

Over the years on these Internet forums we’ve learned that just a huge number of Broncos have been patched and pieced together this way. Most of them not doing it the way you mentioned though, and neglecting the preparation. Typically they would just lay fiberglass right over the cancerous metal.
Not the best practice, even of a less than best practice

 

[DirtDonk]

Even in my case, before the really modern stamped replacement panels were available, I bought a pair of standard cut and bent metal floor panels from James duff and pop riveted them in place.
I didn’t have welding equipment or even most of the other tools of the trade that I have these days, but I still went to great lengths to cut out the affected metal, prepare the remaining surfaces and used silicone to glue the panels in place and seal out moisture while using the rivets to do the ultimate holding.
That was probably about 35 years ago and they are still drum tight. You can tell they’re not original because there are no strengthening ridges or even a stamped dimple for the body mount. I did that with a ball peen hammer.
Doesn’t look factory, but it looks good enough to make me proud that I did it.

 

[DirtDonk]

Looking at your pictures closer, I guess I can figure why the person would choose fiberglass over metal. They are just flat panels, so metal should be easy to work with. But they’re in a couple of the most awkward spots imaginable! So the ultimate decision on his recommendation probably was based on cost.

 

[SVTY SVN]

Great information as always, Paul. Thank you.

 

[Rustytruck]

it was done alot when factory stopped producing stuff and your local parts yard had no options for you. then the internet came and used and new parts are available. I remember the 10 years you couldn't buy replacement parts. fiberglass over properly prepped steel works fine. where you get iffy is improperly prepped metal. epoxy is better than polyester resin and panels that are left in the sun. the thermal expansion rate of steel and fiberglass laminates are not the same so in parts of the country that get very hot the stuff in the sun stretches and cools enough times the bond breaks and your back to a failed joint rusting again. but far better than nothing or roof shingles laminated with tar of winch I have seen a few times.

 

[SVTY SVN]

Rustytruck,

Thanks for that. Shingles and tar? That’s crazy, but I believe it.

The damaged areas are so small and awkward I lean toward fiberglass. So if I’m hearing you right, you’d recommend fiberglass mesh (not cloth) but sealed with epoxy instead of traditional fiberglass resin. Should I do the step three, black POR15 rust preventative coating before or after the epoxy?

Cheers!

 

[bronkenn]

Rustytruck,

Thanks for that. Shingles and tar? That’s crazy, but I believe it.

The damaged areas are so small and awkward I lean toward fiberglass. So if I’m hearing you right, you’d recommend fiberglass mesh (not cloth) but sealed with epoxy instead of traditional fiberglass resin. Should I do the step three, black POR15 rust preventative coating before or after the epoxy?

Cheers!

I have used the POR with a fiber mesh they sold. Just put a coat of POR than apply the mesh while wet and put on another coat over it. Worked really well. PRO TIP: Use gloves!

 

[SVTY SVN]

I have used the POR with a fiber mesh they sold. Just put a coat of POR than apply the mesh while wet and put on another coat over it. Worked really well. PRO TIP: Use gloves!

You read my mind! Was pondering this possibility after posting last night. Thank you very much; I will order mesh now.

 

[73azbronco]

Use POR and mesh. Fiberglass to me would invite trapping water and making the hole bigger. POR would kill the rust in place. Your body shop should know about them.