Rust repair with fiberglass?

[Fletcher]

I just watched a YouTube vid of a guy doing rust repair to fenders with fiberglass (below)

 

So..  is this a legit budget repair/restoration method or so absolutely verboten that I should go flog myself with a tire iron for even having asked?

 

 

[esty]

i have some fiberglass repair on a 20+ year old Honda CRX that have held up through thick and thin...if i had a small rust repair on an o2, this is the method i's use because it's cheap and easy for us non-welders

 

that said, you'll get a load of crap, from the majority, for even asking....but what i always say is "YO, it's my car, my money"

 

[tzei]

You'll just "buy" yourself a little more time until you have to address that issue and by that time it'll be bigger and more expensive.

 

i'd say no but i have a welding machine

[theNomad]

If it's absolute swiss cheese returning to the earth i'd say do fiberglass so you don't flintstone it.

If you have a welder or know someone with one, a few sheets of metal from an old filing cabinet or licence plate is probably better if not only a tiny bit more work. If no tools and its a basketcase, slather away. 

If it's just a few spots on something with potential, paint it with POR-15 until you're ready to do it right.

 

[MitchaPaLoOza88]

First hand experience... The previous owner used fiberglass for repairs and it was an a nightmare. Basically all the metal where the fiberglass was rusted away and the fiberglass was all that was left. And when you decide to do it right with metal, it absolutely covers everything in fine white dust cutting it out.

 

If you are in it for the long haul and doing rust repair:

Highly recommend a Hobart Handler 140 MIG for a first timer. $450 Tractor Supply Co and if you find it cheaper they price match. I made the mistake of buying a cheapo welder to start and ate up hours of my time and left me frustrated. This tool will last a lifetime.

Edited July 6, 2020 by MitchaPaLoOza88

[TobyB]

Fiberglass has its place-

 

but putting it over rust is, as everyone notes above,

not such a hot idea.  Especially on a unibody car,

where most panels have a structural function.

 

That said, if you wanted to play with it on the front fenders, hood or trunk

while you keep an eye out for some good used ones, why not?

It's cheap!

It's also REALLY hard to get it to look good- honestly, the time 

spent doing it in metal's not much worse, and then you're done.

 

t

 

[AustrianVespaGuy]

So fiberglass can work well for repairing small rust spots AS LONG AS YOU CLEAN OUT ALL THE RUST FIRST!!! You need to really get in there and cut/sand/strip things to get rid of ALL the rust to the point that you ONLY have good clean metal left around your hole.  Then you can use POR15 to protect the metal and fiberglass to patch the hole.  But if you just slap some fiberglass over the top of rusty metal, then yeah you're in for a much worse time on down the road. . .

[Fletcher]

3 hours ago, MitchaPaLoOza88 said:

First hand experience... The previous owner used fiberglass for repairs and it was an a nightmare. Basically all the metal where the fiberglass was rusted away and the fiberglass was all that was left. And when you decide to do it right with metal, it absolutely covers everything in fine white dust cutting it out.

 

If you are in it for the long haul and doing rust repair:

Highly recommend a Hobart Handler 140 MIG for a first timer. $450 Tractor Supply Co and if you find it cheaper they price match. I made the mistake of buying a cheapo welder to start and ate up hours of my time and left me frustrated. This tool will last a lifetime.

i likewise have a knock-off (flux) welder And wish I’d bought the Hobart instead.  ?

[Vicleonardo1]

POR 15 makes patch kits. Ideal for floor pans and trunk. It will stop the rust and serves as a good patch. 

It just doesn't do well in any spots that have sun (UV) exposure and it aint easy to paint over... 

 

 

[SydneyTii]

I’ve done it on areas where there is no requirement for strength, I had a hole about the 1.5cm diameter behind the sound deadener in the heater plenum area, the rest was mint, the work required to weld this in a car not stripped out was not practical, so I sanded back to bare steel, rust treated, fibre glassed it, primed and painted.

on the back of the panel I did the same as best I could, I then sprayed with clear Bilt Hamber rust preventing wax both sides, no air will get through that! And you’d never know there was a repair.

i don’t expect an issue.

As Toby says it has its place.

so just don’t bodge it ?

 

Edited July 7, 2020 by SydneyTii

[SydneyTii]

1 hour ago, SydneyTii said:

Double post

Edited July 7, 2020 by SydneyTii

[Fletcher]

Tops and bottoms of fenders seem to be my problem areas like below.  Welding holes seems relatively easy, but I'm not sure what to do along edges like this(?)

 

 

 

[Mike Self]

+1 on using POR 15 paste on spots like you picture, Fletcher.  The paste by itself will bridge a hole up to about 6mm (1/4") in diameter; any larger, ding the edges down (after working your way back to sound metal--rust is OK, but no Swiss cheese or paper thin metal), cut a piece of fiberglass window screen to fit the hole, then butter the hole's edges with POR 15 (wear gloves, it'll stain your fingers for weeks) and press the window screen into the paste around the edges.  Let that dry, and then fill in the center of the screen with more paste.  Keep the whole patch below the level of the metal so you'll be able to put a filler skim coat over the POR 15.  But before doing that, make sure you didn't leave any holes in the patch--shine a light through the patch if you can to catch pinholes.  

 

I've used this repair on a perforated E30 rear wheel opening lip (like an '02's); exposed to Ohio salted roads and never completely finished (only primered and sealed) it showed no signs of rust after two years.  

 

On the other hand...I had a '72 Datsun pickup truck whose rocker panels were hardware cloth with Bondo spread over it.  Never rusted or fell out in my 6 years of ownership.  I was amazed...

 

mike

[Fletcher]

7 hours ago, mike said:

+1 on using POR 15 paste on spots like you picture, Fletcher.  The paste by itself will bridge a hole up to about 6mm (1/4") in diameter; any larger, ding the edges down (after working your way back to sound metal--rust is OK, but no Swiss cheese or paper thin metal), cut a piece of fiberglass window screen to fit the hole, then butter the hole's edges with POR 15 (wear gloves, it'll stain your fingers for weeks) and press the window screen into the paste around the edges.  Let that dry, and then fill in the center of the screen with more paste.  Keep the whole patch below the level of the metal so you'll be able to put a filler skim coat over the POR 15.  But before doing that, make sure you didn't leave any holes in the patch--shine a light through the patch if you can to catch pinholes.  

 

I've used this repair on a perforated E30 rear wheel opening lip (like an '02's); exposed to Ohio salted roads and never completely finished (only primered and sealed) it showed no signs of rust after two years.  

 

On the other hand...I had a '72 Datsun pickup truck whose rocker panels were hardware cloth with Bondo spread over it.  Never rusted or fell out in my 6 years of ownership.  I was amazed...

 

mike

Thanks, Mike!  
 

What do I use for “filler skim coat”?

[MitchaPaLoOza88]

It's probably going to be a little rustier than it looks under those trim pieces. That's just the way it goes.

But..

If you completely clean out all the rust in that section and its just a bunch of pin holes (no bigger than a pin head). I mean super clean metal. Blowtorch, lead, flux and a ton of patience and you can fill the holes up. Then sand and treat it with some rust inhibitor primers or something.

 

General Disclaimer

If you are going full resto. I would kinda make the decision to either drive it like it is for awhile and enjoy (do some mechanical things) or just go all in on body work. It sounds stupid but once you start pulling trim and stuff its just gonna make more sense to just do the whole body at some point. It becomes, "if I wanna paint the car right, then I should pull the windshields out, but don't want to do that a bunch of times so might as well do all the body work as well"