Repairing Rust Damage with Fiberglass

My ride originally comes from Pennsylvania. As a result it has an ATROCIOUS rust problem. Fortunately, it doesn’t look like any of the rust directly impacts the structural integrity of the vehicle. After removing my hood and fenders I was able to see the full extent of the damage. I decided to fix the damage by bonding fiberglass directly to the vehicle unibody.

Tools Used:

  • Hammer
  • Flathead screwdriver
  • Metal Snips
  • Orbital Sander
  • Super cheap paintbrushes (They turn into plastic after you’re done)
  • Latex Gloves
  • Respirator

Materials:

 

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Liberal application of a hammer, flat head screwdriver, metal snips, and my orbital sander gave me a good look at what exactly needed repairing.

The most significant damage was under my driver’s side fender. I had to remove a fair amount of metal in order to eliminate all of the rust spots.

 

 

 

 

 

 

 

 

 

 

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Other damaged areas included the engine compartment frame that my fenders were bolted to and the floor on the drivers side. And yes I could stick my hand right through the bottom of my car and touch the road!

 

 

 

 

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There was also some corrosion damage around the battery compartment that needed patching.

 

 

Patch Management

The first step was to prep the regions. Affixing my handy dandy respirator I mixed fiberglass resin with MKP (catalyst) in order to start the clock. The resin is very sticky, but starts to harden within 3-5 minutes. I coated the problem areas liberally. By the time I’d gotten through coating all of the areas the places I started at had already gotten tacky.

Tacky – Fiberglass resin is said to have gone “tacky” once it is no longer wet and gloppy like an oil-based paint, and is holding its position. At this point the resin is very sticky (like glue). Once it has dried and is no longer sticky, it ceases to be “tacky”.

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Once the resin became tacky I added my first layer of 6oz fiberglass cloth. You can technically add resin to any type of cloth in order to form a solid part. The most common materials are:

Fleece/Cotton/Other Crap – Fleece or cotton are common base materials used in DIY composite construction due to their high availability and low price they lack the strength of more advanced fabrics.

Carbon Fiber – Carbon fiber is super cool, super light, super strong, and super expensive. It is also relatively hard to come by when compared to other fabrics, but it looks sick!

Kevlar – Kevlar is very strong, but it is also extremely heavy when compared to other fabrics.

Fiberglass – Fiberglass comes in two general flavors: fiberglass mat and fiberglass cloth.

Fiberglass Mat vs Cloth – The general difference is price and finish. Mat has a much more course grain and is often used in the construction of temporary parts like molds for future fiberglass work. Cloth is more expensive, but it has a denser weave and can be more easily sanded to a pristine finish. Since fiberglass is not overly expensive I chose to use it as my learning material (as opposed to expensive carbon fiber). I’m using 6oz fabric (fiberglass fabric is differentiated by the weight (oz) of the material).

The next step was to coat the fiberglass with another layer of resin in order to set it appropriately.

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Depending on the location I laid down between 3 and 4 layers of fiberglass.

 

Sanding

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Before applying paint I sanded the patches smooth.

 

 

 

 

Finishing Touches

20141005_164215Finally, I added a layer of paint and let the sucker dry!

 

I’m really happy with how these repairs turned out. The fiberglass is extremely strong (I tested it with my hammer).

 

In making these repairs minimal weight was added to the vehicle. I didn’t have to purchase expensive welding equipment. The project only took a couple days despite my lack of experience with this type of work.

 

 

 

 

 

Let me know what you think or if I left out some obviously crucial detail that you’d like to be regaled with. Yanking the engine out was a load of fun!

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  • Randy

    Thanks for the info I will be doing the same thing