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Repairing a damaged 1963 to 1967 C2 Corvette Fiberglass Fender

How to fix damaged fiberglass and save yourself a bunch of money

Jim Smart Jun 10, 2019
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Southern California living has its benefits. Perfect weather. The beaches and the mountains coupled with skiing, surfing and throw in Hollywood. Plenty of surviving classic cars, too.

Southern California also has its hazards. Because this place has its share of reckless abandon going on, especially on the freeways, you never know when your vintage Corvette is going to suffer abuse, even on a good day. McJack's Corvettes in the heart of Orange County gets its share of hard luck stories from customers who've experienced the misfortune of crunched fiberglass.

Before you is a really nice 1964 Corvette convertible daily driver subjected to all of the hazards of pavement duty in Los Angeles. The owner encountered a large chunk of freeway debris that flew up and smashed the left front fender. It is now McJack's responsibility to make the damage disappear.

Fiberglass is nothing new. The concept of glass fibers dates back a couple of centuries to an inventor named Hermann Hannesfahr, who was awarded a patent for his efforts in 1880. Decades later in the 1930s, Owens Corning figured out how to mass produce glass fibers. It was there a researcher by the name of Games Slayter directed compressed air at a stream of molten orange hot glass and produced fibers in the airstream. So much was discovered via this approach to glass because due to the very nature of glass strands there was an insulating quality there, too. Ultimately, fiberglass has found its way to a multitude of products ranging from insulation to boats and Corvettes.

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Although accident and vandalism damage is emotionally devastating, McJack's tells us repairing the damage isn't as bad as it may seem. What makes it tricky is the C2 and C3 Corvette's unit body construction, but not in the usual way we think of unit bodies. Corvette is a unit body on frame, not like a steel body/platform like we normally see in automobile manufacturing. Because Corvette is a fiberglass unit body you can't just replace a damaged fender or fascia. The darned thing is one huge chunk of molded fiberglass and you need to be something of an artist or sculptor to repair accident damage right the first time. Jack Grubisich of McJack's Corvettes has been massaging wounded Vettes for decades. Jack surveyed the fender damage and concluded he needed to carefully piece the damage back together to maintain the fender's proper composition and integrity, then, lay down resin and fiberglass. This has never been easy for even the savviest body professional.

Once Jack was able to hold the shattered pieces together, he went to work soaking fiberglass in resin and laying it down across the damage. Though this may seem rather crude, this is how it's done. Laying in fiberglass is done in layers. Lay down the first layer, allow it to cure, and cut it down to where you're ready for the next application. Jack cleans up the damage by sanding the broken pieces for good fiberglass adhesion, then, laying in the resin and fiberglass. When the fiberglass is first applied it looks like a relief map of South America. Once the resin cures and becomes hard, Jack works the surfaces with a jitter bug sander and super-course 16-grit sandpaper to cut the fiberglass down to a manageable depth. He then moves on to finer grits to refine the surface. Once the glass is down to a workable demeanor, Jack applies more fiberglass to achieve even greater strength, then cuts the fiberglass down even further, getting it back to the fender's original consistency.

Fiberglass repair is performed in baby steps, layer by layer until you get it where you want it. Because fiberglass and its resin tends to wind up with cavities and glass fibers protruding from the resin, you will ultimately have to apply body filler to bury the cavities and glass fibers. Vette

 

 

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Our C2 front fender has been crunched badly and is in need of repair. No need to replace the fender when you can fix the existing piece. Jack has surveyed the damage and determined this fender can be saved and repaired.

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The damaged fiberglass is first scuffed with a 16-grit disc to give the resin and fiberglass something to stick to.

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There are no unimportant pieces and they must fit together perfectly. You can spread masking tape across the back of these pieces in order to keep them together prior to applying resin and fiberglass.

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Pieces that have broken off have to be carefully sanded where they will dovetail into one another. We don't have a clean break here. The pieces are splintered, which is the way of fiberglass. This means you must carefully sand and fit the pieces together to where they will fit without overlap.

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This looks worse than it actually is. Jack will carefully position all of the broken fiberglass pieces together and secure all of it, then, apply that first Evercoat polyester resin laminating coat with fiberglass to get started. Laminate resin remains sticky for good adhesion during build-up coats.

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With all of the piece positioning established, surfaces are sanded again to ensure good resin penetration. Rough surfaces give resin a place to stick to and cure.

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Do you see how perfectly these pieces fit together? Jack will secure them with masking tape from behind—then—begin laying down the Evercoat laminating resin and fiberglass. When the job is complete the masking tape will be removed.

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A thin first layer of resin is applied to the wound before laying down fiberglass. Jack likes to use Evercoat laminating resin when he's building layers of fiberglass. When he lays down the top fiberglass finish coat he prefers to use Evercoat finishing resin, which will dry to the touch. Evercoat fiberglass polyester resin is a heavy, thixotropic formula that does not run or sag and cures to a non-tacky surface, which is what you want for a top coat.

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Jack suggests supporting the repair from behind with this Quick Grip bar clamp, which is available nearly any home improvement store.

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Jack cautions against laying down sheets of fiberglass. He tears the fiberglass into strands and lays glass fibers into the wet resin and brushes them in.

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Here's a closer look, with resin being brushed into the fibers. Buy a bunch of cheap paint brushes because you will only be able to use them once.

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We have already applied the first coat of resin and fiberglass and followed with aggressive sanding with super coarse 16-grit 3M paper for a first cut. Jack is applying the second coat, beginning with the resin and another layer of fiberglass strands.

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The Evercoat finish resin is allowed time to cure before working these surfaces with 16-grit paper to fine-tune the surface. You may also use 30-grit paper for this phase.

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Inside the wheelwell is as important as what you see outside. Jack pays close attention to the inside to help eliminate any damage. If done properly, no one will ever know the fender was damaged.

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Not all surfaces can be machine-sanded. Areas like this one at the rocker panel have to be hand-sanded, and it can get tedious. Work these surfaces by hand until all imperfections are gone. Body filler will be used to fill pinholes and other small imperfections.

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Wheelwell surfaces continue to be sanded until Jack has eliminated all imperfections.

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The first two layers of resin and fiberglass have been sanded down, leaving plenty of craters. We're going to need one more layer of resin and fiberglass.

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One thing home auto body hobbyists get wrong all too often is the mixing of body filler. This is an easy mistake to make. Follow the instructions on the can to the letter. If you use too much hardener, the filler will cure too quickly and you will have filler crumbs sooner than you ever wanted and have to do it all over again. Too little hardener and you wind up with a sticky, nasty paste that will never cure.

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Jack is using Evercoat Z-Grip filler, which is very forgiving and it holds up very well. When you mix hardener and filler, you want it to look like mint ice cream—like this. Apply it quickly before it has a chance to cure. When it begins to cure, stop applying and wait for it to cure. Then, begin sanding.

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The main thing to remember with body filler is to lay it down like you would butter a slice of bread and get the surface as smooth as possible to minimize sanding time.

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Concave surfaces and edges should be hand-sanded gently with 80-grit paper to prevent removing filler entirely. Filler is applied over fiberglass to fill imperfections in the fiberglass, which means most of the filler should be gone by the time you finish sanding. Ultimately, sandpaper selection will encompass 120-, 220- and 400-grit paper as you get closer to primer and paint.

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A good orbital sander will cut the filler down to a manageable size. Jack is using 80-grit paper for this phase. Jack uses Sherwin-Williams urethane finishes for repairs and complete paint jobs with excellent results. Sherwin-Williams SpectraPrime P27 Premium Undercoat primer sealer is a premium quality 2K-urethane primer-surfacer designed for optimum performance in areas that require low VOC coatings.

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Sherwin-Williams SpectraPrime P27 Premium Undercoat primer sealer is a premium quality 2K-urethane primer-surfacer designed for optimum performance in areas that require low VOC coatings. Sherwin-Williams ATX basecoat is the urethane color coat, topped off with CC200 Dynamic Clearcoat, which Jack says is extremely durable.

Photography by Jim Smart

Sources

McJacks Corvettes
714-775-2799
http://www.mcjackscorvettes.com/

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