Project HY OFCR: SMC/fiberglass repair 101

So, I am posting this up as a bit of an 'aside' to the rectification of my '88 Corvette coupe. The art of fiberglass repair spooks many folks and SMC (Sheet Molded Compound) repairs require some specific materials and processes.

Long story short SMC is a plastic/fiberglass compound. SMC-based resins and fillers can be used on fiberglass repairs but fiberglass resins/fillers cannot be used on SMC. If you do this the repaired area will 'pucker' under heat/direct sunlight. Here is a good overview of the 'vette and the materials used to build them over the years:

http://www.superchevy.com/how-to/vemp-1108-corvette-body-materials/viewall.html

I had removed the interior from my '88 as it soiled/smelled of mouse pee. In doing this I found a few areas that needed repair. With this being the case I went ahead and addressed two immediate exterior repairs as well. Follow along and see what gets done! I am not expert at all here. But I have worked with fiberglass/SMC over the years for repairs on boats and cars. For these repairs make sure to use fiberglass mat and not fiberglass cloth.

First up, here is what I used:



Here are the fiberglass mat pieces I used along with a console panel that I chose to repair a few cracks on:



Make sure you use a clean cloth to wipe down fiberglass dust after you vacuum. Do not use any kind of solvent, water or paint prep to wipe the areas down. Clean cloth on the left is good...cloth on the right is NOT a good choice:



More to come...

Later,

Lee

Moving on, here are the areas to be repaired. All of this damage was done by the prior owner(s).

This is the drivers side floorboard where they tried to jack the car up and instead punched a hole thru the floor. The underside will need to be repaired as well but I can do this come springtime:



The passenger side floorboard was given the same 'treatment' except it's actually even worse. They buckled the seam and this will require extensive work underneath to get fixed properly. I'll address that in the spring.



They had mounted what appeared to be a cellphone mount on the passenger side of the tranny tunnel. Apparently they had to drill, drill and drill even more until they were 100% satisfied it was going nowhere:



More to come...

Here we have the drivers side sanded down and the SMC resin applied. Make sure that you sand thru the paint and primer so that you have an excellent mating surface for proper adhesion. Also, add more mat than is required for additional strength.



Fiberglass mat is laid down. Make sure to have enough resin to completely soak the entire mat:



On the underside I added what I have always called a 'friendship patch'. This adds extra strength to a hole repair and helps to create a stronger repair. Also, this area will receive a larger repair patch that cover the 'friendship patch' come springtime:



Passenger side floorboard sanded down. This is a tougher repair due to the buckling of the seams. This patch will seal the inside but the stronger repair will be done on the underside:



SMC resin and fiberglass mat added to area:



Transmission tunnel area sanded down. This repair consisted of me filling the holes with SMC resin and then applying the fiberglass mat:





Here is a shot of the drivers side repair with a drop light underneath to show the extent of the repair. The hole was the size of a child's fist:



More to come...

Here are the exterior repairs done to the Corvette.

The hood has a true chip that went all of the way down into the gelcoat. It's about the length of 2/3rds of my pointer finger:



I used three pieces of fiberglass mat cut to size to created a layered repair. I did not need to prep the painted areas around the chip as this repair was to simply build up and be able to blend in the chip to the level of the factory finish.

1st piece:



After all three mat pieces added:



This major crack is right at the drivers side door on the quarter panel. This has been busted for some time now as the edges are buffed down a bit:



The area was sanded down a bit to help adhesion for the resin and mat in the crack. But in the future this entire quarter panel must be stripped and repaired in its entirety.



As you can see here I sandwiched the SMC resin and fiberglass mat between the crack of the panel. This will add extra strength to the area instead of just using resin and filler only. Some folks would use a combination of chipped mat and resin to fill it. But in this instance I preferred to have a solid piece of cloth in place:



One trick you always want to use when you repair cracks is to drill out the end(s) of each crack. That way the crack cannot migrate months and even years after the repair:



This basically wraps up what I am doing now on the structural repairs of my Corvette. I am no expert but if you have any questions I'd be happy to answer them the best I know how.

Later,

Lee

Oh yeah, here is my rigged up method to having the split panel stay in place while the repair set up.

Later,

Lee

Nice thorough explanation Lee. I know that working with fiberglass, it's a lot more work than working with steel.

SMOKNZ wrote:Nice thorough explanation Lee. I know that working with fiberglass, it's a lot more work than working with steel.

Looks good Lee.

SMOKNZ wrote:Nice thorough explanation Lee. I know that working with fiberglass, it's a lot more work than working with steel.

Thanks for the compliment! It's intimidating for sure but I'll be honest I don't know that it's necessarily more work than welding. Both types of repairs have their own specific do's and don'ts. If anything I think that welding takes a bit more skill and a deft touch. For some reason though 'glass work does seem to spook folks more so than metal work.

Later,

Lee

Reb Stew wrote:Looks good Lee.

Thanks a bunch! That means a good deal coming from you, Reb. You've done far more bodywork than I have.

Thanks,

Lee

Thanks for sharing