Body Work: Hood Fiberglass Repairs & Primer

In this update the rough body work continues in preparation for sending the car out to have the final body work and paint completed. This time the focus turns to the hood, t-tops and doors where some additional fiberglass repairs are made followed by the application of an epoxy primer intended to seal the fiberglass in preparation for the sanding primer.

Many of these repairs are similar in style and purpose to those outlined in the previous update. The general approach has been to make the necessary fiberglass repairs, apply body filler to even out any rough or uneven surfaces, block sand the entire surface, clean the area, and then apply a coat of epoxy primer.

Prior to my ownership of the car the edges of the hood were damaged in several locations. The edges of the hood were cracked and fractured and the “lips” along the rear edge of the hood were broken off. For a long time I debated just buying a new hood but the thought of spending $700+ wasn’t very appealing. I also wasn’t sure a new hood would fit right in the existing hood opening. So, I made the decision to repair the damaged area. After all, it’s not like I haven’t done fiberglass repair before.

So, to start, repairing the damage required separating the hood skin from the underlying frame. Once again I used a combination of heat, putty knifes, and a hammer to carefully separate the parts.

  

Once the hood frame was separated from the hood skin the damage became even more apparent. In the photo below you can see the damaged corner and, along the edge of the hood, you can see that the lip is gone leaving just the exposed edge of the hood skin. My goal was to reconstruct the corner of the hood and rebuild the lip along the edge of the hood to give the hood skin the strength and rigidity it needs. Little did I know what a colossal pain this would turn out to be…

To repair the hood skin I decided to use the hood frame as a male mold. I taped some cardboard to the corner of the frame and then applied several layers of fiberglass matt and resin to the mold.

After applying the fiberglass matt and resin I placed another layer of cardboard on the top and, as you can see below, weighed the cardboard down with some very specialized heavy objects. To keep the fiberglass from sticking to the cardboard I covered the entire surface of the cardboard with clear packing tape.

Here’s the fiberglass repair piece after removing it from the mold.

…and after doing some initial trimming and sanding the repair piece.

After test fitting the repair piece, and giving it a thorough cleaning, bonding compound was applied to the piece.

Clamps were then used to hold the repair piece in place until the bonding compound cured. Here I’m using the hood skin and the hood frame to sandwich the repair piece in the middle of the two. A piece of cardboard was used to prevent the hood frame from being accidentally bonded to the hood skin.

And here it is, the repair piece bonded in place. At this point you can probably see what I’m going for. I’m using the repair piece as a backing plate so the repairs on the outer surface of the hood have something to be placed against. Although this repair does give the hood skin a bit of extra thickness it doesn’t unacceptably affect the fit of the hood frame.

Here’s the top side of the hood ready to receive some additional fiberglass matt and resin. You can also see that the fiberglass repair piece does a good job recreating the lip of the hood.

In addition to the damaged corner, the cowl of the hood skin was also quite flimsy. I decided to apply a few layers of fiberglass to strengthen the area a bit.

In addition to repairing the hood skin I also had to reattach the cover plate to the hood frame as shown below.

After a lot of fiberglass work, and the application of some body filler, here’s what the underside of the hood skin looked like. Ultimately, I determined that the repair piece worked well to repair the corner of the hood. However, a different approach was needed to recreate the lip along the curved edge of the hood cowl. After trying unsuccessfully several times to recreate this lip from fiberglass I decided to simply use some tiger hair body filler (body filler mixed with fiberglass strands) to build up the lip of the hood. After numerous applications of the tiger hair body filler, followed by some surface coats of regular body filler, I had the repair pretty well feathered out and looking good. It’s not the most elegant solution, but it’s effective, was relatively easy, and it looks decent.

Here’s where things went a bit downhill. I knew that the hood skin and hood frame needed to be bonded back together. I also recognized that the final shape of the hood would need to match the profile of the front fenders. However, the two didn’t want to line up very well on their own – the hood frame was too low at the high point of the fenders.

So, I decided to shim up the underside of the hood frame with some blocking at the high points of the fenders. Clamps were also used to hold the two ends of the hood skin down so they were tight to the frame. I also used some self adhesive felt pads, the same type you put on the bottom of furniture legs, to maintain an even gap along all edges of the hood skin.

After playing around with the blocking the fit looked good so I removed the hood skin and cleaned all the bonding surfaces with lacquer thinner before applying some epoxy adhesive.

  

In addition to the clamps and blocking, I also installed some punches between the hood and the ceiling of the garage to help develop the desired profile in the hood.

Next, to ensure the hood skin and and the hood frame were in tight contact I installed some screws to hold the two components together. This method of attachment was similar to the one I used to attach the rear fender to the rear clip. Without these screws there were several areas where the hood frame simply wasn’t in contact with the hood skin. Unfortunately, it also meant these holes would need to be repaired with fiberglass later.

  

Once the adhesive cured I removed the clamps, blocking, and punches and verified the fit up of the hood was still OK. Unfortunately, it wasn’t. At first it was acceptable but, over the course of a few days, the fiberglass relaxed and the hood sunk back down leaving it about 1/8″ below the top of the fenders. Not cool. Rather than slap on a bunch of body filler I separated the hood skin and frame again and repeated the process, this time building a bit more camber into the hood profile. I was less than impressed having to go through the entire process again but hey, stuff happens.

You can imagine how much less impressed I was when it didn’t come out right the second time either!

So, after having gone through all that extra effort, there was no way I wanted to do it a third time. This time I decided to do something a bit more drastic. On the left and right side of the hood I drilled a small hole through the top of the hood skin into the cavity formed by the hood frame. These holes were drilled near where the hood hinges are. Next, a similar set of holes were drilled into the cavity of the hood frame near the hood latches.

Then, at each of these four hole locations, I used just enough spray foam to fill a small length of the cavity. After the spray foam had cured I drilled another set of holes a few inches down from the holes located near the hood latches. I used these holes to fill the two sections of cavity located between the foam filler with fiberglass resin. Once cured this added resin gave the hood frame sufficient rigidity to hold the desired shape.

Suffice to say this ended up being a colossal pain as well as a giant time suck. In hindsight the hood repairs DEFINITELY should have been done before installing the front clip. It would have been much easier to adjust the profile of the front clip to match the hood. This is because the inner fenders are quite massive and have the stiffness and rigidity necessary to hold the front fenders in the desired profile.

So, after all that extra work, the many screw and drill holes were repaired with fiberglass matt and resin. Next, body filler was applied to provide a smooth and uniform surface finish. Several coats of body filler were applied and, following each coat, the surfaces were block sanded to feather the body filler into the surrounding fiberglass.

  

I addition to addressing the exterior surface of the hood the inside surface received a similar application of body filler to provide a uniform surface flush with the lip of the hood skin, and to smooth out a few other rough areas.

 

In addition to the hood the t-tops and doors were also prepared for primer. In the case of the t-tops the first chore was to remove the hardware and trim and then strip the old paint.

With the trim removed Citrustrip was used to strip the layers of old paint. To help the process along a stiff bristle brush was used to scrub the surface of the t-tops about 30 minutes after applying the paint stripper.

After scrubbing the surface, and allowing the stripper to sit for another 30 minutes, a putty knife was used to gently scrape the surface clean.

After about 3 applications of the Citrustrip here’s how the t-tops looked. I was fairly happy with the result but found the gray primer was being exceptionally stubborn. Rather than continue with the Citrustrip the surface was thoroughly washed with soap and water, and then with mineral spirits, to ensure all of the stripper was removed. Once cleaned the surface of the t-top was block sanded to remove the remaining primer to expose the underlying red primer and fiberglass.

  

Since the doors had already been stripped and sanded previously everything was now ready for primer. Consistent with the rest of the work completed to date the parts were primed with white epoxy primer from Southern Polyurethanes. Several coats were applied to each part to provide a good coating that completely sealed the fiberglass surface.

  

Overall the primer came out very well. I’ve found the Southern Polyurethane primer sprays easily, coats well, and provides a nice finished surface.

Next on my to-list is to reattach the hood and doors, complete a few odds and ends, and then get the car drivable so it can be more easily transferred to the paint shop. While the car is in the paint shop I’ll focus on the interior pieces and getting those ready for when the car is back from the shop.

But, that’s it for this update. Stay tuned for more updates!

 

If you have any questions about this update, or a project you’re working on, I encourage you to visit the Corvette Restoration Forum and ask your question! I’m there fairly often and, together with the other great forum members, you’re sure to get some great advice and feedback.