Rear Clip Repair: Part 4

In our last installment an area of poorly repaired fiberglass was identified in the area of the passenger side number four body mount. In this update work will begin on removing this shoddy repair and making a proper structural repair.

To start, the old repair, which consisted primarily of a thin layer of fiberglass mat, was removed.

To facilitate removal and construction of the new repair the splash shield (located right behind the rear wheel) was removed. A heat gun was used to soften the bonding compound and simplify the removal process.

With the splash shield removed a heat gun and putty knife was used to help loosen and remove the old repair material. As you can see, the repair wasn’t constructed very well so removal was fairly simple.

With the repair removed the extent of the repair became apparent. Not only was a significant portion of fiberglass simply missing, there were several areas of major fiberglass damage around the body mount area leaving the body mount hanging in place by only a few strands of fiberglass. In order to complete a proper and thorough repair I decided to entirely remove the fiberglass and steel bracket making up the body mount.

 

In addition, three major stress cracks were identified in the vicinity of the body mount. In the following photo these three areas have been identified with red arrows. The damage at each area was significant enough to require a full depth structural fiberglass repair.

Similar to the locations of fiberglass previously repaired on this project the area of damage was ground down, cleaned, and new layers of fiberglass matt and resin were applied. Several layers were first applied to the inside face, following by several layers on the outside face. Since several other similar repairs have been shown previously as part of this project I’ve decided to only show a few photos of the prep.

Next on the list was repairing the fiberglass body mount and steel reinforcing plate. Repairing the steel plate was relatively simple; it just needed to be bent back into it’s original shape. However, the fiberglass portion presented much more of a challenge. There really wasn’t much left of it to build off of.

To start the repair, the frayed edges were cut clean and the surface was scuffed with a 20 grit sanding disk to feather the edges where needed and to provide a clean, rough surface to accept the repair materials.

 

Making the necessary fiberglass repairs without a mold didn’t seem plausible here so, after a bit of thinking, I looked to the drivers side of the body for some guidance. Below is a top view of the number four body mount on the drivers side. Although the shape is somewhat different from what was needed on the passenger side, it seemed like a good starting point.

To create the mold I decided to use some expansive foam. My thinking was that the foam could be easily removed from the body and then trimmed as necessary to create a mold.

 

After covering the nut/bracket for the body mount with masking tape the general area was sprayed down with cooking spray to ensure the foam would not adhere to the fiberglass. Next, a small amount of expansive foam was placed in the opening. Keep in mind that a little foam goes a long way! Once in place the foam was left to cure overnight.

After being left to cure overnight was popped out of the body with a small putty knife.

Here you can see how the foam mold will be used to help form the reconstructed body mount. But, before starting any actual fiberglass work, additional components needed to be added to the mold to ensure the reconstructed piece could be easily attached back to the body.

First, a layer of aluminum foil was placed over the foam to ensure the fiberglass materials could be easily released from the mold.

Next, additional blocking (essentially blocks of wood wrapped in aluminum foil) were added to the sides of the mold. Adding these blocks will allow for the development of flanges on the sides of the piece as necessary. These flanges will be used to help affix the repaired body mount back to the body (all of this will make more sense when you see the photos later…) With this effort complete it was now time to start placing fiberglass and resin. Several layers were applied to provide an overall fiberglass thickness of about 1/8″.

Here’s the completed fiberglass mount after some preliminary trimming. It’s not perfect, and it will require some modifications, but I think it’s a lot closer than it would have been if it were free-formed without a mold. With this effort well underway I switched gears slightly to start developing some of the other repair components necessary to reconstruct the area of damage.

For the remaining components I again looked to the drivers side for guidance on how to shape and form the back face (identified by the red arrow) and inside face (identified by the green arrow) of the rear wall.

Once again I decided to create a form for both of these elements. The form for the inside face was simply created by combining a piece of 2×10 lumber along with several pieces of clapboard siding to recreate the required angle.

A layer of aluminum foil was placed to facilitate release of the fiberglass and then two lines were drawn on the foil to help delineate the size of the repair piece needed.

Next, several layers of fiberglass matt were applied to develop a repair piece with a total thickness of approximately 1/8″.

Once cured the fiberglass was removed and set aside.

Several other repair pieces were then created in a similar fashion. Each piece was built up to about 1/8″ total thickness using fiberglass matt (not fiberglass cloth).

With each of these pieces completed the next step will be to trim and assemble them on the car. A new update should be coming in less than a month so check back soon for more progress! In addition, I’ll likely be making a big announcement regarding a new addition to The Corvette Restoration Page along with the next update. It’s something I’ve been working on for quite some time and I think folks will really find it useful! Stay tuned!

 

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