C3 Corvette Fender Flares - Open Wide

The idea for flaring the fenders on our Stingray project was to do a custom flare, and retain the original type of design, just exaggerated. The first step is to mark the primary cut line on the OEM fender lip. The plan is to retain the original lip, so a cut line was marked at the apex of the original curvature from wheel lip into quarter.

A few position lines were drawn radially through from the fender lip to the quarter to aid alignment later, and the outer fender was cut along the marked line with a cut-off wheel in an air-powered die grinder.

While making the cuts, it is important to be aware of the double walled and flange-bonded area in the lower wheelhouse. We cut the inner wall flush and then removed the outer wheel lip section.

Since the fender flare will be bonded inside and out, the inner wheelhouse needs to be ground and cleaned so any fiberglass work in here will adhere. We cleaned to an area of about three inches all around the inside of the cut to bare fiberglass.

A set of five steel brackets were formed to bolt the wheel lip back in at a new location, spaced out from the original position. The lip was moved out 1.250-inch at the top center, about .850-inch at the front bottom, and .950-inch at rear bottom. This positioning subtly tips the edge out more at the top center, and allows a gentle sweep off the door edge outward.

The metal brackets were made of thin flat sheet metal, so they can be bent to a curve and screwed through the body at the quarter and the fender lips. The brackets were slotted at the mounting hole to allow adjustment in or out.

A simple wire gage is used to make a line of sight determination of the height of the relocated wheel lip, which can be adjusted by the curve of the mounting brackets. Our final position was just slightly raised from stock (about 1/8-inch). Since the lip is spaced out, the radius of curvature of the lip will no longer meet the quarter, and given the original angle of the lip, the joint needed to go up about as much as out, so a tape line was set at 1.25 up off the quarter cut, and tapering slightly to the sides.

Once the final position was set and locked-down with the brackets, the quarter and wheel lips were cut again. The wheel lip was cut to remove the radiused part, leaving about 1/2-inch, tapering out to just the lip edge at the front. The position was already set with the brackets, since removing this material loses the position reference.

Here we have the quarter after most of the cutting. The area between the lips and the quarters will be fabricated to create the new flared fenders.

To ensure a good bond, the edges of the original fiberglass were roughed with a carbide bit to bare fiberglass.

The next step was to build a mold from the inside. We began with a layer of really heavy-duty and sticky duct tape, tightly laid in strips from the inside.

To add strength and form to the mold, thin cardboard sheets were cut in sections and fitted onto the sticky side of the tape from the top. The mold was made very precisely, using paper patterns for the cardboard to fit together along the joint, edge-to-edge, without overlap, like a puzzle. The ideal was to gain full purchase on the edge when the fiberglass goes in later, and near perfect shape when the'glass cured.