Non-Structural Sheet Metal Repair Table
JOINT AND REPAIR TYPES REFERENCE
Backer Panel Joint
Backer Panel Joint
Door Skin Door Skin Replacement
Liftgate Inner Panel DO NOT REPAIR
Liftgate Inner Panel DO NOT
REPAIR
Liftgate Outer Panel Liftgate Outer Panel
Body Side Aperture / Quarter Panel Side Aperture / Quarter Panel
Metal Fatigue/Stress Cracks Metal Fatigue/Stress Crack
Backer Panel Joint
Overview: Backer panel procedures may be used to achieve a smooth joint between panel sections. The backer
panel works well in areas where there is not enough room to smooth or feather in an overlap joint. The backer
panel joint is a common repair for rocker panels, quarter panels and body side apertures.
NOTE: OEM panel replacement such as a quarter panel, side aperture and rocker panel will always require
the weld bonding procedure at the pinch weld flange area(s).
Preparation:
NOTE: Be certain vehicle is evenly supported at normal suspension points.
1. Restore structural dimensions as well as all related mating flanges.
NOTE: It will be difficult to abrade the underside mating surface of the original panel, however this is
an important step and should be done effectively.
2. Create a 50 mm. (2 in.) backer panel out of an unused portion of original or new sheetmetal panel, whichever
contains the appropriate shape. Be certain it has a precise fit to the back of the panels it will join.
3. All paint, primer, adhesive and any other corrosion protective coatings must be removed from the mating
surfaces as well as the backer panels themselves, prior to application of adhesive. Grind a 25 mm. (1 in.)
contact area on all panels where backer panel bonding will take place. The metal should be completely bare
and shiny in appearance, if the metal appears pewter in color all of the galvanized coating has not been
removed.
4. Pre-fit the backer panel to the panel(s) being joined, to ensure proper fit. If screws will be used to hold the
panels in place during curing, dry fit them now to be certain of proper fit later. There should be a 0.8 - 1.6
mm. (1/32 - 1/16 in.) gap between the two outer panels, no gap on backer panels.
5. Without a mixing tip attached, purge a small amount of structural adhesive from the cartridge. This will ensure
an even flow of both components.
6. Attach a mixing tip and dispense a mixing tube’s length of adhesive from the cartridge.
Application:
NOTE: Review temperature curing chart before application of any adhesive.
NOTE: Refer to the structural adhesives manufacturer for information on work, handling and curing
times.
7. Apply a 10 - 13 mm. (3/8 - 1/2 in.) bead of structural adhesive to the bare metal mating surfaces of the backer
panels. Evenly apply the adhesive over the complete bonding surface. Apply a 10 - 13 mm. (3/8 - 1/2 in.) bead
of structural adhesive to bare metal mating surfaces. Use a body filler applicator to level the adhesive, making
sure to cover all bare metal to protect against corrosion.
8. Position the new backer panel(s), making sure not to separate after contact. Lifting will create air bubbles and
weaken the bond. Adjustments must be made by sliding, not lifting the panel(s).
9. Clamp tightly and evenly. Adhesive has glass beads that will prevent complete squeeze out. Install screws to
the "hard to clamp areas".
10. Remove excess adhesive from all joints prior to adhesive cure.
11. Allow adhesive to cure, per manufacturer recommendations. When fully cured, expect the acrylic adhesive to
be a little tacky, as this is a normal characteristic of the adhesive.
12. Remove clamps and screws.
13. Repeat procedure for installation of new panel.
RU 31 - Collision Information 31 - 19
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