Superformance inner body to outer body bonding

[Craig T]

As "m5extc" suggests and after a conversation with Blas I think the best way to perform the repair is to do as they have suggested. Cut out the old urethane (I used an old steak knife, it has reach and flexibility, better than an exacto knife or other tools that I tried) and restore the joint with new sealer. As Blas suggested after cleaning, degreasing and roughing up both surfaces, work in and apply a thin coat 1 to 1.5 inches wide of urethane to both surfaces to ensure and promote better adhesion and a wide base of contact.
My next step is to apply a 2 inch wide full length strip of fibreglass gauze (something like fibreglass mesh drywall joint tape, I used a 2 inch fibreglass tape used in sealing high pressure ductwork) and embed it into both surfaces of the first coat of urethane. Next apply a very heavy 3/4 to 1 inch deep filler coat of urethane to the fibreglass gauze and fill the cavity flush, then smooth to blend both panels. The fibreglass gauze does two things in my view:
1) provides a backing for the newly applied urethane to provide a uniform, smooth and regular joint inside the engine compartment even though it cannot be seen in most places. It eliminates the original irregular erratically pumped in mess from the factory. Maybe I just got a bad one.
2) the fibreglass tape will provide additional strength although it may not be needed. The urethane sealer is very strong on its own.
The sealer that I used was from Home Depot here in Canada, "Dap" Polyurethane, "Premium roof and flashing sealant", black in colour, guaranteed 50 years. At $6 a tube.
I think it is close or close enough to the very expensive "Sikaflex" product and will do just fine here. The Dap product has excellent adhesion, flexibility, is waterproof, weatherproof and paintable and cheap.
The front quick lift supports or bumperette supports must be removed to get the best results and access to the joint around the nose and inner fender.
In my view this repair still provides significant support for the front outer shell and provides a strong flexible joint. Hopefully it will also eliminate some or all the front end body "jiggle" and rattles that I currently experience.