Pierre B
05-17-2011, 08:28 AM
This caution comes to me from my past experience with a fiberglass-bodied 1907 Lotus Europa I had repainted. Admittedly, the Lotus fiberglass was thinner and more frail than what we have on our FFRs. But still, this fender precaution is even standard procedure in high end shops that modify 911 Porsches with fiberglass fender flares.
With the Lotus, rock hits to the underside of the fender fiberglass resulted in stars in the car's paint finish. Not good. On my MKII, I lined the underside of the fiberglass in the fender wells with foam padding. The Porsche shops I mention above typically use neoprene, but I wanted something less expensive. Camping supply stores (like LL Bean, Eastern Mountain Sports, etc.) sell foam ground mats (about 3/8-inch thick) for campers to place under their sleeping bags. I bought two for I think about $8.00 each. One of these will do both a front and rear well. Trimming is easy, since it is done in place in the actual wheel well from beneath the car. The mat is first cut to length, then pressed into the well and marked with a felt-tipped pen. Cutting and trimming is easy. I secured the pads with silicone, using about half a cartridge on each fender pad. Once pressed into place, the pads tend to stay in place until the sealant sets up. The final touches involved running a bead of silicone around the outer edge of the pads so they won't start to pick off later, then painting the padding black. Done. Now that I think of it, I may have used urethane sealant instead of silicone, since I had no problem getting the black paint (SEM from NAPA) to adhere to the sealant. Result-no stars! One last parting thought: I did this during the original build, so everything was clean under the fenders. Retrofitting is easy, but make sure to clean the underside of fiberglass first. I guess some of us may have used truck bed liner for the same purpose, but I have had no experience with that material.
With the Lotus, rock hits to the underside of the fender fiberglass resulted in stars in the car's paint finish. Not good. On my MKII, I lined the underside of the fiberglass in the fender wells with foam padding. The Porsche shops I mention above typically use neoprene, but I wanted something less expensive. Camping supply stores (like LL Bean, Eastern Mountain Sports, etc.) sell foam ground mats (about 3/8-inch thick) for campers to place under their sleeping bags. I bought two for I think about $8.00 each. One of these will do both a front and rear well. Trimming is easy, since it is done in place in the actual wheel well from beneath the car. The mat is first cut to length, then pressed into the well and marked with a felt-tipped pen. Cutting and trimming is easy. I secured the pads with silicone, using about half a cartridge on each fender pad. Once pressed into place, the pads tend to stay in place until the sealant sets up. The final touches involved running a bead of silicone around the outer edge of the pads so they won't start to pick off later, then painting the padding black. Done. Now that I think of it, I may have used urethane sealant instead of silicone, since I had no problem getting the black paint (SEM from NAPA) to adhere to the sealant. Result-no stars! One last parting thought: I did this during the original build, so everything was clean under the fenders. Retrofitting is easy, but make sure to clean the underside of fiberglass first. I guess some of us may have used truck bed liner for the same purpose, but I have had no experience with that material.