We have a 2012 3170 with the famous crack. The crack extends at a 45° angle downward from the lower rear corner of the driver side slide cutout. There has been much discussion about the crack on this forum, some people claiming it to be the result of a serious structural defect. Some say the crack is caused by a missed well in the aluminum superstructure. Forest River has apparently agreed to fix some of them. In order to make the weld, the fiberglass skin must be ground out in a three or 4 inch circle so the heat of the weld will not damage the fiberglass and then that fiberglass, and the corresponding gelcoat, replaced. I took a less invasive route. If there is a missed weld I left it and with a Dremel tool ground out about a quarter inch groove to grind out the crack from the gelcoat. There was no visual indication of any cracking of the fiberglass wall itself. I filled the quarter inch groove with flexible epoxy and put a short piece of white electrical tape over it to keep sun off of it. The fix is about one quarter inch wide in about 1 1/2 inches long. You'll never notice it and I haven't ground out a 4 inch hole in the fiberglass wall of the coach. I've had fiberglass boats patched before, and the patch color is never right. If for no other reason, because the patch will fade differently than the original gelcoat. We have a total of 19,000 miles on the unit. We have put 4000 miles on the unit since the fix, some of those miles on a very rough pavement, and there is no further cracking.
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