Gap between roof and front cap
When I first bought my motorhome (12 years ago) I noticed a lot of caulking on the left side of the seal between the one piece fiberglass roof and the front cap. It was obviously that there was a gap...
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Builders love those carbon steel self taping screws. I'm slowly replacing every exterior screw I can find with stainless. I think I'm on my second or third box of 100. Work great in sheet metal not so much in wood or fiberglass. My thoughts are they drill out too much material for the threads to bite into with materials other than metal. Most of what I've removed were in pretty bad shape below the thread with rust Which is why I'll coat the thread on the stainless as an added protection against water ingress.
For the roof seam I used 8 X 1" SS screws predrilled into the lite ply the roof is sheeted with. Roof is EPDM. Both the front and rear had trim pieces the I removed. My thinking is the same as msmith in that the trim is a big washer. I did the front four years ago and 30,000 miles without a problem. Former owners just kept add more and more sealant. Bigger the glob, better the job I guess.
Same with the rear but I didn't have the big gap with either end. I was able to lift the cap and slip butyl tape between the cap and the roof where I could. Pretty much the entire length except maybe the last three or six inches Call it suspenders and belt with the EternaBond tape covering everything including all the screw heads. The rest of the coach will rot some day but all the EternaBond will still be there.
Since you're looking at nine feet or so of an EternaBond run it's real easy to not get it down in a straight line across the width of the coach. About like installing floor tile. Get the first run off center and by the end it has a 90 arc in it. What I did was to mark reference lines every couple of inches and lined up the edge of the tape as I went along. Only remove a couple inches of the back material from the tape at a fine. EternaBond is real sticky and once it contacts something it's real hard to get off. If two pieces get stuck together it's game over. You'll never get them apart.
For the roof seam I used 8 X 1" SS screws predrilled into the lite ply the roof is sheeted with. Roof is EPDM. Both the front and rear had trim pieces the I removed. My thinking is the same as msmith in that the trim is a big washer. I did the front four years ago and 30,000 miles without a problem. Former owners just kept add more and more sealant. Bigger the glob, better the job I guess.
Same with the rear but I didn't have the big gap with either end. I was able to lift the cap and slip butyl tape between the cap and the roof where I could. Pretty much the entire length except maybe the last three or six inches Call it suspenders and belt with the EternaBond tape covering everything including all the screw heads. The rest of the coach will rot some day but all the EternaBond will still be there.
Since you're looking at nine feet or so of an EternaBond run it's real easy to not get it down in a straight line across the width of the coach. About like installing floor tile. Get the first run off center and by the end it has a 90 arc in it. What I did was to mark reference lines every couple of inches and lined up the edge of the tape as I went along. Only remove a couple inches of the back material from the tape at a fine. EternaBond is real sticky and once it contacts something it's real hard to get off. If two pieces get stuck together it's game over. You'll never get them apart.
