Gap between roof and front cap

Gjac wrote:

msmith1199 wrote:

Gjac wrote:
msmith the reason why MH mfg don't do a lot of things is for cost reasons. Caulk is a lot cheaper than 3M 5200. Is you main concern the difference in CTE( thermal expansion) and the roof pulling away from the front cap? Or the vibration while driving? Any mechanical fastener that you use, screws or bolts will restrain the cap and roof. If you have to replace the front cap or FG roof, which I have never heard of, there would be much bigger problems like a front end collision.

My reply to this earlier didn't seem to post? To answer your question, yes on thermal expansion mainly. As for if I have to replace them you're right, it would likely be from some type of physical damage and in reality that would be the insurance companies problem if they did have to replace both. And yeah, I understand the RV people wanting to save money, but since this front seam seems to be the main source of leaks in many RV's, you would think if gluing the two pieces together would fix that they would all be doing it. Do you know of any manufacturer who did glue them together? Have you done it yourself?

To answer your question about the CTE of FG it is about .000008 ins/in/degree F assuming an isotropic layup( cross plys) which most are. The FG caps and FG roof is the same materials (polyester resin and E glass) the same CTE which is very small and I would not worry about. Finding out what adhesives or other materials that MFG's use is almost impossible to determine from their web sites or brochures. Most are described in marketing terms not engineering specs. From what I have seen on mine and others is just butyl tape between the faying surfaces and plain carbon screws that rust. Polyester resin, E glass, butyl tape, and plain carbon screws are cheaper than Epoxy, Kevlar or carbon fiber, epoxy adhesives or Stainless steel screws but they work. I would not overthink this repair but hopefully this post alleviates some of your concerns. The only thing I would do first before adding the adhesive is to install the screws first and see if the gap goes away without any buckling if it does just remove the screws then add the adhesive or caulking if your are still worried then reinstall the screws and tape or caulking and believe that your repair will last forever. Hope this helps.

You sound like you know what you're talking about, so I'll give this some more consideration. Whatever I do, when I put the screws back in I'm going to start in the middle and then work it out to the sides. So if there is any play in it that will force it out to both sides, versus one side, and hopefully I can deal with it. I'll just have to see what happens.