Sikaflex 715 and adhesive membrane
This is in the nature of a report/public service announcement.
In replacing the backup camera on my Itasca Navion, I had to remove three pieces of trim at the rear roof/wall juncture. These wrap around from the roof to the back wall (and a little on each sidewall), and are held down with screws on top. They're also the first line of defense against water leaks there, so they're caulked down. The local RV parts house recommended Sikaflex 715, so I bought two tubes.
This caulk differs from all other caulks I've ever used. A lot of high performance caulks are kind of stiff; not this product. It was slightly stiffer than melted ice cream. Mostly, this was OK, although at the ends of the corner trim, where they mate with the roof as it wraps down over the sides, I had to clean up some caulk drool and re-caulk after a couple of minutes, as it sagged away from the trim.
If you use this product, look up Sika's "RV Roof Repair Guidelines" (for some reason, I couldn't get direct link; search for that phrase on their website). These are quite helpful and include lots of information not printed in the tiny type on the caulk tube (like what to use for cleanup - mineral spirits - I used that knowledge often in this project!).
Have a bucket tall enough that you can hook the caulk gun's trigger over the edge, with the gun in the bucket, as the caulk will keep drooling from the tube (I used the shop trash can that I had by the RV for the various bits of trash).
Unless you are bald, wear a cap that you're not fond of - it's amazing how easy it is while climbing around by an RV to touch your head against the caulk. I didn't, and did a lot of rubbing my head with a mineral spirits-soaked rag.
It doesn't tool easily, because it's so soft; but if you need to tool it, use a strong paper towel or rag soaked in mineral spirits. I was able to get a good job at the ends of the corner trim, the only place you can see the caulk from the ground; the rest is just as it came from the gun.
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Winnebago curves the roof over the sidewalls, but, at the back, the roof ends in a sharp edge even with the wall. The joint is then covered with an adhesive membrane "tape." The guy installing that tape on my rig at the factory wasn't having a good day: the tape (too narrow to do the whole job in one course of tape) lapped in the wrong direction, didn't go onto the roof at all at the ends, and had some holes.
I confirmed with Winnebago that this is a butyl membrane, pretty well identical to a product used in construction for flashing window installations and the like. If you find you need to make some repairs on this area (or others using the "tape") on your Navion, and your RV parts house can't help you, call a contractor's lumberyard and ask for "butyl adhesive membrane." The slang term for this product can't be used in polite company; it sticks instantly to anything it touches and is tricky to apply because of that. But it holds like mad. It is NOT durable if exposed to the weather. The factory membrane on my rig had failed where the center and corner trim didn't quite meet (on purpose, as best I can tell), because the guy running the caulk gun didn't fill that area adequately. I'm hoping my more enthusiastic caulking will work better.
In replacing the backup camera on my Itasca Navion, I had to remove three pieces of trim at the rear roof/wall juncture. These wrap around from the roof to the back wall (and a little on each sidewall), and are held down with screws on top. They're also the first line of defense against water leaks there, so they're caulked down. The local RV parts house recommended Sikaflex 715, so I bought two tubes.
This caulk differs from all other caulks I've ever used. A lot of high performance caulks are kind of stiff; not this product. It was slightly stiffer than melted ice cream. Mostly, this was OK, although at the ends of the corner trim, where they mate with the roof as it wraps down over the sides, I had to clean up some caulk drool and re-caulk after a couple of minutes, as it sagged away from the trim.
If you use this product, look up Sika's "RV Roof Repair Guidelines" (for some reason, I couldn't get direct link; search for that phrase on their website). These are quite helpful and include lots of information not printed in the tiny type on the caulk tube (like what to use for cleanup - mineral spirits - I used that knowledge often in this project!).
Have a bucket tall enough that you can hook the caulk gun's trigger over the edge, with the gun in the bucket, as the caulk will keep drooling from the tube (I used the shop trash can that I had by the RV for the various bits of trash).
Unless you are bald, wear a cap that you're not fond of - it's amazing how easy it is while climbing around by an RV to touch your head against the caulk. I didn't, and did a lot of rubbing my head with a mineral spirits-soaked rag.
It doesn't tool easily, because it's so soft; but if you need to tool it, use a strong paper towel or rag soaked in mineral spirits. I was able to get a good job at the ends of the corner trim, the only place you can see the caulk from the ground; the rest is just as it came from the gun.
----------
Winnebago curves the roof over the sidewalls, but, at the back, the roof ends in a sharp edge even with the wall. The joint is then covered with an adhesive membrane "tape." The guy installing that tape on my rig at the factory wasn't having a good day: the tape (too narrow to do the whole job in one course of tape) lapped in the wrong direction, didn't go onto the roof at all at the ends, and had some holes.
I confirmed with Winnebago that this is a butyl membrane, pretty well identical to a product used in construction for flashing window installations and the like. If you find you need to make some repairs on this area (or others using the "tape") on your Navion, and your RV parts house can't help you, call a contractor's lumberyard and ask for "butyl adhesive membrane." The slang term for this product can't be used in polite company; it sticks instantly to anything it touches and is tricky to apply because of that. But it holds like mad. It is NOT durable if exposed to the weather. The factory membrane on my rig had failed where the center and corner trim didn't quite meet (on purpose, as best I can tell), because the guy running the caulk gun didn't fill that area adequately. I'm hoping my more enthusiastic caulking will work better.
