3M 5200 Marine Sealant et al

[Ranger_Tim]

I currently go over my camper religiously looking for chances of leakage at least every six months. Seams on the roof, windows, etc. are checked for any signs of cracked sealant or separation. I treat them with Dicor in the two varieties, self leveling and goopy. This past trip it rained for three solid days and I was trapped inside a lot of the time. I began to ruminate over how well protected the unit was.

When I was on the east coast I grew up using the 3M sealants for marine industry, notably 5200 and 4200 caulks that came in squeeze tubes and cartridges. These lasted for many years in salt water. They would also go through season after season of abuse from freezing and vibration. I can't believe there is anything that vibrates and moves more than a boat pounding the waves. Those sealants are tough, last for a long time and don't let go. I even used them to mount lighter weight things to fiberglass hulls with no screws with success.

Why doesn't the RV industry use these? Is the Dicor superior because of flexibility? Lots of folks tell me to switch to Sikaflex products. I know people scream not to use silicone but I never hear why. Where is the holy grail of information on all things RV caulking?

[gbopp]

Ranger Tim wrote:
I know people scream not to use silicone but I never hear why. Where is the holy grail of information on all things RV caulking?

Everything I've read on the forum about not using silicone is because nothing will stick to silicone, including other silicone. So, in theory, if you need to recoat a seam the new silicone will not stick to the old.

Maybe that was true with the original silicone caulks? And maybe the newer silicone caulks don't have that problem? I don't know.
I've had good luck with Dicor caulk but, I would consider using a different product if I knew there was not an adhesion problem.

The RV Industry probably uses what works and is the cheapest.

As for finding the Holy Grail on caulking, opinions are like other body parts, we all have one.
I don't know if there is a one size fits all answer.

[srschang]

I can only answer one of your questions. Once silicone caulk is applied, it works well for a long time. But it eventually needs scraped out and replaced. Unfortunately, even if you do a great job removing the silicone, and it looks spotless, there is still a film of silicone on the roofing/trim/whatever you scraped it from. Nothing will stick to that film, not even new silicone caulk.