Sealing the Joint Between Cap and Top of Van on B190

[Jazzy190]

Hello, I am cross-posting this on the various Airstream/B190 forums, so I apologize for redundant posts and message length.

We have noticed a potential source for a small leak into the back right corner of our newly-acquired B190. (See photos for context.)

* Questions: (1) Does anyone have any recommendations on what sealer to use between the B190 cap and the top of the van, and how to do the sealing in this area? (2) Is it possible/advisable to apply a sealant around the perimeter of the joint, or is this not advised (should we just seal the isolated problem area?)

* Details: The culprit seems to be an area where the bottom of the top cap/hull meets the top of the van (as shown in photos). We think the water must be coming from the described joint area because the water "rolls down" the inside of the back door and also touches slightly into an area/corner of the wardrobe closest to the back door. The back door window seals look fine to us. There is no apparent water coming from the bathroom fan. I don't think the origin is the toilet vent because there is no water inside other parts of the wardrobe or in the bathroom, and there are no other signs of water anywhere else inside the B.

I have read info. on the forums about various sealants applied for different purposes, but I have not been able to locate a sealant for this particular purpose in any post (I am listing some below). Because the junction touches on fiberglass and metal, both, I want to make sure I prep the area properly and use the right sealer. I also do not want to "overseal" and cause water to accumulate under the sealant placed in this joint area (I remember reading a post stating this had happened to someone else who used putty and the putty caused water to pool in the area.)

* Potential Solutions: Some sealants I have read about include Sikaflex 221 White or 715.

* Sikaflex 221 White (for roof seams, seals and bonds. The post I read recommends using Eternabond spray cleaner to prepare surface.)
* Sikaflex 715 (used around fans, vents, skylights)

Any feedback offered on this subject is much appreciated!!

[InterBlog]

I don't know the details of your application (no photos), but FWIW, I've used Sikaflex 221 in numerous applications, and all of them were successful.

I put it on our Interstate's roof in lieu of the previously-applied self-leveling stuff that aged out of effectiveness (details here).

Not wanting to waste the residual contents of a caulk tube, I also used the same product on our house, to seal the exterior brick penetration where the air conditioning condenser lines ran up to the rest of the components in the attic. Those kinds of penetrations are notorious for being rodent superhighways. The Sikaflex performed wonderfully in that application, too.

It's tricky to apply and different people develop their own methods. I discuss that in the link above.

[Jazzy190]

Hi, Thanks for your reply. I am not sure why the images did not post. Probably size. My apologies. I am adding them here.

An update: I retested the door's weatherstrip, and it seems the culprit is the weatherstrip, after all. Nevertheless, I still need to fix the issue above. Some other folks suggested Lexel and 3M Marine Adhesive/Sealant 5200. It seems the Sikaflex 221 is more "gummy"?

[InterBlog]

Sikaflex 221 is very sticky, yes. That's a good thing - that's what makes it adhere to what otherwise might be tricky surfaces to work with.

If you've got an opportunity to add some kind of flashing in the area you describe, that might not hurt.

[Jazzy190]

Thanks so much for your advice. Do you think the 221 can be "smoothed" out or will, as your wife put it in the blog article you referenced, remain "ugly as sin"? If it can be smoothed out, what do you recommend? e.g., dip finger (or applicator) in mineral oil, water, etc. Thanks again!