Seal and trim for roof

[JetSet]

Hey there! I'm doing the fly-the-plane-while-you-build-it method. I still haven't finished building my camper, but already have it on the road.
My roof exterior is made of three sheets of plywood, giving me two butted edges. These butts aligned with rib that run the length of the butt, so I figured with all the construction adhesive that I used that I would have a watertight seal. But, after 4000 miles of travel I'm seeing evidence that water is finding its way into the roof.

I would like to put some sort of sealant along the seams, but also maybe some sort of trim to cover the sealant and make things look nice. I would settle for a pvc-type plastic if it was concave enough to cover the sealant and some of the small mis-alignments in the butts. I haven't found any trim that fit the bill for that.

Anyone out there tried something like this, or have any wisdom to share?

You can see my build journal here.

Cheers!

[Zach]

Cool build! I really like those cabinets on the inside!

If you can find or order some aluminum flat RV insert trim, that may be your best bet. Set it on a strip of butyl tape, using screws to draw it down against your roof surface. The butyl tape will squeeze into all the nooks between your roof skins, and then you could run a bead of polyurethane sealant (not silicone!) on each side of the aluminum strip.

This is example is anodized black, but you could get silver or probably even white. And then you would need the vinyl insert that slides into the channel and covers the screws.

https://www.recpro.com/rv-insert-roof-flat-trim-black-92/

Or they even make just flat trim molding, where the screws would be exposed. It would be set on a strip of butyl tape, just like the insert trim.

https://pantherrvproducts.com/ap-products-021-87201-8-flat-aluminum-trim-molding-white-8-ft/

You would just have to get creative at the ends of the strips where they come flush with the side wall since you don't have the aluminum roof edge trim.

[JetSet]

Thanks for that! Yeah, the creative at the tip-ends part has me head scratching