How to make a watertight seal between oil paint coated marine plywood and polypropylene

I need to make a watertight seal between a sheet of marine plywood coated with oil paint, and a 5mm sheet of polypropylene, both at right angles to each other.

Both are well supported structurally independently of each other.

Will silicone do the trick or are there other alternatives?

rickharris5 years ago
Hardly anything (I think including epoxy) will stick to polypropylene. Most Polyprop things are welded together.

I suggest you make a mechanical joint with nuts bolts and some right angled brackets. Then you may be able to seal the joint with the silicone just to caulk the, hopefully small, gaps.
Burf5 years ago
Silicone doesn't bond well with some plastics, I would use a marine grade epoxy and make sure the areas to be joined are roughed up with coarse sandpaper before applying the epoxy.