Re: Inflatable Patching
While 5200 will stick to the PVC it does not provide structural strength. It is also very difficult to remove, which makes any subsequent repairs problematic. Use the two part PVC glue.
A wee bit of separation is usually a sign that the bonds are deteriorating. When I repaired my floor seams and transom seams I pulled apart any seam that would come apart without damaging the pvc surface layer of the tube material. It was very disheartening to extend the separated seams and un wrap my transom, but it is what needed to be done to have a boat with integrity. My floor seam did not come apart all the way around and one of my tube to transom joints was solid. My point here is that if you are going to go at it with glue make sure you aren't just doing a superficial job. Many will say that once a boat starts losing seam integrity it isn't worth fixing. Depends on your time and desire.
1.5 " is a little tight but probably would be fine. I have a patch that is smaller than I usually go and it has held up just fine.
Sounds like your boat really is starting to de bond. Only you can say if it is worthwhile to repair. After you get done sealing the obvious and have some floor integrity be sure to fillt he boat with a few inches of water and check for leaks. I found a couple of seaping small leaks where the floor seam goes over tube seams. Opened up those spots a little and glued them too.
If you are methodical, do the proper prep, mix your two part glue accurately, stay within the environmental limits for humidity and work in stages (don't overlap an uncured repair) you can get strong bonds and a reliable boat. If you search back through my old posts there are some good descriptions and photos of transom repair.