Originally Posted by juro
Sounds like you speak from experience!
BTW I would think if bladderless, the sealing should occur after the stitching.
My instructions only applied to doing a fix on a pontoon with a bladder.
They also work well on float tubes.
If it's bladderless, then you can't really sew the patch on since you'd be creating lots of potential leak points with all of the holes you're putting in it. Also, you can't use a sewing machine since you can't open up the pontoon like you can with one that's just a cover with a separate bladder and has a big zipper on it. If it's bladderless, I'd do it this way. This is how I've repaired rips in inflatable boats.
1. Take a piece of patch material that's about 2" longer and wider than the tear and apply a very thin coating of Aquaseal to it, staying at least 1/2" away from each edge. If you're lucky enough to have a rubber bladder instead of a PVC bladder, buy a bike tube patch kit and use that for the patch and glue.
2. Place the patch inside the tube at the spot of the tear and center it under the tear.
3. Use a spoon to smooth out any air bubbles and to compress the patch and tube together. This is where it's extremely important that a) you applied a thin coating of glue to it and b) left a 1/2" gap around the edges. If you didn't, when you smooth it out you'll squeeze glue out and in the next step you'll glue the two side of the bladder together! The patch doesn't need to be glued right up to the edge. The purpose of patching from the inside is to provide a good air seal since an external patch will always be fighting the air pressure. The internal patch will be pressed against the tear by air pressure, sealing it more tightly.
4. Place a couple of phone books or similar heavy objects over the patch and allow it to dry overnight, then remove them and allow it to dry for another day. Since the interior patch isn't really exposed to the air, you need to allow plenty of drying time. If you can cycle air into and out of the bladder via the inflation valve, that will help a lot.
5. Cut a patch for the outside that's 2" longer and wider than the tear and glue it on using Aquaseal, an all purpose epoxy, or better yet an industrial strength fabric glue. They sell some of these at craft stores, though they can be tough to find. You really want to use something that's designed for fabric.