Re: Hypalon Repair
It would be better if you posted a pic. I am assuming that you are saying you have a leak that is really close to the fabric that attaches the rope rail to the boat, similar to the one in the picture here.
It also sounds like that leak is in the middle of a tube seam with it's reinforcing strip. It maybe good that the leak is straight through the seam reinforcing strip, in that you can just patch it. Often leaks in a seam itself "travel" along and actually leak at some other place out the side of the reinforcing strip. Glueing a patch over this strip may just work, but if the seam itself underneath has issues the pressure may just work itself to another place. You will find out! Here is a pic of patch over an irregular surface. It has held up on the bottom of my boat for three years so far. The original owner damaged the fabric surface trying to effect repairs. After I repaired the floor to tube seam I had a spot that wasn't covered. I got lots of recommendations regarding the use of liquid rubber or other "paints" that would cover the spot and avoid a patch. The advice I got was that patches lowered the resale value of my boat. I didn't care about that. The boat is very sound, but I don't have any real expectations regarding resale and I felt that liquid rubber wasn't going to provide the level of abrasion resistance that I desired. I would rather have a "funny looking repair" that is bullet proof and it is repairable should it fail. Better to receive some scorn from other inflatable owners rather than have a tube failure beaching in a remote location. I am patch happy!
One of the "truths" of repairs is that small patches will not hold. That is definitely not true for well bonded patches. Here is a shot of my tow ring and it's mounting base. I have another one of those damaged fabric spots covered by the larger patch to the side. It is NOT a substitute for correctly repairing a failing base mount. It is only to cover the damaged section of fabric I inherited. It was recommended to me that I use a larger piece of fabric underneath to neatly cover the larger area before I reinstalled the failed tow ring mount. But as you can see aesthetics don't mean anything to me. The really small dinky little patch covers a worn spot on the base mount itself. The heck with liquid rubber or an expensive replacement tow ring assembly. This little patch has traveled far and wide and isn't going to come off easily. It violates the 2" rule because it isn't even remotely 2" big. Yes, it doesn't have to resist air pressure. But it withstands a lot of abuse and I am confident that it could patch a small puncture and remain in place. I had to replace a large circular patch on my boat that was "blown" by tube pressure. The patch had a big "bubble" in the middle. Yes, the extra 2" border was still holding, but that is not what I consider to be a good repair. Relying on the 2"border to hold a bad glue job is foolish. The air pressure will work it's way outward inevitably. If the patch is failing right over the leak it isn't going to last. If a puncture is bigger than just a small pinhole it needs to have a backing patch on the inside too.
It is true that resale value suffers when you add patches. All sorts of dodges are used by some to avoid the appearance of a repair. Everything from large "wear surface reinforcements" that look almost original to installing a d ring over a leak and another one on the other side to make it look like accessorizing rather than patching. You need to decide what is best for you. It is absolutely possible to work down the edge of an overlapping glue job and truly seal a patch. It is also possible to use a patch that is smaller than the 2" border rule if necessary. That said, any repair has a limited life span like any glued seam itself. If possible you should consider the possibility that you will have to revisit the repair eventually. Those sealers you slosh around inside your tube should only be used as a last ditch effort on an old boat. They make repairing large cuts or holes almost impossible (you have to get all of the sealer off to install an inner patch). Hope this helps you and at the very least it will show everyone what a true pinhead I am! Gluing is easy, but a strong bond takes care, low humidity, proper prep and that makes the 2" border rule a guide not a rule.