Our 5-year-old Zodiak lightweight RIB has always had very slow leaks in both air chambers. Every week or so I had to top up both sides. We store it inflated hanging from the garage ceiling in the winter and after about 3 weeks it would get all flaccidy. (I love new words!) I had tried a soap bubble test and couldn't find anything and thought maybe it was air seeping through the cloth. Last summer we also developed a small water leak where the hinged transom joins the fiberglass bottom. While locating that I found a very tiny set of air bubbles coming from the same area. It was where a bunch of layers come together and no way to seal from the outside so I tried this interior sealant. I followed the instructions carefully and double or tripled the amount of flip-flops, tilts and rotations to make sure it got to the right area. That was in mid August. We used it the rest of the summer, hauled it home and hung it in the garage and have not added any air. The stuff was a bit spendy and I only used half of it on the 10 footer but the results were worth it.