Two years ago we bought a used 11’6″ Achilles Inflatable RIB. It had a gouge in the fiberglass bottom and a patch on the front pontoon. Obviously something had been dropped on the dinghy, but it was holding air at the time and for the price we didn’t care that much. After two years of use and neglect (left tied to the dock in the summer heat uncovered, left out in the winter uncovered and full of water), the dinghy (renamed SS Floppy) was losing air minute by minute (I finally forced Rich to dig the cover out of storage and put it on when we weren’t using it). On top of that, Rich put a new hole in the port pontoon when he landed striped bass. Late last year when it was raining quite a bit, the front and port pontoons were mostly flat most of the time, the dinghy filled with water and was on the verge of sinking with our Honda outboard. We’ve had some very Spring-like weather here in California for the past few weeks, so Rich decided to try to fix the dinghy for good. Plus, our neighbor bought a floating platform for his fishing boat and he wasn’t using it so he offered it up to us so we could fix the dinghy. Rich spent two days trying to patch the large gash in the front pontoon. The first patch failed miserably. The second patch stuck, but he used the one-part West Marine glue and it’s already starting to leak very slowly. The patch for the hole from the striped bass spine seems to be holding just fine. Later this year Rich is going to redo the failing patch with a two-part hypalon adhesive which is supposed to hold much better.Compass Marine had some info about cleaning dinghy bottoms so I searched there and he suggested using an acid like oxalic acid. Unfortunately I didn’t have any oxalic acid, or so I thought. Rich brilliantly suggested that the teak brightener I used all last summer had acid in it. We dug the Star Brite Teak Brightener out of the shed and sure as shit it has oxalic acid.
So back at the dinghy I dripped a little of the acid on the fiberglass bottom and the gunk immediately came off. I put the acid in a spray bottle and misted it over the entire bottom then used a nylon-bristle brush to work it in then rinsed it off with water. I was a little worried using it on the hypalon and near the seams but a quick google search for “hypalon and oxalic acid” found that the two are compatible.
I’ll admit that using the Star Brite Teak Brightener was more expensive than using regular oxalic acid (like Bar Keeper’s Friend), but it’s what we had on hand and the West Marine closest to us closes at 2pm on Saturday and is closed on Sunday’s (a totally worthless WM location IMO). Next time we attempt this I’ll have BKF on hand. I’m going to get some anyway just to have on hand for cleaning in general.