Every once in a while, someone asks us for a bit of sailing advice. We have a few sage suggestions (“Keep the people on the boat”, “Keep the water outside the boat”, etc), but high on the list is “Don’t hit the rocks”.
We try our best to follow our own advice, but our best is apparently not always good enough. While in a deserted anchorage in northern Patagonia, we ran Madrone solidly into an unmarked rock on the side of the entrance channel. So, one of the key goals of our time out of the water at Zimmerman Marine was to assess the damage and have it professionally repaired.
The first step of any fiberglass repair is to understand exactly how bad the damage is. For this, there’s no need for state of the art imaging equipment – instead, it just requires some solid tapping with a hammer. The hammer cracks the fiberglass where it’s damaged, and when the cracking stops it means that the laminate is still solid at that point. In our case, the damaged fiberglass turned out to be about a half inch deep radiating about a foot or two from the forward bottom corner of the keel.
Once the extent of the damage is determined, the cracked fiberglass is removed using an angle grinder with an abrasive disk. The laminate is ground back until solid fiberglass is reached – at this point, the edge of the ground area is gently tapered at a 10:1 or so slope back to the original surface. This results in a smooth, shallow divot where the damage originally occurred.
Once this prep work is complete, the repair can begin. Multiple layers of fiberglass cloth are cut to size, starting with a few patches about the size of the deepest part of the divot and then successive patches that are each a bit larger than the last, until the final layer reaches all the way to the edge of the original fiberglass. These patches are then wetted out with thoroughly with resin and sequentially pressed into the ground-away area until it is close to the level of the original surface.
Once the resin-impregnated fiberglass patches fully cure, the resulting new laminate is chemically bonded to the original laminate and the repair is as strong as the original boat construction!
At this point, it’s time to make the surface smooth and a match to the original shape of the keel. An epoxy-based fairing compound is applied over the repair; once it cures, it’s sanded back to leave a smooth surface. It often takes several iterations of applying compound and fairing it back to yield a completely smooth surface that matches the original compound curves of the hull design.
Once the fairing is complete, the repair is covered with a couple of coats of an epoxy sealer, and then the bottom painters are turned loose on the hull.
During all of these steps, it helps to have an experienced hand at fiberglass repair working on the project. We were very fortunate because Jeff at Zimmerman Marine is an artist when it comes to fiberglass. He did an absolutely professional job, and without sanding away all of our bottom paint it would be impossible to even tell that Madrone was ever parked on a rock.
As a side note, Madrone’s design calls for encapsulated ballast – the solid iron of her keel is completely contained within the bottom of the fiberglass keel. The advantage of this approach is that it eliminates the need for keel bolts, making it more or less impossible for the keel to fall off the boat (that’s another piece of sage advice we can pass along – “Keep the keel attached to the boat”). Nothing in boat design is either all good or all bad, though, and the downside of this approach is that if saltwater penetrates the fiberglass and reaches the metal ballast, particularly if it’s iron, corrosion can start. Our initial inspection of the keel damage suggested that it wasn’t deep enough to expose the metal of the keel to seawater, but we were very, very happy to have that suggestion confirmed once the boat was out of the water.
