BANG The account which follows arises from an unexpected encounter with an underwater promontory of the Canadian Shield rock at position 45o 07.256’N, 80o 09.767’W while making passage from the small craft route through the 30,000 Islands out into the open waters of Georgian Bay. During an early September cruise my wife Jan and I had traveled into Port Rawson Bay, a pleasant and secluded anchorage about an hour’s motoring north-east from Fryingpan Island (Sans Souci). Having not previously visited the area I prepared printed sectional charts from Fugawi/NDI software (Chart 2202) showing in large scale the route to and of the bay. These charts were inserted into a transparent sleeve for convenient reference in the cockpit. Comparing these printouts to passing land features, the scrolling display on the chart plotter and the water depths indicated by the forward looking sonar (FLS – displays the bottom profile from ahead of the boat to below the keel), I was impressed with the detailed accuracy of the charts and the precision of position-indicating performance of the DGPS chart-plotter. Following a pleasant night at anchor we departed the bay mid-morning and retraced our track out to the small craft route. Our boat, “Summer Wine” is a recently built (Wiggers at Port Darlington) Nonsuch 33 sailboat weighing over nine tons. It has a cast lead fin keel drawing five feet four inches (1.6 m). Throughout the experience described below we were motoring under a thin overcast sky and the light breeze from the north suggested that we would be motoring through the day to our next destination. From the intersection of the marked small craft route south of Fryingpan Island, Chart 2202C indicates a direct route to the open water of Georgian Bay. The chart does not show the several bouys placed along this route, however there were several visible spar bouys leading south-west and then west. I followed the indicated passage for about mile to a location several hundred metres short of the last red bouy which I presume indicated Harris Bank. From that location, both the chart-plotter display and Chart2202C indicated a safe passage to the south between a few shoals, but with an indicated least depth of more than six metres of water. Following the indicated deeper water path displayed on the chart-plotter we preceded in a southerly direction, noting along the way several significant underwater features that were not indicated on the charts being referenced. The sun shining through a thin overcast onto the rippled surface of the water gave the surface a metallic sheen, effectively obscuring sub-surface features from our view. After a few minutes motoring, and passing beyond the bottom of Chart 2202C, the sonar showed the bottom ahead to be falling away in agreement with the chart-plotter display. Given all indications that we were now entering the area of the deep waters of the open Georgian Bay, I engaged the autopilot on a southerly course and set about establishing a destination way-point on the chart plotter, a task requiring but a couple of minutes of attention focused on the chart-plotter. BANG - a dynamite explosion-like noise shattered the quiet of the morning. The boat seemed to buck vertically and then bang again against an unseen underwater obstruction. I immediately put the engine into neutral and made a quick check for apparent damage. Discovering nothing serious, I carefully backed the boat slowly away from the impact location. I could then see through the reflected glare of the water surface the barely-visible steep faces of a brownish-coloured underwater promontory. I retreated back to deeper water and then by-passed the impact point. In short order depths of more than thirty metres under the keel were indicated on the FLS display. Fortunately, neither Jan nor I were injured. An initial inspection of the boat showed no evident above-deck damage and below-deck damage to be minimal – the galley stove had been knocked off of its gimbals, a fire extinguisher torn from a bulkhead and a door fitting had torn loose. There was no indication of water entry into the hull. We chose then to curtail our cruise and to return immediately of Thornbury, our home port. A subsequent below-surface inspection showed a very large gouge (more than three inches tall and nearly two inches deep) spread across the full width of the lower leading edge of the lead keel. Remote from this location, near the top of the mast, the sail-track had developed a buckle caused by the tall un-stayed mast whipping forward on impact and then rebounding to its normal configuration. It is my practice to set the chart-plotter to always record the boat’s track over the bottom. Hence, I was able to subsequently establish that the collision with the rock promontory occurred at 45o 07.256’ N, 80o 09.767’ N. The display showed the nearest shallow waters to be Waubuno Rock, some nine hundred feet to the north-west, a distance far greater than any error of the DGPS plot and Harris Bank to the north-east, a feature that I had passed earlier. Subsequent reference to Chart 2242, issued in 2005, showed the point of impact to be just beyond the 25 metre line with a nearby indicated depth of thirty-seven metres and no shallows in the immediate vicinity. Although, Chart 2202C and the chart-plotter display had indicated a clear passage along the route taken, had I also referred to Chart 2242 (which was then below under the settee), I would have continued to beyond the end of the buoyed passage before turning south. A significant error on my part was failure to activate the depth alarm upon leaving our home port. Since it triggers upon entry to Thornbury Harbour, I turn if off for local sailing. Henceforth as we head out toward less familiar waters, I will actuate the alarm as we depart. This device looks forward up to several hundred feet and would have alerted me to our approach to the hazard. Our experience underscores the need for boaters to exercise extreme caution when piloting along the outer fringes of the 30,000 Islands. Between Giants Tomb Island and the main entrance to Parry Sound, a distance of 28 nm, Chart 2242 indicates only two marked small craft passages from the open bay to the small craft route. Other possible passages can be seen on the charts, however, as our above-described experience indicates, they should be used with extreme caution and reference to local knowledge. The various charts covering the outer fringes of the 30,000 Islands do not always agree, one with the others, and evidently not all hazards are indicated. Ian Thompson |