When an east wind blows above 25 knots the swell passing north of the island does an interesting thing: It rotates gradually to the south and breaks on our western shore. Waves traveling hundreds of miles from east to west reach the shallows of the island and wrap around them, crashing on shore at an angle approximately 120 degrees off of where they began. It is a pretty amazing phenomenon–a bit counterintuitive, even–and one we wouldn’t have believed until witnessing it drub our boats on occasion. This stuff definitely wasn’t in the manual.
Wave scientists explains this with a concept called refraction. According to this principle as a swell passes the rounded edges of an island gravity, momentum and friction force the axis of the wave to rotate to keep a constant relationship with shoreline and each wave maintains a fixed angle to the changing water depth. Given the curvature of the northern tip of Rabbit Island you can find yourself standing on the shoreline in front of the main camp with the wind blowing your hair from east while waves crash over your feet from the northwest.
This is not ideal for our moorings which take sizable waves even when completely protected from the direct force of the prevailing wind. On nights when a good nor'easter blows we sleep with one eye open and take turns waking up at two hour intervals to shine headlamps on the water amidst the crashing waves and blowing wind. The chance of discovering a severed line, failed cleat, or a boat adrift has a way of inducing restlessness, let us tell you.
Over the last three years we’ve refined our mooring design, hardware and placement accordingly. After much hands-on experience we’ve come up with a solution utilizing thick ¾" line, iron anchorages, underwater buoys to float heavy galvanized chains, stainless thimbles at all intersections of line and metal, stainless washers and nuts, strong climbing knots, rotational swivels, stainless quick links, shock absorbing snubbers, locking carabiners and rope floats to keep the mooring line off of the abrasive bottom. The result is low impact, completely removable and easy to manage. It shows due respect for the forces of Lake Superior with minimal excess.
We’ve also found that when faced with a storm shifting the boats even a few boat lengths to the south down the shoreline can matter quite a bit. The above photo from August illustrates this idea well. Marlin’s sailboat in the distance was in the best position to handle the large refraction waves and wasn’t disturbed whatsoever. The Montauk 17 in the middle of the photo took a few large swells but rode them without much fuss. The smaller Whaler 13, on the far right, however, took an intermittent pounding when sets of waves broke over her bow and stressed her mooring line to near failure. Thankfully the little boat lived up to its design and was, indeed, unsinkable.
All of this practical hydrology has put us through an apprenticeship of sorts, and we’ve found the work interesting. Dealing with the waves and wind on the horizon is a constant variable on a remote island in Lake Superior. On the bright side, however, when heavy weather rolls in it is never without reward. When our moorings are pounded from the northeast and our boats are exposed to swell, one thing is also for certain–surf’s up! And there is also lots of time to think as we’re not going anywhere a while.