A foiling moth is one of the most spectacular and demanding single-handed racing machines in the world. It's also catastrophically fragile in urban water conditions. A Manhattan circumnavigation in a moth is the sailing equivalent of running a high-speed motorcycle through Times Square during rush hour.
The moth's hydrofoils lift the hull clear of the water, reducing drag and allowing speeds over 30 knots in moderate wind. But this speed and the foiling flight envelope create unique hazards on an island where large commercial vessels, tugboats, ferries, and sightseeing boats dominate the waterways.
Ferry and tugboat wakes are lethal. A large wake passing underneath a foiling moth can pitch the boat violently, disrupting the foil's smooth flow over water and causing an immediate, uncontrolled capsize. The East River ferry runs regularly; tugboats move barges continuously; sightseeing boats generate significant wakes. There's no way to avoid all of them on a circumnavigation. You'll encounter major wakes dozens of times. One bad hit means swimming and losing time.
Hell Gate at 5 knots of current is survival mode for a moth. The current velocity isn't the primary problem—it's the breaking waves and chaotic water patterns created when tidal flow interacts with the irregular bathymetry and narrow passage. A foiling moth needs smooth water to stay on the foil. Hell Gate is anything but smooth. You may drop off foil several times and slog through as a conventional boat.
Bridge clearances are not an issue for a moth. The mast is only about 28 feet tall, well below any bridge. But the narrow confines of Spuyten Duyvil and sections of the Harlem River create wind-shadow zones where you lose apparent wind. You'll need to drop foil, level boat, and motor paddle or row.
The enemy is not the geography—it's the wakes. Ferry wakes plus current, tugboat wakes, sightseeing boat wakes. You cannot predict or fully avoid them. The moth is essentially a platform waiting to be knocked off its foils by the next passing vessel.