Every fall, East Coast cruisers get ready for their annual migration down the Intracoastal Waterway to points south. Inside barrier islands the passage is calm and often beautiful and serene. The ICW provides much-needed shelter from the stormy waters and winds found offshore. Winslow Homer’s The Gulf Stream is all the pictorial evidence anybody needs for just how nasty conditions can get “outside.”
But an ICW passage isn’t for every boat. There are constraints. Much of “The Ditch,” as it is often called, is shallow. It’s dredged and the nicest anchorages along the way are restricted to shoal-draft boats.
But even more constraining for larger cruising sailboats is the mast-height limitation imposed by the numerous fixed bridges spanning the waterway. Anything over 65’ of air draft won’t fit under. If you dig you through the planning guides, some fixed bridges like the 7 Mile Bridge at Moser Channel in Florida, the max height is just 63 feet. And remember that has to allow for all those top-of-mast gizmos like wind vanes, antennas, and lights.
This big Ditch is not really all that big after all.
That made us wonder: What would be the ultimate ICW Ditch Cruiser? You want a ship that’s stout enough to stand up to offshore passages, if you have to go into the open ocean. You never know. And you want all the amenities and style, as you will be living on her for weeks at a time. But the ship must feature a mast short enough to fit under all those bridges and shallow enough draft for those nice snug anchorages.
What would that all look like? Let’s crunch some numbers on the sailplan.
It can get a bit complex, but basically, the sail plan is defined by mast height times the base of the sails. For triangular sails and a single mast, normal proportions point to a max hull length of about 50 feet, with a sail base of about 45 feet. The maximum sail area is easy to figure out: It is half that 45 feet, times the 65 foot high mast, minus about 9 feet, that allows for the height of the boom off the waterline. No sail fits in there.
It all works out to about 1,260 square feet of sail that we can spread.
How much boat can that 1,260 square feet of sail power? The so-called Sail-Area-to-Displacement ratio tells us that. Essentially, it’s a non-dimensional descriptor of the horsepower rating of a sailboat and should fall between about 17 and 21 for the wholesome cruiser we want. Using a bunch of exponent math, that trust us you don’t want to know, a sail area-to-displacement ratio of 17 yields a boat that pushes aside about 41,000 pounds of water.
That’s a bit of a hefty displacement for a 50 feet sailor. But not a bad place to start.
Next, we have to apportion that displacement to the actual length of the hull on the water line. And to do that, we use Displacement/Length Ratio. That’s between 170 to 350 for a good cruiser. (If you want to see full formulas drop us a line. )
We worked out our hypothetical Ditch Cruiser to have a displacement-to-length ratio of 200. That’s a nice number. Light, but not too light. And appealing full 45 feet of waterline. We can have attractive short overhangs and a long, efficient waterplane. In that package, we can easily fit a two-cabin boat—nice for living aboard — but not too too roomy. As Ben Franklin said, guests and fish stink after three days.
We’d kick it old school design-wise. We would go with a raised salon to bring in the great views of the Great Dismal Swamp as it slides by. And we’d fit in an inside steering station since hey, it rains. We would start with a single spar, a sturdy look, and relatively short overhangs. The lovely Bristol-Channel Pilot Cutter hull would be our reference above the waterline. But we would (naturally!) make it sleeker and more modern below.
But we think she might need more sail power. So we could look to add more sail by dropping in a second mast, make a full schooner rig with bowsprit, and add some square-top sails to fill in the gaps between masts. One place to start is the traditional Chesapeake Bay Bugeye, a shop favorite around here. Again, some streamlining and modernizing, but keeping the classic essence. Such a boat would be beautiful and a reaching machine under sail.
We’d also tackle the draft question with a bit of engineering: The ICW is a no-brainer for a lifting keel, or keel-centerboard. The lifting keel is a better sailing performer; the keel-centerboard is less expensive and more traditional.
At last, we can stand back and consider our work: An ICW head turner with a split rig, serious sailing performance, true shoal draft, a sexy sheer and real punch in a seaway. Plus enough room and amenities tucked in to make her truly live-aboard for a long, comfortable cruise up and down The Ditch.
That’s a boat that makes us want to get out the pencils and start sketching.