Companionway Formula

Kinney’s design for a safe and comfortable staircase
Companion is an old term for a doghouse or raised skylight on the upper deck, often featuring seats on its sides and opening windows. It’s also the term for the companion-way, a stairway leading from the deck or cockpit to the main saloon below.On small boats, of course, the stairway is unavoidably steep and more likely to resemble a ladder than a staircase, with steps about 12 inches apart. It’s a great luxury on a larger boat to be able to descend gently sloping companionway steps with an armful of sails or other gear.There’s a formula for such steps. They should be between 9 and 11 inches apart, and they must all be equally spaced. They can be as narrow as 15 inches, but 18 inches is better, and even more width will allow you to make an entrance into the saloon with great elegance.Here is Francis S. Kinney’s method of designing safe and comfortable steps, taken from Skene’s Elements of Yacht Design:

This arrangement plan for a voyaging sailboat shows the companionway stairs from pilothouse to saloon in profile and plan views.

• 1.Divide the vertical distance between the deck and cabin sole into equal spaces of between 9 and 11 inches each.

• 2.Lay out the horizontal distance by allowing a projection forward of 9 inches for the top step, and successive projections of 5 inches forward for each following step.

• 3.Let each step measure 6 inches from fore to aft, allowing an overlap of 1 inch.

For safety reasons, companionway stairs should never be varnished unless they are provided with nonskid strips on top of the varnish. Sometimes fancy stairs have individual arc-shaped steps that curve upward at the outboard ends. The theory is that you can find an upright landing for your feet no matter how much the boat is heeled over; but, frankly, most of us seem to manage quite nicely with normal steps.One final note about companionway steps: sitting on the top step is a favorite habit of guests and off-duty crew members. Make it illegal. Post notices forbidding it. Punish transgressors. It is very annoying to have to keep asking someone to move out of the way every time you want to go below or come on deck.

---