I once was motor-touring about 15MPH when I heard three blasts from a mid-sized inboard coming up fast behind me. Since I was about 200 feet from shore, and dismissed the three blasts (meaning "backing"), I eased towards a dock and slowed. Looking astern again, I saw that the "Grey Ghost" had nearly run up my back!
The three blasts were to alert the dockmaster that the mail was being delivered -- right to the very dock that I thought was going to save me from being run over!
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Originally Posted by ITD
Pass to the rear, although I'm sure this doesn't apply to you, most of the motor boaters out there think that sailboats are stationary and end up way too close when they try to pass to the front. Also because of wind variations sailboats speed up and slow down, especially on gusty days. Lastly if a sailboat is sailing toward the shore, give it a wide berth. The sailboat is probably tacking to head upwind and will soon be coming about, changing direction. Wakes generally aren't a problem because there is a large sail above the water and some sort of keel below the water that tend to stabilize things.
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ITD has it exactly right (here, anyway).
But when multihulls are added, things change. Cats and trimarans can go two- to three- times faster than other sailboats, and introduce other issues.
"Pitchpoling" is one. It's not seen in other sailboats.
Pitchpoling is most often the result of driving one or more hulls under a wave. The boat will come to a sudden stop -- and you don't want to be following even 150+ feet astern, or at any speed where you can't avoid the striking the "operator" and crew in the water. (Sailboats don't have "drivers"). High speed power catamarans (tunnel hulls) are increasingly encountering the same effect, often fatal, which they call "stuffing". I posted a video somewhere here of a power cat ripping along.
For multihulls, wakes are another matter:
Too often, wake-cycles can
nearly approximate the spacing (width/beam) of the hulls and violently toss the occupants back and forth between the hulls. Gear and rigging are thrown around too. When the wake-cycles are
exactly the same as the hulls' spacing, the occupants are forcefully thrown in an up-and-down motion -- not
quite as disrupting.
As ITD states, sails and keel keep sailboats balanced and stable, but only when there is sufficient wind.
Unlike
monohulls, multihulls are very lightweight. One Olympic-class catamaran, at 20-feet, weighs less than 372 pounds fully rigged. A small photo
of that Olympic-class catamaran with yellow sails is attached.
It's small, but you can still see the skipper with his arms extended. I'm thinking the boat is travelling from left to right, in a cartwheel. The big splash to the left is probably one crewmember. That light weight allows some spectacular speeds.
The photo to the right is a large multihull that has suddenly come to a stop --
mid-pitchpole. Although it may not have actually gone in - and over.
The stern is to the extreme left of the photo.