Warp Speed Ahead
17 November 2020
Alexi and I started cruising on a monohull. We really enjoyed that but eventually decided we preferred a catamaran (two-hulled boat). There were many things that we needed to get used to when we switched. Most catamarans are much wider (beamier) than monohulls. That means they need more room to maneuver near a dock. But, they often have two engines that are spaced very far apart, making them nimbler in close quarters.
We also quickly learned that the approach we used for selecting dock lines for the monohull was not going to work for our catamaran.
Monohull cruisers often carry dock lines that are one-half to two-thirds the length of their boat. That makes a lot of sense. A monohull approaching a marina for the night is typically assigned a slip that is about fifteen wide. A 20-foot dock line is all they need. And, that's about one-half to two-thirds the length of a typical 30- to 40-foot monohull.
But, we are never given a 15-foot slip when we approach. In fact, we rarely get a slip at all. In most cases, we are on a T-head, side tied. For a side tie, you need at least four lines. Bow and stern lines cross the boat from the hull farthest from the dock (they are shown in red to the far right and far left of the picture). Forward and after spring lines run parallel to the boat and keep the boat from moving back and forth along the dock. For most catamarans, the spring lines are deployed from midship cleats on the hull nearest to the dock. But, they can also be used from the bow and stern.
This arrangement can tolerate changes in current and tide. And, with fenders in place, the stern line can be tightened to bring the swim platform up against the dock.
Most catamarans are about twice as long as they are wide. So, a forty-foot long catamaran is about 20-feet wide. Now, that same 20 foot line that worked so well for the monohull won't even reach the dock from the far hull! It is worthless. Even a thirty-foot line may not be enough if the cleat is far forward.
At first, this problem seems to have a simple solution. Use longer lines. For example, we use spring lines that are about the width of the boat (25 feet) and bow and stern lines that are about the length of the boat (35 feet). That's 50-100% longer than recommended but works really well in nearly every situation. We've been using these line lengths for years in our home slips and as we cruise. But, there is a problem.
Lines that are long enough to dock and thick enough to secure a large catamaran with a lot of windage are cumbersome and heavy to pass and toss during the hectic moments approaching a new dock in a new city with a tricky wind or current. A wet, 35-foot, ¾" nylon dock line can weight 30 or 40 pounds!
So solve this problem, we use warps. In other words, we have two sets of lines: maneuvering lines (warps) for getting into position and dock lines for holding us there.
The way it works is this. We go for a forward (bow) spring warp first (green line to right). That means that the mate is standing on the bow with a relatively short (about 20-foot), lightweight (about 3/8") line cleated to our bow (the warp). As we approach the dock upwind or current, she decides if she is going to toss the warp, hand it to someone, or add a bowline and hook a cleat or pole. Once the warp is made fast on the dock, I can use the engines, current or wind to bring the boat alongside the dock. Occasionally, we prefer to back up to the dock, in which case we do the same procedure with the mate on the stern holding an after (stern) spring warp (green line to the left).
If we are going to stay for a just a few minutes (a fuel dock), we leave the warps in place. Otherwise, once we are alongside, we will set our thick (and much longer than recommended) dock lines.
Perhaps it is clumsy to carry two sets: dock lines and warps. But, the ability to use short, light lines to quickly adapt to a pole, a cleat -- or a person on shore who does not really know the difference - is worth a few extra feet of line. And bonus: we look super-salty with lots of lines hanging around the boat!