Reduce Boat Roll with Flopper-Stoppers
Seamanship: When the ocean in motion becomes untenable, try flopper-stoppers or paravanes to settle things down.
Lying at anchor in warm and gentle trade winds under a blue sky, Mark and Sandi are enjoying a late afternoon sundowner in an idyllic Caribbean cove. But as Mark fires up the grill, he notices breaking swells over distant offshore reefs.
Their 42-foot cutter is usually very steady, but before long, the boat begins to roll. At first the motion is quite gentle and only mildly annoying, but before long, it increases enough that Mark’s sundowner ends up on the cockpit sole and dinner loses its appeal. Although they’re positioned head to wind, a north swell generated from a weather system hundreds of miles away is wrapping around the small adjacent island and striking them abeam. They decide to deploy their flopper-stoppers to reduce the roll.
At the suggestion of an experienced cruising friend, the couple had installed twin whisker poles that easily stow upright against the mast or on the deck. Although primarily used for poling out the headsails when sailing downwind, they can also be rigged for use with the flopper-stoppers. It’s important to note that Mark and Sandi substantially upgraded the topping-lift lines, the turning blocks on the mast, and the hardware that connects the poles to the spar, which now are all much stronger than those required strictly for sailing. In sudden, severe rolls—such as those created by the wake of a large powerboat—the loads imposed by the stabilizers are immense.
|How to Deploy a Flopper-Stopper
1. The floppers work together: As one resists the upward motion, the other sinks lower, and the motion of the boat is noticeably and comfortably dampened. 2. The length of the poles is critical and will vary from boat to boat. It’s imperative to have a full understanding of the loads involved. Unlike conventional spinnaker poles, the topping lifts should be secured at the outboard ends of the whisker poles and stabilized by a pair of fore-and-aft guys and by the line that directly secures the flopper-stopper.
Using the topping lifts that are secured to the ends of the whisker poles (not to the centers of the poles, as with many spinnaker poles), Sandi lowers the poles until they make 90-degree angles with the mast and secures their fore-and-after guy lines to lock the poles perpendicular to the boat’s centerline. Mark retrieves the flopper-stoppers from a cockpit locker and checks that the lines that run from each corner of the device to the connecting ring aren’t tangled.
He secures the first stopper to a line attached to the end of a whisker pole, then ties a retrieval line to a corner of the unit. Next, he lowers the stopper over the side, maintaining a small amount of tension on the retrieval line as the stopper swings out beneath the end of the pole and sinks to a depth of 12 feet. The retrieval line is then secured to a deck cleat with just enough tension to keep the flopper from twisting.
As the first flopper-stopper begins working, the harmonics of the roll are disrupted and the motion is noticeably dampened. After the second unit is deployed, the roll nearly disappears. The baffles work in harmony; as one unit resists the upward motion, the other sinks lower. Mark and Sandi relax and enjoy their dinner, then have a restful night on their gently moving boat.
Floppers vs. Paravanes
The types of stabilizers used when a boat is stationary, as in the preceding example, are very different than those used when a boat is under way. Both are often called flopper-stoppers, but this term is misleading. True flopper-stoppers are designed for use only when a boat is at anchor or, perhaps, drifting. Stabilizers used to ease the motion on an underway boat are properly called paravanes; sometimes these are nicknamed “fish” or “birds.”
Real flopper-stoppers come in a variety of types; while many are homemade, all work on the same principle. They’re designed to sink rapidly, with little resistance, to a depth determined by the connecting line, then resist rapid upward motion, such as that imposed by a wave. Some designs achieve this by shape alone, but most units have baffles that open during descent and close to resist upward motion, or utilize a hinge that allows the unit to drop in a closed position and open when rising.