If you’ve ever been to sea in a small powerboat, you understand how variable the weather and sea state can be. A well-found vessel can take a great deal of punishment, but generally the crew prefers to avoid such conditions. Consider how many more wives and friends would go cruising if the ride were easier, how many fewer accidents would occur from over-tired crewmembers, or how many fewer divorces would result from unpleasant voyaging.

Aboard our cruiser, Dreamworld, we’re not immune to the vagaries of the elements and throughout our travels have suffered accordingly. We decided to investigate, and possibly implement, a reasonably priced solution to the problem of stability.

While in Puerto Rico several years ago, we saw a powerboat with wire-rigged vertical arms attached. Speaking to the owner, he explained that these were “flopperstoppers,” an outrigger-type stabilizer fitted to minimize rolling.

For our benefit, the owner deployed them to their horizontal working positions and explained the theory of their application. With a long arm extended from each side of the vessel and supported from cables by a solidly mounted structure amidships, it was possible to deeply trail below the water line a delta wing-shape device (called a vane or “fish”) that would exert a counter reaction when pulled upward against the roll of the vessel. We were assured that the system worked, but with several unresolved disadvantages, which we were soon to learn about.

The forthcoming Central American leg of our continued circumnavigation promised more of the same rolling we had already experienced, so we decided to research the practicalities of installing a similar system that would exclude the alleged problems of the flopperstoppers.

RESEARCH

A visit to the public library discovered the classic, Voyaging Under Power, by Capt. Robert Beebe. Within these pages we found an early description of the original concept. With no professionally manufactured systems available, we decided to design and build a modern version, tailored to fit Dreamworld, our 40-foot wood ocean motorboat. We planned to install the stabilizer system during our next scheduled haul-out.

The inherent problems identified in the majority of installations are as follows:

  • Difficulty in handling the stabilizer arms in all conditions;
  • Retrieving the heavy fish without damaging the hull, especially in emergencies;
  • Operating noise while under way
  • Losing the equipment if a failure occurred in adverse conditions.

After studying several boats and noting their specifications, we decided that the key to a successful system had much to do with attention to detail in the design and manufacture of the components. Drawings and calculations were done over a period of days with my son, Simon, and we found local suppliers for the materials we thought we’d need.

To offset the costs of such a system, we had to figure in the 25-foot stayed mast, already fitted on the afterdeck of Dreamworld, as a means of supporting the outrigger arms when deployed. This would entail removing and modifying the masthead, as well as adding more fittings to handle the stresses, while retaining the original backstay and forestay attachments.

Finding no hard and fast rules relating to the length of the arms, and comparing our mast to the height of other installations, we deduced that we could minimize stress by fitting shorter arms with our tall mast (versus long arms supported by a short mast). We visited the local aluminum supplier with a list of materials and measurements in hand. The shop agreed to cut the tubes.

THE BUILD

For optimum performance the arms must be mounted approximately 28 percent of the boat’s length forward of the transom; efficiency is reduced when the arms are located farther forward. The outboard ends also require wire stays rigged fore and aft to prevent lateral movement and hinge fractures when the arms are deployed during forward or reverse maneuvering.

After we determined the hinge location at the rise of the after cabin, we used string to mark the spacing and length of these fore-and-aft stays. I took care to keep the bow and stern stay attachment points slightly higher than the hinge’s horizontal plane to avoid any possibility of geometric locking when we raised the arms from a deployed position.

We knew that when the system would be in use, loading forces on each arm could easily exceed 1.5 tons, so it was imperative that each arm attachment plate be designed to handle and distribute this load.

Within carefully cut slots, we inserted flat alloy plates (measuring ¾ by 6 by 8 inches) into each end of the 3-inch-diameter, ¼-inch-thick-walled tubes. The outboard plates were drilled with ½-inch holes for attachment to shackles for the fore-and-aft wires prior to welding onto the tube ends. The inboard plates were similarly machined to fit mating hinges attached to the hull before being welded to the inboard end of the tubes.

The final step was to weld beefy pad eyes to the middle of each arm, in a centerline position, at both the top and bottom radius of the tube. These pad eyes would be used for uphaul and downhaul systems. Upon completion of each arm, the welds were crack tested, cleaned, and primed before we applied several coats of white epoxy paint.

We fit the arms to the hull and were happy to see that both lined up vertically, as designed, in their new stowage cradles. We temporarily deployed the arms to a position calculated to be 7 feet above the water level, so we could accurately measure the length of all necessary cables.

READY-MADE VANES

During our research we learned that it was most cost-effective to purchase ready-made vanes from a specialist company in Seattle, Washington. Kolstrand Marine Supply services the commercial fishing industry, where the vanes are mostly used by workboats handling large fishing nets.

For our size boat, they recommended the medium-weight vanes, which weigh 28 lb. each. We bought two, as well as the appropriate storage brackets for mounting to a railing. Aware of the strain imposed on the rigging by the deployed vanes under way, we bought sufficient quantities of 1/4-inch 7-by-19 stainless steel wire with a breaking strength of 6,200 lb.

When rigging the wire, we used stainless steel thimbles and sleeve swages at all shackle points and swaged rigging screws for tensioning on the inboard ends of the cables. High-quality shackles, closely fitting the holes on the pole plates, were installed, and cables were tightened with turnbuckles. To assemble the uphaul and downhaul for each arm, we made up block-and-tackle rigs of 3/8-inch yacht braid nylon and double blocks.

Typically, the uphauls are fitted to the outer ends of each pole but to achieve a more compact system, we chose to install them at the midpoint of each arm. That way, they add to the central support of the arms when the vanes are deployed. Small winches on either side of the flybridge are used for retrieving the vanes in heavy weather.

PROOF OF CONCEPT

With a block at the outboard end of each arm, we have a way to retrieve or adjust a vane even when under way. This has proven invaluable at times of negotiating shallow reef entrances during heavy weather. Simultaneously raising the arm and tripping the vane provides total control and avoids hull damage on final retrieval. Problems 1 and 2 solved!

The fish normally fly at 16 feet below the surface. To act as a shock absorber, we inserted a 5-foot-long piece of nylon line at the top, and a safety wire in case the nylon line breaks. Problem 3 solved!

With all shackles properly fitted, greased and secured via Locktite and safety wire, we tested the system on Dreamworld. Stationary and rolling heavily in 6- to 8-foot beam seas off Miami, we lowered the vanes in clear water.

Driving through the trough produced instant and amazing results. We watched as the portside vane rode forward from its trailing position and the arm pulled down when the sea rolled beneath us. As the wave passed we were prevented from rolling the opposite way by the similar but opposing operation of the starboard vane.

Within perhaps 10 to 15 degrees, we were level. And, perhaps best of all, our close-tolerance engineering paid off. My wife, Linda, our most sensitive crewmember, remarked at the absence of sound as the stabilizers performed. Problem 4 solved!

We have continually used our flopperstopper system for 2,500 nm, much of the time in 20-foot seas, during our adventure in Central America. When recently checked in Panama, we found zero wear throughout the system, and when greased on a regular basis, we expect it to last almost indefinitely.

Stabilizers have changed our lives aboard Dreamworld, and in conditions recently experienced, possibly saved our lives. Never again will we sail without them.

Nothing is free, but we feel that the penalty of ½ -knot speed reduction, together with the $3,500 outlay for materials and welding, is justified in return for guaranteed comfort and safety for the foreseeable future.