Oct 26, 2004--TWIN KEELS (Bad and Good)

We used to say that MAGIC DRAGON was a series of experiments joined together by fiberglass.

When we designed her, we tried to find ways to build a roomy cruising boat as practical and as comfortable as we could within certain criteria. One limit was length, because in the West Vancouver Yacht Club berths over 40' were not available. The other limit was our budget.

So we came up with a 40-footer with a 14-foot beam and freeboard to accommodate 6'3" headroom under a flush deck. The broad beam gives her form stability. The high freeboard makes for higher ultimate stability. Both provide much interior roominess. The only other boat during the Sixties with similar beam-to-length ratio was the Cal 20, which appeared while we were a-building. It was reassuring to see half-size models in action.

The design was a total departure from the racing cruising yachts of the 1960s, and I was worried that such a volume with light displacement might develop a wild jerky motion. I imagined that two keels would dampen the roll. Such a yacht could not pivot around the lateral plane of its keel. To roll around one keel, the other keel has to be displaced sideways. Also I thought that two fabricated steel keels bolted on the outside of the hull into laminated frames would be a simple way to build a very strong structure and provide extra fuel tankage.

Of course I realized that, to be effective, the keels had to be big enough to dampen motion as well as to minimize leeway. Only one keel works efficiently when sailing on the wind. Big twin keels means increased wetted area, not what one would choose if designing a racing yacht.

However, we knew we were not designing a racing yacht. We had seen the cost of competitive racing and we knew that a 40' racer was out of our budget and, for that matter, not our taste either.

Maximum sailing efficiency in light going requires expensive gear and sails. Motoring in calm waters, on the other hand, is quite economical. So we decided to go for efficient working sails to power us in a breeze, and we built in ample fuel tank capacity to motor in light winds or calms.

As with most experimental Mark 1 prototypes, not everything was right the first time. For instance, the keels were first built with an asymmetrical shape, the idea being that the leeward 'working' fin would provide sufficient lift without crabbing to keep the hull moving along her centerline. The weather keel was supposed to oppose heeling. But the asymmetrical keels--flat on the outside, airfoil on the inner side--acted as brakes. It was confusing at first because when pressed hard on the wind or close reaching, MAGIC DRAGON performed well. But off the wind, or sailing in light conditions, or when powering, their action could be likened to snow plowing on skis, the object of which is to slow down or come to a stop. The twin phosphorescent trails of the wake indicated the turbulence created by the unfortunate design error.

After two years of putting up with them, it was in Guaymas in Mexico that we had them removed and replaced with identical but symmetrical keels, using the same hull flanges. The keels, which a moonlighting Vancouver policeman took three weekends to fashion, took the Mexican shipyard six weeks, seven men and many near disasters to complete whereon hangs many a tale. Suffice it to say, the dragon eventually took to the water with a much more easily driven hull. Sailing in light winds, the switch to symmetrical keels made a phenomenal difference. Powering on smooth water at 1800 rpm on a gallon of fuel an hour, the speed increased from 4 1/2 to over 6 knots. (We still had the original 35hp Isuzu in those days.) At night the phosphorescent turbulence had disappeared.

MAGIC DRAGON's keels are 8 feet apart, 4 feet deep, 8 feet long. At 15-degree heel, the lee keel is vertical in the water, therefore quite efficient. Each keel contains 1500 pounds of lead ballast and 75 gallons of fuel. With 1/4" side plates welded into a 1 1/2" leading edge steel rod and 1/2" base plate, they are solid feelers when grounding and good supports when hauling out.

The twin fins were intended primarily as motion dampeners. In this they may have been successful. MAGIC DRAGON has mild manners. Part of this may be due to her light ballast-to-displacement ratio as well. But for whatever reasons, we have appreciated the fact that she has no tendency to develop a rhythmic roll underway or at anchor. Sailing straight downwind even in big seas, she slides away very steadily. At anchor she can be active, her form stability sensing the water unevenness. But her motion at rest and underway has no jerky recovery and is very easy to take. People and objects don't get thrown around.

Our twin keels are a mixed blessing. They provide an easy ride. They are great to beach the boat for tidal haul-outs almost anywhere where the tidal range is adequate and the bottom is flat and hard. Just the other day we were able to check propeller zincs and clean the prop without diving in cold opaque water. But in light air the extra wetted area is a drag, and a foul bottom is that much more of a handicap. As for the extra antifouling and the time to apply it and the awkwardness of rolling it on over our heads between the two keels, many times we have cursed them as we became spattered with bottom paint. By the end of a haul-out we look like victims of some ghastly plague.

The accepted idea that twin keels are an advantage in case of accidental grounding is not always true. If one of the keels grounds on a falling tide it is much more difficult to hold her standing upright till the next tide than would be a single keeler which can be held upright with an anchor from the mast head. Twice now we have returned to find MAGIC DRAGON with her mast close to horizontal, when in each case one keel had become stuck in a mud bank on an ebbing tide. In Mbenga, Fiji, we ran her aground on coral in murky water after heavy rains with just one keel stuck fast. We had to dive to stack up coral rocks in order to construct a platform beneath the second keel. More important, a twin keeler fast aground cannot be heeled to minimize draft in order to be dragged off by the masthead, as can a single keeler. She'd have to be flopped right over on her side, which could be awkward, to say the least.

However, for all the possible inconveniences that twin keels may cause, the benefits have been an asset. The gentle motion when sailing downwind is not to be underestimated. Another advantage: with a central through-deck lift point attached to keel bolts, we have been able to lift MAGIC DRAGON with a local truck crane and rest her on her keels ashore in places like St.Thomas, Tahiti and Saipan, where hauling facilities were very expensive or non-existent. Lastly, the twin fin keels have made our cruising more fun in that we often choose to anchor in shallow calm water knowing that should we go aground with the tide, it doesn't matter much.

Extra wetted area or not, MAGIC DRAGON has proven her windward capability, making many surprisingly good long passages into the Trades, as well as bashing to weather on many other contrary windy crossings.