Keel vs. Kelp: Fight!
Southern California Coast, 2014, S/V Le Lezard
Kelp is an enemy best avoided when both sailboat racing and voyaging. Today we would treat kelp as our friend, we hoped. This voyage began at the culmination of another great United States Sail and Power Squadrons San Luis Rey raft up at the Del Mar Boat Basin, Oceanside, CA.
We sailed south from Oceanside to San Diego on P/C Barry Bean's fancy new sailboat, S/V Le Lezard, a Jeanneau Sun Odyssey 36.2. The sailing trip began at 08:00 under power and under clear skies. Swell was minimal. Wind picked up from the southwest joined by gentle swells from the west at approximately 09:30 and we sailed close hauled until approximately 16:00. Course deviation due to current was minimal according to the comparison of the GPS's velocity-made-good reading and the sailboat's knot meter reading.
An idea developed during our trip to test the keel of the Jeanneau against the massive reaches of kelp off of Pt. Loma, San Diego. Barry related that his previous sailboat, an O'Day 27, could sail through the kelp forests by slipping directly through the branches. This remarkable performance is related to the O'Day sailboat's light displacement, hull shape, keel shape, and rudder placement. As for the Jeanneau Sun Odyssey sailboat's results when faced with masses of kelp, he remarked: "It's a perfect day to try it."
When it comes to keels vs. kelp, shape and size are significant. The motion of the ocean is inconsequential if a keel is skinny with a big bulb on the end; the sailboat will snag kelp at any opportunity. My own sailboat, S/V Oasis, a Downeaster 32, has a full keel with an attached rudder, thus parts a forest of kelp handily. The O'Day 27 has a small draft fin keel of about 4', which has less drag than a full keel with the trade-off of directional stability, and a rudder on a skeg, which protects the both propeller and rudder. The Jeanneau also has a fin keel, albeit with longer draft of 6' 3", and a spade rudder, which offers no forward protection for the rudder with the trade-off of better steerage (refer to Royce's Sailing Illustrated, page 18).
It may be helpful to reference the sailboat profile figures here to see how various types of keel and rudder configurations affect passing through kelp. The topmost sailboat profile is a full keel sailboat with attached rudder, similar to my Downeaster. The next sailboat is a fin keel with rudder mounted behind a skeg. If passing through kelp, the skeg presumably protects the rudder and propeller from becoming entangled, by parting the kelp under forward motion. The third and fourth sailboats are fin keels of different performance shapes with spade rudder, the fourth being the racing type, skinnier and longer. Another type, not shown, is a longer fin keel with large weighted bulb, common on lighter displacement sailboats and racing sailboats, which easily causes kelp to tangle at the bulb. A Hunter sailboat, for example, has a keel with a bulb.
Nearing Pt. Loma under the Jeanneau's sail, we adjusted our heading to bear into the large kelp forest off the San Diego coast, with speed on a broad reach of approximately 6 knots. Our course plan attempted to cut the corner off of the kelp forest to proceed directly into San Diego Bay, rather than sailing around the outside of the kelp forest. As Barry observed, the kelp forests cut the ocean swells down to a slowly rolling calm, and with the calm of the water, the sound of breaking waves is also halted. The kelp for-est is a small island of tranquility in normally choppy waters, yet that tranquility may capture the unwise.
We proceeded and the sailboat's bow dipped into the outside edge of kelp. All seemed well, our speed maintained a steady 5 knots. Barry maintained course at the helm. Then the sailboat's keel began to divide the kelp forest and our speed slowed by half. Long strands of kelp surrounded us on all sides, parting slowly. Multiple thick strands, caught on the sailboat somewhere below, trailed at our stern. After approximately three boat lengths, our speed dipped to half a knot. Barry reported that he had lost all steerage. The kelp had caught us and began dragging us into its thicket. Our sails began to luff. Barry noted we might have to con-tinue wing-on-wing.
We cut the sheets loose and the sailboat began to gybe, bobbing in the slowly rolling swell. Our first action was to quickly bring the mainsheet in, to avoid a rapidly swinging boom under a gybe. Our heading changed to dead-downwind and we let the main sheet out after the gybe, allowing the sailboat to settle into its own course. We nominated one of the crew to act as a human preventer, holding the boom out to prevent another gybe. Barry noted that the sailboat didn't have a whisker pole, so he moved forward to act as a human whisker pole, holding the jib out for a wing-on-wing sail plan. With this adjustment we maintained a speed of slightly over half a knot while both parting the kelp forest and dragging long strands from underneath us.
The rolling swells changed our heading from a deep reach to dead-downwind and back, since with the boom preventer in place, the sailboat was unable to gybe again. Barry kept tight hold of the jib while it alternately luffed and filled and snapped back into luffing repeatedly. Within the kelp forest, the wind was calm, seas slowly rolling, and progress steady at between half a knot and one knot.
Eventually we emerged at the other side of the kelp forest and adjusted sails to a normal broad reach. We continued to sail beyond the point of Pt. Loma to gain a suitable turn, still training strands of kelp. Barry performed a quick anti-kelp sailboat maneuver of motoring backward, motoring forward, and motoring backward again. Then he used a boat pole to life off a few remaining strands of kelp caught at the rudder.
With this tale now told, who is the winner, the keel or the kelp? I believe the Jeanneau performed well, we did not get permanently entangled. Losing steerage, however, is not to be taken lightly. While progress was slowed, we headed out of the forest easily with favorable, light winds and later cleared the rudder and propeller without incident. It is a fun adventure to test a sailboat's performance under clear, sunny skies with favorable winds, especially while having good company as fellow crew.