Last week several threads scrolled by in which the controversial "to DDW or not to DDW" issue came up. It didn't take long, of course, before someone incanted the magic words "DDW is slow" and most of the congregation dutifully harmonized. The world of sailing is chockfull of similar mantras; viz, "the best time to reef is when you first think about it", "a good coastal cruiser is not a bluewater boat", "you can't sail faster than hull speed", "the higher the csf (capsize screening factor) the lower the probability of capsizing", "paper charts are more reliable than electronic charts", "beating to windward is the least comfortable point of sail", “finkeelers don’t heave-to well", & s.o. & s.f. What these one-liners do have in common is that they are sometimes correct, often wrong and always misleading! Let’s focus on the DDW issue for now. Racers are obviously better informed about what makes boats go fast than daysailers and cruisers. Thus, they usually manage to put their stamp on DDW discussions by trotting out polar diagrams and other simplified performance indicators of sailing vessels operating under rarefied conditions of perfect trim, perfect ballast distribution and zero wave effects. Before discussing what polar diagrams do NOT tell us, let’s take a fresh look at the polars of the semi-displacement Catalina designs discussed in last week’s threads. The Catalina 30 polars in the attached image (highly similar to those of the Catalina 42) reveal that under the abovementioned ideal conditions a DDW course only produces lower VMGs to a DDW destination at true wind velocities less than 16 knot (i.e. ~10 knot apparent). In other words, under conditions of flat water, plus perfect trim and ballast semidisplacement designs such as these Catalinas might as well sail a DDW course to a DDW mark in anything stronger than light winds…. I did not search for Hunter, Beneteau or Jeanneau polars but would be VERY amazed to find substantially different results. So what to expect when running in big seas rather than in flat water? Sailing vessels taking large swells on the stern will generally try to “square off” (i.e. run DDW if waves and wind are aligned), in order to minimize yawing. Yawing vessels lose VMG through the zigzagging as well as through being pushed sideways part of the time. Vessels failing to square off will not only experience severe yawing but will also be heeled, usually producing strong weather helm because of the torque created by the lateral separation between the center of effort and the center of lateral resistance. In this case, the helmsperson (or autopilot or windvane) can only prevent a round-up by fast rudder action, in effect “applying the brakes” And what about the additional effects of imperfect trim, slightly baggy sails, overloaded lockers and bilges and poorly distributed ballast characterizing the vast majority of non-racing daysailers and cruising vessels? Again, in anything from a fresh breeze, and up, poorly trimmed vessels will tend to heel more, thus usually requiring a liberal dose of “rudder drag” to stay the course, Unless sailed DDW, of course. DDW is flat. Flat is fast. Ergo, …….(you figure it out). The unanswered question here is: if not slow in moderately strong winds, why is sailing DDW so unpopular?? On this particular board I see two reasons for that lack of popularity: (1) with B&R and/or fractional rigs it is nearly impossible to properly trim the main for DDW; and (2) in stronger winds DDW often becomes a bit scary. Whereas nearly every skipper loves to sail wing-on-wing from time to time, it takes lots of concentration, particularly in bigger waves. In fact, a single unexpectedly big or errant wave can easily precipitate an uncontrolled jibe. With regard to easy DDW sail plans: a decade or two ago so-called “double head rigs” were popular among cruisers, enabling the use of wing-on-wing genoas or yankees set on whiskerpoles, often with the main centered and reefed down to provide stability against rolling. On Rivendel II we have often used a variant of the double headrig in which we fly a poled-out genoa and staysail wing-on-wing (see link). We also center, reef down and flatten the main to reduce rolling (the last thing we want to do is to dip a whisker pole in the drink at -- or above -- hull speed). IMHO, there is no easier and safer downwind sailplan to fly on longer passages. Unfortunately, properly setting both poles with topping lifts and fore + after guys is quite a bit of work, especially if the wind shifts just far enough to have to switch the jibs and poles again. This makes the use of this set-up less attractive for short-handed daysailing. Fair winds and following seas, Flying Dutchman
