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|12-19-2003 03:33 AM
Yawl vs Sloop
I think that Jack hit the main points on the yawl rig. I would say that if I were thinking of going engineless, the yawl rig would be the absolute last rig that I would be looking at. If I were planning to go engineless I would think that you would want a fractional rigged sloop with a standing sail plan that is large enough that you can get by with minimally or non-overlapping headsails.
Boats are systems and when it comes to one size fits all answers, there is no single right answer when it comes to yawls.
I lump yawls and ketches together here because the share many similar characteristics. Ketches, in one form or another, have been around for a very long time. In the days before winches, light weight- low stretch sail cloth, high strength- low stretch line, and low friction blocks, breaking a rig into a lot of smaller sails made sense. It made it easier to manhandle the sails and make adjustments. Stretch was minimized by the small sails so the sails powered up less in a gust and although multiple small sails are less efficient, the hulls were so inefficient that the loss of sail efficiency did not hurt much. Multiple masts, along with bowsprits and boomkins, allowed boats to have more sail area that would be spread out closer to the water. In a time of stone internal ballasting this was important as it maximized the amount of drive while minimizing heeling. But multiple masts also meant more weight and much more drag. There are also issues of down draft interference, meaning that one sail is operating in the disturbed and turbulent air of the sails in front of it, which also greatly reduces the efficiency of any multi mast rigs.
Yawls soley came into being as race rule beaters. They are first seen in the 1920''s as a rule beater under the Universal and International rules. They continued to be popular under the CCA rule as well. Under these rules, the sail area of jibs and mizzens were pretty much ignored in the rating. This popularized both the masthead rig and the yawl.
There was a basis for not measuring the sail area of a yawl under these rules. On a yawl going to windward, the mizzenmast and sail actually produce more drag than they do drive. This is because the mizzen is sailing in really turbulent air and has to be over trimmed to keep from luffing which can effectively act as an airbrake. This is slightly less of the case on a ketch where the size of the mizzen is large enough to provide a larger percentage of the drive.
Downwind mizzens also are a problem. In this case they are forcing the main or foresail to operate in their bad air and so again they are not adding as much to the speed of the boat as they are taking away. BUT in the predominantly reaching races that were typical of offshore races of that era they offered a number of advantages. First of all on a reach the sails are not acting in the slipstream of each other and so each contributes a fair amount of drive for the drag produced. Also with the advent of lightweight low stretch sail cloths, mizzen staysails, which are great reaching sails, came into widespread usage in racing. Here again a ketch has the advantage of having a taller mizzen and so can fly a bigger mizzen staysail.
In comparing yawl rigs to sloops. The broad generalities are that for a given sail area a sloop rig will generate a greater drive for the amount of drag generated pretty much on all points of sail. That means that a sloop will be faster or will require less sail area to go the same speed. Sloops are particularly better than Multi spar rigs such as Yawls and Ketches on a beat, deep reach, or on a run. A sloop rig would tend to be taller for a given sail area. This means it would be better in lighter air but it potentially might heel more or need to be reefed sooner as the breeze picks up.
Sloops work best on boats with reasonably modern underbodies. Both are more efficient and so can point higher, sail better at the light and heavy ends of the wind speed range, and make less leeway. If you are talking about an engineless boat, the ability to point or run becomes especially important.
Ketch and Yawl rigs work best with heavier boats with less efficient underbodies such as full keels and Vee''d hull forms. These hull forms often need a lot more drive and the hull is the limiting factor in how fast or how close winded the boat will be. The yawl or ketch rig''s lack of windward ability is less of a liability when placed on a hull that similarly lacks windward ability. Also, the ability of a ketch or yawl to carry more sail while producing less heeling moment, also makes it a natural for a heavier hull form which often has comparatively little stability when compared to the amount of drive required to make a heavy boat move.
Much is made of the ketch or yawl''s ability to be balanced to help with self-steering and also the ability to sail under Jib and mizzen in a blow. This is one aspect that a traditional ketch or yawl has over a traditional sloop. It is not so true of modern sloops. Modern (especially fractional) sloops can be easily depowered and that reduces the need to reef. With modern slab reefing gear, reefing is far more easily accomplished than dropping the mainsail to the deck on a yawl or ketch. In a properly designed sloop balance is just not all that hard to achieve.
The performance of all three rigs, both on broad reaches and in lighter air, can be improved by the ability to carry kites of different types.
In terms of comfort at sea, ketch and yawl rigs, but especially yawls push the weight of the spars closer to the ends of the boat which can increase pitch angles, albeit, while perhaps slowing pitching rates. The taller rigs of a sloop tend to increase roll angles while slowing roll rates.
Then there are structural issues. It is often difficult to properly stay a ketch or yawl rig but especially yawls, as the mainmast backstay often need to be routed around the mizzen and the forward load component of the mizzen if often taken by the top of the mainmast. It is also often difficult to get proper aft staying on the mizzen of a ketch or yawl as well. These structural issues are particularly pronounced on Yawls where the mast is so far aft in the boat that on a traditional boat it is hard to get adequate staying base widths.
Many of the early fiberglass yawls were very poorly engineered. I heard the story of how the Bristol 40 became a yawl. It seems that Clint Pearson (who owned Bristol) had started to build a Bristol 40 sloop on order for a particular customer. As the boat was nearing completion the prospective owner bailed out leaving Mr. Pearson with bit of a problem. Almost at the same time came an enquiry about the availability of a Bristol 40 yawl for prompt delivery for a different person. Without hesitation the potential buyer was told that they happened to have a yawl that was almost finished and would be available in a few weeks. At the time Bristol was building a 24 foot Corsair and they took a mast and rigging from a Corsair and used that for the mizzen. A block of wood was glassed onto the hull for a mast step and a hole cut in the deck for the mast to go through and Voila- the Bristol 40 yawl. Several more were built like that and they quickly proved problematic. Eventually the design was engineered to solve the problems that occurred on the first few yawls.
Anyway, in conclusion, if you are interested in sailing performance or ease of handling, a sloop rig makes more sense. To me the only justification for the yawl rig today is solely romantic charm or a sense of history. I do not mean this to be a put down to those who love historic rigs, but for sheer sailing ability a yawl is a relic of another time and an ill-advised and obsolete racing rule.
Responding to your perceived advantages of a yawl, the high drag of the mizzen and comparatively small area of a mizzen means there is no "ability to ghost along under a small headsail and jigger". Going jib and jigger requires a whole lot of wind on a yawl. I cannot imagine why you would want an "air brake" but the mizzen with its small sail area is a poor choice for that as well. While it is true that the mizzen does add a little extra area, it does so at the expense of reducing mainsail area and often jib area as well which in addition to being without the mizzen for balance you are likely to have lee helm on a yawl, means that you are less likely to sail a yawl "like a sloop".
|12-18-2003 10:16 PM
Yawl vs Sloop
Perhaps a better question is ''are there sufficient advantages in favor of a yawl?'' since you are limiting your choices severely if preferring a yawl rig. Downsides of a yawl rig would include:
-weight in the end of the boat (spars, running/standing rigging, sail, and no doubt ''stuff'' on the mast)
-limited use of the mizzen over the range of wind speed & direction
-shortened mainsail foot
-increased weather helm when you can use the sail
-limited sail area
-the geometry of the cockpit can be altered negatively as there''s more in the way back there
Yawls as I understand it were generated in recreational sailboats from rating rules. Yes, I know Donald Street loves such a rig and also sails engineless. Many of his views are passe'' now as technology, changes in cruising grounds and the choices available on the used boat market have all changed dramatically since he''s productive writing years in the 70''s. I can''t imagine putting the expense of a yawl rig on a boat while concurrently removing the utility of an engine, presuming that the money could help keep the engine reliable (rebuild? replacment? repairs?).
|12-18-2003 08:03 PM
Yawl vs Sloop
Having been on a few, I know the disadvantages (as well as the obvious advantages) of a Ketch rig. They''re cool, but not for me.
I was wondering about yawls though. As I''m thinking of going engineless soon, the ability to ghost along under a small headsail and jigger, "air brake", and have some extra sail area to toss up or down depending on conditions could be handy, and when it''s not in use, I could still basicly sail her like a sloop.
So, other than the added rigging... What are the disadvantages?
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