I apologize in advance that this is quite long and I worte it for another purpose but it is a detailed discussion of double enders which starts with a bit of history.
When you look at really old double enders (Egyptian passenger barges, Viking ship, canoes, Skerry traders) you see some things in common. As a broad generality, for their era, these vessels all tended to be quite light and fast and intended to be propelled at pretty high speeds with comparatively little power. The traditional (up until the late 19th century) double ender actually had very fine ends and a burdensome mid-section. This shape was evolved for speed and seaworthiness in low powered (low stability), low volume vessels.
This fine-ended double ender was a great shape for rough sea conditions. In theory, when a boat is running before breaking waves its own wake can disturb the waves astern and cause them to break. These fine-ended double enders threw smaller wakes and so were less likely to cause waves too break on them from astern. If a wave did break, the wave did not collide with the flat surface of a transom. (That is also the same reason that the transoms on traditional boats had as much rake as they did.)
That all works well for light weight working craft with minimal sources of power. As these boats became more burdensome, they began to have a different set of problems. One of the key problems with the more heavily loaded fine ended double enders were that they did not have as much reserve buoyancy as transom sterned boats and waves might not break in their wake but they would get pooped (flooded from astern by overtaking wave).
The Roman and medieval cargo ships, which are well known to researchers, were all double enders below and above the waterline but light displacement they most certainly were not - the cogs, shuyts and fluyts of the Middle Ages and the Renaissance were capacious, slow, cargo carriers.
The reasons that these ships, and most European fishing boats until recently, be they Norwegian, Scottish, Danish, Dutch, Spanish, Maltese or Greek, are double enders are twofold; One is that this type of stern is easy, reliable, and nearly as cheap to build in wood.
Another reason for the early use of double ends is that these working vessels had/have to lie alongside each other in close proximity in artificial harbors. The double ender is less likely to suffer damage from boats alongside. In such circumstances you find double enders.
Elsewhere, like the Breton coast of France or the East Coast of England, where the sea conditions are just as bad, but there are natural harbors, estuaries, etc. you find transom sterns and counter sterns. The transom stern gives more buoyancy aft and is better suited to a high displacement hull, while being nearly equally cheap to build. The counter stern gives a drier after deck (important in sailing ships, which were conned from the poop) and more space for handling sails (and nets, on fishing boats)
It is at that point in the 1800's that Colin Archer comes along in the search for a way to make boats that would not cause waves to break but that would also have sufficient reserve buoyancy in the ends. When you study the lines of a Colin Archer design they were really amazing. These were not delicate boats by any stretch of the imagination. They were truly beefy. They had to be. They were rescue boats and pilot boats that had to be able to stand station in the worst the North Seas had to offer and still make a rendezvous. They needed to be able to sail in light air, and they had to be able to lie against a stranded ship and take the pounding while rescuing people and property. They earned a reputation for their seaworthiness and ability to withstand the worst nature had to offer.
Archer was a theorist and was looking for a way to design powerful boats with powerful rigs that would still remain balanced. Archer also had a tremendous ability to model the lines of these heavy boats so that they had a fairness of line and fineness of water line that is not readily apparent at first glance. They are deceptive boats in many ways. For all of their weight they were reasonably easily driven boats. They were capable of spreading really huge sail plans or being snugged down to a handkerchief
By all descriptions that I have ever read these were not easy boats to sail. These were not the “sailed by a man and a boy” fine ended double ender epitomized by boats like the Tancock Whalers popularized in the fisheries off of Nova Scotia. They took large crews and a lot of brute strength to sail and to some extent they also survived on the iron wills of their crew.
Then along comes Atkins, who takes the Colin Archer rescue boats and adapts them into yachts. Atkins like Archer is a master of the carefully modeled hull form and in many ways his “Ingrid” is the definitive example of a successful Colin Archer type yacht. Comparatively fine yet buoyant and burdensome, the 'Ingrid's are a masterful example of the art of yacht design with the emphasis on art. I keep hearing people refer to these boats as fast. They are fast for what they are, but in a relative sense, even in heavy going, they are not fast when compared to more modern designs.
They also reputedly have very comfortable motions in a seaway. I suspect that that is more a product of their round bottom, and wine glass sections more than their double ends. The 'Ingrid's and 'Eric's did wonders for instilling the idea that double ended yachts represent some kind of ideal for distance cruising. This notion of the ideal was further embedded by the ubiquitous Hanna Tahiti and Gulfweed Ketches.
By the late 1960’s double enders began to be viewed as relics of the past. Well-modeled double enders are not easy to mould in fiberglass since there was often some tumblehome in the stern making it hard to removed them from a single part mould.
It probably would have stayed like that if the character boat craze had not gotten started in the early 1970’s. At the time the whole character boat thing was hard to fathom. After decades, suddenly bowsprits and molded in plank seams were getting popular. (If you actually owned a wooden boat you went to great lengths to conceal the seams and make the topsides look “just like fiberglass” but suddenly fiberglass boats were being built showing 'seams'.)
Emerging in the early days of that period of looking backwards, the Westsail 32 came on the scene. The Westsail 32 is a fiberglass version of the Atkins ‘Eric’ altered to supply more room down below and be easier to mold in glass. The Westsail pretty quickly became an icon for the “serious Blue water cruising boat”. Derided as heavy, slow and wet, with many were bought by posers and wannabes, in reality the Westsails have proven to be enduring boats with an admirable cruising record.
What the Westsails and boats like them did was to bring a focus on the growing gap between “cruiser-racers” and purpose built offshore boats. It was about that time that a young Bob Perry happened on the scene. I have always believed that Bob’s goal in designing the Valiant 40 was to design a boat that bridged this gap. Seen today the Valiant 40 seems very solid and conservative but in its day the Valiant 40 was revolutionary. If you look at the sections and underbody waterlines of the Valiant, they were remarkably far more similar to the early Sparkman and Stephens designed IOR boats (like the Tartan 41) than to anything that Colin Archer designed. Obviously a bit more burdensome, the Valiant 40 dared to be a moderate displacement (for the time) boat with a fin keel/ spade rudder intended for serious offshore cruising.
I also suspect form articles that I have seen over the years that the trunk cabin and canoe stern were chosen not for some inherent obvious sailing or seakeeping advantage but as a clear statement that the Valiant 40 was and is intended as a serious offshore boat. If you look carefully at the stern of a Valiant 40 it in no ways really resembles the traditional canoe stern chosen for low wave making and low drag. This is a very powerful stern consistent with the Valiant's more modern lines and underbody.
Of course for every brilliant design idea there are a bunch of bone headed copies. Having drawn a few double enders in my day, I really think that they take more skill than any other hull form to get right. Poorly done they are awkward in appearance and offer few of the advantages with all of the disadvantages of a double ender. Perry got it right, (to my eye, perhaps more so on the 37 foot Esprit), but a lot of designers never did. Designers like Garden, Benford, and Crealock have designed many a fine double ender, but I think Bob Perry was there at the right time with a design that really understood the problem and looked good doing it.
So back to the original question, “What are the advantages and disadvantages of a double ender?”
If the stern is not carefully modeled and matched to the other properties of the design, there are not any inherent advantages to a double ender; none at all. Properly designed in the fine-ended model, they offer a lower resistance at slow speeds, less wave making and a cleaner wake less likely to cause waves to break astern. Properly modeled in canoe stern model, they offer a lot of reserve buoyancy in the ends with a minimum stern overhang for reduced hobby horsing. They also offer less corners for lines to foul on which was far more important in the days of Gaff Rigs with booms that over hung the transom.
The disadvantage is that a double enders tend top have quite a bit less room aft for their length than a transom stern boat. This means a more cramped cockpit (or aft cabin). In terms of sailing performance, with modern rigs and underbodies it is harder to get a canoe stern boat to work with modern underbodies which are designed to surf and sometimes plane. This means that they are not suitable to today’s lighter faster design principles. Its not an issue if your interest is in a heavier, more burdensome, long range cruiser but if your goal is coastal cruising or performance offshore cruising, where speed becomes more important than carrying a lot of ‘stuff’ in a short sailing length, then a canoe stern might not make sense. Canoe stern boats can be a bit more expensive to manufacture in glass as they often require special molds to handle the tumblehome in the stern.
From a sailing standpoint, most double endere give away some initial stability which translates to reduced sail carrying capability and with that, the need to reduce sail sooner. Unless long and narrow, they lack the 'bearing' to achieve decent reaching and motoring speeds without the stern squatting and greatly increasing drag and fuel consumption.
But also there are practical issues with a canoe stern. In a practical sense, the pinchjed ends make it harder to carry a dinghy in davits or install the type of solar arrays that are becoming increasingly popular. The loss of volume aft, makes it more difficult to carry the weight of a full sized dinghy when davits are installed. The reduction in useful deck area and interior volume result in boats which are small for their length, and are the equivillent of perhaps a 15-20% smaller boat in terms of useful space and sailing ability.
At this point in time, I view the most recent crop of double enders mostly as a fashion statement. Most of us, sail the boats that we bought because we like them. We like them for all kinds of reasons, not the least of which may simply be that we like the way they look. I think that today’s double enders often carry with them a variety of features that attract a certain kind of sailor (or someone who wants to be that type of sailor).
But in the end, to me, in prioitizing the criteria for choosing a long range cruising boat, the most serious consideration needs to be the practical and functional aspects of the boat in question. Aesthetics may play a role, but if the plan is to go offshore for long periods of time, that role needs be secondary. And so from that point of view, I would consider a double end a liability rather than an asset.
Respectfully
Jeff
