Ideal Vessel Size – Less is More

There is a lot of interest expressed in larger vessels in the 50’ (15m.) range, so we undertook some preliminary investigative design work to identify features we may be able to offer in a 50’ vessel that would be specifically applicable to our liveaboard customer base.

for cruising customers, however, we came to the conclusionThere can be little argument that the 50’ vessel has a strong position in the charter market, being able to offer separate accommodations with separate heads for four cruising couples. There are lots of hands, eyes and pocketbooks sharing in the duties attendant to such a craft. Its “fair weather fun” application can turn much serious impracticality in the arrangement of things into a genuine positive.

For cruising customers, however, we came to the conclusion that the compromises made on voyaging with these large vessels using a limited crew can be a definite liability to enjoyment, safety and piece of mind.

The 50′ developmental exercise was informative in that it identified a number of controlling factors that may not be immediately apparent at a boat show or on the dock.

1) Visibility from the helm

If you actually keep the desired bridge deck and headroom clearances in mind, you are led to some accommodation configurations and a deckhouse envelope that has some serious interference with the line of sight from any practical enclosed steering position.

For the sake of this exercise, we took the altitudes from our current 44’ design, with some upward adjustment to raise the bridge deck proportionately, and doing a 2-dimensional expansion of the plan approximates a 50/44-like configuration. From the helm, you now have to see over a much greater expanse of cabin top and deck with no height advantage. This could be the single most serious controlling issue of the size envelope and at least partially excuses some of the bizarre helm configurations to be seen in the market. At 50’ the corners of the vessel are a long way away; difficult to see over, and more difficult to get to from any helm position.

It is significant that the otherwise comprehensive CE rules requiring minimum visibility from the helm of a powerboat have no like application for sailboats, the presumption being apparently that you will never be able to see where you are going. We just don’t find this premise acceptable as a design parameter for a limited crew cruising vessel.

2) “Split levels”

The relative heights of accommodation decks, weather decks, bridge deck and water surface are all exaggerated as the vessel size goes up. What works well in the mid-40’s vessel size as regards step and seating heights becomes very problematic if you wish to avoid an Escher-style exercise in staircases and landings.

Escher staircase

There is a tendency to abandon recognized ergonomically correct step proportions to disguise this effect in many current designs, especially in the transom area, a dangerous practice for any vessel. If a design works well, you should be able to move around the vessel without much thought and without any head impacts, knee injuries or fatigue.

3) The individual in relation to the vessel

Evaluating a cruising vessel’s capacity in terms of its “floor area” is misleading when considering its functionality. A vessel of this type that is 50/44ths the size of a 44’ vessel in terms of length will be approximately 45% larger in terms of structurally supported surface area. This is a vast increase in terms of windage and weight, all of which has to be driven through the water. Mechanical systems, spars, sails, ground tackle, etc. must all go up in size accordingly and rapidly exceed the capacity of an individual’s (couple’s) handling effort.

Reliance on powered systems becomes not just convenient but critical to operation. All cruising vessel tasks should really be planned for one or two individuals in possibly very arduous circumstances. This is a limiting factor and a fresh design exercise therefore demands that the “mission profile” be fulfilled in the most economical manor, without superfluous space or volume. The application of this maxim is not particularly important for vessels which receive casual holiday use but for a voyaging vessel, the benefits to be achieved are critical.

It is evident that cabin separation and privacy is a big advantage with any catamaran design over a monohull. The lower hull accommodations can be placed in the vessel extremities and common living spaces can be centralized. It is hard to reason that simply “more of the same” however will be worth the price to be paid.

There has to be some identifiable “extra” that is achieved by floor area alone to justify going larger with the design. We have yet to identify any sufficiently attractive extra features available with the 50’ vs 44’ potential floor plan, especially when working to retain the practical considerations essential for a couple’s liveaboard vessel. You could end up with more vessel than you can comfortably handle.

Bigger is not in fact necessarily better and may constitute a serious liability. It appears to us that concentrating our design efforts in the mid-40’s range of vessel size will produce the most rewarding results for our customers and by doing so we will continue to offer the most efficient cruising vessels available in the market.

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3 thoughts on “Ideal Vessel Size – Less is More

  1. My Seawind 1000 works for me. There is enough to do to take care of this boat. Anything bigger would take away sailing time. Roger

  2. Having just completed a circumnavigation on a ULDB 50′ monohull, we look at things from a slightly different perspective than most cruisers. One of the key lessons that we learned is that weight is a critical factor when making extended passages. Even for a couple, we calculated that we had almost four tons of gear to support our lifestyle. From what we have seen, cats are equally susceptible (or maybe more so) to overloading as ULDB monohulls. If we start with the four ton payload, there don’t seem to be many cats that will perform well crossing oceans below 48′ or so. By perform well, I mean sailing at speed with the design waterline at or above the water surface. I’m assuming here that payload is calculated in light ship condition and the actual payload would include all of the “extras” that one needs to live aboard for an extended time frame (fuel, water, food, clothes, sails, safety gear, anchoring and docking gear, dinghy, motor, spares, utility (watermaker, solar panels, wind generator, etc.), communications and navigation gear and entertainment/sporting gear (fishing, scuba, DVD, stereo, etc.)). For shorter ocean passages in areas where spares/repairs can be easily accomplished and re-provisioning can be accomplished every couple of weeks, it might be possible to keep the size to the low 40’s. I agree that bigger can make it more difficult, but smaller and overloaded also poses serious safety concerns.

    • Thank you for your thoughtful comment.
      There are obviously some inherent difficulties in using vessel lengths as a criterion for comparing such divergent hull forms as a ULDB and a displacement catamaran but I presume you have been observant of the vessels around you in like service and noticed a preponderance of older catamarans with diminishing bridge deck clearance, amongst other things. I think you made a good observation when you included the qualifier “support our lifestyle”.

      I would caution you against using the “design water line” as a measuring stick for predicting performance. The DWL is a drafting and calculation bench mark and has little or nothing to do with what you see when you look at bottom paint and boot stripes. There is no way you can know without hydrostatics and draft measurements how a boat is floating and furthermore, the designers expectations and intentions may have been considerably modified as the design progressed, making the DWL vestigial in nature. What you can observe is bottom paint usually applied substantially higher than what “heavy” displacement will likely demand and striping to complement the aesthetics. A vessel that appears to be very high in the water may in fact be floating a lot lower than intended, and vice versa.

      The light displacement hulls that went with the early multihull design/lifestyle philosophy. e.g. unclothed vahines for crew, sleeping and cooking zones rather than cabinetry, oars, etc. has led to a lot of older vessels being asked to to support the burgeoning loads attuned to current expectations. The PDQ36 design, which was a forunner in production cats and already about 20 yrs. old when I came on the scene, was originally concieved of as a speedy lightweight cruiser with minimal equipment. It continues to enjoy huge popularity as a cruising vessel long after production has ceased though it is customarily loaded far beyond the original designed weight and has a bridge deck clearance that suffers accordingly. The owners are universally happy with the vessel though, having defined its performance in concert with their own “lifestyle” and the attendant load of stuff it entails. If the boat is a little slower or less ocean worthy than it could be, that’s OK, they have a TV and AC etc.

      When a successor vessel was conceived, eventually emerging as the Antares 44, the idealism of the early multihull years had given way to cruising pragmatism and the design was preceded by a weight study that reflected every likely accessory that an owner may want. (They can always find something to add however, so some margin needs to be allowed for.) The hulls were configured to hold up the resultant maximum weights as efficiently as possible. This is just reasonable project planning. I had some previous commercial vessel design background and was accustomed to approaching a design with more pragmatism perhaps than was common with yachts these days when “How do I look? How much carbon fibre can I afford?” often seem to be the preponderant criteria. This is not to suggest that pleasing appearances and speeds are not highly desirable but the realistic capacity has to be there or the vessel will never be able to shine in its designated role.

      Much of the stuff you have included in your “payload” we would actually assign to a lightship condition, in harmony with the ISO standards. All installed ship’s systems, equipment, safety gear and ground tackle are not considered as disposable load, they are there when the voyage starts and they are there when it finishes. This makes your four ton add up probably fairly consistent with or actually under our own weight study.

      The yachting press has a bad habit of irresponsibly publishing undefined so called payload numbers and drawing conclusions. I appreciate the particular clarification of your derivations, (you have to think like a scientist). The detailed weight study is the only way to define the inclusions and exclusions of a “payload” and what constitutes “lightship”. “Performance” is another abused term. Obviously Playstation or Orange outperform everything at speedy voyaging but they would perform very poorly as a liveaboard vessels for a cruising couple.

      I believe we are the only production builder to freely offer the weight study and hydrostatics cross curve chart to our owners if they want them. These numbers and calculations are however only abstractions and I hope they do not get in the way of simple observation. If your boat’s bottom paint colour can only be appreciated by the fishes, it is time to get a bulk disposal box on the dock and pitch some stuff into it. We are dealing with floating objects after all. It is always satisfactory to “lighten ship”, regardless of its size or type. If your “lifestyle” demands a minimum of four tons of stuff, whatever boat you own will float accordingly. If you can’t afford or support or conscience a vessel of size or type to carry it off casually, the weight of your lifestyle will have to adjust.

      As long as you are enjoying yourself, the boat works for you. We have several Antares 44’s currently at sea with couples, guests and families aboard (plus AC, gen set dingy etc.). Some are on the far side of the globe or have been there and back. The reports are all positive, nobody’s lifestyle appears to have been compromised and they have racked up some impressive runs under sail.

      It is apparently possible to voyage in a catamaran less than 50′ long and I reiterate my point that safety may be equally or more compromised by having more boat than you can handle as it can be by being overloading. The worst case is having more boat than you can handle and then filling it with more stuff than you need, after all the space is there, especially in a cat, so the temptation is obvious. I am not sure how to equate the length of a ULDB to a cruising cat design, apples making lousy oranges.

      Regards, and Thanks

      Ted Clements

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