Comfort in multihulls
Multihull creature comforts
Not only are the decks of multis more or less on a level, they are also spacious. There is room to spread out or entertain a crowd aboard, even on the smallest craft. Designers have plenty of scope for exploiting a variety of interior configurations ranging from the spartan to the luxurious - the options of course broader for larger craft.
Berths and bunks
Catamarans less than 6 m (20 ft): The hulls of very small catamarans, below 20 ft (6 m), are too tiny to enter, so a boom tent normally could be the only provision for overnight shelter on boats this size. Still, tents work very well over wide decks - even tents intended for conventional camping!
Catamarans 6 m (20 ft) to 8 m (26 ft 3 in): In this size range there are several micro cruisers with central bridgedeck cabins. Typically, the main cabin has a dinette with sitting headroom that converts to a double bunk. In addition, single berths and a head are fitted into the hulls.
Open bridgedeck cats, intended for racing or camper-style weekend cruising, are more common in this size, however. In these designs, the only permanent accommodation is in hulls. They are rather tunnel-like, but wide enough to accommodate at least a 22 inch (0.55 m) single bunk. Fitting crawl-in berths in the ends of each hull of a small catamaran makes a simple, open bridgedeck four-berther, with access to below from amidships. The centre section of the hull of this type is often raised to form a sheltered area for changing clothes, sitting and use of a Porta Potti or small cooking stove.
Catamarans 8 m (26 ft 3 in) to 10 m (32 ft 10 in): The smallest catamarans designed for lengthy cruising or live aboard are in this size range. Usually they are designed with sufficient freeboard to give standing headroom in the hulls, allowing easy passage to accommodation or storage fore and aft. The good headroom also makes a hull a practical location for the galley. A bunk, occupying the whole width of a hull, would not be wide enough to be a double, even with some topside hull flare. So many designs have a double master cabin spanning the bridgedeck, forward of the saloon with access through one of the hulls. As with most boats, a dinette usually converts to a double bunk for additional berths.
Catamarans over 10 m (32 ft 10 in): The hulls of larger catamarans are a perfect place for cabins. Headroom is available; the long corridor-like space makes it convenient to add adjoining facilities like closets and bathrooms; there are two hulls each with two ends, so it is easy to have several similar cabins. A cabin in the end of a hull is far from any through traffic, and is a private, secluded retreat, adding to the popularity of catamarans for charter holidays.
Catamarans conceived with charter business in mind, or designed to maximise the accommodation facilities, are likely to have relatively beamy hulls as this creates more volume for the cabins. Such models might have a length-to-beam ratio as low as 8:1. Stubby hulls like this have more drag than slender ones which, on performance-oriented cruisers, are likely to be around 12:1.
Where the hulls are not wide enough to house a double berth, or to make a particularly spacious stateroom, it is common to build part of the cabin overlapping the bridge deck, either forward or aft of the saloon. This is a convenient solution for a cat as there is so much horizontal space with which designers can work, though encroaching upon the bridgedeck still means some compromises. A cabin in front of the bridgedeck saloon could mean more weight and depth of structure forward and less underwing clearance, all of which designers would work to avoid in the interests of ride quality and seaworthiness. A cabin aft of the bridgedeck saloon may dramatically reduce the size of the cockpit, or require a lower bridgedeck clearance with, as in the previous case, the increased likelihood of slamming in unfavourable conditions.
Trimarans: There are only a very few trimarans with accommodation in the floats, since these are too small and exposed for anything but storage except in rare huge boats. So, interior living space is confined to the main hull, meaning tris have layouts below decks similar to those found on monohulls. Since the main hull on a tri should be slender in order to reap the performance advantage of being a multihull, the available volume for accommodation can be quite confined. However, a very pronounced flare of the hull above the waterline compensates for a narrow main hull in many trimaran designs.
For small multihulls, below 8m (26 ft 3 in), trimarans usually can have more comfortable accommodation than catamarans, but this advantage rapidly switches to the cat as models get longer.
A saloon is the social centre of the boat under shelter; a protected place to sit and eat at least. The minimum version of the saloon, as found in the smallest vessels, comprises merely a dinette with bench seating that converts to bunks with space for little else.
Comfort, pleasure and social life aboard, however, can be enhanced considerably in a grander, more lavishly featured space, especially if it has wonderful views.
In catamarans : What more feasible place to build an inspirational saloon than on the broad deck of a catamaran? Notable French catamaran designers have contributed a lot in pushing saloon design beyond the functional with wide areas of glass window, stylish décor and boldly curveatious furniture.
Still, though perfectly positioned for views on all sides, and with easy access without having to clamber down a steep companionway, the saloon on a cat has drawbacks. The most significant is the high windage. The height of a bridgedeck cabin with standing headroom, on a catamaran, is simply governed by the water clearance under the wing and plus the height of a standing person. Without careful design, this height superstructure, even on a large cruiser, would cause an unacceptable degradation of windward performance by today’s standards.
Many early catamaran cruiser models had relatively large, slab-sided main cabins which caused a lot of drag in the wind and subsequently they were notoriously prone to bad windward performance compared with monohulls. Where performance is paramount designs will dispense with the bridgedeck cabin altogether and have the deck open, with covered shelter only inside the hulls – or have a low cabin on the bridgedeck with sitting headroom only.
Modern designs of cruising catamarans often have distinctly rounded superstructures specifically to reduce windage. This measure, along with restricting the size of the bridgedeck cabin within certain proportions to reduce the boats exposed profile, allows good performance to windward as well as having the comforts of a good saloon.
In trimarans: Trimarans, especially more modern designs, have a very wide overall beam, even more so than catamarans. In the interests of keeping displacement light, and air drag low over these expanses of deck, the gap between the hulls is usually spanned only by beams and a trampoline. Therefore accommodation is restricted to the main hull only, with the saloon invariably amidships, in the widest section. With less volume available, saloons in tris are more modest, don’t have the panoramic views, and are much less spacious than those found on catamarans. However, no high windage structure is needed to enclose them, and trimarans typically have excellent performance to windward. Most trimarans have a very exaggerated flare in the main hull to increase the saloon size as much as practicable.
Some trimarans, especially older designs, have all rigid decks allowing even more beam-wise extension of the main cabin.
Out in the open
All multis afford those aboard with generous 'spread-out potential' on decks, trampolines or in the cockpit. Not that these expanses are always inviting. When the weather gets up a bit, wind and spray can soon drive net-loungers to shelter - on the other hand, the spray through the nets may provide a welcome refreshment in warm weather. In any case, the open spaces are an important asset and, along with some of the multihulls virtues (level sailing for instance), help a lot to make voyages enjoyable for all.
Just as the saloon is the social focus inside, on the vast majority of boats, the cockpit is the natural space for congregation outside. Especially since the boat is also sailed and steered from this station, a big cockpit is very useful when there are more than a couple of people aboard. Accordingly, many bigger catamarans have very wide cockpits equipped with tables and seating for relaxing and entertaining outside - sometimes these boats are referred to as 'party platforms' because entertaining large groups of people is so easy on them.
When numbers aboard increase, wide and unimpeded access to intensively used parts of the boat becomes more and more important. Designers of catamarans which are successful in the charter business usually have made sure people can move easily and pass others moving from the swim steps, through the cockpit, and into the saloon. As far as the work of sailing the boat is concerned, a smaller, well-sheltered and protected cockpit with good visibility is ideal. Some cats are built this way as, from necessity, are most trimarans.
No gimbals are needed in the galley of a multihull, tri, cat, or proa, because they don't roll or heel enough to need one. Naturally, this also means less stress on the person preparing food. Furthermore, galleys can be more easily designed with front opening drawers and refrigerators as there is much less risk of provisions being dangerously thrown out of their storage location in bad weather.
Besides being on a level, long counters, good headroom, and easy access makes a galley comfortable to work in - conditions usually found in the middle of a hull of all but the micro cruiser catamarans. Builders of larger cars frequently offer a 'galley-up' version as some people find the 'galley-down' configuration too isolating for the food preparer.
Some catamarans, particularly those configured for charter, have as many well appointed head and shower compartments as cabins. The tiniest cruisers commonly make do with a Porta Potti, though a marine toilet can be fitted in very small boats.
Central heating, air conditioning, refrigerators, hot water, television and other systems will enhance living conditions on a multihull as well as on any boat, given sufficient energy or fuel. On catamarans a bridgedeck cabin is a very convenient structure to support a bimini cover, pilot house roof or complete cockpit enclosure. Biminis, hard or soft are, the most popular way to get sun protection on cats and can be used under sail. Likewise it is normally easier to make provision for natural ventilation on a catamaran than other types of vessel as there are more places to fit hatches that will not obstruct operating the boat if conditions permit them to remain open.
Performance cruiser or floating condominium
The good performance of multihulls is soon degraded when they are overloaded. This is especially easy to do on a catamaran where there is often a lot of convenient storage space to accommodate gear. Often the cruising sailor has to weigh the advantage of a bit more speed potential or another item of luxury.