Définitions fondamentales de l'architecture navale
Pour aborder la question de la vitesse et des performances d'un voilier, il est indispensable de maîtriser le langage technique qui définit ses dimensions. Traditionally, LOA (length over all) equaled hull length. Today, many builders use LOA to include rail overhangs, bowsprits, etc. and LOD (length on deck) for hull length. LENGTH WATERLINE (LWL): LWL is the length of the hull at the level where it sits in the water (the waterline) as measured from the bow ending at the waterline to the stern ending. BEAM: This is the greatest width of the hull and is often expressed as Beam (Max). DRAFT: This is the depth of the hull from the LWL to the bottom of the keel or fin. Like the LWL, it will vary with the weights of fuel, water, stores and equipment. A boat’s actual draft is usually somewhat more than the original designed or advertised draft. For boats with adjustable keels (centerboards, daggerboards, lifting and swing keels), Draft (max) is with the board down.
DISPLACEMENT: If you weigh the boat on a scale, that is her actual displacement. It is the weight of sea water that she will displace when she is afloat. Many designers figure displacement when half loaded with stores, liquids and crew. Some report light displacement (aka lightship) which is the weight of the hull and permanent equipment but with empty tanks. Light displacement does not include stores, optional or removable equipment. GROSS/NET TONNAGE (GRT/NRT): Not a measure of the ship’s weight or displacement, gross tonnage is a ship’s total internal volume expressed in “register tons (GRT)”, each of which is equal to 100 cubic feet (2.83 cubic meters or 748 US Gallons). Net tonnage (NRT) refers to usable space by subtracting from gross tonnage the volume of spaces such as engine rooms, fuel tanks and crew quarters. BALLAST: Material that is placed low in a vessel to improve its stability. S.A.: Sail Area. The total combined area of the sails when sailing upwind. S.A. (reported) is the area reported by the builder. (Verses S.A. (100% Fore + Main Triangles) which is the area as defined by the rig measurements.)
L'Hirondelle : Un concept britannique historique
Le nom "Hirondelle" évoque une lignée de navigateurs passionnés. Il existe plusieurs récits entourant ce patronyme. Par exemple, après une dizaine d'années de navigation en Méditerranée, à faire du charter, Jan et Pauline rêvaient de construire un voilier. C'est dans une vieille grange en pierre dans la petite bourgade d'Ougney La Roche que Jan et Pauline débutent la longue construction de la goélette. Ils fabriquent les membrures, mettent en place les bordés, les couvrent de tissu et collent le tout ensemble. Ils se renseignent sur le plomb pour la quille, creusent un trou sous la coque, construisent un moule et un système de rigoles pour couler le plomb dans la quille. Ils construisent les barrots de pont, et le couvrent de lattes en iroko. Ils installent un moteur. Un voisin sympathique leur a offert deux arbres, deux spruces pour les mâts. Des hirondelles ont adopté la coque pendant toute la construction : le nom de baptême était trouvé. La coque, le pont, et les aménagements terminés, ils mettent le cap sur Amsterdam en passant par les canaux. Aux Pays-Bas, des maîtres voiliers dessinent le plan de voile et le gréement d’Hirondelle. Pendant près de 15 ans, ils naviguent à travers la mer Nord, les canaux d’Europe, la mer Noire et la mer Méditerranée. Sentant le besoin de retrouver les terres familières, ils rentrent dans le Doubs et reprennent une vie sédentaire. Depuis qu’Hirondelle est entre nos mains, nous leur donnons régulièrement des nouvelles et posons toutes nos questions - la chance d’être conseillés par à la fois l’architecte et le constructeur !
Toutefois, dans le monde du multicoque, le catamaran Hirondelle possède une identité propre. Ce clever little catamaran was introduced in 1968, designed by Chris Hammond and built by the British yard Brian Carvill & Associates. According to a feature story in the September/October 1994 issue of Multihulls magazine, more than 300 were sold. Forty-some years ago, empty-nesters Richard and Sheila Olin sold their business in Chicago, and with their two daughters in college, boarded their British-built, 23-foot Hirondelle catamaran and headed south. In 1987, they sold the Hirondelle and bought a Gemini 3100 catamaran for more spacious Florida cruising. Once a multihuller, always a multihuller; level sailing and speed are persuasive.
Conception technique et architecture du catamaran
La performance du catamaran Hirondelle repose sur des choix structurels précis. Hammond decided on symmetrical hulls of sufficient width for single berths. The original daggerboards make for superior upwind performance, a talent in which multihulls are generally inferior to monohulls. The trade-off is additional manufacturing cost and complexity, i.e., trunks and raising/lowering lines and hardware. Bridge clearance and configuration affect two things: wave slap and interior volume. The space forward between the hulls is mostly solid, that is, fiberglass, with just the most forward foot or so filled by a “tramp” or netting. On a small boat of just 23 feet, the extra weight of the solid deck is a concession to the Hirondelle’s cruising side, as several lockers are stowage for ground tackle, fenders, and lines.
Lire aussi: En savoir plus sur l'Hirondelle catamaran
The foredeck is mostly solid, with a small area covered by netting. While little information about construction is available, the hull is single-skin fiberglass; one owner says the deck is cored with balsa. There are no liners in the hulls or on the underside of the deck. As with most cruising catamarans, the bridge deck is where crew gather for meals and evening games before lights out. The U-shaped dinette easily accommodates four, and the table lowers to form a large berth, somewhat disturbed by the compression post under the mast. Depending on crew number, the two single berths in the aft ends of the hulls and the single forward in the starboard hull may suffice. The head with portable toilet is forward in the port hull, and a small galley with a two-burner stovetop is abaft the dinette in the bridge deck. The single berth aft in the starboard hull. There are numerous cubbies for stowing stuff, all without doors; remember that multihull performance is predicated on light weight, beginning with the absence of ballast and perpetuated throughout design and construction by eliminating unnecessary features, such as cubbie doors.
Analyse des performances en navigation
La vitesse est le point fort de cette unité, bien que sa gestion demande une attention particulière. According to sailboatdata.com, the original design was soon modified with a shorter rig, carrying just 220 square feet of sail. On Full Circle, Richard has opted for a roller furling headsail and mainsail; a man in his 80s doesn’t need to be teetering around the foredeck and cabintop. Richard can set and furl both sails from the safety of the cockpit. The main cabin is dominated by the dinette, which easily seats four. Many years ago, a Hirondelle won the multihull class in the Around the Isle of Wight race, though the particulars are not known to this writer. I have, however, enjoyed a daysail with Richard on Sarasota Bay and found performance to be lively. He says it’s best to lower both boards, which we did.
Full Circle is equipped with a Raymarine ST1000 autopilot that Richard controls with a remote. Because of the boat’s lightness and absence of ballast, maintaining momentum when depowered while steering through a tack is best accomplished by a gentle turn rather than quickly throwing the helm hard over. Manufacturer’s sailing instructions that accompanied the boat emphasize that catamarans can capsize and not return to level. The message is to reduce sail early. Regarding beam and close reaching, the instructions state: “Except on a very close reach, beware of luffing in response to gusts, because an abrupt luff may aggravate heel by banking up water against the lee hull and centreboard. On some catamarans the technique is to bear away during gusts in order to help the boat absorb the wind energy by accelerating; but this is not appropriate for Hirondelle, which accelerates better if held straight. An outboard motor mounted in a well aft in the cockpit provides auxiliary power. While the boat can handle up to 25 horsepower, Richard finds his new fourstroke, 8-hp Honda more than adequate and wonderfully quiet. Short- and long-shaft motors work, though the short can cavitate in certain wave states, and the long may risk running aground if not tilted, as it projects below hull level. The Hirondelle is a versatile family cruiser for short cruises and spirited daysails, with speeds surpassing most monohulls of similar length.
Lire aussi: Expérience culinaire en catamaran
Lire aussi: Voiles de catamaran expliquées