Erin, Antrim 30 Trimaran
The prototype Antrim 30+ trimaran "Erin" was built for Dr. Dan Buhler and launched on December 9, 1993.
Easy handling and high performance sailing are features of this high quality and ocean rugged racer/cruiser. High buoyancy and dynamic lift from the unique ama design provide an unusual level of safety and control. Asymmetric daggerboards fitted in amas for upwind efficiency do not intrude upon interior accommodation spaces.
Open, spacious interior includes two double berths and functional galley with dinette.
Folds to 10' beam for docking or trailering. Amas swing forward.
State of the art construction includes carbon fiber wing mast and bowsprit. Composite/foam sandwich construction in hulls, decks, and crossbeams.
Features
Hull: Unique hull shapes designed for excellent handling and level trim with plenty of reserve buoyancy where needed provide safe sailing even at high speeds.
Sailplan: Easily handled three sail rig with self tacking jib, boomless, fully battened main on wing mast,and asymmetric spinnaker.
Deck and cockpit layout: Comfortable cockpit with efficient sail handling layout and unusual whipstaff tiller. Swing up rudder.
Engine: 8-9 horse outboard on retracting transom bracket.
Accommodations: Twin double berths, galley and dinette with folding table, nav. area.
CONCEPTS
My 40' trimaran design Aotea, launched in 1990, was an enormous success, setting numerous records, including the fastest sailing voyage from San Francisco to Japan. She attracted considerable attention with her revolutionary ama hull shapes and aerodynamic styling. Aotea was designed as a single/double handed ocean racer; and as such, had to be easily handled by a small crew. I'm not sure how many competitors noticed - as Aotea roared by at twice their speed - that owner Peter Hogg was often sitting alone in the cockpit, casually smoking a cigarette as he self tacks out the San Francisco entrance, while their large crews sweat and grind to tack big genoas.
Alameda Multihulls did notice. They felt the sailboat industry was headed (finally) toward more speed and greater simplicity; and I heartily agreed. They were looking for a folding trimaran, about 30' long, with strength, seaworthiness, and styling similar to her "big sister". We laid out a set of design parameters and priorities:
Simple rig - 3 sail basic inventory, wing mast.
Easily handled - Jib, main, & mast all self tacking. Asymmetric spinnaker on fixed bow pole.
Small crew required - Crew of one or two can handle the boat easily. Your novice friends can come along for the ride.
High speed - That's what multihulls are for, isn't it?
Safety - "Ocean capable" means that you can sail the boat hard in real waves and serious San Francisco type winds, without having constantly to sweat about a structural failure or an impending pitchpole. I believe strongly that a safe multihull design must keep the bows up. Safety and speed in windy conditions are dependant on keeping the leeward ama bow from burying.
Simple, functional interior and deck - spacious feel and berthing for four adults
Wide load trailerable - folds to fit berth
Design priorities
This is a sailboat. Desirable sailing characteristics will not be sacrificed for secondary considerations.
This is an ocean capable boat.It has to be strong, and must sail well in real ocean sized waves.
Keep the junk out of the water. No waterstays, hinges, akas, or deck edges dragging in the water. Unnecessary drag is slow, wet, and dangerous.
Unique Combinations of Special Features
They say there is nothing truly new in sailboat design. Everything has been tried before, somewhere, at least once. Who am I to argue? That may be so. Yet the Antrim 30+ stands out for a unique set of features, artfully blended to a new, surprising, and pleasing whole. And I state this, of course, with all due humility.
Folding System
We spent countless hours analyzing different folding systems. In hindsight, the path seems simple. Vertical hinging methods, while I admire their ease of operation and clever structural geometry, were eliminated right away for failing priority 3, and because we don't like seaweed on the side of the ama. Once horizontal hinging was settled on, the question was forward or aft? I liked forward folding immediately since it seemed better suited to resisting sailing loads. In the end, forward was the only way to nestle the hulls to a reasonable folded width – the relatively broad ama bows fitting in nicely beside the main hull bow; and alongside the bowsprit.
Spray Chine
The main hull features a sharp, above water chine, which does a very effective job of shedding water. This eliminates unnecessary wetted surface drag from the bow wave climbing the hull sides, makes for a much drier ride, provides additional reserve buoyancy when the bow is buried, and increases width for the forward double berth.
Winglets
The main hull deck flares out into the crossbeams both forward and aft. This serves multiple functions: reduced hinge loads; reduced spray; big, comfortable cockpit; big working area around the mast; reduced twist in the main hull.
Whipstaff Steering & Kick up Rudder
The boat is fitted with a vertical tiller (whipstaff). This steers like a normal tiller, especially with hiking stick attached; yet interferes with cockpit space even less than wheel steering. The hollow steering tube that the whipstaff is mounted on serves as the primary cockpit drain. The rudder is mounted in a cassette which kicks up for trailering; and to protect the rudder from severe collision damage. Since this boat is unusual in not having a keel or daggerboard as "protection" in front of the rudder; we felt the additional protection of the kick up feature to be important.
Retracting Outboard
We wanted a simple, user friendly outboard installation.The outboard must be protected from solid water when sailing, must not require mounting/unmounting at every use, must be controllable from the helm station.We settled on a simple and clean geometry.The motor bracket is mounted on tracks on the swim platform, so that the motor retracts to a protected location under the aft deck.
Watertight Companionway
The companionway opening is recessed, with a sliding lid above. The lid has nothing to do with closing the companionway; but simply serves to keep spray and rain out, so the companionway can be left open for ventilation in all but the worst of weather. The companionway hatch is strongly built and can be dogged closed - the idea being that it will be essentially watertight in a really nasty storm. If the worst happens and the boat flips, our intent is that the occupants will be able to bail the main hull dry and survive in relative comfort. Naturally, an escape hatch is also provided.
Swim Platform
The "back porch" is wonderfully functional for boarding, dealing with the outboard and rudder, or just enjoying a rumble seat view of the action on board. In only the first few days of sailing it has proven its value as an anti swimming platform, as two overboard sailors were easily retrieved, one from our boat, one from another.
Water Clearance
When your multihull gets ready to light off, there is nothing more annoying than having waterstays, struts, or crossbeams clipping through the wave tops. The space between the hulls should be clear of structure. High arched akas (crossbeams) on the 30+ carry ample water clearance even when the leeward ama is depressed. Waterstays were never an option. To the best of my knowledge, this is the only folding multihull without waterstays or struts.
Ama Shapes
These hulls are a direct descendant from Aotea's amas, which have worked brilliantly. The high buoyancy, planing geometry is highly resistant to burying the bow at any speed.
Nevertheless, every trimaran will occasionally bury the ama bow. When submerged, the Antrim 30+ highly rounded ama deck will shed water quickly. There is absolutely no tendency when the ama is submerged to slow or trip the boat. Remarkably, these factors make the boat both faster and safer. Here is an example of priority 1 in action. Flat decks and exterior hull/deck flanges would reduce construction costs; but we refused to sacrifice safety for cost.
As a result of my "multihull footprint" studies, the ama hulls are staggered slightly forward of the main hull. This, together with static and dynamic lift from the ama hulls, causes the boat to trim slightly by the stern when pressed, thus keeping the rudder in clean flow and resisting ventilation.
Canted Asymmetrical Daggerboards
The A30+ has a daggerboard mounted in each ama. Aside from opening the main hull interior to a phenomenal degree, this arrangement has several hydrodynamic benefits:
Each board now only need operate on one tack; so an asymmetric foil can be used, optimized like an airplane wing for normal operating conditions. This makes a tremendous improvement in upwind efficiency - the boat points several degrees higher than it would with symmetric foils.
In the conventional configuration of board or keel mounted on the main hull, as the boat is pressed the main hull lifts, causing the top of the board to get close to, or project through, the water surface. Thus, as loads go up, the conventionally mounted board becomes less efficient through loss of end plate effect. On the Antrim 30+ the effect is the opposite. As the boat is pressed, the board is pressed deeper into the water and gains efficiency.
Normally, rudders operate in the downwash field (angled flow) behind the keel, creating additional drag. The 30+ board and rudder both operate in clean flow.
Like the oars of a rowing shell, the boards provide initial stability. This is helpful when sailing in light air. (Ama hulls are clear of the water at rest.) Because the boards are canted, they also have a "flopper stopper" effect, greatly damping the tendency to slam from hull to hull in light air, leftover slop conditions.
Because the boards are canted, they develop vertical lift like a hydrofoil. Sailing trials have shown this effect to be stronger than anticipated. The boat seems to want to climb right out of the water at speed!I attribute this to a wonderful synergistic effect between the canted board and the planing hull shapes. High static buoyancy, planing ama shapes, and canted daggerboards form the holy Trinity of anti nosedive safety.
Construction
Hulls are sandwich construction using foam core - Airex in hull bottoms for impact resistance, and "rigid" PVC foams elsewhere. Skins are a composite of Carbon fiber, Kevlar, S-glass, and E-glass.Carbon is used in high load areas, and Kevlar in areas vulnerable to impact damage.Akas, daggerboards, rudder, and crossbeams are also composite, heavily carbon reinforced. Wing mast, bowsprit, and rudder post are essentially all carbon. Hybrid, vinylester, and epoxy resins are used as appropriate to the part.
Hulls, decks, crossbeams, interior, and final production tooling were built by Moore Sailboats in Watsonville. Wing mast, rudder, daggerboards, and bowsprit were built by Larry Tuttle of Waterat in Santa Cruz. You would have to go a long way to find two more talented and conscientious builders than Ron Moore and Larry Tuttle. Plugs for hulls and beams by Arne Jonsson in Alameda. Rudder post by Advanced Composite Concepts of Santa Cruz. Deck hardware and electrical systems outfitted by Rodney Morgan of San Francisco. Most deck hardware is Harken. Most custom metal fabrication was by Tom Carr of Santa Cruz. Sails are by Pineapple Sails.
Sailing Records:
1995 Doublehanded Lightship, SF Bay
1st to Finish, 1st in Class, 95 entries
1995 Doublehanded Farallones Race
1st to Finish, 1st in Class, 150 entries
1996 Three Bridge Fiasco, SF Bay
1st to Finish, 1st Overall, 215 entries
94, 95, 99, 01, 05 Doublehanded Farallones Race
1st to Finish (story at BAMA: 2001 Doublehanded Farallones Race)
Features:
Cover Photo and Article, Multihulls Magazine, Nov/Dec 1994
Sailing, January 1995
Featured on Discovery's television program, Next Step
Pineapple Sails Ad in Latitude 38