The most interesting feature of the TRIDENT 46 is the center hull. Its primary purpose is to improve seaworthiness, but it also provides quite a bit of storage space, including room for a workshop (with stand-up headroom), engine room, generator, watermaker, rudder, and battery bank. Removing these items from the outer hulls allows more room and flexibility in designing the interior, and needing only a single engine reduces weight, cost, and construction time. To regain the maneuverability associated with twin engine multihulls, several manufactures sell small electric bow thrusters that can also be installed in the center hull.

The TRIDENT 46 has a 24’ beam, 48" draft, and a displacement of 22000 lbs. The aft sections of the outer hulls are full, and only slightly vee’d, which increases interior space and promotes high speed reaching. The forward sections are flared to insure good reserve buoyancy and quick recovery if you do punch a wave.

The center hull blends into the outer hulls by way of two tunnels, that smoothly direct the flow of water under the hull. The minimum vertical clearance in the tunnels is 39", and there are no flat surfaces, which cause the uncomfortable pounding associated with traditional catamaran designs. Another advantage of eliminating these flat surfaces is that the curved panels are much more efficient at carrying loads, and don’t "oil can" or require heavy stiffeners. The TRIDENT 46 has a disp/lwl ratio of 141, which favors cruising rather than racing. Likewise, the sail area/disp ratio, 22.7, is also optimized for cruising. Top speed under power will be around 6-7 knots, with a range of approximately 1100 miles (140 gal.).

A sloop rig with a full batten main, roller furling 130 Genoa, and self-tending staysail is the recommended sail plan. A pair of long shallow keels that draw 4’ 6" provides good windward performance. If less draft is needed, the center hull can be fitted with a centerboard, reducing draft to 3’. Speed under sail is expected to be in the 10 to 12 knot range. Nothing to brag about around a group hard core racers, but quite respectable performance for a cruising boat, where comfort and safety are the primary design constraints.

The main cabin is optimized for offshore cruising, and includes a navigation area with an inside steering station and pilot berth. Both popular during periods of bad weather. The "U" shaped aft galley has a freezer & refrigerator, double sinks, ample counter space, and a large pass through window between the galley and cockpit. The dinning area is to starboard, and includes a movable section that can be placed to hide the steps leading down into the workshop and engine room.

PLAN VIEW, TWO CABIN LAYOUT

Port and starboard stairs lead down to the outer hulls, which contain matching staterooms, each with a head and shower. The staterooms are spacious, with lots of drawers, a hanging locker, and built in seats. Headroom is 78", and each cabin has three opening ports, two in the hull, and one in the aft bulkhead, over the double berth. The room left over in the forward portion of the outer hulls can be used for additional berths, general storage, a pantry, wine cellar, laundry, or computer room.

ELEVATION

The workshop area, which is part of the center hull engine room, has room for a workbench and lots of storage in deep lockers to port and starboard. The engine is completely enclosed in a sound deadening box, reached from the workshop by removing the steps, or via a hatch in the main cabin sole. Depending on how you intend to use the boat, the engine room area has space for a generator, water maker, bow thruster, or additional fuel tanks. An interesting propulsion option is the Yanmar Sail Drive. This is a very low drag, compact unit, completely self contained, with up to 40 hp.

The cockpit area is reached from the main cabin through a 3-foot wide, sliding door. It contains a built in table and seats, secure access to the swim steps, and an outside steering station wide enough to seat two. A wet locker, built into the cockpit sole just aft of the sliding cabin door, acts like a giant cockpit drain and prevents water from getting into the cabin. A pass through window connects the galley and cockpit. Genoa and traveler control lines run aft to winches on the deck, just aft of the cabin.

Eliminating the twin engines normally found in cruising multihulls not only saves a whole lot of money and weight, but also allows several interesting interior variations. In the base line configuration, the staterooms are moved forward two feet, allowing secure passage between the cockpit and swim step areas (built into the "sugar scoop" transoms). The sides of the swim step area contains seats with storage for dive gear, and flammables like propane and gasoline. The berths in the aft staterooms are elevated 30" above the swim step and stateroom sole. This space can be reached from the swim steps, and is large enough to contain the forward half of a 10-foot inflatable, with its outboard attached. A hinged ramp, with built in rollers, allows the dinghy to be pulled aboard and stowed securely behind the raised (and locked) ramp, by one person. No more stolen dingys, strained back muscles, or lost deck storage space. Other arrangements include a dive platform, with a built in high-pressure compressor and storage for bottles, wet suits, bc’s, etc. You can think of this area as a "garage", and tailor its volume to suit your needs.

The building sequence for the TRIDENT 46 may seem a little unusual, but it has been proven to work well for homebuilders. Construction begins by setting 4x4 posts into the ground, around the contour of the main deck, then cutting them to the height of the shear line and deck camber. 20 foot long 2x6’s are then laid across the posts and shimmed to the plan’s dimensions. The deck panels are lightly glued to the support structure and laminated with epoxy to a thickness of ¾" (three layers of ¼" plywood). After a rough trim, the deck is covered with one layer of 24 oz. Woven roving, with an additional transverse layer of 12" bias ply tape (the fibers run at +/- 45 degrees rather than 0 and 90) at each of the six permanent bulkhead locations.

At this point, we need to stop and think ahead a little. Is transporting a 24-foot wide catamaran going to be a major problem? If it is, now is the time to build some simple wood and fiberglass lap joints along butt line 60 (BL 60), splitting the boat into three sections, two 7’ wide and one 10’ wide. The outboard sections can be bolted together, allowing the whole boat to be moved with two conventional truck-trailer rigs. When the launch area is reached, the pieces are aligned, sealed, bolted, and fiberglassed into a single unit.

The cabin is built separately from the deck, using wood strips over forms, glassed on both sides. The preferred sequence is to build the cabin after the deck has been fiberglassed, then position it under the deck structure, and bond it in place. If you decide to attach the cabin after the hulls are turned over, it’s a good idea to mold a 4" high "lip" around the deck to the dimensions of the cabin. When turned over, this lip will align the cabin and provide structure for bolting it to the deck. In either case, the cabin is positioned on the deck, bonded with epoxy, and glassed with bias ply tape, inside and out.

Hull construction begins with the fabrication of six full width primary bulkheads and two partials, using two layers of 1/2" construction grade plywood as a core, faced with 1/2" mahogany plywood ( 2" total thickness). These bulkheads are positioned on the deck, aligned, and glassed in place permanently using 12" bias ply tape. To reduce weight, lightening holes are called out in the bulkhead templates, along with hollow areas. The remaining temporary forms, on 3’ centers, are built up from 1x6 stock, aligned, and tabbed lightly to the deck.

DuraCore balsa strips and sheets from Baltec Corp. are ideal for stripping the hulls and building the interior structure, but expensive. Wood strips cut from any clear 2x8 stock like redwood or western red cedar will work just fine. The type of wood is not critical since it will be completely covered with fiberglass. Even plywood, ripped from full length scarfed ½" panels, can be used. In both cases, a simple butt joint with a backing block is used to get the lengths required. Milling cove and bead features into the strips is unnecessary.

The strips are placed along the shear first, using a heavy layer of thickened epoxy to insure a good bond between the first strip and the deck. Position the strips with the backing blocks on the outside, where they can be easily removed later. The strips are epoxied to the permanent bulkheads and each other, and held in place with sheet rock screws. 1" wide strips may be necessary where the curvature is high, and several layers of thin vertical strips will be required to form the flare at the bow(s). When the strips have reached a point several feet above the deck, the inside of the hull to deck joint should be cleaned up and glassed with two layers of 12" wide bias ply tape. Glassing this area would be a nasty job if the boat were upright. Longitudinal stiffeners (3/4" plywood or DuraCore) can be added at this time. They are fiberglassed to the deck at the 30" and 60" butt lines and trimmed for a close fit with the strips and permanent bulkheads.

When the three hulls and the connecting structure are completely stripped, the screws and staples are removed, the surfaces faired, and everything covered with one layer of 20 oz. stitched tri-axial fabric. The fabric should be cut to overlap by 12" along the stem and keel area, and 24" at each of the four wing fillets. A second layer of tri-axial fabric is added below the waterline, and a layer of bias ply cloth is applied along the keels and the fillets just to make sure they are "bullet proof". Traditional fill and fair techniques are then used to finish the surfaces in preparation for painting. Be sure to use enough surface filler to prevent sanding into the glass. A lower cost option is to use 24 oz. woven roving, which is not quite as strong and more difficult to finish.

Inside the structure, the strips are cleaned up with a disc sander, and the permanent bulkheads, butt line stiffeners, and soles glassed to the hull skins (more bias ply tape) up to the point where hull curvature makes the job to messy. Check the entire boat for any missed places on the permanent bulkheads, soles, cockpit seats, and longitudinal stiffeners that can be glassed easily inverted. Before turning the boat over, add temporary wood supports from one side of the boat to the other, across the cabin and cockpit area. These should be bolted or screwed to the temporary forms.

Turning the boat over is a tricky operation, requiring a pair of cranes and some careful preparation. Four 20’ slings are placed around each end of the outer hulls then led in pairs to a crane on each side of the boat. The boat is lifted slightly and broken loose from the support structure. The support structure is then removed and the boat lifted about ten feet off the ground. The tricky part starts as one crane lowers while the other takes up, until the boat is hanging completely support by one crane. The other crane now resets its slings over the top of of the boat and begins to pull. Slowly the boat will turn right side up and you can breath again. It sounds worse than it really is, and there is little danger of the boat falling or breaking apart. Some builders have turned boats over using hay bails, tires, pickup trucks, and an old forklift, but I wouldn’t recommend it or even want to watch.

With the boat turned over, the advantages of this construction method begin to pay off, as the deck and hulls are almost finished. All that’s left on the outside is to trim and radius the hull to deck joint and glass the deck. Again, bias ply tape is used at the hull to deck joint. The cockpit sole can be installed next and glassed along with the seats. Inside the boat, the temporary interior forms are removed and the insides of all three hulls and the connecting wing structure are cleaned up and glassed with one layer of 20 oz. stitched tri-axial fabric. As before, a 12" overlap is formed along the keel of each hull. An extra layer of full width (39") fabric is then added over the fillets between the hull and wing. Two by six beams on 12" centers are glassed across the wing structure (out to butt line 60) to support the cabin sole, and the sole (two layers of ½" plywood) is then screwed and epoxied to the stiffeners. The sole is then glassed into the hulls and bulkheads with bias ply tape, and covered with one layer of 2o oz. stitched tri-axial fabric. Ideally, these pieces will have been taped together while the hull was upside down, then taped and covered when turned upright. The goal is to have every permanent bulkhead, longitudinal stiffener, and sole panel securely glassed to each other and the hull, in as many places as possible.

With the primary structure now complete, the interior features can be mocked up, propulsion details sorted out, and thoughts given to the electrical, fuel, sanitary, water, rigging, sails, deck hardware, etc. Three arrangements are offered. They include a two cabin version, either identical or one "owners" cabin and one "guest" cabin, and a four cabin charter arrangement.

A power cruiser variant of the TRIDENT-46 is also available. The basic hull form is unchanged, except the shear line and cabin / cockpit soles are raised 10" and the fiberglass thickness is increased in selected areas. This provides space in the middle of the center hull for a molded in place 500 gal. fuel tank. In addition, a 10" raised landing is added under the steps leading down into the outer hulls. This provides space for another 200 gal. tank, giving a total fuel load of 900 gal.. Since these tanks are located near the center of gravity, the boat will not go out of trim as fuel is consumed. The workshop area is modified to accommodate a larger (80 - 100-hp) engine. Fully loaded, the displacement is 28,000 lbs., and the draft to increases to 4’. On deck, a small raised cabin is added over the engine room. This cabin is fitted with a removable overhead to allow access to the engine for major overhauls, and fitted with an 18" square opening hatch for light and ventilation. The main cabin extends into the cockpit 4’, and is fitted with a flying bridge.

Many custom features are possible for a project like the TRIDENT-46 depending on the individual needs of the owner. The complexity of these features, the amount of design work needed, labor expense, and hardware quality will largely determine the overall cost of the project. As a minimum (work full time on the boat, use lots of used stuff, and nothing fancy), I would estimate $50k and 2-3 years. $100k and 6 years is probably more realistic, especially if you need to work a regular job at the same time.

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