POWERBOAT DESIGNS
	MOLOKA’I STRAIT 79                        for voyaging   Built by: MOLOKA'I STRAIT MARINE Sales:   American Global Yacht Group                Annapolis, MD                Tel: (410) 827-0070   Designed and fabricated for serious voyaging and living aboard, the Moloka'i Strait 79 hull is constructed of A36 marine-grade steel. The deck house is built in 5000 and 6000 series marine grade aluminum. Moloka’i Strait Marine (MSM) is seeking serious buyers for the first few vessels. Owner participation throughout the entire design and construction process is welcomed and encouraged to truly customize each handcrafted yacht. The Moloka'i Strait 79, is a lengthened sister to the MS 75', which was launched in June 2006.  Based on experience with the first of that design, Hercules, which you can see on this page, MSM decided on a few changes, namely:   Make the hull 3' longer in the main saloon and the engine room directly below. Make the MS 79 a twin funnel design to open up below-deck spaces. Make the hull triple-chined for easier construction without giving up pleasant motion. Make the stern more square for extra buoyancy aft. Make all the structure in the hull below the waterline heavier for built-in ballast. These changes had a few very favorable advantages.  Generally, more room in the boat is always nicer, so the main saloon and engine room benefit from the extra space.  The single funnel is removed from the center of the main saloon, opening the view and the space, and two funnels are added at the side of the accommodation where they are much less obtrusive.   In the engine room on the MS 75, the engines sat backwards with V-drives, which is a more expensive situation, and service and maintenance on the propeller shafting is more difficult and expensive.  With three feet of extra length, the engines can be turned around to face forward, and less expensive conventional gear boxes can be used.  The propeller shafting is easier to reach for service and maintenance.   Round-bottomed hullforms, as it turns out, are generally more expensive to build than chined hullforms, even with CNC cutting technology.  Almost as importantly, the talent to make round-bottomed hullforms in metal is a disappearing art, and not many yacht building yards can do it.  To simplify construction and lower the cost to build, we made the MS 79 hullform triple chined.  We used three chines over one or two chines for the very good reason that the more chines you have, the closer you approximate a true round-bottom hullform.  Round-bottomed hullforms have a much easier motion--meaning lower rolling accelerations--than chined hullforms.  In addition, single or double chined hullforms don't have as much bottom volume for fuel storage, but the triple chined hullform actually has a little more fuel capacity than her smaller sister, in part because of her longer length, but also because the shape of the hull gives us the volume that we want.   Finally, on the earlier MS designs, we had to add some ballast to get them to sit down on their lines, and it is far better to simply make the structure heavier to get the weight and lower center of gravity that you like to have.  The added benefit is that the hull plating and structure below the waterline are all thicker and heavier, which makes the hull all that much more indestructible against grounding.   The renderings below are from the Rhino surface model.                     PARTICULARS Loa                                                           78’ 6” Lwl                                                            67’ 10-7/8” B                                                               22’ 0” hull 23’ 4” rubrails D at design waterline (Dwl)                     7’ 6” Displ.                                                 346,000 lbs. at Dwl Block Coefficient                                    0.46 Prismatic Coefficient                             0.60 Lbs./inch immersion                            6,480 lbs/in Displ./Length ratio                                  493 mid-cruise displ. A/B area ratio                                         2.31 Installed power                                       2 x Cummins 8.3 liter diesel, 350 HP @ 2500 RPM Speed                                                     11.0 kts, max., 9.0 kts, ave. cruise, 8.0 kts long cruise Range                                                   4,500 miles @ 8 knots (approx.) Fuel capacity                                       6,656 gal Water capacity                                       444 gal Black water & gray water capacity      359 gal each                Specifications subject to change   HULLFORM The hull is a heavy displacement type with a bulbous bow and cruiser stern. Long range cruising speed is 8 knots (anticipated range 4,500 miles) with a maximum speed of 11.0 knots.  The hullform is designed for generous interior volume with standing headroom in the engine room. The bulb shape is a Nabla-style bulb as on all the other MS motoryachts.  It is characterized by being V-shaped on its bottom and flatly rounded on its top.  The V-shaped bottom cleaves the on-coming waves without slamming, and then as the bow pulls up on the return motion, the higher drag of the rounded top of the bulb slows the bow's lift.  The resulting difference in speed between the bow sinking and returning is the damping effect of the bulb.  Pitching motion bleeds out quickly, making for a very comfortable ride.  Bulb proportions are critically important.  A bulbous bow is designed primarily to reduce the wave-making resistance of the hullform which means you can reach the design speed with less horsepower. Resistance is reduced because the bulb produces a wave that is opposite to the normal bow wave. ACCOMMODATIONS General. The Moloka'i Strait 79 is a four-deck boat with fly bridge, pilot deck, main deck, and below-deck accommodations. ‘Tween deck spacing is 7’ 6” for generous headroom throughout which leaves sufficient space for easy installation of plumbing, electrical, and HVAC services. Five watertight bulkheads divide the hull into 6 watertight compartments: anchor locker, crew cabin, guest cabin, master stateroom, engine room, and lazarette. Below deck.  The fore peak houses twin anchor lockers, and the 16” diameter Naiad bow thruster is installed in the bulb. The anchors and Nick Jackson 2500-lb. boat crane are mounted on a peak deck over the anchor lockers.  A scuttle immediately behind the peak deck and under the crane provides private access to the guest/crew suite at the forward end of the accommodation. Going down the scuttle, at the bottom of the ladder, is the kitchenette that is fitted with two-burner stove, microwave, sink, and refrigerator.  Access through the fore peak bulkhead is by two watertight hatches, one each into either side of the anchor locker.  The bulb is open to the space underneath the crew cabin sole.The crew suite is separate from the rest of the guest and owner accommodation and incorporates a dinette, and queen berth cabin, and kitchenette and head with double sinks and shower to port. Going through the watertight bulkhead door and stepping down to the next lower level is the guest space with two cabins, one each port and starboard.  The larger cabin to starboard has a queen-size double bed and ensuite head.  The smaller cabin to port has over/under twin berths and an ensuite head.  This is a great boat to be owned by Grandpa and Grandma, so that their children may have their own suite to starboard, and the grandkids have their cabin to port.  Just aft of the cabins are a laundry and the main stairway to the main deck to starboard. Aft of the stairs is a watertight door to the master stateroom, a suite occupying the full hull width.  Fitted with a king-size double bed, it has generous closet space, a large ensuite head with Jacuzzi tub, and a complete entertainment center.  Next to the entertainment center to starboard is the vestibule into the engine room.  Fitted with doors on the forward and aft bulkheads, noise is well contained, making the master stateroom particularly quiet.The main engines have generous service room between them, and they have dry exhaust routed up the port and starboard funnels. The 32 KW main generator and the smaller 16 KW light-duty generator are mounted atop the fuel day tanks.  Each is equipped with wet exhaust. A workbench is located aft of the port main engine directly in front of the ladder going up to the main deck.  This is the primary engine room access.  Another watertight access hatch is provided through the aft engine room bulkhead into the lazarette. Main deck.  The main saloon has a semi-circular settee and table with two chairs situated to port.  On centerline forward is the entertainment center.  Access to the cockpit aft is to starboard on the aft bulkhead.  Funnels are port and starboard.  All of this space is carpeted.Forward of the main saloon is the main entrance and stairway on starboard with the dining are to port.  A day head is just forward of the starboard funnel.  Stairs lead down to below-deck spaces and up to the pilot house.  The galley is forward with portlights looking out onto the fore deck.  We like to call this the chef's pilot house, which is quite what it looks like.  The galley is all-electric with 4-burner range/oven, large refrigerator and freezer, double sink, dishwasher, and trash compactor. On the aft side of the galley counter is a 3-seat snack bar. The fore deck is large enough to house an 18’ runabout to port and other toys such as a smaller RIB or jet skis to starboard.  On centerline is a ladder that leads up to the Portuguese Walk around the pilot house.  Going forward on the main deck are steps up to the peak deck for access to the anchor windlasses.  The scuttle to the crew's quarters is just aft and starboard of the deck crane. Pilot deck.  The wrap-around Portuguese walk leads to entrances into the pilot house port and starboard.  Bridge wings extend the view out over the side of the vessel.  A large console includes the ship’s primary helm, chart table, and electrical panels for AC and DC service.  Twin Stidd helm chairs provide considerable comfort and visibility for two on watch through five large front windows.  An L-shaped settee surrounds the port aft corner of the helm area, and the stairway leads down to the main deck.  A lounge faces aft on the starboard side.  This space could also be configured as a separate watch cabin.  In the port aft corner is a half bath for the crew on watch and guests. Going through the doorway in the lounge leads to the pilot deck aft where lounge chairs may be placed.  The liferaft is located at the aft end of the deck on centerline.  The stairway to the fly bridge is just to starboard of the exit door. Fly bridge.  The large fly bridge is equipped with a secondary helm and two helm chairs. Complete controls for the main engines and bow thruster are situated on centerline. To port and aft is a large L-shaped settee with a table.  Outside galley facilities with a barbeque, sink, and small refrigerator are on the starboard console.  A bimini top can cover most of the fly bridge area if desired.The mast is built onto an arch between the funnels and can be customized to the owner’s preference for electronics.  The funnels hold the main engine exhausts and allow passage for other hotel mechanical and electrical services. Power.  The Moloka'i Strait 79 is powered with twin Cummins 6CTA8.3M (350C), in-line 6-cylinder, 8.3 liter, marine diesel engines turning at 2,500 RPM through Twin Disc gears at 2.5/1 reduction.  Caterpillar is reworking their engine line, discontinuing some models and bringing new ones on line.  We anticipate that their new C-9, 9 liter marine diesel will be a good fit.  The NiBrAl 4-blade propellers are 35” diameter x 21" pitch on 3” diameter Aquamet 22 stainless steel shafts running through protective skegs that also support the twin double-plate rudders. Generator power will be by the two gensets, the larger one a 32 KW Northern Lights generator for 110 VAC, 60 Hz main house service. The smaller one will be a 16 KW Northern Lights generator for light-duty service. Tanks. The main fuel storage tanks are located in the hull bottom with a total capacity of 5,404 gallons.  Two day tanks of 626 gallons each in the engine room brings the total fuel capacity to 6,656 gallons.  Fresh water, gray water, and black water tanks are built into the double bottom structure forward under the crew's quarters.  Total fresh water capacity is 444 gallons, and a 600 gal/day water maker is also provided.  Gray water and black water tanks are each 359 gallons. METALS AND STRUCTURE The hull is designed for steel construction, framed longitudinally, onto which is built an aluminum deck house.  The two metals are connected by a Detacouple, which is an aluminum/steel strip that is explosively clad together, much like how our dimes and quarters are made.  Detacouple was invented by DuPont over 30 years ago, and is now made by Dynamic Materials Corporation.  The steel side of the strip is welded to the main deck, and the deck house is welded to the aluminum side of the strip.The hull, main deck, and bulkhead plating is ¼” thick A36 marine grade mild steel.  The main deck and the bulkheads are framed on 16½” centers, with the main deck longitudinal frames being steel flatbar, and those for the watertight bulkheads being angle bar.  The hull longitudinal frames are NC-cut steel flats spaced on 17.5” centers.  Hull and deck longitudinal frames are supported by NC-cut transverse ring frames spaced on 36” centers and fitted with flatbar T-flanges.  Bottom plating is 5/16" thick, and the keel side plates are 1/2" thick.  The bar keel is 12" wide and 10" thick, which provides the bulk of the ballast weight to the hull. The deck house is also longitudinally framed with transverse web frames on the same frame spacing as the hull.  All web frames and bulkheads are NC cut, longitudinal frames and other girders are flatbar and structural shapes.  Plating is ¼” thick 5083 aluminum, and all structural shapes are 6061 aluminum. Naval architect Eric Sponberg wrote a design review for the Moloka'i Strait motoryachts for Professional Boatbuilder magazine that appears in the current issue,  #114, August/September 2008, page 20.  You can access it by clicking here.  Go to the Tools bar at the top of the page to view the Contents, and go to Departments--Design Brief.For sales information, you can go online to Moloka'i Strait Marine at http://www.molokaistrait.com.
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