Long range expedition trawlers
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What are the design objectives of the SP60?


The intent of the SP60 design is a comfortable boat with traditional lines capable of long range ocean passages by two persons. The boat has a clean and simple layout with only the very necessary equipment so that it is economical to build and operate and easy to maintain by a couple. The design and construction considers that the owner will do all of the maintenance and repairs. Above all, the boat is strong and durable.


Why design and build a custom boat rather than buy a production model?


Production boats target the average boater but in fact, there are very few average days at sea. Many production boats have good features and some are well built but none incorporate all of the features of the SP60.


The SP60 is less costly than the typical production boat. The raw materials that make up a metal boat represent a small percentage of the total cost. What costs the most is equipment and labor. Every design decision that was made took into account construction man-hours and the selection of great equipment rather than a lot of it. For every design decision made the initial investment and the ongoing maintenance and upkeep were considered.


Who designed the SP60?


South Pass Yacht Company designed the profile, layout and general specifications of the SP60. The naval architecture, engineering, technical specifications and stability analysis is by Boksa Marine Design.


Is the SP60 designed and built to any standards?


Yes. The SP60 is designed and built in conformity with American Bureau of Shipping (ABS) Rules for Building and Classing Steel Vessels Under 90 meters in Length as well as ABS’ “Guide for Shipbuilding and Repair Quality Standards for Hull Structures During Construction”.


Stability Criteria conforms to International Maritime Organization (IMO) and the US Code of Federal Regulations (46 CFR), as used by the US Coast Guard.


What type of hull does the SP60 have?


The SP60 has a full displacement hull with a fully loaded displacement/length ratio (D/L) of 418. The intent of this hull design is the ability to carry provisions and supplies to live comfortably aboard for long range travel and so that all the machinery and equipment is located in places where it can be easily serviced. Every piece of machinery and equipment has great access to it. There is no need to be concerned about weight and what has to be left home. The overall length was held at 60 feet to moderate operating costs and accommodate the physical capability of an older couple to handle a large heavy boat.


What is the hull material and why was it selected?


The hull bottom plate is 5/16” steel and the hull sides are ¼” steel built around an extremely robust frame structure. Steel is very strong and provides protection from floating objects on long ocean passages as well as accidentally touching bottom. A steel hull is easily repaired all over the world.


Steel is a relatively easy material to build with. It is very economical for a boat in the 60 foot range. It costs less than aluminum. Steel is more noble than aluminum and is a better choice for hull material.


The weight down low does not negatively affect the stability. The distribution of weight on the perimeters of the hull away from the roll axis increases the roll moment of inertia which together with the well proportioned beam provide a well balanced hull form. Imagine the spinning ice skater pulling in his arms to spin faster and then extending his arms to stop the spin. A heavier boat with the weight distributed can be more comfortable than a light boat because of a slower motion.


The superstructure is lighter weight aluminum which lowers the center of gravity as compared to steel.


Does the SP60 have active stabilizers?


The SP60 does not have active stabilizers although it could if desired. It does have fixed bilge keels.  Bilge keels reduce the roll tendency but the main reason for fixed bilge keels is to support the boat upright when the tide is out so that the bottom can be cleaned, zinc replaced, thru-hulls cleaned and other bottom work performed without a haul-out.


Does the SP60 have a bulbous bow?


No. There are benefits of a bulbous bow on some boats in some conditions. The few conditions in which a bulbous bow would benefit the SP60 are outweighed by the many conditions in which it would not, and some conditions in which a bow bulb would be dangerous.


Benefits: Increased fuel economy on large vessels that operate at a constant high speed. It may reduce pitching motion heading into certain but not all size and shaped swells.


Negatives: At some speeds, below 6 knots for example, it increases drag because of the increased wetted surface area. On smaller vessels below 60 feet LWL it increases slamming of the bow in some wave and swell conditions. In following seas a bulb bow can be dangerous on vessels below 60 feet LWL because of the tendency to increase yaw which may lead to a broach. Finally, and the 275 pound centerline anchor could hit a protruding steel bow bulb when lowered and the chain could easily foul in shifting winds and current.


See Nordhavn website where they discuss extensive testing Nordhavn hulls with and without bulbous bows.  Keep in mind however that it is very difficult to bring real sea conditions of wind, waves, and swells into a testing tank.


Has the design undergone stability analysis?


Yes.  Both intact stability and damage stability analysis has been performed and the SP60 exceeds by a large margin the Stability Criteria established by the International Maritime Organization (IMO) and the US Code of Federal Regulations (46 CFR), as used by the US Coast Guard. There are six separate watertight compartments and the boat meets stability requirements with any one of the compartments flooded. There are also 10 separate fuel and water tanks all in double hull bottoms which if penetrated will not flood the boat.


In addition to the weigh distribution discussed above many other design features contribute to safety. The tanks are designed to minimize free surface effect. The SP60 has high freeboard that raises the deck edge emersion point.  The engine room and lazarette air intake vents, and tank vents (downflood points) are all located inboard and above the main deck. All doors, hatches, port lights and vents are watertight. The forward facing pilothouse windows have 3/4 inch glazing. The side windows are 1/2 inch. All hull portlights have 3/4 inch glazing and deadlight covers.


What kind of electrical system does the SP60 have?


The SP60 has a large 1500 amp capacity 24 VDC house battery bank with inverter based AC electrical system. The boat is capable of plugging into any international source of shore power through isolation transformers, yet it can be operated unteathered from shorepower indefinitely. Two high output alternators on the main engine, solar panels, and an AC generator are available for charging batteries away from shore power.


The main engine and the generator starters each have their own isolated battery banks. The navigation equipment is powered by a completely isolated 12 volt battery bank.


What is the main propulsion?


A Single Cummins QSL9 engine rated for heavy duty 330 HP at 1800 maximum RPM. A ZF gear is connected to an Aquadrive CV-joint and an Aquadrive thrust bearing. The propeller shaft is Aqualoy 22HS. The propeller is Nibral 35 inch skew Kaplan five blade inside a Kort type nozzle. The nozzle provides additional propulsion efficiency and also protects the propeller nicks and bumps. The single propeller is located behind a massive keel which gives it additional protection.


Top speed is 10.5 knots, range 1,800 nautical miles. Short range cruising speed is 9.75 knots, range 2,470 nautical miles. Long range cruising speed is 8.0 knots, range 4,458 nautical miles. Ranges are calculated using 98% of the fuel capacity with 10% reserve. Range does not consider generator use because the generator is unnecessary when under power.


What kind of steering does the SP60 have?


The heavy displacement of the SP60 together with a large fishtail rudder, a three inch diameter Aqualoy 22HS rudder stock and Kort type propeller nozzle raise the rudder torque requirements significantly above a typical 60 foot boat. The electro-hydraulic power steering system is commercial grade by Jastram. The steering system starts with two high displacement cylinders that require a high volume hydraulic pump. The primary hydraulic pump is an engine driven PTO pump. Back-up pump is a 24VDC continuous pump by Accu-steer. Steering is by full follow-up lever. In the event of a failure of the DCA control units or any of the electrical components of the steering system an isolated jog lever can directly control the solenoid flow valve. If all these systems fail there is a Jastram helm pump and 24” diameter steering wheel located near the cylinders. If the entire steering systems fail including the hydraulics everything can be disconnected and an emergency tiller fitted to the rudder stock through a deck plate and the boat can be steered manually from the aft deck.


It may be noted here that there is a bow thruster to aid in close quarters maneuvering.


What is the get home propulsion?


Any form of mechanical back-up propulsion can fail from electrical, mechanical, or fuel causes. The only reliable get home propulsion is wind. The boat has a mast and sails for get home propulsion.


What type of dinghy is carried and how is it handled?


The boat deck has ample area to carry most any type of dinghy, launch or aquatic vehicle up to about 15 feet in length. Shown on the layout drawings are a Catalina 14.2 Expo and a 10 foot AB aluminum hull rigid inflatable. A boom mounted electric winch is used for dinghy handling. A manual winch on the pilothouse roof can also be used for dinghy handling in case of a power failure.


The SP60 carries a six man life raft in case of a catastrophic emergency such as a fire or explosion but the Catalina 14.2 is the primary lifeboat. It has a roller furling main sail, outboard motor, boarding ladder, positive flotation and a large watertight compartment under the foredeck in which water, food and ditch items (radio, GPS, etc.) will be stored during ocean passages.


What other design features does the SP60 have that distinguishes it from others?


Large stand-up engine room and lazarette

Walk around main deck

No side panels or supports that restrict line (or fish) handling

Watertight doors port and starboard for access to the side decks from both the galley and the pilothouse

Large galley and saloon on the same level

Pilothouse separated from saloon/galley for nighttime piloting

Straight stairways for safety at sea

Extremely large anchor and robust anchoring system

No exterior wood


How is the exterior finished?


It is intentional that the SP60 looks more like a commercial vessel than a yacht. When traveling around the world it is best not to stand out and attract attention. The plating welds are not ground and the hull is not faired. This saves a tremendous amount of money in construction. The steel hull is painted with non-glossy commercial grade marine epoxy paint and is grey color. With this type of coating it is easy to touch-up the inevitable scratches and nicks as they occur.


The hull has two four inch diameter stainless steel half pipe rub rails welded to the hull plate where it rubs against other boats, docks, and pilings. These are mill finished and unpainted. The cap at the top of the bulwark is also heavy gauge stainless steel that is designed to protect the hull when springing off a piling.


The aluminum superstructure is unpainted. Aluminum does not need to be painted. This saves a lot of money initially during construction and obviously will not need to be repainted in the future which reduces ongoing maintenance costs. It makes cleaning and maintenance much easier.


Who is the builder?


The builder is Gulfstream Shipbuilding in Freeport, Florida. Gulfstream Shipbuilding has a long history and developed a great reputation building commercial vessels. Recently it has been building 200 foot aluminum offshore fast supply boats for the offshore oil industry.


Gulfstream management understands the vision of a strong boat with good looking but durable finishes. The equipment and systems are commercial grade.


Why build in the U.S.A.?


The SP60 is built in the U.S.A. for many reasons.  Primary among them are a desire to build close to home where travel, communications and supervision is easier. There is a high level confidence that ABS, USCG and ABYC standards are being met. It will cost a little more but the results are worth it.


Is this the perfect boat? 


No, there is no such thing as a perfect boat for all purposes and all tastes. One size or one design does not fit all. The SP60 fits the size and design objectives of anyone wanting to do long ocean passages in comfort with the capacity to carry a lot of weight. The SP60 is perfect for someone getting older and eventually slowing down and staying closer to home. It could be called your last boat.


Please take a look. It might be perfect for you. Contact us if you would like one of your own.


 Questions, comments, inquiries click here.