Seapiper Technical – Construction Notes



Our SeaPiper 35 Trawler was designed from the ground up as a completely new design in which we incorporated various great features, while ensuring full compliance with ABYC rules and USCG requirements.


The ballasted chine hull with the extremely low engine placement of Seapiper 35 offers great stability, resists rolling and has a very comfortable motion when underway. The roll period, center of gravity and metacentric height have been carefully chosen resulting in a very safe and comfortable vessel for its crew. The long box keel and large rudder ensure excellent directional stability.


The Seabright skiff inspired hull form on this trawler has limited transom immersion and enables great efficiency at hull speed up to about S/L 2.0. She will sip fuel doing 7 knots while allowing for speeds a little over 10 knots with the 85hp base engine. Important to note is the shallow prop shaft angle of only 1/2 degree in combination with the large prop diameter of 23 inches.

Simplicity and Access:

We believe that simple is better so we chose to limit on board systems to the essentials, but at the same time ensure that these systems are of the highest quality and easily maintainable. Everything is designed with this in mind: plumbing and wiring are straight forward with minimal connections for maximum reliability.

We also went out of our way to ensure great access to each part and every corner. The engine access is second to none for this size of trawler: great access from the front and the sides through the deck hatch, and from the interior engine hatch there is access behind the engine and access to the exhaust system and the water heater. All wiring and all plumbing is directly accessible or routed through conduit where it cannot be reached otherwise. Integral fuel tanks have access hatches for interior hull access.

Strength and structure:

The hull bottom is solid hand laid fiberglass that is mostly 1/2in (12mm) in laminate thickness below the waterline, and 3/8in (10mm) laminate thickness above the waterline which is cored with the superior Airex coring material. This hull structure is extremely strong, well insulated, and the Airex cored topsides offer superior stiffness and impact resistance. The structure is reinforced with strong 2-inch thick Nidacore sub floors and EIGHT very substantial transverse bulkheads, five of which are designed as watertight bulkheads. Longitudinally there are two full height bulkheads under the sole from the stern forward that offer tremendous additional stiffness to the structure.

The safety aspect of this compartmentalized structure cannot be overstated: without interfering with the interior layout it divides the boat into four completely watertight compartments, each of which can be flooded while keeping boat and crew safe. Each compartment also has its own automatic bilge pump.

The cast iron internal ballast set in resin adds to the impact strength of the hull: most of the hull bottom is more than 3 inches thick.


It is worth mentioning that everything engine related, including fuel tanks, fuel filters, cooling intake, and exhaust is all located in the watertight engine compartment.

All the (identical) port lights are rated CE class III, and are of the opening type. All window glass is laminated safety glass bonded in place and confirm to Lloyds requirements concerning thickness and size for offshore use. Note also that there are only two different window glass sizes installed in the boat.

Very FAST Self Draining Cockpits:

Seapiper has a large center cockpit and a substantial aft cockpit which need to self drain quickly. We incorporated an advanced draining system in the center cockpit, along with overflow scuppers that are built into the side doors. This cockpit if filled to the gunnel will drain in an unprecedented 10-12 seconds (!) The aft cockpit is also self draining, and when filled to the gunnel will completely drain in approximately 6 seconds.

Deck access:

We added two side entry doors for access to the water, as well as double opening stern doors onto the swim step. These doors will latch in the open and closed positions.

Doors and hatch seals:

All doors and hatches make use of extruded neoprene seals that will completely seal the exterior from the interior. The doors are installed using high grade composite sliding door hardware which completely eliminates corrosion and will enable smooth operation. All deck hatches use seals and have draining channels overboard.


SeaPiper uses hydraulic steering with an inside wheel and we offer the option of an outside steering wheel which allows for quick access to the wheel when in the cockpit and easy docking, even when single handed.

Ease of handling is also augmented by a large foil shaped rudder, which is protected by a rudder shoe.