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The Aluminum Trawler Yacht


Copyright 2000 - 2011 Michael Kasten

The 80' Motor Yacht NORTH COAST - Kasten Marine Design, Inc.
Outboard Profile | Inboard Profile & Lower Deck | Main Deck & Pilot House
Perspective Forward | Perspective Aft


The intent of this design has been to create a highly capable long range, comfortable, efficient and safe offshore motor yacht in aluminum. The lines of North Coast are designed to provide an easily driven hull for maximum efficiency and economy of operation. North Coast has been designed to comply with the stability criteria provided by the IMO (International Maritime Organization), including the IMO extended weather criteria.

Imperial Dimensions

Metric Dimensions

With a D/L of 304 at the Design WL, North Coast is of medium displacement. In use, displacement will vary from around 230,000# (104.3 metric tons) when lightly loaded, to a maximum capacity of 280,000# (127 metric tons) with tanks full, stores aboard for a full complement of guests, and the boat ready for a long passage.

Twin engines, twin propellers, twin skegs, and twin rudders are planned. This configuration provides an excellent level of redundancy, and also keeps the overall draft at a modest two meters.

Power Options

The North Coast was originally detailed for the use of conventional twin diesel engines coupled to a pair of V-drive gears. During 2008 we were asked to re-configure the North Coast to make use of a diesel-electric propulsion system designed and manufactured by Glacier Bay. These two powering options are described in brief as follows:

Conventional Diesel Propulsion Option

For this option, two fresh water cooled marine diesel propulsion engines will be provided. The propulsion engines are mounted reversed and make use of V-drives. Space around the engines is intended to be adequate to provide good access to all parts of the engines and gears.

Using a continuous duty Marine "A" rating, the requirement is for 300 to 325 hp each. Among the various engine choices, a few that have been considered are as follows:

Diesel-Electric Propulsion Option

For this option, two 320hp (238kw x 750v DC) Glacier Bay OSSA Powerlite electric motors will be provided. The electric motors are mounted to the shafts directly via Aqua-Drive CV joint / thrust bearing couplings.

The electric motors will be energized by three independent 200kW Glacier Bay OSSA Powerlite twin voltage (240v DC & 750v DC) generators. These three DC generators will also provide power for the on-board electrical demands.

Why DC...? One of the primary advantages with the use of DC generators is that they are able to operate at any rpm up to their maximum rating according to the electrical load being imposed. In other words, the generator(s) do not need to scream along at full rpm if there is only a light load being imposed.

A further advantage with DC generators is that all major equipment can be either 240v DC or 24v DC. Incidental AC loads are provided via inverters, directly energized by the battery bank. With a large battery bank in the electrical supply system, there are no "surge" loads imposed upon the generators - they are instead absorbed by the batteries... allowing the generators to be more modestly sized.

Shore Power: Yet another advantage of this system is that when the vessel is at the dock, shore power is fed directly to a twin voltage / twin frequency isolation transformer, then to twin voltage / twin frequency battery chargers, which energize the batteries, which in turn energize the onboard distribution panels, both AC and DC.

This has the multiple advantage of de-coupling the shore-side electric power from the on-board electric power, allowing full isolation for corrosion control, and also allows the vessel to be fully voltage and frequency agnostic with regard to shore power.

In other words, the vessel can plug into US 60hz 120v AC shore power, or EU 50hz 240v AC shore power, and it will make no difference to the onboard AC or DC systems, which are all either DC or are supplied by DC to AC inverters. All onboard AC equipment is 50hz 240v AC.

One might imagine that electric power on an aluminum boat is asking for trouble...! Not so... Despite the prevalence of improperly wired marina power systems and faulty wiring or incorrect wiring practices onboard other vessels which may end up in a nearby slip, by design in this case there is no connection whatever between the shore side AC power and the onboard AC system, nor to the onboard DC system.

Once the power is aboard we have the benefit of an extraordinarily well integrated electrical system design which assures that the onboard electrical system is entirely isolated from the hull, providing for a safe installation that also protects the vessel from the possibility of there being any onboard stray currents and consequent corrosion.

Equipment: Except for the generators and the high voltage DC panels and motor controls, all onboard electrical supply system components are Victron equipment, from shore power to battery charging, to the electrical distribution panels. Using this option, the Victron designed electrical supply system is fully integrated with the Glacier Bay designed propulsion system. In other words, this is a "whole vessel" approach which integrates propulsion, electrical power supply and electrical demand.


Using 20 hp/gal/hr as the specific fuel consumption for the conventional diesel engines or for the Glacier Bay generators, allowing for a 12% fuel reserve and a tank capacity of around 6,000 gallons total, range is approximately as follows:

The ideal long range cruising speed for this vessel is between 9 and 10 knots. Displacement hull speed is around 11.3 knots, depending on vessel loading.


North Coast has been designed in excess of the scantling requirements of the ABS Rules for Motor Pleasure Yachts. The hull, deck and house structures are Aluminum for the purpose of extreme ruggedness, ease of construction, long life, freedom from maintenance, and for its very favorable strength to weight ratio.

The cabin structures being substantial and fairly tall, aluminum provides light weight, a low center of gravity, and ample stability. A "double bottom" area below the lower cabins contains the vessel's tankage, and a mechanical alley down the center.

Interior materials have been chosen to be as light in weight as possible, while not being overly expensive to construct. Toward that end, wherever convenient for larger joinery panels in places where it will not increase the joinery labor to any appreciable degree, honeycomb panels (Nida-Core) have been specified.


With the exception of the mechanical spaces, the cabin structures provide a standing headroom of 6' - 8" (1.93 meters) throughout. The Pilot House deck is extended forward in order to enclose the Master Stateroom, creating a high bow profile. This permits the main deck accommodations to extend nearly the entire length of the ship. Below, the accommodations extend from the utility spaces aft, nearly to the bow.

Original Layout

In the following images we observe the layout given to the original North Coast design:

Inboard Profile & Lower Deck | Main Deck & Pilot House

New Layout

During 2007, along with introducing Diesel-Electric propulsion we were asked to re-design the interior. Our first task was on the lower deck to accommodate a large master suite where the original vessel had a large recreation room, and then to provide a large en-suite head and shower aft of that, where originally there was a big laundry room.

On the main deck, the cabin sides have been moved outward, eliminating the side decks. This allows the whole interior aft of the forward stateroom to become a large open space with the galley forward, dining amidships, and the saloon aft. On the pilot house deck, the changes are more modest, adding a forward-facing large desk just aft of the spiral stairway.

The following images show the new North Coast interior layout:

Interior Profile | Lower Deck Plan | Main Deck Plan | Bridge Deck Plan


For an extended family, or for a couple who enjoy entertaining, one could hardly do better than North Coast in terms of getting the most vessel within the least overall vessel size. Aboard either version of the North Coast one can have a comfortable life afloat, whether in port or on the open sea. This has been most excellently achieved with a styling that is sleek and up to date among modern trawler yachts.

North Coast will stand the test of time in terms of appearance, both inside and out, as well as in terms of maintenance and longevity of structure.

The best way to check out the North Coast design is via the Study Plans, or better yet via much more complete Estimating Plans. For more information about North Coast or any of our other large motor yacht designs please inquire.

The 50' Motor Yacht NORTH COAST The 50' Trawler Yacht NORTH COAST
Click the above images for a larger view...!