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The 48' Fast Aluminum Trawler Yacht

'Coast Runner'

48' Fast Trawler - Coast Runner - Kasten Marine Design, Inc.

Copyright 2003 Michael Kasten

General Concept

The aluminum Coast Runner 48 shown here has resulted from a blend of two other designs: The 40' Coaster contributed the house structures, and the 48' Rhumb Runner has contributed the fast semi-displacement hull form.

Two additional images linked here illustrate the same cabin and interior layout configuration, but with a walkaround exterior "Portuguese Bridge forward of the pilot house and slightly different styling to the aft cabin eaves and "wing plates" as well as the pilot house brow... See the Forward Wireframe and the Aft Wireframe views.


The long fine run combined with light displacement will yield an excellent combination of speed and economy. Relatively short overhangs maximize WL length and therefore vessel speed and accommodation space below.

As with the 48' Rhumb Runner, the 48' Coast Runner has an average waterline length of 46.75 feet. Beam is 13.5 feet. Displacement is around 32,000 lb. light and around 42,000 lb. loaded. Draft is 4.5 feet light, and 5 feet loaded.

The displacement to length ratio varies from around 142 to 192 depending on the load case, i.e. quite light... The result is that displacement "hull speed" will be right around 12 knots. In order to achieve this relatively high "displacement" speed, the power required will be around 160 hp, assuming an average load condition. At 12 knots, with 600 US gallons of fuel, range will be something like 720 NM in the average load condition, assuming a 12% fuel reserve.

At a more typical "voyaging" speed of 8 knots, still with 600 US gallons of fuel, range is calculated to be over 2,600 NM, assuming the same 12% reserve.

For higher semi-displacement speeds one could easily make use of 450 or more hp, which will yield vessel speeds in excess of 20 knots (depending of course on fuel load and other vessel loads). The top speed achieved with greater horsepower will be more or less in proportion to the power applied. As always, range will be exponentially reduced at higher speeds.

Although it is possible to apply sufficient power for true high speed planing, if that were the goal the hull form should be changed. In other words, for true fast planing performance, the hull should be given a run that is flatter yet, along with a wider transom...


Beginning forward, the layout below contains a large owner stateroom with head and shower to port, and a second stateroom to starb'd.

The Pilot House is quite spacious, with a nav station and piloting area forward, and a bench seat to starb'd aft. Below the Pilot House sole are the engine and tanks.

Aft, there is a galley to starb'd very much as with the 40' Coaster. In this vessel however the saloon is larger. Along with the dinette seating, there is ample lounging space within the saloon.

The aft deck is also more spacious than that of the 40' Coaster, allowing a seating area aft, located out of the normal traffic pattern.

Design Summary

As with the 48' Rhumb Runner and the 49' Ocean Express, the intent of the 48' Coast Runner described here has been to fit the maximum accommodations into a fast cruiser under 50 feet LOA.

Height to the top of the Pilot House is low enough to allow access to most of the canals in France and the rest of Europe.

The 48' Coast Runner is so-far a preliminary design, having been modeled by computer, and the hydrostatics calculated. The interior has been sketched, but remains to be detailed into a completed set of Building Plans. For further information, please inquire.