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The 36' Fast Aluminum Trawler Yacht

"Wave Runner"

36' Fast Trawler Yacht - WAVERUNNER - Kasten Marine Design, Inc.
Larger Aft Perspective | Larger Forward Perspective | Proposed Interior Arrangement

Copyright 2001 Michael Kasten - Updated January 2011

General Concept

The 36 foot all aluminum "Wave Runner" has a fast semi-displacement hull form. The long fine run and 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.

Average waterline length is 34.5 feet. Beam is 10 feet. Displacement will be around 16,000 lb. light and around 21,000 lb. loaded. Draft is mainly a matter of deciding water depth limitations versus the preferred propeller diameter for best propulsive efficiency. Having chosen an optimum propeller diameter, draft is around 4.25 feet.

If it were desired to limit draft, say for creating a "Trailerable Trawler" it would be most effectively achieved by the use of a "tunnel" stern. Given a specific requirement, design issues such as these can usually be accommodated.
 

Power & Range

The displacement to length ratio of the 36' Wave Runner is quite light (D/L is around 177 light). This allows a "displacement hull speed" of close to 10 knots!

At a more typical voyaging speed of around 6.8 knots, with 350 US gallons of fuel, range is calculated to be over 3,100 NM, allowing for a 12% reserve. At this speed, power use will only be around 15 hp...! At 9.7 knots, this vessel's "hull speed," range would be something like 1,000 NM assuming an "average" load condition. At this speed, only around 65 hp will be used.

Of course faster speeds are possible with this type of semi-displacement hull form. By supplying more power, a much higher speed can be obtained. Of course range will be reduced exponentially at higher speeds.

Depending on top speed desired, a wide range of possible powering options are available. For example, using a 4 cylinder Yanmar 4LH-STE having a continuous rating of 190 hp at 3,100 rpm, a speed of around 16 knots is attainable.

Another 4 cylinder engine that can provide slightly more push is the Cummins 4B-250, rated for 200 hp continuous at 2,800 rpm. This combination would provide approximately 16.5 knots in the fully loaded condition, and around 19 knots when lightly loaded.

In order to take advantage of such a wide range of power for these differing purposes a Controllable Pitch Propeller would be the ideal choice, allowing efficient powering at displacement speeds for voyaging, and at semi-planing speeds for quick trips...

Although it is possible to apply sufficient power for true planing, if that were desired as the primary operation regime, the hull form would ideally be modified in order to provide a flatter run (i.e. buttock lines of less than 2 degrees to the WL).
 

Interior

The Proposed Interior Arrangement is planned to be the same as that of the Greatheart 36. Since the Wave Runner also has a large flush fore deck, there is an enormous amount of space in the forward cabins. Right forward is the head, with a hatch above. Just aft of that is a settee on both sides with a table between. The settee seats allow dual use, and provide two guest berths. Just aft of the settee is a large galley spanning both sides of the little ship.

If you curious enough to want to get a sense of how much space is conferred by this type of fore deck, you can do the following little experiment. Take a tape measure and run it out to 9.5 feet. With one end behind your shoulder and viewing the far end of the tape... that's how much interior beam is available, full width, and full height...!

Aft of the galley and up through the companionway is the Pilot House, where there are seats to accommodate pilot and mate. Aft of the pilot house is the private owner's cabin, having a true "double bed" size berth on center.

Best of all, on deck there is the chance for an aft facing seat right above the after cabin. Perfect for fishing or just for watching the wake in the sunset.
 

Design Summary

The intent of this design has been to fit the maximum accommodations into a fast cruiser of 36 feet LOA. The requirement for excellent sea keeping has encouraged keeping the cabins low. The low profile serves the vessel well. For example, the height to the top of the Pilot House is right around 9 feet off the water, which opens up access to the canals in France and most of continental Europe.

Additionally, with a beam of less than 10 feet, and a "dry" weight of under 15k lbs, the boat can easily be trailered from one cruising site to another.

Quite a good little ship....!

36' Fast Trawler Yacht - WAVERUNNER - Kasten Marine Design, Inc.
Larger Aft Perspective | Larger Forward Perspective | Proposed Interior Arrangement