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Exterior Profile    |     Interior Profile & Arrangement
Hull Model Perspective Above    |     Hull Model Perspective Aft

General Concept

The name "Twee Schoenen" is Dutch for "Two Shoes" which we think captures both the general look of the boat (Dutch) and the twin-hull type (Two Shoes).  Aesthetically, the boat would be very much at home on a Dutch canal...

The 35 foot aluminum "Twee Schoenen 35" is a light displacement power catamaran, having a "tunnel-hull" and modest beam. This design was developed in order to provide a stable platform capable of high speed, and also capable of long range at lower speeds.  Design waterline length is 32.8 feet. Moulded beam is 14 feet.  Displacement light is around 24,000 lb. and loaded is around 28,000 lb.  Draft is 2.6 feet from the DWL. 

Twin engines have been specified as is usual for a power catamaran.  This provides redundancy of get-home power and shallow draft for cruising thin water such as is found in the Bahamas.  The twin hulls also allow beaching the boat and still remaining upright when the tide goes out.

Below, the interior begins forward with a large dinette table surrounded by a wrap-around seat.  Aft of that is a large desk to port and a galley to starb'd.  Aft to port is a large head compartment.  Aft to starb'd is a double berth, enclosed for privacy. 

Within the pilot house is a large chart desk to starb'd and a double seat helm station to port.  Access to the engine space is provided via two hatches, one below the pilot seat, and the other below the chart desk.

Aft of the pilot house is a "well-deck" or cockpit, containing seating, and a secure coaming all around.

The long forward cabin has a downward sloping curve in order to maximize the headroom in the galley / dinette area, while still allowing the maximum view ahead from within the pilot house.  While this may seem somewhat unusual visually, on review of older power vessels from the 20's through the 60's there are numerous examples of similar roof lines. 

In order to avoid the usual "flat" and somewhat dull sheer line often found on similar power craft, the hulls were given a pronounced sheer line.  This allows a substantial bulwark forward for protection of the cabin, and for security while walking around the side and forward decks.

Just outside the forward end of the cabin is a forward facing seat.  Within the seat are the two anchor winches and storage for lines and other gear.

A 10' aluminum sailing pram is stowed above the pilot house, lifted in place by the mast and boom.

 

Hull Design Notes

This hull type is suited to sizes ranging from around 30 feet to around 60 feet.   The hull form is modeled after similar types that are used in a variety of configurations for sport fishing; as landing craft / small ferries; and as rescue boats.  

Construction is in all aluminum alloy for the best combination of lightness and strength.  GRP construction would of course also be possible, as would plywood construction.

The overall approach to hull form has been to essentially take a successful "mono-hull" type, cut it in half lengthwise, move the two halves apart and plate the inner face using flat panels, with a radius at the top in order to create the tunnel.  This is both practical for the sake of ease of construction, and the resulting vessel is fast and seaworthy.

 

Powering Options...!

Here are a few of the powering options we considered for the Twee Schoenen.  The variety of engines is more an illustration of the extreme adaptability of the design....! 

We considered the use of passive near-surface hydrofoils.  These would span between the hull halves and would raise the hull out of the water about half way at speed, so the vessel is not entirely foil borne and does not need active controls on the foils.  Being of the near-surface type, the foils are self-regulating.  The aft foil is given an adjuster, which can be varied under way in order to make trim corrections as fuel is used.

For this design the foils require over 275hp.  They nearly double the potential speed, but require only a relatively modest power increase.

We originally planned for Yanmar JH4TE 125hp engines - which we calculated were good for around 15 to 17 knots, depending on the load.  The owner wanted to check out higher power for charter use in order to get a larger circle of operations within a given time period, so we considered the following power options:

* Yanmar 6LP - DTP 260 p @ 3800rpm
* Yanmar 6LYA - STP 370hp @ 3300rpm
* Volvo 6-310 - 310hp @ 3500 rpm  

Plus, we looked at a variety of 8 degree down-angle gear choices, including:

* Twin Disc MG-5050A
* ZF IRM-220A

Other possible gears (choice depends on engine power rating):

* Twin Disc MG-5011A
* ZF HSW-630A

Among the above, the Volvo 6-310 - 310hp combined with the Twin Disc MG-5050-A would have been the best choice if it had been chosen to use foils.  Among the above engine choices, the Yanmar 6LP would not have had enough power to fully use the speed potential of the foils, and the 6LYA had much more power than necessary.  Plus, space in the engine rooms is at a premium...! 

The owner decided to use the Steyr - 230hp @ 2,200rpm supplied with a ZF 220-A down-angle gear, and no foils. This is a fine combination, good for 20 - 23 knots depending on the load. 

The Steyr engine is made in Austria.  It is very compact, has an excellent warranty even for commercial use, produces high power and is not too heavy.  This engine is only slightly larger than the originally planned 4 cylinder Yanmar.

We then ran the design through Transport Canada, and with a few tweaks here and there plus a new interior configuration it qualifies for use as a charter vessel in Canada.  You can see the new layout in the following images... strictly for charters...! 

Chartering Layout Profile   |   Chartering Layout Plan View

In the Chartering Layout, the galley is aft to starb'd opposite the head.  The whole forward area is for seating.  Of course the forward area could be differently configured, but that too shows the flexibility of the design...

About the Charters...

The Twee Schoenen is to begin operations in 2007 from the Port of Campbell River British Columbia. B.C.  The operators are Boat Tours LTD., a Canadian Corporation.  The vessel will fly the Canadian flag as a fully compliant commercial passenger carrying vessel pursuant to all Canadian Coast Guard Regulations. 

The owner, Monroe Woollard of Hawaii, wanted a vessel with a tunnel and asymmetric hulls.  In order to develop the design we followed in the tradition established for the type in England and in South Africa.  The specific benefits of this kind of hull are to help eliminate wave pounding, to carve turns, to eliminate wake interference between the hulls, and to be efficient at speed using modest power.

In use as a charter vessel for eco-tours, the vessel will carry kayaks, provide easy access for scuba divers, and afford cozy and warm accomodations for twelve guests under the eye of a highly qualified Native American guide / Ship Captain.  Please check out their Web Site for more information about these charters.

More Info...

As the length of this vessel type is increased to around 40' or more, the design begins to really show its potential. You can see other prototypes of this kind of vessel on our Power Prototypes web page, which range in size from 50' to 120'. If you would like more information about these vessels, please please inquire.