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The Aluminum or GRP Fast Power Catamaran

90' Tunnel CAT

90' Tunnel CAT - Click for Larger Image
Larger Aft Perspective | Forward Perspective | Aft Perspective

Copyright 2007 Michael Kasten

General Concept

This type of power catamaran is very much like a mono-hull with a 'tunnel' between the two halves of the hull. This configuration provides an easy motion and eliminates wake interference between the hulls.

The Tunnel CAT type shown here has often been outfitted with hydrofoils in between the hulls. Of course this type of craft can be driven at planing speeds without the foils, however with the foils and with approximately 25% more horsepower, the speed potential is almost double - an extremely rare case of getting something for nothing...!

The hydrofoils work well in rough water because the foils lift the hull nearly halfway out of the water. Being between the hulls, the foils are well protected. These are 'sub-surface' foil types, which makes them self-regulating. In other words they do not need to be dynamically articulated for the purpose of attitude or trim control. If desired, the aft foil can be arranged to articulate to various 'set' positions, allowing corrections for variations in vessel loading - say for widely varying fuel loads, etc.

This configuration is very fast. Being foil borne allows an extended daily range of operation, allowing a wider variety of day trips, and much quicker voyages. With only approximately 25% more power being used, but roughly 50% more speed, the range under power at top speed with a given fuel load is also extended considerably.

The model shown here is 90' overall length. This type can be designed at nearly any length desired.

Although this configuration is ordinarily intended for planing performance, long range cruising is also a possibility at slower speeds. For top speed - especially with foils - either water jets or surface piercing drives would be ideal. For slower speeds and long distance voyaging, immersed propellers would provide the most efficiency.


These vessel types must be kept relatively light in weight. Thus steel is probably not a viable option for top performance. Aluminum would therefore be ideal, as would GRP.

For a vessel built of fiberglass, many builders have taken advantage of the option to create a plug (male) or mould (female) directly from the computer generated model using a large 5-axis router. This eliminates the complex and labor intensive mould-building step, entirely eliminates lofting, reduces shop space requirements and builder lead-in time - ultimately saving the builder's labor and the customer's overall boat cost.

In aluminum, of course NC cutting is the ideal approach, yielding extreme accuracy and fairness, combined with an enormous savings in hull fabrication labor.

Check out our CAD Design Process article for more information on these options...

Further Development

Our routine is to work with new designs on a custom basis, so we are able to develop a design such as this in just about any size or superstructure configuration. As a boat becomes larger, naturally there are a much greater variety of cabin arrangements possible. This is entirely up to one's preferences, with the result that the hull and superstructure will be given the best shape in order to fit the required accommodations.

In other words, a Power Cat of this type can be scaled as needed, or even adapted to a variety of other unusual applications. Check out the Nemo - Nautilus combination: A 70' Tunnel CAT is able to serve as the mother ship for an 80' Submersible! When mated, they act as one single ship. When deployed, the Sub and the mother ship are autonomous.

For more information, please inquire.