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.
Construction
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
please inquire.
