Hydrofoil_home

hydrofoil F1
Technical Information
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In recent years, this problem has been solved by placing flaps at the back edge of each hydrofoil (Hook method).

The flaps can be adjusted using mechanical controls (see Fig. 1), thereby increasing the lift as required.
This works quite well when the water is relatively calm, but stops working when the water gets rougher, as the flaps tend to start fluttering. Also, with this system, only lift can be controlled, but not downforce (negative lift).

Download Fig.1 (PDF)
Mechanical hydrofoil control (Hook method)

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Digital hydrofoil control:*)

Catlift, a Munich-based company, has been building hydrofoil control systems for the past 20 years. The company has developed an elegant solution which uses a computer to automatically control the complete hydrofoil, as opposed to just controlling flaps on the hydrofoil (Hook method). The computer controls powerful and responsive stepper motors which raise and lower the complete hydrofoil (Fig. 2).

The efficiency of this type of hydrofoil is much higher, as only minor hydrofoil control movements are required. Also, by controlling the hydrofoils in this way, the computer can filter out the movements caused by the waves. The result is impressive: the new hydrofoil F1 flys much faster than any comparable catamaran, yet with no sacrifice of safety, comfort and ease of use.

Download Fig.2 (PDF)
Digitally controlled hydrofoil

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Altitude control

In the new hydrofoil F1 the altitude (distance above the water's surface) is controlled using a rod with an integrated angle sensor. The sensor transmits the current distance to the computer. Using custom software* developed by Christian Enzmann, the computer filters out the motion caused by the waves and sends the required control signal to the stepper motor of the hydrofoil control system to stabilise the boat.
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The "luff push" effect

Both side daggerboards with the controllable hydrofoil on the bottom end (so-called T-foils) are not actually vertical, but are splayed out sidewards. In this way, not only does the leeward hydrofoil get the required lift to reach the right altitude, but also experiences a force toward the windward side, thereby reducing the windward drift by more than 50% (the "luff push" effect).

As the altitude increases, the windward hydrofoil is automatically tilted downdard, thereby producing downforce. The consequence of this is, whilst the boat is close-hauling to the wind, a substantial amount of righting moment is available (in relation to the weight of the boat, more than with any other technology). By setting the windward hydrofoil at a negative incidence, besides the expected downforce pointing vertically down, there is also a downforce pointing in the windward direction. For the "Enzmann-hydro", this means that despite the higher speed, there is less drift experienced whilst beating to windward.

Download Fig.3 (PDF)
The "luff-push" effect

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Sailing faster than the wind

As with ice yachting, flying on hydrofoils means the boat is sailing faster by using its own headwind. Here's how it works: as the speed of the boat increases, so too does the headwind. This headwind vector is added to the true wind vector, thereby turning the "apparent" wind around so that it is like a fast wind coming diagonally from the front. It's this apparent wind which can drive the boat faster, as long as the drag force of the water can be reduced by sailing on hydrofoils.

Download Fig.4 (PDF)
Sailing using the headwind

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Aerodynamic drag

Every cyclist knows that a headwind uses up a lot of energy!
With this in mind, a lot of work has gone into making the
hydrofoil F1 aerodynamic as possible for wind speeds of 100 km/h or higher. All parts of the boat were painstakingly designed and tested to minimise aerodynamic drag. Not only does this work really well, it also looks great. You can "see" the aerodynamic nature of the boat.

Download Picture (300dpi)
Aerodynamic looks well

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The duo cockpit

You can sail alone in the hydrofoil F1 or with another person on board. All instrumentation required to "fly" is in the dashboard of the rear cockpit. Behind the rear cockpit, there is a drawer which contains the computer and the lithium ion rechargeable battery. The battery and the battery charger are standard off-the-shelf models which are also used for e-bikes.

Aerodynamic made from carbon epoxy sandwich structure, white outside

Aerodynamic made from carbon epoxy sandwich structure, white outside
Plenty of dry storage space in the bow and stern
2 removable reclining seats
Double main sheet rigging (so you can sail whilst in the front or rear cockpit)
2 optional safety belts

Download Picture (300dpi)

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Steering the boat

The boat can be steered using two adjustable foot pedals in each cockpit. The foot pedals are connected to the aft rudder using carbon-fibre push rods. In deep water, the rudder blade is pushed down and secured in place.

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"flight-information" on a touch-screen

Touch-screen display showing control information:

Hydrofoil angle-of-attack
GPS co-ordinates
GPS-based speed
Battery charge level (4 to 6 hours "flight" time,
depending on the wind)
Main On/Off switch

For charging, and to deter thieves, or the complete dashboard including computer and battery can be removed from the boat.

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The required water depth ?

A hydrofoil F1 also sails like any other catamaran. The boat is launched from the beach, with the hydrofoils swivelled upwards and the rudder blade pulled up. The boat is sailed into deeper water, the hydrofoils are swivelled downwards and locked in place. The rudder-hydrofoil is pushed downwards. Now the boat is "ready of take-off".

Safety

Thehydrofoil F1 offers additional safety, for example, a sudden gust of wind won't capsize the boat, something which could indeed happen with a traditional catamaran. When the boat lands on the beach, the side daggerboards are again swivelled into an upright position. They are stored beside the sail in the bag. While the hydrofoils are in the water, the bag is stored in the cockpit.

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STBD is down, port and rudderblade is upwards

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Steering the hydrofoils

Under water, the hydrofoils are controlled using push-rods which are in turn driven by stepper motors with their own controller. Over a CAN-Bus data-network, all three motors are connected to each other and to the central computer.

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Is it difficult to sail the hydrofoil F1?
No, on the contrary ! The high capsize resistance of the hydrofoil F1makes it very easy to sail.
This makes it even easier for people learning how to sail.

The wing spar
is mounted on the front edge with a hook -like nose and attached to the cockpit using two screws.
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The rigging

Consists of a carbon-fibre mast and a laminated sailcloth. A fixed-wing was intentionally not designed into the boat, as it is extremely cumbersome for everyday use. Every evening, it must be taken down, to avoid the boat sailing off on its own during the night. This is easy to observe during the Americas cup.

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The catamaran hulls

Are made of carbon sandwich material (the weight is only 10.2 kg !) are connected to the platform using the force of friction, and each hull is fixed to the platform using just 1 screw. This means that the complete catamaran can be assembled using just 4 screws, which is what the boat can be assembled so quickly.

*) Patents pend. Reg. Design Reg. Trademark