E-Foil: Take off at the touch of a button – putting the Duotone Foil Assist to the test

With the Foil Assist, manufacturer Duotone is jumping on the e-foil bandwagon. Unlike traditional e-foils, this system carries the battery on the rider’s body, so a specialised board is not required. This makes the system significantly lighter than traditional e-foil boards. The price for the set is 4,799 euros. The system can be further upgraded with a carbon mast (D/Lab Upgrade) (5,999 euros). A more powerful propeller is also available.

On Land – Contents of the package

The package includes the Foil-Assist mast with the drive unit, which is then secured to the battery pack via a cable using a sturdy twist lock. To ensure that the pull does not strain the power cable in the event of a fall, a stretchy leash is integrated into the cable, which is also clipped onto the battery pack’s belt. The foil mast is mounted in the foil box as usual. The wing of your choice is then fitted to this; we have tested the system with two Crest foils (1050 & 925 cm²). The system itself is therefore compatible with various Duotone foils and boards. To prevent the power cable from getting near the propeller, a small plastic plate is screwed into the box behind the foil mast, ensuring the cable is neatly routed towards the rear. The leash and power cable are also secured to the top of the board to prevent the cable from coming into contact with the propeller.

To start the system, first insert the two batteries into the battery box. Pressing the start buttons simultaneously puts them into standby mode. Then switch on the remote control; it will pair automatically with the e-foil motor. The remote control can be worn on the wrist like a watch; the battery levels of both the motor and the remote control are visible at all times. The remote control is connected to a small finger ring, which is slipped onto the index finger, for example. This is used later to adjust the drive’s speed setting. Finally, fasten the belt with the battery to your body and you’re ready to head out onto the water.

On the water

We tested the system in very gusty conditions with wind speeds of between 4 and 14 knots. When launching, you should ensure that the leash is routed neatly upwards behind the tail. Once on board, the propulsion is activated by double-clicking the finger ring; in the first stage, it engages a slow, moderate forward thrust. However, this thrust is already sufficient to stabilise the board even in marginal wind conditions. You can now gradually increase your speed, taking care to keep the board flat by applying controlled pressure to your front leg and building up sufficient speed first. If you take off too early, the propeller will come out of the water and you’ll lose thrust. After a few attempts, however, you’ll get a good feel for it and can keep the board on the water’s surface a little longer than necessary to build up speed, before taking off in a relaxed manner. As soon as you’re in the air and your flight has stabilised, release the pressure on the finger ring, which stops the motor immediately – from this point on, you’ll only be using the wave or the wing for propulsion. The concern about getting caught in the rotating propeller in the event of a fall seems to us to be relatively unfounded: As soon as you take your hand off the wing, the button on the finger ring is automatically activated, bringing the propeller to a standstill straight away. To prevent the propeller from starting accidentally whilst swimming or ascending, it is also activated by a double-click. Once airborne, you can ride the Duotone Foil-Assist as normal on the foil. The drag from the motor is barely noticeable, as it has been designed to be quite slim and is also mounted high up on the foil mast.

The weight of the hip belt takes a bit of getting used to; at around 4.5 kilos, the battery belt isn’t exactly light. However, any concern that the weight might make swimming more difficult or even pull you under is unfounded, as the belt is designed to provide sufficient buoyancy and supports its own weight. The rest of the riding characteristics are primarily determined by the foil being used; once airborne, the Foil Assist System has long since switched off. Consequently, the battery performance is more than adequate for this purpose. As the motor does not need to provide continuous thrust, the session does not end because the battery runs out – but, at most, because the rider’s battery has run out. After two hours on the water with numerous take-offs, our battery was still around 70 per cent full in air temperatures around 25 degrees.

Maintenance & Care

As this is a technical device, it requires some maintenance. Sand and salt on moving parts should be rinsed off with fresh water from time to time. The batteries should only be fully charged just before use; if you’re taking a longer break from surfing, it’s best to store the batteries at 50 per cent charge.

Duotone Foil Assist – the verdict

No doubt - the Duotone Foil Assist is primarily useful for downwind riding and prone surfing. When wing foiling, it helps you get airborne in marginal wind conditions. This makes a huge difference, particularly at spots with very gusty, light winds. Foil surfers who are still working on basic manoeuvres or perfecting their pumping technique will also find they get up on the foil much sooner and stay up for longer. Ideally, the system should be combined with a slim mid-length board such as the Skybrid or the Midfish, which was specially developed for this purpose, because these boards allow thrust to be converted into speed more effectively than on short, compact boards.

Duotone Foil Assist – technical specifications

• ​Product under review: Duotone Foil Assist AL
• Pole (aluminium): 84 cm
• Price of test set: 4,799 euros
• Contents: Foil Assist mast, propeller, 2x battery, charger, battery belt, leash & cable connector, protective covers, tools, screws, remote control & finger ring
• Special features: Set including a carbon mast for 5,999 euros
• Information: Visit the website