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Duotone Foil Assist
Add electric propulsion to your foil setup!
It's here, and we are super stoked!
The Duotone Foil Assist has been in the making for a while, and after extensive development, Duotone is excited to introduce a lightweight, powerful, modular, and nearly drag-free system that allows you to foil freely in a variety of conditions. Whether you’re riding waves, going on downwinders, flatwater cruising, foiling behind ships, just getting started in foiling, or eager to wing foil on light wind days, the Duotone Foil Assist is set to become your ultimate foiling companion! Engineered for maximum performance and designed for effortless setup and use, the Duotone Foil Assist is compatible with a wide range of board and foil setups, including boards and foils from other brands.
Duotone Foil Assist 2026
Spend more time foiling, linking waves, trying new maneuvers and disciplines, and experimenting with different foil setups.
This innovative foil assist system includes various mast options and a smart watch style remote. Explore different propeller configurations and experience boosted foiling sessions.
The Duotone Foil Assist system is built to preserve the pure, natural feel of foiling while adding powerful assistance, intuitive control, and seamless compatibility with your current setup. Across all three Assist masts, the motor pod is fully integrated into the mast profile, creating a clean, hydrodynamic shape that minimizes drag, even during touchdowns, and maintains the smooth glide and efficiency of a traditional foil. With the batteries positioned on the rider’s hips, weight is kept off the mast and board, ensuring the setup stays as light and balanced as possible. The smartwatch-style controller, paired with a finger ring, keeps your hands free so your body can move naturally through every session, whether you’re pumping, paddling, or carving.
How does the Foil Assist compare to an eFoil?
The Foil Assist combines the advantages of an eFoil with those of a traditional foil setup, creating a versatile hybrid experience. It features a lightweight and highly agile design with a mast equipped with a motor and propeller. The electric propulsion allows you to easily lift off the water, navigate to the waves, and catch them with ease. Once you are up on foil, you can simply switch off the motor and enjoy the ride, letting the swell or wave carry you.
In comparison to an eFoil, the Foil Assist offers less power and runtime, but it still provides great assistance and enjoyment for riders of all skill levels.
The Duotone Foil Assist comes in three mast options with fixed motor positions. On the carbon and aluminum assist masts, the motor is positioned high, making it easy to motor out to the waves, match the wave’s pace and get on foil. For those beginning their foiling journey or seeking a setup that excels on flat water and in small waves, we also offer a Cruise version. This aluminum model features the motor mounted low on the mast, like an eFoil, always keeping it in the water. This design allows for smooth foiling on flat water.
FULLY INTEGRATED MAST (for excellent performance & easy assembly)
The motor pod is integrated at a fixed position on the mast (assist position: 17 cm below the top plate, cruise position: 15 cm above the fuselage). A clean leading edge, internally routed cables and hydrodynamic motor pod shape ensure optimal glide even during touchdowns and maximum maneuverability.
BATTERY HARNESS for less drag & weight
To keep the board-foil setup light and perfectly balanced, we have integrated the batteries into a lightweight waist harness. The harness allows for a full range of movement, making it ideal for extended or high-performance sessions, while the plug-in battery system makes installation and swapping effortless. Additionally, the placement of the batteries on the body offers another significant advantage: optimal signal transmission to and from the remote, resulting in consistent power output.
WATCH RING REMOTE for hands free riding
The Foil Assist Remote - a waterproof smartwatch-style controller with a finger ring - keeps your hands free for paddling, duckdiving, carving, or wing handling. Activate the motor with a double-click, then fine-tune your speed with simple plus and minus controls.
POWERFUL MOTOR WITH FOLDING PROPELLER for maximum power and low drag
The motor is compatible with all three mast options and delivers exceptional torque and thrust. Atop the motor is a bell with two folding propeller blades (available in plastic or aluminum). The folding gear propeller minimizes drag for effortless glide on the wave. Its integrated gear system allows the two-blade propeller to unfold instantly, delivering a seamless transition as you kick out of the wave and power back out.
The Cruise Mast also includes a propeller guard for added safety.
STANDARD TOP PLATE & FUSELAGE ADAPTERS for maximum compatibility with Boards and Foils from different brands
Duotone’s assist masts are compatible with all foil boards using standard US foil tracks. The D/LAB mast features a molded 3BS fuselage connection, making it compatible only with Duotone foils and the specially designed fuselage for Armstrong foil users. The alloy masts are compatible with foils from Duotone and ten other brands thanks to special adapters (not included in the sets).
SHORT CHARGING TIME to get back on the water as quickly as possible
The Charger can fully charge your two batteries in an hour or less, allowing you to get on the water quickly. It also features a discharging function to maintain the batteries at an optimal storage level of 40–60%.
THE MIDFISH offers several advantages in combination with the Foil Assist
Compatible with most foilboards, the Foil Assist fits seamlessly into your current setup — and pairs perfectly with the Duotone Midfish board. Available in four sizes (38 to 78 L), the Midfish is surf-oriented and super playful in waves and bumps. Its mid-length shape with a narrow outline and wide fishtail gives you offset foot placement, added stability, and extra drive through takeoff. It also keeps the power cable neatly tucked and out of the way while riding. The 58 L and 78 L models offer optional front footstraps for more control and support.
What's Included in Your Foil Assist Set
Discover everything that comes with your Foil Assist Set! Each set includes one of three premium mast options (AL, D/LAB, or Cruise AL) along with essential accessories: the eHarness, Watch Ring Remote, a full battery set, and a charger.
Foil Cruise Set AL
FREERIDE
This video guides you through the essential maintenance routine for your equipment after using it in salt water. Learn the importance of rinsing your entire system, including the board, mast, foil, remote, harness, and battery box, to prevent damage to the Foil Assist. Learn how to properly clean the motor bell, bearings, and control devices, and we'll provide tips on drying and applying protective greases for smoother operation and to safeguard against corrosion. Don't forget to recharge your batteries to storage mode (2-3 LED lights). Never leave the batteries empty or fully charged overnight or for an extended period, as this can reduce or end their lifespan. Make sure to perform these steps after every session.
Maintaining the Foil Assist Set
After each use, rinse the entire system with fresh water to ensure proper maintenance and longevity.
Rinse the harness and battery box with the latch closed and the cable attached. Remove the motor bell and rinse the inside of the bell and the motor bearings thoroughly. Rinse the watch remote and ring controller as well.
After your session, let your setup dry or at least wipe down the motor bell, motor, and protective caps for the eHarness and cable. Disconnect the cable from the eHarness and place the protective caps on the connectors.
If the connectors are wet or dirty, rinse them with fresh water, remove any remaining water with compressed air, and allow them to dry completely. Then apply a thin layer of dielectric grease.
Once everything is dry, apply a thin layer of 2-4-C marine grease to the stator. Then place the motor bell onto the stator and rotate it to distribute the grease evenly. Spray the bearings with WD-40 Specialist Penetrant to prevent corrosion.
If you do not use the Foil Assist mast for an extended period, rinse it regularly with fresh water to prevent salt deposits inside.
Storing the batteries
⚠ Never leave your batteries turned on in the battery box when not in use.
❗ When removing the batteries, never open the battery box when it is wet. Pay attention to any salt water that may drip from your wetsuit, remote control, or hair.
After every session, you must recharge the batteries to storage mode (2-3 LED lights). Never leave the batteries empty or fully charged overnight, as doing so will reduce the batteries‘ life.
⚠ Do not charge the batteries immediately after use. Charging a hot or cold battery can damage the cells. Wait 30 minutes to 1 hour to allow the battery to cool down or warm up to room temperature.
If the batteries are left idle for an extended period, make sure to run a full charge then storage mode cycle every 3 months to maintain optimal performance and longevity.
Always perform charging and discharging at home, under supervision, in a well-ventilated area. Always ensure that there are no obstructions next to the air vents on the sides of the charger. The air from the charger may be hot, make sure items are kept at a safe distance from the air vents. Never leave the system plugged in when not in use.
The best temperature for battery storage is between 10 °C and 25 °C (50 °F and 77 °F).
How to Use the Batteries and Charger
In this video, Terence explains how to store and charge the batteries correctly to ensure a long battery lifespan.
Duotone chose these high voltage lipo batteries because of the amount of power they provide at an airline friendly size and weight. They are under 160W hour, so you are allowed to carry two! Total game changer!
*Please do check with your airline before you travel and get their approval.
MAINTENANCE AND CARE
These batteries are perishable items, and they will slowly degrade over time. With proper maintenance and care, you can prolong the lifespan and performance level. To maintain your battery, one of the key things is to never leave them fully charged or empty overnight. It is not good for the batteries. After the session, make sure you put them into storage mode. Or if your batteries are full and you decide not to go for a session, put them into storage mode.
STORAGE MODE
Storage mode is 50%, which is the healthiest state of the batteries. If you are storing them away for extended period, for example, if you're done for the for the season, always make sure to put these batteries in a full battery charge cycle, charge them to full, and put them to storage mode every 3 months to make sure they're healthy. If you don't, it'll stay dormant for too long, and the battery will slowly discharge, which is not good for it.
STORAGE TEMPERATURE
Make sure to store them at room temperature. The battery is not good when it is too cold or too hot. Also, it’s not good to charge these batteries immediately after use. If you feel that they're hot to your touch, let it cool down to room temperature, then you can charge them or set them to storage mode.
*Please read all the safety instructions on your foil assist user manual and on the batteries before use.
CHARGER
To use the battery charger, plug the adapter into the wall outlet. The green light, that means it's on. Plug the cable into the charging dock. Once it's plugged in, there's a switch on the back where you turn it on. The green lights indicate that the charging dock is on and ready. To charge the batteries, remove the caps, and place it into the charging dock. Press it down to engage the connectors and press the button. Once you see the red light on, it's charging. You will hear the cooling fan turn on, and the batteries will flash the capacity level it is charging to. Once fully charged, it will automatically turn off and the light will turn green again.
STORAGE MODE
To put it in storage mode, insert the battery then turn on the battery by long pressing the battery button until it turns on. Wait a few seconds, then you will see a flashing blue light, meaning it's discharging to storage mode. Once it reaches storage mode, the charging dock will turn off, but you must manually also turn off the batteries. Always remember to unplug your batteries when they are fully charged as a safety precaution. Turn off your charging dock and unplug your adapter. Be careful to make sure the air vents are not obstructed, because they blow out the hot air. Always read all the safety precautions and warnings on your charging dock.
How to Set Up Your Foil Assist
Terence shows you how to set up the Foil Assist with the tools and screws provided with the Foil Assist set. You can find another thorough set of instructions in the user manual.
GETTING STARTED
Start by installing your mast like you normally do, but before you do that, you need to install the M6 T-nuts and slide them to the rear for your V cable holder. Then you install your M8 T-nuts and screws. Slide two to the front and two to the rear. They included longer screws just in case you have a board with deeper tracks. Next, you place the mast on top of your board and slide the screws onto the top plate and then you use your Torx key to tighten the screws. The Torx key is compact, so there's less chance of it hitting your mast. Tighten all of them up about 90% just to keep it level and then crank them down one by one.
INSTALL THE FASTENER
Make sure the cable is flat and place the big holes over the screws and move it down. If the protective hose is too far up, you can move it down to give you enough space. Then place the big hose over the screws and slide to the small hose. Grab the Torx key and use the M6 head to tighten them down. You don't have to crank them too hard, because it's plastic. They just need to be snug and in place.
INSTALL THE FUSELAGE ADAPTER
This is a 3BS system. Place it into the mast. Then you place your foil on top. Grab the three longer screws in the screw box. These are the 15 mm, the three of them. Install them one by one. Use your Torx key and tighten them about 90% as well. Then you can crank them down one by one.
INSTALL THE MOTOR BELL AND PROPELLER
Check that the propellers are folding and unfolding freely and make sure there is no debris, sand, or dust inside the motor bell. Also, check that the stator is clean and there is no sand on it. When you install it, be careful. There's a very strong magnet, so make sure your fingers are free from the edges or else you're going to get pinched. If you're holding on to the can, hold it firmly so you don't get cut by the sharp edges. Once it's on, it's always good to rotate it one time with your hand, just to make sure it's rolling smoothly. It’s good to use the Torx key to make sure the screws on the motor are fastened because they may loosen over time from the vibrations of the motor.
PUT ON THE LEASH
When you open the rail saver, just be careful. There's a bungee cord here, to make sure the cable is elevated and there's no chance of it touching the propeller. If this bungee does come loose, simply wrap it around your cable and install it into the rail saver. Install the rail saver into the leash plug strings and close your rail saver. This rail saver is not like a typical surf leash. It's made of heavy-duty materials just to withstand heavier loading and for the foil assist. Once that's done, it should be combined into one unit, so the cable should be in the neoprene sleeve of the leash and the elastic webbing should be in the coils string through the coils of the cable. This is to make sure there's less chance of getting tangled since it's a one piece design.
INSTALL THE CABLE AND LEASH ONTO THE BATTERY BOX
First, remove the caps from the connector and remove the cap ring off the carabiner. Remember to make sure to put the carabiner on the harness. This is very important. The leash is shorter than the cable, so you want all the loading on your leash. If you forget the leash, all the loading is going to be on cable, and it can overextend and damage the internal cables. Once you have the leash on, it's time to put the connector into the battery box. Check that the connectors are clean. There's a notch on the connector, and there's a recess on the battery box. Make sure you lock it securely to make sure there's a water watertight seal. Now the cable is connected to the battery box.
PAIR YOUR REMOTE TO THE SYSTEM
Make sure the remote is 100% fully charged, then remove the USB type-C charging cable, then install the ring controller. Make sure there's an O-ring, which provides the watertight seal. Also, make sure the connector on your ring controller is clean, then install it into the watch. There is a flat section, so make sure you twist it tight to provide the waterproofness. Pay attention to the ring controller, because it will turn only 180 degrees depending on which wrist you put it on. Don't overturn, as it will break and destroy the internal cables causing malfunction.
INSTALL THE BATTERIES
Remove the caps and make sure the connectors are free of sand and it's clean. Open the neoprene cover and slide the lock to the unlock position. If it gets stuck, press down on the latch gently and it will slide freely. Open the latch and install your batteries. Before installing, check to make sure the battery level is at full. If it's four lights, that's 100%. Make sure the battery levels match, as it's recommended not to use a full battery and one that's not fully charged. The batteries only go in one way, with the logo facing you. When you install it, give it a little nudge to make sure the connectors are engaged, then turn on both batteries simultaneously by pressing the on button. Long press it until the light comes on, then you will hear a beep from the motor. The beep will only come on if you have the motor bell. Once it powers on, you must pair the system within 20 seconds. Long press on the remote and you will feel the vibration until it shows it’s pairing, then let go. Once it's paired, you will see the battery level displayed.
NOW IT’S GOOD TO GO!
Once it's paired, it's good to give it a quick test to make sure everything is functionally properly. You will see a lock symbol. You have to double click it to engage the motor, so if you click it once by mistake, it's not going to activate. For safety, it's always good to turn off the remote before you head into the water, as well as your batteries. And then when you're at the water, you just switch on the batteries and your remote. Since you already paired it once, it connects automatically.
The most important thing is to make sure the seals on your battery box are clean and to lock the battery box properly. Make sure the latch is in the lock position. Then you zip up your nail case and you're good to go. Now this system is all set up. You're ready to enjoy the water.
How to Replace the ESC (Electronic Speed Controller)
In this video, you will learn how to replace the ESC on your Foil Assist mast with this quick step-by-step guide. Start by removing the motor bell, the take out the motor and ESC, install the new ESC, and reassemble the motor and bell. Ensure the ESC cover is clean and securely tightened before reassembly.
Tools & screws needed:
- Torx Key TX20
- Allen key #3
- Motor: 3x M4x10 (with blue Loctite)
- ESC: 4x M4x8
- Motor Pod Cover: 2x rubber plugs, 1x M5x35 with bolt
- Spare screws: Foil Assist Maintenance Screws (40260-8008)
Steps to replace the ESC:
- Remove the motor bell.
- Unscrew the three motor screws and pull the motor out in a straight line.
- Unscrew the four ESC screws, remove the rubber logo plugs on the sides of the motor pod cover and take out the screw and bolt.
- Take off the motor pod cover.
- Unscrew the ESC top cover.
- Remove the ESC.
- Attach the new ESC to the ESC top cover.
- Insert the ESC screws through the holes of the motor pod cover and tighten them securely.
- Reinsert the motor into the ESC and tighten the three motor screws.
- Insert the two motor pod cover screws on the sides and replace the rubber logo plugs.
- Finally, reinstall the motor bell.
⚠ Make sure the ESC cover is screwed on tightly and is free from sand and dust before reassembly.
How to Change the Receiver in the Battery Box
The receiver sits in the lid of the eHarness battery box. To replace it, open the battery box, remove the two screws from the receiver cover and disconnect the receiver connector. Reverse the process to connect the new receiver.
Tool & screws needed:
- Torx Key TX10 (included in your Foil Assist Screw & Tool Set)
- 2x M3x6 (spare screws: Foil Assist Maintenance Screws 40260-8008)
Steps to change the battery box receiver:
- Open the box.
- Remove the two screws from the receiver cover.
- Take off the receiver cover.
- Disconnect the receiver connector.
- Connect the new receiver to the box connector.
- Insert the connector into the box.
- Place the cap on top of the connector.
- Screw the two screws back onto the receiver cover.
How to Replace the Battery Box / eHarness
You can easily replace the battery box or just the harness by detaching four screws. Ensure the valve is properly seated in the harness hole before tightening the box to avoid damage.
Tool & screws needed:
- Torx key TX30 (included in your Foil Assist Screw & Tool Set)
- 4x M6x18 & washers (spare screws: Foil Assist Maintenance Screws 40260-8008)
Steps to remove and install the battery box or eHarness:
- Loosen the four screws of the battery box on the inside of the eHarness.
- Remove the battery box.
- Attach the new battery box or the new eHarness using the four screws and washers.
⚠ Ensure the valve is properly seated in the eharness hole before tightening the box to avoid damage.
Change the Propeller Blades Mount
To change the propeller blades mount, you need to take off the propeller blades first and then detach four screws.
Reset the Remote
Switch from Standard to Boost Mode
The default mode on your Watch Ring Remote is BOOST MODE, which offers seven speed levels. To switch between BOOST and STANDARD MODE (which has 5 speed levels), press the - and POWER buttons simultaneously.
Attach the Propeller Guard (Cruise)
The ePropeller Guard Cruise is only compatible with the Foil Assist Cruise Mast AL and attaches easily to the motor using three screws delivered with the propeller guard. We highly recommend using this guard, especially for riders with little to no foiling experience, as it provides an additional layer of safety. Please note that while the guard enhances safety, it does not fully protect against the rotating propeller. Caution is still advised when using the Cruise mast with the guard in place.
⚠ Note: Using the guard may result in higher energy consumption and therefore shorter battery runtime.
Required tools and screws:
- 3x M4x14
- Tx20 Torx key
- Medium-strength liquid thread locker
Here are the steps on how to install the Propeller Guard:
Take off the motor bell and propeller in a straight line.
You only need to remove the screws from the motor; it is not necessary to remove the motor itself.
Place the guard onto the motor, align the screw holes, and tighten the new, longer screws. To prevent the screws from loosening quickly, you can apply medium-strength thread locker.
Install the motor bell onto the motor.
❗ Warning: The magnets are very strong. Be careful with your fingers when attaching the motor bell.
Once the motor bell is installed, check to make sure it spins freely and the propeller blades are not in contact with the guard.
Charge the Remote
Before using the Watch Ring Remote of your Duotone Foil Assist, charge it to 100% using a USB Type-C adapter outlet plug. The remote control must be completely dry before it can be charged. The watch screen will go blank when fully charged. Unplug the charger and replace the charging cable on the watch remote with the ring cable. Before attaching the ring cable, always check if the O-sealing ring is still in place around the watch connector to ensure that the connection is waterproof.
Change the Propeller Blades
The Duotone Foil Assist can be used with plastic and aluminum propeller blades. To change your propeller blades, detach the screws, take out the sleeves and transfer both sleeves to the new propeller blades. The blades are marked 1 and 2. Make sure to match the corresponding number to the propeller mount. Check that the ridges of the blades are stacked correctly to allow the blades to fold and unfold freely.
Screws & tool needed:
- #3/M4 Allen key
- 2x M4x35 screws (3 Nm)
- 2x M4 washer
- 2x M4 nut
Steps to remove and install the propeller blades:
- Loosen the two screws.
- Remove the sleeves and transfer both sleeves to the new propeller blades.
- The blades are marked with 1 and 2. Make sure each number matches the corresponding marking on the propeller mount. Also check that the ridges on the blades are stacked correctly so they can fold and unfold freely.
- Tighten the screws.
- If the blades do not fold or unfold smoothly, check whether the gears are stacked correctly or if the screws are overly tight.
SWAP THE MOTOR
The motor can be easily removed from the Duotone Foil Assist Mast by detaching only 3 screws. It's important to pull out the motor in a straight line to avoid damaging the connector and to maintain the waterproof seal between the motor and the ESC.
⚠ Remove and install the motor only in a clean and dry environment.
Tool & screws needed:
- Torx Key TX20
- 3x M4x10
- Medium-strength Threadlocker (e.g. Loctite Blue 243)
Steps to remove and install the motor:
- Remove the motor bell.
- Detach the three screws.
- Carefully pull the motor out in a straight line to avoid damaging the connector and to maintain the waterproof seal between the motor and the ESC.
- Insert the motor into the ESC connector of the new mast. Press firmly to ensure a secure, watertight connection. Make sure the motor seal is properly aligned when sliding the motor back into the pod!
- Apply medium-strength threadlocker to the screws (Loctite Blue 243 or equivalent) to prevent them from loosening during use.
- Insert the screws back into place and tighten them securely.
- Attach the motor bell back onto the motor. Be careful with your fingers - the magnets are very strong.
Swap the Connector and Cable
To remove the connector and cable from the top plate of the Duotone Foil Assist Mast, you only need to detach four screws. Remove the connector and insert it onto the new mast, or attach the new connector to your current mast.
Tool & screws needed:
- Torx Key TX20
- 4x M4x12 (3 Nm)
Steps to remove and install the connector and cable:
- Loosen the four screws on the power cable connector.
- Remove the connector.
- Make sure the connector and the top plate of the new mast are clean and dry.
- Attach the connector to the top plate of the new mast. Press it down gently so the male and female contacts lock securely.
- Insert the four screws and tighten them.
⚠ Maintenance tip: If the connectors come into contact with sand, dirt, or water, rinse them thoroughly with fresh water, dry them completely, and then apply a thin layer of dielectric grease.
Checkout the collection: Duotone Foil Assist 2026
**If you have questions or need to coordinate an order call us at either of our stores.
Houston Kiteboarding
281-508-6485 sales@houstonkiteboarding.com
Pacific North Sports
360-794-1688 sales@pacificnorthsports.com
