What goes on behind the design? The guys at Duotone flew over to Maui to catch up with Foil Wing designer, Ken Winner, to get all the insights into the development of his latest project.


Ken, how did the idea for the Foil Wing come about?

Back in 2011, I tried an inflatable wing for use with SUPs. It didn’t excite us enough to develop further, so we shelved it. A few years later, Ralf Grösel took on the idea to design an inflatable sail for windsurfing that became the successful product you know as the iRig.

Then in the spring of 2018, I saw Flash Austin out on the water riding a SUP hydrofoil board powered by a home-made hand-held wing he had built from fibrerglass spars and canopy material. It got me thinking, I bet I can make something like that, but as an inflatable wing.

That’s where the design process began. Starting mid- 2018, Sky and I tested 20 or 30 prototypes and refined the idea from a silly novelty item — early protos had handles, no windows, a floppy inflatable strut, too small leading edge and no battens — to a performance-oriented piece of sporting equipment. 

So, you just decided to try it? No consulting with colleagues, no budget approvals?

Yes. A great thing about Boards & More / Duotone / Fanatic, something I’ve always enjoyed, is that our designers have great freedom to chase fun ideas. We don’t need to have a big meeting or a conference call or approval from a board of directors before we go and experiment with new product ideas. I blew quite a few thousand dollars and a lot of my time on Foil Wing prototypes and testing before we ever decided we were going to turn the Foil Wing into a product.

Of course, we do this because even if we don’t come up with something good right away, something that other people will want to use, we always learn a lot from the process and that always helps with the other products we’re working on.

How was the development process and what design iterations did you go through? At what stage did you bring in the boom and battens and did you try inflatable struts?

The first proto had segmentation similar to the Neo, profile similar to the Neo, no windows, an inflatable strut with sewn-on grab handles and not nearly big enough leading edge diameter. However, we quickly moved on. The next proto had fewer segments — because the Foil Wing has way less leading edge curve than a kite, so it needs way fewer segments in the geometry. And we quickly adapted a rigid boom to the next proto because the handles were, frankly, Mickey Mouse. Simple, yes, but zero performance.

Every rider, whether trying to learn the basics or trying to learn tack-jibe-tack-jibe circles, can benefit from the rigid connection to the wing that a boom provides. It’s also really nice to be able to slide a hand along the boom to exactly the right spot or being able to extend or shorten the boom for more or less power. The boom is, simply, a no-brainer.

I was reluctant to bring the battens into the design as I feared the added weight, but with battens the gain in performance was overwhelming.

Does it get tiring holding onto the Foil Wing without a harness?

That’s a common question. The first thing to understand is that the rider doesn’t hold up the wing, the wind does. Aside from that, whether it’s tiring depends on the rider and what he or she is doing.

For example, downwind foiling in 25 knots puts roughly zero load on the arms. If you’re an 80-kg guy on something like the Fanatic Sky foil SUP and a 2000sqcm front wing, you have 10 or 20kg load on the arms to get up on the foil, but then once up on the foil the load goes pretty close to zero. If you catch a swell, the load is zero.
If you’re going across the wind, you have the option of sheeting in hard and going fast, in which case there’s some load, or you can just glide easily along with very little load on the arms.

Upwind foiling can be tiring or not – depending on the physical condition of the rider. Most fit windsurfers can easily ride a SUP hydrofoil upwind for an hour without feeling the need for a harness.

We regularly ride two-hour sessions, upwind, downwind and wave riding without any problems. My wife goes for two hours, no problem.

What’s it like to learn?

Learning on the Foil Wing is relatively quick. People with a background in kiting and especially windsurfing, can pick it up rapidly. It’s easier to foil SUP with the Foil Wing than learning with a paddle. Holding and maneuvering the Foil Wing is easy and very intuitive.

Naturally, it depends not only on the rider’s background but also water conditions (flat water with steady wind is easiest) and the learning progression he or she chooses. As with most things it’s easier to learn with an instructor and on the right equipment. For example, a novice will want to spend some time on the beach learning to handle the Foil Wing in light or moderate wind.

A possible step for someone with little wind-sports background would be to ride a big windsurfing board — one with a daggerboard — and learn more about handling the Foil Wing. Some people even spend some time on a SUP board.

Ultimately, the rider will want to get on a hydrofoil. Something like a 7’0 Sky SUP with 2000sqcm or 2500sqcm front wing, long fuselage and 75-cm mast works great. The rider will ride around a bit on its knees, then progress to standing, then progress to foiling.

Then, for the more advanced rider, jibing with the Foil Wing is super easy. Way easier than foil jibing a windsurf or kite rig. Tacking is not easy, but flying tacks are at least as easy as with a kite, and far easier than with a windsurf rig.

Bottom line: Learning to ride a hydrofoil with a Foil Wing is the easiest way of learning to ride a hydrofoil.

What are the wind range limits?

Initially, I designed the Foil Wing to replace my paddle for downwind foil SUP where the winds are commonly around 20-25 knots. Most of the early protos were 2.5 meters in sizes and I was easily using them in 25 to 30 knots gusting 35 knots.
Now, that I have a 5-meter Foil Wing, I can get flying on flat water in about eight knots of wind. That same 5-meter works for me in 15 or 18, though I can go to the 4-meter in about 12 knots of wind.

How good are the upwind capabilities of the Wing Foil?

Surprisingly good. Early protos, the ones with no boom, no battens, flat profile, flexy leading edge, sucked for going upwind. But, we worked through all those issues and in the end are quite pleased with our upwind ability. We go upwind better than a lot of windsurfers and kiters and generally out-perform most sailboats.

What features would you point to? 

  • We like the dihedral, the upsweep, in the wings. This contributes a lot to stability.
  • There’s back-sweep in the leading edge — not too much, not too little — which also contributes to stability. Having too little sweep would force the riders’ hands too far forward on the boom, and having too much would force the rider’s hands to an awkward position too far back on the boom. We think we have found a good balance.
  • The big leading edge diameter — so big it looks freakishly big —  is really key to power and performance.
  • Windows, of course. No-brainer there. Essential to catch swell and be safe cruising in traffic.
  • Boom — too many performance advantages to list here.

How does the Foil Wing compare to kitesurfing or windsurfing?

First, let’s be clear: Nothing replaces windsurfing or kitesurfing or prone surf foiling or SUP surf foiling or downwind paddle foiling. These are all awesome sports and they all have their particular advantages and appeal.

That said, the Foil Wing has its own particular advantages. To name two, it’s light and simple. A Foil Wing weights 2 or 3kg, max. Pump and go. No lines. No need for a huge sandy beach. No need for a big, heavy, expensive sail. No need for footstraps or harnesses or harness lines.

To name another, it’s great for going straight downwind in swell. With a windsurf rig you have to swing the boom from side to side when carving heel-side to toe-side and back. This is not as easy, smooth, clean, intuitive and fun as effortlessly handling the Foil Wing through a similar maneuver. Some might say you can just go clew-first part of the time with the windsurf rig, but, really? No. We’re trying to have fun here.
And if you want to go downwind down-swell with a kite, you have to be thinking about the kite location all the time. Kiters who go down-the-line on a foil on a light-wind day constantly have to worry about line tension. Not so with the Foil Wing. It’s just so easy to put the Foil Wing exactly where you need it.

Who does the Foil Wing appeal to?

If you already own a SUP foil setup, the Foil Wing is perfect for you. You can surf on the glassy-wave days, and ride the Foil Wing on the windy days. If you’re into downwind foiling, you can ditch the paddle do it the easy way.

If you’re looking for an accessible, safe, thrilling, low-impact way to enjoy the water and nature, the Foil Wing could work for you. Foiling take-off speed is 6 to 8 knots. Cruising speed can easily be just 10 to 12 knots. At these speeds, crashing is little different from just falling in the water.

And if you’re looking for some kind of crazy, hair-ball adventure on the big days, the Foil Wing works for that too. Nothing quite compares with Foil Wing flying over massive seas in nuclear winds.


This article first appeared on the Duotone website here.
Read more about the coming of the wing in our summer 2019 issue, shipping soon! Subscribe here: https://www.thekiteboarder.com/product/magazine-subscription/