Yesterday I´ve had the pleasure to talk to one of the most successful and influential persons when it comes to aerodynamics in watersports. Ralf Groesel is his name. And if you have no idea who the heck I am talking about: It´s his kite designs which have accumulated the most world championship titles as he had been working in the kitesurf industry for the past 30 years. He indeed could be doubled a true wunderkind and there´s one particular design he engineered and made work which has direct influence on how we sail today: I am of course talking about the Oxley sail.
I´ve had the pleasure to test an Oxley a few years ago during a trans Biscay cruise on a brand new Excess 11 catamaran. I am honest: Back at that time I was a bit overwhelmed by both the weather (too rough), the catamaran (my first ever journey on a multihull), the circumstances (Covid just hit, skipper and owner left the boat leaving me alone with his two kids). So I just briefly got up the kite and … quickly took it down to concentrate on the main task, bringing the boat safe to Spain.
A sail that is easy to operate. And fun to drive.
In any case, for some reason this experience just popped up in my head again. Maybe because of the fact that my new yacht is more and more nearing it´s completion and I am increasingly organizing all the stuff needed to rigg the ship, which includes, of course, the sails as well. Originally I had planned to purchase the whole setup of sails from Quantum Sails, which is still true for the standard setup of full batten main and the Jib, but as for the light wind sails, I am not so sure anymore. Why?
For once, I will be sailing single handed most of the time, my other crew members will be my kids, which are sailing indeed but too you to be entrusted with standing a full watch unobserved, or my wife, who isn´t a keen sailor at all. What I am looking for is a sail that is easy to set up. Best would be a “fire and forget”-solution. And of course I need a sail that can be operated safely even in gusty conditions and – best would be – in a variety of points of sails. And here my brain kind of pointed me towards the Oxley “kite sail”, just as did so much positive feedback from skipper who use it. Lately I interviewed a couple sailing an Allures 51.9 through the Arctic and essentially around the world, who had nothing but full praise for the Oxley. So, let´s talk with the engineer who literally made the kite fly – Ralf Groesel.
“I can see fluidal patterns around objects.”
Ralf´s life is worth a documentary, if not a full-blown movie. Honestly. He has the same age as I do and maybe that´s one reason why we connected so fast in our video-conversation. He sat behind his desktop in his office in Macedonia, looking down through a large window onto the buzz and fuzz of his company. They are producing world-leading high-tech garments and other laminate-materials to be used in kites and … sails. I ask him how he started to being interested in sailing, kiting, the wind and such.
“When I was 14 years of age, the first thing I did – of course against the will of my mother – was to start jump off planes with a paraglider. I just loved it so much! It is still the one big passion of my life!” His passion however was driven by a gift. A gift, very, very few people have: “The older I got the more I realized that I apparently have the ability to see flow patterns around objects. I have an instant and profound understanding of fluid and laminar motions of air or water around any sort of objects.” A gift which also comes with lucid dreaming and – often a burden – a non-stop working brain that is constantly solving aerodynamic problems. Truly amazing, but it also comes with downsides, like any intellectual giftedness. But for whatever reason, Ralf was able to see and quickly understand how stuff works: He soon started to build his first own paragliders and began self-train how to utilize CAD-software. This is how he started construction works at the age of just 16 years …
„At that time I finally built my first real paraglider. I was barely a young man and went to the big trade fairs of the kiting and paragliding world. But I was treated poorly. I knew that my design was years ahead of everything on the market back then. But almost all of the guys I spoke to literally chased me off their booths. It was very frustrating!” All but one, refused to even listen. The one who did was no other than the CEO of SWING, at that time market leader for paragliders. He hired Ralf to become his test-pilot. The wunderkind started to learn by the minute, gaining more and more experience, sharpening his senses. “Right after acquiring my A-levels I started my first own company, Flysurfer, to join the business. A bit later our first soft-kite for kitesurfing entered the market.”, Ralf tells me. Flysurfer is still active on the market, successful. Ralf was 20 when he founded the company.
Bit it wasn´t enough for him. As much fun kitesurfing is and as much as he loves the connected lifestyle of kiting still today, it was the paragliders he really wanted to make. His second company was quickly on its way, with “Skywalk” he finally could do what he wanted to do. It was then around 2001/2002 when he met the German sailor, Hartmut Schaedlich: “He was introduced to me by one of the Skywalk founding members to whom he pitched his revolutionary idea: What if one could combine a powerful light wind sail with a paraglider in its middle to stabilize it?” Hartmut had a patent on his idea and several mockups as proof of concept. Once I saw the sail and the 3D data, it was instantly clear to me that there was room of substantial improvements. I also found the idea very interesting and compelling. So, I started working on the problems.” Ralf was sure he would be able to solve the issues: In the end, he says, everything is mathematics, physics and logical thinking.
The Oxley sail principle
I ask Ralf to comprise the basic idea and how the sail works for a complete newbie and dummy. After a smile and a few seconds of thinking it over, he says: “Well, just plain and simple: This sail makes sailing more easy.” I am rolling my eyes, a bit rude, I know, but of course this is such a worn out marketing phrase that after a gazillionth time of hearing it, it doesn´t even hurt anymore. But Ralf means it: “No, no, I am absolutely serious with this!” So I am asking the question in a bit different way: What´s the principle behind the workings of the Oxley sail?
„Hartmut´s idea was to combine the stabilizing and lifting effects of a “wind” – the kite – with the power of a spinnaker sail.”, Ralf tells me. “But the more I looked into their models and calculations I understood that they hadn´t been able to make it work in reality. The variables are very complex, the aerodynamics did not work out as intended.” It was only after Ralf´s meticulous work that finally the breakthrough happened: “The wing shape was the key as it has not only a lifting effect but also a spreading influence to either sides of the sail. This means that the leeches of the sail will be stabilized, hence the tendency of the first versions to start oscillating and being unstable was eliminated.” Ralf explains that this way new shapes had been made possible for both the wind and the sail: “We started testing and really pushed the limits to make it work, which it finally did!”
So in essence, a specially shaped paraglider is integrated into a specially shaped symmetric spinnaker, right? Ralf nods: “The Aha-effect for most customers is the understanding of the pivoting effect the sail carries: Because, if a gust suddenly increases pressure onto the sail, it will proportionally increase the uplift of the wind at the same time -hence, increasing its lift.” Ralf demonstrates with his hands how the gust is lifting up the wing ever so slightly. “And what happens?”, he asks … well, it´s an opposite force against the pressure of the gust, I guess? “Exactly! The lifting of the wing kind of pushes back against the rigging, counterbalancing its tendency to heel. This works like a foil, but above water. The faster an Imoca sails, the more lift the foil creates, counteracting the heel of the boat. Same here: The more lift our wing creates, the more it counteracts the heeling effects of the gust.”
This would mean that the Oxley sail is kind of calmer in rougher weather? “Yes exactly!”, Ralf smiles: “The thing is that you can – and most customers do – use it as a light wind sail exclusively, but it is capable of much more!” Apart from the fact that the quasi “hole” in the spinnaker also functions like a pressure relief valve in case of a very violent increase of wind speed, Ralf explains that the Oxley is much more than a straight downwind sail. Which I find most striking …
Much more than a downwind sail
Many sailors use this sail as a kind of Gennaker substitute. When you are sailing around the world in the coconut route for example, dead downwind driven by the trade winds, a Gennaker quickly reaches its limits as the cannot be used in TWAs greater than 160, 170 degrees. At least not safely and conveniently. On the other hand, the classic Spinnaker, which can sail dead downwind, is almost extinct when it comes to modern cruising yachts, it has become a merely “classic” on such yachts and peculiarity among “real” sailors. The Oxley, however, offers a solution: It truly can be used to sail dead downwind: “This is often the main driving factor for skippers acquiring one of these”, Ralf says. “But the best thing is yet to come.”, Ralf smiles.
As the Oxley´s sail profile is not shaped like a true Spinnaker, it is indeed possible to utilize the sheets to apply little, but very important trimming to the sail: “This way you can flatten the profile and make it a bit asymmetric. The outcome will be a wing-shape, rather than a symmetric blister you would suspect when you think of it as a Spinnaker-type sail.” What this means is that a skilled Oxley-sailor could indeed point the bow into the wind and use it as a Gennaker! “It´s even possible to trim the Oxley to essentially become and behave like a huge oversized Genoa, making sharp upwind TWAs possible. And this is where the fun begins!” Ralf tells me that customers on sea trials regularly become literally shocked!
The best thing about it: Appalled customers!
Ralf tells me that he notices frequently how shocked and appalled even skilled and seasoned skippers become when they see what the Oxley is truly capable of: “It seems that the sail´s performance is all against their experience. Their expectation was to see a downwind sail, now the boat is sailing upwind, literally in the wrong direction, in their eyes!” When the weather starts to turn a bit nasty and wind is increasing a notch, the “lifting effect” of the sail and its counterbalancing forces are putting them over the edge: “It´s my biggest reward to witness this big Aha-effect! Really.” Slowly I realize that I had tried out the Oxley back with totally the wrong expectations and zero knowledge myself as well! And: If the sail works that way, the range of application of this sail must be widened completely, I ask Ralf.
„Yes, I think so! Oxley is much, much more than just your convenient, “fire and forget”-downwind sail. In essence I would say that it fits any sailor who wants to squeeze out the optimum performance.” He tells me that in his eyes the Oxley is a fascinating product that comes with a uniquely and very steep learning curve for the user – paired with exciting moments of success. He tells me about lots of sailors having tried out the sail, who literally freaked out when shown the full potential and later becoming skillful users themselves: “You can really push your boat with an Oxley! And the most fun part is, that with just a bit of effort, it will make you boat fast in very little wind, literally, in no puff situations, you will start to sail!” In his eyes, the sail is simple to use, intuitive in its application and trimming and very safe, even in strong wind conditions. In this way, the “appalled customer” is a very good thing, with their expectations regularly exceeded.
“At the end of the day, I´d like the sailors to have fun out there!”, he says. Especially European, most prominently German and “northern” clients tend to be too strict, kind of gridlocked in a certain old school doctrine of how sailing should be and what´s a “true” sail and what is not. “Innovations often have a rough start, groundbreaking ideas even more: The industry on the one hand and often the sailors as well kind of restrict and shield themselves from those.” This is something Ralf haven´t experienced in the kiting industry or in paragliding, at least not on such a level: “I would love to see that sailors allow themselves to veer away from their “safe paths” and try out something new. It´s really fun to push your boat with an Oxley! I´d love to see more of those bright smiles and joyful cheers!”
Physics and aerodynamic principles don´t change
But if this concept works so perfectly fine, with such a groundbreaking outcome, why don´t the big players like North Sails offer a sail like the Oxley themselves? In Ralf´s opinion that´s because they simply can´t: “Making a sail, honestly, is pretty easy. And those companies are indeed very good at it! But paragliders, which is essentially aeronautics, is a whole different level. They simply don´t have the knowledge nor the people to do it. It´s really hard to even copy the concept, which is why certain me-too brands don´t have the success they thought they would have.” And there´s another problem: The production.
„See, back then when we started with Istec in 2004, I found out that there wasn´t a manufacturer capable of building the sails as I wanted. So in addition to solving the engineering problems and bring Hartmut´s idea to life, I had to literally invent and build up the manufacturing process in order to achieve the intended outcome.” The production of ordinary sails, new shapes, new laminates and such, can easily be leased out to third party production companies, putting in the brand labels of the OEMs. As for the Oxley, that´s a whole different story, Ralf explains. “I have been working for Boards & More, the company behind the brand of North Kiteboarding until 2017, then rebranded as Duotone. From 2003 until 2023 I was their Kite Designer. I know how difficult it is to reinvent the wheel and in regards of the sail-industry, you really have to have expertise in paragliding manufacturing.” This explains why there are essentially only two brands on the market right now offering the real wing-sail product: Which would be Oxley, Ralf´s company, and Istec, his original employer.
“Physics do not change. Aerodynamic principles neither – so I´d say that the concept of our sail is clear, logical and fixed. There is no need for coming up with hybrids, like some try, which in my view only dilute and weaken the clear range of application the two sails stand for.” Where concept-wise Ralf protects and fights for the solutions, the more open-minded and excited he gets when it comes to introducing new materials, combinations and production methods. Ralf has founded the manufacturing company Brainchild-Production located in North Macedonia in 2022. Focused on high-tech materials, new production methods and a huge emphasis on sustainability, his companies have set new standards within the Kitesurfing industry literally overnight.
“I have seen the need for a radical change within the kitesurfing industry”, Ralf explains. “For decades, we have been using the same materials, originating from the sail industry mainly. But the technical requirements have changed, the sport has developed rapidly, and I always wanted to create a playground for innovations. Now, we are the world market leader in advanced production processes, like ultrasonic welding or full scaled digital printing on high tech materials. We are working on material combinations which ultimately will benefit the Oxley sails as well.” Now that´s quite a story, right?
What´s the difference between an Oxley Bora and Levante?
Coming back to my own sailing aspirations, I try to really take into consideration to skip the idea of putting a Code 0 and a Gennaker onto my new yacht and substitute both with an Oxley. But there are two versions of it, the Bora and the Levante – which one to choose? Where are the differences and which one is suited for which type of sailing? “It´s pretty easy to distinguish both”, Ralf explains: “The Oxley Bora has a double-walled, kind of “real” paraglider as its wing. This way, next to the lift created when put up in the wind, there´s also ram pressure. In contrast to the Levante, which has a single-layered wing, creating “only” lift.” Bora offers maximum cushioning effect and is suitable for heavier yachts and stronger winds.
“The Levante creates less lift, hence a bit less dampening effect.”, he tells me: “It is suitable for lighter boats and also lighter winds.” In the end, it all depends on your yacht and on the sailing program, Ralf says: A sail like this shouldn´t be bought blindly online, a skipper willing to buy one should definitely contact a certified and trained dealer where a proper consultation should take place. “A suggestion which sail fits best to your individual style of sailing should take into account your sailboat as well as the sailing area”, Ralf says. Apart from that, a proper sea trial and short dash out for a demonstration of what the Oxley is capable of is not just advised, but really great fun! Well, here´s an article coming up for next spring, I gues …
“Just go out and have fun!”
In his deepest core, I am convinced now, Ralf is still the excited paraglider and fun boy surfing with a kite up. For him, the kite-scene and paragliding community is much more fun-driven, excitement-oriented. “You know, it´s the best feeling when you go to the beach, I can still see so many of my kits still used and loved by the people, and all are smiling! All have so much fun!” It would be great to see those bright smiles much more on the pontoons of the marinas: “The Oxley is a real shift of paradigm. It´s not just a powerful sail, easy to use and safe to apply, but it creates a real benefit!” And this benefit, Ralf says, is fun!
“I want the people to have fun. Simple as that! Go out, have fun and enjoy what you are doing! The Oxley is an enabler for fun, I know it, I´ve seen it so many times: Just try it out!” What a wonderful closing sentence for this article, I think to myself. I´d never had expected that Ralf Groesel´s story would be that gripping: From a gifted wunderkind to one of the most successful kite-designer and engineer of the wing-sail. What a relatable, sympathetic and nice guy, I think to myself. And catch myself thinking about the color that my Oxley might have in a few months … Well, to really close this article, Europe´s biggest sailing magazine, Yacht, designated the wing sail in their 100 year anniversary issue (back in 2004) as one of the 100 most influential and important inventions in sailing of the past 100 years. And that´s, I think, a true accolade, isn´t it?
Pictures © with kind permission by Oxley Sails, Brainchild Production & SY CASTELLA
Related articles you might find also interesting to check out:
My first encounter with an Oxley sail, traversing the Bay of Biscay
Another wunderkind: The Nomen clamps inventor Axel Hoppenhaus
Single handed Gennaker retrieval step-by-step tutorial