How to design a foil? Behind the scene at Indiana Paddle & Surf Co. with engineers Jan PĂĽtz and Andi Widmann

Have you ever wondered how a foil is designed? What is the thought process, the specification, to obtain a foil adapted to a given program? And how do engineers play with parameters such as aspect ratio, surface, profile, outline and materials? To find out, we called on the engineers and shapers at Indiana Paddle & Surf Co. Jan Putz and Andi Widmann. They explain their role within the Swiss brand, and tell us all about the design of the gear… with some news about the next new products!

Hello Andi, hello Jan, first of all, can you introduce yourself?

Andi: Hi, I am Andi Widmann, from Konstanz where I was born and have lived ever since. My favourite sports are  Wingfoiling, Windsurfing, WaveSup, Snowboarding and Skiing. I do watersports all year round at Lake Constance and at spots from north Denmark to south France travelling with my VW T5. Living at the shore of one of the biggest lakes in Europe and close to the mountains brought me to where I am now. My father is a passionate sailor and ski teacher, so I crew up doing these sports. With the new sports skateboarding at 9 years and windsurfing at 12 years I got hooked on Surfing Live. I started building my first Windsurf-, Surf- and Snowboards in 1981 at the age of 16 and since then I have developed boards for every new boardsport coming up on the water. Logically I made my passion for my job right after school.

Jan: Hello TotalWing, I am based in Konstanz as well. I do wingfoiling and found a passion in pump foiling. I studied mechanical engineering at RWTH Aachen University and worked in different engineering offices. After more than six years of ocean wave energy plant development, I became self-employed as a freelance engineer five years ago. Within that framework I have the opportunity to pursue projects from very different sectors, including the design of medical technologies, testers for automotive car parts, to hydrofoils (from 2020). Latter is fantastic, as I get to combine engineering with some fun on the water. Designing new foil components, brainstorming what changes will have what effects, and then being able to test the prototype on the lake in front of my house, just gives working a whole new quality.

What’s your role in the development of Indiana foils?

Andi: It started in 2016 with two SUPs, when Indiana needed a shaper with board shaping and CAD knowledge. For 2018  I already have developed Kite-, Wake- and City surfboards as well as Indiana’s first Foilboard. This particular Board evolved from a Wave-Foil-Sup-Hybrid to the popular 7’8’’ AllinOne, which is still in the line with its original shape. My role as a shaper is to see the future products, develop and test them and give advice for the production. Besides the whole Indiana team, I have a team of six members here in Konstanz, who represent the foil market quite well with their different age, weight and skill level. Besides feedback they also give me ideas about what equipment they dream of. Being at the lake and not a pro level rider, I develop all the flatwater and general market orientated stuff. That’s boards and foils as well as masts, fuselages and accessories like footstraps. I often build prototypes here in my workshop on the CNC machine and get on the water to test with my team.

Jan: On all of the new products that have come out in the past years (that I have been involved in) we have worked together as a team. And everybody comes at it from a different background. In the early stages of development my role is to contribute rough conceptual estimations and then further along in the process, I do all the CAD modelling right down to the last detail and prepare drawings and manufacturing specs. Finally, I jump in the water together with Andi and test the prototypes, get out and discuss my impressions with the team riders and Indiana ambassadors. Their input is also always invaluable for bringing things further along.

Can you tell us about the foil development process? What are the stages involved ?

Jan: In the early stages there is a lot of discussion, brainstorming, market analysis, and at times also one or the other long call involved. The development team comes together and the discussions are intense (in a good way). What follows is the technical design part, where I simulate and calculate the foil. Afterwards the detailed design work in CAD has to be done and we try to build and test prototypes as soon as possible. And before the customers can hold a perfect product in their hands, a lot of things have to happen in the background that are quickly overlooked. By this I mean, for example, the graphic design and many other small details, such as the specification of the sleeves or the creation of the items in the system and in the web shop.

Andi:  I am involved in all the stages mentioned above.

And so, in particular, what’s the process for designing a frontwing?

Andi: I come from learning by doing and trial and error, because often when I develop something, it is so new that there is nothing to look at on the market. That made me gain a lot of experience in thinking about every detail back and forth, to not make too big mistakes at first shot anymore. Nowadays most of the time I have a product which I can use as a base to start the development.

Material and production process is easy, because you can only make precise and stiff foils out of carbon in a mould. Parameters for choosing profile, AR or chord depend on what performance I want to achieve. By using as many different foils as possible, also from other brands, I have quite some experience which combination of parameters works in which way. So after the decision which performance the new foil should get, I can design a foil and Jan can do some calculations to see if we are basically right. Then we build and test it and hopefully don’t have to do it too often to end up with the desired result.

Jan: Due to the fact that the physics of hydrofoils in the water follow the same laws as airfoils in aviation, the design basics work out according to the design of an airplane wing. Even though the possible foil design ingredients are very clear, designing a foil is not cooking straight along a recipe, but a very iterative process. All design parameters have strong interdependencies. I had to learn that a good portion of experience is required . First assumptions like the design speed and foil geometry gets fed into some very basic calculations by hand. With the resulting numbers in mind (e.g. required lift coefficient, Reynolds number, aspect ratio) I dig into my aerospace and aviation books for the right choice of the profile section. Here it is essential to be able to read and fully understand the polar graphs, which describe the characteristics of the different profile sections.

Every decision made is a greater trade-off between different effects. As is well known by now, a higher aspect ratio increases foil efficiency, as induced drag gets reduced on the other hand the foil will require a higher rider level.

Can you give us an overview of the Indiana foil ranges you’ve worked on?

Jan: For perfect products the whole Indiana team knowledge and experience is required. Usually somebody has the project lead, so e.g. Andi had the lead for the MAR-Series and the coming up next level wing foils and stabilisers. I was in charge of the 1396P and a couple of brand new pump foils as well as the new aluminium mast-combo recently.

For which foiling practices and riders would you recommend each of these series?

Andi: My MAR-Series is made for winging. It is an easy going Wingfoil from beginner to advanced, depending on which size you use. You can also use it for freeride windfoiling. My new performance line has more speed, glide, control and turnability. Therefore it’s made for intermediate to pro riders for winging flatwater or waves. As well it works for prone or downwind foiling with slower waves.

Jan: The 1396P has been designed for the maximum lift at lowest speed. So it allows incredible low start speeds, longer pump heats and is the first choice for intermediate dockstarters and the best foil to learn paddle-up-foil. Furthermore, I personally love this foil especially for wake foiling behind small and slow boats, like they pass the Seerhein in Konstanz due to speed limits. Until recently, it was unimaginable to surf in such a small wake with the foils available at the time. The new Condor XL emphasises glide. It will take your maximum pumping time to completely new dimensions, but is still fun in sharp and agile turns at the same time. So I recommend it to every intermediate and above rider who loves glide and still wants to vary his turning radii.

If I’m not mistaken, you’ve also worked on the design of some of Indiana’s wingfoil and windfoil boards. It’s a bit like asking the same question about foils development: how do you determine the ideal shape of a foil board for a given program? We can see the current trend towards boards with a downwind profile, for example…

Andi: Yes, I designed the windfoil boards, which came naturally to me, with me and my team doing that sport from the beginning. The same happened with wingfoil boards, we started the sport and I developed boards for our needs at the time. My first range was the flatwater allround for beginners to advanced. It has to be stable when getting on board, kneeling and not flying. Next it has to gain speed and release from the water effortlessly. Getting easy on board and on the foil, that’s what it’s all about. Decades of shaping windsurfers gave me the knowledge needed therefore. Now the next line comes with refined shapes and smaller sizes for advanced wingers. At Indiana we have seen the trend towards downwind profiles already more than a year ago. Gunnar (Biniasch, Indiana development team colleague and pro rider living on Fuerteventura) has developed downwind SUP shapes for the ocean, which we have in the line since spring. With the feedback from these boards I developed a line of downwind style wingboards for super early flying with small wings in hand, which comes in stock very soon. Also recently I designed two sizes of paddle-up downwindboards for flatwater. Conditions are so different in the ocean and on flatwater, so have to be the shapes – stay tuned.

And finally, what’s next for Indiana foils?

Andi : We are coming up with a new line of masts, in carbon and aluminium. With our new profile we increase speed and eliminate ventilation. Also we intensively work on the stabiliser theme, here is so much potential not used yet. And finally we do the performance foils in a monobloc construction with the fuse and foil in one piece for better power distribution and less drag.

Jan: All our new products will finally come out with a name, which will make tech talk at the beach and in the pub easier. We have a very sexy new wing, the Condor XL coming out shortly. With JĂ©rĂ´me Baudoux we have a great new ambassador in the team and I am absolutely convinced that with the new large span pump foil, he will surpass his previous record by a lot! There are very exciting new pumpfoil stabilisers and the mentioned two new dedicated wing foil series for advanced riders, as well as smaller Condor foils for pump foiling in the pipeline – keep in touch!

Thank you Jan and Andi for this very interesting insight into innovation and design at Indiana! We leave you with this preview of the new 2024wingfoil boards, presented by Andi himself last week at Boot Dusseldorf.

Discover also the 2024 downwind crossover wingfoil/SUP foil boards :

More about Indiana Paddle Surf & Co.:
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About the Author

Laurie Montagner

From SUP Racing to wing foiling, through windsurfing, wakesurfing and surfing, you will always find Laurie somewhere in the South-West of France. Passionate about watersports, Laurie spends her time surfing, whether on the wave... or online! Laurie is indeed a specialist in social media marketing and web development, from writing lines of code to making professional videos. Very much a competitor, you've probably already met her on one of the SUP and wing events all over France!

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