Interview express Bill Hansen, Switchkites designer
Publié : mer. 12 déc. 2012 05:35
English version: (click on images to get full size - La version en français suit cette version anglaise):
LesFoilz (FZ) : Hi Bill. You are nowadays the designer of Switch kites but you have a long history in kite design and, more generally, in sail design. Those of us who followed your interventions on kiteforum may know some of your personal journey and career (for instance, the 3 struts kite project) but that would be nice if you could give us a short bio - in particular for our readers who only read French.
Bill Hansen (BH) : From an early age, I've had a natural interest and aptitude for things that fly or are driven by the wind. Kites, model aircraft, sailboats and boomerangs were always under construction with growing sophistication. My father had several airplanes and I learned to fly sitting on his lap and later earned my pilot's license at the minimum age. As a Junior High Student, I won the Illinois State Science Fair with a wind tunnel project entitled 'Facts of Flight' in which a tethered model plane could be actively flown. At University, I studied Applied Physics and after graduate school, I worked at UC Berkeley as a Research Associate on a Superconducting Electromagnetic Airborne Geophysical Prospecting system which was basically a large metal detector hanging from a helicopter. During that time I raced sailboats, flew airplanes, participated in skydiving and eventually began windsurfing in the early days of the sport with my own self-designed and built high-aspect fully-battened sails. After 5 years at UC Berkeley, I started a windsurf sail company named "Windwing' which grew into the largest US-based windsurf sailmaker. During that time I competed internationally in Speed sailing, windsurf course racing and slalom. Eventually we expanded to high performance stunt kites and set the standard for them which to some extent is still evident today. Around year 2000, I sold my interest in the company and became an independent designer/consultant for aerodynamics, kites and sails and have worked in this capacity for a number of brands and projects both inside and outside of the kiteboarding field. I also actively participated in open source kite design forums as a matter of self-improvement to push the limits of technology. It has been said that "if you do what you love long enough, someone will pay you to do it." I am blessed in that regard to now be a part of Switch.
FZ : On LesFoilZ, we are particularly interested in wave riding, with or without straps. One of your intervention I was very interested in was when you were commenting on the behavior of the switch method on the edge of the wind window (for those of you who want to read the post, look HERE). My take on your argument was that you were saying, amongs other things, that a wave kite should be a performance kite, and that comes with trade-offs. Could you tell us a bit more about what you think makes a good wave inflatable kite or even what would be a perfect wave kite, regardless of technology ?
BH : As a competitive sailor, the importance of upwind performance is obviously well-known. As an avid waverider and surfer, I found getting back to the line-up after a good ride (especially paddle surfing or with wind-blown current) was the worst part of the experience because of the time lost to the actual surfing. To me, a proper wave kite should go upwind extremely well if for no other reason than to get back to the line-up as quickly as possible. In addition, if the kite can operate well at the edge of the window, a larger range of motion is available to the rider to put the kite in an optimal position. Finally, kites that are capable of flying far to the edge also typically de-power well due to their ability to fly at low AOA (angle of attack.) But, that is not all of the equation. The final performance criteria for the optimal wave kite (other than re-launch and de-power) is fast turning without the loss of power and good drift down the line. We also wanted a powerful kite for the size because smaller kites are simply more maneuverable (and fun.) It is easy to make a kite sit back and turn fast in a pivotal power-losing way and there are many on the market. But, our vision includes a fast sweeping turn without losing power (which can be regulated by sheeting out.) Working with Felix in Hawaii, the criteria we sought were: Fast, non-pivotal powerful turning; excellent upwind ability; predictable drift; maximum de-power; easy re-launch; moderate bar pressure (so you can 'feel' the kite.) To us, this is what makes a great wave kite.
FZ : To what extent do you think you have achieved your goals? (I still have to try the method, it is on my must-do list)
BH : In the first version of the Switch Method (V1) we achieved most but at the sacrifice of higher bar pressure and tricky handling in gusty winds for less skilled riders. A kite which finds itself at the edge of the window is subject to natural instability due to the window expanding and contracting as the velocity and direction changes in gusts. In some cases. the kite simply finds itself beyond the edge of the effective instantaneous window. Subsequently, the Method V2 has been developed to allow adjustable bar pressure and better stability in gusts while overhead or at the edge. We believe we have retained the positives of the Method V1 while eliminating the negatives to open up the user profile to less-skilled, bar pressure sensitive riders. The response from our wave-riding Method testers has been unanimous.
FZ : With the increasing interest in wave riding, things are likely to evolve, and in particular the demand from the riders. As a brand close to riders (and to some extent made by riders), do you have some ideas about what would be the future of wave kites?
BH : At this point, even as idealistic as we can be, we find ourselves having trouble imagining how to improve it - at least for wave riding. We have already made some protos with differing parameters that perform very well but are not significantly better. Our immediate efforts and testing is with improved materials and construction which often impacts performance (both positively and negatively.) As the coming season progresses, we will listen to the riders and when we see a consensus of opinion, we will work to address them. This is how we see the best progress being made. One must also note that as the boards and riding styles evolve, the kites will follow (or possibly lead) the progress.
FZ : On lesFoilz.com, we are mixing (happily, at least up to now) tubes and foil kites. Some of us are even using exclusively foil kites in waves. Did you ever considered foil kite design?
BH : Yes. I have designed numerous 2-line, 3-line and 4-line foils for many years including the popular Slingshot 'B' series and others including but not limited to the Elliot Sigma Sport and Windwing Skyfoil models. At Switch, we are currently in production with 2-Line 1.5, 2.5 & 3.5sqm foils and nearing production on 4-line 7, 9 & 11sqm de-powerable foils. I have also previously made 4-Line ram-air 'C'-shaped sledfoils which were released to open source kite-design forums.
FZ : Wow … nearing production on 4-line 7, 9 & 11sqm de-powerable foils! You take us by surprise! Could you tell us more about these foilkites? Open or closed cells? Are you thinking about snow kiting with Switchkites?
BH : Switch is very interested in all aspects of kiting including snowkiting, buggy and landboarding. The 2-liners are open cells with closed wingtips to avoid collecting debris when dragging a wingtip. We view them as a progression from a fun 'trainer' in the 1.5sqm to a simple and basic landboard or snowkite in the 3.5 version (wind permitting due to square area.) The sheetable 4-liners we will be testing in the near future have a unique NACA inlet vent with interior valve flaps. To my knowledge no one has made such an inlet vent/valve in ram-air foils. If they do not work we will revert to the open-front inlet vents common to other foils and our previous prototypes. We are using a 2-pulley 'speed system' on the 4-liners for de-power / sheeting and our standard Switch control bar. The 4-line kites are relatively higher aspect than some (but not all) of the popular snowkites on the market. We are not planning on promoting them for water use but expect some enthusiasts will no doubt use them that way.
FZ : Do you think that there is a future for foil kites in waves (some of us tend to think yes but some R&D would be welcome for improving what is available at the moment as wave riding has specific needs).
BH : Far be it for me to say something is impossible but my sense is that it is a tough problem due to the complexity of the bridles, inlet valves and risk of crashing in the white water. Lack of structure seems like a primary limiting factor both while flying and in the case of a crash. I'd be interested in hearing the thoughts of the riders using foils in waves and where they see need for improvement before making an engineering analysis regarding a solution. In the meantime, my hat is off to those using them in waves!
FZ : Foils work fine in waves. New generations of foils do relaunch really fast and their soft structure can also be an advantage in the surf, because they tend to float above the white water. This said, a kite dropped in the surf has always a chance to be ripped off, and foils are no exception. At the moment, there are no production foil kites purposely designed for wave riding. Foils perform well but there are trade-offs which are not made for wave riding but with something else in mind. The challenge would be to build a foil kite that turns quick and tight with a constant pull (this is doable as concept air from Canada as for instance very interesting closed-cells prototypes - Peter Lynn chargers are also very quick and agile but some may argue that the kick in power they deliver when they cross the window is not very good for wave riding), that has a good depower (the system used by Concept Air and flysurfer that changes the arc of the kite is very good to that respect) but which is developed to be a production kite - so user friendly enough (this means stable enough for experienced riders - flysurfer kites are very stable for instance) with a fast relaunch (again flysurfer kites are very good to this respect). The main challenge is to put all these characteristics in one foil kite designed with no other thing in mind than waves (and traveling because foils could be very light and small companions of surfboards + small sizes wave foilkites could be interesting for snowkiting too). At lesFoilz.com we hope we plant some seeds in that direction.
BH : My sense from what you have said is that the primary deficiency of existing foils in waves is the character of the turn vs de-power. This is the same problem we encountered in developing the Method. Also, since foil-borne wave riding is a small segment of the market, the specific wave riding needs are probably being lost or diminished in the face of other more desired characteristics. That said, I do not believe a sweeping, controlled-power turn (where initiation is quick but with fixed or increasing radius) is undesirable to the general market. Rather, perhaps it just does not exist - at least so far in the kites brought to market. Our prototype testing has shown it is possible but requires some sensitivity on the part of the pilot/rider to not over-control the kite into a decreasing radius pivot turn. I believe this could be prevented by a limited control input system where the rider pre-determines the extent of deformation available. IMHO, part of the problem is rooted in how a typical foil control system deforms the kite to achieve turning and de-power. I personally like the way a 2-line foil turns in this regard and believe it may be ideal for down-the-line wave riding. The problem then becomes de-powerability because a too-powerful turn will rip the rider off his edge or board. Perhaps there is some room for R&D in this area.
FZ : You told me that you were currently in Hawaii for some testing with Felix Pivec. Could you tell us a bit more about this? In particular, on the next evolutions for your wave kites.
BH : We had a number of kites to test - not all entirely wave-oriented. Our recent test line-up included:
1) Pre-production Method V2's to finalize bridles and check other details for production.
2) Combat V2 prototypes with varying materials and canopy seam configurations for visual graphics. This is necessary as materials/printing and seam configurations have an effect on performance. It is not unusual to make subsequent changes in follow-up protos at this stage,
3) Element 11sqm prototype for comprehensive testing of all aspects for future development. This is the preliminary step on the way to a new model.
4) 2 and 4-line foil testing.
Felix and I test all of the kites before submitting them to HQ in NZ. Most models are then also tested there by Marc Jacobs and other Switch staff and riders. Our testing normally extends 1/2 to a full year in advance of release with several rounds of protos going back and forth from Hawaii and NZ as the effort progresses.
FZ : Thank you very much Bill for your time and answers, and for giving us the opportunity to see what's coming next!
Stef for LesFoilZ.com
LesFoilz (FZ) : Hi Bill. You are nowadays the designer of Switch kites but you have a long history in kite design and, more generally, in sail design. Those of us who followed your interventions on kiteforum may know some of your personal journey and career (for instance, the 3 struts kite project) but that would be nice if you could give us a short bio - in particular for our readers who only read French.
Bill Hansen (BH) : From an early age, I've had a natural interest and aptitude for things that fly or are driven by the wind. Kites, model aircraft, sailboats and boomerangs were always under construction with growing sophistication. My father had several airplanes and I learned to fly sitting on his lap and later earned my pilot's license at the minimum age. As a Junior High Student, I won the Illinois State Science Fair with a wind tunnel project entitled 'Facts of Flight' in which a tethered model plane could be actively flown. At University, I studied Applied Physics and after graduate school, I worked at UC Berkeley as a Research Associate on a Superconducting Electromagnetic Airborne Geophysical Prospecting system which was basically a large metal detector hanging from a helicopter. During that time I raced sailboats, flew airplanes, participated in skydiving and eventually began windsurfing in the early days of the sport with my own self-designed and built high-aspect fully-battened sails. After 5 years at UC Berkeley, I started a windsurf sail company named "Windwing' which grew into the largest US-based windsurf sailmaker. During that time I competed internationally in Speed sailing, windsurf course racing and slalom. Eventually we expanded to high performance stunt kites and set the standard for them which to some extent is still evident today. Around year 2000, I sold my interest in the company and became an independent designer/consultant for aerodynamics, kites and sails and have worked in this capacity for a number of brands and projects both inside and outside of the kiteboarding field. I also actively participated in open source kite design forums as a matter of self-improvement to push the limits of technology. It has been said that "if you do what you love long enough, someone will pay you to do it." I am blessed in that regard to now be a part of Switch.
FZ : On LesFoilZ, we are particularly interested in wave riding, with or without straps. One of your intervention I was very interested in was when you were commenting on the behavior of the switch method on the edge of the wind window (for those of you who want to read the post, look HERE). My take on your argument was that you were saying, amongs other things, that a wave kite should be a performance kite, and that comes with trade-offs. Could you tell us a bit more about what you think makes a good wave inflatable kite or even what would be a perfect wave kite, regardless of technology ?
BH : As a competitive sailor, the importance of upwind performance is obviously well-known. As an avid waverider and surfer, I found getting back to the line-up after a good ride (especially paddle surfing or with wind-blown current) was the worst part of the experience because of the time lost to the actual surfing. To me, a proper wave kite should go upwind extremely well if for no other reason than to get back to the line-up as quickly as possible. In addition, if the kite can operate well at the edge of the window, a larger range of motion is available to the rider to put the kite in an optimal position. Finally, kites that are capable of flying far to the edge also typically de-power well due to their ability to fly at low AOA (angle of attack.) But, that is not all of the equation. The final performance criteria for the optimal wave kite (other than re-launch and de-power) is fast turning without the loss of power and good drift down the line. We also wanted a powerful kite for the size because smaller kites are simply more maneuverable (and fun.) It is easy to make a kite sit back and turn fast in a pivotal power-losing way and there are many on the market. But, our vision includes a fast sweeping turn without losing power (which can be regulated by sheeting out.) Working with Felix in Hawaii, the criteria we sought were: Fast, non-pivotal powerful turning; excellent upwind ability; predictable drift; maximum de-power; easy re-launch; moderate bar pressure (so you can 'feel' the kite.) To us, this is what makes a great wave kite.
FZ : To what extent do you think you have achieved your goals? (I still have to try the method, it is on my must-do list)
BH : In the first version of the Switch Method (V1) we achieved most but at the sacrifice of higher bar pressure and tricky handling in gusty winds for less skilled riders. A kite which finds itself at the edge of the window is subject to natural instability due to the window expanding and contracting as the velocity and direction changes in gusts. In some cases. the kite simply finds itself beyond the edge of the effective instantaneous window. Subsequently, the Method V2 has been developed to allow adjustable bar pressure and better stability in gusts while overhead or at the edge. We believe we have retained the positives of the Method V1 while eliminating the negatives to open up the user profile to less-skilled, bar pressure sensitive riders. The response from our wave-riding Method testers has been unanimous.
FZ : With the increasing interest in wave riding, things are likely to evolve, and in particular the demand from the riders. As a brand close to riders (and to some extent made by riders), do you have some ideas about what would be the future of wave kites?
BH : At this point, even as idealistic as we can be, we find ourselves having trouble imagining how to improve it - at least for wave riding. We have already made some protos with differing parameters that perform very well but are not significantly better. Our immediate efforts and testing is with improved materials and construction which often impacts performance (both positively and negatively.) As the coming season progresses, we will listen to the riders and when we see a consensus of opinion, we will work to address them. This is how we see the best progress being made. One must also note that as the boards and riding styles evolve, the kites will follow (or possibly lead) the progress.
FZ : On lesFoilz.com, we are mixing (happily, at least up to now) tubes and foil kites. Some of us are even using exclusively foil kites in waves. Did you ever considered foil kite design?
BH : Yes. I have designed numerous 2-line, 3-line and 4-line foils for many years including the popular Slingshot 'B' series and others including but not limited to the Elliot Sigma Sport and Windwing Skyfoil models. At Switch, we are currently in production with 2-Line 1.5, 2.5 & 3.5sqm foils and nearing production on 4-line 7, 9 & 11sqm de-powerable foils. I have also previously made 4-Line ram-air 'C'-shaped sledfoils which were released to open source kite-design forums.
FZ : Wow … nearing production on 4-line 7, 9 & 11sqm de-powerable foils! You take us by surprise! Could you tell us more about these foilkites? Open or closed cells? Are you thinking about snow kiting with Switchkites?
BH : Switch is very interested in all aspects of kiting including snowkiting, buggy and landboarding. The 2-liners are open cells with closed wingtips to avoid collecting debris when dragging a wingtip. We view them as a progression from a fun 'trainer' in the 1.5sqm to a simple and basic landboard or snowkite in the 3.5 version (wind permitting due to square area.) The sheetable 4-liners we will be testing in the near future have a unique NACA inlet vent with interior valve flaps. To my knowledge no one has made such an inlet vent/valve in ram-air foils. If they do not work we will revert to the open-front inlet vents common to other foils and our previous prototypes. We are using a 2-pulley 'speed system' on the 4-liners for de-power / sheeting and our standard Switch control bar. The 4-line kites are relatively higher aspect than some (but not all) of the popular snowkites on the market. We are not planning on promoting them for water use but expect some enthusiasts will no doubt use them that way.
FZ : Do you think that there is a future for foil kites in waves (some of us tend to think yes but some R&D would be welcome for improving what is available at the moment as wave riding has specific needs).
BH : Far be it for me to say something is impossible but my sense is that it is a tough problem due to the complexity of the bridles, inlet valves and risk of crashing in the white water. Lack of structure seems like a primary limiting factor both while flying and in the case of a crash. I'd be interested in hearing the thoughts of the riders using foils in waves and where they see need for improvement before making an engineering analysis regarding a solution. In the meantime, my hat is off to those using them in waves!
FZ : Foils work fine in waves. New generations of foils do relaunch really fast and their soft structure can also be an advantage in the surf, because they tend to float above the white water. This said, a kite dropped in the surf has always a chance to be ripped off, and foils are no exception. At the moment, there are no production foil kites purposely designed for wave riding. Foils perform well but there are trade-offs which are not made for wave riding but with something else in mind. The challenge would be to build a foil kite that turns quick and tight with a constant pull (this is doable as concept air from Canada as for instance very interesting closed-cells prototypes - Peter Lynn chargers are also very quick and agile but some may argue that the kick in power they deliver when they cross the window is not very good for wave riding), that has a good depower (the system used by Concept Air and flysurfer that changes the arc of the kite is very good to that respect) but which is developed to be a production kite - so user friendly enough (this means stable enough for experienced riders - flysurfer kites are very stable for instance) with a fast relaunch (again flysurfer kites are very good to this respect). The main challenge is to put all these characteristics in one foil kite designed with no other thing in mind than waves (and traveling because foils could be very light and small companions of surfboards + small sizes wave foilkites could be interesting for snowkiting too). At lesFoilz.com we hope we plant some seeds in that direction.
BH : My sense from what you have said is that the primary deficiency of existing foils in waves is the character of the turn vs de-power. This is the same problem we encountered in developing the Method. Also, since foil-borne wave riding is a small segment of the market, the specific wave riding needs are probably being lost or diminished in the face of other more desired characteristics. That said, I do not believe a sweeping, controlled-power turn (where initiation is quick but with fixed or increasing radius) is undesirable to the general market. Rather, perhaps it just does not exist - at least so far in the kites brought to market. Our prototype testing has shown it is possible but requires some sensitivity on the part of the pilot/rider to not over-control the kite into a decreasing radius pivot turn. I believe this could be prevented by a limited control input system where the rider pre-determines the extent of deformation available. IMHO, part of the problem is rooted in how a typical foil control system deforms the kite to achieve turning and de-power. I personally like the way a 2-line foil turns in this regard and believe it may be ideal for down-the-line wave riding. The problem then becomes de-powerability because a too-powerful turn will rip the rider off his edge or board. Perhaps there is some room for R&D in this area.
FZ : You told me that you were currently in Hawaii for some testing with Felix Pivec. Could you tell us a bit more about this? In particular, on the next evolutions for your wave kites.
BH : We had a number of kites to test - not all entirely wave-oriented. Our recent test line-up included:
1) Pre-production Method V2's to finalize bridles and check other details for production.
2) Combat V2 prototypes with varying materials and canopy seam configurations for visual graphics. This is necessary as materials/printing and seam configurations have an effect on performance. It is not unusual to make subsequent changes in follow-up protos at this stage,
3) Element 11sqm prototype for comprehensive testing of all aspects for future development. This is the preliminary step on the way to a new model.
4) 2 and 4-line foil testing.
Felix and I test all of the kites before submitting them to HQ in NZ. Most models are then also tested there by Marc Jacobs and other Switch staff and riders. Our testing normally extends 1/2 to a full year in advance of release with several rounds of protos going back and forth from Hawaii and NZ as the effort progresses.
FZ : Thank you very much Bill for your time and answers, and for giving us the opportunity to see what's coming next!
Stef for LesFoilZ.com