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Physics of Windsurfing
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Windsurfing physics
»  I am amazed at how much physics is involved. Of course, it's not making my electromagnetism physics class any more interesting or helpful! I have a bundle of questions, but let's start with the general forces and the wide board revolution...   read on........

Hi Katie (and Eddy says hi also),

I think you're beginning to get the idea, namely, that the board/rig/sailor combination act as a whole when responding to forces of wind, water AND gravity. In addition, the size and location of these forces depend, in part, on adjustments the sailor makes in where he stands on the board and how he moves the sail. He, after all, is the only active link between the sail and the board. All the sail (wind) forces go through him to the board. The u-joint, while essential, is only passive.

Now to your questions:

Q: How do you know where to begin when creating new gear and modifying old ones?
A: Begin by asking the question, "What problem would it be nice to improve if not solve?" And then think of the problem as a puzzle for which there can be many answers, some better than others, or there can be no answer at all. These puzzles can be simple like "what do I do with all that extra outhaul line?" In this case, turn to page 80 of the current issue of WINDSURFING. Other more intriguing puzzles are usually "a puzzle within a puzzle within ......., etc." For example, the combination of 1) sailor standing 2) holding the rig by a wishbone boom and 3) attached to a surfboard with a universal joint, was the answer to the puzzle of "can a sailboat be steered without rigging, mainsheet or tiller?" That puzzle, in turn, came from a more basic one, namely, "can we get rid of the expensive, noisy, smelly, unreliable ski-boat and replace it with a sail?" The real answer to your question of where to begin -- board, rig, fin, sailor, etc. -- is, like a puzzle, you don't know until you're done. The most important tool here is imagination, patience and persistence. Education and experience help a lot as well.

Q: Why didn't the sport start with wide short boards for stability and for speed?
A: The early boards were mostly all based on wave surfing's tandem longboards, those with enough volume to stand on while uphauling. These had well developed low drag shapes at the time, and still do. They had a lot of rocker for maneuverability and were well adapted to the shape of an about-to-break wave. Hoyle (Schweitzer) did produce a short-wide board called (I think) the Starsurfer. Originally hoped to be fast, it wasn't; it was heavy, being made with a polyethylene skin and polyurethane foam, and slow because of rocker and a short waterline length. It rarely planed because the centerboard forced the sailor forward and the skeg was to small to resist HEEL without spinout when the daggerboard was retracted. The schools loved it, however, for just the reasons you can imagine. So, the first experiment in short and wide failed for lack of imagination and primitive technology. The benefit of a narrow board was and still is that it can be long and still be light and handy. In non planing conditions, the longer the better for low drag, a phenomenon well known to naval architects, yacht designers and long board shapers. The trouble is that neither naval architects nor yacht designers have any interest or skills in sail board design. And board shapers rarely have advanced technical training. Their "if it looks good, try it" approach has served them and the sport quite well. And I'm not sure but what it's the right approach given the complexity of the field as illustrated by the papers I attached to my earlier eMail. The current state-of-the-art in windsurfing owes more to the principles articulated by Charles Darwin and Adam Smith than those by Sir Isaac Newton. And I don't find that so bad, just frustrating.

Q: Can you shed some light on the physics behind your idea of the wider revolution?
A: First of all, it wasn't my idea originally, it was Svein's. I had some years earlier considered increasing board width but rejected it. The reason, now proved wrong, was that increasing width, while theoretically favorable to drag reduction on flat water, requires shortening the patch of water the board rides on. This shortening and widening both increase a tendency to pitch up and down in the choppy water that is an inevitable consequence of winds strong enough to plane. I guessed (rather than tried) that this poor behavior would dilute the improved theoretical hydrodynamic efficiency. Fortunately, Svein wasn't troubled by these theoretical reasons and went ahead anyway with GO. He brought one of the first units to Santa Barbara and asked me what I thought. Well, after a test ride and because he asked, I went back, looked at my assessment more carefully and concluded that I was almost certainly wrong. We then collaborated on the Formula series and the rest is history.

Q: Did you and Svein think that the GO board might affect the planing world as well?
A: We were almost certain from the beginning, especially when a GO board won the Canadian championship a few months later. Following this, nine of the top ten finishers in the world championship held in Thailand were the wide short Formula designs of Starboard. All of the competitive sailors had to be planing even in the rather moderate breezes off Jomtiene, Thailand. Yes, we thought it would revolutionize racing, and it has. But it also has revolutionized teaching and entry level sailing. Both of us are very pleased that this revolution has been adopted by almost all manufacturers now, to the great benefit of windsurfing as a whole.

Katie, this has been a very long answer to your questions. I don't mind and I want you to get benefit from it. However, your questions are very much like many others. And I have addressed the answers not just to you but to a wider audience. I hope you don't mind.

What do you think?

»  Hello Jim-Thanks for your response -- and I certainly don't mind that you generalize them for a wider audience. It brought up a few more questions...   read on........

Hi Katie,

It's OK. These are questions that many other people have. So it's worth spending whatever time it takes to add some light. Here goes:

Q: I imagine [flat rocker] has to do with surface tension and simply having a flatter planing surface. Can you elaborate?

A: Surface tension plays no role here because there is no free surface for the water to generate tension on. You may be thinking of skin friction between the water and the bottom of the board. In which case, it is one of the three main sources of drag on the board that together equal DRAG defined in the Windsurfing article. Another is called wave drag. The third is called drag-due-to-lift or simply lifting drag.

Friction drag is, as the name implies, the friction force of the water moving along the bottom of the board. The friction is caused by the water's viscosity. If the water were replaced by molasses (silly, I know) the friction drag would be much greater. The friction force is proportional to the board's "wetted area," literally the area of the board that is wet. Friction drag is also proportional to the square (!!!) of the speed through the water. This means that friction drag for the same wetted area quadruples when speed is doubled. However, happily for planing boards, the wetted area for a well designed and well sailed board reduces with speed approximately with the inverse of speed squared. So friction drag stays about the same no matter the speed once the board is planing.

Wave drag is caused by the board pushing water to the side, wasting energy and ending up in the form of lateral (side) waves that you can easily see forming a vee expanding to the side, originating at the point where the board first encounters the water. (There's much more to it than that. In fact wave drag is the subject that fluid dynamists have spent more time on during the last century than any other.) Wave drag is a complicated function of the shape of the immersed part of the board. Long slender shapes have generally lower wave drag than short blunt shapes. It is also a complex function of speed, generally increasing as speed increases. Its strength, however, can be estimated qualitatively by the height of the lateral vee waves I mentioned above. Tail rocker makes the board slower to plane and slower overall by increasing wave drag. The reasons for this are a little bit complicated and probably not well understood -- maybe even wrong. However, rocker certainly improves maneuverability.

Lifting drag is the consequence of the board pushing down on the water as it passes to produce what is called dynamic lift through a process that physicists call momentum exchange. The dynamic lifting force is proportional to the area of the planing surface, the angle it makes with the oncoming water and, again, the square of speed. (Very boring; don't bother trying to understand if you don't want to.) Dynamic lift is one of two sources of lift. The other, static lift, together with dynamic lift equals total LIFT, also defined in the Windsurfing article. When a board is said to be planing, most -- but never all -- of the lift is dynamic lift. And, to diverge for a moment -- but stay with me, this part is important -- static lift is equal to the weight of the water displaced by the hole in the water that is occupied by the board. The hole is roughly wedge shaped with the sharp edge forward, where the board's bottom surface first meets the water. This hole, for a planing board, varies with speed. At low speeds where there is little dynamic lift, the weight of the water that fills the hole approaches the total weight of the board, sailor and rig. At high speed planing, the board rises out of the water in response to the increased planing forces, i.e., dynamic lift. This is because less static lift is needed. Thus the hole gets smaller with speed, AND the wetted area reduces, explaining how friction drag stays about the same with speed. Now back to lifting drag: dynamic lift acts perpendicular to the bottom surface of the wedge and thus is angled back a small amount -- a few degrees. This produces a component of the dynamic lifting force in the drag direction. This is how lifting drag comes about, it's the portion of dynamic lift that tilts backwards. However, like friction drag, if the board is going at least fast enough to be planing, lifting drag also stays about the same no matter what the speed.

Q: The longer boards have less drag. My intuition says that the shorter waterline would make it glide on the water easier -- less resistance. What is going on that makes a board with a shorter waterline slower?

A: Well, from the answer to your first question you could probably guess that there's no simple explanation. Longer boards do indeed have less drag but only under certain conditions. Low winds and thus low speed is one. Long slender boards have lower wave drag (see above) because they push water to the side less aggressively. For the same displacement (the total of board, rig and sailor) the longer the board the smaller the mid-length cross section that's below the water. Hence the board treats the water more gently as it passes. However, the long board has somewhat more total wetted area for equal displacement and thus gives away some of the advantage it has from its slender profile. Once planing, however, a long narrow shape of the planing surface is less efficient hydrodynamically -- more lifting drag -- than a short wide shape like Formula. Also, a wide tail coupled with a deep fin allows the sailor to hike further out and create more DRIVE if he has enough wind and/or sail. None of this insight was known, much less incorporated into the Windsurfer Star (you may be right about the name). It had the short-wide concept right but lost it from its other (unsuspected and unidentified) design flaws.

Katie, even as complicated (and maybe boring) as the above is, it's still been simplified a very substantial amount. But if you're still curious, please don't hesitate to keep the dialogue going.

»  Hello Jim- how about one more question, then I think I'm set...   read on........

Aloha Katie,

OK, but it doesn't really have to be the last question even though I'm quite tardy in answering.

Q: Where is the c.l.r. on a planing board?

A: The c.l.r. (I use CLR since it takes less key strokes) for almost all types of boards, including especially a planing board, is very close to the geometric centroid of all fins (centerboards, daggerboards, skegs, whatever you call them) weighted by their plan (lateral) area and the location of their individual CLR. The actual location is an inch or so forward of the geometric centroid. The character of the shape of the fin (rectangular, swept, shark, etc.) doesn't matter very much so far as the location of its individual CLR, given that geometric center of its area is established -- though twist, induced by lateral pressure, can move it up and forward a small amount. While there are very precise rules on how to determine a fin's geometric CLR location, one can usually just look at a fin and guess close enough where it is by eye.

The lateral area presented by the board (a long shallow shape) does, in principle, contribute to lateral resistance with yaw, but in practice it is very slight because its shape is very inefficient hydrodynamically. Whatever lateral "lift" is present due to the board's yaw just leaks away underneath the board. Some sailors debate this and offer as proof that "railing" (rolling the board to leeward) increases the lateral "lift" on the leeward rail and helps going upwind. A more likely explanation of this well known effect is that "railing" moves the center of vertical lift (both static and dynamic) to leeward and thus increases the leverage the sailor can apply to the sail. This, in turn, increases HEAL and thus DRIVE unwind for a well trimmed and controlled sail.

I hope you are still interested enough to let these past explanations create still more questions. And, if so, you're welcome to continue the conversation.


Jim Drake
Jim Drake's vectors
»  I enjoyed Jim Drake's article "What Drives You" in the April 2006 issue of Windsurfing Magazine....   read on........

Dear Dr. Hanson,

I'm delighted you took the trouble to read and analyze the article from a technically critical perspective. The number of windsurfers that interest themselves in the physics of our sport is not great.

I'll have to admit that the terminology does not conform exactly to current aerodynamic or hydrodynamic practice. It was chosen to be 1) close to current convention 2) expressive of the force it represents [the term "skid" was created for this article] and 3) short.

You are, of course, quite right when you observe that orthogonal forces are by definition independent of each other. In this case, however, these are the orthogonal components of the same force i.e., the sum of the aerodynamic forces generated by the apparent wind, the wind sensed by the rig and sailor. For most interesting cases, i.e., close reaching to broad reaching, drive is a small fraction of heel and can't be generated at all without heel. I probably should have chosen my words with more care.

A remarkable feature of a planing windsurfer's aerodynamics is that -- for a well trimmed and properly selected rig and a skillfully handled board -- the apparent wind's angle to the direction of travel and the sum of the resulting aerodynamic forces stays approximately constant, from a close reach to a broad reach for any constant wind speed. This is the consequence of two technical phenomena: 1) The drag of a planing hull stays approximately constant over a large range of board speed and 2) the maximum leverage that the sailor can impart to the rig and still maintain control is also fairly constant with board speed. This phenomenon is explained a little better, by no means perfectly, in the attachment "Lecture PDF."

You may also be interested in the attachment "Board Forces copy." It is a series of analytic relations with which board forces, sail forces and fin forces can be estimated. All have sound theoretical foundations -- I believe -- but gain simplicity (and transparency) with certain empirical modifications.

I'd welcome your review of these two attachments.

Jim Drake
A friend and I are trying to figure out how a fin can give lift. Any clues?
»  The answer hinges on the definition you use for "Lift".In the technical field of fluid dynamics, "lift"...   read on........

The answer hinges on the definition you use for "Lift". In the technical field of fluid dynamics, "lift" normally refers to the force induced on a body (usually a fin, wing, sail or other foil) by fluid flow but at right angles to the direction of that flow; "drag" is the force in the direction of flow. Lift is often called the "normal force" for that reason. A more restrictive definition of lift is that it is the force perpendicular to the flow but also opposite to the force of gravity.Using this second definition, a fin doesn't generate lift unless it is inclined away from vertical in which case lift is proportional to the sine of the angle off vertical. A fin does flex sideways a little due to side forces and a small amount of that force is thus directed upwards.

If you are using the first and more general definition, lift is generated by what is known (from Sir Isaac Newton's time) as momentum transfer between the fin and the water. Water (or air in the case of sails and wings) is deflected by the fin as it passes by. (Fluid viscosity plays a crucial role in creating the type of the flow that makes momentum transfer possible.) The force required to "push" the water away -- since water has mass -- is the force felt by the fin. That force is proportional to the angle of attack -- yaw -- of the fin to the water, the area of the fin, the square of the speed through the water and other fin geometric factors. And, from a different perspective, the force on the fin is equal and opposite to the sail's heeling force -- the component of the sail's force that is perpendicular to the direction of travel.

I have a feeling that the above is way more than you wanted to know. But there's a huge amount of additional information, if you're still interested. If so, I'll do my best to answer any further questions.

The Hypersonic is my favorite because its deep concaves smoothes the ride and thus makes it fast. It has been replaced by the iSonic, also a great board. The future may see deep concaves incorporated into iSonic as well and I would again expect substantial improvements.

Hello again Jim,Bloody fantastic, that explains a lot to me. I suspected the fin would provide sideways force but not much vertical force. But i have 2 questions from what you said, if you have time to answer them.
First is why does a bigger fin help in lighter winds to plane earlier, and the second is if i had a fin that was flat on 1 side and foiled on the other, would it be really good in 1 direction (better than normal fins) and worse in the other?Thanks Jim, really appreciate your explanations.

»  I was serious when I said to contact me if you had other questions. So ...........   read on........

I was serious when I said to contact me if you had other questions. So ...........

1) The explanation is a little complex so bear with me. It begins with the physical fact that, when planing, a well trimmed board has roughly the same drag force over a wide range of speeds. This force is (also) roughly proportional to the total weight of the sailor, board and rig -- somewhere around 10 to 15%. This means that the sail's drive force in the forward direction has also to be about constant with speed to overcome drag. It also means that, for the same point of sail, the heeling force on the sail (perpendicular to the direction of travel) is also (roughly) constant at low or high speeds -- and thus -- the side force on the fin is also the same at low or high speeds. The side force a fin can generate is proportional to 1) its area, 2) its angle of attack (the angle of yaw with respect to the oncoming water) and 3) the square of forward speed. For complex reasons (that I can explain in a separate eMail if you wish) a fin works most efficiently, i.e., minimizes drag per unit lift, at a particular angle of attack that also is independent of speed. All this means that at slower speeds, the most efficient (least drag) way for a fin to resist the lateral force of the sail is just get bigger.

2) Yes, a fin with camber (one flat side and the other curved is one of many ways to develop camber) will be more efficient (less drag per unit lift) in one direction and less in the other. However, the optimum amount of camber is dependent on the three factors given above plus the amount of lift required to resist the sail's lateral (heeling) force. And the gain is not all that great. My view is that, except for unidirectional sailing such as speed sailing, cambered fins are not worth the trouble because of the wide variety of conditions (speed, chop, jibes, point of sail, etc.) the recreational and the professional sailor sees during a typical session.

Pray for wind,


How Did Monofilm Impact Windsurf?
»  My Views about Monofilm's Impact on Windsurfing.   read on........

Do you think monofilm helped or hurt the sport's appeal to recreational windsurfers?
I believe, on balance, that monofilm has had a very positive effect on the sport's popularity to recreational windsurfers. It's stiffness and low cost are qualities hard to find in any other sail cloth. It will be even more beneficial when the technology of glued seams replace triple stitched ones. And at some point, variable thickness monofilm will be able to adapt better to the large variations in loads and load paths. Finally, the UV problem WILL be solved, perhaps in some non-obvious way like easy rigging and derigging to shelter the sail in its bag.

Some say that monofilm reduced the visual and spectator appeal of the sport-do you agree or disagree? Comments?
Maybe, maybe not. There's still the board and the sailor, though they're not as prominent. And anyone really watching in real time will have binoculars. Like at horse races and, for big events, with an announcer, Otherwise it will be through the eyes of a camera, still or motion, for later viewing (with advertisement.)

In retrospect, what should we learn-if anything-through the monofilm example about how we introduce and market new technologies to the sport?
We should learn that experiments using new (or old) technology to improve performance should be broadly encouraged, letting the market place decide whether cost/performance is improved or not.

Are there other examples that concern you? Carbon fiber? Epoxy boards? Others?
None of those concern me and never have. Nor do any other technical innovations so long as they pay proper respect to the laws of the land and to safety. As I said above, the market place will do a fine job of culling out those that hurt from those that help. What does concern me is that the market has been telling us for some time now that spoks (probably misspelled) and triple forward loops (and other similar circus stunts) do little to encourage recreational participation. What they do is sell beer, suntan lotion, Red Bull and magazines but not windsurfing, completely missing the point that windsurfing offers, among many other things, a sense of self fulfillment at all skill levels. Most troubling is the false impression that windsurfing is a complex and difficult sport to learn. Great.
How wide is too wide?
»  Let's get to the guts: How wide is too wide? Is there a point of diminishing returns in regard to board width?   read on........

Well of course there is and the point of diminishing returns depends on what you're concerned about -- speed on a reach, broad reach and/or run, low end early planing, tactical maneuver, ease of jibing, pumping and the like. And there are other factors like the capacity of the x-ray machine at BKK or other international airports, the width inside your SUV, entry level instruction, etc. So it's a simple question but without a simple answer. Sorry.

Light-air boards appear to be getting shorter and wider. Why? And why haven't free-ride and wave boards followed this trend to the same extent?
Light-air boards are indeed getting shorter and wider because this allows them to plane earlier. This is because, among other things, the patch of water required for planing has a more efficient shape (lower drag for the lift provided) if it is wider and shorter. Fluid dynamicists refer to such shapes as having a higher "aspect ratio", the ratio of lateral span to average longitudinal wetted length. Free-ride and wave boards are -- in my opinion -- likely to follow this trend but perhaps less aggressively since both (think they) have the luxury of choosing better wind. The future may demonstrate the virtues of light wind attributes to them as well.

What caveats exist for consumers when considering light air, wide-body boards?
Be prepared to be ridiculed by the skinny board north shore Maui crowd in return for more water time at more places.

Have trends to short, wide shapes eliminated the light-air, sub-planing cruising element of windsurfing that originally helped make the sport so popular?
For the moment, yes. But only for the moment, that is, until short wide designs are developed that have at least adequate and perhaps very pleasing performance even when sub-planing. Originally, as you say, the sport grew from the pure pleasure of holding the wind in your hands and freeing yourself from the land. That changed when planing was introduced and the sport became more dramatic and athletic -- changes that were inevitable and from my point of view all to the good. These changes, however, displaced the zen of quiet windsurfing, a valuable quality that is appreciated by many but difficult to enjoy with single fin Formula style boards. All that may change if radical ideas, such as adding a retractable fore fin and a lateral mast track, bear fruit.

During a recent light-air board test involving boards of relatively the same volume, the wider boards seemed to hold the highest average speeds in marginal winds, yet gave up top-end speed to more narrow rivals as the wind conditions improved. What can be done to improve the top-end speed of wide boards?
One idea (not new) is to incorporate deep double concaves. This changes the shape of the patch of water the wide board planes on to lengthen the longitudinal wetted water line without reducing the efficiency (aspect ratio) of the planing surface. This smoothes the ride because it reduces the impact of the water's irregular surface -- chop -- on the bottom of the board. The quieter the board is the faster it is.

If the 100 cm width limit weren't in place for Formula boards, would you expect them to grow even wider? What would be the result?
I would indeed expect them to grow wider. Tests at Starbord have shown as much, at least through 120 cm. Imagine a 4' x 7' board! I can. And the benefits (except to obsolete all current Formula designs) would be as one expects -- earlier planing, quicker and maybe shorter "pump and go", quicker to the windward mark and maybe a little higher pointing.

Do you predict boards to continue to get wider in the future? What design innovations do you predict will complement this trend?
It's hard for me to predict that they won't get wider, just based on history and physics. But it's also hard for me to predict where it will all end up, namely, what will be the countervailing force. Today it's the bureaucracy -- Formula -- but that can and should change. It might be the "x-ray machine at BKK" but the x-ray machine problem and the air travel problem can be avoided as it is with all other forms of sailing. It might be the SUV but there's always the roof rack. My guess is that the limit will come by way of the requirement for longitudinal trim, that is, finding a place where the sailor can stand and counter the unbalanced couple between the sail's drive and the board's drag and still hold the board at its optimum angle of attack. (That's a bit obtuse, I know, but I'd put everyone to sleep with any better explanation.) One innovation to complement this trend could be to employ cavitating and/or ventilated planing hydrofoils to help longitudinal trim. (Well, you asked!)
Email to Olivier, Mar 7, 2006
Hi Olivier,It's good to hear from you. I hope your book project is moving well and, of course, I'm pleased to help as much as I can.

»  I think I ( -- we, including my wife -- ) visited Brittany in spring of 2001. Below are the answers to your latest question, again in bold.   read on........

Hi Jim
Thanks for your answers who help me a lot in my first part of the book.Jangada is Brazilian fisher old small craft, around 5.60 m, with a sail and 3 persons stand up, who move on it to change direction, helped by a saffron. This had a primitive concept of mobile sail with 6 mast implant on each part of the board, it was built in balsa and the sensations looked not bad, even if it wasn't question of planing, wishbone...For the "small story," a famous Brittany seaman, Charles Claden, today tug boat commandant, bought one in Brazil in 1975 and brought back to Brittany. Today, we can see few jangadas on Brittany nautique event like "Brest 2004" for example.

I have some precessions to ask you :

1 Can you tell me when Starboard will launch on the market "Serenity concept," is it ready for 2006 or for next year?
Gemini will be available through dealers later on this year, namely, 2006.

2 Can you tell me what kind of collaboration have you got today with Starboard, can we say designer consultant? How define your function today?
The main reason for my association with Starboard is my close friendship with Svein (Rasmussen, the owner and CEO) and also many other members of the staff. I don't have any formal position, so I think the best term would be "consultant." The help I give is a mixture of technical design, marketing, writing and lecturing.

3 About your kite sensations, what do you mean by "I'm terrible in it" (it has a double sense in French) : horrible or fantastic?
I mean terrible as in horrible. I don't think I've gone more than 100 meters without falling. I'm not discouraged so much as frustrated. I'll keep trying, however, though right now I think I have better uses of my limited resources -- time and strength.

4 What mean "CCM" fins, is it "stratified" fins like G10?
CCM stands for Computer Controlled Machining of materials like G10, stratified for stiffness or not. It also means Computer Controlled Machining of molds in which laminated fins can be formed. In both cases the accuracy required of a high performance fin can be obtained in no other way.

5 I'm very interested by the sending of the documents you spoke: early drawings of Serenity, Gemini and PowerFin, can you send them by e-mail?
Attached are some early designs for all three. Serenity and Gemini very similar to these attachments are likely to appear this year in dealers throughout the world. An earlier design of PowerFin demonstrated the principle of a laterally stroked, surface piercing foil. I was not satisfied with many features of that design. The one pictured here solves those problems (I think) but has yet to be built and tested.

It's a good way to show that you're not just active on the water, but even on the design, not just for windsurfing but for watersports, which is really in the spirit of the book, where we'll show that the main point is having fun on the sea, the support is not so important.

Hi Olivier, Answers to your questions are below interspersed with the questions:  read on........

1 When did you discover the existence of Darby and Chilvers research (I know it's after your invention) ?
Newman Darby's work, as it appeared in the US magazine "Popular Science," was shown to me by a German lawyer posing as a journalist in about 1976. Peter Chilver's narrative about his attaching a tent fly to a wooden mast and using two booms on either side of the sail and then mounting the mast to a hollow hull with the use of two interlocking eyebolts was brought to my attention during preparations for a legal action in the UK. It was first mentioned to me by a US patent attorney engaged by the UK firm in about 1980.

2 Are you OK to consider Brazilian jangada like windsurf ancestor (sailing stand up, different mast implants) ?
I'm afraid I don't know who Brazilian Jangada is. But I wouldn't be surprised that others would have thought of and perhaps built a small sailing craft that featured the sailor standing and, as I have said many times, holding the wind in his hands.

3 Your invention is nearly 40 years old, don't you thnik most of people have lost the feeling to ride without planing (and for this, classic longboards are perfect no) ?
Maybe, but maybe not. Most of the really good beaches, both fresh water and salt water, have winds in the 4 to 8 knot realm. Far fewer spots have the 12 to 16 knot and above where planing is really fun. Starboard is introducing a new concept named "Serenity" that may change the perception that planing is the only way to enjoy windsurfing. This will expand, by three to four times, the number of venues. And at the same time reduce the amount of sand and/or dust that one's girlfriend (or boyfriend) has to endure while one is out having fun.

4 If you should resume (I assume you mean summarize) in one word the years 1968-72, what would you say?
It was a "watershed" for individual sailing sports.

5 Did your relations with Hoyle Schweitzer definitely stopped since 1972 ?
Pretty much since 1978, though I've been in friendly contact with his son Matt. The ending of the friendship between the Drake and Schweitzer families is not something I'm at all pleased about.

6 Have you ever been in Brittany? What do you know of this part of France and his inhabitants?
I've been there only once to visit Bic. I was very taken with the beautiful scenery and the great food. And I'd like to visit there again when I get the chance (or an excuse).

7 Which windsurfer inspire you the bigger respect?
Of the ones I know well, there are two and I could not choose between them. The first is Robby Naish for his honesty as well as great skill. Both traits are rare in the windsurfing business. The second is Svein Rasmussen again for his honesty and his vision in creating the worlds currently most successful windsurfing and Kiteboarding company.

8 What have been the top 10 evolutions in our sport: harness, footstraps, sail design, camber, light materials...?
Not counting the u-joint and wishbone boom, I would list in no particular order: foot straps, harness and harness lines, full span battens, camber inducers, carbon fiber masts, stiff boom front ends (ala Streamline), flexible u-joint, CCM fins, wide short boards , Mylar sail material, laminated board construction, etc.

9 Did you make other creative designs in watersports?
Yes, PowerFin, a laterally swept fin for kayaks and similar craft.

10 Today you're 76 years old (is it exact ?), (That's right.) do you always practice windsurf or sailing sport, (as long as I can remember) what kind of contact have you got with the sea?
I still windsurf as often as I can, which turns out to be not very often. And back in the early windsurfing days, my family enjoyed cruising on our 40 ft catamaran, "Manu Kai."

11 Today: where du you live, what are your best hobby?
My wife, Sam, and I moved to Pfafftown, North Carolina from Santa Monica, CA in 2002. We really enjoy the quiet, the large secluded property (on a small lake) that Southern California could never offer us. Bicycling, like windsurfing, is what I enjoy as often as I can.


12 In 1962, when you have the idea with Fred Payne, to tract a board with a kite, you conclude that the traction wouldn't be strong enough to make a waterstart, (Water start wasn't on my mind. The difficulty I foresaw was that the weight of the kite would limit the drive because much of the kite's force would have to be devoted to just keeping the kite aloft.) don't you think that you could have been the kitesurf inventor and not the windsurf inventor if you had tried this concept in the water?
In a way, both I and another Frenchman (whose name escapes me now) did invent early Kiteboarding. There are numerous pictures of our designs in various magazines from the early 1980s.

13 Did you follow the work of Legaignoux brothers, two Brittany inventors of Kitesurfing?
Yes, very much. And once again, patent protection, greed and other unproductive motives have poisoned an otherwise fine sport.

14 Do you think Kitesurfing goes in a good way or follow the same excess of windsurf (small board, extreme move...) ?
I can't predict today. Unfortunately, it seems to be taking on the appearance of a stunt rather than a sport that appeals to a broad section of athletically inclined men and women. Kitesurfing will have to solve its two major drawbacks before it can generate broad appeal. It has to become much safer and it has to become simple and inexpensive.

15 Did you try Kitesurfing?
Yes, and I'm terrible at it.

16 Would you be attracted to come to live in Brittany (the wind, the sea, lots of space...) ?
Yes, I think I would very much like to live in Brittany -- for perhaps a large part of the year.

I have noticed Starboard e-mail you sent to me, but have you got some personal designs about windsurfer research that I could use to illustrate the book? It's always a good way to show an invention, in complement of pictures, Starboard perhaps have some of them but are you in position to send me these kind of docs?
Nothing comes easily to mind except, perhaps, the early drawings of "Serenity," mentioned above, "Gemini," a forthcoming tandem design and perhaps "PowerFin."

Let me know if these answers help and if you need more detail.

Jim Drake
Email to Ding, 2004
»  Hi Ding, At the conclusion of the meeting in San Diego you asked me to send you my views about the forthcoming evaluation -- let's call it
Torbole II.   read on........

First, Torbole II became necessary when the President of ISAF judged Torbole I to be a great disappointment, blaming a poor response by the windsurfing industry who he described as consisting of board builders -- now only one -- and marketers. The president went on to repeat that if the windsurfing industry failed to "get its act together" he might well recommend that the two Olympic windsurfing medals be withdrawn in favor of other disciplines. This contrasts inexplicably with the positive view reached by the Evaluation Team.

A logical step would have been to ask him specifically where industry and the Evaluation Team failed. No one did, leaving us to answer that question on our own and communicate it to the Torbole II participants -- ISAF and industry -- and hope Torbole II does a better job in the president's eyes.

Second, another class, the International Raceboard Class Association (IRCA), several months ago in its submission to the Events Committee proposed "that ISAF select a 'Hybrid' board" and that IRCA be "selected to manage the chosen equipment." Evidently the term 'Hybrid' associated with Olympic windsurfing equipment had been in play for many months before Torbole I. Accepting the IRCA submission would require that they alter the dimensions of their "box" which is currently 3400 mm minimum length and 850 mm maximum width. IRCA plans to do so at their forthcoming AGM. Z-Class was not advised of the 15 March deadline for submissions to the Events Committee and thus was not an option eligible for official consideration.

Selecting IRCA to manage the chosen equipment would have the substantial benefit of employing an organization with exceptional contacts and experience. This is because IRCA, Mistral One Design (probably including 'Evolution' Mistral One Design), Prodigy and Formula Windsurfing all have the same Executive/General Secretary. Watch out!

Third, windsurfing is culturally on a different planet from dinghy and keelboat racing. It has much more in common with snow skiing. Skiing and windsurfing are, at heart, recreational and social sports with yearly changes in equipment and fashion. Only a small percentage of skiers and windsurfers participate in racing. But skiing, unlike windsurfing, has its own federation, the FIS, that regulates, officiates and certifies events. Windsurfing depends on ISAF for those services.

Imagine the reaction if a fictional FIS -- in the interest of fair competition, minimizing costs to poorer nations, etc. -- were to require that all official ski races be run on identical white skis supplied by the event organizer of a design selected every four years by this fictional FIS -- none of who's fictional members are skiers. Imagine at the same time that these races are run on gentle slopes with "spring snow" as well as on steep icy slopes. This parable could explain why ISAF has not distinguished itself in its past choices of windsurfing equipment. The windsurfing community puts up with this because they like the publicity and need the money that Olympic participation brings. ISAF and the windsurfers both need to grow up.

Can or will Torbole II do something about this? It's possible but unlikely. The window of opportunity probably closed for another four years with Torbole I. Despite this gloomy outlook, however, I'd still like to help Torbole II succeed as well as it can. Four years will go by quickly enough.

Jim Drake
Letter to Burt Rutan, Dec 2004
»  Hi Burt,I want to thank you personally for taking the time for a very revealing interview and tour.   read on........

Hi Burt,

I want to thank you personally for taking the time for a very revealing interview and tour. I'm sure I got more out of it technically than the rest but their experience was no less appreciated since it's their work in progress. And we all shared the aw at the sight of the first true space ship.

I agree with you that space flight is an imperative for the human race and that we're only at the beginning. As I said, however, I think we're at a stage more like the Montgolfier brothers than the Wright brothers. In my opinion, we've yet to progress even as far as Santos-Dumont rounding the Eiffel Tower though progress came quickly after that as it may here as well.

My grandson Sean Fleming, age 14, was there also. He was thrilled to participate because he is inclined in the same direction as you and I. His mother (my daughter) asked me to ask you a very sensible question, namely, which universities in your opinion produce the most creative aero-space engineers while at the same time giving them a properly broad college education? In his case brains and funds are more than adequate. I'm prejudiced about the brain part but not the funds. Your suggestion(s) could prove exceedingly useful.

Finally, I'd be delighted to help you on your journey in any way I can.

Sincerely yours,
Jim Drake
Formula Quote for Dan Mangus
»  Aloha Dan, It all looks much too good for the Formula format in 2004. With one exception the support is genuine among the sailors, the press and the industry..   read on........

Aloha Dan,

It all looks much too good for the Formula format in 2004. With one exception the support is genuine among the sailors, the press and the industry. I think Neil put it best of all in his thoughtful quote.

But I don't trust bureaucrats and the Olympic Committee is one of the worst. Witness what happened in the site selection committee when a little favoritism and influence money was introduced. There are, without doubt, opposing views. What are they and who holds them?

On the other hand the press package you suggest will most certainly help and I'd like to help in any way I can. For starters, you are free to use part or all of the following quote:

"From the start I held the view that windsurfing competition (and recreation) was the liquid version of skiing where technology is selected by the participant and driven by performance with regulation held as close to zero as possible. Yet windsurfing accepted sponsorship on the world stage by the regulatory prone IOC and IYRU. I believe that it was a mistake to accept one-design and the Olympic triangle as a condition of entry. Access to the deep well of inovation that was responsible for the creation of windsurfing in the first place was blocked for this premier event. Windsurfing allowed itself to become just another boring elitest yacht race. To use a contemporary phrase, windsurfing shot itself in the foot on that one.

"It can be argued that after one of the largest world wide promotions of a new sport (selfserving to be sure), the Olympics effectively killed windsurfing's growth; participation leveled two years later. Even the patent's expiration could not reverse the trend.

"Fortunately, windsurfing is what windsurfers are -- not the reverse. Windsurfers at all skill levels know the wisdom of encouraging the kind of inovation that brought them the sport they love. And even more so at the pinnacles of competition, the PWA World Tour and the Olympics. Introducing the Formula concept, that is, allowing competetors and organizers the widest latitude in the choice of equipment and course, will energize the event itself and the sport as a whole as no other action can.

Jim Drake
Santa Monica, CA

"Caution: 'The devil is in the details' and great care must be taken in defining -- meaning undefining -- the Formula format to realize its promise. I have a sermon prepared for that one too."
Letter to Peter Johnstone about PowerFin
»  Thank you very much for your reply. I'll assume, with little fear of misinterpretation, that it is evidence of your personal if not commercial interest.   read on........

Dear Peter:

Thank you very much for your reply. I'll assume, with little fear of misinterpretation, that it is evidence of your personal if not commercial interest.

I should summarize PowerFin's current status to give you a better idea of where and whether Sunfish-Laser might participate. As the paper said, a number of prototypes have been constructed over the last three years, some here and some in Japan. These efforts have been supported by a consortium of two firms, JBS International Co., Ltd. in Japan and LAXON Corporation here in Torrance, CA. Both companies have informal ties to Yamaha as well as permission to exploit the U.S. and Japanese patent currently owned by Yamaha. The goal of the current experimentation is very much along the lines you suggest, i.e., simple, small, light, low price, roof-top, catamaran, one-man or two-man crew. The technical question is how best to combine power and control. The marketing question is where best to enter the price vs. quality scale. In both regards, an understanding of the Nova Scotian's fish tail system could be very useful. Thus, I hope you can retrieve one of their brochures (and send along one of your new design, Escape.)

Both JBS and LAXON are in this project for potential profit, not for the romance, and though we have no formal agreement, I feel a professional obligation to them. A part of that obligation is to make them aware of the potential your company might offer in developing PowerFin. I have started that already and any additional information would be helpful. I don't yet know how they feel.

For me, on the other hand, I am in this project for the romance and the joy of creating something that gives pleasure. (For that reason I prefer a fairly high position on the above mentioned price/quality trade.) I'd be unhappy if PowerFin were exploited without me, but for the time being, they have earned my trust. Time will tell.

I am very familiar with Greg Ketterman and his Trifoiler, though I'm not sure whether I have met Russell Long. It is indeed a technical tour de force. I am pleased, though a bit surprised, that its high price did not deter sales. But as you say, distribution works. My technical view at the time the Trifoiler was developed, was that high speed under sail favored planing lift, not foils. This is because cavitation becomes unavoidable much above 50 knots. The fact that all motor powered and sail powered speed records are currently held by planing craft is support (but not proof) for that view. I think that it is entirely possible that a variant of the windsurfer, small enough to be car-topped, could be competitive. Or, at least theory says it could.

Please write and let me know more about Sunfish-Laser.

Jim Drake
»  It has been about a year and half since we last corresponded. Since that time I've retired from Logicon/RDA though I still maintain a technical consulting relation with Department of Defense.And, of course, I'm still very involved with PowerFin.   read on........

Dear Peter:

It has been about a year and half since we last corresponded. Since that time I've retired from Logicon/RDA though I still maintain a technical consulting relation with Department of Defense.And, of course, I'm still very involved with PowerFin.

I can believe that the changes you've made to your company and the effort required to establish two new products in the market-place leave you with little spare time. None-the-less, I hope you can help me in a step I'd like to take in PowerFin's development.

The unique feature of PowerFin lies mainly in its propulsion. The current catamaran configuration, while attractive and well adapted to both sail and fin power, is not the only or even the most marketable platform for PowerFin propulsion. In fact, we mounted one unit on the transom of a 33 ft 6 ton sloop and managed to propel it at about one knot in zero wind conditions. It also allowed maneuver, though very slowly, into and out of mooring slips. The idea is to provide auxiliary propulsion for small to medium sized yachts when the wind fails. LAXON, the financial sponsor of PowerFin, has elected to narrow the development to just the oar to reduce the investment while perhaps widening the market to all boats under about 5 tons.

And that brings me to Escape. I would like to see if PowerFin can be mounted either on the existing gudgeons, with or without the rudder, or separately. If so, I'd then like to test it over a range of wind speeds, including zero, and wave conditions. (I currently test out of the UCLA Marina Aquatic Center's boat dock, with their permission.) However, I have seen only a few photos of Escape and very little of its specifications. Thus, I hope you can help in two regards. First, I'd like a more complete technical description, perhaps including scaled drawings showing the overall arrangement as well as the details of the transom. This would probably tell quickly whether the idea is at all practical. Second, assuming the first step shows promise, I'd like your suggestion of how to get a complete unit for modification and test. I'm sure there is a dealer here in So Cal, but I've been unable to find one.

On a different subject, we just spent three very charming weeks on New England coast, including Boston, Rockport and Booth Bay. So it is likely that we passed very near your location. We plan to return perhaps as early as Christmas but certainly by next summer. I would like very much for us to meet and exchange ideas on our mutual interests.

Jim Drake