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The Way It Is/ Exploring the Delta Wing concept

by Gordon Kirby
If nothing else the Delta Wing Indy car concept has captured the attention of plenty of people both inside and outside racing. The Delta Wing is a much-needed attempt to revolutionize and re-energize Indy car racing. As Chip Ganassi says, it's a concept as much as a car. The Delta Wing is about entirely rewriting and recreating the rulebook and its unique ground-breaking shape has created plenty of debate both approving and disapproving. Indeed, the revolutionary concept has proved difficult for many people to get their minds around.

"It would have been very disappointing if everybody had just yawned and said, 'Boring.'," remarks Delta Wing designer Ben Bowlby. "But I was a bit shocked at quite how violent some of the negative comments were. I wasn't expecting it that strongly, but maybe that's a good sign. It means we raised people's pulse and triggered them to respond. It's good if the violent reaction of people looking at the photos results in them saying they've got to look into this a bit more and get to the bottom of it. Some diehard racing fans hated it, but a lot of seven-year old kids and many people who don't pay attention to racing saw it and thought it was as cool as hell."

Bowlby says the trend is moving toward the approval side as people learn more about the project.

"We've had a lot of feedback on our website and we've been seeing two very different reactions. We've seen some one-line hate mail and we saw some three-page love letters and as time goes on more and more people are coming 'round to listening and understanding that we're serious. More and more of them are saying they're beginning to see where we're going with this. But I have to say it's proving more difficult to communicate the story than we thought.

"We gave ourselves the cruelest challenge. We put a plain, grey racing car out there without any paint or decals on it and it's still had a huge impact. Let's see what it looks like when the team's individual paintwork and sponsor logos have been designed around the car.

"It's very exciting," Bowlby adds. "I must say I'm very happy because it's back to doing something that's edgy and difficult. It's engineering that's not just what we've been doing for the last goodness knows how long. It's a significant step and change so we have got to give ourselves the opportunity to really drill down to make sure we're doing something that's going to work in a wide operating window from Indianapolis at 235 mph on the straight to the Long Beach hairpin. The politics are complicated but that's just part of the typical motor racing world. So again, it's exciting and personally pleasing."

© DeltaWing Racing Cars
Bowlby's racing career started when he was in college in the UK. In 1985 Bowlby built a 'special saloon', a silhouette 1.0 liter motorcycle-powered car with an aluminum monocoque and composite body. Starting in 1986 Bowlby raced clubman's cars for six years while studying for his engineering degree. When Bowlby graduated Mike Blanchet hired him to work at Lola and he became Lola's chief designer in 1997. Bowlby left Lola in June of 2002 and spent six months helping GForce design the 2003 IRL car with which Ganassi's team and Scott Dixon won the '03 IRL championship. Bowlby joined Ganassi at the beginning of 2003 to lead the team's engineering projects in IRL, Grand-Am and NASCAR, including commissioning Ganassi's full-scale aero test facility in Pennsylvania.

"Ben has a remarkably wide range of experience," Chip comments. "He has experience designing cars for many years in different categories from Indy cars to Le Mans cars and working on our stock car program. Ben is a very qualified guy. Ben and his guys have worked on the thought process and development of the Delta Wing as a side project for about a year or so.

"It actually started out when Ben and I were talking about the motorcycle GP race at Indianapolis," Ganassi adds. "You could see the guys working the handlebars of their bikes in the corners and it seemed to be a good balance of power, tire and speed. But you could see the riders working in the corners and we were talking about how the drivers in Indy cars at Indy don't appear to do that anymore. The cars look like slot cars. They certainly aren't, but that's the way it looks.

"So we got to talking about how fast those 'bikes go at which point Ben pointed out to me with his engineering wisdom that if you have half the drag and half the weight you go the same speed with half the horsepower. Which got us thinking about why don't why do that in Indy cars? Go to half the weight and half the drag and we can do the same lap speed and achieve more efficient overall performance with half the horsepower."

Bowlby recalls these early conversations he and Ganassi enjoyed which led to the creation of the Delta Wing project.

"Watching the Moto GP bikes at Indianapolis reminded us how cool it is to watch a rider truly on the edge of balance, but in a visible way for the spectator," Bowlby remarks. "It's great to see those guys balancing their machines and we thought we've missed that in Indy cars. I watched the 2009 Indy 500 from the Southwest Vista with some of our sponsors. It was my first experience of sitting in the stands watching the cars and I was very surprised that with even a trained racing engineering eye how little movement you could see in the cars' balance.

"The cars were on rails and they all pulled the same rpm with exactly the same exhaust note for every car. They all did the same speed and there was no differentiation so it became a droning kind of thing that's the opposite of Moto GP racing. That made us realize we needed to make a car with a much broader performance envelope."

During Ganassi and Bowlby's discussions Chip took on board the futility in the excessive amount of drag required by the IRL's current IndyCar rules.

"Ben pointed out to me that an Indy car has more drag than a stock car right now!" Ganassi exclaimed. "I said, 'How can an open-wheel car have more drag than a big, full-bodied NASCAR car?' That's not the way it should be. But that's how we, as rulesmakers, have allowed it to be."

Thus began Ganassi and Bowlby's odyssey of exploring what an Indy car could or should be.

"Every constituency in the sport would like to see something different whether you're a car owner, a sponsor, a driver, a racetrack owner, a promoter, a car or engine manufacturer," Ganassi observes. "So we said, let's start with a clean sheet and answer all those questions and check all the boxes.

"Then simultaneously the financial crisis hit and reshuffled the deck. It's like our sport is under siege all of a sudden because it's either not green or renewable. People look at not just automobile racing but the automobile in general in this way. The automobile in general is under siege just as much as the sport."

Meanwhile, Bowlby quickly expanded the pool of information and resources required to properly explore and define the parameters for the Delta Wing.

© DeltaWing Racing Cars
"There were a lot of different inputs," Bowlby comments. "We signed up the teams under confidentiality agreements in April last year and we talked to people like Peter Gibbons and Tino Belli and Brian Lisles and many other engineers. We discussed our ideas, got input and looked at all of the different areas of opportunity.

"It's really about, 'If we threw the rulebook away, what could we do?' We met with Dr. John Melvin and talked about if we had a clean sheet of paper what would we be trying to do with the positioning of the driver? We attended conferences and took in many different sources of information to pull this thing together.

"We tried to make a car that had clean lines and was appealing to the eye. It's not a styling model. I think one of the things that's very important to get across is that this wasn't a styling exercise to create a certain look. This was all about us thrashing away to get to the point where the aerodynamic performance and the vehicle dynamics met the requirements that we had laid out.

"In this case, to use a well-worn phrase, absolutely form follows function," Bowlby continues. "There's nothing on this car that's there to look cool or to make it look a certain way. It's about creating the most efficient, best-handling racing machine that we can come up with to meet the requirements of going from the Long Beach hairpin to turn one at Indianapolis.

"At the moment the advanced engineering group at Ganassi has done most of the design work. That's a group I lead and we've hived off a small group and will be adding to them in the next few weeks as the funds become available. We've still got a lot of work to do but the basic concept is very robust and well-defined. From here on out it's about fleshing-out the details and getting the production engineering and coordination taken care of to pull the car together."

Adds Ganassi: "We've had a lot of people look at it in simulation. We've verified with different engineers that it will do what the simulation says it will do, and obviously everybody wants to see it run to see how it works out in reality. What we set out to do was that form follows function and we just kept looking at what were the answers to all those questions and checking those boxes off. We think we answered a lot of those questions."

A key component in Bowlby and Ganassi's thinking was linking the Delta Wing's basic parameters to the automobile industry's increasing search for more efficient engines and overall designs.

"We identified the trends in the automotive industry and the global social trends towards accepting higher efficiency and reduced waste," Bowlby says. "These were things we could bring relevancy to from what we do in Indy cars by having a far more efficient car in all ways, including using modern high-tech, high efficiency engines that the auto manufacturers are commited to and in the process of developing. 300 horsepower is going to be at the top end of the power output of a lot of three and four-cylinder turbocharged engines produced over the next few years. Everybody wants the performance but they also want the cruising performance for fuel efficiency."

The first trick was to substantially reduce the Delta Wing's overall drag coefficient.

"How do you get the drag out of the car?" Bowlby posed the question. "The wheels are currently 54% of the drag of the car at Indianapolis. If you enclose the wheels you'll end up with an ALMS-type sports car and that's absolutely not the identity that we're looking for. We want the jet fighter or the single-seater man and machine entity. So we started playing around for the sake of argument with the idea of removing the front wheels completely to see how much drag we saved and we saved an enormous proportion of the drag. That led to the Delta Wing concept where we had a very narrow front track and a wide rear track. So we developed a single-seater that's very different from what we have today and would in fact be a unique identity.

"The first question was, could it work? We did some simulation experiments and to our great suprise the vehicle dynamics were incredible. We thought we must be messed up here. But no, we weren't."

Doubtful of his computer models which suggested a three-wheeler would understeer less and steer more precisely than a conventional four-wheeler, Bowlby resorted to some old-fashioned modeling techniques to prove or disprove his theory.

"Sometimes computers can leg you up pretty badly," Bowlby remarks. "So I ran down to Hobbytown USA in Castleton here in Indianapolis. It's a great model shop and I bought two suitable high-performance, radio-controlled model cars. I modified one of them to have a single front wheel with the weight distribution that it looked like we needed from a simulation standpoint. I compared a conventional four-wheeled car to this Delta shaped three-wheeler and the three-wheeler was extraordinarily good. What we had seen in simulation actually worked in reality.

"It had less understeer and the fundamental balance is a progressive and stable oversteer condition. It's stable simply because you have the ability to respond with a very light front end to increasing yaw angles and catch the car. It has a very progressive and wide operating envelope. So we carried on with the simulation work and developed a very detailed strategy for the layout of the car."

The more Bowlby and his team of engineers looked at the Delta Wing concept the more they realized it would not only accelerate much quicker but would also be more stable under braking. This of course is the opposite of what conventional wisdom might suggest to many uneducated observers.

"What we discovered," Bowlby explains, "was that if we had the weight more rearwards in a straightline competition we can out-accelerate the current car because more of our weight is on the two rear tires that are powered and that gives us greater acceleration capabilities. Under braking we discovered that we had created a unique condition--in racing car terms--where more than fifty percent of the braking came from behind the center of gravity. Normally, more than fifty percent of the braking comes from in front of the center of gravity and that is an unstable condition where you have to be terribly careful not to lock the rear brakes."

These lessons were learned by the aircraft manufacturers more than half a century ago during World War II .

© DeltaWing Racing Cars
"The aircraft industry discovered this when they were trying to land fighters on aircraft carriers in World War II," Bowlby relates. "All the fighter airplanes in WWII had two big wheels underneath the wings and a tail-dragger at the back. It was very difficult to try and stop one of those in a hurry because they were in an unstable condition ready to lose control, spin and fall on their noses.

"Every aircraft after that ended up having the main undercarriage widely-spaced and placed further rearwards with a single nosewheel so you could haul on the anchors and have a stable condition under braking. Certainly we found under simulation that's exactly what you end up with--a very stable car under braking. So suddenly we had a car that out-accelerates and outbrakes the current car."

The Delta Wing concept also promises to be a much better handling machine than a traditional Indy car. Bowlby believes the Delta Wing will be much more capable of changing direction and more lithe in its handling in general than a current Indy car.

"We found that with appropriate tire-sizing we had very similar lateral performance characteristics with perhaps a bigger operating window from a yaw standpoint so that the driver could recover a higher yaw angle," Bowlby points out. "At that stage we thought it was looking pretty good and we started developing some aero for it. We used CFD to broad-brush develop an aero package."

One of the goals of the Delta Wing is to produce a car that is more raceable, more capable of running in close quarters and being able to pass other cars

"We wanted to create a car that would run in its own wake with minimal loss of downforce," Bowlby comments. "Here at Ganassi, we've done tons of work on the problem of running in traffic, particularly on the ovals because we can do almost nothing to help ourselves on the road tracks. But we've worked pretty hard on the ovals and learned a lot about the influence of the wing on the underbody and their interaction.

"We realized we had to get rid of the front wings because they were far too sensitive in terms of angle of attack and interaction with the underbody. That interaction between the wings and underbody is such a big part of the reasons why it's so hard to overtake when you're in the turbulence from cars in front and behind."

Thus the Delta Wing's basic parameters were established.

"We said we were going to have a very low drag car with about forty percent of the drag of the current car," Bowlby says. "With that drag coefficient 300 horsepower would get us over 230 mph at Indianapolis. If we were going to reduce the power by that much we had to reduce the weight by a similar amount so that we maintained our power-to-weight ratio. So that became the spec of the car."

Ganassi reiterates Bowlby's essential points.

"Our beginning mantra was half the weight, half the drag, half the horsepower, half the cost, and the same speed," Ganassi says. "That was our mantra. People want to see racing and passing. They want to see high speeds and they want to see performance. Our aim was achieve all these things efficiently with half the horsepower. We wanted to show that racing is about achieving the best possible efficiency. That's what racing was always about but we've gotten away from that."

Chip points out, quite correctly, that the basic layout of an Indy car, or even a Formula One car, has remained unchanged since the days of the pioneering Lotus 79 and Chaparral 2K ground-effect cars. In fact, the roots of today's Indy cars lay in the chisel-nosed, side-radiatored McLaren M16 'wing car' from 1971 and the iconic '72 Eagle, the first car to lap a superspeedway over 200 mph.

"We've essentially been racing the same car now in Indy car racing for twenty-five or even thirty-five years if you go back to the '72 Eagle and the McLaren from that era," Ganassi observes. "All we keep doing is making the tires bigger or smaller, the tunnels bigger or smaller, the wings bigger or smaller, and the engines bigger of smaller. But it's the same platform, the same car. Every iteration has been done so many times that everybody can tell you what any iteration will do before it hits the track."

The most common question about the Delta Wing is how the car will turn effectively and not suffer in general from a serious understeer problem. The answer, Bowlby says, lays in the much reduced mass and inertia of the front wheels.

"The reality is that the small front tires give us an incredibly responsive directional change," Bowlby explains. "This is because there is very little inertia and very little mass and the tires are tuned to that mass so we have an optimized, highly-responsive car.

"The fundamental physics is that the amount of mass that is supported by the front pair of tires is matched to the capacity of the front pair of tires. Therefore when you steer the front tires--and just to be clear the steering does come from the front--the mass of the front of the car reacts and a lateral g effect or pull takes place that is in balance with the mass of the car.

"The tire is designed and developed for the appropriate mass that it has," Bowlby adds. "If we put a bigger tire on the car it would be over-tired and the balance of the car wouldn't be there. We want the front tires to saturate in their capacity at about the same time as the rear tires saturate in their capacity."

Bowlby and Ganassi are delighted with Bridgestone/Firestone's enthusiastic support of the Delta Wing project.

© DeltaWing Racing Cars
"We met first with Bridgestone at Indianapolis back in May," Ganassi reports. "We wanted to know if they thought we were crazy and they didn't. They were very enthusiastic from the beginning. Bridgestone loved it from the start because it gave them a whole new angle of attack on tire development because of the front tires or the torque steering. All that was something they loved the idea of."

Bowlby expands on Bridgestone/Firestone's extensive technical support and commitment to manufacture and develop uncommonly narrow front tires with a four-inch bead width on fifteen-inch wheels.

"They have been working very closely with us on the vehicle mass properties and designing the tire with those properties in mind," Bowlby says. "They've also been working on the aerodynamic side so they know what to expect for aerodynamic loading. We've given them simulation of the data of the car going 'round street tracks and high-banked tracks and everything in between. They understand fully what their design parameters are so they can make a tire that achieves the car's performance requirements.

"Bridgestone/Firestone America is committed under Al Speyer's direction to manufacturing the tooling and production machinery to build this tire. They've never made a racing tire quite this narrow."\

Firestone expects to produce the first Delta Wing tires by the end of March or early April.

"They will go into the lab where they have a lot of tire test machinery and test the tire like they evalute any new tire designs," Bowlby says. "They will calibrate the fundamental tire performance model and develop it and prove in the lab that it can do the speeds and necessary performance. By the time we're ready to run in August they will have some options of tires prepared for us to go testing.

"The nice thing is the simulation work will get more and more accurate as the real tire characteristics are measured. We've made assumptions on what the tire characteristics would be from our simulation work. We scaled the capacity of a known Indy car tire so we're very confident that we haven't tricked ourselves in any way and we've shared that data with Bridgestone/Firestone.

"We could handle every other element of the car," Bowlby adds. "But there is no chance that we could handle making the tires. The tire guys are special and there are very few in the world that have the capability to make a racing car tire. But Bridgestone/Firestone have shown the world that they are absolutely the top group."

The Delta Wing makes its downforce entirely from its underwing.

"The downforce is created by a very simple shape underneath the car," Bowlby says. "It's just a contraction, or venturi, that makes a clean puddle of very low pressure pretty much under the center of gravity of the car. It's not very sensitive to ride height changes or to pitch angle, so you've got a very consistent downforce area.

"If you've got a front wing ahead of the front axle and a rear wing behind the rear axle, if you have changes on the flow on those wing elements their influence on the front and rear axles is magnified. If you have a very small change from turbulence or crosswinds you have a very big reaction on the car. It's a cantilever effect. But if you can make all the downforce very centrally in the middle of the car changes to the downforce aren't as radical to the balance and grip of the car."

The overall package should produce a much more raceable car.

"What we found was we could create a wake behind the car that was much less destructive to a following car," Bowlby says. "When it's one car length behind, the Delta Wing design loses less than half the downforce that today's car loses. So we're in much better shape as a percentage and we don't need to make as much downforce because the car weighs half as much. To achieve the same grip on the tires you only need half as much downforce. We have to knock a much smaller hole in the air. It's 300 horsepower worth of a hole in the air compared to 630 horsepower. So the momentum lost in the air is less than half."

Without the need for a rear wing to generate downforce or provide aerodynamic balance the Delta Wing enjoys a vertical tail fin to aid directional stability.

"Having moved the weight so far rearwards we were very aware that we wanted a high degree of yaw stability to increase the envelope a driver can explore in the middle of a turn," Bowlby explains. "So we needed to move the lateral center of pressure rearwards so that we gave ourselves an appropriate stability margin, known in the aircraft world as 'static margin'. That means when the car is in yaw you don't have a destabilizing moment or torque that tries to create even more oversteer.

"It's like the feathers on a dart. You have to put lateral force components far more rearwards on the bodywork than we have today. That's an area where we've done a lot of work on to try to improve the lateral stability of the car to help give us a bigger operating envelope."

Bowlby stresses that improved safety is a keystone of the Delta Wing concept with the driver located further back in the car. A dissimilar aim of the design brief was have plenty of space for sponsors logos and advertising messages.

"We didn't intend to create a car that looks the way it does," Bowlby says. "It's a result of meeting the criteria that we laid down and that included sponsorship space. It had to have a good amount of space on the body for sponsors and it had to be safe. The drivers' feet are far further rearwards than a current car. They're nearly twenty inches further rearward."

The Delta Wing's revolutionary aerodynamic parameters and lighter weight will also help make a much safer car.

"We worked on the rear impact structure," Bowlby relates. "By having a much smaller and lighter engine/gearbox unit and by making that an unstressed, non-structural member element in the chassis the car could absorb rear impacts very well. With the current car the very solid engine and gearbox can transfer too much of the impact through to the driver.

"We also did some side intrusion work by balancing the design of the nose, sides and rear of the car so that it wasn't a battering ram for side impact. We have sidepods on the current car but if you were to kick them hard you could put your foot through them. So we decided that just having sidepods wasn't really very helpful. What we needed to do was to take away the nose and tail battering rams that the current car has which really are a problem in T-bone-type accidents.

"The nose of the current car has to support a lot of aerodynamic loads so it has to be very structurally solid to absorb the crash energy. But for aerodynamic reasons it does this through a very small cross-section. But having done away with the wings we didn't have to support those aero loads. So both our nose and tail designs can be relatively 'soft' structures that are designed to absorb energy and not cause any intrusion through the chassis skin or sides."

The Delta Wing is designed to be powered by the new generation of high efficiency, turbocharged four-cylinder engines expected to arrive in the global market in the coming years. Ganassi and Bowlby believe a small capacity four-cylinder will attract a fresh wave of automobile manufacturers to Indy car racing.

"This car only needs somewhere between 320-350 horsepower and there are lots of engines out there with that amount of power," Ganassi observes. "The fact that you can drop any engine in this design is something we think is very attractive. Asking any of the car companies in today's economic environment to build a purpose-built racing engine is out of favor, so the car has been designed with a non-stressed engine. We think that has some merit in today's world. What's to stop Audi from calling Dallara or Subaru calling Lola and asking them to build one of these cars and let's go racing? That's what we hope to see."

Delta Wing's plan is to control power by a fuel flow restrictor.

"We're really trying to find a platform for the auto industry to showcase their future powertrains and we want to introduce the concept of fuel flow rate control," Bowlby explains. "For years motorsports has regulated power by how much air the engine can pump by defining cylinder capacity or rpm limits or carburettor size or air restrictors or turbo boost. It's always been about limiting the air and if you can develop the engine to get more air in there then you can lay the fuel to it.

"We're going to turn that on its head to achieve a very similar thing but in a subtly and importantly different way. If we only allow a certain amount of fuel flow to the engine we reduce the development of the airflow passage and the result, we think, is we're going to reduce costs very significantly because it's very expensive to develop airflow components. If you're going to change an intake tract it means a new cylinder head. If you want to change the valve lift you've got to redo the cam design and valve springs.

"What we want to do is limit the amount of fuel and make as much power from that fuel," Bowlby adds. "Then you won't be revving as high, which has good cost implications, and work on reducing friction and other esoteric elements are all about what's being done with road cars. So suddenly there's relevance because the technologies you're going to apply are technologies that need to be showcased for customer awareness in road cars. This will make us extremely relevant to the road car industry."

Bowlby also believes the Delta Wing's low drag and physical shape allied with its light weight and improved safety will be attractive to the automobile industry.

"In the coming years automobiles are going to be styled increasingly for minimum drag," Bowlby observes. "That's going to be the trend and we're going to see drag-reducing shapes that we didn't expect. We're also going to see structures to lighten the vehicles. The automobile industry is looking at lighter weight vehicles that are much more efficient so you need less power to achieve the performance everybody expects with less energy management issues when you have an impact."

Next week in part two of this analysis of the Delta Wing project I'll take a look at how the prototype will come to life in August. I'll also discuss Ganassi's and Bowlby's hopes and plans for the car to be built by more than one chassis constructor amid a fully competitive 'open source' environment.

Auto Racing ~ Gordon Kirby
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