Cory Bird's Symmetry

"You've got to see this airplane!" That's all I've been hearing from friends like Jon Sharp and Mike Melvill for the past couple of years. Cory Bird, a member of the highly talented team of mostly young people Burt Rutan has gathered around him at Mojave, CA, was nearing completion of his own original design homebuilt, I was told, and it was absolutely going to blow my mind when I saw it. This, mind you, from guys who knew I have been privileged to see and write about the best the homebuilt world has had to offer since the early 1960s. Well, folks, they were right.

Cory Bird's Symmetry

I've seen the airplane and it really is a mind blower. The airframe looks like it was sculpted out of some kind of soft, flowable material, then was put out in a strong breeze where its shape sort of streamed back until it no longer offered any resistance to the wind. Then when you have the opportunity to inspect it close at hand, you have to be amazed at the craftsmanship - and not be surprised it took nearly 14 years to complete.

Cory calls his masterpiece "Symmetry." He could just as well have called it "Slippery," but Symmetry is the more appropriately elegant term. When I see a homebuilt like this and learn that it is a first time project - especially when it is an original design - I want to know where and how the designer acquired the knowledge, skills and experience to produce such a work of art. These are capabilities that must somehow be acquired. It's not like a child prodigy of three or four who simply sits down at a piano one day and begins playing a piece of classical music he or she has just heard.

Cory is 45 and, as you are about to learn, has a very impressive background to bring to bear on work he does today. He was born in Portland, OR in 1958 and learned to fly in Cessna 152s in 1977 while attending Oregon State University. His father owned a company that custom built campers, trailers and various kinds of recreational vehicles on order, which was a cyclical business that closely followed the ups and downs of the nation's economy. Unfortunately, one of those down times came while Cory was in college, with the result that he had to return home and help his dad make it through until the next economic upturn. Cory had grown up with the company and acquired an array of mechanical and business skills - enough that when his father decided to move to Hawaii, he was ready to buy the company and manage it himself. Times were good for a while, but in the mid-1980s the RV industry hit another bump in the road. By this time Cory realized that feast and famine would plague him for the rest of his life if he remained in the RV business, so one day he simply packed it in, gave his father, who had returned to Portland, the keys and headed for Southern California.

That direction was the result of reading a book on Burt Rutan. Cory had always built things, but not necessarily things that were of great interest to him. He was a pilot and loved airplanes, so the idea of building airplanes struck him like a thunderbolt. It was something he had to do. The book had told of Burt's new company, Scaled Composites, which was launched to develop prototypes of often exotic new aircraft, so employment there became his ultimate goal. However, without any aircraft building experience, he was fearful of being turned down by Scaled, so he took a job with TASK Research in Santa Paula, CA, specifically to learn something about working with composite materials. Later that summer, after returning from the EAA Convention at Oshkosh, he applied for a job at Scaled and was hired as a shop fabricator. This was in August of 1985.

It didn't take long for Burt Rutan and his staff to recognize that they had a real talent on their hands in Cory Bird. Learning quickly and willing to take on any new assignment, he was given more and more responsibility and in 1990 was moved to the engineering department. Ultimately, he would begin serving as a project engineer on new designs Scaled contracted to develop, the most recent of which is the White Knight, the big launch vehicle for the SpaceShipOne rocket plane.

Over the past 18 years Cory has had a hand in quite a number of Scaled projects, some of which are well known to the general public, some that are known only in the aerospace world, and some that are still secret today. Among those that can be discussed were the Pond Racer; the Triumph business jet (which is mounted on a pylon in front of Scaled's offices today); the hard sail for the Stars and Stripes catamaran that won the America's Cup boat race; the Pegasus LT-11 launch vehicle for Orbital Sciences; SMUT, the big short field transport developed for DARPA; the Visionair Venture corporate jet; the Williams V-Jet; the Earthwinds gondola in which Larry Newman and others hoped to make the first non-stop balloon flight around the world; and the Global Hilton, in which Dick Rutan hoped to retrace his Voyager flight in a balloon. Included were a lot of drones, things involving stealth technology . . . but we can't talk about those.

Along the way, Cory was learning a great deal about composite materials and developing new ways to use them in aircraft construction. He even picked up a few patents in the process.

Cory Bird's Symmetry


When he began work on his own design in 1989, Cory had been working for Scaled for just four years and did not yet have the knowledge and experience he does today. Nevertheless, he did not hesitate to begin. His guiding philosophy is as follows: "You should never fail to start a project because you don't know how to do some aspect of the work. Start anyway. That forces you to learn. You learn how to do all the plumbing, about all the AN fittings, the fuel system, the electrical system, how the engines work. That's what's so cool about it."

Cory's first task was to find a place to build an airplane. When he moved to Mojave, there were no hangars available and he was living in a small apartment. Eventually, however, an old building in town became available and he was able to renovate it and build in some living quarters.

As originally conceived, Symmetry was a single place, low wing taildragger with a retractable main gear that swung back and up into the fuselage, a la Cessna 210. That was changed, however, as a result of a trip to Indiana to visit aerodynamicist John Roncz. Cory had carved a little model of the design and he hoped he could get John to critique it.

"He looked at it and said, 'Wow, what kind of foam did you use?' He was totally disinterested in the airplane. I finally got him to look at it and he said, 'You can do that, but your wing-to-body intersection is going to suck. You'd do better with a mid-wing.' I had already started building the fuselage, using Burt's moldless construction technique, and had even had a canopy made, but when I got home, I cut it up, took it to the dump and started over. This time, I decided on a mid-wing airplane with a fixed gear - and this time, I decided to build a plug and do a molded fuselage. I did all kinds of little samples to see what would make the lightest layup and finally ended up using a sandwich of fiberglass with a quarter inch H45 Divinycell core. The longerons were put in and taped over after the outer shells were assembled.

"With the fuselage reshaped, of course, a new canopy had to be made. I got in a hurry and made the first plug too thin, so that by the time the company that forms the canopies got around to using it, it had shrunk enough to ruin the optics. The next time my wife, Patti, and I built a much thicker plug, post-cured it for an entire weekend at 200° and spent two months body working it to ensure perfect optics. It was quite an experience, but the first canopy pulled off the second plug was a good one."

Symmetry's plus or minus 10G, one-piece wing was built just like a Long-EZ wing - hot wired out of two pound polystyrene, with an S-glass spar and outer skins. The most difficult part of the wing construction was gluing up the hotwired foam pieces in perfect alignment. This was doubly important to Cory because in addition to wanting a perfectly straight, wave-free wing, he wanted the trailing edge to flow smoothing into a raised accent line he had molded into the fuselage that extended back toward the tail. It was a time-consuming, tedious job, but, needless to say, he achieved his goals.

The airfoil section Cory chose is somewhat of a surprise, considering all the exotic, computer-derived sections that have been used on Scaled airplanes. "All those airfoils were closely held secrets at the time, in the early 1990s. I didn't want to intrude on anybody by asking them for a free airfoil and I didn't want to steal one, so I looked at what I thought my cruise was going to be and where the drag bucket was and I opened up a copy of Theory of Wing Sections and chose a NACA airfoil that appeared to have the lowest drag at this coefficient of lift. That turned out to be a 64212."

Symmetry's T-tail was not a part of its original design. The horizontal tail was built and installed in the tail cone in the conventional manner before Cory decided he did not like the looks of it there. It made the fuselage look too short, he thought, so he decided to place it atop the vertical tail. That definitely enhanced the sleek look of the airplane and with the endplate effect, probably increased the effectiveness of the vertical tail. The change did, however, make it necessary to thicken the vertical fin, both for the added strength needed for a T-tail and room for the elevator actuating mechanism.

Cory built up his own composite landing gear over a particle board former. It's all S-2 glass and high temperature resin, with an overlap of carbon fiber to better resist torsional drag loads. Cleveland 5:00x5 wheels and brakes with low profile tires were used, and gear leg fairings were made for streamlining and enclosing the brake lines and fuel vent lines. Symmetry was on its gear and beginning to have the various systems installed in the mid-1990s when time out was called to attend to family matters. With kids in high school playing sports and engaging in other activities, it was time for the parenting role to take precedence over the airplane for a few years. About the only thing accomplished on the airplane during this period was the building of the engine mount for the Lycoming IO-360 Cory had purchased.

During this hiatus from airplane building, the Birds had moved several times, first to larger homes, then, with the kids gone, back to a smaller one where Cory rebuilt a shop in the back where Symmetry could be finished.

Patti Bird has had much the same career as Cory. They both had previous marriages and both came to work for Scaled Composites at about the same time. She also started as a composite fabricator and worked on many of the same projects as Cory. She was one of the key persons on the development of the wings for the Orbital Science Pegasus and eventually became the program manager for that continuing program, as well as many others in succeeding years, including a current secret program.

Patti helped me on all the composite parts of our airplane. She is a much better laminator than I am. She has smaller hands and can reach things better than I can. Symmetry started out as a single place airplane, but after all her help, I came to realize that just wasn't fair. Fortunately, back in the beginning of the project, I had asked one of my friends at Scaled for help in structures and he said, sure, but only if I would make the cockpit big enough for him to fit in. He's 6' 6" so the cockpit was made way bigger than I needed in a single place airplane. This made it possible to add a seat behind the pilot. We mocked up a bunch of seats, with different inclinations of the seat backs, sat in them for hours and eventually came up with a really comfortable configuration for both of us. I reran the CG numbers and we were still in the envelope, but near the aft limit. I told Patti she could not gain an ounce in the future - but, actually, we can easily add ballast if we need to."

The control system is all push rods, with machined bellcranks turning in ball bearings. "The hardest thing about a composite airplane is that when you put in the flight controls, there is nothing to grab hold of. You have to build all sorts of attach brackets and bond and tape them in place, and that can take as long as it does to build the basic fuselage. As a result, I came up with a common bracket I could cut at different angles and radii and they saved a lot of time."

Electric pitch trim, driven by a MAC servo, was installed, but needs to have stiffer springs, Cory says. A mechanical roll trim system was also installed, but he thinks that once he gets it dialed in, it won't need to be adjusted again. The control surfaces were built using the same moldless/hot wired core technique as the wings, but were skinned with carbon fiber. The plain flaps are attached with piano hinge and are actuated by a torque tube. All the control surfaces are balanced 100%. "That was a real chore because the paint adds so much weight. I used horns to balance the elevator, but the rudder and ailerons are mass balanced along their leading edges."

The original retractable tailwheel was retained, even though a switch was made to a fixed main gear. It utilizes a Long-EZ nosewheel retraction mechanism and an S-glass strut. It includes a locking mechanism, with a lever on a console in the cockpit. The hole through which the tailwheel retracts also serves as access to the bellcranks for the tail surfaces. Overall, Symmetry is a small airplane, and with no way to put fuel in a solid foam core wing, Cory had to make use of every square inch of space within the fuselage. He solved his fuel tank dilemma by building two saddle tanks, one on each side outboard of his legs. Big hunks of foam were shaped to fit the available space, then had three ply skins laid up on them in pieces.

"Once you get the layup done, you put a piece of plastic over it and squeegee the surface. That way you push all the bubbles and excess resin out to the sides and you get a perfectly sealed laminate. You don't use a vacuum bag and suck all the resin out of it. After all the pieces were put together, I taped the corners with a couple of extra plies so the tanks wouldn't leak."

To fill the tanks, Cory made a single hole in the top of the fuselage, just behind the firewall, through which a filler pipe was installed that branches down, left and right to each tank. With the fuel tanks on each side of the fuselage, Cory had to place the rudder and brake pedals between them, with a clever arrangement of levers to actuate the brake master cylinders which are mounted vertically on the back of the firewall.

The VFR instrument panel is all carbon and is contoured around the front and sides to make maximum use of the space available. Modeling clay, the use of which was new to Cory, was used to shape the side consoles that are actually form fitting for Patti in her back seat position. The seats, themselves, were designed for a nine G crash load, the same as the fuselage, so the seat belts could be attached to them. The front seat swings forward for access to the rear seat, and when swung back is held in place with sturdy pip pins.

The 200 hp Lycoming IO-360 came out of a Cessna Cardinal and was chosen because the fuel injector is on the front, allowing a low profile cowl. It was overhauled using all new cylinders and had a B&C starter, alternator and voltage regulator installed. A six inch prop extension was used and the propeller, itself, is a wood Featherlite unit that came from the late Bruce and Bonnie Tift's tooling. It was delivered without the urethane leading edges in anticipation of some tweaking to match it up with Cory's airframe. Unable to find a spinner he liked, Cory made his own. After bonding a length of steel tubing in a block of foam, he inserted it in a lathe and turned it down into a shape he liked - actually a quarter of an inch smaller than required. Next, he slathered on a coat of tooling dough (epoxy and micro balloons), and after it cured, turned it again to the desired dimensions. This tool was used to make a female mold, in which the actual carbon fiber spinner was laid up. A sort of lip was built into the spinner so the screws for the backing plate go in from the back of the spinner and thus are not visible from the outside. The top part of the cowling has to be removed to gain access to the spinner screws. The cowling itself is devoid of all but two visible screws. One screw on the inboard side of each air inlet frame (which fits so precisely you hardly notice it is separate from the rest of the cowl) is removed, the frame is pulled out, and the long piano hinge pin is exposed for removal.

The insides of the top and bottom portions of the molded cowling are finished and painted to the same high quality standard as the exterior of the airplane. The outlets for the four exhaust pipes are not simply holes - they are molded tunnels that are intended to create negative pressure to aid the extraction of the exhaust and cooling air. Likewise the induction inlet, oil cooler inlet and outlet, battery box and cooling shrouds and baffles for the cylinders are molded carbon fiber parts. Complex, swoopy plugs were made for each part, then molds, then the finished parts. Cory probably spent more time on his oil cooler inlet and outlet alone than most homebuilders spend on their entire cowling. A stainless steel firewall polished to a mirror finish and chrome valve covers complete the glittering, jewel-like engine compartment.

From the very start of the project, from the plugs to the molds and to the finished parts, every effort was made to make the airplane as straight as possible . . . "straight" being the composite builder's term for perfectly contoured and ripple free. Throughout the process, Cory bathed the parts he was working on with fluorescent light to show up the faintest flaw. He used a little micro fill where needed and used long sanding blocks to create a final ripple free finish.

Next came what Cory calls a resin wipe. After going over the surfaces with 36 grit sandpaper he spread on a coat of pure resin, then immediately began squeegeeing it all off. With a little time for cure between applications, this process was repeated five times, leaving just a film of resin maybe two or three thousandths thick, filling every 36 grit scratch and all the pin holes. That was followed by wet sanding with 150 grit, then a coat of DP-48 epoxy primer and a guide coat of some color - just enough to see when it is sanded off.

Cory liked the yellow Volkswagen is currently using on its cars, so he chose that for Symmetry. He used acrylic urethane - duPont's base coat/clear coat system. The base color coat, he says, is a no-brainer, except that yellow does not cover well and required more coats than he expected in places. The real work comes with the clear coats, which require repeated sanding and, eventually, buffing to get the glass-like shine being sought. Cory started with 600 grit paper, but soon switched to 1500 to avoid hard to fill scratches. It took a lot more sanding with 1500, he says, but the resulting finish was easier to buff out.

When finally completed, including a set of sleek wheel pants which would be left off for the initial test flights, Symmetry was found to have an empty weight of just 959 pounds. The airplane was ready to fly in early April of this year (2003), shortly before the unveiling of Scaled Composites' new manned spacecraft program - but then the infamous Mojave winds began to blow. For two solid weeks, right up to and including the Friday of the White Knight/SpaceShipOne debut, they howled through the day and night. About 3:00 a.m. the following morning, Saturday, April 19, 2003 however, Cory was awakened by the sound of . . . nothing! The winds had died. At daybreak he was at the airport rolling Symmetry out into a bright sun. By chance, Mike Melvill was also out early and wanted to know what Cory's intentions were. A big production, with all his Mojave friends, lipstick cameras in the airplane, video cameras on the ground and in chase planes, had been planned for the first flight, so this morning Cory only planned to do some high speed taxiing, maybe getting the tail up.

A veteran of many first flights and all kinds of flight test work, Mike said, "You need someone out there with you, because if you are going fast enough to lift the tail, you never know what will happen." Sure enough, on his second run, Cory found himself airborne, and with the airplane feeling stable, he pushed in more throttle and climbed out. Mike was right behind him in a Beech Duchess - with Patti along video taping the event - but could not begin to keep up with Cory in the climb to 10,000 feet. Once there, Mike talked Cory through a rather complete test card and, finding everything functioning normally and the airplane handling beautifully, they began spiraling down for landing. It was then that they got the only bad news of the morning - the Mojave tower reported that the wind was picking up again and was already at 20 knots! Cory chose Mojave's longest, widest runway for landing, despite the fact that he would have a crosswind component, and came around base at 120 and slowed to 100 on final, shooting for 85 over the numbers. It was bumpy on the roundout and he bounced pretty hard and high on his first touch down attempt. Shoving the power back on, he went around . . . and got down safely the second time.

Now, what are the odds of having the first flight of an airplane that had been under construction since 1989 take place on the very morning that Golda and I just happened to be in Mojave, California - a continent away from our home in North Carolina! I was standing on the ramp with camera in hand when Cory taxied in and took the pictures you see here. Sometimes you just get lucky!

Although both Cory and Patti have intense work schedules ahead of them at Scaled this spring and summer, they hope to have Symmetry at Oshkosh in late July. Look for it there, because my message to all of you is the same as I have been hearing for the past couple of years . . .
You've got to see this airplane!

Cory & Patti Bird

POSTSCRIPT - Fall 2004

With Scaled Composites' manned space program taking an ever-increasing amount of his time, Cory only managed to fly Symmetry about 31 hours over the next year and a half, which included the 25 hours of test time assigned by the FAA.

"I would fly it, then pick a project to improve it that would take a month or two to complete. I finally got the retractable tail wheel and its little clam shell doors working properly, and I had to rebuild the exhaust system to keep it from cracking. The biggest job, however, was repitching the propeller. I could only go about 180 knots before it would be over-speeding the engine. I did some calculations and figured that I needed about 13 more inches of pitch. I started grinding on the blades and added six inches to the diameter, then covered it with carbon fiber and clear urethane. Now at full power and 2,800 rpm, I get about 240 knots. I picked up 60 knots with just that one modification, but that was another couple of month's work. I also added some fin area below the tail cone. Full flaps tended to screw up directional stability when really slow, so the added fin fixed that. From the beginning, the engine has performed flawlessly and cools really well. The oil temperature never exceeds 180 degrees and the cylinders stay at just over 300 degrees. I can probably gain a little more speed by choking off the inlets a bit."

When Cory departed for the 2004 EAA Convention at Oshkosh, it was the first time Symmetry had ever left the Mojave Airport to land somewhere else. He took the southern route, in short legs with overnight stops at Tucumcari, NM and Tulsa, then spent time with friends near DeKalb, IL before flying on to Oshkosh. Once there, the Homebuilder's Headquarters crew parked him just outside the flightline entrance arch and roped off the airplane because they knew it was going to be mobbed by EAAers all week. They were right - the airplane was the sensation of the Convention and no one who saw it was surprised when it was named the 2004 EAA Grand Champion-Plans homebuilt. Cory was also awarded the Stan Dzik Memorial Award, which is for technical innovation. Cory's plexiglass solenoid safety shield garnered that award.

After flying home by the same southern route, Cory continued to put time on Symmetry, often flying chase for Jon Sharp in his new NemesisNXT racer.

Over the Labor Day weekend, Patti finally got her first ride - and loved it. That ride was a sort of symbolic end of the 15 year developmental phase for Symmetry.

Of course, the following weeks of September were a countdown for the two historic space flights of SpaceShipOne, the first on September 29th and the second on October 4th, that would win the X Prize. With his responsibilities for the launch vehicle, the White Knight, Cory obviously had little time for sport flying, but with that great aviation milestone behind him and all the folks at Burt Rutan's Scaled Composites, perhaps he and Patti can finally begin to enjoy their Grand Champion Symmetry.