Upscale ACME Spitfire
Against All Odds by Joe Isca
(as published in Launch magazine)
An Indiana rocketry club boldly embarks on a mission to build a 6X upscale of the A.C.M.E. Spitfire, an amazingly bizarre rocket. The result was a stunning flight at the National Sport Launch.
“Man, there ain’t NO way you can make such a crooked rocket fly.” That quote from the FlisKits A.C.M.E. Spitfire instruction manual describes the first thought that comes to mind when an incredulous person first sees this rocket.
Our story begins in the summer of 2005
Shortly after Dennis Watkins—a member of our Summit City Aerospace Modelers (SCAM) club—built his original A.C.M.E Spitfire kit. I was amazed at the attention that rocket drew at our launches. That kind of attention made me want to upscale the kit.
Over the winter months, Dennis built a 3X upscale of the A.C.M.E. Spitfire using six-inch diameter body tubes. It was at the spring 2006 SCAM launch in Winchester, Indiana that Dennis tested his unpainted rocket using an Aerotech J570 motor. That’s quite a test, but it turned out to be an arrow-straight flight with perfect deployment. The A.C.M.E. had earned a beautiful paint job and was taken to Amarillo, Texas for LDRS XXV (the Tripoli Rocketry Association’s annual national launch). As Dennis expected, the Spitfire was a real crowd pleaser…both before and after the successful J570 launch.
Planning the build
It had been about five years since Team SCAM members had built the now-celebrated N and then O-powered half-scale Honest John missile—and launched it in Danville, Illinois, and again at LDRS 21 in Amarillo, Texas. And now, with the National Association of Rocketry’s National Sport Launch (NSL) to be held in nearby Muncie, Indiana, what better time for a new club project? Twelve members agreed to upscale the A.C.M.E Spitfire, and Dennis was named project director.
Before the building began, we spoke to Mario Perdue, launch director for NSL 2007. We wanted to confirm the suitability of our special project and the AMW M2200 Skidmark motor that we hoped would boost the A.C.M.E. Spitfire. He green-lighted our proposal.
Now that we had the go ahead that we needed, Mike Law volunteered his workshop (and nearly his entire house) for our weekly build sessions and meals. Did I mention the meals? Thanks, Valerie Law!
We asked Jim Flis, the designer of this rocket, for his help with our 6X upscale. He was nearly as excited as we were with the project. Jim graciously supplied digital files for each of the eight different centering rings, the templates we needed to cut the peculiar body tube angles, the odd-sized and dissimilar fins, and the form used to construct the unusually shaped nosecone. With the upscaled files on hand, Dave Wyss took them to be printed on Orajet, a self-adhesive vinyl graphic material.
Let's start building
At one of our first group meetings, Dean Bobay, a former boat racer, suggested we use Okoume 9-ply Mahogany marine plywood to make the centering rings. Okoume is widely used in race boat construction because it has a high strength to weight ratio. Consensus was reached, and Dean ordered a four-by-eight-foot sheet. At the next build session, we affixed the Orajet outlines for the centering rings to the Okoume plywood. Cutting the rings using this method was quite straightforward.
Dean also suggested that for the fins we use a composite material called Tripanel Marine, a composite cardboard/phenolic honey-comb sandwiched between two pace panels of Okoume. Again, we agreed with Dean’s recommendation. The fin templates were attached to a four-by-eight-foot sheet of half-inch Tripanel Marine.
After the fins were cut, we needed to seal all of the exposed edges. We chose to do this by cutting rabbets into strips of Okoume to form T-shaped caps. Each of the T-caps were mitered, fit, and then epoxied into all of the exposed fin edges. Once the caps were in place, we covered the fins in three-ounce fiberglass. The edges were wrapped with an additional three ounces of glass.
The templates were very helpful in marking the body tubes. However, through human error on our part, they didn’t quite scale up correctly. Each body tube had to be adjusted slightly “on the fly,” and our center of pressure (CP) had to be recalculated. Once we were happy with the fit, the tubes were covered with one layer of six-ounce fiberglass.
We used the nose cone template to cut a piece of linoleum, and formed that into the shape of the cone. This linoleum form was then covered with one layer of 20-ounce fiberglass. Raka epoxy was brushed onto the entire surface area, and it was set aside to cure. A second layer of 20-ounce glass and a layer of 18-ounce woven roving glass were applied. When the cone had fully hardened the linoleum, template was removed. At this point we noticed a flat spot had developed on the nose cone. A batch of epoxy was mixed with phenolic micro balloons in an effort to build up and round over the flat spot. It wasn’t perfect, but close enough. Remember, this is a crooked rocket.
We didn’t want to limit the rocket strictly to 75mm motors. Who knows? Some day—maybe—this rocket would look great flying on an N, an O, or a P motor. (OK, we’re optimists.) Regardless, the six-inch tube gives us flexibility now and in the future. For now, we equipped the rocket with a 48-inch long motor mount adaptor that adapts from 150mm down to the 75mm for the M2200 Skidmark planned for the initial launch.
The next step n our plan was to build the conical fin can. It was constructed with centering rings epoxied to the 12-inch diameter tube. This unit was then inserted onto a six-inch diameter motor tube with large centering rings attached to it. To keep the weight to a minimum, four-inch thick staves of blue foam were applied along the length of the fin can. After carefully fitting and sanding the staves, two layers of six-ounce glass were applied. Before we permanently attached the fins (check out the weird placement), we took careful measurements to make certain the completed unit could pass through the door of the work area. Mike Law wouldn’t be too pleased if we had to rip him a new doorway. It was tight, but it would make it through. The fins were permanently mounted and two layers of six-ounce glass were run from fin tip to fin tip. Proper alignment of the all-thread rods and the U-bolts in centering rings 4 and 5 was a critical step in the construction process for this uppermost tube. Of course, it took our “engineers” about half a day just to figure out where to drill the holes in the centering rings and then to properly align the tubes. We saved this important step until the fir can and tubes two and three were completed and epoxied into position. That way we could be sure everything was as crooked as it was supposed to be.
Altimeter Bay
The altimeter bay and a compartment for parachutes are two elements contained within the nose cone. A specially shaped off-center centering ring attached to the nose cone holds the altimeter bay. A cutout from the ring allows for storage of the two main chutes inside the nose. To ensure the chutes (one for the nose, and the other for the body) would not snag on this ring, it was foam-filled and smoothed right up to the edge of the ring.
Charlie Humphries, our senior member and a retired engineer, worked closely with Mike Law. Together they planned and built an exquisite altimeter bay. These guys are noted for their meticulous craftsmanship. Dennis Watkins devised a method for placing the switches for the altimeter on the underside of the nose cone. They are easy to reach and don’t get in the way.
Inside the bay you’ll find an ARTS2 as the primary altimeter. With a rocket this big, and this crooked, we wanted to be sure we could deploy the chutes at apogee (or whenever), so a remote-controlled Missile Works WRC2 was chosen as the back-up device.
Now that the components for the entire rocket had been assembled, it was time for some “peanut butter.” This mix of epoxy blended with colloidal silica was used to fill and smooth out the rough joint between the body tubes and the seams on the fins. She was looking good now.
Rocksim gave us the center of pressure; however, we wanted to find the actual center of gravity (CG). That way we could be sure of the CP/CG relationship. The assembled A.C.M.E. was placed on the fulcrum of a sawhorse and we kept balancing the rocket until the CG was found. We were certain that nose weight would be required. Seven-and-a-half pounds of lead shot and epoxy later we were all happy.
Launch Rail Considerations
From the beginning it was our intention to use the same rail guide that Dennis had fashioned from nylon and the launch rail we had constructed for the half-scale Honest John project. But the darned crooked fins didn’t like our tower. There was no way to get the rocket onto the rail. A new tower had to be built from scratch.
That’s the beauty of a large group project. When a need arises, someone with the proper skill set steps up to meet it. In this case it was Travis Troyer. His years of custom car welding served us well.
We could use the original base and the rail. Travis and Dennis made sure the new tower design would not interfere with any of the fins. Dennis purchased the one-and-a-half inch square tubing. Travis brought a TIG welder and a large tank of Argon gas for welding. He also brought a metal chop saw, a slow-speed metal band saw, a MIG welder, a tank consisting of CO2 and Argon mixture. He brought nearly the entire shop. But more importantly, he brought everything we needed to build the new tower. We were back in business.
Ejection Charges
Ground testing of the ejection charge is always an important but worrisome step in a large-scale project. You want to be absolutely sure that when the time comes for deployment, the chutes deploy. But how much black powder will it take? The online calculators are a helpful first step. Use their estimated amount of BP for your first test. Then for your second charge, use more or less based upon your test result.
Eight grams of BP was called for by the calculator, and that is what we used. Mike Law and I set up the “test stand”—an old mattress leaning up against a well-worn picnic table. Mike put layers of sleeping bags on the ground to try to help protect the 15-pound combo nose cone/altimeter bay during our tests. I grabbed a tarp and Travis and I shoveled mulch into a wheelbarrow. We dumped the mulch about ten feet away from the “test stand.” Mike set up a lawn chair to lift the front end of the rocket up from the ground. The mulch was used as a cushion for our precious fin can. At this stage of the game we couldn’t afford any damage to it during our ejection charge tests.
It’s an awesome roar when eight grams of black powder is set off at ground level, and in fairly close proximity. It was more than adequate for the first test. In fact, it was perhaps a little too energetic. We decided another test was in order, this time using “only” six grams. It worked just fine—though the nose cone and the arming switches did sustain some minor damage that has since been repaired.
Painting Tribulations
We held an informal contest among club members to see who could come up with the best paint scheme for the A.C.M.E. Spitfire. Adults and kids alike submitted their color drawings, and a vote was held. Eight-year-old Brandon Gross created the winning design.
We were getting close now. Travis made arrangements with a friend to borrow an automotive paint bay for the day. By 8 a.m., Mike Gross and Travis had mixed the automotive primer and prepared spray guns. Not much was coming out. Crank up the compressor. Still wasn’t working too well. Another sprayer was used, but with the same sad result. After much effort, out came the brushes, and the rocket got covered with thick, bondo-smelling primer. It was an ugly mess.
For four precious hours of our limited schedule we actually watched primer dry. Talk about exciting. There were benefits though. During times like these we really get to know each other. Stories are told, and male bonding takes place.
It’s lunch time. The crew adjourns to a tavern around the corner for sandwiches and beer. Even the beer didn’t help us when it came time to sand that awful primer. When the sanding was complete, most of the primer was gone. Bare fiberglass was everywhere. Our solution was to make a quick trip to the store, buy two spray cans of automotive primer, and spray the rocket. Oh, so easy. Wish we had done this five hours ago.
We completed our final sanding. This time, the paint and the spray gun liked Travis. Strange thing though, the can of paint says “yellow” but we all think it looks gold. Maybe it gets lighter as it dries. Nope, but gold will look real nice with purple.
Mike Gross proceeded to teach us a thing or two about how to artistically mask and prepare a large rocket for painting. Eyeball, mark, tape, cut. It was great to watch a master at work, and a real learning experience. When Mike was done, Travis put his professional skills to good use again. He laid down a coat of purple for the striping, and later three of the four fins, and the nose cone got showered in black paint.
Fourteen hours later and it’s time to take all of the masking off. Wowie, zowie. We’re all as happy as clams. She looks absolutely beautiful, and well worth all of that hard work. But she’s not done yet. She needs three coats of clear to protect the finish. Mike tells us he’s really going to make the colors pop. He adds a little bit of the metallic gold paint to the clear coat. It’s amazing how that little bit of gold flecking brought each of the colors to life. Seventeen hours after we started the day, it’s time to pack her up and take her home.
Launch Day
It’s Saturday, June 2nd, and everyone from the Team-SCAM group is seemingly calm—but you know that can’t be the case. The nervous quotient is climbing rapidly. A sizable number of NSL attendees came just to see this flight, and here stands the A.C.M.E. Spitfire on display. She’s drawing lots of attention. No doubt about it. Moms and dads are posing their kids with her for those keepsake preflight photos.
Mike Law and Dennis Watkins are busy building the motor. Charlie Humphries is again bench testing the electronics and preparing the bay for launch, while Travis Troyer carefully folds and inserts the parachutes into the body and into the nose cone.
Suddenly, word is out that we may not be able to launch. What? The grass is very dry, and the Skidmark could easily cause a large ground fire. Dennis has two 55-gallon drums full of water, but would that be enough to douse a roaring grass fire? Talk about nerve-wracking.
Just in time, like the cavalry to the rescue, came the Liberty Township Volunteer Fire Department. Their crew hosed down a 50-foot circle surrounding the launch pad—just so we could launch (and they could watch) the A.C.M.E. launch.
Everything is ready now, and she’s hoisted up on anxious shoulders and carried to the launch pad. With care she’s loaded onto the rail. The excitement grows as the very heavy rail and rocket are raised into position. We’re only minutes away from launch, so it’s time for the obligatory group photos. Everyone wanted these for their personal photo albums. She looks great on the pad. We’re quite honored to have Jim Flis, designer of the original kit, on hand for our launch. He looks like a proud father with a newborn child.
Launch Day Issues
Mike Law begins the arming process, but clearly there’s a problem. The main altimeter is not arming. Retry the arming sequence. Switches off. Shunts off. Shunts on. Switches on. No joy. She’s got to be taken down.
Anxiety is escalating. Open the bay and review every connection. It didn’t take long before a broken battery clip was found. Travis got his propane-fired soldering iron, and in a few minutes the bay was closed and the optimism was climbing.
During the interim, the launch area grass dried out, so the Liberty Township crew came out and soaked the ground again. This time the SCAM crew raised the Spitfire into launch position, armed her, and got everyone back to the flight line.
Upward!
After a brief introduction, the RSO gave the 10-count, hit the button, ignition. The motor erupted into a throaty roar and sparks spewed everywhere. The A.C.M.E. rose skyward into a straight flight pattern. Shortly after motor burnout she reached apogee at 1,456 feet, arched over and spilled her chutes into the wind. As the chutes unfurled the A.C.M.E. descended to the screaming cheers of the hundreds of spectators below. Before she had even landed, a large contingent of the crew raced out into the field to retrieve her. A quick inspection showed the nose cone and altimeter bay were in perfect condition. One of the fins had popped slightly away from the body, and caused a minor ripple in the paint and the body tube. The damage was so minor, and the high from the successful mission so great, that no one seemed to care. The A.C.M.E. Spitfire had marked her place in sport rocketry history.
Kudos
It didn’t take long for the stories, photos, and videos to begin circulating on the Internet. Mike Hively said, “the crowd broke into applause throughout the flight. It was as if the space shuttle had just launched.” For Tim Hegemier, it was the first M-class Skidmark he’d ever seen. “I love that rumble I felt in my chest at lift-off.”
“Way cool flight,” said Mike Gross.
Giving his two cents worth, Charlie Humphries exclaimed “the thrill of that lift off was worth all those hours spent building and prepping her.”
SCAM Webmaster, Ed Hardy had this to say: “This was my first group project. These last six months spent working on the A.C.M.E. Spitfire has introduced me to yet another aspect of rocketry. While the awesome flight was a perfect and exciting climax to months of work, and something I will never forget, I’ll also remember the camaraderie and teamwork involved… the project was not only worth every hour and every penny spent on it, but I’m already looking forward to the future and our next project.
It didn’t take Jim Flis long to post the following words on The Rocketry Forum (rocketryforum.com): “Oh, the A.C.M.E. was un-freakin’-believable! Breathtaking doesn’t even describe it… Man!... the launch was flawless, and it was THE LAUNCH of NSL. No Question!”