ElectriFly's Cosmic Wind
Speed is king with ElectriFly's new tribute to the Goodyear racing class
By Larry Kruse/photos by the author
Great Planes reached back some 65 years into aviation history for the inspiration for one of its newest offerings to the modeling public, the ElectriFly Cosmic Wind. Originally designed and built by Lockheed’s chief test pilot, the legendary Tony LeVier and a handful of Lockheed engineers, this tiny single-seat racer was aimed squarely at Goodyear Trophy Formula I racing in 1947. Driven by the competition formula and an 85 hp Continental C-85 engine, the plane never lived up to its pedigree in the races of the times, finishing third and fourth in the 1947 Goodyear Trophy Race.
AT A GLANCE
Type: R/C electric sport scale
Construction: fiberglass, balsa, ply
Wing span: 36 inches
Wing area: 254 sq. in.
Length: 32 inches
Weight: 29.5 ounces
Wing loading: 16.7 oz./sq.ft.
Motor: Rimfire .10
Battery: 1800 mAh 11.1V 25C Li-Po
Radio: 4 channel, 3 mini servos
Dist. by: Hobbico
P.O. Box 9021
Champaign, IL 61826
Three planes were built initially, a fourth later, and finally a fifth version built by amateur builders. At least one more version of the design was built in the UK and remains on the civil aircraft registry, but lacks a "Permit to Fly."
Its sleek classic lines, with a flowing fuselage shape, squared and tapered flying surfaces, and a racer’s trademark bubble canopy were captured nicely by Great Planes in this electric-powered race plane that looks fast, even at rest.
Presented as an ARF, the plane offers somewhat more than what one thinks of as the typical almost-ready-to-fly model of today. Opening the nicely packaged box revealed a plane with a very low parts count, which spoke to rapid assembly.
The larger parts were taped to both sides of a clever "floating" cardboard divider which keeps everything suspended away from the top, bottom, or sides of the box and securely safe in shipping. Removing the securing tape revealed a one-piece fiberglass fuselage with the battery hatch positioned on the bottom of the nose area, held in place with a peg at the front and two magnets at the rear. The flowing fiberglass fuselage and the compound curved hatch were perfectly rendered and painted to an exact match of the MonoKote covered flying surfaces.
My version of the plane was "Missile Red" in color, although a solid white version is also available. The flying surfaces of both versions are built-up balsa and ply structures, nicely constructed and warp-free. The other remaining parts consisted of two aluminum landing gear legs and two molded fiberglass wheel pants (also painted a matching "Missile Red"); narrow foam wheels to fit inside the pants; and a clear canopy with a matching painted edge trim. The canopy, by the way, fits perfectly over a raised canopy rim molded into the top of the fuselage.
Assembling the Cosmic Wind
After a check to see that all of the hardware listed in the manual was there, I began what was to be a very rapid assembly process, thanks to the low parts count. As a brief sidebar, I initially couldn’t find the hardware packet containing the multiple pushrods, only to discover they were taped essentially out of sight under a flap in the cardboard divider!
The plane has a very low parts count as shown in this photo (above left) of everything but the hardware laid out. Assembly moves quickly when so much is already finished. The kit has the standard Great Planes step-by-step illustrated instruction manual (above right) that illustrates the assembly steps in sequence. It also has a supplemental sheet detailing additional “clean-up” steps such as opening the wing dowel holes in the fuselage a bit to more easily accept the wing dowels, and grinding off the lip of the fuselage under the wing bolts to permit full movement of the aileron control horns.
The whole assembly process took less than five hours from the box to a model ready for flight. Stopping to take pictures at each juncture of the assembly process slowed my progress, so actual assembly time for a dedicated modeler could be substantially less than that, although allowing time for epoxy and glue to set up and cure over night is never a bad idea.
The covering required very little attention to remove what few small wrinkles were present, and I moved quickly to assembling the two wing panels. The wing is held together by a stubby, tapered hardwood joiner that also automatically sets the dihedral, and a guide pin at the trailing edge for alignment purposes.
As is the case with all assembly procedures, I always do a "dry run" to make sure everything fits together correctly before applying glue or epoxy. In this case, that proved to be fortuitous because the hole for the trailing edge guide pin had not been drilled in the right wing panel. That was quickly corrected and the wing panels were epoxied together with 30-minute epoxy and held in position with "Scotch 3M" blue painter’s tape. If you haven’t tried this tape for modeling purposes, you need to do so. It has great tack, great staying power, and yet removes easily by peeling it back. It is also available at most hardware stores.
A short, tapered, hardwood stub spar holds the wing together and sets the dihedral (above left). The stub spar required only a small bit of sanding to fit perfectly in the spar box. The rear of the wing is held in alignment with a small peg. The wheels (above right) are held on and spaced for the wheel pants with small wheel collars using tiny recessed Allen screws.
Since the ailerons are already hinged, all that was left in assembling the wing were the leading edge locating dowels and the wing bolt plate. Both of these areas do require some added attention, however, since the wing-to-fuselage mounting is crucial to flying success.
Great Planes has provided a supplemental instruction sheet that addresses how to carefully enlarge the dowel holes in the molded fuselage by manually using a drill bit to ream them out slightly. I found that this was necessary information for my plane, and that the guidelines for trimming away a portion of the wing saddle mount were also useful in order to give the aileron control horns adequate freedom of movement. Before leaving the wing, I also slightly enlarged the bolt holes in the plywood wing bolt plate to make installing the wing bolts a bit easier.
At this point, it was becoming clear that the fiberglass fuselage was a masterpiece of molding, but that the addition of the gel-coat finish and paint in the manufacturing process had made tolerances very tight. I either trimmed slightly, or opened up areas where components would be installed, including the stabilizer slot, and the pre-determined holes for the landing gear and the tail wheel bracket.
The two-piece landing gear screws to the fuselage using three screws per side. Since it is not a bolted structure, I pre-drilled pilot holes down into the molded-in anchoring plywood plate. I then tightened the screws into position, then backed them out and hardened the screw holes with drops of CyA.
One niggling little point in assembling the landing gear, wheels, and wheel pants, was having to find the very tiny loose Allen head wheel collar screws in the hardware packet and to keep from dropping them once I found them. It would have been helpful to have these tiny screws partially screwed into their wheel collars. These wheel collars space and lock the wheels into position for installing the nicely-finished fiberglass wheel pants, as one of the photos shows.
I did have to widen the wheel pant openings slightly using my Dremel tool and a flat sanding stick to accommodate the width of the wheel assembly. Also, it is important to have the inside axle head bolts at 90 degrees to the front of the landing gear legs in order for the molded mounting slot to fit over the bolt head.
Hinging the elevator and rudder, epoxying the stabilizer in place, and mounting the tail wheel assembly as indicated sequentially in the well-illustrated instruction manual, completed the airframe assembly.
The power train
The power train components were provided by Great Planes and they proved to be a perfect combination for the little plane. The ElectriFly "RimFire .10" brushless outrunner motor was the motor around which the plane was designed, so naturally it fit the laser-drilled mounting holes in the pre-installed plywood firewall.
To save the weight of a receiver battery, the ESC of choice was the ElectriFly "Silver Series" SS-35A brushless ESC which features a 5V, 2-amp BEC. That ESC was coupled with the recommended ElectriFly "Power Series" 1800 mAh 11.1V, 25C Li-Po battery. Given the static current draw of 24 amps, about a 10 minute flight envelope was anticipated before the BEC kicked in.
The propeller used for test flights was an APC 9–7.5 electric version, although the instruction manual also specifies an 8–8 prop. The supplied collet fits over the RimFire .10 shaft with no shimming necessary (top) and can be adjusted to allow the spinner to clear the nose ring. The RimFire .10 is mounted using four supplied screws and washers, which fit through the pre-drilled holes in the firewall. The ElectriFly SS 35 ESC (above) snugs up against the inside of the fuselage wall above the battery platform and is held in place with the supplied strips of hook and loop fastener.
While the plane has not been pushed to its current limitations, half-throttle flying with an occasional burst to full throttle (the plane is fast!) will get at least a 10-minute flight on a fully charged battery. Using the alternatively recommended 9–7.5 E APC prop rather than the APC 8–8 E prop gives a slight reduction in speed, but better vertical performance.
Radio installation is about as simple as it gets with just three servos and a receiver. Being a Futaba person, I was very comfortable using my Futaba 6EX FASST transmitter paired with a Futaba R617 FS receiver and three Futaba S3114 Micro High Torque servos. For those who expect to use a servo for each aileron, it just isn’t necessary for this ship. The single S3114 servo mounted in the center of the wing has plenty of torque for this airplane. The recommended ¹⁄₈ to ³⁄₁₆ inch up and down aileron movement; the ¹⁄₈ to ¹⁄₄ inch elevator movement; and the ³⁄₈ to ⁹⁄₁₆ inch right and left rudder throw do not tax these servos in any way.
The radio components chosen were three Futaba S3114 micro-servos and the Futaba R617 FS FASST receiver (above left). The ElectriFly SS35 ESC has a 5V, 2-amp BEC, which saves the weight of an additional receiver battery to power the receiver and the servos. The rudder and elevator control rods (above right) exit from their pre-installed tubes and line up perfectly with the S3114 servo arms.
Flying with the Wind
The really fun part of any building or assembly project is, of course, seeing the plane take to the air and take on a life of its own. The Cosmic Wind did not disappoint in any respect. With a projected all-up weight of between 27.5 to 29.5 ounces, the plane came in on the lighter end of the scale at 28.2 ounces, with no additional weight added to arrive at the recommended c.g. of 2¹⁄₁₆ inches in back of the LE at the fuselage/wing juncture.
I did balance it laterally as well, and found that a small stick-on weight of a little over 4 grams was needed on the underside of the right wing. If you look closely at some of the photos you can see it as a small speck, which will be embedded in the wing tip later on and covered with a piece of MonoKote.
In order to get the necessary flight shots for this article, I asked one of the better flyers in our local club, Paul Phillips, to do the honors while I manned the camera. I anticipated that a lightweight tail-dragger like the Cosmic Wind would have some problems with ground-looping on take off, particularly in our Oklahoma breeze. That was not at all the case. The little plane tracked straight down the runway with no need to keep the tail wheel pinned to the ground, and took off smoothly into a gentle, but steady climb at between half and three-quarter throttle. Once airborne, it required absolutely no trim changes whatsoever. It was delightful!
It is a small plane and is a "burner" wide open (It’s a racer, after all!), but it also slows down nicely with no tendency to drop a wing. Even though the recommended throws seem very small, they are more than adequate for loops, rolls, stall turns, and inverted flight. While initial rolls were not entirely axial, a bit of rudder programmed in will fix that.
The one anomaly that showed up from the first was in setting the plane up to land. Most small models, regardless of their power source, are not known for their glide. That is not the case with the Cosmic Wind. It is so clean and so lacking in parasitic drag that on its first landing attempt it was still sailing along merrily in ground effect as it approached the end of the runway. A second go-around started the descent much further out and resulted in a smooth two wheel landing that dropped its tail to the runway as it lost air speed. While it doesn’t land as slowly as a trainer, anyone with trainer experience will enjoy landing the Cosmic Wind.
All in all, the project was most enjoyable— from initially opening the box and discovering all of the high-quality components, to seeing the plane in flight and thinking about its racing origin as it banked around the field. One last precautionary note. This plane is not a park flyer. It needs space to fly and space to land. It is however, the kind of plane you can pull out of your car fully assembled on any day and have a great flying experience at your local field. Great Planes is to be congratulated on a job well done in adding the Cosmic Wind to its stable of great flying airplanes.
This review appeared in the April 2012 issue of Flying Models.