What’s a Rocket?
Unless you’re a close follower of John Harmon and Mark Frederick, you probably are a little hazy on the whole Rocket thing. All in all, it’s pretty easy. The first Rockets were developed by John Harmon from portions of Van’s RV-4 kits. The primary difference is the presence of a six-cylinder Lycoming powerplant in the nose of a plane designed with a four-banger in mind.
Why do this? Well, if you have to ask… (Hint: It’s about pure, unadulterated performance – higher speeds, nosebleed climb rates, and energetic aerobatics).
Before we get too far ahead of ourselves, let us go back and have a look at the history and design philosophy behind the Vans RV series of aircraft, as this will help you to understand better why the RV-4 kit is the initial Rocket platform.
A Brief History of Van’s Aircraft
Back in the 1950’s, Ray Stits (of Polyfiber fame) built a small homebuilt known as a Playboy. The Playboy would eventually become one of the most influential aircraft during the post-war boom in aircraft homebuilding.
Richard (Van) VanGrunsven, of Van’s Aircraft, (“RV” of course, stands for Richard VanGrunsven…) built a Stits Playboy and then improved it.
In the late 1960’s, with his experience flying the Playboy, he began to design the RV-3 as a clean sheet attempt to maintain the Playboy’s configuration and layout concept but to improve it in all aspects. The RV-3 design philosophy was to incorporate light handling, aerobatic capabilities, and fast cruise speeds.
Van’s Aircraft company was founded in 1972 and began by selling RV-3 plans and various parts. Since then over 8000 Van’s aircraft have been completed and flown.
Design Philosophy – Total Performance
The goal behind the design of Van’s RV series of aircraft was to achieve the maximum overall performance, flying enjoyment, ease of construction, building and flying economy, ease of maintenance and pleasing appearance possible for a two-place airplane.
The “traditional” configuration of the RV aircraft; tractor engine, monoplane, stabilizer in rear, is a valid exercise, not merely a concession to convention. This formula for aircraft design has been successfully used for decades, and the bottom line is that this configuration is proven to offer the best compromise resulting in the best all around airplane.
The constant chord wing planform provided easy construction, stability and lifting ability. The possible drag and aesthetic penalties of the rectangular wing are negligible in light of the advantages. The airfoil is a modified NACA 23013.5 which is a mature airfoil often critically discussed in “airfoil selection” articles and texts. However, this basic airfoil has been used on some of the world’s most successful aircraft including the Taylorcraft, Turbo Commander, and even the Cessna Citation. Others using it include the DC-3, all tapered wing Beechcraft and many of the Cessna twins.
In addition to the stable wing platform, the RV aircraft are also designed to incorporate a relatively long fuselage with large tail surfaces which provide plenty of control authority.
Seating arrangements vary among the RV aircraft, depending on the primary mission design. Side-by-side seating was chosen for the RV-7/-9 because these aircraft were designed primarily for cross-country flying. Particular advantages of the side-by-side configuration include equal visibility for both occupants, dual control capabilities are more easily achieved, increased instrument panel space, minimized Center of Gravity travel for various loading configurations, and a full cowling with room for engine accessories and plumbing.
The RV-4 was designed with tandem seating because this arrangement provided lower drag, better pilot visibility, and aesthetics that have more appeal to the “sport” pilot. The increased visibility allows the aircraft is flown solo from the front seat. Handling and Center of Gravity characteristics would be better had the solo-pilot position been the rear seat, but visibility is of sufficient importance to override these considerations. An additional benefit of the front seat location of the pilot is the ease of landing.
The Vans RV series of aircraft are designed with a rather broad “Mission Profile.” These aircraft were intended to fill nearly all sport flying needs: Speed, STOL, limited sport aerobatic. To meet all these requirements, the designer must delicately balance all aspects of the aircraft. Favoring one criterion over another often adversely affects the others. This rational isn’t a “maybe” it is a certainty. For instance, maximizing cruise performance by installing a full suite of avionics, instruments and upholstery. Being a kit aircraft, the designer left these considerations up to the individual builders to assess whether the trade-offs are worthwhile. Additionally, the cruise speed of the RV aircraft can be improved by reducing drag through attention to finish and fitting details.
It should be obvious now that the Vans RV aircraft have met their design philosophy and achieved overall performance, flying enjoyment, ease of construction, building and flying economy, ease of maintenance and pleasing appearance.
Beyond Total Performance – The Harmon Rocket
For decades, people have modified motorcycles, cars, boats and many other things seeking to make a vehicle meet their needs and desires. Naturally, this applies to airplanes too, and the Harmon Rocket is no different.
Somewhere back around 1988, John Harmon created the Harmon Rocket I which was a modified single place Van’s RV-3 sports plane that had fantastic performance. Advance a few years to 1991 when the RV-4 kits came out, and John began calculating how to hang a 250 h.p. Lycoming IO-540 engine on it with an 82-inch diameter constant-speed prop from a Cessna 180 so that he could get every pound of thrust available.
Eight months later in October 1991 the Harmon Rocket II was released.
The Harmon Rocket II is a modified Van’s two place RV-4. When you purchase a modification kit to build a Rocket from John Harmon, the kit is an extension of the RV-4 kit which is purchased from Van’s.
Harmon Rocket II is beyond total performance and today John Harmon provides a conversion kit for the RV-4. Be warned, the HRII is not a quick build kit. This aircraft is better suited to builders prefer to be more involved in the aircraft building process and express a preference of some minor fitting and trimming. Harmon Rockets were made up of portions of Van’s kits and portions of Harmon’s own design and manufacture. These build projects are complex and usually not taken on by first time builders; the construction of the HRII closely resemble that of the first Van’s RV kits before the kits were CNC machined with matched-holes and jig less construction.
The HRII resulted in a beefed-up airframe ready for the big six-cylinder engine that includes the following modifications:
The firewall is the full width of the fuselage. The instrument panel is set 3 1/2 inches further forward than the typical RV-4, providing more room between the pilot and instrument panel. The fuselage has a 4-inch stretch between the rear spar carry through and the rear seat. The main spar box is 4-inches wider than the RV-4. The additional width added by the full-width firewall and the main spar box is where the roominess starts to become apparent. The entire tail cone is positioned 4 inches further back to bring the airplane into CG with the IO-540 engine up front. The canopy of the HRII is a tip-over design.
The parts from the RV-4 used on the HRII include the wing, tail, and fuselage. From the rear seat to the tail cone, the rear fuselage bulkheads are all RV-4, including skins for the sides, bottom and tail cone. The top deck, aft of the rear seat bulkhead, is a new piece along with the upper bulkheads of the aft fuselage. The rear seat ribs are changed to be 4-inches longer. The front ribs are RV-4, which keeps the spar spacing between the main spar and rear spar to fit the wing.
The wing is the RV-4 wing. All rib locations changed, and the wing length is reduced by 7-inches at the outboard end. Overall, the HRII has a 14-inch shorter wings span. The fuel tanks are extended to increase the fuel capacity up from 32 to 42 gal. (55 gallons optional). The flaps and ailerons are shortened to accommodate the shorter wing.
The tail is a stock RV-4 empennage with 0.020 skins on the elevators and rudder.
Engine / Propeller
The recommended engine is the Lycoming IO-540-C4B5 or -D4B5 250/260 h.p. The recommended propeller is a Hartzell compact HCM2YR used on the Beech Sierra and Beechcraft Duchess. The propeller blades are 8468/8477 between 80 and 84 inches in diameter. The spinner is off a Rockwell 114.
Engine Mount / Landing Gear
The HRII engine mount and landing gear combination are designed similar to the RV-4. The landing gear is all titanium. The top side is machined similar to the RV-4, and the bottom side is machined for a bolt-on axle using a Cessna type axle with 500 x 5 wheels.
TeamRocket and the F1
Moving our timeline ahead, along comes Mark Frederick, who saw the benefit of bringing the Rocket concept into the quickbuild world and began producing whole kits in the 1990’s.
Using knowledge and experience gained in the building of at least 8 HRII kits. Mark was also involved and working closely with Bruce Bohannon’s Exxon Flyin’ Tiger. The F1 quickbuild kits were developed to satisfy customer demands.
The F1 kits are stand-alone, meaning that the builder was not required to purchase anything from Van’s Aircraft. The Team Rocket F1 Rocket eventually was joined by a new project featuring tapered wings, called the F1 Rocket EVO.
Sure the F1 looks like the Harmon Rocket II, but these two aircraft are all individual. The F1 includes a sliding canopy, titanium gear legs, larger brakes, and several beefier areas. The F1 changes also include a widened firewall and larger tail surfaces.
TeamRocket and the F1 kits were ongoing overseas until foreign suppliers of the quickbuild kits broke ranks. Mark has continued to forge forward gone on to stuff a Continental IO-550 into the nose of the EVO testbed he owns. Today the F-1 Rocket kits are no longer in production; however Harmon Rocket parts are still available to modify Van’s RV kits.
Update Late 2017: Flyboy Accessories and TeamRocket/F1 Aircraft are starting production of F1 Rocket and F4 Raider parts!!
My Damnlottafun F-1 Rocket
With demand for the F1 Rocket still running high, there is an option for those of us who still want an F1 to be able to have one. Due to F1 parts availability when I began construction, this F1 Rocket will have a modified or “Rocketized” RV-8 tail, Sport Wings that begin with an RV-4 wing kit, then modified into the Sport Wings as per the Harmon Rocket II plans. The fuselage will be constructed from a mix of F1 Aircraft parts and a few RV-4 odds and ends.
Follow my journey building the Damnlottafun F-1 Rocket on my build log here.