A Modern Classic
By Martin Hone, firstname.lastname@example.org
Gatton Airpark, South East Queensland, Australia
Photo by Colin Johnson
Back in 1990, when my father and I were in the process of building a J6 Karatoo, we became aware of another Jesse Anglin design, the Spacewalker II. At that time, it was being built by the Australian distributor, with both airframes currently being marketed through Serenity Aviation. A real retro machine, the Spacewalker appealed as a low 'n slow, fun aircraft, and I’ ve maintained an interest in it ever since. Little did I know that I would buy the very same kit-built project that had piqued my interest some 20 years earlier. As it transpired, relocating the kit-built airframe some 1,000 miles to Queensland from Victoria (via furniture truck) was uneventful.
And So the Head-Scratching Began
A round engine needs a round firewall, so a circular panel of stainless steel replaced the square one, and hence the entire fuselage shape was determined. From the front cockpit forward, I crafted aluminium panels with large access hatches, which have proved a blessing when it comes to any form of maintenance.
Semi circular plywood formers were affixed each side of the box-shaped steel-tube fuselage, to which four wood stringers were attached each side and hand carved to provide a rounded taper from the firewall back to the tail. The same process was used on the belly, while the upper deck is pretty much as per the plans but with the addition of a roll bar and head fairing.
The wing is made from wood and constructed in three pieces – two main outer panels and a deep center section that is permanently fixed in the fuselage. This required some thought as to how to mate the center section to the new shape, given that the plans don’t have a lot of information or advice regarding this area as it is. Laying up fiberglass over a hand-carved foam fillet, I found it was possible to fair the fuselage sides into the wing, solving the problem.
Although shown out of chronological order, creating the wing-root fairing was a simple, straightforward, and rewarding task.
Fitting the nine - cylinder, 150- horsepower Rotec radial engine proved straightforward. Simply positioned via an engine crane, where preliminary weight and balance calculations had predicted, an engine mount was duly constructed to hold it there.
Copious planning went into the design and layout of the modifications to the airframe before the engine was finally installed. Mocking the propeller in place made for a good visual cue when working out the aesthetics.
As with the access panels installed aft of the firewall, the engine mount was designed to pivot on the right- side upper and lower mounts so that the entire engine and oil tank can be swung out to gain access to the throttle body injection unit and twin ignition systems.
It entails removing three of the five mounting bolts, plus two oil tank supports, but I can do all this and have the engine swing out in about 15 minutes for any maintenance.
By any standard, the Rotec engine is a work of art, so I’ m happy to leave it out in the breeze, b ut a “ boot cowl” was constructed to cover the area immediately aft of the engine – the engine mount, fuel pumps, oil tank, etc. – with the possible benefit of smoothing the airflow between the cylinders and airframe. The engine drives through a 1.5 to 1 planetary propeller speed reduction unit and is therefore able to swing a big prop, which is great if you’ re building a World War I replica with a 90- inch- diameter propeller.
Some measuring and number crunching showed that the smallest diameter prop that I could use was 76 inches (such as you would find on a DH-82 Tiger Moth), provided the undercarriage legs were extended – nine inches longer, as it turned out. So my friend Phil worked out the appropriate increases in wall thickness and diameter in order to retain the original strength. As a bonus, the new legs give the aircraft a much more imposing stance.
Other than the custom engine installation, the rounding up of the fuselage and longer gear legs, the aircraft is pretty much as per the plans, although I did lower both seats and fabricate a swing-down instrument panel – something that had proved a great success on my RV-6.
This Time, No Pressure
Unlike the Karatoo project, where completion became an obsession, I was able to really enjoy both the building and design process with the Spacewalker. Maybe the interim period had mellowed me, but having another aircraft to fly took all the pressure off having to set deadlines for completion. I didn’t keep a record of the hours, but it was 2-½ years in the building before it took to the air during one sunny morning in July.
With the engine performing beautifully and the wings released of their surly bonds, we were airborne in less than 100 yards and climbing like a rocket. The handling surprised me as I expected the Piper Cub-like feel of the Karatoo, but Anglin has imbued the Spacewalker with control responses more akin to an RV. In other words, light and responsive – a real pleasure to fly. Anglin, like any designer, is n’ t enthusiastic about people messing with his designs, which usually take the form of using bigger and heavier engines and/or other ill-conceived modifications, so it was with much pride that after the aircraft was completed and flying, I found out that the man himself had given it his blessing.
The engine is slightly bogged down by its over pitched Australian Performance Prop s 76-inch 2-blader with 67 inches of pitch. B ut with the already short take off run and steep climb, I really don’t need the engine to turn any more than the 3,100 rpm it does now, though another couple hundred could be very interesting and still well short of the 3,600 maximum revs. It will easily cruise at 100 knots, but I find the open cockpit environment more comfortable at 90 knots where the engine is relaxed at 2,800 rpm and the fuel burn is around 4.7 U.S. gallons per hour.
Early flights were conducted without the nicely radiused boot cowl.
During a long cross-country flight in formation with friend Ray in his own beautiful Karatoo, I brought my speed back a little to keep us together, about 75 to 80 knots. His 80- hp Rotax 912 was running at around 75 percent power, the Rotec running around 50 percent power, and at each 2- to 2.5- hour leg, the big Rotec was using around half a gallon less fuel per hour of premium unleaded or avgas. If I use my regular cruise speed of 90 knots (3,000 rpm), the fuel burn averages 6 gallons per hour, depending on how much I lean the mixture on the Rotec TBI-40 throttle body injection unit.
As mentioned earlier, Serenity Aviation (www.SerenityAviation.com) has taken over the world-wide distribution rights to the Spacewalker and Karatoo designs; hopefully we might see a rekindled interest in them. There certainly has been a lot of interest in the radial-engined version, so I’ ve made available a series of notes, pictures, and drawings, including schematics for the wiring and fuel systems, which I’ ve called the RR Conversion Plans. They’ re available f rom Serenity for $85 U.S. plus postage.
Since we now reside in the sunny part of the world, we wanted a “ low ' n slow” open-cockpit aircraft, something with plenty of character and crisp handling. The Spacewalker already had the classic look, and combined with the Rotec radial, it has the sound as well. So what we’ ve ended up with is an aircraft that has beautiful flying qualities, a classic look, yet built from all- new components. With its smooth, powerful engine, and that lovely yet muted radial rumble, our Spacewalker II-RR has really proved to fit the bill nicely.
Also see the May 2010 issue of Sport Aviation for Tim Kern’s detailed report on the Rotec engine.