Savoring a New Design
The show stopper for this year’s COPPERSTATE was undisputedly Chris Christiansen’s one-off Savor. With its very short-span cantilevered high wing, extra-wide cabin with leather tandem seating, welded 4130 steel tube fuselage inside a fiberglass fairing with an all-metal wing and empennage filled as smooth as any composite wing - Savor appearing vaguely similar to so many tricycle-geared European S-LSA entrants, until you look in the cooling inlets and see an 0-320. It was quite the enigma to the many attendees who stopped by to take a closer look.
The name inscribed on the vertical stab reads “Savor the Experience,” and the “Experimental” decal displayed in 2-inch high letters on the door still didn’t help solve the puzzle posed on the showplane ramp at COPPERSTATE this past October. Only when owner/designer/builder, 29-year-old Chris Christiansen appeared and answered questions did it all come together - the one-of-a-kind Savor.
“I began with the idea of what I wanted and what I enjoyed flying and also what I thought other people might enjoy and appreciate in a clean-sheet design,” he said. “I love flying high-wing aircraft as they tend to be more stable and since this aircraft’s purpose was to be a comfortable, quick-trip jumper of about 300-400 miles, I didn’t want to have to be on the stick the whole time.” From beginning to end, including design time (by hand, no computer aided design), it took Chris 15 months to arrive at COPPERSTATE 2009.
It’s been long thought that high-wings tend to be slower than mid- or low-wing aircraft of the same basic specifications, but the BD-4 and Wittman Tailwind seem to defy that line of thought. Chris thought that if he adapted newer composite methods of construction to allow a sleeker shape and refined lines, he could improve upon the success of those earlier, successful designs. His plan was to prove that a high-wing doesn’t have to be an ugly, slow aircraft.
No newcomer to design/build, Chris’s first project was displayed at COPPERSTATE 2003.
Chris is no stranger to aircraft design and construction, and no stranger to COPPERSTATE, either. As an exhibitor in 2003, he displayed his Peregrine XS-302, a one-off, single-seat, all-composite, Rotax-powered time-to-climb aircraft. Although completed and flown, Chris hasn’t attempted a record flight yet. He instead built his second aircraft, the Saker, before designing the Savor, an “ultimate” short cross-country machine, his third design, and certainly not his last. Read more about the Peregrine in the accompanying article.
Features and Specs
Although nothing about this new plane could be described as conventional, every unique feature is symbiotically and elegantly knitted together and is comprised of all of Chris’s favorites. From the unobstructed view of the ground due to the cantilevered high wing, to the ability to bring a friend along, the Savor fits Chris’s needs like a glove. Conventional gear is something Chris never enjoyed, so tri-gear is his choice. And who doesn’t love a great power-to-weight ratio, which he gets from the 160 ponies on tap from the freshly overhauled (by him) O-320? With a gross weight of just under 1,600 pounds, the Savor’s power-to-weight ratio is better than a stock Lancair 235 or 320, and much like that of a Van’s RV-4. Although Chris is very slight in stature, he’s smart enough to know that a good designer should not design a plane around his own physical size; he was interested in having ample room in the cockpit, which he accomplished by way of hip and shoulder dimensions of almost 36 inches wide - the width of the engine. Headroom is most accommodating in its current configuration, too, but a 6-inch increase is planned.
Solo flight is conducted from the front seat which is situated right on the center of gravity, so the pilot can weigh just about anything, potentially as heavy as 350 pounds with full fuel.
The Lycoming O-320 is expertly installed. Any A&P would be envious of the workmanship and attention to detail that went into everything under the cowl, from the Dynafocal engine mount to the 4-inch propeller extension.
The engine is your basic Lycoming O-320 with compression boosted to net a full 160 horsepower. A used core was completely overhauled by Chris; new cylinders, new cam and lifters, rebuilt mags, just about everything that was available new was installed. The crank and case were overhauled and brought to new spec. The prop is attached via a 4-inch extension, and the exhaust is carried away from the combustion chambers with “very long,” as Chris put it, straight pipes - no muffler.
Chris designed the intake plenum to use an automotive-style K&N air filter with an otherwise stock carb heat system. The top of the engine is enclosed with a custom-fitted aluminum and fiberglass cooling plenum fed by two annular intake openings with an airfoil cross section, feeding a pair of precision-formed diffusers.
The propeller was built by Gary Hertzler, Hertzler Propeller, Inc. firstname.lastname@example.org. Gary started the business in 2000 following retirement from Honeywell Trubine Engines. Since then, he’s designed and manufactured over 250 propellers, primarily for the canard community, although he has made some for RV and Glassair products. The prop on Chris's plane was originally designed for the Glasstar but after cleanup (spinner and pants at a minimum) Gary feels that Chris will need one closer to what a O-320 RV4 would use. Gary was also Chris’s tech counselor and had built props for his other planes, so with this plane Chris was quite insistent that it have a Hertzler prop, too. At present the prop is a bit underpitched and acts as a climb prop, giving full RPM at any angle of climb. Once leveled off, power needs to be reduced to keep the RPMs under redline - 175 mph sees 2,950 on the tach.
The short, clean, all-metal wing is built similar to a BD-4, with tubular spars and an exceedingly long center section for increased G loading, “…not aerobatic but lively,” as Chris put it, although he also admits that it’s designed for 6 G’s. The pilot’s operating handbook clearly states no aerobatics, and Chris noted that the oil system and carburetor can’t handle any negative G’s.
The wingspan and the airfoil are built for speed and all the flush rivets are filled - the tail surfaces are of the same construction. The ailerons and electric flaps are constructed from bonded PVC (polyvinyl chloride) ribs and riveted spars wrapped in an aluminum skin. All but two of the control rods ride inside a bearing or bushing of some sort for ultimate smoothness in the control system. The wings are detachable and the ailerons have a 2:1 differential ratio to help diminish the effects of adverse yaw. The flaps can be set to any angle using the “momentarily on” switch.
The laminar flow NACA 64-415 airfoil Chris selected appears nearly symmetrical. This is the same airfoil that’s used by the Sonex Waiex and Xenos; Bede BD-1, BD-4, and BD-6; Grumman Cheetah and Tiger; and American Aviation Yankee, just to name a few. See David Lednicer’s “The Incomplete Guide to Airfoil Usage.”
Appearing as being fully composite, the rudder, horizontal stabilizer, and the elevator are in fact metal. The rudder is an extension of the tube frame, covered by the fuselage fairing.
The 4130 steel tube fuselage was completely MIG welded (metal inert gas, aka wire-feed) and fully painted by Chris. The construction is similar to a Glastar except that the “cage” extends all the way to the tail and includes the vertical stabilizer, whereas the rudder, elevator, and horizontal stabilizer are all made from aluminum. The shell halves are not structural; they are simply a light-weight fairing (made from a permanent mold) and can be removed for maintenance, repair, or retrofitting. The true reason for this design feature is perhaps frivolous at best. Chris thought this construction method would be “cool” to accomplish, and now that it’s done, he’s not sure that there is any real need for it or benefit to being able to remove the fairing. Future versions may call for bonding the fairing.
Admittedly it’s overbuilt for testing purposes, but future plans are to remove some of the current structural members (steel tubing) inside the cockpit to allow for lowering the pilot’s seat for taller persons and for comfortably locating the rudder pedals for the rear occupant, which weren’t installed at the time of the show.
Along with the visibility theme, Chris made his doors nearly 100 percent acrylic. With the exception of the necessary structural frame, once seated, it’s as if there are no doors on the plane. For some reason Chris doesn’t like planes to have doors that open like car doors, so he made his hinge up from the top being supported by a pair of gas-filled struts The only drawback to this is the depletion of headroom when entering and exiting, otherwise the overhead hinge mechanism is simpler to build than just about any other. Although it looks like it has doors on both sides of the fuselage, only the port side is operable. The view out either of them is the same, however.
The canopy appears to have compound curves, but it’s actually made of one single sheet of flat Lexan (polycarbonate). The cutouts at the leading edge of each wing allow for a second bend perpendicular to the main bend, allowing for somewhat of a skylight right up to the spar location. The leading edge of the canopy actually extends forward of the firewall, giving it a very streamlined profile.
The interior of the plane is very professional looking, all the way down to the plastic trim and headliner. In this case, Chris carved the interior (in place) from foam, laid fiberglass over the foam, and once cured and removed from the cockpit, scraped all the foam off the back side. With a little spray texture, paint, and exposed screws, it looks like it came off an assembly line in Wichita, Kansas.
Chris designed and built the tricycle landing gear. Of particular note is the solid round section of 7068 aluminum that makes up the main gear legs. This alloy is touted by many as being “the strongest aluminum commercially produced.” The design was proven on Chris’s “interim” plane (his Saker) and it worked well. The taper machined into the metal is there to control the spring rate and was cut by Chris on a 10-inch table saw with a carbide wood-cutting blade - one blade per cut.
He also designed and manufactured the weldments at each end of the aluminum legs and the steel nose strut - the front wheel being full-castering. Where the aluminum main gear plugs into the fuselage is reminiscent to that of a conventional gear RV, where the mains plug into the engine mount. Of course wheel pants (and a spinner!) will be installed after phase-one flight testing is completed.
Sunburned, tired, and dirty (actually the t-shirt was made to look dirty), Chris had a very long day showing his plane. The reward of course came later that evening at the award ceremony.
An Award-Wining Design
The COPPEERSTATE aircraft judges were duly impressed with the Savor - enough so to award Chris the “Best Plans Built Award.”
Chris is refining the construction techniques to potentially reduce the labor and the parts-count to build and to hopefully reduce the cost to complete the aircraft, in anticipation of possibly kitting the aircraft if the design proves itself to be marketable. Depending on the price, my guess is that Chris has hit a home run.
With only four hours logged for phase one (at the time of the show), Chris doesn’t have all the numbers together yet, but cruise speeds in the 150 mph range with a 7-gallon-per-hour fuel burn are anticipated. And as with any prototype in the initial test phase, the numbers aren’t final. Chris reserves the right to keep some info confidential, but the following numbers are current at this writing yet still preliminary.
Wingspan – 23.5 feet
Length – 23 feet
Empty weight – 1,097 pounds (overbuilt)
Gross weight – 1,550 pounds
Airfoil – NACA 64-415a
Engine – Lycoming 0-320, 160 horsepower
Propeller – Hertzler Silver Bullet
Landing gear - Tricycle 5 x 5.0 wheels
Seating – Tandem
Fuel – 16 gallons (header tank),
14 gallons (future wing tanks)
Cruise speed – 150 mph @ 2,400 rpm
Top speed – 170 mph (so far)
Stall speed – Not yet demonstrated, but 55 mph with full flaps is anticipated.
The morning after. Courtesy of Chris Christiansen.