Sonex/Cleanex Corvair Combination 2008
Friends,
The Sonex is an outstanding light aircraft designed by John Monnett. It is the root aircraft in a group of designs by John Monnett that include the Waiex and Xenos.
They are available as plans and are very popular as kits. They've sold hundreds of aircraft.
The Sonex is an outstanding airframe which combines high strength, good
slow speed manners and a very high top speed capability. Its 40" wide cockpit is generous by most aircraft standards, but is snug with two full-size Americans.
The Sonex factory approves and supports only three engines for the airframe: the 2,180cc VW, and the 80 hp and 120 hp Jabbirus. The factory position firmly asserts
that for an aircraft to be a Sonex, it must have one of these three engines. We're personal friends with the Monnett family, and to respect their wishes, I carefully
refer to the combination as a Corvair powered Sonex airframe, or Cleanex, and encourage people working with the combination to adopt a different name for their aircraft.
While many aircraft designers don't care what you plan on installing for a powerplant in their design, John Monnett, along with a handful of others like
Burt Rutan, assert that you should not call your aircraft their design if it does not have an engine they approve for it. I respect the work of these men immensely,
and being careful in naming the airplane is a small concession to talented designers.
Here's a photo of Dan Weseman and his Cleanex in front of my hangar at Corvair College #8. Until his airplane was done and flying, we kept Dan's identity a mystery to
let him get the work done. At the time, a few people who saw this photo made
jokes about the "Builder Protection Program" with a nod toward John Monnett's allegededly sharp temper. In reality, Dan is friends with the Monnetts.
The first person to fly a Corvair powered Sonex airframe was Del Magsam of Wisconsin. His airframe was one of the first five hand-built prototypes that predated the
kits. It came equipped with a standard Sonex motor mount. Del is a machinist by trade, and put a lot of effort into altering the Corvair to mate it with the Sonex airframe.
He flew the combination in 2004. We saw the airplane fly at Brodhead 2004 and Del was justifiably proud of the accomplishment. We nicknamed the airplane "The Outlaw
Sonex" due to the nature of Del's engine selection.
Del had several very busy years after the completion of the plane. Although the plane was airworthy, it only logged 70 hours in its
first few years. Alterations to the engine, a mild 2,700cc Corvair, and a propeller that was below optimum for the airframe gave the airplane
acceptable performance, but it was not indicative of an advanced version of the combination's potential. This was to come next.
At the time Del was finishing his aircraft, we met a fellow Floridian named Dan Weseman. He was well into building a beautiful plans built Sonex airframe, and
strongly considering an O-200 powerplant for it. Dan made several trips to our hangar, and quickly revealed himself to be very mechanically inclined, a hotrodder of
great experience as well as a talented pilot. He had three other important things in his corner: he's got the energy of a guy in his 20s, he's positive, likable
and easy to work with by good nature, and he has a very supportive wife who encourages all his aviation endeavors. With these assets, Dan set out to build an
outstanding example of the Sonex/Corvair combination. He assembled the parts for an expense-is-no-object exercise in Corvair engine building. Dan spent a little under
$7,000, something of a record for Corvairs at the time. Dan assembled and test ran the engine at Corvair College #8.
Here is a view of the Cleanex engine at last annual. Our Gold Hub and Front Starter
system are clearly visible in the photo.
Dan's engine is a very potent 3100cc. We got him a Sensenich 54X58 prop, which turned out to be a perfect match. Dan chose to use all of our
accessories, including Prop Hub, Front Starter, Oil Pan, Alternator
Bracket, and Oil Top Cover. He chose to use all these systems because they were all flight proven on our 601. He modified one of our Nosebowls,
and worked up his own cowl and motor mount. The combination proved incredibly sucessful because Dan wisely chose a mixture of proven parts, clever craftsmanship and
practical hot rodding. Soon after it was flying, I dubbed the aircraft "The Cleanex." Once Dan showed people what the plane was capable of, it was more frequently
called "The Wicked Cleanex." You can read more of the story of the airplane at Dan's Web site, www.flycleanex.com.
Here's a view of the underside of the Cleanex's motor mount. Dan designed this mount combining the basic geometry of the Sonex airframe's landing gear attach
points and our traditional Corvair bed mount. The structure is well thought out and perfectly triangulated. Although it looks heavy, it is not. It weighs 13.8 pounds,
only four pounds heavier than the factory Jabbiru 3,300 mount. Dan's mount has flown hundreds of loops and rolls.
Many people have seen Dan and Grace flying aerobatics in The Wicked Cleanex on our Corvair Flyer #1 DVD. Continuous use of this type of
operation led Dan to independently develop his own simple, retrofitable fifth bearing setup to reduce flight loads on the Corvair's crankshaft. His Web site for
this is fly5thbearing.com. While people just getting into aviation occasionally view Dan's flying as daring, I want to emphasize that it is a smooth display of skill
and has nothing to do with daring or risk taking. I've gotten to know him pretty well, and around airplanes, Dan is pretty conservative. I would easily name him
the steadiest pilot and most meticulous maintenance guy in the land of Corvairs.
In the foreground above is Dan Weseman's Wicked Cleanex. Off his wing, Chris Smith flys the Son Of Cleanex. The photo was taken over a bend in the St. Johns River
in North Florida.
Chris Smith was building a Sonex airframe from a kit and met Dan as Dan's airplane neared completion. Chris opted to build a close copy of Dan's aircraft. Although
Chris had many years of flying experience, he had never built an aircraft before. Because of this, he wisely chose to follow Dan's proven format closely. When Chris' aircraft
was done, it earned the nickname "Son of Cleanex." It first flew at the end of 2006, and it has served Chris through many hours flying over the southeastern
United States. Chris' aircraft also has a 3,100cc engine, which was built for him by Hangar Gang member Kevin Fahy. The Son of Cleanex is currently being upgraded to
one of Dan's fifth bearing setups.
We have never gone out of our way to promote the combination of the Corvair on the Sonex airframe. I've never actively promoted something we have no firsthand
epxerience with. In the early years, we were in this position. After Del's airplane was flying, the solid but modest performance drew compliments but few converts.
Following Dan's success, a significant number of people were drawn to the combination. Dan did nothing to promote this, but the aircraft made a lot of sense to
many people who saw it. Technically, the engine, even in Dan's modified form, is above the recommended firewall forward weight limit. However, moving the battery to
the baggage compartment brings the aircraft well within its CG limits. I've personally flown in the aircraft, and it's a stunning performer. The fact that the
Corvair has excellent cooling characteristics and can be run at wide open throttle continuously at rpms even in excess of 3.600 allow the full use of the power
potential of the engine.
While we still don't go out of our way to promote the combination, we want to make it perfectly clear that people who do use it should avail themselves of our
experience and knowledge to ensure their success. Again, out of respect for John Monnett, fans of his airframe should not expect him to endorse nor provide information
about, Corvairs on his design. A recent example of a successful builder following this path and additionally choosing a different name for his aircraft is Danny
Cash, who has recently completed a 2,700cc Corvair powered airplane. The name of his airplane is "The Cashex."
In the coming months and years, there will be more examples of this combination. It takes a slightly independent character and a bit more perseverance to complete
this combination. In the land of Corvair builders, however, these two characteristics are common qualities.
Corvair Engines in the Zenair 701
Please see the applications page.
Corvair Engines in Vans Aircraft
Friends considering powerplants for RV series planes:
I have spent the past 10 years developing and flight testing Corvair engines. The overwhelming popularity of the RV aircraft and the emerging popularity of the Corvair often leads to the question: "Would a Corvair be a satisfactory powerplant in an RV?"
The plain and simple truth is NO. It has taken years of development to get the 164cid Corvair motor to economically produce 100hp with the reliability that is required from flight engines. While we now have a 120hp 190cid motor, it makes its power at an elevated rpm, 3,200rpm, and it cannot be considered a direct replacement for the O-235 in this application. The O-235 and O-290 make their power at several hundred rpm less. I believe the Corvair's thrust level to be below what would be satisfactory for the RV-9.
I have received reports of a geared, turboed Corvair installation in an RV-9, but I do not know if the aircraft has flown. The builder of the planetary gear set told me his cost was $2,500. The engine overhaul was perhaps $3,000 and the turbo system was certainly another $1,500. At this point, you've spent as much money as you would have on a mid-time 150 Lycoming.
While the Corvair has been geared and turboed to produce more power, this is done at expense which typically exceeds the cost of the equivalent Lycoming power with nowhere near the reliability Lycoming offers. Simple Corvairs have an excellent history that common sense tells you would be lost with a highly complex installation.
Only the single seat RV-3 in its most basic form would be a possible installation for a direct drive, simple Corvair.
In conclusion, the RV series of aircraft and the Corvair engine are great designs, just not for each other, with the possible exception of the RV-3. The other RVs are not designed to achieve their best performance on 164-190cid engines like the Corvair.
As a person who has done more work with the Corvair than any other living person, I suggest you consider my words carefully. Anyone who is trying to disagree doesn't have the experience I do or is trying to sell you something.
Thank you.
William