Corvair Powered Zenair 601XL in The Corvair Authority Hangar
October 12, 2003
Here are the first photos of what will be our Corvair engine showcase aircraft for the 2004 season.
It is a Zenair 601XL, one of the very first of the new taildragger models. Grace and I saw it at Oshkosh this year,
and immediately found it very appealing. After speaking with the Heintz family during the week, Grace and I
decided to purchase the kit from Zenair. Arrangements were made, and Corvair builder Dave Vargesko and I drove the
2,600 mile round trip to the Mexico, Missouri, factory last month to pick up the project. Upon our arrival,
we were treated to a complete tour of the facility by Sebastien Heintz. The simplicity, common sense and
craftsmanship of their kits is also represented in their 20,000 square foot factory. A scant 55 hours later,
Dave and I were back in Daytona with the kit, which immediately captured a lot of attention at the airport.
Why We Chose The 601
Earlier in the year, we'd decided that we wanted to select a new airplane to be our primary showpiece and
flight demonstrator. The Corvair covers an enormous range of airplanes, but two factors drove our decision to
the 601. First is the time to build. Although I average 60-70 hours a week in the hangar, the vast majority of
this is tending to business and working on customers' orders. Working on our own plane, although it would benefit
the business, takes a backseat to customer orders. In the end, I have few more hours than the average guy does
for building my own airplane. Whatever airplane we chose, it had to be a very fast build airplane. Although
many people building 601s are building from plans, we chose the highest level of prefabrication we could get in
the kit because it served our need to get it flying sooner. I've found the factory work to be very clean and
Secondly, we needed a fairly roomy airplane. I'm 6 feet tall, and Grace is 5'10". Although we're not
too wide, a number of our friends and customers are bigger people. We wanted a plane in which we could comfortably
give Corvair familiarization flights. Although I like KR2s and the Sonex, the 601 is quite a bit larger,
especially in the passenger department. When we first showed the airplane at our local EAA Chapter 288 meeting,
many people mistook it at first glance for an RV-6. Our Chapter has about 25 completed RVs to its credit. Many
of these builders, upon studying the 601, were impressed with the kit. Although the airplanes serve different
purposes, it's a compliment to the 601 that some of our experienced RV builders were duly impressed with the
601 as a package.
Engine For The 601
As you can see in the photos, I've already built the Motor Mount for the airplane. Making the Motor Mount
this early in the project is made possible by the 601's excellent plans and drawings. The plans contain detailed
information on the installation of several different types of engines. Knowing the weights of these engines, it
was possible for me to mathematically calculate the correct location of the CG for the Corvair engine.
The 601 mount is the 22nd different Corvair to airframe mount I've designed in the past eight years.
It has particularly good geometry, and it is simple, light and rugged. It only weighs 5.5 pounds. Zenair's clever
design of airframe mounted nosegear means the same mount will also work on a tricycle gear XL. The firewall on
our XL actually has some of the tricycle geared bracketry in place. This is a benefit because it ensures that
tricycle gear builders will be able to follow our work on developing the 601/Corvair combination. At a later
stage, I'll remove these brackets and the plane will be a pure taildragger.
The engine in the photos has been installed on the mount to study the proposed shape of the cowling and the
installation issues. The spinner is a 13" diameter Fiberglas unit available from Van's Aircraft, the RV people.
Notice how well the front starter system blends in right behind this spinner. Although it may appear that
the aircraft has some type of prop extension, it has only my standard 3" hub. This is a good visual presentation
of my argument in favor of short extensions and large spinners vs. long extensions and small spinners.
The cylinder heads sport low profile, welded on, aluminum intake pipes. I've studied it carefully, and it should
prove to be an aesthetically pleasing, compact cowling. The generous size of the airplane's firewall and the simple
nature of the Corvair will make the completed combination clean and uncluttered.
As it sits, the engine will fit inside the stock Zenair 235 cowling with a ton of room to spare. The Corvair
is a much smaller engine than the 235, and builders who already have the 235 cowl could certainly use it.
However, it's our intention to build our cowling in a female mold. A number of my friends have exceptionally
good mold building skills, and we'll have a specific Corvair/601 cowling available if people so choose.
The first engine we will fly in the airplane is a completely stock, right out of my Conversion Manual 100hp
motor. Although I have a 3,100cc motor and my 164cid turbo motor nearly complete, I believe it is of far more
benefit to Corvair/601 builders to demonstrate how good the base motor is. This said, we're setting up the plane
from the very beginning to rapidly change out and test these other motors. People who have followed my work know
that I have done an enormous amount of flight testing of new systems for the Corvair. This airplane will have
all of the instrumentation, wiring, controls and systems in place to rapidly change from one Corvair motor to
another. This is why, as you'll see in later photos, the instrument panel has a MAP gauge which reads to 50".
As many people know, I've been working in the field of experimental aviation about 15 years. Although I
read a lot to stay up on all facets of aviation, about 95% of my hands on work is with experimental aircraft.
I have a great deal of experience with the whole spectrum of experimentals, from Pietenpols to Lancair IVPs.
While I love them all, some aircraft are best appreciated from a distance or by having your friend own one. Many of
these designs, although beautiful or great performers, take time by the calendar years and money by the cubic
yard to finish. The Zenair 601 is on the opposite end of this spectrum.
The 601, especially the newer XL model, strikes a good balance between simplicity and capability, and aesthetics
and economics. In kit form, it is among the easiest of aircraft I've seen to build. While it would obviously be
more challenging to build from plans, it would still be a very doable project, and the ability to purchase any
component from the factory makes plans building the 601 an even more viable option. There are plenty of kit airplanes
which are filled with proprietary parts that you could never hope to truly plans build. From everything I've seen,
the 601 is not like this at all.
I want to have the airplane done, flight tested, fully developed and on display at Sun 'N Fun in April 2004. We're
actually shooting to have it done way before this, and all indications say we might have it done before year's end.
I have a group of skilled friends helping me with it. This is the same team that's worked on many projects with
me over the years. The most common heard quote while we're working on the plane is, "I can't believe how simple
it is." Our friend Gus Warren, who has an extensive sheet metal background and an Oshkosh Best of Type award to
his credit, did most of the work on one wing in a few days of light labor. He pointed out that his sheet metal
background was not necessary, and in fact may have slowed him down because he spent a lot of time thinking, "This
is too simple. I must be missing something."
Above, Gus attempts to pierce his ear with the pneumatic riveter.
Stay tuned to this page. We'll update it as we make progress.