It would be hard to imagine two more unlikely coconspirators in the plot to persuade me to construct a homebuilt aircraft. On the one hand my long suffering wife of forty years, Barbara, and Paul Hanson, Director of Curmudgeonly Studies, at Brown U, on the other. L.S.W.O.F.Y....”You have looked long enough...if you don't build something soon you will be too old. Failing that, get rid of twenty years of accumulated Sport Aviation magazines.”
P.H.D.O.C.S....”I've just read about the perfect plane for you to build...it's called a Sonex.”
My initial search for “Sonex” on the Web came up with nothing more exciting than a brand of drywall, but perseverance finally yielded a homebuilt design by an ex-Skunk Works engineer named Pete Buck. Incidentally the design bears a striking resemblance to an aircraft called the Kittiwake designed and built back in 1967!
Over the years I had formed in my mind the design that I felt would meet my needs. Low wing monoplane, two place side by side, economical engine, good plans with some parts, reasonable cost and metal construction. Removable wings would be nice too, since being cheap, I did not want to pay for hanger space. The design as advertised seemed to meet all these criteria so there were no more excuses left and I decided to bite the bullet.
My advertisement in the Chapter 14 newsletter found three other equally naïve people willing to share resources and build the same design. Though all the drawings had not yet been completed we ordered a set anyway. A local metal supply house sold us enough sheet stock to make an unspecified number of three wheeled off-road vehicles, (selling metal for aircraft was too much of a liability) and Aircraft Spruce doubled their profits for that week with our purchase of the required hardware.
My first part rolled off the production line at 5:30 pm on January 24, 1999 followed by countless others made and sometimes remade over the next six years until after 3181 hours I thought the construction was over. Dreamer!
During the ensuing years I made over forty significant design changes, some of which actually improved performance and handling and others which can only be justified under the heading...“There is no such thing as a failed experiment.” Some might say that it is not very smart to change an original design but all the modifications were made for reasons of performance or comfort and all paid due respect to structural integrity.
At this point I hope it would not be too presumptuous of me to make a few personal observations based on the ninety or so hours of flying I have experienced in 535CB. Basically the aircraft is sound and strong but a potential builder should consider whether the inherent “Neutral stability” of the design would fit his flying needs. Choosing the heavier six cylinder Jabiru engine is definitely a plus in helping to mitigate this unfortunate characteristic. The other point worth making is that I would not want to remove the wings more than twice a year and then only with a crew of helpers. This is not an aircraft to be trailered.
On a more positive note...this is a nice performing craft with a fuel burn around 3.5 gph, a very docile stall and really ground handling even with non differential braking. Landing characteristics are probably good though I have yet to prove them! And yes, it does qualify for Light Sport with the smaller engine.
I have often thought that if I ever submitted 535CB for inclusion in Sport Aviation I would have to caption it... “The plane that THEY built”. THEY would be the numerous chapter members who helped me with problems big and small, technical and elementary, and without whom I would probably still be struggling. I think of people like Dennis Cullum who designed the many little circuits that lurk under the instrument panel. People like Terry Peterson whose knowledge of motor sports was invaluable in making some of the decisions firewall forward. Chuck Howard who conceived some of the tooling aids and made many machined parts for me comes to mind and there were many others.
Lastly but not least is the man that risked his neck many times with and without me in the left seat, Pete Grootendorst. This is the hero that did the maiden flight and suffered the early hiccups in engine performance. Never once did he balk at doing the test flights while I attempted to solve the fuel problems and he stuck with it while they were eliminated. Thanks Pete.
Well, 535CB has come a long way and its taken more hours than I expected but I would not have missed it for anything. Now if only I could find a way not to polish the “beast” so often I would be truly happy.
Thinking of building? Make a start. Failing that, get rid of all those old Sport Aviation magazines!