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The Joy of Building an Airplane from Plans

Voss Sonex

Ron Voss, EAA 153026, fly642r@comcast.net

Voss Sonex

After learning to fly in the late 1970s and attending many of the EAA Oshkosh Conventions, I found that I usually had either the time or the money to fly, but never both at the same time. Building from plans was the only way I was going to be able to own my own airplane, so in 1998, I purchased plans for a Sonex. Many of you can guess the rest of the story; I was hooked on building and have always had a project since.

After selling my first Sonex, I worked on a Wagabond project until I was sidetracked by a friend who was selling his RV-6 project. I couldn’t pass up the opportunity to build an RV so I sold the Wagabond and finished the -6. Six months later I was bit by the building bug again and I decided to build another Sonex. I really enjoyed building the Sonex from scratch, manufacturing all the parts myself instead of buying the kit, so my current project is scratch-built too.

The little Sonex flies a lot like the RV-6 except it does it slower, it takes up a little less hangar space, and is easier to maneuver unassisted in and out of the hangar. But most of all, the Sonex is much cheaper to build. I had less than $18,000 in my first Sonex and two and a half times that in the RV. Both planes work equally well for my main mission of Sunday morning fly-out breakfasts.
 
The Voss Sonex II
The main joy of building airplanes from plans, rather than from a pre-cut, pre-punched kit, is that you can easily make modifications to personalize your aircraft. After building and flying my first Sonex (built almost completely per the plans), I discovered some things that I thought I would like to do differently if I were ever to do it again. Now that I am doing it again, here is a short list of the changes I’ve incorporated into my new project, so far.

The Sonex normally utilizes stainless steel pulled or “blind” rivets for everything except the main spar. I have built my current project using as many solid rivets as possible, with flush heads being used on the exterior wherever possible. I know that this won’t increase the speed measurably, and it lengthens the build time, but I enjoy building and it does have other benefits. Aluminum rivets are lighter, less expensive, and most importantly, they look so much better. I estimate that I will save around 4 pounds and over $400 by making this modification.

The Sonex also uses Azusa cable-operated brakes, but I have opted to install hydraulic toe brakes. Tracy O’Brien makes a brake kit that fits well on the axles. The brake pedals and cylinders I installed are from Van’s Aircraft. They sell a right side brake kit which includes most everything needed.

Sonex

All I had to do was weld a few carefully located tabs onto the rudder pedals. Reservoirs that attach directly onto the master cylinders further simplified the installation. This mod increases the cost but frees up a hand when doing run ups and other ground operations.

The Sonex fresh air vents on my first plane were not very effective until I added a deflector to the outside to scoop the air in. Van’s has a nice vent kit for the rear seat of the RV-10 that I installed on my new project. It is a style that is similar to a Piper vent and I had seen a similar type on Wittman Tailwinds.

Sonex

It is a little more difficult to install on the Sonex than on the RV-10 because the RV fuselage skin is precut to fit the vent. Anyone building from a Sonex kit with the NACA opening already cut out might consider the vent kit for the other RV series.

Sonex

In an effort to limit the fiberglass on this project, since I really dislike filling and sanding, I have also replaced the fiberglass tail tips with metal. Building from plans allowed me to lengthen the stabilizer spars and skins so it will not look like an add on. This mod added virtually no cost, but saved the cost of buying and painting the fiberglass tips.
 
Engine
My original plan for an engine this time was a VW with a belt reduction drive and a longer prop, for the increase in takeoff and climb performance. After looking closely at the drive and how it mounts to the engine, I was less impressed and decided to go back to the AeroVee direct drive VW. I may consider a swap in the future, and it would not require many modifications other than a new cowling and prop.
 
Caveat
I must caution against making structural modifications, or any changes that could adversely effect safety, but keep your eyes open at AirVenture and other fly-ins to scout out better ways to build.

Sonex

 
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