Building the Sonex

Availability

In line with a grass roots philosophy, and in order to keep costs to a minimum, the Sonex can be built in several ways.

At the basic level, the computer drawn plans are first rate and the entire machine can be scratch built if the builder so decides.

At the next level, the builder can purchase various component kits such as all welded parts, spar caps, fibreglass parts (cowling etc), fuel tank, canopy and a formed kit which contains pre-bent material from which the final components are made. The builder remains responsible for obtaining the 6061-T6 aluminium, hardware, instruments, wheels and brakes, upholstery, propeller, and engine.

Finally, for quick build time, Sonex have produced a more complete kit containing laser cut and pre-drilled components which saves many hours of layout and sheet metal work.

I decided upon purchase of pre-formed material and component kits from Sonex and local sources for sheet and angle material. This avoids the need for special tools and skills for bending, welding and fibreglass fabrication. I bought all the hardware, nuts and bolts etc. from a U.S. supply company but these are available locally if you want to compile your own list and source what you need. With this way of doing things, the project still remains very much plans-built. I have estimated builder percentage to be around 85%.

The all-up cost of the component kits and materials including all instruments and new Jabiru 2200 engine has been approximately A$29 000. There will inevitably be more to spend before I am finished but I do not expect any further major expense apart from fitting of the engine and fuel system, finish and cockpit fit-out. Although I purchased all I needed at once, there is no need to do this. The advantage of the Sonex over a complete kit is that you don’t have to buy it all at once. You can start with the plans and a single sheet of 6061 material if that is the extent of your budget.

Construction

I received my plans in May 1999 and the component kits in November. I started by fitting out a workshop and making the work benches. I began construction in December 1999 and I am building as work and time permits. So far I have spent about 1270 hours total building time.

Construction has been straightforward with fabrication from locally sourced 6061-T6 sheet and angle material as well as the pre-bent material. Most riveting is with 1/8″ stainless steel pop-rivets except for the main spars.

No jigs are required to build the Sonex. The entire aircraft is constructed on a flat 12 ft x 4 ft workbench. Tools can be basic such as typical electric drills, hand shears, saws, files and a hand pop riveter. But I have fitted out the workshop with band saw, drill press and a compressor with air drill, riveter, and sheet nibbling tool to make life easier. I would suggest the same to anyone who is serious about undertaking a metal construction project.

Skills

If you can use my own case as a yardstick, you need no previous metal working experience. I suppose I benefit from a head start, having having been around flying generally for most of my life. I am familiar with aircraft construction in general, particularly wood. My father has been involved with home building for more than 50 years and has built 12 aircraft of one sort or another. I have undertaken a complete restoration of a wooden glider and the installation of a rebuilt engine in my present Cygnet aircraft.

But metal construction is completely new to me and I have had to learn all the skills required. I started by reading up on metal working techniques. The Jeppesen book on basic sheet metal work has been a good reference. But I have had more value from a very skilled and helpful RV builder for practical advice and hints and tips. I set about teaching myself the basics of measurement, layout, cutting and finishing sheet and angle material, drilling, deburring and riveting. For every new technique, I practiced on bits of scrap until I was confident, then launched into it. I started on the easy parts and worked my way up to the spars. I am now happy that if I can do that, I can do the rest.

So my opinion is that if you have the ability to build a model aircraft or even a good planter box you can build the Sonex. But to do a good job you will need a willingness to learn, be prepared to make mistakes and aim for a high standard of workmanship. As the Sonex building manual says — treat every part as a piece of jewellery and you will be OK.

Problem solving

When you get down to the nuts and bolts of construction there are a whole variety of small problems you have to solve. Most of these involve reading the plans properly and this alone takes a bit of time to get used to. The plans are highly detailed. Most everything is there, you just have to study them.

As a comprehensive resource in problem solving there is the ever expanding Sonex builders group available on the internet. The builders are keen, talkative and approachable. You can get an answer to any problem you may have by searching the archive or asking a question directly to the group. If you are in doubt about anything at all, there is help at hand. Many builders keep highly detailed web pages which are a priceless source of information.

Hours

I have kept a detailed log of time and can break it down so far (1st October 2002) as follows :

Vertical stabilizer — 75 hr
Rudder — 24 hr
Horizontal stabilizer — 102 hr
Elevator — 52 hr
Flaps — 34 hr
Ailerons — 72 hr
Wing ribs (forward & aft) — 100 hr
Main wing spars — 245 hr
Rear wing spars — 31 hr
Wing assembly — 350 hr
Aft fuselage — 133 hr
Turtledeck — 60 hr
Total — 1278 hours

For total build time, an estimate I have seen is 1200 hours over 2 years to complete the airframe. This obviously depends on how fast you work, how particular you are with detail and finish and how much time you can spend on it. My rate of progress seems to about 3 times slower than that shown for other builders. But then I have included all time such as sweeping the floor, studying the plans, drinking coffee, scratching my head etc. I am taking less time as I go along so I would estimate that a total of 3000 hours would not be an unreasonable estimate in my case and I would expect it to take about 4—5 years. I will only really know when I have finished.

Is it worth it?

Well I haven’t finished yet so I can’t tell you for sure. I can say that I am certainly wiser for the amount of work involved but my initial enthusiasm remains undiluted. It will be a grand day when this little plane takes to the air and I am determined to make it happen.

. . . . . Lynn Jarvis

The next page in Lynn Jarvis’s Sonex project features the construction of the tail and spar.

Lynn Jarvis’s Sonex project

| 1. Introduction | 2. Sonex specifications | 3. Building the Sonex |