ZK-WBS, Bill Sargents Sonex

Why build your own aircraft???

I have been asked this many times in the past 2 years of construction, and I still can’t come up with a satisfactory answer. As far as I know there is no strain of insanity in the family, although uncle John was awfully keen on his sheep - hmmmmm.

I learnt to fly with the Mid Canterbury Aero-club in 1991, and sat on the committee etc etc, - as you do, but I wanted more. The instructor at the time was Brent Perkins and he was really keen on buying Jodel ZK-DBI but couldn’t afford it on his own so I formed a syndicate of 9 and we bought her about 7 years ago. I have enjoyed flying her - but I wanted more!

I was introduced to the AACA by arriving at the fly-in at Rangiora - you remember the one, it pissed down all weekend - but I still have the photos of Case Groots KR2 and I kept coming back to that aircraft as a possible building project….

The idea of the VW at anything above 1835cc didn’t turn me on, and a true 2 seater needs the 2180cc, so this combination dropped out of the equation.

What I wanted was a 2 seater that would trip around the country, get in and out of the usual strips the Jodel could use, have the wings in the ‘right’ place (because real pilots sit on the wing and don’t hang below it), be relatively cheap to build ( HA HA HA) and maintain. After taking the aero-club planes and the Jodel to aircraft mechanics and seeing the bills on the engines getting bigger and bigger I wasn’t too keen on going down that line. This began much investigation into the possibility of using a Subaru engine.

I have only sat in, let alone flown, four homebuilt aircraft so I didn’t have any great depth of knowledge to back up any decision on types of aircraft to build.

I was lucky enough to go flying with Rob Mackey at Dunedin in his Zenith and was very impressed. My impressions were reinforced by the comments from my son when he returned from a demo flight in ZK-ZKZ with a Subaru fitted so the Zenith 601 seemed like the logical choice. But I wanted more!!!

A little bit more speed would be nice. Enter Paddy McDonnell and his Sonex. I first saw the photos of the Sonex and thought ‘Yeah right, funny looking thing’. On closer investigation it seemed OK. The wings were in the right place, even the tail was at the back where it should be, it is metal, two place and VW or Jabiru powered.

There were none flying outside of the USA, and no homebuilt versions at all when I decided to start. I purchased the bare minimum from the factory. ie the plans US$600, and the spar-caps US$400. You could buy the flying surfaces, cowls, metal work, and fibreglass pants but I decided not to push the budget too far.

The Sonex is made of 6061 T6 aluminium and of course at that time you couldn’t buy it in NZ. I got a price from the USA and convinced 2 other would be builders to ship theirs with mine. At this time I was contacted by a fellow who offered to match my price and include release notes. Cool! I’m a starter. Eleven months passed , the other two builders dropped out and still no ali. In the end was lucky enough to get almost all I needed in 2024 T3 from an abandoned project, so at last I could start.

The 120 sheets of EXCELLENT plans had the cutting profiles in them. I started with the tail, because it was small to store. I cut the skins, and the channels were formed with the bender at the local plumbers shop. I ended up with lots of bits because when you have a sheet 12ft X 4ft on the table it is easier to cut out all the bits on that sheet.

The wings came next. They each had 12 ribs all facing the same way – even for both wings. These were shaped over wooden formers and beaten with a modified plastic bread board. No expense spared on this project…

The spars are rather massive and are the only part to use driven rivets. The rest is held together very well by about 5000 stainless pop rivets. The spars went together with the help of Dave Johnson and his rivet gun.

The skins were measured, drilled, deburred, deburred, deburred, deburred, and finally assembled. Each wing uses 3 sheets to cover the top and bottom surfaces from the spar rearwards, and a leading edge that goes from spar to spar. This piece is bent in a press built from two 12ft lengths of 12” x 2” timber and a long piece of pipe, scary but very effective.

You can never have too many clecoes. Did I mention how much I enjoyed de burring?

Ailerons and flaps came next, then onto the fuselage. This is built on the table out of 1” x 1” angle and channels, and is in 2 parts. Part one and part 2 (I hope I haven’t got too technical here). Part one is from the pilots shoulders back to the arse end and part 2 forward to the end that makes all the noise.

The turtle deck was really challenging. It was held in place using ratchet tie downs.

It would have been really interesting if they had let go!

At about this stage Paddy finished his Sonex and I was able to take a quick flight in the right seat. The canopy was a little tight and the pitch was very sensitive, but I liked it. Too late now anyway!

I purchased heaps of 4130 steel to make all the pushrods and the engine mount/ landing gear. While waiting for the ali to arrive I took a course on TIG welding.

Here is a subject where if you ask 6 experts you will get 6 different answers!

I welded the tail gear and the rudder pedals using oxy-acetylene before being able to borrow a neat little TIG welder.

All the pushrods and the engine mount I jigged and tacked – and then let John Crawford make a decent job of the final welding.

The undercarriage (tail dragger) is 1 1/8” titanium and required four ¼” holes to be drilled through it. Again many suggestions! I drilled them through the 4130 mounts in the drill press using cobalt bits and no pilot holes. Very slow RPM and plenty of pressure and cutting oil. As it turned out the 4130 was harder to drill through.


( Some of the ‘invisible’ parts that Bill made—they all disappear inside the front of the fuselage - there’s always a lot more to building a plane than meets the eye, Ed)




The engine I chose was a second hand Jabiru 2200.

This needs to have the aluminium con-rods replaced with steel ones and the 3 piece pushrods replaced with one piece models. Of course nothing of the newer generation engines fits mine so it also is going to be a bit of a challenge.

I am now at the stage of building the canopy. Too cheap to pay $1000 for one from the factory. Besides, nearly everyone I know has cracked theirs so I’m not too keen to repeat that.



My purpose built shed is just large enough to assemble the complete aircraft and this will happen soon and then painting will begin. Again another area for disagreement among many ‘experts’.

The whole exercise has gone quicker than expected, two years to date, with hopefully less than one to go.



Some observations,

1. Not being able to get the equipment and materials I need here in NZ has been very frustrating.

2. There is not as much expertise out there as I thought. Don’t get me wrong, I have been helped by some very clever people in our group and outside.

3. There has been very little interest in this project from aircraft people. I have had six other builders over the two years come in for a look, but I’ve had 2 cub packs, one entire primary school of 160 kids with teachers, one electrician and one plumber.

4. Would I have started if I knew what I know now!!!!! Yes

5. Would I do it again???? Not on your Nelly.

Bill Sargent, Sonex # 160 ZK-WBS