Why did I build a Sonex? When did the idea start?
I suppose I could go back to when I was a little kid stretching
to hold up my Dad's glider wing and with small legs running
as fast as they could to keep it level on the cable launch
take-off.
Or maybe it was much later when I took up hang gliding
and was soon running a flying school and taking part in
the fledgling organisations that held things together.
Or was it when I bought a wrecked glider, restored it
and, on one strong thermally day, flew it as high as I
ever have been, to 15,000 ft. The whole gulf was set out
like a map below, the canopy fogging slightly with the
cold and wingtips brushing the tops of the high cumulus.
Or perhaps it was when I started my PPL in an old beat
up C150. Or maybe it was when I gained an ultralight certificate
while I was waiting.
Or, what about when I built a hangar and had nothing
to put in it. Or when I bought a Skyfox that was for sale
in the hangar next door. Or when the newly built, super
balanced 2100 VW in the Cygnet roared to life for the
first time.
It wasn't a quick process and it sort of grew with me
over time. I do remember the armchair discussions and
hangar talk of the cost of this and what you got with
that and Joe Bloggs down the road was building this one
and an awesome guy had built an RV in 6 months. But hey,
I had made my decision some time back of the sort of aircraft
that I was interested in building and I hadn't found it
yet.
Then along came the Sonex. It was just a picture in
a magazine, a prototype, not even available as plans,
but they promised them soon. I was hooked. So I waited.
Finally the Sonex plans became available. Mind you, they
were only half finished and I had to source all my own
material and arrange my own import of the expensive bits
- spar caps, canopy etc. But I had made a start
The actual decision was made a long time back and the
Sonex remained my ideal. Imagine it - plenty of room for
two, 110 kt cruise, light and small, stalling speed and
weights well within the ultralight category specifications,
an Aussie Jabiru power plant, an all metal shiny machine.
This was in 1998 so cast your mind back.
Now this didn't happen without some discussion with
my wife and her support for such a big undertaking, as
well as some careful budgeting. We had to find money for
materials and the all-important engine. But there wasn't
much more needed for the basic aircraft. So the big orders
went off.
Some months later, quite a few large boxes and long
tubes arrived on the doorstep. After that, a very heavy
pallet of sheet metal and bundles of angle material turned
up, as well as an engine in a box. I found it hard to
imagine that all this would end up as an aircraft.
A room in our office building became the workshop and
later on, two rooms were consumed after a wall was knocked
out. I eventually rigged the entire airframe inside. The
workshop became home for quite a few years. There was
a sort of routine to it. I would open the door and knew
exactly what I wanted to achieve that day, so the building
process was fairly continuous. That is until I had so
much else to do, I had to shelve it for a year. But soon
I started again and continued at an increasing pace.
The learning curve is steep. Suddenly I was faced with
endless small problems like how many teeth per inch should
I use in my bandsaw. Should I get more of those 3/32 clecos?
When you buy anything don't mention the word "aircraft".
How do I know a bend is good? What radius, set back and
how? Any Sonex builder will tell you that T106-03 is difficult.
Maybe some crack testing is. How on earth do I drill that
titanium? Search for answers and find them on the Sonex
email discussion group.
Why doesn't that fit? Measurements wrong - didn't triple
check. Get it square or the holes won't line up. A dull
drill bit will consume more time deburring than the saving
is worth. What is this acrylic canopy stuff? Treat it
like soft glass. The tank plumbing calls for NPT fittings
but local supply is BSF. Watch it - they look the same
but don't match. That AN3-6A bolt called for is a bit
short. A 7A with a washer seems better, only got a 7 on
hand - oh well! What's the correct torque on the 3/16"
bolts? It seems that the MS20392-3C9 clevis pin on the
tailwheel rod should really be a -2C9. How am I supposed
to match drill that when I can't see whether it's lined
up or not? I don't seem to have enough of these 4RX3/8-THA-SS
screws or MS21047-L4 anchor nuts. Wiring is a can of worms
unless you plan it right. And the painting - well how
hard can it be?
Now if you didn't get any of that, don't worry. But I
am trying to show that this is an aircraft you are building.
I know they say it's not a piano, but you have to do it
right and learn a lot fast. Then again, with the 100 sheets
of engineering drawings, Internet group support and easy
communication with Sonex, I was comfortable that I could
solve any problem that came up. There were plenty, but
I got through them just fine.
So it was that I worked my way through the elephant,
eating one small bit at a time. And then one fine day,
the workshop window was removed and the fuselage sat gleaming
out in the sun.
Not long afterwards I arranged the final inspection. Fortunately
the Sonex is small enough to rig up in our front yard,
so that was convenient. The inspector was thorough and
practical.
Then there was the move to the hangar, three trips in
the summer heat. The final rigging was down to myself
and just me, but I managed it with plenty of cushions
and patience.
Soon it was time to get in and start it up. After so much
time in the workshop it was strange to actually use the
controls and hear the engine. It felt alive. Quickly on
to taxi testing - a piece of cake, like a go-cart with
that steerable tailwheel. Not much point in doing any
more of that. A couple of blasts down the strip and it
was time.
Well, the first flight was over with before I knew it.
On starting the roll down the runway I realised that I
had not checked whether the airspeed indicator worked.
So I pushed the speed up, knowing that, with the stall
speed of 40 kt, I should stay below 30 for safety. I gave
it some power, kept it straight and watched. The needle
came alive. It's just touching 30 so it works. Hey - it's
flying. Well that got the hard part over with real quick.
No problems and all systems go. I climbed straight out,
watching the instruments like a hawk.
Engine temps were up with the 40ûC day, but well
within limits. Coming up to a comfortable height I looked
back and the runway was way back in the distance. This
thing really goes. I hope the engine keeps going. Somewhat
disappointed with the handling, then I realised that I
had not pulled up the flaps. It really makes a difference.
A bit more messy flap work later saw me on approach and
probably the best landing I have ever done. Taxi back
and shut down. Fantastic! I want to do it again, but maybe
later.
Then all too soon there was the big prize at Narromine
and a gathering of Sonex builders just as keen as I was.
It was a bit strange after being the only Sonex builder
in Australia for so long.
Now almost a year later, what's it like to fly? It's like
nothing like I have experienced before. The control feel
is solid but not heavy. It's very responsive and yet not
light and twitchy. The Jabiru 2200 has plenty of power
with significant torque effect on take-off. There is quite
a large trim change on lowering or raising the flaps.
It climbs out easily at about 80 kts and settles to cruise
at around 110 kts at 3100 rpm. Top speed straight and
level is 140 kts, VNE is 170 kts. Stall speed is 35-40
kts and no vices before the gentle stall.
The main thing I needed to get used to is the outstanding
visibility and easy manoeuvring. It's a zippy little machine
and G force can build up fast with a pull up or high bank
turn, enough to make me feel queasy. Fuel burn is about
15-16 lt/hr around the paddock and 14-15 lt/hr on a long
trip.
For me that's more than enough. But there are other options.
There is the 120 hp Jabiru 3300 engine, or an 80 hp VW
derived engine in kit form. Or alternative airframes are
the Y tail "Waiex" or the powered glider version,
the "Xenos".
The Sonex kit now provides cut and drilled components
that save many hours of layout, cutting and drilling.
It isn't like an "A meets B" kit but neither
is the cost. If you don't have the money for a complete
kit you can build it a piece at a time as your budget
permits.
So what's the future for the Sonex in Australia? I have
22 builders listed and there are likely to be more I don't
know of. The plan numbers are now well into the 700's
and the factory is shipping kits as fast as they can move
them out the door.
My thoughts - it's a little beauty and the kit's a bargain.
Building a Sonex is a tremendous experience with plenty
of support and you end up with a fantastic little sport
aircraft. I'm off to the field now.
