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The Joy Is Repeated

Completion of a Sonex

By Karl Storjohann, EAA 744612, feedpro@bbcwb.net

Moments after a successful and rewarding first flight

Karl Storjohann is a seasoned commercial-rated pilot, now enjoying sport pilot privileges and social security. Methodically working through his first build, he credits the plans and parts supplied by Sonex for much of his success. Working daily for nearly three years netted him the joy of having built this plane, with his own two hands, and being the first person to fly it. He likens his first flight in his new plane to his first solo flight 46 years earlier.

The FAA inspector from the Flight Standards District Office (FSDO) has been gone two hours; the airworthiness certificate is in hand. The cowl has been replaced and all inspection covers are reinstalled. It’s time; I’ve waited long enough. There are no more excuses.

The wind is slight. A friend has just landed at my little grass strip, so I have someone available if something bad happens. The moment arrives to make the first flight. Wow, I haven’t felt this way in years as I face into the wind and slowly advance the throttle to see if the Jabiru engine will take full throttle. All of a sudden, I realize that this feeling is exactly the same one I felt 46 years ago during my first solo flight. Now, over 6500 hours later, there’s the same excitement, and yes, apprehension of what’s to come while I perform the first flight in a Sonex that I had built myself over the previous three years.

I certainly didn’t ask my wife for permission to make this first flight, as she can’t believe that something that I built would be safe. I don’t know why she feels that way – it’s just a wife thing, I guess. As the airspeed builds, the engine sounds as if it wants to keep going. So I slowly bring the stick back and we’re flying. What a thrill. But it isn’t the thrill of flying, which is always there, but the thrill of flying something that I built. All homebuilders know what I mean, but the rest of you can’t really understand until you make the first flight in something that you built. In the meantime, remember the feeling of your first solo flight; for me it’s nearly the same.

Not everything is perfect during this first flight, nor did I expect it to be. The left wing is a little heavy, but I can fix that easily because I know this yellow Tweety Bird. I know everything that makes her tick, and if something tock-ticks, I can fix that once back on the ground. The only thing I didn’t have control over was the engine. I didn’t build that, but some very good folks at the Jabiru plant did. They test-ran it before shipping it to me, so I did expect it to run great. And it does. Still I worry, maybe a little too much, since it purrs like a kitten. Here I am, acting like a mother hen.

As I circle the airport, there are other small things that became evident I would need to handle. The flashing low-fuel light was irritating me since I knew the tank was full. The fuel flow is indicating 9 gallons/hour when it should be in the area of 5 to 6, but that’s the fun of homebuilding; you’re in charge of fixing important things after you land. In addition, this is the reason why I have to fly 40 hours in the local area and not haul passengers.

It’s now time to land since I don’t have anything to write on to make notes of my observations. Bad planning on my part, but the excitement of making this first flight took up all my brain activity, leaving no room for logic. I bring the power back and establish a perfect 4-degree glide on final. I let the airspeed continue to degrade through 60 mph as I cross the fence and slowly fair at one foot above the runway. Reducing power to idle, we’re immediately down. Wow, what a feeling of apprehension I just went through. It may be a new flying machine, but the feelings that the airframe transmits are the same as everything I had flown previously. What exciting times lie ahead as I explore the limits of this airplane and correct issues that arise. I can hardly wait for the next great flying day. Thanks go to God for an opportunity to experience once again the feeling of that first solo.

How It All Began
The thought of building my own airplane never appealed to me before. It just crept into my mind after a trip to EAA AirVenture Oshkosh in 2007. I was looking over the Sonex display at AirVenture and got to thinking, “This could be fun to do in my retirement.” I had just finished modifying a Cessna 175 from tricycle gear to conventional gear (tail wheel) and learned how to handle a rivet gun and buck rivets by myself. Then Les Mittleider, the airframe and powerplant (A&P) mechanic with inspection authority (AI), would come along and mark the ones he didn’t like, causing me to drill them out and do it again. Got to thinking, “I’m getting good at this.”

In retirement, I used my Cessna to travel to the Idaho backcountry and fish, so another airplane, capable of aerobatics, would be just the thing I needed to keep life exciting. At least, that’s how I justified the thought of building a Sonex. It was capable of aerobatics. Little did I know at the time that it wouldn’t be long before I needed to fly as a sport pilot.

Building the wing spar
Once Karl set up his shop, the first order of business was to build the wing spar.

This first flight in my Sonex ended nearly three years of building. The project turned into a very satisfying experience and was worth every minute of time spent. The construction started in my workshop that I previously used as a woodwork finishing facility. All the woodworking equipment was moved into storage, and a large worktable was constructed on heavy steel sawhorses in the center of a 14 x 24 foot area. This worktable was leveled out so that all my construction would be on a level surface, consisting of two long pieces of 7/16-inch oriented strand board that were from the original crate for the Sonex kit. When fastened together in two layers, they made a solid surface that I could use as a backing to drill holes into, without caring what happened to it.

My first try at plans-reading began in March 2008 after taking the construction course at the Sonex factory in Oshkosh, Wisconsin. The first day was a total loss, as I spent all waking hours studying the drawings, trying to learn to read the plans and understand what they were telling me. As I continued to study the plans, gradually they started to talk to me. I would then build a small part with this new understanding. Then I built another and another until they began to fit together and form a meaningful piece.

Sonex plans
Larger view

If I made a mistake – and there were many – I made that part over after first calling a supplier for more material. However, I’m proud to say that I don’t have enough messed-up parts to build another plane. In some places there are rivets installed to fill holes accidentally drilled in the wrong spot. They don’t hold anything together, but an empty hole would be very noticeable and lead to embarrassing questions. This way most people wouldn’t even notice a row of rivets perfectly spaced and aligned that aren’t doing anything other than filling holes.

I decided that I would build wings first and spent the next several months building up spars with solid rivets. This experience of riveting layers of aluminum into an ultrastrong spar builds confidence in the strength of the design. After drilling out “smiley faces” and reinstalling, I moved on to wing ribs, covering them with big sheets of 6061 aluminum.


I was thankful that I purchased a kit containing precut skins marked with laser-cut alignment holes. I wouldn’t have wanted to try to cut the skin correctly, then mark and drill all those holes, expecting that they would be perfect and the wing straight. You have to admire a scratch-builder. The kit approach allowed everything to line up perfectly. It was such a joy to bend the leading edge skin over and have the holes line up on the other side.

Dimple leading edge skin for flush rivets

My strategy behind building the wings first was to move the completed wings to my hangar, thus making room for the next build project. This worked well. As the construction progressed, I became better at plans-reading, so each morning I jumped out of bed excited. I just couldn’t wait to get into the shop, fire the wood-burning stove, and git-’er-done. Never have I worked on a project that was so satisfying. Each day, there was just one page of the plans to be studied. Then I would build the parts on that page which would eventually become a part of something that others would recognize as airworthy. The United Parcel Service driver is probably able to build his own homebuilt now, since he was able to keep track of all my progress.

Why Did It Take So Long?
Now the question that enters a person’s mind on reading this is, “Why did it take nearly three years to build? It sounds as if you were moving right along.” Well, every hole first needed to be drilled with a number 40 bit, deburred, clecoed together, then drilled out with a number 30 bit and deburred again, then clecoed back together before you can rivet. The leading edge skins of the wings also needed to be dimpled. All of this took time and soon became a chore, although a necessary chore, but definitely not the most fun part of building. Also, there were over 3,000 rivets installed. Some were drilled out and installed again, just for fun…not!

Making small parts at the bench

Assembly of fuselage

Fuselage box taking shape

Instrument panel and rudder pedals, plus part of spar box

Rigging the wings required the help of Monte Orr (on left) and Dave Carlson.

Eventually I reached a point after completing the fuselage that I needed to move the project to my hangar. If I put the gear legs on the fuselage, I wouldn’t be able to get it out the 4-foot shop door at home. Hey, at least I realized this in advance! Otherwise, I would have been removing the end wall of my shop. The fuselage was loaded on my flatbed trailer and hauled the 17 miles to the grass strip at Hay Springs, Nebraska. This hangar has an oil furnace, but it isn’t insulated. So if the wind was strong in the wintertime, I couldn’t stay warm. Most days it was comfortable. In the summer, the hangar door was opened and a fan ran inside to circulate the air. This made it livable, and progress continued with time out for putting up hay for my livestock.

The Sonex started looking like an airplane as I installed the tail feathers and conventional landing gear, then hauled it 15 miles into the country to get it painted by a young fellow (well, younger then I am) with an auto body shop on a ranch. Remember, this is western Nebraska, and folks in these parts are able to do many things, especially farm boys.

Part of the Sonex comes back from painting. Note the tail pull handle inside of fuselage.

After the fuselage was painted, I hauled the wings over to him in a wing rack that I had built using strips of carpet to cradle the wings in an “on leading edge” position. Leaving the wingtips off allowed the painter to be able to build a rack to rotate the wings while painting. After discussion about not putting on too heavy a coat of paint, thereby not adding much more weight, I left him to his work of making Tweety Bird yellow.

The painting took place in June 2010, with the rest of the year spent mounting the engine and wiring the panel to the engine. Others have said, “When you are 90 percent done, you only have 90 percent left to do.” This is very true. The wiring took far longer than I would have thought, but it was still fun work. Here you have a complete fuselage with tail feathers and wings that look like an airplane, yet it’s far from flying. You still have to build the canopy, windscreen, cowling, well, you get the idea.

Mounting the Jabiru 3300

“Cowl work takes nearly forever.”

Then the day finally arrived for the inspection. The FAA inspector from the FSDO showed up to look her over while I was praying for that airworthiness certificate and a flight test area I could work with. I knew it would go well when I heard him say, upon first seeing my Sonex, “This looks like it is not going to be too difficult.” First impressions are very important to the outcome. I was popping shirt buttons when he stated, “You obviously have built before.” Nope. This is the first.

Nothing left to do but to do it.

As years go by and more and more friends learn you’re building an airplane, you’ll find their first question is always “When will it be done?” My answer: “Tuesday.”


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