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The Leonard Brothers Build a Pair of Thatchers

Story and photos by Will and Phil Leonard, for Experimenter


Building an experimental aircraft can be very rewarding, potentially doubly so if done with a friend. That being the case, how much better could it be if the plane was built with a brother? Will and Phil Leonard found out that it’s especially rewarding when a few years ago they saw to completion a pair of exceptional Thatcher CX4s.

It all started in 2003 when my neighbor and I made a long-desired trip to EAA AirVenture Oshkosh for a few days there. I came home all fired up to get back into actively flying again. I had obtained my private pilot certificate in the early 1970s, as well as a sailplane rating, but hadn’t flown any aircraft since the early 1980s. I wanted to buy something small that I could fly out of a local grass strip. So I found a Hi-Max in Dunn, North Carolina, bought it, and my brother Phil, EAA 765985, helped me pick it up and bring it home to Independence, Virginia.

After sharing stories of my trip to Oshkosh with Phil, we were both excited about flying again.(Phil had started his private pilot training in the 1970s, too, but hadn’t finished. The bug bit him again; he decided to finish his training. He got his certificate in early 2008 and went on to get a tailwheel endorsement later that year.) Phil then brought up the idea of building an airplane. During the long discussions on what to build, we decided on the CX4 and also decided to head for Florida-based Sun ’n Fun in April of 2004 to look at the prototype and meet the designer, Dave Thatcher. That’s all it took: Phil bought the plans, I reasoned that building two of them side by side would be about as easy as building one, and that’s when the project(s) took off. Later I purchased my plans from a gentleman who didn’t think he could finish due to his age and health conditions.

Phil trying on the prototype CX4 at Sun ’n Fun 2004

We decided to build the planes in the garage that Phil used for years in his auto repair business (from which he’s now retired). The place needed rehabbing. Heat and air were installed, things were rearranged for aircraft building (as opposed to auto repair) over many months, and even a side room was added to the garage.

During the summer of 2006, we started ordering and taking delivery of most of the materials we needed to start the building process. Everything we needed was in place by Thanksgiving. In the following week, we embarked on the journey of cutting, deburring, bending, drilling, and riveting metal!
In April of 2007, we returned to Sun ’n Fun once again to pick up a 2180-cc Mosler conversion VW engine Phil had purchased from a gentleman in Punta Gorda, Florida. Phil got quite a deal on the engine/prop package, and we returned to North Carolina really fired up to continue the building.

Getting Started
Since I lived near Independence, Virginia, some 210 miles away, I would come down for a week or two during which we would spend 8 to 10 hours a day building. Afterwards, I’d return home for a week or two. This was the routine throughout the building process, and it wouldn’t have been possible without the extraordinary patience and understanding of my wife! Sometimes Phil worked on his aircraft while I was gone, sometimes not. When I returned, I’d catch up and we’d enter new territory again together. His was the lead/test plane. We found out quickly that once we had done something on his plane, it took a lot less time to do it on mine—this is the great benefit of experience. Neither of us had built an aircraft before, and although I had some experience working with wood and fabric aircraft, the CX4 is all metal and new for both of us.

We modified the nose piece and bottom receiver on this press in order to squeeze the driven rivets. The pressed rivet heads are very consistent and clean and don’t put stress on the components like hammering can.

We each have many years of experience repairing and building things; Phil is a career auto mechanic, and we each have home construction, electrical, plumbing, etc., experience. We weren’t apprehensive about the process, but nevertheless we were cautious about following the plans and talked a lot of things over before proceeding. There were of course moments of frustration and head-scratching, and a few blue words scorched the air now and then. But overall it was relatively easy to follow the plans and build the planes. Dave was always available to answer questions and guide us. Both of us agree that he is one of the finest gentlemen we have ever met and an absolute delight to work with. That was an unexpected bonus to the building process.
Construction Begins
So just how do you start building an aircraft when you’ve never done it before? Well, you start with the plans and builder manual, both of which are excellent for the CX4. There’s a detailed material list provided with the sources identified and prices, though they’ve changed over time, always up! In the case of the CX4, after you’re fairly familiar with the plans and manual (a lot of which you won’t really understand until you get to that particular activity), you have to do some woodwork first! Yes, I know it’s an all-metal aircraft, but you need to form that metal over something. Wooden forming blocks are the answer, and I made ours while Phil was upgrading the garage.

Mounting of the nose skin to wing

The forming of the various pieces is simple, easy, and goes very rapidly, much faster than you might think. In fact, it takes longer to cut the material to shape than it takes to form it. While one of us worked on these, the other worked on other components. We actually started our building by making the center-section spar and wing spars first. We didn’t care for the results of our first attempt, so we trashed it.

This gave us the opportunity to build the alternate spar design that was specified after our plans were published. They came out excellent! No warps, no bends or twists. These were the main items formed by driven rivets (entirely new to us) instead of pulled Avex rivets which are commonly used on the rest of the plane.

Making the spars, setting the dihedral, mounting the wing ribs and center-section ribs, then covering the wings is phase one in the construction. By the time you’re finished with these parts, you’ve mastered the skills needed to do the rest of the construction.

Buildup of the seat pan. In place here is the seat back bulkhead.

The next step involves mounting the ribs to the spars. Keeping them square and properly aligned to the spar is the most important part of this process. A 16-foot (level and square) worktable is the largest item needed to build this plane, but it’s a necessity! We had a nice one retrieved from Square D’s renovation that was going to the dump!

Mounting the rear ribs and skinning the wings were the next steps, and we were gaining speed and confidence in the process. Again, keeping everything level and square is of utmost importance, but using simple jigs and clamping setups keeps everything where it should be until it’s drilled and riveted.

Now comes the fun part. When this is finished, it’s going to look like an airplane! Keep in mind that this plane can be built with ordinary hand tools, a 14- to 16-foot table, and lots of patience. There are no compound curves in the metal - it’s all flat sheet stock, cut and bent to fit.

The simple jig is illustrated above and shows locating bulkheads, installing rear upper longerons, and finally, skinning the top of the rear fuselage.

It was then time to frame up the remainder of the fuselage. This is done by building a simple jig on the tabletop to keep the rear frame level and square. (That keeps coming up, doesn’t it?)We chose to add lower longerons for strength and ease of handling, rather than fold a lip on the bottom skin. Then we removed the fuselage from the jig, flipped it over on sawhorses, X-braced it, and returned it to the jig for bottom skin fitting.

After the fit was satisfactory and clecoed, we again removed it and began the riveting process.The turtledeck can be installed anytime after the initial skinning because you don’t have to get into that area for any future work. It must, however, be installed prior to canopy fitting.

There’s a lot of trial fitting of the parts prior to final installation. The above photo illustrates the making and fitting of tail assembly after fuselage is on gear.

We moved on to installing the main gear and the tail wheel. Now we could move the planes around and finish skinning the fuselage and build up the tail assembly. Framing and fitting the vertical and horizontal stabilizers and the elevator is straightforward, but it can be tedious in detail. Close attention must be paid to avoid a warped fin or horizontal stabilizer.

Aileron and elevator control stick

When the aircraft is skinned and geared and the tail assembly is installed, the next major step is control installation. There’s nothing different here from any other aircraft build—follow the plans and adjust the rigging until they’re balanced. The following pictures depict some of the control components used in the CX4. 

The Engine
We were then at the point of working on the firewall-forward. We installed the motor mounts, mounted the VW engines, and proceeded down the long road of wiring, cowl baffling, and fitting. Of course there are instruments to install and connect. By leaving the windshield and canopy till later and not covering the front sides of the fuselage, we had better access to mount the fuel tank, connect fuel lines, etc.

Phil got a great deal on this used Mosler 2180-cc VW engine that he picked up the year before.

Nearly Finished!
If you’re like me, you’ll want to wait until this phase to install your windshield and canopy. Phil, on the other hand, decided to put his on earlier in the process. Installing the windshield and the preformed canopy is the most difficult part of building the CX4, as with many other homebuilts.

Great care must be exercised to avoid cracking the Lexan when drilling and fastening it down. Using a proper drill bit and making certain it’s not under stress when the bolts are tightened ensures success.

After many hours and lots of patience, we arrived at the day when the aircraft were ready to paint. Seats, instruments, fairings, and wheelpants had all been installed and tested as best they could on the ground. The engines had been run and wiring checked, radios installed, and there was nothing left to do but paint the final product.

After so many months of building these aircraft one piece at a time and seeing them finally complete and painted, mixed emotions were heavy! Too quickly we had nothing to do, or so it seemed.

It Was Finished!
All that remained was to transport them to Smithfield Airport in North Carolina (KJNX), get them certificated, and test-fly them. I don’t know about Phil, but I had a hollow feeling that something was missing. It took a few days to adjust to the new adventure.

Probably the greatest pleasure I derived from the experience was spending so much time with my younger brother and us getting to know each other better. You should know that there’s quite an age difference between us. At the time of the first flights, Phil was 58 and I was 71. Going back further, he was just a little guy when I left home at 18 to make a career out of the U.S. Air Force. Phil is also an ordained minister and pastor of the church he founded. We had many, many moments of laughter and storytelling. Fortunately, we’re similar in our beliefs and outlook on life, so we get along well.


Another benefit and pleasure was the interest it stirred up in the neighborhood and among our friends. Once the word was out that we were actually building two airplanes and intended to fly them when finished, well, they just had to see this with their own eyes! The type and manner of questions and comments were hilarious at times, and I still laugh about them today. Needless to say, this slowed down the construction somewhat but was worth it in the end.

The two planes were finished in August of 2008 and moved to Smithfield Airport for certification and flight testing. Both aircraft were certificated on August 15, 2008, and the phase one test flying could begin! Or so we thought - in fact, after taxiing tests and engine run-ups, we found that a few more tweaks were needed. The landing gear needed alignment, brake pedals needed adjusting, tail wheels needed adjusting, and in my case, replacing.


No major problems were encountered, but progress was slow. Finally, Phil was satisfied with his plane, N458CX, and took to the air! She climbed like a rocket, purred like a kitten, and flew beautifully! The landing was an adventure in itself, but he did get it down safely in one piece and was all grins! After watching his landing attempts, I got a little nervous. I hadn’t flown recently and last flew a taildragger in the 1970s. Reaching the conclusion that I needed to get refreshed with an instructor in a Cub, I did exactly that.

However, since Phil supervised and helped build my engine, he insisted that he test-fly N433CX in the meantime. He did and she performed equally well. But he encountered a rumbling vibration on the first flight and immediately throttled back. It went away, but he returned to the runway quickly as a precautionary move. We couldn’t identify the source but thought it might be an unbalanced propeller spacer. We pursued this possibility and a left-wing heavy condition (corrected by control adjustment and small trim tab), and it was test-flown again with no vibration. It turned out the rumbling was the wheels still turning after takeoff and spinning up. Applying the brakes just after liftoff cures this problem.
Both our aircraft are a little heavy for the model, but the performance figures are right on the specs laid out for the CX4. We couldn’t be happier with how it has all turned out, and we love our “twins”! Phil has conquered those landings with just a little more speed on touchdown!

The Leonard brothers realized a dream and made it to Sun ’n Fun 2009. They were parked in a place of honor next to Dave Thatcher’s prototype, seen in the background.

See all the build photos here.


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