By Budd Davisson, EAA 22483
This story was originally published in the March/April 2019 issue of Vintage Airplane, the publication of EAA’s Vintage Aircraft Association. It is the second in a series that will highlight fun and affordable vintage aircraft in each issue.
When walking around the grounds at EAA AirVenture Oshkosh, it’s hard not to notice a distinct trend among “magazine airplanes,” those that appear on the pages of aviation publications: They are uniformly restored to exact, original condition or beyond. Often far beyond. It has become the norm that vintage birds on display are often far more perfect than the day they left the factory. Or they’re customized to be a super slick version of the original airplane brought up to 21st century standards.
And then there is a smaller group of airplanes that, although sometimes unique or semi-rare, bear the marks of something that has been enjoyed and flown, and flown, and then flown some more. Like a well-worn pair of boots, they look, and are, comfortable. And that’s what attracted me to the Bohmer family Piper J-4 Cub Coupe: Not only was it a seldom-seen variation of the venerable J-3, but it had that “lived in” look, which said N33427 was one of those airplanes that most VAA owners could afford and enjoy without the sometimes-significant investment and daily worry that the fully restored birds often represent.
Alex Bohmer, a freight pilot based in Milwaukee, brought the Cub Coupe he and his dad own to AirVenture 2018 — his first time to AirVenture flying his own airplane.
“I’ve been coming for years, but this is the first time flying, and I love it!” he said.
Alex’s dad, a mechanical contractor, had learned to fly long before Alex was born, but fell out of the habit.
“I was born in January 1997. He had bought a Beech Sundowner but sold it a couple years after I was born because he wasn’t using it to fly to job sites anymore and couldn’t rationalize owning it,” Alex said. “However, it seems as if almost every pilot goes through a period where they are starting their career and their family at the same time and have to stop flying for a while. I guess I caused part of that gap in his flying, but we’re making up for it now.”
Alex said that when he was a kid his dad would take him to the airport where a friend of his had a PA-11 Cub.
“When I was about 12 years old, I made a deal with him where I’d mow the grass in exchange for time in the Cub,” he said. “I kept after it and soloed shortly after my 16th birthday and got my PPL right after I graduated from high school. Dad took me to AirVenture the first time in 2009, when I was 12, so from the very beginning I was pretty much bore-sighted on sport aviation, specifically vintage airplanes,” Alex said. “Dad had started to fly again, and we started looking around for airplanes that would fit our purpose. He didn’t really need a traveling machine, but he also didn’t have a tailwheel endorsement and knew little about tailwheel airplanes.”
Alex, however, was very much into tailwheels and, with a little prodding, was able to shift his dad’s focus to fun, little airplanes that they could both enjoy.
“We ran across the Cub Coupe in Faribault, Minnesota, which is pretty much local to us,” Alex said. “I’m not sure either of us had ever actually seen a J-4, and that appealed to us. It was something a little different. Also, compared to getting into a J-3, this was much easier and, once inside, it was surprisingly roomy. I don’t know the exact dimensions but compared to a Taylorcraft or Aeronca Chief, it feels much wider. Also, its wing is mounted much higher than most two-place, side-by-side classics so with only a little stretching, you can actually see over the nose and aren’t as blind out to the sides. Plus, the control sticks are shorter than the Cub’s, which makes them more comfortable to fly.”
The Cub Coupe was only produced for three years, 1939-1941, and only about 1,250 were built.
“I’m not sure if they discontinued it because of the war or because sales were slow compared to the J-3. It was probably both. … It’s unknown how many still exist or fly but best guesses are around 100,” Alex said. “Ours is a 1940 model so it came out of the factory with a 65-hp A65, versus the earlier A50 engine, and the cylinders are completely enclosed rather than hanging out like a J-3. The cowling is compound formed aluminum, and they are hard to find. Fortunately, ours is in good shape.”
Alex said that the airplane was upgraded to a C85 in 1980, which greatly increased its performance.
“I’ve never flown a 65-hp J-4 but knowing how much 85 hp improves the performance of a J-3, I can imagine that there’s a big difference,” he said.
When you stand back and look at a J-4, it’s easy to see its Cub lineage, which is partially the result of Piper’s design philosophy: Design as many new aircraft as possible but use as many common parts as possible. That’s why almost all Piper rag-wing airplanes from the J-3 to the Tri-Pacer use the same ribs, slightly modified tails, and the same basic wing structure with minor updates (aluminum spars).
“At some point, maybe in the 1940s, our airplane may have been damaged because the wooden spars were replaced with aluminum, which was standard on most postwar Cubs,” Alex said. “Also, even though there are no float fittings on the airplane, the logs show it was on floats in the 1980s right after it was re-covered. So, as with many old airplanes’ logs, there are some minor mysteries.”
Alex said people are constantly asking if they’re going to restore it, and his usual answer is — maybe.
“It would be nice to get rid of some of the dings and make a few repairs, which we do from time to time, but we’re unsure about restoring it,” he said. “Dad says, ‘A daily driver reduces any anxiety about maintaining the aircraft’s appearance in perfect condition.’ Grass stains, fuel stains, exhaust stains, a little chipped paint at the fasteners, etc. are all nothing to be too concerned about. When we take people up for a flight they can just climb aboard and enjoy the experience. We don’t need to worry about leaving a little scratch or fingerprints behind.”
Alex said the fabric on the Coupe is Razorback, which is a fiberglass type of fabric that the FAA recognizes as being a permanent covering.
“It supposedly doesn’t deteriorate and, in inspecting ours, we can’t find any deterioration except for minor scuffs. That is fine except it places a lot of responsibility on us to do really detailed interior inspections,” he said. “The fact that we have aluminum spars, however, greatly eases the worry about the wings. Internally, they are now all-aluminum with the exception of the carbon steel drag/anti-drag wires. The fuselage, of course, is subject to rust so it requires careful inspection, but we hangar it and, as far as we know, it has spent little time tied down outdoors. Its time on floats, however, keeps us poking around with mirrors and flashlights, but so far, so good.”
Alex said the Coupe’s performance is exactly what they need.
“We flight plan 70 knots, 80 mph, at about 4 gph,” he said. “We have no electrics to worry about and virtually no systems, so it’s an easy airplane to care for and very affordable. It’s nice to have an airplane that doesn’t become a major financial factor, as so many airplanes do. The Coupe is also a really good flying airplane and is literally a two-place Cub in most areas. Dad got his tailwheel endorsement in it, and we’ve taken it all over our area to fly-ins, etc. and have had zero problems with it. However, an investigation into a minor oil leak led to the discovery of a stripped through bolt on the engine case that required an engine teardown to install a Heli-Coil in the engine case. Other than its tired appearance, it’s what everyone actually needs in a Sunday morning flyer. We know it looks a little rough around the edges, but it more than makes up for that with affordability and fun.”
Cub Coupe Lookout – Details of the Breed (From Airbum.com)
Even though the Cub Coupe was produced for only three years, 1939-41, it managed to do a fair amount of changing, and all of these variations are worth knowing.
Most of the important changes came about after the first year of production with the introduction of the 1940 model. The most obvious change in the ’40/’41 models is that the exposed engine cylinders of the 1939 J-4 have been cowled in with an extremely pretty piece of sheet metal, possibly one of the prettiest Pipers ever built up to the Twin Comanche Tigershark cowls. At this time, 1940, they were doing their very best to give the Coupe a fancier look to entice more people into using it for business (we think). The cowl had a little chrome trim on it, and the instrument panel was completely overhauled and regrouped. All of the controls were moved into the center of the panel, which included putting the carb heat and fuel cut right in the middle, along with the mags and throttle. It was an unusual arrangement for an airplane, but one that is quite attractive.
All of the J-4s had the same structure, which is to say they were built like a J-3 Cub. The fuselage is steel tubing with wooden fairing strips covered with fabric. The wings have wooden spars, but the ribs are riveted T-shaped aluminum with wooden tip bows, as were all rag-wing Pipers. Only the spars in postwar airplanes were changed to aluminum.
As far as the wings go, it’s highly unusual to have a truly rotten spar unless the airplane has been left out in the open for many, many years and the fabric drain holes are plugged. But it does happen, and the spars should be looked at closely. Also, since the fittings at either end of the wing struts are steel, they should be inspected for rust and/or pitting.
On a J-4, something that tops the list in the investigation is the cowling itself. The original J-4 with exposed cylinders has a nosepiece and a top panel that are compound curved and were most likely formed in a die. The late models have even more complex metal work up front. While there are lots of companies making new sheet metal for J-3s, you might be hard pressed to find a good replacement cowl for a J-4.
As with all Piper aircraft of the period, the wing strut forks at the bottom of the struts have several ADs against them. By this time, if the airplane is flying, those forks have probably been examined and replaced. Since the forks (and new struts) are readily available, it doesn’t make any sense not to replace them.
The 1941 models came out with the 75-hp Continental that gave the airplane a much needed kick in the rear. Going up to a C85 via a field approval would make a totally different airplane out of it.
With the exception of the compound curved sheet metal, the J-4 represents absolutely nothing that is difficult to repair or hard to replace. Although it’s not a J-3 Cub, an awful lot of J-3 parts can be used to keep it flying. Otherwise, it’s just normal grassroots hardware.
Budd Davisson, EAA 22483, is an aeronautical engineer, has flown more than 300 different types of aircraft, and has published four books and more than 4,000 articles. He is editor-in-chief of Flight Journal magazine and a flight instructor primarily in Pitts/tailwheel aircraft. He is a regular contributor to EAA’s magazines.