Where the Fun Is: The Bohmer Family Cub Coupe

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.

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

“I’ve been
coming for years, but this is the first time flying, and I love it!” he said.

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

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.

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.

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