visitor Stephen B. just wrote asking me to post this article for
the Folkerts SK-3 Speed King. As the designation suggests, there
were two prior iterations of the airplane. The Folkerts was a paradigm
breaker in its day (circa 1930s) for using an inline engine rather
than a radial. The story mentions that even "today" (...being 1973)
the battle of opinions continues. Guess what? In 2012, there is
still no agreement - take a look at the variety of racers at Reno.
Although there are no construction plans, the inestimably talented
Björn Karlström provided a detailed 5-view of the airplane.
Folkerts SK-3 Speed King
Racing great, Harold Neumann, and the Folkerts Special "Toots."
Small even when compared with a Formula One racer, this powerful
machine demanded the finest of piloting skill.
For almost as long as there has been air racing, there has been
a battle between radial and in-line engines. The prettiest, sleekest
machines have packed straight or V engines into their graceful cowlings
... but most of the big winners have carried bulky, round engines
This early Folkerts exemplified its designer's concept - minimum
airplane with the biggest engine that fitted and careful attention
|Specifications of the SK-3
Wing Area-51 sq. ft.
|Empty Weight-840 lb.
Gross Weight-1385 lb.
Top Speed-over 275 mph
No doubt about it, an in-line engine is a lot
easier to cowl in, and the result is a much cleaner and faster airplane.
if the comparable radial engine has about the same power, and that's
the catch. Engine manufacturers have long made far bigger and far
more powerful radial engines than they have in-lines. And as any
racing person knows, you can't beat cubic inches!
true back in the 1930s, when the fat Gee Bee was faster than any
of its slimmer rivals. And it's just as true today, when you pit
Bearcats and Sea Furys against the slender-but-less-potent Mustangs
and Cobras. What chance does a 1650 cu. in. Rolls Royce V-12 have
against a 2800 cu. in. Pratt & Whitney? Attempts to even the
odds have usually resulted in V-12s so souped-up that they won't
hold together long enough to finish, let alone win.
equally as one-sided back in the Golden 30s, when eight of the ten
pre-World War II Thompson Trophy Races were won by Pratt & Whitney-powered
airplanes. Of the other two, one was a French government-sponsored
airplane that simply "out-monied" everyone else. And the other was
a slick little Menasco straight-six job with 1/3 the cubic inches
of the next three racers that followed it across the finish line.
And no more than half the horsepower.
How can it be done with such a handicap? Well, for one thing, a
sharp engineer can create a much cleaner, smaller airplane behind
a slim in-line engine, and any designer knows the shortest route
to speed is streamlining, not power. So, while a powerful streamlined
airplane is better than an underpowered streamlined airplane, the
edge goes to streamlining. At least that was the way Clayton Folkerts
By 1937, Folkerts was up to 400 hp. Had three times the power
of today's Formula One with 3/4 the area.
Competition more than doubled its displacement. The six-cylinder
Menasco Super Buccaneer was shoe-horned into this tight cowling,
in Thompson winner.
Build an airplane as small as possible and give
it the biggest engine that will fit. And if you do it right, you
should win a few races. For Folkerts, of Bettendorf, Iowa, and later
Lemont, Illinois, it started in 1930 with the Mono-Special, later
called the Folkerts SK-1 Speed King. Powered by a four-cylinder,
in-line 310 cu. in. American Cirrus engine rated at 90 hp, it was
a strut-braced mid-wing with rather crude landing gear. Careful
work brought its speed up from 142 mph at Chicago in 1930 to 187
mph at Cleveland in 1935, though by then it was called the Fordon-Neumann
Special and was being flown by Harold Neumann. It raced until 1937
as the Whittenbeck Special and then simply vanished.
Clayton Folkerts didn't. His second racer appeared in 1936 and was
a major improvement over the first. The SK-2 "Toots" firmly established
his concept of a racing airplane: Minimum wings (50 sq. ft., compared
with 66 sq. ft. required of today's Formula One racers), maximum
power (supercharged 363 cu. in. Menasco C4S Pirate four-cylinder,
rated at 185 hp), and one of the earliest, simplest retractable
landing gears. With 1935 Thompson winner Neumann at the controls,
the tiny SK-2 outran several more powerful rivals to place fourth
in the 1936 Thompson at 233 mph. Roger Don Rae got its speed up
to 243 mph in 1937, and the airplane ended its brief career when
Gus Gotch crashed in it at Oakland in 1938.
With his theories
pretty well proven, Clayton Folkerts moved ahead. His 1937 racer
was simply more of the same: A few inches more length and wingspan,
considerably greater weight ... and lots more power. The little
Menasco was replaced by its big brother, a six-cylinder, 489 cu.
in. C6S-4 "Super Buccaneer" souped-up to deliver some 400 hp at
3300 rpm. It had three times the power of a Formula One, yet only
3/4 the wing area. This had to spell "performance," but it could
also spell "trouble."
Simple retractable gear was a masterpiece of engineering.
But Folkerts knew enough about designing an airplane to
keep it within reasonable handling characteristics. In fact, the
pilot chosen to handle the new baby, Rudy Kling, had fewer than
200 flying hours when he sat on the starting line for the Greve
Trophy Race at Cleveland, on Sunday, September 5, 1937. Lined up
alongside Kling were six other Menasco-powered airplanes, in what
must have been one of the classiest collections of racers ever seen.
And at the end of ten laps of the ten-mile race course, they were
almost as closely bunched as they had been at the start:
Kling beat out Steve Wittman by 1.9 sec. and Gus Gotch by 4.5
sec., as they averaged 232.27 mph, 231.99 mph and 231.59 mph, respectively.
competition with the best small racers in the world, Folkerts and
Kling had proven that their team was a most effective one. But the
big test was yet to come. Prior to the Thompson Trophy Race, Kling
entered the SK-3 "Pride of Lemont" in a qualifying race against
Wittman in his big Curtiss-powered "Bonzo," Roscoe Turner in the
Laird-Turner "Meteor," a Ray Moore in a Seversky military prototype.
Giving away 600-1300 cu. in., Kling was not expected to do very
well, and he placed third at 240 mph, behind Wittman's 259.1 mph
and Turner's 258.9 mph. But he was less than a minute back at the
finish of the 50-mile race, and began looking forward to the Thompson
with growing enthusiasm.
That race was for 20 laps of the
ten-mile course: 45 minutes of hard, fast, on-the-deck flying. With
insufficient power and insufficient experience the Folkerts-Kling
combination was seen as a dark horse, at best, because they were
pitted against the best in the business - Wittman, Turner, Earl
Ortman and others.
At the takeoff, Kling's heavily loaded
little airplane found itself in eighth place in a nine-plane field.
By lap five, however, he had moved up to fifth place and was in
striking range of the leaders, if only a few of them would slow
down a bit, please! At the start of lap 15, he started to make his
move, and quickly advanced to fourth, behind Wittman, Turner and
Ortman. On lap 17, Wittman ran into engine trouble and had to pull
back on the power, moving everyone up a notch. Then, on the final
lap, another piece of good fortune, as Turner swung around to circle
a pylon he thought he had cut, and let Ortman and Kling go by.
As Ortman in the big Marcoux-Bromberg, and Kling in the
Folkerts, roared toward the finish line, Rudy Kling took advantage
of his excess altitude and dove to gain speed. He passed Ortman
as they approached the wire, and crossed it a mere 50 feet in the
lead. His margin was but .57 seconds, as he averaged 256.910 mph
to Ortman's 256.858 mph, in what is still the closest finish of
any "unlimited" air race in history.
The joy in the Folkerts
camp was as great as befits a long-shot victory. They had taken
on all the horsepower that American air racing could muster, and
they had won. And they had even topped the speed record set by the
great Jimmy Doolittle in his immortal Gee-Bee. All this was only
489 cu. in. and 400 hp. Indeed, it was a great day for the little
But it was the last great day for a Folkerts racer.
At Miami, a few months later, Kling was rounding the first pylon
of a race when a violent gust of wind caught the SK-3 and flipped
it into the ground. Neither survived. In 1938, the fourth and final
Folkerts appeared at Cleveland - the SK-4. It didn't race that year
because of wing flutter, but returned the next year and crashed
on a qualifying flight.
And so it was over, this tale of
the Folkerts racers. They had won and they had lost. They had lived
and they had died. And what remains is the knowledge that on one
glorious day, David had again beaten Goliath.
5-View of Folkerts Speed King SK-3
<click for larger
The AMA Plans Service offers a full-size
version of many of the plans show here at a very reasonable cost. They will scale the plans any size for you. It is always
best to buy printed plans because my scanner versions often have distortions that can cause parts to fit poorly. Purchasing
plans also help to support the operation of the Academy of Model
Aeronautics - the #1 advocate for model aviation throughout the world. If the AMA no longer has this plan on file, I
will be glad to send you my higher resolution version.
Try my Scale Calculator for Model Airplane Plans.
A couple different version of the
Folkerts Speed King are available from the AMA Plans Service
(pages 40 & 41).
Posted September 18, 2012