Pilot's Post - Race planes of the 1930s' - The Folkerts SK-3 and SK-4

01.05.2022

SK-3 "Jupiter, Pride of Lemont" had her first flight in 1937 and was the third in a series of air racers developed by Clayton Folkerts and was built for a mechanic, Rudy A. Kling from Lemont, Illinois as his personal racing aircraft. Developed from the SK-2, the SK-3 was slightly bigger with a larger Menasco C6-S engine.

SK 03

The National Air Races (also known as Pulitzer Trophy Races) were a series of pylon and cross-country races that took place in the United States since 1920. Although slightly different, these races were the forerunners to the Reno Air races that we know of today. The science of aviation, and the speed and reliability of aircraft and engines, grew rapidly during this period; the National Air Races were both a proving ground and showcase for this.

SK 04

Starting in 1929, the races ran for up to 10 days, usually from late August to early September and ran until 1939 but then went on a hiatus because of WWII. The races included a variety of events, including cross-country races. The more popular events were the Thompson Trophy Races which started in 1929 which were closed-course races where aviators raced their planes around pylons and the Bendix Trophy Race across most of the USA, starting in 1931.

A mid-winged conventional aircraft with a long and slender welded steel tube fabric covered fuselage, it had thin spruce wood plywood covered wings with split flaps. The conventional tailwheel landing gear was retractable. Powered by a 400 hp (300 kW) Menasco C6S Six cylnder supercharged inline piston engine, it was capable of a maximum speed of 267 kts (307 mph, 494 km/h).

Rudy Kling, who was involved in the construction of the aircraft, had only had 150 hours experience in a J-5-powered Travel Air before flying the racer. That did not stop him for finishing first at 232.27 mph (374 km/h) in the 1937 Greve Race.

At the 1937 Thompson Trophy race, he again finished first, this time at 256.910 mph (413 km/h). Sadly, on 3 December 1937, during the 1938 Miami Air Races, he crashed, dying on his 29th birthday.

The SK-4 was a copy of the SK-3 built with a new metal propeller specifically to attain a speed of 330 mph (531 km/h). She was entered in the 1938 races but withdrew due to wing flutter. During the 1939 races with Del Bush at the controls, she became the last in the SK series built by Folkerts when she crashed.

Classic Aircraft
History

Race planes of the 1930s' - The Folkerts SK-3 and SK-4

By Willie Bodenstein