Oba St. Clair

The Trial


On September 24, 1953, Jim Walker filed his case against L.M. Cox Manufacturing Co., Inc., charging them with patent infringements on two counts; the Bellcrank system and the control handle/reel. Jim also charged that the trademark U-Control had been indirectly used by Roy Cox and that constituted unfair competition. Jim offered as evidence:


• Copies of his patents and trademarks • Several magazine articles and books

• Drawing of his control system and Roy Cox's TD-1 airplanes

• A model of the framework of Oba St. Clair's airplane

• A Fireball and parts

• A Handy Reel, Skylon Reel and U-Reely

• A letter from W. Elmer Ramsey (one of Jim's attorneys) to Roy Cox

• Several airplanes including, a TD-1, Firebaby, Zing, Monogram Piper Cub kit, Testor wooden model and a Testor's Sophomore 9 kit

The patent infringements were charged by Jim because Roy had been selling his TD-1 airplanes that used a bellcrank without a license. He also charged the Skylon Reel was a copy of his UReely and also made without a license. He charged that when Roy had his TD-3 airplane boxes printed with the words, “All You Do is Control It,” he was obviously cashing in on the trademark U-Control and taking unfair advantage.

Jim's statement to the court said that 90% of all model airplanes flown at that time in the United States used U-Control and that it had grown to a multimillion dollar business by his hard work, substantial investment, time and ability.

Roy Cox's statement to the court said that theL.M. Cox Manufacturing Co., Inc., was aware that the patent had been issued to Jim Walker, but they had been illegally issued because the original inventor named was not the original inventor, that the ideas were known and used by others prior to the patent issue.

Roy challenged the claim that the trademark “U-Control” was owned by Jim Walker.

Roy Cox listed 14 patents that preceded Jim's two patents and listed the following publications:

• Popular Science magazine, April 1939, page 107

• The Telephone Register newspaper, McMinnville, Oregon, July 15, 1937

• Model Airplane News magazine, November 1937

• Model Airplane News magazine, January 1938 Roy's evidence included all of the above mentioned, plus his star exhibit, Oba St. Clair's original Miss Shirley airplane, three TD-3 airplanes, two molded from clear plastic to show bellcrank action.

Altogether, Roy introduced over 50 exhibits of evidence.

On February 11, 1955, Jim Walker and Roy Cox put on a flying exhibition for the court. Jim flew his three Fireballs at once. This may have done Jim's case more harm than good.

When he flew his Firebaby with Roy Cox's designed Skylon Reel to illustrate that it performed the same function as the U Reely (lengthening and shortening of the flying lines during flight), the court did indeed conclude Jim was such an expert that he did not prove that the average flyer could do the same thing and Jim lost that point.

Roy Cox flew his TD-3 and believes he did everything Jim did except fly three at once. Roy had one airplane control system set up as Oba's airplane and one set up as manufactured. The flying went well for all. Each flyer surely returned to the courtroom thinking he had proved his points, but the victory for Jim was to be short lived on that day; he lost his first two points.

The court ruled the defendant had not infringed on the trademark “U-Control” and had not engaged in unfair competition.

Roy's attorney asked for a judgment in favor of L.M. Cox Manufacturing Co., Inc., at that time, but didn't get it.

The case to follow was equally interesting. Roy produced a list of 15 people who could testify to prior use of the control system invention in question. They had all seen Oba fly his airplane more than a year prior to the issue of Jim's patent.

Roy or his attorney somehow had found an ad in a January 1938 issue of Model Airplane News listing for sale, construction plans and specifications for building a Miss Shirley” Control Line airplane. They came up with a modeler named Wilbur Hahn, who purchased a set of drawings and built and flew the Miss Shirley in 1938. There was little doubt as to how the case would come out – only a question of whether or not Jim would win any points.

He did win two points: the tradename “U-Control” was declared his, plus the court referred to him as “Super Expert.” The court ruled that the control patent was void and invalid. The court also ruled that Jim

Walker had seen Oba St. Clair's airplane in the spring of 1937, although Jim testified he didn't remember.

The court ruled that the control handle patent was valid only on the points that related to reeling the control lines out and in during flight.

The decision was all in Cox's favor. It must have been hard for Jim to take, but the worst was yet to come.

The judge began to lecture Jim – scolding him for not keeping records of his testing, comparing him unfavorably to Oba, who was a mill worker and had complete documentation and proof of everything. The judge sent a letter to Oba St. Clair (Oba only testified by deposition; he didn't go to the trial) naming Oba as the “father of Control Line flying.”


Information about Oba St. Clair is taken from two articles that appeared in Model Builder magazine’s November and December 1981 issues. The articles were written by Charles Mackey and Dale Kirn. Charles Mackey submitted the information to the AMA History Program.