Hallmarks of Homebuilding

Thorp T-18 Advanced Metal Homebuilt Construction

John Thorp and his T-18 project at the 1963 EAA Convention and Fly-In.

The first T-18 to fly, built by Bill Warwick of Torrence, California, graced the cover of Sport Aviation in February 1965. (Note the bubble canopy.)

The individual “Hallmarks of Homebuilding” have been so designated because they fundamentally changed an element within the homebuilt movement. By definition, one very definitive hallmark is represented by John Thorp’s all metal airplane, the Thorp T-18.

By his own admission, Thorp stuck his neck out—“way out”—when he wrote in the February 1962 issue of Sport Aviation that “metal airplanes can be simpler to build than wooden airplanes.”

He set out to prove just that with his metal T-18. In May 1962, Thorp wrote, “My system of building a metal airplane without jigs employs a system of locating the rivet holes in the detail parts through the use of transfer strips.” This became known as the matched-hole tooling method and jig-less assembly system, which was described in detail throughout a 14-part series of articles on building the airplane in EAA’s magazine.

With all of the holes in the parts, assembly is accomplished in “Erector Set” fashion by clecoing the parts into assemblies and then riveting. This method provided several advantages, such as not having to build jigs, but also resulted in component accuracy, convenient assembly sequence, and simplified repair.

Apart from being one of the first all-metal homebuilts, the T-18 was the first homebuilt to use Thorp’s patented stabilator, or all-flying tail. Piper later used the design in their line of Cherokee aircraft, and today you can see extensive use of this design on military aircraft.

The T-18 made history in the early 1970s when it became the first homebuilt to be flown around the world, as well as to both the geographic and magnetic north poles. Don Taylor achieved those feats in his famous T-18, which now resides in the EAA AirVenture Museum.

After 40 years the T-18 is still one of the best handling and efficient airplanes of its era and beyond. John Thorp’s matched-hole technology and jigless construction method benefited other sheet metal designs that followed.

And for that reason, the homebuilt Thorp T-18 is a true Hallmark. 

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A T-18 completed in 1967, sans canopy, currently registered to Bernard J. Thalman, Jr., Wilmette, Illinois.	EAA Founder and then-President Paul Poberezny congratulates Don Taylor upon his successful 1977 flight around the world in his T-18. That plane is in the EAA AirVenture Museum.