From Models to Military Drones, Don Srull Has Built Them All

The hobby that launched a career.

Don Srull has built hundreds of airplane models, including the PWS-10, a 1930s-era fighter flown by the Polish air force. (Pat Daily)
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Donald W. Srull, a longtime designer of model-airplane plans published in modeler magazines, talks about the hobby that launched his career as an aerospace engineer building unmanned air vehicles for military surveillance.

Air & Space: Describe your first experience building and flying a model aircraft.

Srull: My first attempt at model building was with a 10-cent kit from Comet, an early model company. It was a Curtiss Robin, a favorite because it was featured in a movie I saw. After a long struggle, it was finally finished, and to my eyes looked beautiful. When tossed vigorously, it could travel six or seven feet. Building models soon became a neighborhood ritual: Three or four of us would get together on a front porch and build models while listening to airplane adventure programs on the radio.

What are the secrets to designing plans for models that don’t just look good but actually fly well?

I can honestly say I am still looking for the secrets of successful model design. To increase the chances that your model will fly well, keep the model structure as light as possible. That leads to the most basic design trade-offs to be made: strength versus weight, a fundamental design challenge for all aircraft. For scale models, part of this trade-off requires decisions about how much scale detail to add.

What are some of the aircraft you have designed plans for?

My model designs include the Santos-Dumont 14-bis and the 1911 and 1913 Voisin Canard biplanes. Delta wings also appealed to me, such as the World War II Lippisch P.13. The majority of model designs, however, were versions of more conventional civilian aircraft, such as Cessnas, Wacos, Pipers and the like, plus a number of World War II aircraft.

What kind of feedback have you received from people who’ve built your model designs?

The response to model articles I’ve published has been gratifying—and unexpected. I received a surprisingly large number of letters—before the Web—from contemporary active modelers, old-time former modelers, and even non-modelers.  Virtually all comments were friendly and complimentary. And very often photos—proud photos of the writer’s rendition of my design. I cannot imagine a greater compliment. Many of these photos are still pinned to my workshop wall. A touching letter came from a young boy interned in a reform school. He had no modeling background, but was moved by a model airplane article from his reading library. He asked for advice and help in getting materials to build one. We corresponded for a time—I hope it helped get him on track.

Has electric-powered propulsion for model aircraft been a game changer?

Electric power has certainly been a game changer. Electric revolution might be more accurate. Electric power now dominates most forms of model and small-drone activity, and is just beginning to move into full-scale aircraft. It has made this jump in a remarkably short time, and its growth is accelerating.

Do you think hobby drones should be more tightly regulated?

The proposed flight area restrictions for hobby drones, such as a maximum altitude of 400 feet, and minimum distances from airports are modeled after current Academy of Model Aeronautics regulation and seem to be a reasonable start. The maximum weight limits for hobby drones, however, appear quite high to some and deserve further attention. As the density of small drones continues to grow, I believe that some kind of certification of basic flying skills and knowledge of safety regulations for any hobbyist flying a high-performance drone—perhaps administered by local model clubs—may be useful. A minimum age should also be considered. Difficult decisions, but after all, everyone requires a driver’s license to drive a car on our highways. Perhaps high-performance drone pilots should also be held to some minimum level of competence. The vast majority of drone operators, both hobby and professional, are dedicated, safety-conscious fliers. For that reason, I’m optimistic we can move along somehow.

Of the many models you’ve built and flown, do you have one or two favorites?

It’s a hard choice, but my most memorable model experience was the Dornier Do-X. In 1988, when electric models were beginning to break out, electrics offered a new opportunity for multi-engine models. It was possible—but very difficult and risky—to use other motor types. Electric motors were much more reliable and consistent performers, so they were ideal for this use. A few twin-motor scale models worked well for me, so I decided to go the limit and build an old favorite—the Dornier Do-X, a 12-engine giant flying boat, built in 1929. To be honest, expectations for the model were not all that high, but the real Do-X had a fascinating history, and I liked its looks. To everyone’s surprise, the 42-inch free-flight model flew remarkably well on its first day out. It has had a charmed life. Even with homemade motors and early nickel-cadmium batteries, I flew it without serious damage for years and hundreds of flights. Eventually, I replaced the motors and batteries and added a small RC system. I still fly it occasionally today.

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