What goes around

Not all propellers are the same. Different size engines require different types of propellers. For ultralight aircraft, propellers need to be small and lightweight. Culver Props in Rolla, Missouri, is a family-owned business that serves the experimental and ultralight communities as well as the more rarefied world of World War I and Golden Age aircraft replicas with custom-built wooden propellers. Each propeller is created via patterns, traditions, and equipment refined and handed down over decades. The result is not just a functional part of an airplane—it’s a masterpiece.

Out of the way

Alaina Lewis gives out the address of Culver Props and advises, “You will think you are lost but just keep going.” Rolla calls itself “the middle of everywhere” thanks to its location halfway between Kansas City and Springfield, but once you jump off Interstate 44 it’s another story. Follow the county road that winds through watersheds and notice the flood warning signs on the narrow bridges. Turn off that road, pass two farms, and the shop is at the end of the lane. If you are greeted by a pack of friendly dogs or you see an aluminum ultralight airframe parked in front of the shop, you’re at the right place.

Each propeller is created via patterns, traditions, and equipment refined and handed down over decades.The rich aroma of mahogany will hit you before you spy the woodstove; racks of propeller patterns; stacks of wood; and orders in various stages of completion. One of these is a propeller that belonged to John K. Moody, known as the father of ultralight aviation and the first person to develop a powered hang glider that could be launched from flat terrain, without benefit of wind. When this propeller is rehabilitated, it will grace an Easy Riser—the same type of swept-wing biplane hang glider that Moody looped at an Experimental Aircraft Association airshow in the 1980s.

A Culver Props customer is either having a great day—because they’re designing or perhaps picking up a propeller to start a new project—or a bad day, because they broke their propeller and are hoping Lewis can fix it.

Provide your measurements—bolt pattern, bolt size, rotation of the propeller, center pilot hole diameter, and the desired cruise rpm and miles per hour desired—and Lewis or her brother, Grant Smith, will turn those dry numbers into an elegant prop. You might even get to see your propeller being made on her Instagram account.

It starts with the wood

The process starts with perfect pieces of wood, shipped from Kansas City on an 18-wheeler too big to navigate the county road, let alone the farm lane (the wood is offloaded to Lewis’s truck at a gas station on the interstate). Lewis uses primarily hard white maple, which she says is incredibly strong and not as heavy as oak or walnut. Some of the propellers-to-be are mahogany, which is also strong and has the added benefit of providing an authentic look for World War I replica aircraft. Maple and mahogany have a tight grain that stands up to the torque forces of a full-power takeoff.

Lewis inspects each piece of wood, looking for defects such as cracks, knots, or unsightly grains, or a dense spot in the wood that would likely throw its balance off. She selects a pattern that will be used to cut out as many layers of the wood as the propeller requires.

Culver Props has approximately 300 patterns dating back decades—they are stored in an entire wing of the shop’s second floor. Lewis wants to preserve them. “There’s less and less of them. I want to keep that period of aviation alive so people can appreciate what we have now...If you look at a triplane and then look at a jet, [aircraft designers] started with that triplane. Those are what started [aviation].”

The boards are glued together and placed in a press for 14 hours at 70 degrees Fahrenheit and at 60 to 90 PSI depending on the propeller size. When the glue is dry, Lewis drills the center pilot hole in the glued-up blank, and sets up the lathe with the pattern and the blank to carve out the propeller shape and drills the center pilot hole. Once in the lathe, the wood rotates hypnotically along its axis while she uses a very sharp saw to perform a symmetrical cut—a sort of rough draft of how the propeller blades will look. She sets the propeller pitch, then performs a final cut of the blades.

The massive lathe is a star attraction of Culver Props’ social media videos. It can accommodate propellers up to 102 inches in length. Lewis says she would like to get an even bigger lathe so that she can produce 110-inch propellers for World War I replica aircraft.

Sanding and balancing

From there, Lewis will cut out the hub and use a hand sander on the hub and the propeller blades. Sanding the blades can take from four to eight hours. “Then it’s a matter of sanding and balancing, sanding and balancing, until they’re perfectly balanced vertically and horizontally,” Lewis says.

The propeller is stamped with a serial number, pitch, and diameter, and the bolt pattern is drilled into the hub.

The propeller receives two coats of a custom-blended antimicrobial/antifungal sealer with UV protection, then two topcoats. The final coat, she says, “is something similar to what you’d put on counter tops.” The propeller will then need to cure for 10 days. The final touch is a Culver Props sticker.

At any point in the process, Lewis can decide that the project is not going to be up to her standards. It will not be an airworthy propeller, but it might be sold for decorative purposes. Then she’s back to the wood pile to choose another contender.

Propellers are priced according to their size and the type of engine they’ll fly with. At the lower end of the scale are 48- to 54-inch propellers intended for Volkswagon or Jabiru engines, starting at $575. On the other end of the spectrum are 84-inch propellers for seven-cylinder Verner engines, starting at $2,650. Custom staining, leading edge tape, and tip paint will cost extra. Want a mix of mahogany and maple, or an all-maple propeller? Lewis can do that, but it will cost extra as well.

Ultralight roots

Lewis and her parents and grandparents have owned Culver Props since 2001. “It was basically a way to keep Grandpa active in his old age,” Lewis says of her grandfather, Gene Smith. He was a farmer, crop duster, and pilot with airframe and powerplant certificates who also designed and sold his own ultralight, the Back Yard Flyer, via a separate company called Valley Engineering. Lewis said her grandfather, who graduated college with a degree in engineering, was kind of a “mad scientist, but in a good way, in a fun way”—constantly refining his own designs. He created 12 different aircraft designs as well as different versions of the Back Yard Flyer before his death in 2016.

“He was always five to 10 years into the future,” she says. A 2003 video shows Gene Smith displaying a Back Yard Flyer with wings that could be rotated 90 degrees so that the airplane could be loaded into a box trailer; an electric starter; and a 72-inch-diameter propeller flying in front of a 40-horsepower four-stroke engine. Valley Engineering was shuttered and no longer sells ultralights, but Culver Props offers online support for Back Yard Flyer owners.

The Smiths moved the propeller business from Pennsylvania to their home in Missouri. Grandfather Gene and grandmother Juanita Smith built the propellers and sold ultralights along with son Larry Smith, who divided his time between operating a gravel company and the family’s aviation pursuits. Larry’s wife, Verla, takes care of the accounting in addition to running three small businesses in Rolla.

Larry and Verla’s daughter Alaina grew up around ultralights and began helping out in the propeller shop while in high school—taking out trash, cleaning up, even providing her grandfather with an extra set of hands when carpal tunnel syndrome wouldn’t permit him to wrench.

When Lewis officially joined the family business, “I made tons and tons of unairworthy props before they would let me make an airworthy one,” she says.

Her brother Grant Smith helps with propeller production. Together, the sister and brother can make 175 propellers a year.

Grant’s wife, Hillary, is a photographer who manages the company’s popular social media accounts. Their dad is always available to help with fixing propeller pitch, choosing a pattern, or anything else. Lewis’s husband, James, drills bolt patterns in addition to his “real job" as a cement plant manager.

Grandmother Juanita, now in her 80s, is retired. Whereas she once was busy with packing propellers and covering airplanes for the family’s ultralight side gig, she is content to come to the shop and sweep when she’s needed.

A dream come true

Although she is working on her private pilot certificate in a Piper Cherokee, Lewis’ affection for smaller, lighter aircraft will never wane. If you should meet Lewis or any of her family at EAA AirVenture, you’ll likely find them in the Ultralight section, where they’ve hung out since they began attending the show in the 1990s. They exhibit at the show, and likely have many examples of their handiwork parked by the grass runway of the Fun Fly Zone at Oshkosh.

You can also see Lewis’s handiwork flying on an Albatros D.Va reproduction at Old Rhinebeck Aerodrome in Red Hook, New York. She created the pattern for the project. “It looks perfect on their airplane,” she says.

“My dream was to make a prop for Old Rhinebeck,” she said. “It doesn’t get any better.”

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