Propeller hub moves north
One of the constants of the sport, experimental and microlight aircraft scene is a need for wooden propellers. At this lighter end of the scale, with not much need for constant speed units, a local industry has grown up to provide a steady market with fixed pitch propellers.
For many years Ian Henry of Christchurch was the name on the homegrown propellers, as well as on type certificated wooden units he overhauled. Then some 15 years ago Brent Thompson designed and made a propeller for his own aeroplane at Rangiora. That worked so well that others wanted one, and what started off as a minor sideline to Brent’s building and flying developed into Thompson Aeronautical Ltd.
But health concerns prompted Brent to advertise his business for sale last year, and New Zealand’s fixed pitch wooden propellers are now centred, like much of the country’s aircraft manufacturing, in the Waikato. In this case it’s the village of Kihikihi, south of Te Awamutu on SH3.
Bill Izard is well known in the general aviation community. He retired early (48) after a life running manufacturing businesses and, having watched much of New Zealand’s manufacturing disappear offshore, was “looking for something to do the Chinese can’t make”.
Wooden propellers fell neatly into that category, he thought, being largely handmade and tailored to very individual applications, not something to be churned out in their mass-produced thousands. Enjoying working with wood and with his flying and aeroplane ownership based firmly at this end of the field, he bought the business last November and moved the plant northwards.
In between was a five-week learning period. “I’m still basically an apprentice propeller maker under Brent’s guidance,” Bill admits. “He’s still designing on a casual basis and supporting me.”
During those weeks he made a dozen or so propellers with Brent. “I had to learn through osmosis and practice. Brent has a great mind and lots of experience, but he’s an absolute craftsman — and they don’t always make ideal teachers.”
Back home in Kihikihi with all the gear, Bill had made a couple of dozen propellers by Christmas. While there’s normally a waiting time of three to six months, he plans to build up a stock of 50 or so by mid-year, covering the most common types of engine/airframe combination and pitch.
The business has been renamed Omega Propellers. The Omega name was attached to a stillborn Izard LSA project not so long ago, and the picturesque family property on the edge of Kihikihi, with plenty of outbuildings, hangar and its own airstrip — strictly one-way with tall mature trees at the road end — seems the ideal place to run a gentle, one-man outfit such as making individual wooden propellers. “Cottage industry” doesn’t seem quite right with such a substantial house, but you get the picture.
“The whole thing is craftsmanship and a lot of sweat,” says Bill. “About 70 percent of the time is spent sanding.”
Even so, he has made some changes in production techniques, not surprising given his manufacturing background. Bill designed and built an 8ft long (much of aviation still uses imperial measurements) hydraulic laminating press and is experimenting with high-grade marine varnish for the final finish.
And whereas Brent designed each propeller from scratch, using first-principles trigonometry, Bill says he is “presently looking at the latest technology in prop design” with a computer program from Finland. The glues used in laminating have traditionally been resorcinol, but Bill prefers epoxy. “It’s easier to use, more forgiving and a better filler.”
There’s no need to change the timber used, as 100-plus years of aeronautical experience has long identified suitable materials — with some regional adaptation.
“It’s mostly Victorian ash and Tasmanian mahogany,” says Bill, “with some Southland beech and jarrah. Each batch of timber is tested for strength, and the grain must be straight with any knots 3mm maximum.”
The light aviation world deeply regrets Brent Thompson’s health concerns, but he can take some comfort from the knowledge that his propeller expertise and craftsmanship have been passed on — even if a short Kihikihi airstrip seems a world away from Rangiora aerodrome.
- Report and photographs by John King.
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