Testing at Sensenich Propellers

Builders,

Yesterday, Dan Weseman, Paul Salter and myself drove 150 miles south with the Panther prototype to Sensenich Propellers. The task was to have their engineering staff test the combination of their Composite ground adjustable prop blades on the most powerful Corvair, Dan’s 3.3 liter stroker engine. It was a productive and interesting day. Dan had long planned this, and we wanted to squeeze it in before the end of the year. Sensenich has designed a specific prop for The Panther, but the testing paves the way for existing Composite props to be used on Corvairs. We have used Sensenich wood and wood/composite fixed pitch props on Corvairs dating back to 2003, and we extensively tested them on Zeniths, KRs, Pietenpols and even our Wagabond had one. But Yesterdays efforts were directed at Sensenich’s hollow, molded composite blades, recognized for their outstanding performance and their ability to be used in ground adjustable and constant speed hubs like the Airmaster.

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Above, Dan in the panther, while an engineer logs the data. it isn’t like a simple prop balance, this information is vastly more complex, and will require many hours of analysis.

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Above, Paul standing with one of Sensenich’s air boat blades. It is hollow composite. Three of these will effectively work on a 380hp GSIO-540. Half of their business is airboats, and they have a lot of work from it. The factory is highly automated with all types of CNC equipment, but still employs 30 craftsmen. A tour through their facility is a very effective demonstration that much of the “Conventional wisdom” spread on the internet and in hangar flying sessions is BS, modern props are doing many things ‘internet experts’ say will never happen. So much for props that are tapered to eliptical toothpicks at the tips.

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Above, to be said with a Marlin Brando accent: ” I cudda been a propella” . This is a 10 yard dumpster filled with cut offs and scraps of yellow birch, sourced from the US, mostly in New York state. It is a fairly dense wood, and what most of their fixed pitch wood props are made of. Sensenich is an actual FAA certified aircraft prop manufacturer, whos products have to meet certified standards. This isn’t a nice guy with a draw knife and a cult following, it is real American manufacturing.

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Above, The office had a super cool cut away of a Sensenich skyblade adjustable prop from the 1940s. This is not an Aeromatic, notice the diaphragm at the top. This was designed for certified aircraft.

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Above, a series of intricate strain gauges attached to the blade root, the highest stressed part of the blades. The connections were soldered to wires leading to a radio transmitter in the prop hub, so the data they read was transmitted wirelessly to the computers on the bench. If you look at the first photo, you can see the receiving antenna attached to the blue bucket in front of the plane.

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Above, opposite blade, with it’s strain gauges installed on the node lines of the blades. This is looking for resonant frequency data. The node lines were previously established on a shaker table inside. The silver writing is upside down here but it shows the fist second and third lines. These blades are incredibly stiff, and these frequencies are very high, well outside the rpm range of the prop. The testing went all the way to 3600 rpm in 50 rpm increments.

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Something funny: Earlier in the year, a guy was telling a few people that he had some combination of a Chinese crank and a bearing that would be the only way to put a complex prop on a Corvair, and the Weseman made inUSA billet crank and Gen II 5th bearing was not up for it. Here’s the joke: The cost of yesterdays run of testing on Dan’s products, and the development of parts is covered by Sensenich.  These blades are already in New Zealand at the Airmaster factory in a test prop specifically designed for Dan’s 5th bearing and our prop hub. Real propeller companies with staffs of actual engineers who have spent their entire careers looking at these specific issues, working on the combination, Yet one idiot with a keyboard and access to a discussion group can claim that he and his Chinese crank are the ‘solution’.

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