Pietenpol CG and gear welding


On day two of Earl Brown’s visit to my shop we worked on his Pietenpol gear legs. Earl is using split axle gear, laced wire wheels, and disc brakes. The pictures below show some of the stuff Earl, Vern and myself worked on today.


How do you know where to place the axle in the plane? Follow the 1933 plans? Think again, pre-war Piets didn’t have brakes, and if you try the 1933 gear location of the axle 10″ behind the leading edge, you can be the next guy to put one of these planes on its back. People make that mistake all the time. Why? I have no idea, because from 2010-2012 Myself and Ryan Mueller did an enormous project measuring W&B data from 40 different Piets, developed a mathematical formula to calculate the heaviest pilot who could fly any Piet, and then wrote a series of very clear, concise articles on the information. Problem solved? Not at all, almost no one outside Corvair builders used the data, and they went merrily ahead believing old wives tales and building planes with aft CGs and the tendency to go on their nose.


Fortunately Earl is a smart cookie, and in a few minutes we placed the location of his Axle 11.6″ behind the firewall, about 1″ behind the leading edge of the wing, and set up this way his plane will not go out of the aft CG limit unit the pilot weighs more than 280 pounds. Five minutes of paper work vs years of building wondering if you will have to move the wing or build new landing gear legs…..or both. Your choice, but Earl is a low stress guy, so he chose 5 minutes of looking at the old articles we wrote long ago.



Above, a page from the 2012 BPAN newsletter, where all the CG articles were published. These are still available. The is no rational reason to ignore the existence of this painstakingly gathered data, but many builders do. I wrote the articles myself, they cover all popular engines for Piets, and they are presented very simply. It is not required to be a math wonder to use the data, there are many examples of each engine to follow.


When I presented this data at Brodhead, a man actually told me that I was “ruining Pietenpols” because they are for people who “Like to fly low and slow, and not think too much.” I pointed out that he was literally advocating running out of Altitude, Airspeed and Ideas at the same time.  Some people you just can’t reach.



Earl made a wood fixture which took the place of the bottom of his fuselage. It also located the axles. Pietenpols have a flat steel tension strap connecting the fittings on each side of the plane.  In the foreground are the the completed die spring assemblies.



Above, a look at the front fittings, and the beginning of the landing gear leg. $130 steel parts were made by Earl, and Vern welded them with my Tig welder.



Above, the rear attach fittings, these wrap around the sides, and are also the lift strut attach points.



Above, Vern stops for “dinner.” It’s Herring out of a can. To make the shop smell better I had to burn more of Earls particle board fixture with the welder. It didn’t really cover the scent, so I may have to empty the contents of several cat litter pans into the shop just to freshen things up. Vern’s jacket celebrates the Bonneville Salt flats. He hand painted the image and the lettering on the jacket one day when he was bored, about 10 years ago.




About William Wynne
I have been continuously building, testing and flying Corvair engines since 1989. Information, parts and components that we developed and tested are now flying on several hundred Corvair powered aircraft. I earned a Bachelor of Science in Professional Aeronautics and an A&P license from Embry-Riddle Aeronautical University, and have a proven 20 year track record of effectively teaching homebuilders how to create and fly their own Corvair powered planes. Much of this is chronicled at www.FlyCorvair.com and in more than 50 magazine articles.

8 Responses to Pietenpol CG and gear welding

  1. Howard Horner says:

    Were that my plane I would have to mount little mirrors so passersby could see the beautiful weldments. Holy cow!!

  2. Dan Branstrom says:


    I guess you just don’t like herring. I grew up with it, being of Swedish descent. Herring is eaten all over the areas surrounding the Baltic Sea. I’ve had herring pickled, as well as canned in vegetable oil, and I occasionally like to have some.

    Just be glad that Vern wasn’t eating Surströmming, a lightly-salted fermented Baltic Sea herring that is fermented for at least six months, “the Swedish delicacy, that is widely considered to be the smelliest food in the world.” I’ve never eaten it, and don’t care to, but one description of the smell is Limburger squared.

    The story, told to me by a Swede, is that a Swedish couple were staying at a hotel in Germany, and had a can of Surströmming with them. They went out on the patio and opened it up. Soon, there was a knock on the door, and they ended up being cited for air pollution.

    That is, indeed, beautiful welding.

  3. Dennis McGuire says:

    Wow, looks like these fitting are built for a tank. Wonder if they could be built with thinner steel to make them lighter.

    • Howard Horner says:

      I am not an engineer, not very experienced in aircraft building, and not even that smart, but I have to wonder if there might be a better place to save weight on an airplane than the landing gear. Respectfully, Howard

    • Dennis, two factors, the photos make them look thicker than they are, they are .125″. Second, because this is tripod gear with geometry for wire wheels, it has far more acute angles to it than gear for 6×6’s, these acute angles put far higher loads on the fittings. If you look at the picture of my ‘sculpture’ it has fittings which experienced tear out in the accident, and showed that given a great load, the bolt didn’t shear, nor did the tube fail at the end, the failure point was tearing out from flat fittings. Not that you design for accidents, but it shows that perhaps the tube or bolt is overdoing it more than the fitting.

  4. Lou Casella says:

    Those welds are absolutely beautiful. I hope to be able to weld that well in the future.

  5. mark says:

    It beggars belief that brain dead people can be live (zombies?)let alone fly. Lovely welding by the way

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