Corvair / Buttercup – Dan Palmer


This is a 2014 photo sent to me by Dan Palmer, the first person to build and fly a Corvair Powered Wittman/Luce Buttercup.  This airframe is one of the all-time great homebuilt designs, from the mind of one of the greatest aviators of all time Steve Wittman.


Two lessons here:


If you think that you are too old to build a plane because AARP sends you junk mail, know this: Dan Plamer’s EAA membership number is 3065. Thats right, only four digits. I joined 29 years ago and my number is 331,351.  This guy is serious ‘old school’, he could have voted for Harry Truman. If your first election was after that, time for you to head out to the shop and get building.


Second, I included his original engine parts order in the picture. Note that it was placed and filled in 2004. Twelve more years elapsed before Dan’s engine went flying. Many planes are a personal lifetime goal, and the builders are not competing with anyone. They may be on a budget, have family obligations, or just approaching each task with a goal of mastery. 2004 was my 15th year in the engine business. Nearly every single engine company from that period is gone. Engine companies that have short life spans don’t serve traditional old school builders. Working with Corvairs since 1989, I am here for the long run. Read: What defines ‘reputable’ in our industry?



Above, Dan’s creation in New Mexico. The Corvair and the Buttercup are a natural match. Wittman’s original was powered with a number of different engines, but he intentionally stuck with a high reving C-85 installation.


Today, I find it ironic for anyone to claim to admire Wittman’s designs, but not like auto engines. He was one of the greatest advocates of alternative engines and high rpm direct drive props ever.  I know what I’m speaking of, read this: From The Past: With Steve Wittman 20 years ago today. Wittman’s Oldsmobile V-8 powered Tailwind flew us on a 62″ metal prop turning 3,600 rpm at 195mph. It was no slouch.  His VW powered V-Witt design was the perennial Formula-V national champion.


It is not a myth that Wittman flew his planes at wide open throttle as a cruise setting, and he liked 500AGL as a cross country altitude. With the props he liked, this meant the original C-85 Buttercup going 145mph with the engine at 3,400 rpm. That is 825 rpm above the C-85s published redline. At 3,400 the C-85 probably made 110-115hp.


Wittman derided anyone who put a 150-160hp Lycoming in his designs and then throttled back to 115hp for cruise. He may look grandfatherly in pictures, but in person he had a sharp tonge for people who believed old wives tales about slow turning props.  Wittman understood that with the right prop, the 3,400rpm Continental was virtually as efficient and powerful as a throttled back Lycoming, but it was 100 pounds lighter and  less expensive. Everything I have said about the efficiency of Corvair engines with reduced diameter props is taken straight from the Steve Wittman playbook. When you encounter someone making a statement about smaller props not being efficient, recognize they are calling Steve Wittman, the greatest air racer that ever lived, an idiot or a liar.



4 Replies to “Corvair / Buttercup – Dan Palmer”

  1. This hit home with me. Working with small hp engines for ultralights and going direct drive with them. I have noticed a lot of people who think its better to swing a large prop. In doing so the small engine cannot meet its design hp.
    I don’t understand why anyone would want to leave hp unused in an engine for the sake of turning a larger prop.

    If your only working with a 15 hp engine to start with and prop it so it your 20% under rpm your loosing 3 hp.

    This does not seem like much but may be the difference between flying or running and engine and simply overheating it without it making its max potential.

    Think about it a bigger prop may not always be better!

    Tim Shupert
    Eau Claire, wi.

    1. Bigger prop is tantamount to running a car or bike in a higher gear when it should be in a lower. Per revolution, small prop moves less air/less load, but higher rpm moves equivalent air and more than big prop while engine, albeit turning higher revs, is not ‘feeling’ loaded. Agreeing totally with the theme here, just translating for the guy that lives in my head…

  2. Steve Wittman gained much of his knowledge of aviation design in the toughest, most competitive venue possible: racing. He beat many, better financed, more powerful airplanes by his designs that included lightness, more efficient aerodynamics, and reliability. There’s good reason he has the Oshkosh airport named after him.

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