Save $59, loose $1,000, repeat for fun….


Yesterday was a very quiet and peaceful day around our airport. People here are very friendly and gregarious, but on Thanksgiving, they tend to focus on family and home, and yesterday there was no one out and around. Grace and the dog drove over to her parents for a few days, but I elected to stay here and enjoy the quiet while getting some things done on our own aircraft, It was perfect blue skies and slightly cool. At sunset I went out flying, climbed to a few thousand feet and just puttered around at 1,800 rpm and just watched the sun sink. When it was gone and the runway lights came on, I pulled the power off completely and glided all the way back in comparative silence. I landed and rolled directly to our front yard.

About 10 pm I realized that I had not spoken to a single person face to face all day long. The only people I had spoken with were on the phone. I had covered about a dozen calls during the day. In the morning parents and siblings, a number of friends in the afternoon, people we know from Corvairs, but the conversations weren’t on technical things.

Mixed in this came a call from a guy who refused to give me his name beyond “Jerry.” He was a bit rude saying that he wanted information about a Corvair flight engine he had bought, but it wasn’t anything I had built. He started off with a sarcastic tone about “wow a real person on the phone.” When I am answering the shop line on Thanksgiving day my tolerance for having him complain that I didn’t return two of his previous calls is low. (If you call and will not leave your name and you need help with an engine I didn’t make, you are not a priority call to return) His story goes like this: He didn’t buy a manual from me because they are $59. Instead he bought an engine for more than $1,000. He tells me that it has the drive end of it opposite the way we do it, that his engine has a gear box on it,but he has no idea if the gearbox is spur or planetary, but he is absolutely sure it is made of aluminum. He wants to build an airframe for this engine he bought.

In a few questions I can tell he hasn’t read much about Corvairs. The thing that is annoying to me is that this doesn’t stop him from saying thing with a tone of being knowledgeable. Without seeing a single picture, I tell him he is wrong about the drive end, we have always put the power out through the flywheel end. Second, he is also wrong his gear box,  a Rinker cast iron unit, undoubtably a 1.39 ratio. Since he says the engine was built 20 years ago, it isn’t going to have anything good inside,( and it stands a very high chance of being a 145 cid early engine.) This guy states that it’s an aircraft conversion because it has valve covers that say “otto” on them, but I tell him that they are just car parts from the 1970s in CA. He looks at pictures and listens to my descriptions and concedes that most of the things he said and thought about the engine were wrong. He is slowly coming to the conclusions that 1) I know something about Corvairs. 2) he doesn’t have a good engine. 3) maybe information is power, and $59 wasn’t a big rip off compared to a grand for a boat anchor.

He cheers up a little when he thinks that he might at least have an expensive core engine. I point out that it likely isn’t a 164 cid engine, and even if it was, the Rinker is mounted to the crank by broaching a key way right where we thread the safety shaft, so he doesn’t even have a core engine. He asked what he could do with it, I suggested selling it to an air boat guy. He then told me that the engine is in Idaho, not real close to the LA or FL swamps.

I am not writing this to complain about anonymous people who don’t like buying manuals but do feel entitled to complain about return phone calls. Neither am I motivated to cite another example of a person who’s only interest in Corvairs was that the thought they were cheap and he had a bargain in hand. The reason for the post is far more direct and simple: Experience has shown me that when I tell a guy who just lost a thousand dollars that what he has isn’t good, there is about a 75% chance that the specific engine will be for sale in the next 60 days on Ebay or Barnstormers for at least the same amount of money he paid. Writing this isn’t going to prevent that cycle, and there is always another guy out there to buy it. No, I write this just so when the next owner surfaces of a discussion group saying he just got a ‘cheap engine’ for his plane, perhaps one of you guys can send him a link to this story. And you know what the new guy is going to do when he finds out his engine is useless junk? Well in 60 days it…………

A question of Carb location…..


We got a letter from builder “PJ” who asked this about carb location:

“All the Fly-Corvair designs have the carb slung under the engine while the evil Rotax has two on top as the Corvair motor had in its automotive configuration. Is there a good argument for leaving the intakes unmodified and having the carbs top-side? How was it done in the early Pietenpol models?”

PJ, I have photos of about 350 Corvair powered aircraft that have been built in the last 53 years. Of these only two or three had  2 carbs mounted on the stock intake flanges. I am going to say that none of these aircraft were even marginally successful.  Two of these aircraft had stock Corvair Rochester 1 barrel carbs and the other had a pair of Bing carbs.

To cover part of your question, Bernard Pietenpol always used carbs below the engine. In my workshop, carefully protected, is a Ford tractor carb. I treasure this because it was actually BHP’s own carb from an early Corvair conversion. (The carb was a gift from the Mensink brothers.) This carb was mounted on a manifold just like ours, but bolted up to the stock intake flanges on the heads. If you look at the very last page of your conversion manual, it has a picture of BHP standing next to the very first Corvair powered plane, a J-3 airframe. It has this same type of set up.

Why is the carb below? For one overwhelming reason: Because the plane can use gravity feed as a fuel system. Virtually every single classic light aircraft was set up this way. It is r-e-l-i-a-b-l-e. Compare gravity feed vs pumps that would be required by carb on the top: Carbs on the top are 2 times the carbs, you need a regular fuel pup, and of course a back up. then you need a fuel pressure gauge to tell you how the pumps are. you need a pump switch, and each pump needs it own breaker or fuse, and this all needs to be connected by wire, and you need to give some thought to better lines and AN connections because it all going to be under pressure. Now, does that sound simpler than having one carb under the engine? BTW, I have dyno tested the same engine with stock carbs, back to back vs a Stromberg from a 65 hp Continental, and below 3,600 rpm they had the same power output.

Issue#2 is aerodynamics. The stock carbs sit up 6.5″ above the intake log. The GM designed minimum height air cleaner used in vans and wagons adds a full 2″ to this height. A cowl that these carbs fit in would be big enough to house the 505 cid OX-5 V-8 in the previous story. I have seen picture of two Piets with stock carbs set up this way, and I am basically going to say that the people who pursued this needed to have a “mechanical intervention” where their friends showed up and all at once said to them “we love you, please just stop, we will find you help.”

The only person that actually tried to fly two bing carbs on the top of a Corvair was a builder of a “Lite Star” A design that looks like a kitfox from the very respected Canadian designer Morgan Williams. I know Morgan, and he was not fond of this guy, “Pavel” a recient immigrant to Canada from the Czech Republic. As predicted, the plane, which could have used gravity feed, instead a very complex set up and a cowling that looked like a shipping crate. It was a very poor performer. Last I heard from Pavel, (2007) he was in Vancouver and trying to start a business building Corvairs. I reminded him that his signature on the product rights agreement said he wasn’t going to do this, but his attitude was that his word was meaningless, and I couldn’t do anything if he stayed in Canada. My condolences to my friends in the frozen north who are hosting this guy. I really doubt my Great Grand parents had the same attitudes towards their new home land when the came through Castle Garden immigration station in the 1870s.

I particularly don’t like Bing carbs. People generally understand that Rotax as a company doesn’t place much emphasis on mechanical longevity, low parts count, simplicity nor field maintainability. Now, if you are going to look at using a carb off another engine, why choose the one that comes from a company that has values that are the polar opposite of things we are working for in the Corvair movement? There are vastly better motorcycle carbs than a Bing. Rotax just uses them because Rotaxes are from Austria and so are Bings. A few months ago I wrote a story about a guy who insisted on using a Bing on a brand new 3,000 cc engine. It leaned out and wasted the engine on flight#1. At the end of the photos I include a 1997 story about the joy of flying Bing carbs. It should change any ones mind, with the exception of a guy in Vancouver.

Above, I stand with Chris Heintz in the Zenith booth, sun n fun 2004. Our 601XL in the background. Look at how close the intake tube that is visible comes to the cowl. It is only 2″ above the log. You can’t put a Bing carb on an engine and put a cowl on it that is vaguely aerodynamic. They fit on the top of Rotax 912s because the Gear box makes the thrust line much higher than the crank on a 912. No one ever accused the typical 912 of having a really slick cowling.

For all the relentless talk of “PSRUs” (gearboxes and belt drives) I endured in the 1990s, few people mentioned that many PSRU engines had cowlings that looked like bath tubs. If you move the thrust line down on a plane to clear the carbs, your making something ugly with poor prop clearance, and poor motor mount geometry, not to mention your messing with the aerodynamics of the plane, without testing. All this, just to have two of the worlds poorest motor cycle carbs. Don’t even get me started about the fact that Bings are under pressure but don’t have threaded fittings on the fuel lines……

Above, Louis Kantors 601XL engine installation, built in my hangar in 2009. This is another view of how close the intake pipes are to the smooth cowling lines on a Zenith. We use the same intake on all Corvair powered planes with the exception of the Cleanex and the Panther (Dan sells those, they look nearly identical to ours but are different on the bottom to fit those airframes.) Note that this aircraft has a 45 amp tea cup ND alternator on it. I built a number of these as a test, they work, but there is no call for them. Notice that it displaces the oil cooler and makes the plumbing more complex. Today we are looking at direct drive rear alternators, a more promising idea that leaves the oil cooler in the standard location.

Above, three aircraft with carbs below the engine parked in our front yard. L to R, Louis’s 601XL – MA3-spa, Grace’s Taylorcraft – Stromberg, and Dan Weseman’s Cleanex-MA3-spa. The 601/650 is one of the few Corvair powered airframes that uses fuel pumps, almost all others are gravity feed. You might not guess this at first glance, but the Cleanex has no fuel pumps, it is only gravity feed, but it worked great, even during aerobatics. Do not accept complexity without good reason. The 601/650 have the fuel in the wings, which is a good trade-off for complexity. High wing planes can also have the fuel in the wings, but they don’t need pumps.

Above is Randy Bush’s 400+ hour Pietenpol at Brodhead.  Note the intake pipes. It should be obvious that this plane would have a very blocky cowl with carbs on top. Note that this aircraft has a stock thrust line, about 3″ below the top longeron. There is even less space for carbs on top when we make the high thrust line mounts. Thats ok because the high thrust line gives more room under the engine for the carb, where it should be.

Above, the last original with a stock thrust line. Note the tiny bulges in the cowl to clear the intake tubes on the manifold that connect the carb under the engine to the stock flanges on the heads. Again, no space on this installation for carbs on top, and no reason to have that kind of complexity on a plane that can have simple gravity feed.

Most of the people who are looking at a carb on top of the engine are driven buy one of two things: they either want to find a ‘cheap’ carb or they don’t think I know what I am talking about when I say having a low carb doesn’t affect power output. I find the concept that a guy who has tested neither assumes that his guess is more valid that my 20 years of testing pretty annoying. On the subject of low-cost, it isn’t a stretch to say that I know more people building a Corvair engine for a  plane than any other person on Earth. While cost may be an initial attraction, the reason why people stick with it is to learn something, be proud of what they  have done, and experience this in the company of other like-minded aviators. In  the last 20 years, these people have largely been the ones who succeeded. I have  good reason to state that the ones looking for something ‘cheap’ were the first  ones to quit. Every unexpected penny eroded their reason for building.  Conversely, those who where here to learn build and share, viewed a lot of the  money they spent as an investment in themselves. If you want to fly cheap, rent  a Cessna 150. If you want to do something rewarding, fly something you built  with your own hands.

Above, a 1 barrel down draft ford carb. If you would like to read more on our testing of this, use the search box at the top of the page to find my story “in search of..the economical carb.” 

When I was little, I wanted to be Jacques Cousteau. It hasn’t worked out that way.  Sad but true, the lasting portion of my working life boils down to what I have done with the Corvair. In reality, I am neither overly proud of it nor ashamed of it, just OK with it. This said, none of my work is to show cheap people what they can get  away with. My work is to show people willing to make a serious investment of  themselves (mostly time), that there are great rewards awaiting the individual  who perseveres on his own terms. In 30 years I will likely be dead and  forgotten. Between now and then I plan on spending as much of my time as  possible in the company on people who want to learn build, fly and have a good  time. If I ever seem short with some ideas, it is because my experience allows me to see something that many people miss: This vital finite resource isn’t money, it’s time.

Not in the free time sense, but in the years left sense. If you’re not young, nor a millionaire, then you have to make your shot count, you’re not going to get a do-over on this. Let my experience work to your advantage. Build as simple as a plane as you can, work on it every day you can, and understand that some components on it, like the carb, are going to cost money. There is a combination of simplicity/effort/money that can get a great number of people flying. You can be one of them, and the odds that you will be go up dramatically if you use my experience to avoid every mistake I made and paid for.

A personal example of why I don’t like Bing carbs; Steve Rahm, our neighbor at Spruce Creek, designed and built the ‘Vision’. It had a Stratus EA-81  Subaru with two Bings on it. Since they basically ran full time carb heat,  he wanted to try cool ram air in search of more power. He went as far as testing the set up with a gas leaf blower on the ground. He did this because some people said Bings don’t like ram air. On take off it worked great, until the plane hit 70mph over the trees at Spruce Creek. Then the carbs  shut off all by themselves. Plane slowed to 65, power comes back a little. Very  skilled flight at tree top level is executed. Several minutes of listening to  the rough engine clawing its way around the pattern.

He appears on final gliding  in. Steve was a new dad, and his own father had been killed in a plane when  Steve was a young man. I could not believe that I was about to witness a  horrific repeat of a family tragedy. He barely made it, touching down at 75  mph. People on hand thank God aloud. as the plane rolls out in the three point  attitude, the airspeed drops below 60, engine comes back to full power and tries  to take off on its own. Steve later tells me he almost had a heart attack at that  moment. He switches to a Lycoming with an MA3-SPA. which operates on the stone  age concept of the throttle opening and
closing when the pilot wants. (the throttle on a bing is controlled by a vacuum diaphragm) Steve is a  master skydive instructor with
4,000 jumps, he can keep his cool under pressure.  I figure most other pilots in a plane with a five mile per hour  wide speed envelope and 100′ altitude would have bought the farm. -ww

Mail Sack, Thanksgiving.


Here are some letters on various topics. On the subject of Machine vs appliance, USAF (F-4)/ATP, 601XL builder Bob Pustell writes:

“I like your comments about machines verses appliances. I have spent several weeks reinstalling my overhauled 65 year old Franklin engine into my 65 year old Stinson airplane. Both are marvelous machines. Both are good for another 65 years. I could have done the installation more rapidly (or hired someone to do it) but part of the charm is doing the work, making the wire runs look orderly, getting the push-pull cables rigged just so, etc etc. The only down side to this infatuation is that the effort required to keep a two thirds of a century old airplane airworthy cuts deeply into my building time. I am enjoying myself.-Bob “

Zenith 650 Builder and CC#22 grad Brian Manlove writes:

 “William – and even “appliances” are not immune to the habitual machine lover… as can attest the numerous “gone forever” toasters, fans, and other consumer stuff that cannot escape the hand of the person who hates waste. Count me in for April – that will hopefully be my run-time. Thanks.”

Builder Don January writes:

“doing a great job, hope to fly soon corvair is done working on panel”

Builder Tom Griesemer sr. Writes:

“Absolutely!!! I want to be the first to sign up as Leesburg is only 75 miles from my home. I have only just started my engine (which you helped me find) but would like to bring it. I will be there. Thanks William.-Tom G.”

Sprint builder Joe Goldman writes:

Where my Sprint currently lives, Roy Hall , the owner of the place has a good crank and other parts for the OX5. He also has a restored but uncovered fuselage and I think wings for a 1927 travelair 2 seater just sitting there next to me. He also has a lathe that is 110 years old, still used with its AC/ DC electric motor and leather belt drive. It is geared for cutting various threads and my axles were made on it. My Corvair engine comes to Florida in Feb. Anyone wants to drive or fly, (Lantana airport is close) is invited. It is amazing where building a plane and a Corviar engine takes you. PS In 1968 I bought my love a 1953 stude starliner.-Joe”

On the subject of Corvair College #24 reviewed in pictures:

Aircamper builder Jon Coxwell writes:

“William, I want to thank you for all the time you spent with my engine at CC#24. It was such a joy when it finally fired up. I am certain that if I had tried to fire it up on my own that it would have been very frustrating. Now I know it runs and move forward. I hardily recommend to anyone using a Corvair to get to at least one of your colleges. My engine is now back in my shop on the bench.  I read through the 601 installation manual in the motel on the way home. There is certainly a lot of good stuff in there and I found a lot things that indeed will apply to my GN-1 (piet look alike). I anxiously await the manual you are preparing for the Pietenpol. Each College that I have attended, I have learned something new and made some new friends as well. I want to pass on, that my son was impressed with what you are doing and I believe he thoroughly enjoyed himself. I certainly enjoyed having him there. Living 2000 miles apart means we don’t see much of each other. Thanks again for your help and the great experience.-Jon Coxwell-GN-1 Aircamper”

SP-500 builder, Pratt-Whittney aero engineer and Corvair College#23 grad Spenser Gould writes:

“Impressive photos from cc24, looks like a lot of good process was made at the event by the builders, having my engine run on the stand in cc23 was very inspirational. The work from You, Dan & Ed is a big part in keeping the homebuilt movement going in today’s world.-Spencer”

Builder Dave Gingerich writes:

“Mr. Wynne, could you please send me an email address for Dave Aldrich. I would like to get the data for the Sensenich prop shown. I have a computer program that computes the thrust and horsepower for any speed and any rpm. I have data for the C150 prop, but haven’t been able to get any for a typical prop running on a Corvair powered slow airplane.”

Dave, Mr. Alderich is still working on the plane for the prop. Other than Corvairs, the only part of Aviation that I have some degree of mastery with is props. I have been a dealer for a number of different brands, tested dozens, collected a lot of data, set up an FAA prop repair station, and was lucky enough to have both Ernest Jones and Vance Jauqua as personal mentors on propulsion. ( this is like being able say your two guitar teachers were Jimi Hendrix and Eric Clapton) Let me offer this modest observation: All computer programs are based on an algorithm. Even an incredibly complex set of equations is going to be an incredibly simplified model of what is actually taking place. It is likely just OK at predicting behavior of run of the mill props because that is what virtually all the models are based on. Such a program isn’t going to be accurate at all in predicting the behaviour of a smaller diameter/ higher rpm prop like a Corvair. Ernest Jones had a PhD in this subject, and he directly showed me how a very complex 3D computer wind tunnel model of a prop,spinner/cowling/windshield model reviewed on one degree angle of attack increments painted a different picture of the required prop. If you want to learn more about props, read Fred Weick’s 1930 book. If you want a good prop for a plane your building, data from flying pilots is a far better predictor than computer programs.-ww

Zenith 650 builder Brian Manlove writes:

 “I’m really enjoying your posts once again… and sad that I couldn’t go to CC24. I just stopped by Kevin Purtee’s house yesterday and had a great visit. His garage is quite a testimonial to the great people in the Corvair world. It makes me feel really good to know that I am in the company of such folks and walking a proven path… and I’m inching ever closer. I just finished the right wing for my 650, started on the left, the fuselage is right around the corner. I want to finish N129BZ in 2013. Please keep the comments coming… I hope y’all have a great time at the event, and I’m looking forward to getting to another one as soon as I possibly can.-Brian”