Bearhawk LSA Engine Mount, P/N #4201-E
Builders,
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Last year we worked with Bob Barrows, designer of the Bearhawk series of aircraft to make a Corvair Engine mount for his LSA model. In our Catalog, this is part #4201-E. The story of making the mount can be found at this link: Corvair Motor Mount for Bearhawk LSA
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We built mount #1 on a factory welded fuselage. I knew that it would be a while before the first one sold, and it did this week, more than a year after we built it. Vern and I took the time to make a very heavy duty fixture off the mount before we sent it out. In the picture below, the mount is powder coated Haze Gray and the fixture is painted DD Alpine Green.
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I did a rough mental calculation and figured out between the 2 day trip to GA with the truck and trailer to make the first mount, the materials in it, and the shop time making the fixture, I have about $2,500 in mount #1 and the tooling. We have set the price on these mounts at $549.
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This is a good indication why most companies in experimental aviation fail: because the ownership are salesmen who can not physically make nor develop the products they wish to sell, thus they have to hire out every task, and they are often unable to tell if they were done correctly. Additionally they are often fixated on revenue, so they could never develop anything and wait a year to sell the first one. If you ever see a guy in a polo shirt at Oshkosh selling planes using financial buzz phrases like “return on investment” I will bet you 100 dollars to a doughnut his operation tanks in 36 months.
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In our case I am a home builder, a craftsman and an instructor at heart. Yes I sell things, but they are things that we developed and made ourselves. I can afford to work on R&D projects that will yield interesting, but not lucrative results; I can invest hundreds of yearly hours in free teaching; I can deficit spend on projects for months, or even years without having to answer to any investor. When an opportunity to work with a top notch designer like Bob Barrows comes up, my only thought is about what I can learn from the man, not how much money can be made.
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We are here for the long haul. The Bearhawk LSA is a great plane, and over time I hope a big number of them are Corvair powered. When these builders need mounts, we have the tooling and will gladly produce them. But for today, I am very happy to have #1 head out the door, and to have had a great opportunity to work side by side with Bob.
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As I handed over the mount at the post office counter I gave it one last look and wondered how many months it would be until I saw it again, at a College or Oshkosh, bolted on the front of the builders plane. -ww.
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For further reading:
Bob Barrows to Fly LSA Bearhawk to CC #27, Barnwell, S.C., Nov. 2013
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Bearhawk LSA, Corvair motor mount in development
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Above, Bob Grace and myself in our tent at Oshkosh 2013. Bob holds the distinction of having flown to every single Oshkosh, all 45 of them. All of his designs have been Continental or Lycoming powered. Opening the option for Corvair power to his LSA builders is a milestone in the Corvair movement.
Shop Notes, 10/26/14
Builders,
Vern and I were welding in the shop last night until 1AM. In a few minutes, I will be back out there and working all day. Vern and I are working on a very large batch of motor mounts slated to go into power coating on Wednesday. We have less than two weeks to CC#31, and we are in the phase of back to back 14 hour days. It is productive, and many parts are headed, to builders this week, not just to people headed to the College.
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I have laid off writing in recent weeks as we move closer to the College and the end of the year. Some people miss that I do most of the writing when I am on the road, and don’t have access to the shop. I also go through phases where I am convinced that few people read the stuff in detail. The counter on this site is nearing 700,000 page reads in 33 months, but at a recent college I asked 40 builders if they had seen the detailed story Balancer Installation. Exactly zero out of forty had read it. Not very encouraging.
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If you would like to review your own reading list, click on this link to 200 of the 589 stories on this site, they are listed in groups. 200 Stories of aircraft building. In the last 5 years, I have seen less than 5 hours worth of television total, but I have read more than 200 books. Everyone can spend their time how they like, but I get a lot more out of reading than entertainment. If you want to have a Corvair powered plane that serves you, that you really know, reading will be the best path to get there.
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Behind the scenes we have had some real advancements in parts and shop ability. We have had a long wait for intakes because the friend of mine who owns the robotic tubing bending company that made them for us for 10 years has become astronomically wealthy by switching from producing parts for the aircraft industry to the medical industry. O2 concentrators are much better revenue that fuel injection lines. By appealing to our 25 year friendship I have gotten him to agree to make 3 years worth of intake pipes in a single run, and we should have these just after CC#31, and will shortly be sending them out as the flanges and brackets for them are already made.
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This fall I have invested countless hours in getting our Jacksonville cylinder head source perfected. While Mark at Falcon still makes fine heads, his back order list is at least 6 months, and in many cases it has been well over a year. For builders moving faster, we have our new source here. We have had several rounds of test and production heads and we are close to having heads on the shelf to exchange. Right now I have 36 pairs that I own personally lined up to be processed. More news shortly.
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Even shop capability like our cleaning and blasting cabinets are being upgraded here to shorten the time on items like 2000HV oil cases. I bought a compressor so powerful that it can relentlessly hold 175 psi against an open 3/16″ blast gun nozzle. Yesterday the electrician was in the hangar installing a dedicated 100 amp line to run the unit. You can never have tools too big or industrial.
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If you have an important question, please send it to my personal email directly, with a number and time I can return the call. It will likely be too loud in the shop today to hear the phone, but I will be glad to get back to you. -ww.
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From our website in 2011: “For the greater part of his years on earth, Vern has been a welder. In the world of experimental aircraft, when a company wants to sound impressive, they always tout that their welders have “Built race cars.” I welded the frames of lots of NHRA legal dragsters before I was 21, and this experience taught me nothing about aerospace welding. Vern has welded countless race cars together, but that has nothing to do with why we utilize his skills making Corvair parts. What counts is the little piece of paper on the orange board.”
“If you look closely, it shows that Vern has every aerospace material welding rating in every thickness recognized by his employer, the United States Naval Aviation Depot. In this facility inside NAS Jacksonville, Vern has welded every kind of material that goes into modern combat aircraft. This includes titanium, Hastelloy X and magnesium. While some people can weld this when it is new in a purged box, Vern can weld things like the inside of a jet’s burner can while looking through one bleed hole and feeding the rod through another.”
#3410-Nason switch-(For planes with electric fuel pumps)
Builders,
Here is a look at a simple, but important part of the Corvair installations which require electric fuel pumps. Please note: While this part looks identical to the switch we used from 2003-2005, it has a critically different pressure rating, and no Corvair powered plane with electric fuel pumps should be flying with the earlier number. Nason’s part number for the correct unit is SM-2C-5F. I mention this because just this year I found an aircraft in the Corvair fleet still flying the wrong part number.
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The purpose of the switch is simple: If the plane has an accident, and the engine stops but the primary fuel pump is left on, The switch will detect the oil pressure dropping, and automatically cut the primary electric fuel pump off, without the pilot having to act. Note that the system is not used on the back up electric fuel pump, for reasons of having the simplest back up possible. Our 601XL, N-1777W, may not have been the first experimental aircraft to use such a system, but we were the first people to widely popularize the need for it in all planes with primary electric pumps. It was nominated for an EAA award for safety design of the year, but nothing came of this and the idea was not published beyond our personal efforts.
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There are alternatives to this derived from a Bosch system extracted from German cars which cut off the pump if it detects the coil is no longer firing, but no one should ever connect any device to the Corvairs’s ignition system that it does not need. Here is an example of that mistake: MGL vs Corvair ignition issue. No one should connect a tach, sensor or any other device to the ignition system, it is a failure point. I have been writing that for 20 years, but people still do it, and it has caused issues, but thankfully no one has been seriously hurt…yet. Don’t be the first.
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Above is a 2008 picture from our website, with 13 Nason switches, part No. SM-2C-5F. We were reminding builders then to switch to use. This switch automatically cuts off the fuel pump when the oil pressure drops below 5 psi. The original switch was the same function, but the switched closed at 20 psi.
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We started with the 20 psi switch because we originally used the Corvair’s mechanical fuel pump (We stopped this in 2004 when we conclusively demonstrated that all modern replacement Corvair mechanical pumps were prone to leaking), as the primary. The electric back up fuel pump was automatically activated when the mechanical dropped below 4 psi fuel pressure, and was automatically stopped when the oil pressure was below 20 psi. This prototype mechanical/electric system was replaced by modern system we have today in the summer of 2004. We originaly kept the 20 psi switch.
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However, with many builders retrofitting 5th bearings, some engines would have a hot idling oil pressure below 20 psi, and this could potentially lead to a builder gliding in on final with a hot engine and the low oil pressure cutting off the primary fuel pump. Switching to a 5 psi Nason prevents this from potentially happening, We have promoted this almost 9 years, but some builders with 5th bearings missed this important change.
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We now have a large number of SM-2C-5F’s in stock and will be glad to supply them at $43 including S&H in the U.S. It is part number #3410 at this link: http://www.flycorvair.com/products.html
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Above is the ignition wiring diagram for a a Corvair system. The Nason switch is on the upper left. Note that it is only wired into the primary fuel pump, not the back up .-ww.
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The “Outlaw” Kitfox/Corvair project
Builders,
If you have ever thought of putting a Corvair on a Kitfox, here is a story to follow. Below are some pictures of a Corvair being sized up for a Tri-gear Kitfox model seven. We took these at Corvair College #30 two weeks ago.
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The game plan here is to make a set of installation parts for Kitfox models 5 through 7. (They are the same ahead of the firewall.) It needs a unique motor mount, it looks like it will work with our standard #3601-S intake, our #3901C stainless exhaust and we are going to base the cowling on one of our #4102 Nose Bowls.
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A Corvair builder in Texas already flew a 2,700cc Corvair on a Model 5, but it was a non-standard, hand built installation that did not have an aircraft carb. It worked, but not nearly up to the potential of the combination. I have another Texas builder, John Pitkin who is getting closer, but there are also one-off elements of his installation, and he is not in a hurry to get done. This time we have an eager builder who already has a completely standard 3,000cc Corvair done and test run at Corvair College #29. He brought the fuselage to CC#30 so I could get all the data I need to make the mount in Florida. This feels like the right plan coming together to see the plane done perhaps as soon as Oshkosh 2015.
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Now we get to the “outlaw” part of this. I have long talked to John McBean, the owner of Kitfox about doing this. Some aircraft company owners like the Monnetts have politely asked that we don’t overtly promote Corvairs on their designs, and I respect that (The have now reversed their position on this) , others Like Sebastien Heintz said “Buy a kit and have at it.” McBean has been a third path, where he has expressed a desire to make some of the parts and have say over details. I wrote about different company perspectives in this story: Selecting an engine for your experimental aircraft , but Mcbean’s approach doesn’t sound promising to me, mostly because he has never seen a running Corvair and glossed over how unique the exhaust systems are and that they use bed mounts.
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At sun n Fun this year, we reached something of an impasse when he told me that he really wanted every Corvair installation to use one of his Lycoming cowls, a design 7″ too wide for a Corvair, simply because he wanted “his design” to have a “Certain Look.” At that point I decided that he is a good guy, but we have different views on things like who gets to choose how a plane looks (I say the builder does). The best solution is to develop the installation without any input from the Kitfox people. It is my personal belief that if a person buys a plane, it is their personal property, and they have the right to do with it what they want. Doing the firewall forward without the approval or input of the airframe kit maker is what I call an “Outlaw” installation. If you would like a look at how our nose bowls looks on different planes look at this link: Catching Up On Nosebowls ( p/n #4102 ) and at this one: STOL and utility planes for Corvair power.
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If the factory says people shouldn’t use a Corvair on a model they sell, let them make a convincing technical argument why. If it is right, builders will not use Corvairs. Simply telling people to obey works with most people, but a large chunk of traditional homebuilders only follow good reasoning, not commands. Saying “I want your plane to have a certain look” isn’t a technical argument, it is an opinion about another man’s property. Saying “I make money if you buy a Rotax 912, so it is the right engine for your plane” is not a technical argument, it is just an opinion about how you should spend the money in your bank account. It works with some people, just not many of the ones I know and spend time with. When I want Corvair builder to do things like use forged pistons, I make a technical argument why they are needed and make sense. It is a different approach that requires treating builders as intelligent adults.
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Many people are first concerned with what everyone else is doing before making a decision. They believe that finding out what most people are doing is the answer to doing it the ‘right’ way. Actually it is, if you are best described as an ‘average’ or ‘typical’ person. If there was one right way to build a plane, and it was based on what the ‘average’ person was doing, we would all be forced to read Mac McClellan’s editorials, then drive our imported mini van to the barber to get a John Edwards haircut while we read Flying magazine and the Sporties catalog. Then to the airport to use our swipe card at the chain link fence, go out to our Rotax 912 powered tri-geared plane with a glass cockpit, call ATC for permission to fly to the ‘practice area’, spend .8 hours there practicing something from a Rod Marchado video tape while never looking out the windows, Get permission to return to the airport, fly a pattern big enough for a 747-400 (because you were told to) land, put the plane away, and drive home wondering why some people talk about flying as ‘freedom’.
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Conversely, it isn’t my goal in life to be like anyone else. My goal is to follow my own path, as determined by myself, using my rational brain that I was provided with, guided by things that I care about. In 51 years on this planet, I have only been brought closer to that path by people who loved me, and a salesman telling me I have to buy a Rotax 912 is not in the group of people who love me, and for the most part, neither are the people who tell you what you have to do without offering a rational argument. They are just trying to have you obey to make something work better for them, like guy in a tower trying to have you fly a 3 mile final. Traditional homebuilding is the exercise of becoming educated so you can use your rational mind to make choices that are right for you. I am not sorry is that is inconvenient for people who would prefer is everyone was ‘average’. If you have never read it, make a point this week to drive to your local library and spend the one hour it takes to read Jonathan Livingston Seagull, and understand it is an allegory about how the ‘flock’ attempts to peck any individual to death for not conforming and serving the ‘average’ need, but some individuals were not born to blindly serve the flock od society. Bach wrote it 40 years ago, but it is more important today than it was then.
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Above, our mystery man builder, known by alias “318 Detroit” with his identity protected at CC#30. (Isn’t this what outlaws do?) Get a look at how much bigger the fuselage on this model 7 is in relation to the engine than in the bottom picture of a model 4 with a Corvair.
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A very interesting side angle: Before the McBeans owned kitfox, the company built a large number of model 5 kits. If anyone is looking for a very inexpensive STOL plane option, you can run an ad on Barnstormers.com saying “Looking for unfinished model 5 kit.” We have ad 3 people do this, and on average they paid $9,000 for a complete kit that originally sold for more than $22,000. Technically these are not ‘factory supported’ in the same way as people who buy kits direct from the McBean’s, but they do have excellent manuals and they is a lot of on line know how from people who built them successfully.
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The “outlaw” kit above is a second hand buy from Barnstormers. It’s original buyer bought nearly every option available, paying $30,000. He took it home but did virtually no work to it. (I have pointed out many times that our consumer culture indoctrinated people to be good at buying things, but poor at working on them.) Our mystery builder paid only $12,000, because it is a supply and demand issue, and deals like this will always be available as long as homebuilt completion rates are low. At CC#30 I sat down with Mr. “318 Detroit” and he showed me on paper that he is going to have a first class model 7, with a complete high end 3,000cc/12oHP Corvair, all of the items ahead of the firewall like the cowl and prop, and a basic instrument panel and a flight line radio for less money than the original owner paid for the kit.
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This option is not for everyone, and I know from 25 years of working with experimental builders that there are many times more people who will drive to Oshkosh in a $500,000 Prevost motorhome, buy a brand new kit from the McBean’s, order a $40,000 fuel injected Rotax 912 engine and installation kit, and have someone build them a glass cockpit. If they get it done, they will have more than $100K in the plane. Are they taking the right path? Yes, for them. For a more traditional homebuilding oriented person with different goals, like our “outlaw” builder, the option is open to have a very similar performing plane, but a very different experience in homebuilding, for roughly 30% of the cost. Each of these two paths are the right one for the respective builders, and figuring that out for yourself is what making a good personal choice in homebuilding is all about. Before too long another builder will come along, buy a model 5 kit off barnstormers for $7,500, buy some parts from us, put together a 2,700cc / 100HP engine with a Stromberg carb and a Weseman 5th bearing, add some steam gauges and a hand held radio and have $16,000 in the plane, and he will probably wonder why our mystery builder chose to budget so much money.
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Above, a group photo, the freshly run 3,000 cc Corvair engine destined for the “outlaw” Kitfox is on the test stand as a centerpiece. This photo is from Corvair College #29. Can you guess which one of the 31 people in the photo is our mystery builder? Let me make it a little easier; From the left, it isn’t Grace nor ScoobE, The Son and Father Jameson team have their own 2700 Pietenpol engine, Vern works on our team, Bob Lester in the brown hat has a flying 2700 Pietenpol,…..
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At left with me above is Kitfox CEO and owner John McBean. He stopped by the booth at Oshkosh 2013. He is a good guy, and I am not building an “Outlaw” installation to antagonize him, I just choose the term to differentiate the result from the possible co-operative effort we had previously spoken of. He has owned Kitfox for about 10 years, and put a lot of work into restoring the companies reputation, his family is known for very good customer service. I have done more than 50 different motor mount designs for Corvair installations, and more than a dozen very detailed firewall forward designs for Corvair powered planes. I will capitalize on this when working on the design of the model 5-7 installation this winter.
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Above, A kitfox model four in my shop getting a motor mount. The earlier owners of Kitfox made more than 1,000 model 4’s. They are smaller and lighter than a 5 through 7 models, really too light for a Corvair, but the owner of this plane is a friend who weighs about 160 pounds, so it still has a high useful load. We used a #2601R reverse Gold oil filter housing to get the engine right up to the firewall for the weight and balance to be right. the model 5 through & will have the harmonic balancer about 10″ from the firewall. The relationship between the model 4 and the 5-7 is very much like the difference between a Zenith 701 and a 750. they look alike, but the later planes are substantially bigger. This model 4 has it’s own 3,000cc Corvair, already built and run at a College. When completed, this large engine/small plane/light pilot combination will be a short field rocket. Read the whole story at this link: Kitfox Model IV with Corvair mount. -ww.
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Catching Up On Nosebowls ( p/n #4102 )
Builders,
Here is a production news update on Nosebowls, part number 4102.
Above a 2007 photo of Lincoln Probst of Canada gives a visual representation of how it feels to complete your own ZenVair 601XL. This photo highlights our 4102 fiberglass Nosebowl, which is painted blue on Lincoln’s plane. The part of the cowl behind the Nosebowl is sheet metal. This plane is now based in Texas.
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Since we built our own 601XL in 2003, we have sold copies of our Nosebowl to builders. While it is most associated with Corvair powered Zenith aircraft, it is actually applicable to many different airframes.
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Over the years, we have had three different Composite guys make the part. The first two make only a dozen or so each, but the great majority of the production run of several hundred parts has been made between 2007 and this year by a friend of ours in Detroit. The were directly shipped from his shop to builders. In the last year, he landed a contract with Boeing and had a hard time keeping up with his existing work. After it because apparent that we were not going to get this to improve, Grace and I stopped by Michigan on our way back from Oshkosh and picked up our molds.
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I already knew where I was taking them. In Jacksonville, 30 miles from our airport is a well known production composite shop that we have worked with before. The key difference between them and our previous suppliers is they are not a small shop, they have about 12 guys working on the shop floor. They have enough production capacity that supplying our needs will not be an issue. The first week they had our molds they made six cowling sets, more than we have been able to get out of our previous supplier in 10 months. We will shortly have all the back orders on this part covered, and move to having them on the shelf in ready supply.
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Above, our Nosebowl molds and master plug on our side lawn last week. We made them more than 10 years ago, but they are in good shape. Our new shop refinished the inside of the molds and set them up for a zero porosity gel coat finish, greatly reducing the builder finish time. They can now simply be scuff sanded and painted with now filler work at all. You can read more about part number 4102 on our catalog page: http://www.flycorvair.com/nosebowl.html
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Above is a 2007 shot of Rick Lindstrom’s 601XL, built in our Edgewater FL hangar. The Nosebowl shown here came from the same molds.
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Doug Stevenson’s CH-750 Stol in California. This is the same Nosebowl on a 750. the plane is powered by a 3,000 cc Corvair.
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Above a 2007 photo of Gordon Alexander’s Pegzair, powered by a large Corvair, also finished on our shop in Edgewater. If you look close, his plane has the same #4102 Nosebowl. Read the story at this link: 3,100cc Corvair in Pegzair
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Above, the flying 2850cc Zenith 750 built by Gary Burdett of Illinois. It has our full complement of Zenith installation components and one of our production engines. This is a good photo of a 4102 Nosebowl on a 750. Read more at this link: Zenith 750 Flying on Corvair Power, Gary Burdett, Illinois
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The 4102 Nosebowl can be fitted to a broad array of Corvair powered planes. Above,a close-up of Jake Jaks’ Junior Ace on the flightline at Sun ‘N Fun 2009. It’s cowling is based on our Nosebowl
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Questions from potential builders:
Builders,
Here are some questions that came in as comments on other stories:
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Frank Stephenson writes:
“While there will be many different results, I am wondering what the average time before overhaul may be. Also what are we looking at cost wise for one of these engines and the average cost of an engine mount? I am considering selling my current conventional geared C-172 with a C-O300B engine and buying or building something a bit smaller and more efficient. I really don’t know anything about Corvair engines other than I know of several folks who have utilized them, but I don’t really know anything about their results. I have found, in general, that automotive engines don’t make really good aircraft engines, but some VW engines I have known of are an exception and apparently the Corvair engines may be an exception.”
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Frank, the minimum time between overhauls on a well built engine is 1,500 hours. Ten years ago we listed 1,000 hours as a very conservative figure, since then, improvements like using valve rotators have driven the life span up significantly. The Overhaul cost on the engine is very low, on the order of $2,000 to replace almost all moving parts or recondition them. You can lean more at this link: Basic Corvair information I understand that many automotive engine engines have a poor record, but I have been doing this for 25 years, and we have earned an excellent one. You can read this link: Planes flying on Corvair Power, and see many examples. For the cost of motor mounts, just look at out catalog,http://www.flycorvair.com/, and page down to Group 4200, it lists the price of every mount we make.
I know VW engines have worked for many people, but I will put the track record for reliability, power and TBO of our work with Corvairs against any VW based engine. There is a lot of information on our main webpage, http://www.flycorvair.com/. I understand that it looks overwhelming, but better too much than to little.
Here is an important point: I don’t think efficiency is a good enough reason to move to homebuilding. Lets say your Cessna does 110mph on 8 gallons an hour. There are several Corvair powered planes that can do that on 5 gallons an hour, even some on 3 gallons an hour. But even if you were to cut your fuel costs on flying 200 hours a year from $8,000 to $4,000 per year, I don’t think it is enough motivation to send a guy to the shop for 1,500 building hours. The only people that consistently succeed at homebuilding are the people who inherently would rather fly something the personally built, and people motivate by the desire to learn new skills. I have met very few people motivated just to fly less expensively who thought in the long run that homebuilding was worth it. Consider this carefully, you may have a better time staying airborne in the plane you have.
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Steve Spears
“Sir, I am currently building a RW26 Special ll and I would like to use the Corvair engine. However, some people are telling me that it is to heavy for the aircraft. What are your thoughts and do you know of anyone who has used a Corvair engine in the Rag Wing aircraft? I read what you wrote about the Pietenpol and am encouraged that I can use the engine”
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Steve, I looked at this pretty closely for an hour the other night. I tend to think that a Corvair is too big to the R-26. The 912 appears to be as large an engine as people use. Several of Rodger Mann’s designs have flown with Corvairs, but I wouldn’t call any of them an ideal match. I am guessing that a Rotax 503 is really the optimum engine for many of his designs. For a comparison of how heavy duty a Pietenpol is built, the longerons in the fuselage are one inch square spruce from the firewall to the tail post. I am pretty sure the R-26 is lighter than that.
For any plane that you are wondering about Corvair power for, the best rule of thumb is asking if the same plane has flown with a Continental o-200. If it has, a Corvair will always work in it. For a comparison of the two engines look at this link:Corvair vs O-200….weight comparison and this one:Dynamometer testing the Corvair and O-200. We also have a lot of info on comparisons to 912s at this link: Testing and Data Collection reference page. -ww.
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carbs, mags and certified engines
Builders, I wrote the comments below to address a guy who put a 65 continental on a new homebuilt, rebuilt the carb himself, and couldn’t make it even slightly hint of running in two hours of hand propping. The man was not a mechanic, never built a plane before, and had never soloed a plane. He went on a net discussion group to ask others how to start his plane, and got some advice on starter fluid. the comment below was to hopefully get some builders to look at the bigger picture, that reliability isn’t cast into the metal of certified engines, it is in the attitudes and decision making of the people working on and flying them.
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I have been an light aircraft mechanic in Florida for a long time. One of inspection tasks that is occasionally done is looking over a single engine plane before it flies to the Bahamas. The gap from West Palm to West End is 56 miles, and smart pilots, particularly those renting, get another set of eyes on the plane before they stick their family in it. When given 30 minutes to evaluate a certified engine’s condition on the ramp, my focus is on the Mags and the Carb, as there two are the most likely sources of taking a swim. A slightly low compression cylinder is not the same trouble as a failed mag on a 95 degree day with four people in a C-172. If the Mags and the carb are working perfectly, odds of other trouble are quite low. The slightest hint of issue from either is a good reason to delay the trip.
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The exact same logic applies to Experimentals, and I can make a statistical case that flying the 40 hours on a new homebuilt, even one with a certified engine, is greater risk than flying for a week in the Bahamas. If a neighbor chose an A-65 Continental for his newly built Pietenpol, I wouldn’t be concerned that the basic engine had 800 hrs. on it. If it has consistent oil pressure. it is not likely to throw a rod, but I would advise him to stack the deck in his favor and make absolutely sure that he had a perfect Carb and Mags on it, as they are the likely source of any issue.
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When looking at the O-320 headed to the islands, I look at the logs to make sure that the last people who touched the mags and carb were in a repair station, or the factory. After visual inspection for leaks and security, I run the engine to full power and try to make it misbehave with the throttle and mixture. A critical test is full static power and slightly leaning must show an rpm increase. Carb heat must work, and cutting off the fuel and letting it idle must cause a 25-50 rpm rise before it quits. Engine must idle as solid as a rock. Turn the prop and feel for low compression and listen for impulses to click at the same time. The 1/2″ nuts holding the mags are checked for torque. Hands on mags to make sure they are secure. Leads traced to look for cuts, every 3/4 nut checked. Engine is started and the key is messed with to make sure a worn switch will not short. The run up is performed with the engine heat soaked, because mags have trouble when they are hot, not cold. Zero tolerance outside of limits on mag drop. The goal is to find the circumstances in which it misbehaves, not to show that it runs ok. Any discrepancy on mags or Carb, even one that is hard to quantify, is cause for the delay of the trip. If I bring any issue to the pilots attention and he responds with a variation on “It will be alright” I never fly with him nor work for him again. I am not a cat, I don’t have 9 lives.
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If a newly finished home built has a used certified engine on it, and the builder is having trouble starting it, odds are the trouble is with the Mags or the carb. If it is stored in a reasonably dry place, a piston in a bore can happily wait 20 years to be re-stared, but the points in mags don’t like this and carbs don’t like fuel, especially auto fuel evaporating from them. (The sole common exception to the mags-carb rule is the camshafts on Lycomings left to sit often corrode and if the engine is run without correcting this the grind the lobes off in a few hours and pump the metal through the oil system.) A homebuilder is allowed to fix his own carb and mags if they need attention, and there are manuals and parts lists on the net, but I can make a case that this isn’t always smart.
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Looking at the carb: aircraft carbs are deceptively simple, and they look far easier to rebuild than a four barrel. Here is the hidden issue: Many carbs on engines for home builts are 60 years old and have had long periods of inactivity, previous owners mix and match parts, and people who like to drill out jets. A skilled guy in a FAA fuel system repair station can spot all of these, but a homebuilder is likely blind to them. I like aircraft carbs, and I teach people to use them after sending them to a professional. Maybe 3 of 10 NAS3’s or MA3’s sold at fly marts have mix and match parts inside. Hard starting is not the worst thing about poorly tuned carbs. First, a carb that is set too lean or has a malfunctioning enrichment circuit will damage the engine in flight. Second, ones that don’t run smooth will often quit at idle. Put this on a hand prop plane and combine it with the fact that many pilots don’t fly every pattern power off, and the new homebuilt ends up 100 yards short of the runway threshold. For more info on carbs, look at this link: http://flycorvair.net/2013/12/03/carburetor-reference-page/
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I do not trust mags that have no logs, were repaired by amateurs, or have had a decade with no inspection of any kind. My neighbor owned a Mag test bench that could run all brands and evaluate them with proper loads on the leads, a tool you find in a Mag repair station. He just sold it on Ebay and got $4,000 for it. If it was actually possible to properly evaluate, repair, overhaul and test aircraft mags without this tool, then it would not be possible to sell it for $4,000. It is legal for a homebuilder to ‘repair’ his own mags, but no rational person who make the argument that a first time amateur without the test device could do as good a job as a professional with the correct equipment.
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Now lets think about a new Pietenpol getting ready for it’s first flight: Plane is built by a nice guy, but planes are a hobby, not a career. A tech counselor looked at it, but that man’s experience was building one RV-6A, and all his “looks good” offered was a false sense of security. It passes the FAA exam, with a DAR that charges $400 but didn’t even ask to see it run. The plane is out of rig, but no one knows this yet. The low time pilot’s time in type is two trips around the pattern at Brodhead. He got 3 hours of tail wheel in a Cessna 170, (a plane that could land itself) but he was not allowed to solo it. The pilot has never flown anything that has the short glide ratio of a Piet. At his last Biennial the CFI allowed him to drag the 152 in with power and plop it down on the runway. He is nervous enough even without the video cameras, but there is a growing group of spectators adding pressure. Under these conditions, does it sound smart that he is also flying the first aircraft carb that he has ever ‘rebuilt’?
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A small continental is an easy engine to troubleshoot if you are trained on them. This training can come in many forms, but the most effective is learning them in person, from someone who knows them. Theoretically you could learn to fly by reading a book, but everyone understands that in person flight training works. I only make the same point with maintenance, that instruction is best, person to person. On a relative scale, making one run that is reluctant to start is very easy compared to doing an airworthy job overhauling a carb or a mag without specific tools or training. Everyone is entitled to their own opinion about this, but what ever difference in opinion is, the wager riding on the opinion is the same, the whole value of the plane and the lives of the people in it. Place your bet carefully.
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I like Continentals, and have a lot of time flying behind them. Their primary quality is reliability. This well earned reputation was made seven decades ago, when homebuilding was still illegal in the US. The Continental reputation was built on relatively new engines, installed at factories, and maintained by trained, licensed A&E mechanics, in a era where people had longer attention spans. Seventy years later, anyone expecting that the same reputation magically lives in the metal is deluding themselves. To get the same results, you have to get as close to the original format as possible. But the issue is that the parts can be old, the details of the installation on a homebuilt can be weak, and the guy working on the carb may have never built one before. Is the issue beginning to make some sense?
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To even get close to the original reliability, One must spend some money on parts, the used parts must have a history and be within limits, and critical items like mags and the carb should be done or at least checked by a repair station. You can choose to do otherwise, but it is not possible to then argue that you can expect the full reputation for reliability. Anyone who thinks that you can have the reliability of a certified motor when you buy one that is advertised as “no logs” or “experimental only” is mistaken. You don’t get to have it both ways. Continental’s reputation was not built on engines made of junk and spray painted. If the engine was just as reliable with out of spec parts, then they wouldn’t be out of spec would they?
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There are always people who argue that they have to have “a reliable certified engine” and that they will not fly auto engines. Then the first thing they do is go out and look for the cheapest collection of parts bolted together that are masquerading as a “certified” engine, made of out of spec parts. That behavior isn’t rational, but people who are compulsively cheap often are satisfied with the illusion of reliability instead of the real thing. Want to know who isn’t fooled by this? Our old friends Physics, Chemistry and Gravity. If the FAA considers the engine un-airworthy in a certified plane, it is just as un-airworthy in an experimental one. Physics, Chemistry and Gravity don’t care if the plane was built in a factory or your garage. An engine built of out of spec parts doesn’t magically become airworthy when it is bolted on an experimental.
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I am an Embry-Riddle trained A&P with 24 years of continuous work on light aircraft. I am qualified to work on virtually any part in GA planes, but that doesn’t mean I am reluctant to hire other mechanics with greater experience and better tooling. When the right mag had excessive drop on the C-85 in my wife’s Taylorcraft, I could have replaced the cracked coil myself, but instead I took both mags to a repair station and waited while they were overhauled. In the last 10 years we have finished several home builts, and I could have overhauled each of the carbs myself, but I elected to send them all to a certified repair station. The difference between ‘fixed’ and ‘Yellow tagged’ is often hundreds of dollars. It sounds like a lot of money until you have lived through two plane crashes and attended a few funerals. 90% of the people reading this make more money than I do, and 95% have less experience with aircraft engines. If those people are trying to save money by fixing a mag or a carb themselves, when I would send the same part out, they should rethink that plan.
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My known specialty is training amateurs to build aircraft engines for experimental aircraft. It doesn’t matter that the hardware is mostly Chevrolet and not Continental, It isn’t about metal, it is about the capacity of builders to learn, and I am not speaking of turning wrenches, I am speaking of learning to make good decisions in a very unforgiving environment. No one has to agree with my perspective, but I have been doing this for long enough, with enough homebuilders that it is worth considering carefully. Homebuilding, including building engines, can be done with reasonably low risk, but only when the builder makes good decisions. -ww
Turbocharging Corvair Flight engines Pt. #2
Builders, Here is part 2:
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“Boosted” engines: If normalizing is trying to maintain 29.92″ of sea level pressure in the intake, a boosted engine is driving the manifold pressure above this. This is actually very common, and almost every single classic radial engine was “Boosted”, except they most often used superchargers to do this. A P&W 450 hp radial is known by its displacement “the 985″ is how many cubic inches it has. They make their rated power at 36.5″ of manifold pressure. Many other classic piston engines made their power at 45 -72” of manifold pressure. High end GA engines like the GTISO-520 makes it “low power” 375 hp rating at 40″ MAP. In the big picture it is ‘turbo normalizing’ that is the oddity.
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In the car, the turbo Corvair is a Boosted engine. The 180 HP ‘Corsa’ model made its rated power at 5,200 rpm and 45″ MAP. That is about 7 pounds of boost in car-speak. Worth noting is that the same engine made 265 foot pounds of torque was down low in the rpm band, at a setting that can be used in a direct drive engine, and the turbos we have used are far better at building torque that the car original was. A 3,000 cc engine running 40″ MAP on takeoff is burning the same amount of fuel and air as a 4,000 cc naturally aspirated engine. If that doesn’t sound dramatic, read this story to understand what kind of difference 35% more power makes on a plane’s climb performance: Pietenpol Power: 100 hp Corvair vs 65 hp Lycoming
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Draw through vs Blow through: On a draw through arrangement, the air flows through the carb, then the turbo and on to the engine. A blow through is turbo-carb (or injection) and then the engine. Draw through is characterized by simplicity. Our set ups are all draw through, as was the original Corvair car. Virtually all modern cars are fuel injected, and the ones that are turboed are blow through. The primary advantages are two things which don’t matter to planes, throttle response and emmisions. One of the hidden advantages to draw through is the fuel getting fully vaporized early radically cools the intake air and makes it more dense without the need for an intercooler. Injected engines can’t do this because the fuel arrives in the intake just ahead of the valves. In one minute at full output, a turbo engine will digest and vaporize more than a pound of fuel, this has a great cooling effect on 250 cubic feet of air.
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One of the things that always comes up when you mention draw through arrangements on planes is an alarmist pointing out that every foot of the intake has air and fuel in it under slight pressure, and this is in his mind a giant fire hazard. A dozen years ago it was mentioned on the Dragonfly builder’s list that I was working on a draw through arrangement for the Corvair. The leading ‘personality’ on that list wrote a long diatribe about what a horrible person I was, and convinced most people of this by saying that no airplane was made that way. Only one problem with his argument, it was a complete lie. The US built 300,000 planes in WWII; 160,000 of them were multi engine, and 32,000 of those had four engines. If you look at all the radials, the Allisons and the Merlins on these planes, You are looking at 750,000 engines, and virtually every one of them was a draw through arrangement being boosted by a turbo, a supercharger or both. A R-4360 engine has at least forty, (40′) feet of intake piping after the blower, and every bit of it is packed with fuel and air. There are 56 couplings in that intake system that I can think of. If draw through systems didn’t work WWII would have had a different outcome.
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For a look at some of our ground testing we did in 2004 before flight testing, get a look at this link: Testing Turbo Corvair and Rotax 912S. In some of the tests we ran the MAP all the way to 60″, which is 15 pounds of boost, or a 2,700 cc engine inhaling the same amount of air as one that is 5,400 cc (330 cubic inches) The turbo we were using was a modified Garret TO-4B with a .58AR housing, machined for a carbon seal. It worked great. Not all turbos are expensive, this one was made in the USA and it was only $545 brand new. The real cost of a full turbo system is far more, because many of the other parts like the exhaust system have to be made from very high quality materials. If you look at the price of turbos on Ebay, be aware that the market is flooded with counterfeit name brand turbos that are made in red China. A turbo counts on good materials, it often runs 1,600F on the inlet and the wheel is turning 100,000 rpm while it is working. If it breaks a blade or bearing, it feeds the metal from the compressor side right into the engine. It pays to buy the real thing, especially because the US made items are often reasonably priced.
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We learned a lot in testing. My plan was to take the regular 2004 100 hp conversion on the Skycoupe and run it with the turbo on it and get some time on it to see what parts would need to be upgraded to last on a turbo engine. First, let me say that nothing on the engine broke, but judging from the 1550F EGTs and high oil temps, the engine would have gotten ‘tired’ quickly with the stock conversion parts of 2004. When I see people talking about putting a turbo on an engine out of a junkyard that was never intended to be turboed, I can only wish them good luck, because our testing indicated that any engine running in a boost condition will need the best available internal parts and systems.
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Below is a number of things our testing indicated we needed for the engine to work as a regular, long lived power plant. After each topic is a link to a story of the part we developed to address each of the issues. These developed systems also served as stand alone options that have improved regular naturally aspirated Corvairs, but the owe their origins to conditions our testing identified 10 years ago.
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Engines in lower compression and more displacement with a quench: The 2,850 pistons were developed specifically to work with turbocharging. They also happen to work very well as a dual fuel piston suited to both 100ll and auto fuel. The 3,000 cc models we developed as a spin off. read the stories by clicking on the links:
Getting Started in 2013, Part #16, 3,000 cc Piston/cylinder kits
Getting Started in 2013, Part #14, 2,850 cc piston/rod/cyl. Kits
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Pressure retard distributor: When an engine is boosted it need less ignition advance. This is done on a Corvair car with a pressure retard in the place of the vacuum advance on the stock distributor. In the Skycoupe I made a special dual points distributor that only had 25 degrees of total advance. The long term answer was the system below. As a tech spin off it will also be useful on naturally aspirated engine at very high altitudes:
Ignition system, experimental “E/E-T”
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Ultra high grade exhaust valves: We normally use 4-N stainless valves in Corvairs, but the exhaust valves of turbo motors need to be made of exceptional materal to last to a normal TBO. This is a job for the super-alloy Inconel. Mark Petz of Falcon head fame developed these in 2008. See picture below:
Above, I hold the last word in Corvair exhaust valves. In the past year, Mark Petniunas put a tremendous amount of effort into finding a source for these valves, which are precision manufactured out of the super alloy Inconel. It has greater strength at 1,500F than 4130N steel does at room temp.
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321 stainless exhaust. Our normal exhausts are made of 304 stainless, a very high quality material, but the job is better done by 321. Very few experimental engine companies have ever used this because it is 3 times the price of 304. The link below is about our regular systems, at the bottom of this page is a photo of a 321 system I made for a 601XL test.
Stainless Steel Exhaust Systems
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high volume oil pumps: Turbo engines need more oil flow to feed the bearing in the turbo, the 5th bearing and to internally cool the engine. High volume oil pumps have been around for a long time for Corvair cars, but we developed our CNC model which has better internal alignment:
High Volume Oil Pump
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large aircraft oil coolers. Turbo engine make the oil hot, it flows through the turbo’s bearing with is one inch away from the exhaust housing which can be visibly glowing. Our Gold oil systemens serve many purposes, but they would serve a turbo engine very well and allow the use of a appropriate sized cooler:
Heavy Duty Gold Oil Systems, new cooler model.
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5th bearings: These were in development by the time we were doing our turbo testing, but we did not have one on the skycoupe. Today, virtually all Corvair flight engines use one, and I would not consider building a turbo engine without one:
Getting Started in 2013, part #1, Crankshaft process options.
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I am holding the turbocharger that Woody Harris found for our test program. Note that it has an integrated wastegate. This is a common feature on modern car turbos. However, almost no modern car turbo has the capability of being used in a drawthrough application, which is a highly desirable format for aircraft use. It took us a long time to find an expert on turbos who could properly fabricate a modern turbo, appropriately sized for our application, with a carbon seal.
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I built this exhaust System out of 321 stainless. Its future home is on Woody Harris’ 601 XL. He will be retrofitting his 2,850 cc engine with a turbocharger. This is the engine half of the exhaust system, and it was built in my jigs. Our regular exhaust systems are built out of 304 stainless, which is extremely durable and fairly resistant to heat flow. 321 is the alloy of choice for Turbo Systems, as it withstands elevated temperatures even better. Notice how the one pipe crosses underneath the engine to go over and meet with the other before heading into the Turbo. It is worth noting, however, that naturally aspirated Corvair powered 601s with 2,700 cc engines have exceeded 17,000’ and have little problem with density altitudes over 14,000 feet.
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Turbocharging Corvair flight engines, Pt #1
Builders,
I am going to sweep together much of the info we have on turbocharging Corvairs here and have it as a reference page for builders, with links to other previous information I have written on the subject.
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Why put a turbo on a Corvair Flight engine? For more power. Corvair cars were the first mass produced turbocharged passenger cars. Many people who know little about cars mistakenly think it was the Porsche 911, but the Corvair Spider beat the Carrera to the market by a full 12 years. The Corvair was designed from the start with the possibility of boosting the output by putting a turbo on it. Above all, it has the cooling for this. Engines that barely have the cooling to run naturally aspirated don’t stand a chance with a turbo.
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Our work with turbos on flying Corvairs: Most of our flight test work was done in 2005. The information was of personal interest to me, and many builders expressed an interest also. But as a reality check, A turbo on a flying Corvair was not really something 95% of builders needed. Also, bringing our test bed aircraft to airshows and speaking with builders taught me that the great majority of people who expressed interest had little appreciation of the complexity and often they had very unrealistic expectations. The best example of this was the majority of people saying “I don’t want a boosted engine, I just want it turbo-normalized” Clearly some of the sources of information on turbocharging of planes that people were reading was not written from a practical experience. Having a flying plane was done, but there was a lot of work to go before builders could understand what the motor would entail, what it would be good at, and what it could not practically do.
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Above is a 2005 overhead shot of our test bead aircraft the Turbo-Skycoupe. It is easy to see the stainless heat shield over the hot side of the turbo in this view. You can see more photos at this link: More Turbo Skycoupe photos
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Turbo-normalizing engines: Picture a naturally aspirated 100 hp Corvair powered plane climbing out from an airport at sea level. The pressure is 29.92″ there. Now picture the same plane taking off from Leadville CO, at 9,927′. The air there is has only 65% of the density it does at sea level. A turbo could easily put this right back, but here is the in-escapable issue: You can only do this with an inflight adjustable prop. If you tried it with a fixed pitch prop that worked at sea level, the prop would radically over speed at altitude. If you put on a fixed pitch prop that absorbed 100 hp at 9,927′ and then tried to take off from sea leave without boosting the engine past 29,92″ on take off, the plane might not even spin the same prop to 2,500 rpm. performance would be very poor, less than a naturally aspirated 100 hp motor with the right prop. The bottom line is you can’t turbo-normalize any plane unless it has an in flight adjustable prop. They exist, but they cost nearly as much money as your motor will. The good news is that a turbo-boosted engine still makes sense in some applications, and it works with a fixed pitch prop.
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The Vne problem: Many people who like the idea of a turbo say “I want to get up high and go fast.” OK, this can be done, but here is a very real issue: Many light planes, especially experimentals, can already operate near their Vne (Velocity Never Exceed) speed. If you add a turbo to them, they will be able to fly right through it in level flight, a very bad idea. People debate this, but here is the reality that the educated side of the argument knows: Vne is based on TRUE airspeed not indicated. If you are in a plane with a Vne of 200 mph, and you are at 10,000′ and indicating 170 mph on a naturaly aspirated engine, you have no where to go. This is because your true airspeed will be 199 mph, and that is 1 mph below your Vne. Put a turbo on that plane and you can’t use it to increase the high altitude cruise. This is a very common condition for Van’s RV aircraft, and it is a big part of the reason why you don’t hear about them being usefully turbocharged. With Corvairs, the common example is the KR-2s, which can fly very near it’s Vne naturally aspirated. If someone around the airport tells you I am wrong about this, look it up for yourself in Aerodynamics for Naval Aviators. I can’t sing nor dance, but I did learn some things in my 5 1/2 years at Embry-Riddle.
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Above, Arnold Holmes and I stand behind the engine installation on a V-8 powered Lancair IV-P. This is an EngineAir package that I helped develop from 1993 to ’98. It’s 450hp, geared, injected, intercooled and very heavily turbocharged.
Most of the people commenting on turbocharging piston planes have little experience with it. In 1996 We took a Lancair IVP like this one on a test flight to 32,500′ I have a number of hours aloft above 29,000′ in these planes. Very few people have flown that high in light piston planes, and truly very few have worked on the engines and system that worked in this environment. You can learn a lot; example, you can easily overheat an engine even when it is 30 below zero outside because the air density is low, and it can’t take many BTU’s out of the cooling system.
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There are also many practical things that directly relate to turbocharged Corvairs such as techniques of welding 321 stainless tubing. Many new guys like to talk about selecting the turbo itself, but my experience says that the reliability of the system has a lot to do with details like how large the radius in the exhaust bends are, if the welders are really careful to come off the Tig pedal slowly and not to leave tiny ‘craters’ on the ends of weld beads, and a bunch of other details. Dozens of companies have on line catalogs to pick turbos, and people regurgitate that info all the time, but real installations have to be very carefully fabricated by experienced people.
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Get a good look at the size of the 5-blade MT propeller. Air is thin at 30,000′ and to absorb 400 hp there, you need blade area, speed and lots of pitch change . Contrary to what some people think, even though this engine was geared 2.19 to 1, it only needed 74″ of diameter to be optimized for the task.
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on to part #2…..
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