Corvair - General Info

Other VW (Revmaster, Great Plains, Hummel), Corvair, Viking, etc

Re: Corvair - General Info

Postby lpaaruule » Wed Mar 07, 2018 1:56 pm

Hi John,

I'm was aware of the anacdote about tremedous horsepower being produced by VW engines. However, since I was ignorant of whether or not the engines had any longevity past running the 1/4 mile, or other short races, I rejected it as useful info, and stored it as interesting trivia. I would, however, find running a controlled over-stress test very interesting. Perhaps 500 hours at 110Hp on a dyno, though I don't know what the Hp could be without producing a foolish premature failure.

From your recent post I thought that you had genuine curiosity about builders rational for using the corvair, and their surpassing the design gross weight.

From your experience, do you not find any merit from a durability standpoint in running an engine at less than its rated horsepower?
Last edited by lpaaruule on Wed Mar 07, 2018 3:02 pm, edited 1 time in total.
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Re: Corvair - General Info

Postby kmacht » Wed Mar 07, 2018 2:43 pm

Lets be fair here. The aerovees are operating at a horsepower about double the original design but other than the recent connecting rod failure there are very few reports of internal "Chinese" components failing on the motor. Corvairs were not designed as an aircraft engine and they require modifications (i.e. 5th bearing) to make them withstand the rigors of flight just like the aerovee requires many modifications to a stock 36hp engine to make them able to handle 80hp. Neither is a clean sheet engine designed for what it is being used for and there are compromises that have to be made for both to work.

The aerovee can be a reliable engine. I have never denied that. Proof of that are the many sonexes (sonexi?) flying with them installed. Some of those installations have hundreds of trouble free hours. The problem I have is that it isn't understood what is allowing some engines to run trouble free while others are having sudden failures during takeoff. For many years I was of the opinion that it was probably the builder not paying attention to some detail when assembling the motor or failing to perform necessary maintenance. I really wanted to believe that the time and money I had invested in my aerovee was well spent and told myself that those must be the reason why their installation didn't work but mine would. That was until the factory had the same issue on two of their aerovee powered aircraft. The factory should be the pinnacle of correct assembly and proper maintenance and if they can't get it right how do I know I can. You can read John's explanation in an earlier post and decide for yourself if that is sufficient for you to feel comfortable behind your aerovee.

I am choosing the corvair because for me (and just for me) the risk/reward balance is better than the aerovee. I don't expect John or Sonex to ever embrace the corvair conversions as a factory supported engine and don't think it is productive to even ask. They have both business and technical reasons why they choose not to. He did bring up some valid questions regarding empty weight vs useful load but unfortunately I don't think many corvair Sonex owners will bother to respond because of the way it was asked and what he was insinuating about them.

There are risks with any motor you fly behind. You should make sure you fully research all options before making a decision. Your life could depend on it one day. Don't let what you read on an internet forum posted by a random person or what a business with a vested interest in selling their product says be the only thing that you use to decide. Do your own research and make an independent and informed decision

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Re: Corvair - General Info

Postby Jgibson » Wed Mar 07, 2018 4:33 pm

Anyone know the difference between a weight of a full-up Corvair with new crank vs the weight of a fully installed Rotax (including radiators, etc.) AND the full up installed weight of the Jabiru 3300?
Just curious because I distinctly remember the same factory resistance to the Rotax motor until the B model came out using the same tail, same wings, and same tailcone.
Is the Rotax installation heavier, lighter, close?
I'm no engineer, however I'm certain the extra 50 pounds or so of the Corvair could be offset by lighter (glass) panel installations, lighter battery, minimal interior, no paint, etc.
No one, including me, is knocking the VW engine in slower turning power requirements. However it was just never designed to be running at 80 hp CONTINUIOUS in our applications. Show me VW aero conversions that run a minimum of 500 hours without head work, or conversions that don't require continuous re-torquing of heads, continuous valve adjustments, etc. They may be out there, but they are a rarity. The Corvair needs none of these maintenance issues and the ignition setup is bullet proof and redundant IF the William Wynn modified distributor is used. Standard aircraft carb.
The Corvair running in the aero mode is running at a much lower rpm than originally designed in the auto configuration. My turbo made it's 150 hp at 5500 rpm and as I noted in previous posts, I TRIED blowing it up and couldn't. Same with my Fitch prepared 110 hp. So I'm pretty comfortable running it all day long at 3100 rpm WITH a new 5th bearing setup.
Again: my opinions are just that. Mine. However they are based on facts and my own experience with the Corvair powerplants. I respect Mr. Monnet's experience and knowledge and believe he has designed a great airplane and done a lot for light aviation. Nobody is asking or expecting you/him to design a completely different airframe to accommodate the Corvair. Explaining the pitfalls of the Corvair installation, and/or possible structural upgrades serves everyone's best interest.
But dismissive remarks, like those that USED to come with the mention of a Rotax does nothing to advance either safety or promotion of either lite aviation or the Sonex product itself.
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Re: Corvair - General Info

Postby Marrahm » Wed Mar 07, 2018 10:51 pm

According to SPA, the new 3.3 corvair engine with , intake , carburator , carb box, exhaust system, coils, igniton wires,coil joiner,voltage regulator ,cooling baffels ,oil cooler, hoses, starter , generator, propeller, spinner, cowling, and oil is 255lbs, which is 40 lbs heavier than a 33oo jabb install.

Think Sonex nosegear assembly weighs 40 more than the TD FWF setup?

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Re: Corvair - General Info

Postby samiam » Thu Mar 08, 2018 10:30 am

It's a bit of a shame that we can't respectfully talk about Corvairs here and share information; please everyone, let's try to keep it civil.

With regard to John's remarks: I'll start by saying that I have utmost respect for the work that you've done and for your design. I am happy to use a different name than Sonex for a Corvair powered airframe if that is what you prefer.

I think that from my perspective, it is challenging that in this discussion about the suitability of the Corvair/Sonex combination, we are ignoring the 10+ years of successful Corvair powered Sonex airframes with over 2 dozen flying aircraft and no reported issues. This is not an off-the-cuff idea; it has been tried and shown to work very well, and owners are generally reporting to be very pleased.

I was given to understand that Jeremy's comments during the EAA webinar on weight and balance represented something of a "softening" of the Sonex stance on the usage of alternative engines; however, if John feels that using a Corvair is "blatant disregard" for the design then I suppose this is not the case. As it is his airframe and his company, I will respect that decision as it is his to make.

That said, I do think that sharing of W&B data is suppressed because those who have done it are hesitant to come forward because of comments such as these, so it is a bit of a catch-22.

Thank you to everyone who has constructively contributed to this thread.

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Re: Corvair - General Info

Postby jerryhain » Mon Mar 12, 2018 12:18 pm

Marrahm wrote:
Think Sonex nosegear assembly weighs 40 more than the TD FWF setup?


Does anyone know how much weight the nose gear including wheel pant, everything hanging off the engine mount on the OneX is?
I want to know what the firewall forward will be for a turbo aerovee with turbo cooler and the nose dragger on the OneX.
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