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BruceMe

Well Known Member
I've got a line in a project rv-4 for 1500 and I just bought a half converted corvair engine for 600. I'm going to build it single place and dirt simple. W&B should work out perfectly with nobody in the back. I've never heard of a corvair rv anything, it will be wimpy but quite affordable and still a great airplane. Am I really the first?
 
I think you can build the Corvair up to 130 hp. Keep the airplane light and simple, and it will probably be a dream to fly. Won't have the top speed, but I bet it climbs great, and lands VERY slow.
 
Hours of Power...

I've got a line in a project rv-4 for 1500 and I just bought a half converted corvair engine for 600. I'm going to build it single place and dirt simple. W&B should work out perfectly with nobody in the back. I've never heard of a corvair rv anything, it will be wimpy but quite affordable and still a great airplane. Am I really the first?

Bruce,
I inspected two different RV4's with alternative engines over the years, both Mazda rotaries based on Tracy Crooks plans and reduction drive. Both flew well and were flying (like my RV4) for south of Twenty grand. A Cor-Four, should be similar cost.

As you well know, William Wynne's Corvair U has many success stories including a Pietenpol with 1000 hours. More recently though, sixteen Zenith 600 series builders chose the Corvair as well as numerous Dan Weseman's Panther customers. I've known Dan for 15 years and have seen his Fifth Bearing mod to the Corvair up close as well as 2 flying Panthers. My favorite though is the Bearhawk LSA with the 120HP Corvair.

Here is a great link to flying airplanes: https://flycorvair.net/category/flying-planes/

Having now owned and flown a 1835VW powered Sonerai 2 that handled like my RV4 but cost 1/4 to own and fly, I can totally relate with and encourage your progress...

V/R
Smokey
 
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Thanks Smokey

Smokey,

I plan to use PSA/Panther's 5th bearing, I met him at OSH17 and I also talked with William at length too. William doesn't know of any RVs that are Corvair powered yet, other than a guy building a twin RV-6A I also met there.

I'll start simple and just get it in the air stock 100hp. But I really want a flying test bed for lots of weird ideas... The ultimate goal would be to evaluate ultra efficient/hybrid electric-turbo-compound.

Imagine a simplest turbo-charger, no waste gate or intercooler. Now; oversize turbine section as big as possible and add a 40kw dynamo/generator running off the turbine shaft.

Under power the oversized turbine is compressing the intake as "turbo-normal" (~32") and it's also acting like a gas generator extracting an additional 20% of heat energy from the exhaust and putting it into the dynamo to generate electricity. That energy is buffered with a small 2-kwh lifepo4 battery and capacitors and pushed through an ESC to a 40kw motor on the back of the crankshaft.

The last piston-engine technology used all mechanical turbo-compounding to drive the turbine back to the output shaft for power. It was messy and complicated mechanically, but it did boost efficiency by 15%.

I know it's not the easiest, but it is interesting.
 
SPA

I put a Corvair on my Sonex and used Dan's first generation 5th bearing. You can't go wrong with Dan and his products and support.

Have you considered his 3.3L option?

BTW, Dan is one of my best friends so my opinions might be somewhat biased...:D
 
I only listen to biased opinions.

I'm actually considering going totally stock 2700 (mostly cause that's what I have) and for strength when I put a turbo on it. As you get bigger and bigger, the margin for cracking between the machined out case/head and the cylinder stud bolts is paper thin. I may tare it down later, but till I know I really want it, I'll leave it 2700cc.
 
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Hey Bruce,

We try to host an alt engine get-together here in Mississippi at least once a year. So far it's been mostly rotary guys, but they aren't bigots; they welcome all versions of alt engines. I'd like to expand the gathering to a lot of other engine types.

If you're up for a road trip, watch this space; I'll post an invite a month or so before the actual event. We usually do them in late May, but sometimes in September. Depends on scheduling for those who have a strong desire to attend.

And Smokey, you no longer have an excuse; I expect to see you here next time. ;-)

Charlie
Slobovia Outerntional (MS71)
RV-7 Mazda Renesis FWF in progress
 
What time of year? If I fly in on a Lycoming IO-320 RV-4 will I be thrown into the creek? :D

-Bruce

If you were, you'd land on me; my daily driver is an O-320 powered -4. :)

Next event will likely be in late May, but depending on attendees' preference, we might push it as late as September. And we often have an impromptu alt engine gathering the 1st Saturday in November, when a few of the Lower Slobovia families host our annual Pumpkin Drop. Come on down. :)

Charlie
 
Regarding Corvair flight engines, I was initially rather apprehensive. I spend a considerable amount of time researching and eventually going to a Corvair college(multiple events per year where William Wynne and SPA get together with dozens of Corvair builders to make progress, assemble, and often break in and test run their engines on the custom run stand assembly William supplies) and spending time with Dan and William at Oshkosh, etc.

I have come away very impressed with their approach and products. They go to great lengths to design, test, improve, repeat on all their products and procedures. It’s the most open, honest, and professional approach I have ever seen for an alternative engine. I have been fully prepared to do a top to bottom rebuild on an O-200 for my non RV project, it’s not about the money.

IMHO, the Corvair conversion they have developed is mature enough to be considered a very reliable direct drive engine in the 100-125hp range. And yes, the smoothness(lower vibration) of the 6 cylinder balanced Corvair is night and day better than an O-200 or any other opposed 4 aircraft engine. The exhaust tone and overall sound is really pleasant as well, a bit like a Merlin with the right headers.

I’m personally heading down the top end of the spectrum, with a new US made billet stroker crank and new rod package from SPA, going to a full 3300 (200 cu in) with the 5th bearing and all the other well developed parts. One can build a top quality 2700 for SUBSTANCIALLY less.

There have been many who have gone down their own path and developed their own conversion parts for Corvairs(such as the turbo Corvair build in the other thread). I have considered doing some of it myself. But as someone who designs and builds complicated metal parts for a living, I can’t think of a single part that I can design, test, and produce myself that would honestly be as cost/time effective as using the proven parts that William and Dan offer. If you really enjoy that kind of thing or are determined to have something unique, I get it though.

For those interested in checking them out:

https://flywithspa.com/

https://flycorvair.net/

http://shop.flycorvair.com/

George
 
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Regarding Corvair flight engines, I was initially rather apprehensive. I spend a considerable amount of time researching and eventually going to a Corvair college [snip...]

IMHO, the Corvair conversion they have developed is mature enough to be considered a very reliable direct drive engine in the 100-125hp range.

[snip...]
one can build a top quality 2700 for SUBSTANCIALLY less.

George

Thanks George,

I met William at OSH17 and went to one of his forums. I probably will skip the college, but I will follow his path and I'll definately get a Weisseman 5th bearing. I will also go for the "substantially cheaper" 2700cc option. I am considering adding turbo-normal (Same Garret 60 AR hot/ 48 AR cold like Robin, but plumbed like Azalias). This will give it another 10hp down low and some legs for x-country. A solo RV-4 doesn't need much power. It's maybe 100lbs on a RV-3 and they can use 100hp just fine. I typically cruise at 80hp, 11,000' and 140ktas in my IO-320 RV-4 now.

I will push the engine as far forward as I can and hope the W&B is close enough for solo... Or... I'll pull it and drop the 10k for an O-320 :(
 
W&B Calc...

I plugged the numbers raw, no futzing and my hunches where validated.

Here's a W&B I could find handily for an O-320-E2D (lightest 320)...

Weight (lbs) Arm (ins) Moment (lbs. in)
--------------------------------
Right Wheel 441 60 26460
Left Wheel 436 60.3 26290.8
Tail Wheel 56 237.5 13300
Total: 933 66050.8

CG=66050.8 / 933= Empty moment of aircraft 70.8” aft of datum

To that... I altered the engine weight as follows.

A ready to run Lycoming O-320-E2D is roughly #350
A 2700cc Corvair ready to run is roughly #250.

Then I took side view of the W&B and the middle of the cowl is at 30" aft of datum.

So... if I mount the corvair with the flange in the same place.

Weight/Mom/Arm

O-320 350 10500.00 30
Corvair 250 7000.00 28 (it 4" shorter, moves CG 2" forward)

When you remove the weight and adjust for the change in moment, that gives...

833 62272.50

Empty CG - 74.76"

Ok, so the aft CG limit is 77" in an RV-4 and this is a very hard limit. I've flown near it and didn't like it much, it's aft!

So with all that said, running my RV-4 with those empty numbers told me I could fly safely with 4 gal in the tanks (most aft cg) and 50 lbs of "baggage" in the rear seat area and I'd be at the limit. So yeah... it will do it.

So then I started playing with nose extensions... It would take moving the motor 10" forward to bring the empty CG back into the normal 70" CG location.
 
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By the numbers...

Hey Bruce,
Interestingly enough, when I bought my Sonerai from a craftsman's estate, I knew I would eventually have to rebuild or replace the original 2180CC VW it sported since new. Ended up replacing it with a nearly new, extremely custom built 1835CC engine that was flying in a Q2 (planning to go electric).
During the engine R&R I re-calculated the CG as it's even more critical in the Sonerai, especially given the EW is 557lbs and the moment very short. Since the original 165lb 74HP engine left the CG slightly forward, the 143lb balanced/blueprinted 60HP engine would move it slightly aft but reduce the EW, sound familiar?

Since I reduced the EW by 32 lbs, moved the CG slightly aft and the moment arm closer to neutral (4" in the S2), the flight qualities actually improved significantly with little to no performance loss and a turbine smooth power-plant as a bonus. :)
I'm sure you will see similarity in your RV4 as I found my Sonerai had similar numbers to my own RV4, except at half scale. The biggest difference though is the Sonerai II solos from the rear seat!



V/R
Smokey

PS: Similarly to the Corvair, to extract more HP from the VW you have to stroke the crank which inherently places more load on the front bearing as it was originally only supporting a fan belt pulley. Failures have occurred in the past with stroked cranks where the propeller flange hub is pressed onto the shaft. To remedy the problem, the VW aero community has embraced the Great Plains Force One Hub as a "5th bearing" for Strokers (2100CC or greater) and the German factory replacement 69MM forged crank for the 1835CC. Wood props are the order of the day with any VW derivative due to nearly zero harmonics. I'm sure the Corvair shares this as well.
 
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If your into stock in go power, I built RV4 with 165 HP Subaru ,Canadian psru, sds
Ignition/fuel injection .SDS also supplied info on belly rad cooling.EXTRA WORK to
fit cowling around Suby Forrester engine.At full power climbed 2000 fpm, 190 water
temp ,170 oil temp w/o cooler. I can email photos if interested Tom
 
RV-3 Corvair

Bruce, I am currently flying an RV-3b. My engine is a 3100 with a Weseman fifth bearing. Weight and balance is right in the middle of the envelope and it flies well. If you are interested in how my engine is mounted, give me a call. 559-430-7220.

Bill Newkirk
 
Bill and I had a long talk today it was great, thanks bill;

What I can tell you is that a corvair can definitely work on an rv-3. His mount is interesting and pretty heavy and mounting it as far forward as possible he said cg fell right in the middle of the empty range for an rv-3... For comparison a wood prop o-320 is right at the forward limit. So it's somewhere near an o-235 or 290; they weigh similarly. His is 3100cc using vw cylinders and is a WW styled build with the weisseman 5th bearing. He didn't assemble the engine core, but did assemble all the accessories. He says he has red line at 3300rpm and used a pretty small prop in the 56-58" range if I recall correctly. He uses a 2900 cruise limit and wing tip extensions to stay lsa and he may be the fastest true lsa I've heard of. Cruise burns are South of 5gph at lsa limit and 3000. Could get faster true higher.

It's a relatively new build, he's only been flying for a year and 50 hours. I'll post pictures when I get them.
 
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Pictures Bill sent

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Sierra Hotel...

Wow Bruce, this is the most exciting set of posts on this site in a long time..BTW, the tips on the -3 look very much like the late great Paul Lipps designs for the RV6. He also designed very cool props.
I look forward to hearing your Cor-Four numbers when you get it flying!
V/R
Smokey
 
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Thanks Smokey

I'm looking for something different in the next project. I've been throwing around a lot of ideas. But this one will be unique.

I spent the morning putting down my ideas for this airplane on this page. It's pretty out there, but I like to let my imagination run wild. The real project will go in stages, first get a flying airplane, then... We'll see.

https://github.com/bruceme/aerovair

Enjoy,
 
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