# Looks like it is Corvair power for my Vari-EZE

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#### patrickrio

##### Well-Known Member
I helped on several Vari/Long EZ builds in the wing smoothing (sand sand sand) phase 30-40 years ago, and I have been out of the loop since then so my knowledge does not have the benefit of internet correspondence....there is likely better information on this topic available now and my info is probably worth less these days... but:

The planes I worked on had mostly done poorer foam hotwiring and as a result had more micro and fills resulting in tail heavy weights before the engines were added. Even the lightly constructed Vari-Eze's had to be really aggressive in keeping low weight on the O200s and the ones with heavy fills would still need to add even more weight to the nose. The thus heavy Vari-Eze planes had noticeably worse flying qualities. For these planes, you are probably better off with lighter construction with poorer smoothing than being super smooth and heavier. Because of the Vari-Eze fill/weight issues, I bet some of the lightest O200 installs ever are in Vari-Eze's, so you are often not comparing a light Corvair to an average O200.

Do weight and balance checks on your airframe VERY carefully before committing to the Corvair route. It won't matter how much weight you pull out of the panel if you have to add a bunch of nose weight to balance the engine install (and then you have one that fly's like a dog anyway....)

Even though perfecting the Yamaha install for a Vari-Eze may be a pain in the ass and time consuming, it might be your best chance of keeping the engine end light and thus keeping added weight out of the nose if your airframe is constructed tail heavy like many.... Your panel lightening will just make the need for a lighter engine even more likely.

And with a radiator, you may be able to move some install weight further forward too (and add cabin heat if you live in Minnesota...joke, you won't want to add even that weight....)

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#### dwalker

##### Well-Known Member
I helped on several Vari/Long EZ builds in the wing smoothing (sand sand sand) phase 30-40 years ago, and I have been out of the loop since then so my knowledge does not have the benefit of internet correspondence....there is likely better information on this topic available now and my info is probably worth less these days... but:

The planes I worked on had mostly done poorer foam hotwiring and as a result had more micro and fills resulting in tail heavy weights before the engines were added. Even the lightly constructed Vari-Eze's had to be really aggressive in keeping low weight on the O200s and the ones with heavy fills would still need to add even more weight to the nose. The thus heavy Vari-Eze planes had noticeably worse flying qualities. For these planes, you are probably better off with lighter construction with poorer smoothing than being super smooth and heavier. Because of the Vari-Eze fill/weight issues, I bet some of the lightest O200 installs ever are in Vari-Eze's, so you are often not comparing a light Corvair to an average O200.

Do weight and balance checks on your airframe VERY carefully before committing to the Corvair route. It won't matter how much weight you pull out of the panel if you have to add a bunch of nose weight to balance the engine install (and then you have one that fly's like a dog anyway....)

Even though perfecting the Yamaha install for a Vari-Eze may be a pain in the ass and time consuming, it might be your best chance of keeping the engine end light and thus keeping added weight out of the nose if your airframe is constructed tail heavy like most.... And with a radiator, you may be able to move some install weight further forward too (and add cabin heat if you live in Minnesota....)
I appreciate the input, but as mentioned several times above, the Corvair motor is THE SAME WEIGHT OR LIGHTER than the 0-200. Depending on configuration it can be lighter.

#### BoKu

##### Pundit
HBA Supporter
I get the feeling you are roundabout referring to the powerplznt
The service bulletin behind the 2.5g restriction discusses issues with the wing spar and wing panel attachment fittings. Keeping the non-lifting parts light reduces the stresses on those parts. The weight of the lifting parts (wings and foreplane) matters a lot less, since any extra mass is reacted directly by aerodynamic lift forces, and doesn't contribute much to the bending moment in the wing spar.

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#### dwalker

##### Well-Known Member
Yes I read that, and I had a V-EZ flyer explain to me what to look for with the wing attach fittings.

#### BBerson

##### Light Plane Philosopher
HBA Supporter
I was thinking Rutan had problems with the fan cooled VW as a pusher. The Corvair is fan cooled and probably doesn't have the fins of a continental, same as a VW.

#### rv7charlie

##### Well-Known Member
Does anyone run the cooling fan on a Corvair? I've never seen the fan stuff on one in an a/c. For that matter, I've never seen the cooling fan on a VW in an a/c.

#### BBerson

##### Light Plane Philosopher
HBA Supporter
Molt Taylor used cooling fans on his pushers. Need enough static pressure to flow for the horsepower required. Pushers have less pressure.

#### b7gwap

##### Well-Known Member
Bernie Pietenpol used the stock corvair car fan and shroud, but most modern installations mimic the successful baffling used in certified Lycoming and Continental installations. The fan is mounted on a heavy cast aluminum bearing boss that doubles as the top cover plate of the engine. It adds some 8-10 inches of height to the engine. The fan is magnesium and lightweight, but it would also require you to retain the fan belt pulley bracket, AND risk damaging components and lines near the firewall in the event of a belt break. WW recommends against using it unless you’re doing a Pietenpol replica. Although it probably would draw more cooling air into the pusher cowling.

The Corvair heads have a lot of fin area, but I don’t have data on how it compares to a Conti or Lyc. Imagine though, having an air cooled engine that needs to survive idling in LA freeways and has a never exceed CHT of 575F.

Does Bill’s EFI completely do away with the rear distributor drive?

Outside the box, have you considered an O-200D?

#### Marc Zeitlin

##### Exalted Grand Poobah
The service bulletin behind the 2.5g restriction discusses issues with the wing spar and wing panel attachment fittings. Keeping the non-lifting parts light reduces the stresses on those parts. The weight of the lifting parts (wings and foreplane) matters a lot less, since any extra mass is reacted directly by aerodynamic lift forces, and doesn't contribute much to the bending moment in the wing spar.
We're getting pretty far afield here, but if you're concerned about bending stresses, then of course you're absolutely correct regarding wing/canard weights. However, weight is weight, and it affects rotations speeds, landing speeds, brake wear, climb rate, cruise speed, landing gear stress, etc., as of course you know.

So while from a strength standpoint, wing weight isn't nearly as important as the centerline weight, from all other aspects, it's still meaningful. Just wanted to emphasize this point, although you were clearly aiming your comments at the wing attachment corrosion and subsequent "G" limit issue.

#### Marc Zeitlin

##### Exalted Grand Poobah
I was basing it on a possibly flawed memory...
BTDT.

...of having read about a builder who had done both, and downdraft proved out to be markedly better.
Yes - there are a few folks that have implemented downdraft cooling on Long-EZ's and it works great for them. I didn't say that it couldn't work - it clearly can. But I also know of downdraft implementations that are marginal at best, but it's not worth it to the owner of the plane to pay me a boatload of \$ to switch back to the plans system. The question was whether downdraft is better in general, and that clearly is not proven, and there's very little data to support the contention, if any.

In any case, we should all know that "anecdote" is not the singular term for "data", and one data point can have a line drawn through it in any direction one chooses .

...One concern I have is routing the air up through the exhaust vs down from the top. The spacing of the 6 cylinders being tighter than the 4cyl engines seems like it will make updraft baffling a much tougher challenge.
So _IF_ you end up using a Corvair, then your concerns may be valid, because it is different than an O-200 or O-235 with respect to how the air flows through the fins. You might want to search for updraft cooled Corvair installations (if there are any) just to see if they've worked, because then you wouldn't have to invent a downdraft cooling system for a Varieze.

But since I am aware of who you are and read a lot of the things you have written, I'll admit to having not a lot to back that up and am perfectly willing to go back and do more research/ listen to others.
Eh - please don't pay attention to what I say because of "who I am", whatever that means. Pay attention to it (or don't) because it makes sense and is supported by evidence and facts (or not). But thanks.

#### Marc Zeitlin

##### Exalted Grand Poobah
Yes I read that, and I had a V-EZ flyer explain to me what to look for with the wing attach fittings.
Did the Varieze flyer explain to you that it's impossible to inspect the areas of the wing attach fittings that have failed in flight or have been found to have massive corrosion issues, even while the areas of the wing attach fittings that are visible look perfectly fine? I have seen the one that failed in flight, and have another with extreme corrosion that had eaten away 1/2 - 2/3 of the thickness of the attach fitting, and left the rest looking like crap, but would have been completely invisible from the exterior.

This is the single biggest issue with Variezes - you can't inspect the wing attach fittings, so understanding the provenance of the airplane - where did it live its life - how was it cared for - was it hangared 100% of the time - did it live on the coast or in a dry place, etc., is critical. The 2.5G limit was an inadequate stopgap measure that became permanent - it's completely unnecessary for aircraft that have no corrosion, and it's completely inadequate for those that do.

This is the note I put into any Condition Inspection Residual List Report that I provide for any Varieze on which I perform a CI:

Safety Related Residual Items:

Both Wing Attach Fittings (ALL VARIEZES) - Due to the inherent design from RAF, it is not possible to check for internal corrosion of wing attach fittings. I recommend removing wings at alternate CI's and checking externally for corrosion, with the understanding that without ~40 - 100 hours of disassembly/reassembly, a full inspection of the fittings and full confidence in the condition of the fittings is not possible. Plan on wing removal for more extensive examination at the 20XX CI. Obey RAF's +2.5G / -1.5G limits.​

#### dwalker

##### Well-Known Member
Did the Varieze flyer explain to you that it's impossible to inspect the areas of the wing attach fittings that have failed in flight or have been found to have massive corrosion issues, even while the areas of the wing attach fittings that are visible look perfectly fine? I have seen the one that failed in flight, and have another with extreme corrosion that had eaten away 1/2 - 2/3 of the thickness of the attach fitting, and left the rest looking like crap, but would have been completely invisible from the exterior.

This is the single biggest issue with Variezes - you can't inspect the wing attach fittings, so understanding the provenance of the airplane - where did it live its life - how was it cared for - was it hangared 100% of the time - did it live on the coast or in a dry place, etc., is critical. The 2.5G limit was an inadequate stopgap measure that became permanent - it's completely unnecessary for aircraft that have no corrosion, and it's completely inadequate for those that do.

This is the note I put into any Condition Inspection Residual List Report that I provide for any Varieze on which I perform a CI:

Safety Related Residual Items:

Both Wing Attach Fittings (ALL VARIEZES) - Due to the inherent design from RAF, it is not possible to check for internal corrosion of wing attach fittings. I recommend removing wings at alternate CI's and checking externally for corrosion, with the understanding that without ~40 - 100 hours of disassembly/reassembly, a full inspection of the fittings and full confidence in the condition of the fittings is not possible. Plan on wing removal for more extensive examination at the 20XX CI. Obey RAF's +2.5G / -1.5G limits.​
That's pretty much what he told me, and I checked very carefully for corrosion. The fuselage side is in good condition, but the wings are suspect imo, as they were stored outside for a time separate from the fuselage. I'm very tempted to build a new set of wings to be honest.

#### dwalker

##### Well-Known Member
Bernie Pietenpol used the stock corvair car fan and shroud, but most modern installations mimic the successful baffling used in certified Lycoming and Continental installations. The fan is mounted on a heavy cast aluminum bearing boss that doubles as the top cover plate of the engine. It adds some 8-10 inches of height to the engine. The fan is magnesium and lightweight, but it would also require you to retain the fan belt pulley bracket, AND risk damaging components and lines near the firewall in the event of a belt break. WW recommends against using it unless you’re doing a Pietenpol replica. Although it probably would draw more cooling air into the pusher cowling.

The Corvair heads have a lot of fin area, but I don’t have data on how it compares to a Conti or Lyc. Imagine though, having an air cooled engine that needs to survive idling in LA freeways and has a never exceed CHT of 575F.

Does Bill’s EFI completely do away with the rear distributor drive?

Outside the box, have you considered an O-200D?
I'll answer this in detail when I'm back at an actual keyboard.

#### Marc Zeitlin

##### Exalted Grand Poobah
That's pretty much what he told me, and I checked very carefully for corrosion. The fuselage side is in good condition, but the wings are suspect imo, as they were stored outside for a time separate from the fuselage. I'm very tempted to build a new set of wings to be honest.
That's all well and good, as a new set of attach fittings can be alodined and fasteners wet installed to protect from corrosion. But it doesn't address the other side of the equation, which is the attach fittings on the end of the main spar... Less likely to be corroded, if the corrosion came from separate storage, particularly outside, but who knows. As I said, just because they LOOK OK from the outside is not proof that they are. By the time you get through with the work of replacing the spar, you have to ask yourself, even if you got the plane for free, what the freaking point of all that work is, when getting a Long-EZ eliminates 100% of the safety concerns.

I like Variezes, and I've flown them, and those that own and fly them love them, but personally, I'd hate to have "wing attach fitting corrosion" running around the back of my head anytime I got in the thing to go somewhere... I have a hard enough time, when I've climbed to 10.5K ft, thinking "did I tighten the canard attach bolts last time I took the canard off?" .

#### dwalker

##### Well-Known Member
That's all well and good, as a new set of attach fittings can be alodined and fasteners wet installed to protect from corrosion. But it doesn't address the other side of the equation, which is the attach fittings on the end of the main spar... Less likely to be corroded, if the corrosion came from separate storage, particularly outside, but who knows. As I said, just because they LOOK OK from the outside is not proof that they are. By the time you get through with the work of replacing the spar, you have to ask yourself, even if you got the plane for free, what the freaking point of all that work is, when getting a Long-EZ eliminates 100% of the safety concerns.

I like Variezes, and I've flown them, and those that own and fly them love them, but personally, I'd hate to have "wing attach fitting corrosion" running around the back of my head anytime I got in the thing to go somewhere... I have a hard enough time, when I've climbed to 10.5K ft, thinking "did I tighten the canard attach bolts last time I took the canard off?" .
I'm actually building a Long as well and simply doing the VE as a time filler while I'm working through the Long. The Long is at the fuse on wheels stage, so it's got a bit to go.

#### dwalker

##### Well-Known Member
Does Bill’s EFI completely do away with the rear distributor drive?

Outside the box, have you considered an O-200D?
I am not using Bills EFI. so I do not know honestly,

I am using a coil-per-plug system with crank and ref pulled from two locations- a set of sensors in a modified distributor, and a set of toothed" wheels incorporated into the "front pulley". There are people who are smarter than me that think the redundant Synch/Ref setup is silly and not needed, but it costs little and provides some measure of mental security.

I honestly bounce back and forth between wanting an "airplane engine" and just wanting something more modern that will actually work in a way I understand and am used to. At this point I am fairly annoyed with "airplane engines" and while I am still very likely to acquire an 0-235 or 0-200 at some point and have it ready to swap onto the airframe, it is a back burner item for two reasons.
First. I want this thing to fly sooner than later. There is literally NO WAY I am getting in front of a used aircraft engine, no way, no how. That means finding a suitable core, tearing it down, and going through it as my A&P has time to spend with me on it, as I cannot certify anything about the engine. That will take an indeterminate amount of time and money in addition to all the other things that need to be done. The Corvair engine is simple, easy, and no one needs to sign off on anything. I have had several leads pop up on potential engines, but even the "removed flying in great condition" engines are nothing more than cores to me, until they have been gone through completely.
Now you are about to say- "But you do not have to certify an engine in an Experimental Vari-Eze". Yeap I don't. This leads to item two-
Second, at some point, assuming it IS a good aircraft and does what it is meant to do in a proper fashion, when the Long-Ez is done I am very likely to sell this aircraft and more than likely most buyers will want an "airplane engine" behind them. If I have an aircraft with a certified zero time 0-200/0-235, signed off on, I feel like that will appeal to a greater number of flyers than a Corvair with a few hundred hours on it hanging off the back. Even if I choose not to sell it, there is no reason not to have a spare engine.

#### rv7charlie

##### Well-Known Member
It makes perfect sense to get assistance with an unfamiliar engine, especially a/c engines that are stupid simple yet have dozens of ways to 'bite' if you don't know all the required secret handshakes when overhauling them.
But once it goes on an exp a/c, and especially, once it runs with a prop that wasn't actually certified to run on that particular model and dash-number engine, then it's no longer 'certified' until it's removed and you convince an IA to sign the logbook that it again meets its type cert (which almost always means another overhaul, unless the IA doesn't value his license very highly). A lot of FSDOs, including mine, used to take the engine's data plate when they did the initial inspection on a new homebuilt, so it could never be installed on a type-cert a/c. HQ made them stop that, because it made it much more difficult for owners to determine whether they were at safety risk when a new AD was issued on a particular series of engines.

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#### Victor Bravo

##### Well-Known Member
HBA Supporter
Back on to the subject of the Yamaha engine for a moment...

I believe there is a significant additional benefit to putting effort into this engine for the VE, assuming the weight issues can be handled adequately.

The engine placement and the cowling and the cooling system of the EZ style canards creates some unusual drag and airflow issues concerning the propeller inflow and outflow. The size and shape of the cowling at the rear, and the shape of the cowling to clear the cylinder heads, causes problems in my opinion. The EZ style pusher canards have a distinct sound, which is caused by the dirty and separated air flowing around the cowling and out of the cooling plenum, and the propeller trying to beat its way through all that jumbled up airflow. It's the same reason the Cessna Skymaster, Republic Seabee, and a few other airplanes make this horrifying slapping grinding sound.

Now imagine you were able to install the Yamaha engine which would not need such a large cowling, and may very well be able to use an engine cowling that follows the contour of the upper and lower wing roots all the way to a trailing edge like the rest of the wing. No Olympic size ski jump in the cowling in front of the cylinders. No tennis court sized hole at the back of the cowl that takes up half or a third of the propeller disc area.

Now imagine that the cooling system and radiator could be shaped and streamlined under the fuselage, far enough forward and able to re-accelerate the air to ambient velocity so the airflow into the propeller was minimally affected.

You would have lower drag, higher thrust, better propeller efficiency, and lower noise - than a four cylinder opposed "boxer" engine. On a fast, clean design like the EZ, my semi-educated guess is it would add up to something significant.

#### Map

##### Well-Known Member
I have worked on the engine cooling for 2 pusher installations and have done 2 updraft cooling systems and a lot of downdraft cooling systems.
I learned that the selection of up-vs downdraft needs to be based on the installation requirements. Either can work equally well in flight if it is done right.
One of the main problems for pushers is the lack of prop wash for ground cooling. The suction from the prop behind the engine does not extend far enough forward to help draw hot air from the cowling. Updraft cooling helps here because hot air moves up on its own, or use a fan. The other pusher problem is the wake of the fuselage it lives in, making it harder to get full air pressure into the inlets unless they are raised out of the wake or are made larger than for a tractor installation.
I use updraft cooling on my motorglider (VW engine, tractor) which works well.
I have an extensive chapter on engine cooling in my book "Efficient Powerplant Installation" (see caro-engineering.com).

#### dwalker

##### Well-Known Member
I have worked on the engine cooling for 2 pusher installations and have done 2 updraft cooling systems and a lot of downdraft cooling systems.
I learned that the selection of up-vs downdraft needs to be based on the installation requirements. Either can work equally well in flight if it is done right.
One of the main problems for pushers is the lack of prop wash for ground cooling. The suction from the prop behind the engine does not extend far enough forward to help draw hot air from the cowling. Updraft cooling helps here because hot air moves up on its own, or use a fan. The other pusher problem is the wake of the fuselage it lives in, making it harder to get full air pressure into the inlets unless they are raised out of the wake or are made larger than for a tractor installation.
I use updraft cooling on my motorglider (VW engine, tractor) which works well.
I have an extensive chapter on engine cooling in my book "Efficient Powerplant Installation" (see caro-engineering.com).
This fellow has some solid information- Downdraft Design