Corvair Engines - The Justification Series

[Gordon]

Regarding Dales Many Comments......

Gezz Dale............calm down my man..........your getting a "bit intense"....approaching "a rant" even.

Just kidding.......to be clear, you have made some good points.....so I am not going to add to the "mix".

Evidently some folks don't agree........and that's fine. With all the information flowing from different points of view there are always a few "nuggets" in there that we can all learn from.

Your "Corvair Justification Series" is just fine with me.

Gordon........Onex.....Hummel 2400

[vigilant104]

Dale,
As you note, the Sonex LLC acrobatic max weight is given as 950 lbs, and you presumably take no exception to that as being appropriate. That already takes into account whatever the wings weigh. If we are flying acro and have a 180 lb pilot (that's with clothes, headset, etc) and just 50 lbs of fuel, our maximum empty weight will be 950-180-50 = 720. So, if we build a plane that weighs more than about 720 lbs empty (regardless of engine type, etc), it is, for practical purposes, incapable of safe flight at +6/-3Gs (the FAA standard for the acrobatic category).
Unless somebody can/has built a Cleanex with an empty weight of less than 720 lbs, all of them are and will be non-aerobatic, right?
That's fine, I know you mentioned that you didn't fly acro in yours. Lots of people enjoy their Thatcher CX4s, Cessna 152s, RV-12s, etc and never miss flying acro. But if mounting a Corvair means that acro is off the table, then we should just specifically note that as we press ahead.

[rizzz]

Dale,
As you note, the Sonex LLC acrobatic max weight is given as 950 lbs, and you presumably take no exception to that as being appropriate. That already takes into account whatever the wings weigh. If we are flying acro and have a 180 lb pilot (that's with clothes, headset, etc) and just 50 lbs of fuel, our maximum empty weight will be 950-180-50 = 720. So, if we build a plane that weighs more than about 720 lbs empty (regardless of engine type, etc), it is, for practical purposes, incapable of safe flight at +6/-3Gs (the FAA standard for the acrobatic category).
Unless somebody can/has built a Cleanex with an empty weight of less than 720 lbs, all of them are and will be non-aerobatic, right?
That's fine, I know you mentioned that you didn't fly acro in yours. Lots of people enjoy their Thatcher CX4s, Cessna 152s, RV-12s, etc and never miss flying acro. But if mounting a Corvair means that acro is off the table, then we should just specifically note that as we press ahead.

I'm not sure that staying below 720lbs with a Corvair is that unachievable based on my experience:

My Sonex weighs 665lbs empty,
It has a 2.4L VW engine and itcertainly isn't the lightest VW you can build (it has a heavy Bendix dual magneto and a full flow oil filtering system).
My aircraft is also painted, but I've kept everything else as light as possible.

If I had built the exact same aircraft but with a Corvair engine, would that really have increased the weight by more than 55lbs?

[daleandee]

That's fine, I know you mentioned that you didn't fly acro in yours. Lots of people enjoy their Thatcher CX4s, Cessna 152s, RV-12s, etc and never miss flying acro. But if mounting a Corvair means that acro is off the table, then we should just specifically note that as we press ahead.

Hi Mark,

No, I don't fly acro. Dan Weseman did in his but he built a very light polished tail dragger and his empty weight was listed at 699 lbs although I seem to recall that it was revised up a bit later. So in keeping the acro limit at 950 lbs you are correct that the build weight with the Corvair would have to be carefully watched. So while I wouldn't put acro off the table with a Corvair there are two caveats, 1) a light build and 2) a pilot that is somewhere close to an FAA sized guy (< 200 lbs).

Dale Williams
N319WF @ 6J2
Myunn - "daughter of Cleanex"
120 HP - 3.0 Corvair
Tail Wheel - Center Stick
Signature Finish 2200 Paint Job
171.9 hours / Status - Flying
Member # 109 - Florida Sonex Association
Latest video: https://www.youtube.com/watch?v=1VP7UYEqQ-g

[vigilant104]

I'm not sure that staying below 720lbs with a Corvair is that unachievable based on my experience:

My Sonex weighs 665lbs empty,
It has a 2.4L VW engine and itcertainly isn't the lightest VW you can build (it has a heavy Bendix dual magneto and a full flow oil filtering system).
My aircraft is also painted, but I've kept everything else as light as possible.

If I had built the exact same aircraft but with a Corvair engine, would that really have increased the weight by more than 55lbs?

I'm not sure. 55 lbs sounds like a lot, but two more jugs, two larger heads, a longer crank, a case that is long enough for two more cylinders, two additional pistons, conrods, more oil, etc-- is surely going to weigh something.

Scott Casler's site says his 2400cc engines max out at 167 lbs.
Here (https://sonexbuilders.net//viewtopic.php?f=9&t=4273&p=32910&hilit=pounds#p32910 ) Dale cited another builder's Corvair FWF weight as 255 lbs, which is the highest Corvair weight I recall seeing.
255 lbs - 167 lbs (Hummel/Casler) = 88 lbs more. This is almost certainly an apples/oranges comparison.

I thought most of the Corvairs were coming in at about 220 lbs. 220 lbs - 167 lbs (Hummel/Casler) = 53 lbs more. That seems reasonable, and is darn close to the 55bs additional you cited. If that increase is right, then you'd still be okay to fly acro in your present aircraft --if you didn't weigh more than 180 lbs (with clothes and gear) and you don't have more than than 50 lbs of fuel aboard.
In these comparisons, a lot depends on what is included in the weight. Induction?? Exhaust? FWF including engine mount? Oil? At any rate, it is sure that some planes fitted with an Aerovee now will be over the aerobatic weight limit if the same plane and pilot are flying behind a Corvair that weighs 50+pounds more. OTOH, as Dale points out, the difference between the Corvair and some of the other (heavier) engines that Sonex supports will be less.

[samiam]

Dale - Thanks for the series. We need to have this discussion and share the information. Despite quoting me on your opening post, I've resisted posting again until now.

Perhaps the ONLY possible objection that everyone has to the Corvair engine is its weight, and there is very little REAL information available out there on it. All comparisons are very apples to oranges.

I'm building a top-of-the-line Corvair with all lightweight parts. I'm using the billet crank which is about 8 pounds lighter and the 3.0L displacement which is also lighter. When I finish later this year, I plan to weigh it. The "dry weight" of a Camit 3300 is 182 pounds. I don't think the weight difference will be as dramatic as some think. However, until we have these specific numbers, everything else is just conjecture.

As for the whole argument itself: I simply ask myself what the more common risk is in aviation - airplanes falling apart in midair, or their engines failing in midair.

[GordonTurner]

Right on Mike.

My 3.0 with billet crank is sitting in the coffee table in the middle of the living room waiting for the rest of the project to catch up. If i had some way to weigh i would. I’ll think about that one.

Gordon

[WaiexN143NM]

hi all,
just for reference, we weighed our cont. O-200A this am. dry weight, at 200 lbs. slick mags and harness, ms ma3spa carb and carb heat /air box,spin on oil filter, lite wt b&c starter & 30amp alt.
so no motor mount, baffeling,oil, prop, spinner, cowling,oil cooler, battery ,muffler. another 25-30 lbs?
so estimating 230 full up fwf.
this engine we built up for our zenith cruzer.

waiexN143NM
michael

[daleandee]

Dale cited another builder's Corvair FWF weight as 255 lbs, which is the highest Corvair weight I recall seeing.

As many have now commented on the FWF weight and the differences I think I may be able to clarity this a little. My Engine (3.0) was 218 lbs. The newer ones should weigh a little less as the new starter takes off 3 lbs. and the newer billet crank is lighter also. I can't say exactly but 210-212 might be in the ballpark. What Dan was referring to is the real honest FWF weight of the install. That's what I was driving at when I mentioned the Turbo VW motor.

The Jabiru 3300 weighs 180 but the installed weight is 215 lbs. which is 35 lbs higher. If an older Corvair at 220 lbs. is installed the FWF weight would be somewhere about 255 lbs. Newer Corvairs will save about 10 lbs. So what we don't know is the true FWF weight of the Turbo VW motor which includes everything forward of the firewall. It would be helpful to know that number when ALL the parts are put together and weighed. That's what SPA did in order to get real numbers for the Corvair.


Dale Williams
N319WF @ 6J2
Myunn - "daughter of Cleanex"
120 HP - 3.0 Corvair
Tail Wheel - Center Stick
Signature Finish 2200 Paint Job
171.9 hours / Status - Flying
Member # 109 - Florida Sonex Association
Latest video: https://www.youtube.com/watch?v=1VP7UYEqQ-g

[peter anson]

The Jabiru 3300 weighs 180 but the installed weight is 215 lbs. which is 35 lbs higher.

What do you think needs to be added to a 3300 Jab that weighs 35 pounds? The engine weight is quoted with everything except oil which is probably about 7 pounds. I'm pretty sure my oil cooler doesn't weigh 28 pounds. I remember when I did the original weight and balance thinking "Phew, that was close". My Sonex is all painted, but if the engine had been any lighter I would have had to hang weights on the nose. The initial weight was just 666 pounds (bit of help from the devil there).

Peter