SonexBuilders.net

radfordc wrote:You're assuming the Aerovee Onex will always fly at gross weight....but probably not. I think the numbers will look more like this:

Aerovee/Onex 600, 200 pilot, 60 fuel = 860/80 = 10.75 lb/hp

O-200/Onex 700, 200 pilot, 60 fuel = 960/100 = 9.6 lb/hp

I'll bet the 100 lb lighter plane will fly better.

Based on your theory a Pitts Special with an 0-200 will fly better than one with an 10-360-A which is about the same weight difference as the Onex going from an aerovee to an 0-200.Same airframe on both Pitts, the latter having a higher power to weight ratio.
Power is not the enemy here unless there is not enough of it.Take any airplane with any given HP,overload it and it will fly like a pig.Add 75 more HP and you no longer have a pig.The same holds true with cars. Drive a 6 cylinder Mustang and then drive a Shelby Cobra
Lets agree to disagree and leave it at that.

Since the likelihood of someone building an O-200 Onex is fairly small our disagreement will remain academic. I continue to believe that lower wing loading in a small plane provides better flying qualities than higher power/weight ratio.

Mike53 wrote:Great Andy ,I get knocked down and you come along and give me false hope :? The more I look at the UL260i the more I wish I had a lot of money.

I hear that! :D

radfordc wrote:Since the likelihood of someone building an O-200 Onex is fairly small our disagreement will remain academic. I continue to believe that lower wing loading in a small plane provides better flying qualities than higher power/weight ratio.

I love it when nobody brings a club to a debate.Cheers :D

One thing to keep in mind when adding weight is that when pulling g's that weight gets multiplied. Lets say that the 0-200 weighs 50lbs more than an aerovee. You go to do a simple loop and fall out the top or somehow screw it up. Suddenly you are pulling out at 5 to 6 g's in a panic to get it back under control. Those 50 lbs are now effectivly an additional 250 to 300lbs of weight on the nose. Are you sure the motor mount and firewall attachment points can support another 300 lbs of weight? Maybe you don't plan on doing aerobatics in your sonex, are you sure the guy you sell it to in a number of years won't? Those 50 lbs don't sound like much but they can add up quickly.

Keith

Alternative engines: The OP suggested an O-200 I was wondering about a C-65 for the following reasons.

There are two Piper Cubs on my field who fly regularly and never have engine problems, or problems hand propping.

There are six VW powered airplanes on the field and they never fly (including two Monnett designs). They're always tinkering with their engines, something is usually "off" and two of six have crashed due to engine problems. I'm not a fan of the VW because of these experiences.

Meanwhile the C-65 Cubs have a grand time with no reliability issues.

There are also two ultralight trainers here with HKS 700e engines, and they have been reliable as well in a hard duty training environment, about 3,000 hours between the two with no failures and just routine maintenance.

You'll get lots of different opinions on the AeroVee, but they have been around long enough to be a known quantity. I fly behind one and got into it knowing it took a bit more maintenance than a certified engine with the trade off of lower costs. I do not have enough time on mine to debate the "always tinkering" part, and have to say the two of six having crashed is a skewed assessment of the engine as a whole. Either way, the engine is reliable or there is no way it would have survived.

In a Sonex, any certified engine may run into weight issues - the airframe just isn't designed for a firewall forward package that heavy.

Can it be done? Yes. Should it be? Well, there we go back to the beginning of the discussion again...To each their own. Experimental aviation is different that way.

Mike53 wrote:What I find confusing is the fact that Sonex would design a plane with this type of limitation.Was it just a way to assure the sale of their own engines?

OK everyone can have their own opinion, but let's not go ascribing nasty motives or hidden agendas based on zero information!

I highly recommend you read the book "John Monnett: from Sonerai to Sonex" - it will clarify a lot of things and provide some facts.

Here are a few facts (from that book and from other public sources) about the Sonex and the engine options:

• The Sonex was engineered by Pete Buck, a former Monnett employee who went off and became a respected engineer at the Lockheed-Martin Skunkworks.
• The intent was to make a lightweight, fun-to-fly aircraft.
• Early on (before the Sonex plans were available in the US), there was some business-plan to offer a mostly-built or ready-to-fly aircraft in the European microlight market-segment (similar to our LSA category, but before LSA was officially established by the FAA). We've never learned the whole story about who was involved and possibly investing in the program; but we know the idea was to have the aircraft built in a country with inexpensive low-skill labor. At the time there was a lot of opportunity in Eastern Europe, and several glider & boat manufacturers set up shop in those countries for similar reasons.
• The potential for unskilled assembly-workers helped drive the design towards simplicity and ease-of-building. This turned out to be a boon when the original business/plan was abandoned. The Sonex became an aircraft that was easy to build from plans, out of standard materials.
• The first Sonex prototype was powered by a Jabiru 2200. The Jabiru 2200 and 3300 were seen as low-weight engines offering good performance. The exchange-rate and initial prices on the engines made them attractively-priced in US dollars.
• The new Aerovee was introduced as an option for the Sonex later, after the plans were being sold and Jab engines started to shoot upward in price (due to both pricing adjustments and changing exchange-rates).

Its easy to see that the Sonex was not designed at all around selling the Aerovee engine. If anything, the Aerovee was resurrected (from earlier Monnett ventures), updated, and re-introduced as a complimentary product specifically as a counter to the rising costs of the Jabiru engines**.

One last note on weight: Remember that you're going to have to build a custom engine-mount to hold the heavier O-200. So don't just factor in the weight of the engine - also factor in the weight of the mount (relative to the stock engine-mount). Then think about how your CG is affected by cantilevering that extra weight out in front of the aircraft.

One last note on the O-200: Are you prepared to figure out all of the firewall-forward systems and components on your own? Unlike a Jab or an Aerovee, you're going to be doing something that few - if any - people have done. So there will be no one to ask "how did you do this?", no aircraft to compare yours to, and no factory support to fall back on. How much extra time and money will you sink into wiring & ignition systems, carburation/injection, cooling & baffling, custom exhaust piping, fuel delivery, a custom cowling, etc??? Maybe you're prepared for such an experience and relish the extra development, testing, tuning, and iteration that would be required... But if not, you need to consider all of these things before you jump into it. Someone on the thread mentioned seeing some Aerovee-equipped aircraft being worked-on frequently - I think the same thing is going to happen (and perhaps to a far greater degree) if you use an unusual engine and have to come up with custom solutions for every FWF system!

Take care,

--Noel
Sonex #1339
Center-stick, TD, Flush (pulled) Rivets, Aerovee Turbo, Acro-ailerons
Wings & Empennage complete

**NOTE: I'm not trying to claim the Monnetts are angels - they're a business (and have every right to make a reasonable profit). Re-introducing the Aerovee gave them another revenue source and it helps keep the cost of a Sonex well below the range of an RV aircraft. It also helps keep the Sonex at a cost which is comparable to many used aircraft (whereas it would be a less-attractive offering if it was much-more-expensive than a simply-equipped used Cessna or Piper).

Sonex1517 wrote:You'll get lots of different opinions on the AeroVee, but they have been around long enough to be a known quantity. I fly behind one and got into it knowing it took a bit more maintenance than a certified engine with the trade off of lower costs. I do not have enough time on mine to debate the "always tinkering" part, and have to say the two of six having crashed is a skewed assessment of the engine as a whole. Either way, the engine is reliable or there is no way it would have survived.

In a Sonex, any certified engine may run into weight issues - the airframe just isn't designed for a firewall forward package that heavy.

Can it be done? Yes. Should it be? Well, there we go back to the beginning of the discussion again...To each their own. Experimental aviation is different that way.

*****************
Will get a lot of different opinions on the old A65 continentals too. The one in my old Luscombe 30 years ago would most always always start on first pull (No starter) . -- When cold. Only found one way to get it started when hot, ---- Let it cool off. (no impulse mag.) Also recall replacing a jug or two on the 0-200 in the C150 that followed it. So far my CAMit 3300 is doing great.

David A. Sonex TD #1327

Hang on,
Personally I would not put an O-200 on a Sonex, it goes against the whole philosophy.

That said, the main objection in this thread seems to be weight, now Wikipedia lists the dry weight of the O-200-A at 170.18 lbs without accessories:
https://en.wikipedia.org/wiki/Continental_O-200
As I understand, the only real hard constraint Sonex has ever put on the weight of the engine is that you need to keep the total weight of the FWF package below 200 lbs.
(Although there are those who have proven this hard constraint is not that hard after all, especially the CorvAir & Viking people no doubt)

Anyway, with a little creativity like using a lightweight lithium battery, using an TBI, ..., wouldn't you still be able to keep a O-200 FWF package below 200lbs, thus remain within the Sonex set air-frame limitations?