certificated engine on Sonex

[Arjay]

Anyone ever considered putting a U. S. certificated engine, like a continental 0-200, on a Sonex? Would like to hear ideas about it.

Ron

[Bryan Cotton]

Ron, have you seen these threads?
viewtopic.php?f=9&t=2758

viewtopic.php?f=9&t=105

From the second thread:

One thing, a major thing, that nobody has brought up in this conversation is the propeller. Even if the engine was the right weight (it's not) and the right physical size (it's not, especially for a Onex), and if you didn't have to engineer an engine mount for it (which you do), you still need to consider ground clearance for the propeller. An O-200, or a C-90 (or even an A-65) produce their power and torque in the range of about 2300 to 2700 rpm. In order to make that power at that rpm useable, the engine needs to swing a 72 to 74 inch propeller. That's 20 inches (!) longer than the 54 inch props typically used on the AeroVee or Jabiru. That means the prop is 10 inches longer on each blade. That would put the prop tip about 2 inches from the ground on a Onex or 4 inches from the ground on a Sonex TAILWHEEL airplane, and closer on a tri-gear. And that's on an empty airplane, sitting still in the hangar. Put some weight in the plane and start taxiing and see how long you make it before you catch a prop tip on the ground. And don't forget to take off and land ONLY in 3-point attitude, lest you hit the runway with the prop.

Sure, you can run a shorter prop, but now you have to turn up the rpm in order to get the performance. Yes, the O-200 can turn more than 2700 rpm, but running constantly at higher rpm will shorten the life of the engine accordingly. And when you do need to top or overhaul the engine, think about the cost. One cylinder assembly for an O-200 costs about as much as EVERYTHING you need to overhaul an AeroVee. Two cylinder assemblies for an O-200 cost more than as EVERYTHING you'd need to overhaul a Jabiru 3300. And you'll be totally on your own in figuring out just what prop will work, which will probably entail buying and trying several propellers before finding the right one. Don't forget to add that to the cost of engineering your installation.

There are a number of engines that can be engineered to fit the Sonex or Onex. But for many reasons that have been outlined in this thread by myself and others, I truly do not believe that the O-200 is among them.

As always, your mileage may vary.

[Area 51%]

The person that bought my Waiex has an O-200 mounted where the Aerovee used to be. I don't believe it's back in the air yet.
I forget the exact numbers, but I believe he had a prop made with more than 60" of pitch to make up for the lack of diameter.

[GraemeSmith]

You could always consider 3 blades with less diameter to solve the issue of ground clearance while still making the power useful. But smaller 3 blade propellers are not grown on trees....

[daleandee]

Plenty of debate on prop sizes and I'm really not a prop guy by any means but I'll toss in my nickel for what it's worth.

I see the mention of 74" props on the O-200 but a C-150 uses a 69" prop. Some, with a desire for more RPM for more power have utilized a 67" prop (experimental).

A faster airframe can use a smaller prop very well. My 3.0 Corvair uses a two blade 54" prop but is has a tremendous amount of blade area. Graeme mentioned a three blade prop and that is certainly an option. Where there is a will there is a way ...

As for the FWF weight debate I've given my thoughts on this years ago: viewtopic.php?f=9&t=4273

Still the factory warning must be respected and there is a limit to the "experimentation" that can/should be done to these airframes.

Dale
3.0 Corvair/Sonex
Tailwheel

[OneTallShort]

I see you said "American", but don't Jabaru and Rotax both make "certified" (ASTM) engines with approved installations on Sonex aircraft? I can't image any manufacturer will ever build a new light aircraft engine to the old FAR certified standard...
To put this anouther way. Are you really going to be safer behind a old "reliable" engine that is not designed for the aircraft with tons of custom work to make it fit vs. using what has been time tested by multiple installations?
If you look at the statistics, it's the systems around the engine (fuel primarily) that cause a lot of loss of power incidents.

Gregg Short
Sonex-A 715