Sonex-A purchase - What to look for

[daleandee]

He actually had a VW racing shop completely rebuild his AeroVee, resulting in over 100 hp without a turbo, no cooling problems, and smooth running in all conditions.

I personally do not believe such a rebuild is possible with an Aerovee. I'm not doubting what you were told but I am seriously doubting the validity of what you were told. From my limited experience with engines, that claim just isn't possible. I believe if it could be done then Sonex would not have needed to add a turbo.

Revmaster has a larger engine, R-2300 (2331cc, 142.2 cu.in.) that uses their RM-049 heads featuring large fins & hemispherical combustion chambers & they rate it at (82) at 2950rpm continuous. (Takeoff power is rated at 85, at 3350rpm.)

I'd like to be proven incorrect by seeing the actual proof from a certified dyno run without the CHTs going into orbit and the RPMs in a range where our small prop size would still be efficient.

Best,

Dale
3.0 Corvair/Tailwheel

[Bryan Cotton]

I'd be interested to know what prop he runs and what RPM he sees.

[Hambone]

I'd be interested to know what prop he runs and what RPM he sees.

I don't know, but I can ask him next time I talk to him.

[Hambone]

Well, I'm receiving a huge amount of useful information from Jim Triggs, an EAA Flight Advisor with over 14,000 hours flying time. What he doesn't know isn't worth knowing! He built and flies an RV-7 and a Xenos. He connected me with a past student of his who built his AeroVee Sonex while in high school, and now has over 1,200 hours in it! He's a wealth of information, too.

A common theme from both of them which concerns me is all of the attention that apparently has to paid to minimizing time on the ground with the engine running to avoid overheating issues. I've never flown an airplane where that was a concern. Some of the advice, like avoiding tower-controlled airfields that require takeoff clearance that could necessitate a lengthy wait on the ground, is new to me, as is considering landing halfway down a long runway if the fuel pump is near the departure end, to avoid a lengthy taxi to the pump. Lots of considerations I have never experienced, but if overheating during ground operations is an issue, I guess it makes sense.

[Bryan Cotton]

For what it is worth, I've only had real temperature issues once. Heat of the summer, and two-up pattern work. Otherwise I don't worry about ground ops at all.

[MichaelFarley56]

I agree with Bryan. Once the AeroVee is broken in, overheating on the ground tends to be a very rare event. The Jabiru 3300 is much more prone to cylinder head temps during prolonged idle than the AeroVee is. Unless it's an unusually hot day or you're idling way over 1000-1200 rpm for some reason, you shouldn't have any issues.
When I had the AeroVee on my Waiex there were many days when outside air temps were 30-50F degrees and I'd have to idle for 15-20 minutes to get the oil warm enough to perform a takeoff!

I'm thrilled you found a Flight Advisor and other knowledgeable people to talk to about the airplane. I wish you the best of luck and safe travels! Let us all know if and how we can be of service!

[Murray Parr]

He actually had a VW racing shop completely rebuild his AeroVee, resulting in over 100 hp without a turbo, no cooling problems, and smooth running in all conditions.

I personally do not believe such a rebuild is possible with an Aerovee. I'm not doubting what you were told but I am seriously doubting the validity of what you were told. From my limited experience with engines, that claim just isn't possible. I believe if it could be done then Sonex would not have needed to add a turbo.

Revmaster has a larger engine, R-2300 (2331cc, 142.2 cu.in.) that uses their RM-049 heads featuring large fins & hemispherical combustion chambers & they rate it at (82) at 2950rpm continuous. (Takeoff power is rated at 85, at 3350rpm.)

I'd like to be proven incorrect by seeing the actual proof from a certified dyno run without the CHTs going into orbit and the RPMs in a range where our small prop size would still be efficient.

Best,

Dale
3.0 Corvair/Tailwheel

It is probably possible given the low compression ratio's we set these to vs what it could be set to.

A few years back, I built a great planes version with the force 1 hub, and it had larger cylinders, I think was 2331cc and the VW racing guru that I was purchasing parts from couldn't understand why I wasn't setting the compression ratio to 11:1 or higher as many of the racing engines are set to. After all, isn't installing a turbo a similar result to boosting compression by increasing pressures in a different way.

[Scott Todd]

100hp doesn't seem like a stretch. Higher compression will quickly get you more horsepower. Dual carbs. Higher RPM. We (and Sonex) choose not to do these things for reliability and longevity. Cooling on the ground shouldn't be an issue. At 700-800 rpm, it just isn't making much heat. My calves give out from holding brakes long before I ever worry about overheating. In my 200 or so hours behind 5 different ones, I've never had an overheating problem. If you have a long wait, just shut it off. Turn the second ignition off, kill the fuel, and wait. A modern radio should only draw an amp or so and sitting like that for 10 minutes won't drain the battery enough to make a difference. When its time, fuel on, ignition 2 on, start. After you've done it a few times, it becomes instinctive.

[Hambone]

It’s great to hear all of the experiences of minimal overheating issues! I’m feeling more confident now.

A real challenge will likely be the enroute weather, especially the seasonal Midwest thunderstorms. I plan on being airborne each morning no later than sunrise, so that should hopefully mitigate some of the weather issues. All part of the fun!

[kmacht]

On the ground the battery has always been a bigger concern than overheating for me. The alternator on the aerovee puts out little to no amperage at idle. It does t really start charging until around 1500-2000 rpm. If you sit too long with the secondary ignition, radios, lights, etc all on you will quickly deplete the battery capacity down.