SonexBuilders.net

I'm still researching Sonex aircraft kits, and recently had a chance to take a look at a Onex in person. Due to my height, a Onex might be my only choice. This particular Onex had a stock "80hp" Aerovee engine hanging on the front of it. The pilot weighs around 160lbs and related to me that the Aerovee MAYBE gets 80hp wide open, and that it seems to lack power, even with a 160lb pilot and in a such a small and lightweight aircraft.

I know that the Aerovee turbo advertises 100hp, but even with the taildragger configuration, it seems like a really really tight fit against the firewall. Also, Ive been reading about post flight overheating with the turbo, and now it also requires a cooling radiator, fan, and coolant can. More stuff to try and cram next to the firewall.

Does anyone have any experience, advice, or recommendations in regards to the Aerovee turbo on a Onex? I've also been looking at 85hp Revmaster 2300, Hummel, Great Plains. Thoughts on these engines?

If Sonex made an engine mount for a Rotax 912 on the Onex it would be a no-brainer for me. I'm trying to keep things simple as possible, so not interested in having a custom engine mount made.

I'm awaiting an airworthiness inspection on my Onex turbo with the water cooling additions. It is a tri-gear which compounds the firewall space problem. I would not recommend that combination. The turbo and accessories eat up a lot of space behind the engine.
It really cramps the engine compartment and there is little to no room to get to the rear of the engine. If I were to do it again I would likely choose a UL, Jabiru or Rotax and have someone build a mount to get 100 HP or better. I started putting the engine together a few years ago and didn't want to tackle the custom engine mount engineering myself but I think these days there are people who have used these engines who would build and sell you a mount. One additional caution, my trigear, turbo Onex is not exactly light weight at 653 pounds. Obviously the nose gear and turbo add weight but that is also with an EarthX battery versus an Odyssey for weight reduction. The wing fold mechanism in the Onex is steel and that adds weight so they are heavier than you might initially imagine.

Tom Jones
Onex 0133
Aerovee Turbo

Hi Tom,
Great to hear your close to a/w inspection! yes the onex is not much lighter than a sonex. more hp is always good!
I think a few motor mount options would sell many more onex kits.
hope to see your plane at osh airventure 2021!


best,

WaiexN143NM
Michael

I contacted ULpower and it turns out they do make an engine mount for the Onex. I will most likely be putting a UL 260is on my Onex (107hp). It weighs right around the same as a Aerovee and its fuel injected and FADEC engine management. So no choke, mixture, carb heat, etc.

I always felt that the two factory prototypes performed very well with the AeroVee. I never felt like there was a lack of power. Keep it light and you can't get more performance for the dollar! If I were to build one, I'd go with the AeroVee.

Has anyone actually asked Sonex if they will make a Onex mount for a 912? I was planning to make my own, so I never asked, and also haven't started on the mount yet. Based on the price of the mounts they make for the Sonex model, it wouldn't be cheap though.

Rusty

I have never felt the need for more HP with the Aerovee in my Onex. The plane performs to its design parameters. If you want to exceed the design that's up to you. After all we are building experimental airplanes and we are all test pilots in one way or another. But, if you are really considering installing a UL engine in your Onex I'd recommend contacting someone that is or has done it before you. I'm familiar with one that is being built near me and it is not an easy task. There are many extra units that support the "one lever" operation of that engine that are a problem finding space for in the Onex, and something else to think about, it is totally dependent on the battery to operate. A back up is necessary. I think the Onex I'm talking about is the first or second one in the U.S. I'm not bad mouthing the engine. It is a great, automated operation, factory built and tested, expensive engine. But putting it in a Onex is not easy. 300 hours on my Aerovee and flying.

Does the UL use the stock Aerovee cowling? I can’t find a reference on the Sonex website