Why not Rotax

[gcm52]

I installed an 80hp Rotax 912 in a Zenith 701 and I thought it was a very nice engine. Reliable, smooth, light weight and fuel effecient. I am now starting a Onex and am thinking about engines. A Rotax 100hp 912 and a 120hp Camit are both interesting options, but I have a while before I need to make the engine decision. Maybe there will be a hydrogen fusion engine available by that time.

[fastj22]

I installed an 80hp Rotax 912 in a Zenith 701 and I thought it was a very nice engine. Reliable, smooth, light weight and fuel effecient. I am now starting a Onex and am thinking about engines. A Rotax 100hp 912 and a 120hp Camit are both interesting options, but I have a while before I need to make the engine decision. Maybe there will be a hydrogen fusion engine available by that time.

There's a new diesel coming online this year at about the same price, weight and power as a 912 that could be a game changer.

[gcm52]

There's a new diesel coming online this year at about the same price, weight and power as a 912 that could be a game changer.

Who is the vendor/manufacturer for that diesel??

[NWade]

Its important to keep in mind that the cost & complexity arguments don't just apply to the initial purchase & installation. You have to think about the ongoing operations, maintenance, and overhaul costs!

Sonex has consistently talked about how inexpensive their airplanes are to operate and maintain. In fact, this is one of their bigger selling-points of the AeroVee: an "overhaul" costs just a few hundred dollars in parts.

How does that stack up to the cost of a Rotax overhaul? ;) And what's the long-term cost of checking and maintaining (and eventually replacing) the radiators and hoses and fittings on any liquid-cooled engine?

Its true that modern-day materials and designs make liquid-cooling more reliable than it used to be, just as modern electronics are more reliable than they used to be. But every item you put in an aircraft will eventually wear out and cost you money.

Sonex's factory-supported configurations are intended to hit a spot on the price/performance curve that's just below the point where diminishing returns really kick in. Folks can certainly push beyond that spot, and they may even get better-performing airplanes as a result. But the question is: How much money and maintenance are you willing to deal with, in order to save a few pounds or go just a few knots faster?

Lastly, remember that - no matter how much you tweak it - a Sonex is never going to have the legs of an RV, the aerobatic capabilities of a Christen Eagle, or the climb performance of a CarbonCub. Its a good all-around airplane for local flying, some cross-country journeys (if you accept frequent stops and a light baggage load), and some mild aerobatic fun. And being able to do all of these at a low cost is a great achievement! But dumping an extra $5k - $20k into this airframe will not transform it into something that it isn't.

My 2 cents,
--Noel
Sonex #1339
Wings & Empennage complete, Fuselage build underway
AeroVee Turbo, Center-Stick, TD, Acro-Ailerons, All-Flush Rivets

[gcm52]

Some folks want economy above all else, some folks are willing to spend more to get a different mix of features in an engine. It is a very personal decision. Yes, a Rotax overhaul is going to be more expensive, but the TBO is 2000 hours. So is it better to spend $800 for a VW overhaul at 600 hours or $10,000 on a Rotax overhaul at 2000 hours. Different folks will answer this question differently. That is why I think it is smarter for a kit manufacturer to support more engines. You will sell more kits.

[NWade]

That is why I think it is smarter for a kit manufacturer to support more engines. You will sell more kits.

Except this ignores the fact that supporting more engines means:
1) A lot more work, on their part; and
2) Possibly more liability, if something happens to a Sonex in a "supported" configuration

Everything in aviation is a trade-off.... everything! :-P My hunch is that Sonex has done the math and decided that the incremental sales doesn't justify the work; and that people who are big Rotax fans will install the engine regardless of whether the factory supplies a "supported" solution or not.

--Noel

[fastj22]

There's a new diesel coming online this year at about the same price, weight and power as a 912 that could be a game changer.

Who is the vendor/manufacturer for that diesel??

viewtopic.php?f=9&t=1954

[gcm52]

Except this ignores the fact that supporting more engines means:
1) A lot more work, on their part; and
2) Possibly more liability, if something happens to a Sonex in a "supported" configuration

I agree that this is more of a business philosophy question. An example of a kit manufacturer that supports a lot of engines is Zenith. For my first build I wanted the engine that I wanted, plus I wanted a FWF kit to support it. That led me to Zenith. Sonex has a different philosphy, focusing on the Aerovee. For my second build (Onex) I feel I can handle the custom FWF for a different engine, if I decide to go that route, in fact I think it would be fun to do. I agree it is more work for a kit manufacturer to support more engines, but my feeling is there would be a return on investment by having more kit sales. I think the engine manufacturers will sometimes do some of the work to develop the FWF kits as well.

As far as liability goes, kit manufacturers protect themselves pretty well with their waivers and the fact that the aircraft is not manufactured by them. But I think there is more liability risk by supplying the engine and the kit versus just supplying the kit and having Rotax or Jabiru supplying the engine. In the latter case the liability would be shared by Rotax or Jab. However I think it is a moot point as the liability is assumed by the kit builder for the most part.

[gcm52]

There's a new diesel coming online this year at about the same price, weight and power as a 912 that could be a game changer.

Who is the vendor/manufacturer for that diesel??

viewtopic.php?f=9&t=1954

Thanks! That looks interesting.

[fastj22]

If Sonex didn't offer the Aerovee, you bet they would support a lot more engine options. Now that the Turbo is getting some traction, I would anticipate Jabiru being dropped from support. Doesn't mean you can't put another engine on your Sonex, just don't expect firewall forward tech support for it.