Viking Engine

[fastj22]

The problem is the Viking forum is controlled with an iron fist by Eggenfelner. He will not allow any post that questions his products or puts him in a bad light.
I think that puts him in a bad light.
Why has he been so evasive on the RV12 weights? You would think that if his weights were comparable or better then an 912ULS, he'd be crowing about it. But he doesn't.
We still don't know the weight and balance of the RV12. And it seems he's lost interest in promoting that aircraft. Wasn't he building one just for the Viking?
Just 6 months ago, the Viking was going to be dominating the RV12 community. Now it barely gets a mention.

It all really comes down to weight to me. The Fit engine is rock solid. His reduction gear seems solid. Even his redundant ECU and fuel system.

With the Sonex, there's not much extra weight those little wings can carry and maintain the flight characteristics Sonex is known for. If he's adding 50 extra lbs, on the nose, that comes out of our useful load in fuel, passengers and baggage and potential dramatically effects the handling of the aircraft.

Color me skeptical. I wish I was more skeptical when I placed my $1000 "refundable" deposit on it back at the 2011 Airventure. But I'm glad that's all I will ever lose. Live and learn.

[fastj22]

Looks like Jan found the solution to the balance issue. By mounting the battery in the furthest aft section of the tail.

http://www.vikingaircraftengines.com/Viking%20Sonex%20installation%20pictures.html

Look at last photos.

[chris]

I have never seen a battery mounted that far aft on a sonex. What kind of issues such as stability could that placement cause?

[fastj22]

I have never seen a battery mounted that far aft on a sonex. What kind of issues such as stability could that placement cause?

Think lawn dart.

[chris]

I have never seen a battery mounted that far aft on a sonex. What kind of issues such as stability could that placement cause?

Think lawn dart.

:lol: That's basically the image I had.

[falvarez]

Some Corvair powered Sonex have had to put the batter far back in the tail (usually due to a lighter pilot)...so this makes me think the Viking will weigh in around what the Corvairs weigh...210 to 220 lbs...but that's just my guess. If I wanted to exceed the recommended FWF weight, I personally would have gone w/ Corvair...10 more HP than Viking and about 5K less.

[chris]

Some Corvair powered Sonex have had to put the batter far back in the tail (usually due to a lighter pilot)...so this makes me think the Viking will weigh in around what the Corvairs weigh...210 to 220 lbs...but that's just my guess. If I wanted to exceed the recommended FWF weight, I personally would have gone w/ Corvair...10 more HP than Viking and about 5K less.

Is the battery in roughly the same spot with corvairs? Do you know of any pics from the corvair?

[falvarez]

Back when I was considering a Corvair for my Sonex, I spoke w/ Dan W (builder of the Cleanex) and he said for my body weight (180 lbs) that I'd want to put the battery in the tail cone just forward of the Horizontal Stabilizer. This would offset the added weight of the engine for solo flights. I believe he said this is where Chris Smith (son of Cleanex) put his battery...Dan's may have been a bit more forward.

I don't have any pics of the install, but I imagine that you could reach out to one of these guys to get some.

[fastj22]

Putting a 15lb battery furthest aft possible in an aircraft is a HUGE indicator that the aircraft is not well balanced for that design.
Now say you want to take advantage of the new LION batteries and save some weight. They produce the same power but only weigh 3 lbs. Now if you have a Viking, you need to not only put that in the aft end, but add 12 lbs of lead ballast to get it to balance properly. And you still have the bonus of having highly energized 8GA power cables running from the tail, through the cockpit and through the firewall.

IMHO, The Viking and O200 are just too heavy to be a good fit to the Sonex airframe. Corvair is marginal. So is the 912ULS.
There is a reason Sonex only supports the Jabiru and VW engines for their aircraft. Some of it is marketing, but truly, most of it is design. The plane simply requires a lighter engine.

Think about the consequences.
Loading an airframe with higher mass on each end of the airframe vs. keeping the mass closer to the CG makes the airframe more sluggish and spongy. It simply takes more energy to change the path. Its more stable when moving in one direction. But stability comes with a price. We sometimes need to change our path. So expect much heavier control inputs and slower response. Aerobatics also become more interesting because once you get that end loaded mass moving it will take a great deal more effort to make it stop. Spins may be unrecoverable.

[radfordc]

Think about the consequences.
Loading an airframe with higher mass on each end of the airframe vs. keeping the mass closer to the CG makes the airframe more sluggish and spongy. It simply takes more energy to change the path. Its more stable when moving in one direction. But stability comes with a price. We sometimes need to change our path. So expect much heavier control inputs and slower response. Aerobatics also become more interesting because once you get that end loaded mass moving it will take a great deal more effort to make it stop. Spins may be unrecoverable.

From what I've heard, the guys with Corvair engines in Sonex's would say your analysis is pretty bogus. There are really only two issues with the Viking engine...does it perform as advertised, and is the manufacture an honest, reliable source of support?