Converting to a 912

17 posts in this topic

Posted

After many years of great performance from my Subie I decided to try to get some better performance and lighter weight on the SuberAvid  (think I can cut at least 50 to 60 lbs and gain 15hp with the Zipper kit on the 912), so after getting the Rotax 912 engine as FWF ready as possible; last weekend Leni was gracious enough to let me come stay with him while we built the new exhaust system.  With a little help from me, and mostly Leni using his tubing bender and super TIG welding skills, we got that final puzzle piece done and it was time to do the switch.  Starting last week and this weekend I got the Subie off and after some work on the firewall to move cabin heat ducts and pos. and neg. terminals (it seems time everything fell directly in line with the new engine mount tubing).  The Rotax 912 got bolted to the firewall (this is another testimony to Leni's fabrication and welding skills.  I had made a firewall mockup for the Subie when I was building the plane so it came in handy to use for the firewall side of the new engine mount Leni made for the Rotax.

When deciding where to position the engine we discovered that my Subie engine mount had a 6.5 degree down angle,which is extreme and now makes sense that even though my plane handled great is always seemed to be flying tail low in pictures.  The new engine mount has 1.5 degree down angle which is a more normal position, but I added shims to set it at 0 degree thrust line to try for best takeoff performance.  The Rotax is also positioned 4" further forward than the Subaru to try to keep the W&B similar. The mount is 3" forward with an additional 1" of shims so I can move it back if I need to once we do the W&B.  I want to keep it right at the forward limit when it is unloaded so I don't have to worry about rear CG when I load it heavy for hunting.

Still have a ways to go in getting it all hooked up but it is going good so far.  I can sure appreciate you guys doing the Yamaha's; a lot of fabrication work, trial and error involved in getting those all working.

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Posted

Very nice work and the work space looks great too.

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Posted

I like the addition of the stabilizer tube for the stinger.

 

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Posted

Looks great Fellas!! Cant wait to hear what you think about about the swap.

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Posted

Thanks for noting the need for a brace on the stinger Larry, we added it because of that.

Yes, nice hangar isn't it! My buddy is letting me use it for the swap since it is heated and mine isn't.  Nothing like having good friends!

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Posted

Can't wait for the flight reports mr!  I think with the thrust line issue fixed and the lighter weight it should be a completely different bird!  I am still shaking my head over the down thrust they had built into the subie mount.

:BC:

 

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Posted

Wow is all i can say at moment!!! Damm nice work guys, that will b so sweet, Leni, even the wife said "Damm thats nice!"  

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Posted

Looks good Randy, my soob mount had the same problem with the downward thrust, never did get it flying straight always had that tail low attitude and always needed back pressure on the stick. It will feel like a different plain for sure now that you corrected the thrust line like Leni says

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Posted

Well, I think I have it ready to fire up now; at least I sure hope nothing smokes when I pull the trigger.  We will see if I wired it right.  Still need to contact MGL to find out how to hook up the Rotax CHT sensors where I had thermocouples on my Subie.  The cowling is a bit odd looking with the 4inch aluminum spacer; kind of makes it look like it has a roman nose, but it will have to do until I can figure out a new cowl (does anyone have a MK IV cowl for sale?).

It definitely is more difficult to see over the nose now with the extension and the zero thrust line so I will have to get used to that.  Can't wait to be flying again soon!

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Posted

She's still a beauty, Randy!

 

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Posted

Thanks Larry!

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Posted

That looks SWEET! And you beat Joey by a mile. I think his conversion project is still flying the 582! (Sorry Joey :-)

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Posted

So did the W&B; weight is 64 lbs less and by moving the engine forward 4" the empty CG changed from 9.17 with the Subie to 9.45 with the Rotax; almost exactly the same which is what I wanted. It is easy to get to the forward CG limit with just my emergency gear in the rear of the cargo area and I can continue to load it heavy in the cargo area and not worry about exceeding the aft CG limit.

I fired the engine up today and it started and ran great, but my oil temp and water temp gauges were not reading correctly and I was not able to get it up to good operating temp since it was -14 degrees, so didn't fly it.  Need to block off the oil cooler and part of the radiator and close up about 1/2 of my cowl opening area and build a heat muff for the exhaust to get some heat in the cabin.  Hope to fly it next weekend!

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Posted

I see the oil cooler on the belly and the coolant radiator on the front of the engine. 

The oil cooler can probably be completely taped over in the winter, or make a sheet metal cover that can be attached with a shutter on it.

Where is the coolant radiator getting it's airflow from?  The large cheek openings?  What about the baffling on the radiator? Is there a duct attached to it?

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Posted

That is one badass looking plane. Does it derive from a Magnum??

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Posted

Oh and when can we expect a name change?? :BC:

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Posted

I plan to block off about 4" height in the middle of the cheek openings and deflect air from the lower part of the cheek openings into the radiator.  I will cover the oil cooler with aluminum tape; makes it easy to change to get right amount of covering for the temps.

Ha, ha,..Sorry, I can't bear to change the name.

I'm not sure how the fuselage compares to the Magnum but it is 18" longer and 6" wider than the Avid MK IV and has a much larger tail.  The new wings are the same dimensions as the Magnum wings. It really gives you a lot of room for packing gear; 6 feet from the seat truss to the back of the baggage and all open and useable space.  I have popped out the passenger seat and slept in it before.

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