UL Power/RV-12 Weight and Balance

[Tim Kern]

Tony, you mention "To cantilever a heavier and more powerful engine off these mounts an additional 12? or so forward of the Rotax position seems cavalier to say the least."

While the ULPower 260iS is more powerful, it isn't heavier, though its more-compact (front to back) design makes the leverage look different.

As for the comments about needing a shorter prop to use peak hp (at UL's 3200rpm), when an outfit like, say, Sensenich matches an airframe and engine, they take that into account. A prop must match both; there's a lot more science involved than meets the eye, and certainly a lot more than mere length and pitch numbers can tell you. And you still need ground clearance for the prop tips.

As for CG shifts, that won't be a factor; once the CG of the FWF is established (based on the weight and placement of components), the effect on the "happy flight controls" will be just about nil. Remember, the installed weights of the FWF packages are very close.

Were I doing it, I'd probably add mounting to intersect the longerons, as well. With the slight weight advantage of the 260 (it's lighter, so more structure can be added), I think the small added mount weight of the added tubes and backing, etc., (maybe a pound; two, tops) would be well-placed. (So, I would not be adding structure to support a heavier engine -- 'cuz it's not heavier; I'd be doing it to have a stronger assembly.)

And remember that the torque on the airframe isn't a result of the torque of the engine; it's a reaction to the torque on the propeller and its relationship to the torque axis -- and all those arguments about longer blades and slower rotation translate into more torque on the mount from the Rotax... which makes the factory mount, with its mounting points and narrow track, more questionable from this standpoint. But I trust they have a pretty good handle on what's needed.

[rv6ejguy]

Originally Posted by Tim Kern

Tony, you mention "To cantilever a heavier and more powerful engine off these mounts an additional 12? or so forward of the Rotax position seems cavalier to say the least."

While the ULPower 260iS is more powerful, it isn't heavier, though its more-compact (front to back) design makes the leverage look different.

Were I doing it, I'd probably add mounting to intersect the longerons, as well. With the slight weight advantage of the 260 (it's lighter, so more structure can be added), I think the small added mount weight of the added tubes and backing, etc., (maybe a pound; two, tops) would be well-placed. (So, I would not be adding structure to support a heavier engine -- 'cuz it's not heavier; I'd be doing it to have a stronger assembly.)

Technically, the 260iS is about 10 lbs. heavier than the Rotax apples to apples, with exhaust, rads, oil cooler, oil and coolant. The power to weight ratios are almost identical.

[RFSchaller]

Seems like it's a question of numbers. If it makes sense and you are EAB, I say go for it. I LOVE "EXPERIMENTAL".

[Phantom30]

Originally Posted by rv6ejguy

Technically, the 260iS is about 10 lbs. heavier than the Rotax apples to apples, with exhaust, rads, oil cooler, oil and coolant. The power to weight ratios are almost identical.

Go with the new li battery and the weight would be equal�� and you would have more juice for your electronic toys (I mean instruments)!

[rongawer]

Originally Posted by rv6ejguy

Technically, the 260iS is about 10 lbs. heavier than the Rotax apples to apples, with exhaust, rads, oil cooler, oil and coolant. The power to weight ratios are almost identical.

Technically, the installed weight of the 912uls is 160.2 and the UL260iS is 159.3. They are nearly identical in weight with UL being slightly lighter as someone else mentioned earlier. If you're building E-AB, the UL260iS has a lot lower price with a cost saving over the Rotax of nearly $10,000, plus fuel injection, FADEC control and the option of a 50A alternator and no gearbox. And all the talk about inefficient prop speeds ignores that the no one runs the UL at redline of 3300rpm, but rather cruising in the 2600-2700rpm range, which when mated to the right prop, makes for a very fuel efficient, speedy, quiet, smooth engine setup with a little more horsepower and a lot more torque.

[joedallas]

Ron

It would be very interesting if vans offered a version of the RV12 with a UL engine and wing tanks.

Vans has the ability to do this best.

I think they would sell more than the current version.

Joe Dallas






QUOTE=rongawer;1028016]Technically, the installed weight of the 912uls is 160.2 and the UL260iS is 159.3. They are nearly identical in weight with UL being slightly lighter as someone else mentioned earlier. If you're building E-AB, the UL260iS has a lot lower price with a cost saving over the Rotax of nearly $10,000, plus fuel injection, FADEC control and the option of a 50A alternator and no gearbox. And all the talk about inefficient prop speeds ignores that the no one runs the UL at redline of 3300rpm, but rather cruising in the 2600-2700rpm range, which when mated to the right prop, makes for a very fuel efficient, speedy, quiet, smooth engine setup with a little more horsepower and a lot more torque.[/quote]

[Driftdown]

Originally Posted by joedallas

It would be very interesting if vans offered a version of the RV12 with a UL engine and wing tanks.
Vans has the ability to do this best.
I think they would sell more than the current version.

If that came about, I would sell my CT and buy an RV-12 (S-LSA).

[crashley]

Weight rotax


Engine with carburetors
124.7lbs / 56.6Kg

Exhaust System
8.8lbs / 4.0Kg

Air Box
2.9lbs / 1.3Kg

Air Filter
0.7lbs / 0.3Kg

Liquid Radiator
2.2lbs / 1.0Kg

Oil Radiator
1.1lbs / 0.5Kg

Regulator-Rectifier
0.2lbs / 0.1Kg

Installed Weight
140.6lbs / 63.8Kg

Weight/power ratio
1.41lbs/HP / 0.87Kg/KW

ul
Installed weight
72.3 kg [159.3 lbs] (including all accessories, oil and exhaust

[joedallas]

Nice Start

Now add the break down showing True HP, wet weight, hoses, fuel system, CG arm of engine, vibration, cost of engine, cost of rebuild of each engine, cost of gear box service.

and also a photo of the final look of the install.

Some like Rotax and some of us Just Don't.

That is why it would nice if we had a choice.

Joe Dallas

Originally Posted by crashley

Weight rotax


Engine with carburetors
124.7lbs / 56.6Kg

Exhaust System
8.8lbs / 4.0Kg

Air Box
2.9lbs / 1.3Kg

Air Filter
0.7lbs / 0.3Kg

Liquid Radiator
2.2lbs / 1.0Kg

Oil Radiator
1.1lbs / 0.5Kg

Regulator-Rectifier
0.2lbs / 0.1Kg

Installed Weight
140.6lbs / 63.8Kg

Weight/power ratio
1.41lbs/HP / 0.87Kg/KW

ul
Installed weight
72.3 kg [159.3 lbs] (including all accessories, oil and exhaust

[Hotscam]

I must admit the ULs look great and specifications and price are promising as well.
We are pretty close to the factory and quite few in use around here.
Unfortunately they seem to have a poor reputation and I have seen builders replace them by Rotax and an LSA munufacturer change their production line from UL to Rotax. Both for good reasons.

I have got two 912's and quite happy with them.
I think the gearbox and resulting efficient large prop ar a bonus.
There are issues with every engine but 40000 airworthy ones do mean something compared to the handful UL ones.