Engine confusion

[rcsoar4fun]

Today I picked up a Norvel BigMig .061 at the LHS and was doing a little research on it. I have noticed a lot of kits out there say they require a .10 sized engine. I also notice the rating for the Norvel is a good bit more than some of the .10's out there. How does the Norvel .061 rated at .31HP really compare to the TT .10 at .27HP? There is a pretty big difference in weight, so I would think the Norvel would be an overall better choice.

Kristopher

[1705493]

Power to weight, the Norvels are the hands down winners. That includes the .061, the .074 and even the .15. I had a Pilot Pitts sporting an OS .10 that wasn't all it could be. I swapped in an Enya 11CX. This is a superbly made AAC engine with dual ball bearings. NOW the Pitts did much better. But, the Enya is heavy like most Enyas are, cube for cube. Powerful and bulletproof but heavy. The Norvel .15 weighs no more than the Enya .11 so that was installed. NOW the Pitts really shined. The Norvel .15 by virtue of its bigger displacement could swing a bigger prop with more authority and that's exactly what this plane needed. I had to cobble up a Pitts style muffler and add an adjustable airbleed to the throttle but with that done, the engine has huge power and throttles extremely well.

Note that the Pitts called for the OS .10 for power. If you assumed that the Norvel .061 was equivalent, or better, you would have been dissappointed.

If you want sparkling performance out of your Norvel, don't use it in a plane spec'd for a .10 sized engine. Any ten will swing a bigger prop and horsepower figures aren't the total picture. Consider torque and the better effciency of a bigger prop that a larger engine will swing.

Best perfromance with a Norvel .061 comes with a plane with 250 squares and 14 to 16 ounces at the very most. Eighteen ounces gets sluggish and 20 ounces is a killer. At least if you're aiming for sparkling aerobatics.

JMO,

Andy

[sturmvogel]

I built an Akrobat from FM plans and powered it with an old Fuju .15 and it was a dismal failure. It sat around for a year or so and, rather than just junk it I figured for a couple hours work I'd try my Norvel .15. To say that the airplane was transformed was to put it mildly! The verticals demonstrated real authority! The difference was amazing. I agree with Andy, though, a plane designed for a .10 would not sparkle with a Norvel .061 or .074. Prop diameter makes a great difference...
Bob