Originally Posted by
mgnostic
You are coming in to that size of airplane where the gasoline engines start to pay off over glow fuel. The four strokes aren't so bad but when you get into the larger two stroke nitro engines they can be a bit thirsty. I run a 25 cc engine in my BUSA N-17 . It has a 16 oz tank but I only used about 16 oz total during two flights yesterday. With a Cub you will likely spend less time at full throttle than I do with the fighter plane although as the saying goes, your mileage may vary. As Rich points out, a 16 oz tank is more than enough.
I know this is comparing apples to oranges but in my 1/8 scale unlimited hydroplanes, I carry around 20 ounces of fuel for a marine .67 sized engine. That lasts me for a bit over 5 minutes. There are a couple of differences in how a marine .67 and aircraft .60-65 run:
1) My engine tops out at 28K, the aircraft engine maybe 12K
2) My engine runs 50% nitro, 18% lubricant and 32% alcohol fuel, unlike an standard aircraft engine that runs 5-10% nitro, 18% lubricant and 72-77% alcohol fuel.
3) My engine is driving a 2.36" prop, a comparable aircraft engine drives a 12-16" prop, the goal being to get a proper load on the engine and to prevent over-revving(or should I day detonating) the engine.
As I said, apples to oranges but, that being said, application will affect how much fuel you can carry and how long you can fly with that load of fuel. Just be glad you're not using a ducted fan engine as they go through fuel faster than my boat engines do.