Originally Posted by
Hydro Junkie
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.
Hi HJ. Apples to oranges and maybe even a papaya. I gotta agree with you about ducted fans. They are the gas guzzlers of the modeling world. Even the electric fans, which seem more user friendly than fuel power, blow through their energy store faster than anything else. It's been over a decade since I saw a glow powered ducted fan anywhere other than Youtube or a swapmeet table.
As power goes you would obviously be aware of nitro is where it's at. You are probably far more experienced at getting racing levels of power out of an engine than I am. For ordinary flying it is more about matching matching up the right fuel to the right size of engine. This is a broad generalization but generally speaking methanol is generally friendlier to use in two strokes under one cubic inch. Once you start getting into bigger engines the much greater fuel consumption of glow engines starts to become an issue. Given the appropriate carb and tuning a 50cc engine will happily burn 15% nitro glow fuel but you end up blowing through $25 worth of fuel in a flying session. It's just my experience but it seems like after you get over about 20cc of displacement it is just more economical to get your power from displacement as opposed to hot fuel. I'm sure there are a of exceptions to this, certainly racing is one.
Are the converted Homelites still a thing in boat racing? It would be interesting to see the fuel consumption of a hopped up fuel burning Homelite versus the converted 25cc that I have pulling my Nieuport around.