Nice Plane- but did'n't fly much for ten years

[Rob]

How does 2600 rpm get you much? My understanding was these props at 2400 are supersonic and lose efficiency. Wouldnt an extra 200 rpm just be less efficient?
Havent bought it.

There is way too much black magic in propellors to make any broad stroked comments. That black magic moves exponentially when you include a multitude of airframe / engine combinations to that mix.

First ask anyone who recited the supersonic rhetoric where they learned this and 99.9% of the time the answer is well, just look at so and so's prop size / speed calculator... So and so... you know, the guy who sells prop STC's... How many prop STC's do you think will get approved when said props are snarling sonic booms? They don't want you making noise and making their lives harder at producing props (income).

Secondly, what are you looking for when you push that go knob forward? I'll be completely transparent, I'm looking for a kick in the @$$ launch, I don't give 2 rips what my fuel meter says (and I actually pay for gas) why would I care if my prop is working less efficient (just like my engine at that moment) but making more over all thrust. Motivation, that's all I care about at that moment, I understand that there are folks that enjoy getting outstanding MPG, but they're paying for that fuel, outstanding prop efficiency? I don't know anyone paying for the air they move.... waste some.

200 RPM harder on what? not on an engine designed to run there. More first time tractor owners kill their tractors because they are afraid to turn it at an RPM spec'd for the task, your not 'babying' anything running at less than rated rpm, your lugging it.

Having said all that, I've ran in to probably as many prop engine combinations that pull harder pulled back on the tach as I have ones that pulled harder spooled up more. How an airplanes pulls harder when it's producing less horsepower? I have no idea Gues that's the black magic part.

Pull tests? Na. I never fly with the tail tied down, those tests give me a baseline, but not much else. Seen too many that pulled less tied down only to grunt a better load than the static king.

Noise charts? Na... too many (but certainly not all) pull better snarling.

My money is on how well it gets me off the ground x the time to climb. If I was looking to race, I would probably have a whole different criteria.

Take care, Rob

[KevinJ]

How many hours were you able to put on the cub last year Cardiff?

[mvivion]

How many hours were you able to put on the cub last year Cardiff?

Excellent question.

As to propellers, there seemed to be very little advancement in propeller efficiency and thrust for decades, followed in the last thirty or so years of quite a few significant improvements in props. Today’s propellers pull harder, often at lower rpm, that the older props that Cessna equipped their airplanes with for decades.

Thats a good thing. I agree with Rob that “static thrust” tests only provide part of the story. How that prop performs during acceleration is really what most of us want to know. And, yes, propeller performance seems to involve a good dose of black magic.

MTV

[DENNY]

Rob is correct! Efficient is a useful term only when you state exactly what you are trying to do. Efficient at what?? Making power/improving fuel burn/top end speed/making noise/making less noise/longevity/climb power/producing thrust. Not all engines are created equal!! The reason they put letters behind the 0470 is because they have made changes to the engine, some small, some large. Compression/Crankshaft/piston/counterweights/cam and lifters/cylinders/intake/carb/injected/turbo/exhaust. all come into play. Then you get to add in all the STC changes. Once you get finally start to understand how all of the changes help or hurt your final pick then we get into props. Metal/wood/carbon/blended/blade shape/blade length/number of blades/fixed/constant speed/ect. Wait the prop I want won't fit the engine I want. No problem just figure out the best compromise then that is what you get UNLESS it won't fit the plane you want!! The good thing is you really only get so many choices on a Certified plane. Don't get hung up on a single factor. At the end of the day it is the pilot, much more than the plane that makes the difference!! Pretty much any plane can make you a good pilot if you let it.
DENNY

[stewartb]

180 props aren’t a mystery. In essence you’ll find planes with 82” and 88” props. The former is referred to as a wheel plane prop and the latter a seaplane prop. STOL guys prefer the seaplane props for improved short field performance but give up a little speed at top end. 88” seaplane props are approved with tires on 180s. You can get all sorts of pireps on variations on the theme, but most of those pireps will be on 520 engine upgrades. The old rule applies. There’s no replacement for displacement. That’s an important factor for props. FWIW, while a 470 redlines at 2600, a Pponk 520 redlines at 2700, the same continuous rpm limit prescribed for the IO-520. Most of these props are fully capable of turning 2850 for takeoff and work quite well at that.

It’s ironic how buyers look for low time airplanes and then get scared of infrequent use. 99.9% of GA airplanes see infrequent use. The variable is the definition of infrequent.

[stewartb]

Tonight there’s a 185 on the skywagon Facebook page with 300TTSN, and someone replied with an 1100TTSN plane. Pieces of crap, right? Not flown enough? Ya, right!