Good Morning, Oppo

"ttyymmnn" (ttyymmnn) 04/05/2018 at 09:15 • Filed to: good morning oppo

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!!!error: Indecipherable SUB-paragraph formatting!!! says “Good morning” too.

facw > ttyymmnn 04/05/2018 at 09:20

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Having just a two-blade propeller looks all sorts of wrong.

Demon-Xanth knows how to operate a street. > facw 04/05/2018 at 09:24

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Anything more than none means I’m ready for action:

WilliamsSW > Demon-Xanth knows how to operate a street. 04/05/2018 at 09:33

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What the hell?

AuthiCooper1300 > WilliamsSW 04/05/2018 at 09:41

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Bah, that’s nothing:

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WilliamsSW > AuthiCooper1300 04/05/2018 at 09:46

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OK, I get conceptually that you *can* do this - but for the life of me, I can’t understand *why* you would?

Seems like it would reduce lift without any material benefit to offset that.

someassemblyrequired > ttyymmnn 04/05/2018 at 09:52

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It’s the Balsa-Cedar Goose!

ttyymmnn > WilliamsSW 04/05/2018 at 09:57

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My guess is that it has something to do with counteracting the P-factor .

AuthiCooper1300 > WilliamsSW 04/05/2018 at 10:00

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You can... up to a point. There is an interesting explanation here:

https://aviation.stackexchange.com/questions/21354/is-it-possible-to-fly-with-counterbalanced-single-blade-engines

In the case of the Bo-103, the idea was to do an absolutely “minimalist” machine. There could be other possible motives too, as described here, for example

http://www.sikorskyarchives.com/S-57%20CONVERTIPLANE.php

Demon-Xanth knows how to operate a street. > WilliamsSW 04/05/2018 at 10:00

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The less blades, the more efficient the propeller as they aren’t contending with the other blade’s drag and turbulence as much.

WilliamsSW > ttyymmnn 04/05/2018 at 10:01

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Would it though?

Also, P-factor isn’t that big of an issue unless you’re talking about either a) rotary engines or b) very high horsepower taildraggers.

The aircraft pictured is neither.

ttyymmnn > WilliamsSW 04/05/2018 at 10:07

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I have no idea.

WilliamsSW > AuthiCooper1300 04/05/2018 at 10:11

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Thanks for the links! It makes sense, I guess, and I can totally understand it as an engineering exercise (which is really what the BO-103 was), but the list of downsides is pretty long, and about what I would expect.

For that reason, I suppose that a single-blade, fixed pitch, propeller is probably more workable than a single blade rotor, but I would still expect vibration issues.

AuthiCooper1300 > WilliamsSW 04/05/2018 at 10:20

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You are welcome.

Indeed, for the same reasons explained in the first link. Even if the weight is balanced, the aerodynamic forces are not.

The first time I heard about this was on some news item about single-blade rotors for wind turbines.

I imagine they may work if they are smallish and light, but with a big machine you’d need a more conventional setup.

WilliamsSW > Demon-Xanth knows how to operate a street. 04/05/2018 at 10:30

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Makes sense conceptually, but there are other considerations in prop design, too—

Demon-Xanth knows how to operate a street. > WilliamsSW 04/05/2018 at 10:38

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That’s why not every prop has the same number of blades. Single bladed props tend to be limited to rather specialty applications that require high efficiency over high output.

The opposite end of the spectrum is the UDF:

ttyymmnn > WilliamsSW 04/05/2018 at 10:39

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https://en.m.wikipedia.org/wiki/Single-blade_propeller?wprov=sfti1

WilliamsSW > Demon-Xanth knows how to operate a street. 04/05/2018 at 10:42

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Yeah - shorter blades allows for higher RPM, which you offset by adding more blades. The UDF is a pretty unique beast.

Demon-Xanth knows how to operate a street. > WilliamsSW 04/05/2018 at 10:52

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Blades and supersonic make for unhappy ground crews:

WilliamsSW > Demon-Xanth knows how to operate a street. 04/05/2018 at 10:56

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ttyymmnn > WilliamsSW 04/05/2018 at 12:57

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That thing is such a f**king beast.