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 Rotor Blades, Why...
Kyiv
Posted: Apr 10 2012, 06:28 AM


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So how is the number of blades on a rotor determined? I'm thinking mainly about helicopter rotors, but I suppose this is just as valid for other rotors.


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QUOTE (Rich and Corporations @ Apr 16 2012, 10:06 PM)
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Vault X
Posted: Apr 10 2012, 11:37 AM


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2 is very simple and always balanced, 3 is much harder to balance, 4 is easier than 3, 5 is harder to balance, 6 or more idk. Fewer but longer blades can be more efficient (more eff. wingspan), but take more space, odd blade count is quieter, even count has balance advantage.


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Trinary
Posted: Apr 10 2012, 01:10 PM


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For fast crafts you migh also whant to think about rpm and length to allow higher speeds without retreating blade stall.

If i rember it correctly the US military has some nice course mterial for helicopter aerodynamics avalible from one of the sites in this forums library section
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no endorse
Posted: Apr 10 2012, 02:37 PM


You have way too much time on your hands ...


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QUOTE (Kyiv @ Apr 10 2012, 01:28 AM)
So how is the number of blades on a rotor determined? I'm thinking mainly about helicopter rotors, but I suppose this is just as valid for other rotors.

More blades runs smoother, is quieter, better balanced, and can carry more load better. Two blades are really easy and simple. Imagine the swashplate for a Cobra, and then for a Blackhawk. Yup.



A dominant force in helicopters is tail rotor interaction. In prop planes, it's all about propulsive efficiency at cruise, so you get them curved rotors.


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user posted image
QUOTE (IRC)
[22:39]Spizania: A chain is a unit of length; it measures 66 feet or 22 yards or 4 rods or 100 links[1] (20.1168m). <<< This is why Britian ruled the world
[22:39]Spizania: we created a system of measurements noone else could understand
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[17:57] matinsky theres only one thing that can save saxon england
[17:57] matinsky ...
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[17:57] Rosdivan Frogs?
[17:57] matinsky a mark XXXIII bolo
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Forza
Posted: Apr 10 2012, 03:31 PM


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Would it not also have something to do with the amount of power available against the range of weights to be lifted?


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Samozaryadnyastan
Posted: Apr 10 2012, 04:53 PM


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QUOTE (no endorse @ Apr 10 2012, 01:37 PM)
QUOTE (Kyiv @ Apr 10 2012, 01:28 AM)
So how is the number of blades on a rotor determined? I'm thinking mainly about helicopter rotors, but I suppose this is just as valid for other rotors.

More blades runs smoother, is quieter, better balanced, and can carry more load better. Two blades are really easy and simple. Imagine the swashplate for a Cobra, and then for a Blackhawk. Yup.



A dominant force in helicopters is tail rotor interaction. In prop planes, it's all about propulsive efficiency at cruise, so you get them curved rotors.

So, the viability of a 7-blade rotor would depend significantly upon the extent to which the tail rotor was geared to evade the main rotor?
I take it that simply moving the tail rotor away from the main rotor so they don't intersect poses a variety of issues in flight and generally engineering wise?


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QUOTE (Falls @ Sep 10 2012, 05:14 PM)

QUOTE (Samozaryadnyastan @ Sep 10 2012, 03:24 PM)

What're those three ships tailing at the back?

a good general guess if you look closely is, grossly superior to foreign counter-parts.
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no endorse
Posted: Apr 10 2012, 07:04 PM


You have way too much time on your hands ...


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Moving the tail that far out is heavy. Weight is your mortal enemy in an airplane, but a helicopter is the sort of thing where you'll commit a murder for each pound you can drop.



The tail rotor interaction has a lot to do with stability, noise, and the sheer geometry of it (can't work if the blades will intersect)

QUOTE
Would it not also have something to do with the amount of power available against the range of weights to be lifted?

It's just structurally and aerodynamically more efficient in many ways, though you pay one hell of a complexity penalty.


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user posted image
user posted image
QUOTE (IRC)
[22:39]Spizania: A chain is a unit of length; it measures 66 feet or 22 yards or 4 rods or 100 links[1] (20.1168m). <<< This is why Britian ruled the world
[22:39]Spizania: we created a system of measurements noone else could understand
QUOTE
[17:57] matinsky theres only one thing that can save saxon england
[17:57] matinsky ...
[17:57] matinsky ...
[17:57] Rosdivan Frogs?
[17:57] matinsky a mark XXXIII bolo
Top
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