About designing an efficient propeller

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simplex1

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About designing an efficient propeller

Can I really design an efficient propeller by following this theory:

"One can reason that a propeller could be regarded as a rotary wing in which the lift being generated becomes the thrust that moves the aircraft forward. Knowing the number of revolutions per minute at which the propeller would be turning, the speed at which the blade would be moving can be calculated at any point along its length and an appropriate airfoil from a table, developed during wind tunnel tests, can be selected."

Can I simply choose from a table the best possible airfoil (and attack angle) for a certain speed and, knowing the speed distribution of the cross sections in a propeller, stack together these selected airfoils and obtain a highly efficient propeller?
 
Yaaay...more spam.
 
The Wright Brothers designed the first efficient propeller.
 
I want to read the theory, about designing efficient propellers, of those two brothers you are talking about. Where can I find it?
 
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simplex1 said:
About designing an efficient propeller

Can I really design an efficient propeller by following this theory:

"One can reason that a propeller could be regarded as a rotary wing in which the lift being generated becomes the thrust that moves the aircraft forward. Knowing the number of revolutions per minute at which the propeller would be turning, the speed at which the blade would be moving can be calculated at any point along its length and an appropriate airfoil from a table, developed during wind tunnel tests, can be selected."

Can I simply choose from a table the best possible airfoil (and attack angle) for a certain speed and, knowing the speed distribution of the cross sections in a propeller, stack together these selected airfoils and obtain a highly efficient propeller?
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Yes, it's been done for over a century now.
 
The twisted airfoil (aerofoil) shape of modern aircraft propellers was pioneered by the Wright brothers. While some earlier engineers had attempted to model air propellers on marine propellers, they realized that a propeller is essentially the same as a wing, and were able to use data from their earlier wind tunnel experiments on wings. They also introduced a twist along the length of the blades. This was necessary to ensure the angle of attack of the blades was kept relatively constant along their length.[14] Their original propeller blades were only about 5% less efficient than the modern equivalent, some 100 years later.[15] The understanding of low speed propeller aerodynamics was fairly complete by the 1920s, but later requirements to handle more power in smaller diameter have made the problem more complex.

Alberto Santos Dumont, another early pioneer, applied the knowledge he gained from experiences with airships to make a propeller with a steel shaft and aluminium blades for his 14 bis biplane. Some of his designs used a bent aluminium sheet for blades, thus creating an airfoil shape. They were heavily undercambered, and this plus the absence of lengthwise twist made them less efficient than the Wright propellers. Even so, this was perhaps the first use of aluminium in the construction of an airscrew.
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I've heard this same information from multiple sources. This is from: http://en.wikipedia.org/wiki/Propeller_(aircraft)) under Aircraft Propellers section.
 
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William Froude worked it out in the mid 1800's. We still use his equations.

Read this, and then come back if something isn't covered.
 
I think designing a prop using the rotary theory as you desciribe will provide the basics of design. Just like in a helicopter you have more pitch at the root than the tip. Some helicopters have a sweep at the tip just as a propeller. It's all about trying to equalize lift throughout the span and reducing tip vortices. Of course you have other tricks (vortilon tape) used on props as well.
 
The OP is looking for something new in an area that has little left to find. The Wright brother's propellers were about 83% efficient already, and it's only gotten better from there. There are many other things about airplanes that need fixing; one of them is the internal combustion engine, which turns 25% of the heat energy extracted from the fuel into thrust. The rest goes out the tailpipe (50% of the total) or through cooling systems.

Dan
 
The creator of the "Blade element theory" is Stefan Drzewiecki and not the Wright Brothers who just learned about it from Octave Chanute and simply did not understand it, trashing Drzewiecki.

Letter of Wilbur Wright to Octave Chanute
Dayton, July 2, 1903

"My delay in writing you was chiefly due to a desire to first obtain a clear understanding of the Drzewiecki article on screws. [2] This author's methods of thought and expression are so different from my own that it has been no easy matter to master his paper.
It shows a very clear understanding of some features of the question, but as the author seems unacquainted with negative tangential, and with the effect which weight of water acted upon by each part of the screw has in fixing the angle of incidence, the paper leaves much to be desired as a complete discussion of the subject. I am quite certain that his method of constructing a screw of uniform angle of incidence will not give the result intended. The speed imparted to the water by suction before the screw actually has a chance to strike it is also ignored; and no method of calculating the loss from this source is given. Some of his conclusions seem to Orville and me to be rank heresy, but of course we are like the theologians and judge the "soundness" or "unsoundness" of others by the closeness of their agreement with ourselves."
Source: http://invention.psychology.msstate...Chanute_Wright_correspond/1903/Jul2-1903.html

" [2] Stefan Drzewiecki, born in 1844, was the originator of the blade element theory of screws, which considers the blades of a screw as being composed of an infinite number of aerofoil sections. The blade element theory, together with the momentum theory of Froude and Rankine, is almost universally used today to explain the action of aerial screws. In 1900, Drzewiecki presented a paper, "Des Helices propulsives," to the Congres d'Architecture et de Constructions Navales in Paris. In 1901, a second paper by him, "Du Choix des elements determinant les helices propulsives permettant leur facile comparaison entre elles," was published in the Bulletin de l'Association Technique Maritime (no. 12, 1901). The papers were reprinted in Paris in 1900 and 1901 respectively. It is not known which of the two Chanute sent to the Wrights."
Source: http://invention.psychology.msstate...Chanute_Wright_correspond/1903/Jul2-1903.html

Now it is clear, this two brothers were ignorants, made fun of Drzewiecki, in front of Chanute, and finally, in 1908 when they flew in France and US in front of witnesses, claimed the theory of this Polish scientist as their own. Shame on them.
 
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simplex1 said:
The creator of the "Blade element theory" is Stefan Drzewiecki and not the Wright Brothers who just learned about it from Octave Chanute and simply did not understand it, trashing Drzewiecki.

Letter of Wilbur Wright to Octave Chanute
Dayton, July 2, 1903

"My delay in writing you was chiefly due to a desire to first obtain a clear understanding of the Drzewiecki article on screws. [2] This author's methods of thought and expression are so different from my own that it has been no easy matter to master his paper.
It shows a very clear understanding of some features of the question, but as the author seems unacquainted with negative tangential, and with the effect which weight of water acted upon by each part of the screw has in fixing the angle of incidence, the paper leaves much to be desired as a complete discussion of the subject. I am quite certain that his method of constructing a screw of uniform angle of incidence will not give the result intended. The speed imparted to the water by suction before the screw actually has a chance to strike it is also ignored; and no method of calculating the loss from this source is given. Some of his conclusions seem to Orville and me to be rank heresy, but of course we are like the theologians and judge the "soundness" or "unsoundness" of others by the closeness of their agreement with ourselves."
Source: http://invention.psychology.msstate...Chanute_Wright_correspond/1903/Jul2-1903.html

" [2] Stefan Drzewiecki, born in 1844, was the originator of the blade element theory of screws, which considers the blades of a screw as being composed of an infinite number of aerofoil sections. The blade element theory, together with the momentum theory of Froude and Rankine, is almost universally used today to explain the action of aerial screws. In 1900, Drzewiecki presented a paper, "Des Helices propulsives," to the Congres d'Architecture et de Constructions Navales in Paris. In 1901, a second paper by him, "Du Choix des elements determinant les helices propulsives permettant leur facile comparaison entre elles," was published in the Bulletin de l'Association Technique Maritime (no. 12, 1901). The papers were reprinted in Paris in 1900 and 1901 respectively. It is not known which of the two Chanute sent to the Wrights."
Source: http://invention.psychology.msstate...Chanute_Wright_correspond/1903/Jul2-1903.html

Now it is clear, this two brothers were ignorants, made fun of Drzewiecki, in front of Chanute, and finally, in 1908 when they flew in France and US in front of witnesses, claimed the theory of this Polish scientist as their own. Shame on them.
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Can you just state your overall point, so we know what it is?
 
simplex1 said:
It can be a good propeller but the inventor has first to determine its efficiency.

P=engine power delivered to the propeller
T=dynamic thrust
V=the speed of the vehicle pushed or pulled by that propeller

Efficiency=T*V/P
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What makes you madder? Orville and Wilbur being wrongly credited for first powered flight, or nobody listening to you?
 
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You keep posting.

We'll keep pretending like we care.

Okay, maybe we won't even pretend that.
 
Dan Thomas said:
There are many other things about airplanes that need fixing; one of them is the internal combustion engine, which turns 25% of the heat energy extracted from the fuel into thrust. The rest goes out the tailpipe (50% of the total) or through cooling systems.

Dan
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That's a bit generous, IIRC the number is a bit lower.
 
Captain said:
What makes you madder? Orville and Wilbur being wrongly credited for first powered flight, or nobody listening to you?
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We're going to wish we'd been in simplex's corner when he successfully proves the Wrights weren't the first. I'm still waiting for him to prove my theory that all heavier than air flight is impossible. Impossible I say!

All I know is when I'm in ground effect in the 172, just a smidge over idle and I could fly like that forever. How much HP is that in a 172? You're not going to prove anything, get over it.
 
48dodge said:
We're going to wish we'd been in simplex's corner when he successfully proves the Wrights weren't the first. I'm still waiting for him to prove my theory that all heavier than air flight is impossible. Impossible I say!

All I know is when I'm in ground effect in the 172, just a smidge over idle and I could fly like that forever. How much HP is that in a 172? You're not going to prove anything, get over it.
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Ground effect in a 172 has a noticeable but fairly small effect on the power required for level flight unless the wheels are almost touching the ground. The reduction would be about 20% just before touchdown but if you have flaps extended much of that is lost to the extra drag of the flaps and if you're any higher the HP required reduction falls off pretty quickly.
 
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