Q's for you all
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Silkhands - you post sounds like something that came out of the Monty Python school of logic. Whatever those pills are that you are taking, stop it. 
SixDemonBag - In reference to square tip vrs round tips. Yes, they produce more drag, BUT, if you are trying to put the maximum amount of power into a propeller, for a given rpm and pitch, and assuming a constant number of blades, you can only then increase the area of blade. If you have already reached the limiting diameter (i.e. trans-sonic tips), that only leaves increasing the blade's chord, or it's camber. Square tips are an improvement in the former. Square tips = "wider" chord = more area = more thrust (just like a helicopter blade). For a given blade diameter, a round tip prop cannot produce the same thrust as a square tip, unless it has a wider chord elsewhere. It is however, like everything, a compromise.
The peculiarities of the engine it is mated to is a big factor in chosing the design, as is it's anticipated operating environment. A given aircraft might perform better using square tips instead of round tips, because of the power curve characteristics of the engines and the flight envelope and role of the aircraft itself. As Checkboard points out, a big avantage of a square tip is it's resilience to stone chips (perhaps SFTOL operations), and ease/economy of manufacture.
It's clearly a case of horses for courses.
[This message has been edited by Weary (edited 07 September 2000).]
[This message has been edited by Weary (edited 07 September 2000).]
SixDemonBag - In reference to square tip vrs round tips. Yes, they produce more drag, BUT, if you are trying to put the maximum amount of power into a propeller, for a given rpm and pitch, and assuming a constant number of blades, you can only then increase the area of blade. If you have already reached the limiting diameter (i.e. trans-sonic tips), that only leaves increasing the blade's chord, or it's camber. Square tips are an improvement in the former. Square tips = "wider" chord = more area = more thrust (just like a helicopter blade). For a given blade diameter, a round tip prop cannot produce the same thrust as a square tip, unless it has a wider chord elsewhere. It is however, like everything, a compromise.
The peculiarities of the engine it is mated to is a big factor in chosing the design, as is it's anticipated operating environment. A given aircraft might perform better using square tips instead of round tips, because of the power curve characteristics of the engines and the flight envelope and role of the aircraft itself. As Checkboard points out, a big avantage of a square tip is it's resilience to stone chips (perhaps SFTOL operations), and ease/economy of manufacture.
It's clearly a case of horses for courses.
[This message has been edited by Weary (edited 07 September 2000).]
[This message has been edited by Weary (edited 07 September 2000).]
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The square tipped blades on a Herc prop are for high thrust at low speed, useful for dragging the aircraft out of short unimproved strips. Problems of transonic flow at the tip are avoided primarily because the shape and therefore the drag of a Herc prohibits a really high speed cruise. Hercs cruise at around 300KTAS.
The Orion however, only operates out of longer hard surfaced runways and spends the majority of its time in high speed cruise and so has a rounded tipped props.
If you compare the two aircraft you will notice that the Orion has a much thinner wing and smaller diameter fuselage than the Herc, also the Orions MAUW at 135,000lbs is 20,000lbs lighter than the Herc.
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The Orion however, only operates out of longer hard surfaced runways and spends the majority of its time in high speed cruise and so has a rounded tipped props.
If you compare the two aircraft you will notice that the Orion has a much thinner wing and smaller diameter fuselage than the Herc, also the Orions MAUW at 135,000lbs is 20,000lbs lighter than the Herc.
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