Propellers?

[Penguins Suck]

right yous lot listen in, yous are all thick as mints the reason them J models fat herberts have more blades on thems propullors to make it easier to chop thems movers up if thems walkinh into the prop

 

[Ex-Bay]

The "J" propeller is a "High Speed" design that as the outer section of the blade is swept back to reduce (by the resultant airflow due to the sweep) the formation of shockwaves by the resultant velocities of airflow and rotation. The term High Speed refers to the fact that an aircraft fitted with such a prop can fly faster that an aircraft fitted with a conventional prop of the same size / rotation velocity.

Straight from my Module 17 text book.....

Erm, hang on. If I understood what I was told about swept-back wings, they have a little something sticking up to stop the wind 'falling off the end' (the winglets on a big Boeing being an example).
So air doesn't 'slide off' the swept back propeller ?.

 

[shoutingwind]

More power, more blades, the Shack had six per power plant 2150 HP give or take.

is that it? the J has 4700 HP per engine, that is a whole lotta horses i love hi-power runs LOL

i thought wing sweep was to increase span-wise flow to allow the air to re-energise so it sticks to the wing for longer when a plane moves fast.

Maybe i'm getting myself confused, but i thought the sweep on the prop was to ensure the maximum length of the blade was approaching the air at the right angle to create thrust, so the middle was going slower so its needs a smaller angle, while the tip is going faster so it needs a bigger angle....

 

[PingDit]

A little something I came across which may help to explain the efficiency...

A high efficiency forward swept airplane propeller includes a constant leading edge forward swept angle from the root to the tip. The forward sweep is created by leaning the blade leading edge tangentially toward the rotating direction on the rotating plane. The leading edge projection on the axial-radial plane is a straight line with constant axial position from the blade root to the tip. Alternate embodiments of the projection of the leading edge on the tangential rotating plane include: a propeller blade with a leading edge shape that has a smaller forward sweep angle (including 0 degree) in the inner portion of the blade and a larger forward sweep angle in the outer portion; a propeller blade that has a negative leading edge aft ward sweep angle in the inner portion of the blade and a positive forward sweep angle in the outer portion. Alternate embodiment of the leading edge shape projection on the axial-radial plane include a shape which is not a constant line, but at any radial position, the maximum leading edge axial deviation from the root axial position is less than the blade airfoil chord length at that radial position. Compared to the radial blade or backward swept blade, the mechanism that causes the forward swept blade to have a better performance is that the tip pulls more mass flow and has higher flow kinetic energy in the tip region, which suppresses the tip vortex. The effective aspect ratio of the blade is larger and the induced drag and downwash are smaller. The wind tunnel tests and the simulations using 3D computational fluid dynamics software indicated that the forward swept propeller blade of this invention significantly improves the efficiency and stall margin compared to the conventional radial blade.

 

[rest have risen above me]

A little something I came across which may help to explain the efficiency...

A high efficiency forward swept airplane propeller includes a constant leading edge forward swept angle from the root to the tip. The forward sweep is created by leaning the blade leading edge tangentially toward the rotating direction on the rotating plane. The leading edge projection on the axial-radial plane is a straight line with constant axial position from the blade root to the tip. Alternate embodiments of the projection of the leading edge on the tangential rotating plane include: a propeller blade with a leading edge shape that has a smaller forward sweep angle (including 0 degree) in the inner portion of the blade and a larger forward sweep angle in the outer portion; a propeller blade that has a negative leading edge aft ward sweep angle in the inner portion of the blade and a positive forward sweep angle in the outer portion. Alternate embodiment of the leading edge shape projection on the axial-radial plane include a shape which is not a constant line, but at any radial position, the maximum leading edge axial deviation from the root axial position is less than the blade airfoil chord length at that radial position. Compared to the radial blade or backward swept blade, the mechanism that causes the forward swept blade to have a better performance is that the tip pulls more mass flow and has higher flow kinetic energy in the tip region, which suppresses the tip vortex. The effective aspect ratio of the blade is larger and the induced drag and downwash are smaller. The wind tunnel tests and the simulations using 3D computational fluid dynamics software indicated that the forward swept propeller blade of this invention significantly improves the efficiency and stall margin compared to the conventional radial blade.

Glad you cleared that up PD...DT_Xtremez_19:

 

[Ex-Bay]

A little something I came across which may help to explain the efficiency...

A high efficiency forward swept airplane propeller includes a constant leading edge forward swept angle from the root to the tip. The forward sweep is created by leaning the blade leading edge tangentially toward the rotating direction on the rotating plane. The leading edge projection on the axial-radial plane is a straight line with constant axial position from the blade root to the tip. Alternate embodiments of the projection of the leading edge on the tangential rotating plane include: a propeller blade with a leading edge shape that has a smaller forward sweep angle (including 0 degree) in the inner portion of the blade and a larger forward sweep angle in the outer portion; a propeller blade that has a negative leading edge aft ward sweep angle in the inner portion of the blade and a positive forward sweep angle in the outer portion. Alternate embodiment of the leading edge shape projection on the axial-radial plane include a shape which is not a constant line, but at any radial position, the maximum leading edge axial deviation from the root axial position is less than the blade airfoil chord length at that radial position. Compared to the radial blade or backward swept blade, the mechanism that causes the forward swept blade to have a better performance is that the tip pulls more mass flow and has higher flow kinetic energy in the tip region, which suppresses the tip vortex. The effective aspect ratio of the blade is larger and the induced drag and downwash are smaller. The wind tunnel tests and the simulations using 3D computational fluid dynamics software indicated that the forward swept propeller blade of this invention significantly improves the efficiency and stall margin compared to the conventional radial blade.

Ow. My brain 'erts.