Originally posted by Daniel Z
if I understand your question... low pitch high diameter props are used to hover because of the increased giroscopic effect, more disc throwing air to the tail and more thrust and acceleration, they will give you less speed in normal flight, and the higher the pitch the plane wants more to torque roll instead of hover.
hope this helps
It works like this:
High Diameter, Low Pitch = More Torque
Low Diameter, High Pitch = More Speed
If your wanting to 3D you'll want to run a high diameter, low pitch blade. This gives you the torque needed to hold the plane on the prop and the higher diameter helps throw air over the surfaces to control it being your flying in a stall. This is why 4 stroke motors are nice with 3D because they can swing a much larger prop vs a 2 cycle of the same size and with the larger prop you don't need the high rpms.
If you want speed you want high rpms (lower diameter) and a high pitch to move the air quickly. Take a Something Extra with an OS46 and a 10x7 prop for example. Sure it may go fast during level flight but pull it vertical and it will lose speed quickly. Take the same engine and mount an 11.5x4 prop and you can point it towards the sky and watch it go up with unlimited vertical however at the same time it won't go near as fast flying level. Take that same engine and mount a 11x6 and you'll have nice speed, not as fast as the 10x7 but not as slow as the 11.5x4, and decent vertical, not unlimited like the 11.5x4 but also won't fall out as quickly as the 10x7.
The trick here is to use the right prop for what you want to do with the airplane or find a prop in the middle that will allow you to enjoy the airplane and fly it to have fun...