I'm fairly new to RC airplanes. I thought I understood prop sizes, but I'm not sure anymore. Can anybody explain it to me. For example, an 11X6 versus 11X8...I understand the second number is the pitch, but what happens as the number gets larger? Does the pitch get smaller (flatter) taking less bite of air, thus allowing higher rpm's? And, do higher rpms translate to more speed, but less torque for power during climbs, etc. What happens if I want to step up to a larger prop....do I need to decrease the pitch to keep the same rpm's due to the longer prop? Any help unlocking this code would be greatly appreciated.

the higher the number the steeper the pitch (taking bigger "Bites" of the air which allows the plane more thrust for every rotation, although this takes away some of the RPM)

thats what i always thought anyway...

the first #is diameter, for planes with less drag you should use a larger diameter, smaller pitch prop(within guidlines of engine manual). and with planes with more drag(ie biplanes) should use props with larger pitch and less diamter.

Hope this helps, Dave Trimmer.

P.s. Welcome to the confusion and adiction

What Dave said, reverse that!! You will want a low pitch larger prop for planes with lots of drag such as Biplanes. [8D]

I agree with FastSky.

analogy to cars - changing from an 11x8 prop to an 11x6 is like changing rear axle ratios from a 4.11 to a 4.56. If you don't understand cars, nevermind.

well, my bad. you should all know not to listen too me any ways

Another member sent me this link:

[link]http://www.bmaps.net/software/thrusthpv20d.zip[/link]

It's a great way to see what different props do at different RPMs.