Originally posted by sandal
One way to select prop size:
1. Choose pitch
high pitch = high level flight speed
low pitch = good climb rate and acceleration
2. Choose diameter
large diameter = low rpms
small diameter = high rpms
This is the way I do it. Type of airplane and flying style decides pitch. Then I choose a diameter that puts a suitable load on the engine with the pitch I chose.
If you are using a 10x4 and want more speed, you must increase pitch. If you increase pitch to 8, you will have to decrease diameter to 9 or even 8 to allow the engine to rev up to "where it belongs" (typically 12-14k for a 40LA...?)
The 10x4 is a prop that gives you good climb rate, but it is not the best for speed. So I think, as Geistware and MikeL suggested, that a 9x7 or 8x8 is what you are looking for. But theory is theory, and the best way to find out is to try a few different types and see what you like best.
Hope this helps!
Tore S.
EXCELENT POST!!!!!!!!
Thanks sandal and the rest who responded.
Learn something new everyday.
Small prop for more speed.
I see where the rest also suggested a smaler prop.
Well I have an order here for TH so I may as well pick up a dozen props of different sizes.
Many thankd Guys
