Prop Question?????

Joined
Jan 16, 2009
Location
SouthEast Arkansas
#1
I pretty well understand what the different props do and dont and what each part of the prop does as far as performance but there is one thing that I dont understand..........

As far as the diameter of the prop what does that do for the performance..........For example.........say I have 2 props.........13x21 and 13 1/2x21................what does the difference in diameters do for performance??????