ORIGINAL: dszabo2
That is some what contrary to what I was told.
Assuming that having alot of vertical means needing torque, I would use a large diameter prop with a low pitch. Therefore the plane would hover well but not fly very fast. Is that a correct analogy?
Dave
That is correct -- however, prop selection often isn't that simple -- it also very much depends on the particular airframe, as well as the operational characteristics of the powerplant.
Despite the general rule that small diameter, steep pitch props will make a plane go faster, it is entirely possible that a small steep prop on a bulky airframe with a big wide cowling, will make the model go slower than it would with a larger diameter flat prop.
Similarly a big flat prop on a 4-stroke engine may give poorer climb performance than a prop with more pitch -- 4-stroke engines have a limited rpm range, & when they are operating near their peak rpm, they can't spool up any faster with a flat prop, so thrust actually falls.
Prop selection is part application of "general rules" and part black art -- which is learned by practical experience.