Exactly right

Think of it this way.

Large diameter/low pitch equals more pull/thrust less speed

Small diameter/large pitch equals less pull/thrust more speed

To chose the correct prop for a given situation, it's sort of an art and science. For example, a Four Star 40 using an OS46AX flies very well with nice speed on an APC 11X6. An APC 11X7 will really make the plane scream but you just increased your takeoff roll and the time it takes to get to that speed not to mention the plane will be difficult to slow for a landing.

Same plane/engine combo now turning a 5 pitch prop will take off in a shorter distance, not fly as fast, but when you go full throttle and pull vertical it will climb like there is no tomorrow.

The other thing to remember is chosing a prop that keeps the engine in it's power band and works well with the plane.

A YS110 loves to be running right at 9000 rpm and an APC 16X6 prop puts it right there, put this same engine/prop in a Funtana90 and that prop delivers to much speed for the plane as it's very lightly built and will blow itself apart quickly (flutter). So I use a 17X4 prop on it. It now flies nice, not to much speed and when I go full throttle and pull vertical it just climbs until I tell it to stop and the engine is only getting 100+/- more RPM's.

If you want to see the effects of a low diameter, high pitch prop, here is a video of a Patriot using a ST 50. The prop is a custom cut 10X8.5 and you'll see that it needs lots of runway to take off and land and until he makes the first dive at the ground it does not have a lot of airspeed.

http://www.hiddenhangarrc.com/video/...ll_Patriot.wmv

This nextr video is me flying the Funtana90 with a low pitch prop. You'll see right at takeoff how I can pull vertical with little airspeed and go straight up

http://www.hiddenhangarrc.com/video/..._Funtana90.wmv