hello all! i need help with understanding what prop to what engine/plane combination. i understand that lower pitch is for 3-D type flying with hovering and all that fun stuff, and that higher pitch is for speed. What does the prop length do?

and can someone tell me what prop to use with these 2 plane engine combos that i have? and without just suggesting a different engine? lol these 2 engines and planes are all i have and can afford for now. just wanna know what prop to use for the time being untill i can afford better engines. what size prop is best for 3-D type flying for the following:

1) Great Planes U-Can-Do 60 w/ super tigre .61

2) Nitroplanes Zlin Z-50 46 size w/ saito fa80

any help would be greatly appreciated!!!!!!!!!
thanks in advance!!!
=kevin

I'm familiar with some of what you have but not all of it. About the Saito, is that an 80 or 82? If it's an 82 I would try an APC 14x4w, if it's an 80 I would try an APC 13x4w. I'm not too sure about the ST 61. It would be good to end up with more of a 3D type blade for the U Can Do but you may have to experiment with different ones to see what works best with it. If you fly at a club maybe there are people that will let you try one of their props to see what works good. That's the problem with prop / engine combos, you might have to try several different ones to find out what works best. So if you can borrow one and try it out that would help a lot.
About the prop length question, what it will do is either allow the engine to throttle up faster or throttle up slower or slow the plane down. Generally if the prop is on the small side the engine will spin up quick but won't pull the plane through the air as efficiently as one that's longer. A prop that's too long will bog the engine down and can slow the plane down.

You always want to keep the engine in the right RPM's for the best power. Go over the power curve and loose power, but too much prop on and the same result.
If for example your engine calls for a 12x8 the you can use a 14x6, 16x4, for 3-D. Now if you want speed you can 11x9, 10x10. As you can see for every inch in dia. lose or add a inch in pitch. This will keep the RPM's at the same level. Dennis

wow, thanks guys!!! that was easy. i been tryin to get a simple answer like this for awhile now! prop length, rpm range, engine...i understand the main idea now! you guys are awsome! thanks again!
-kevin

3d needs thrust.
3d to get quick response for hovering need light weight prop. wood!!!
3d thrust req's powerfull engine with largest dia. prop and 3-5" pitch prop.

larger dia do play in response time of an engine but its the weight of the prop which is the main factor. the lighter it is near the tip the faster it will accelerate. a heavy small dia prop will be slower than a light larger dia one. smaller the engine the less weight comes into play but on a 45 and up its huge. try a 13x4 wood prop on the 61 or maybe even a 13x5 in a xoar or simular prop dont use zinger and so on types.