Prop sizes

Bigger finer pitch props increase thrust but have less top speed - like gearing down in yer car. Great for things liek 3D planes that want to hover and fly straight up.

Smaller diameter coarser pitch props will load the motor to near its maxium horsepower, and are ideal for very fast flight, but may lack teh low speed thrust for good climbrate. Fine for racing...

The large diameter, low pitch prop will also load the engine in its optimum power band if chosen properly. As a side note, when you choose the large diameter, low pitch option, you want the engine to turn more RPM on the ground than you would if you chose the small diameter, high pitch option.

performance?

I prefer it, plus you get a lovely whirring thrusty sound when you fly by! Sounds more realistic, particularly happy with a 12x6 Master Airscrew Scimitar I just bought.

The main things to remember about prop sizes and pitch:

Always select pitch first, then select the length that your engine likes to keep it in the proper RPM range.

Your engine runs best in a given RPM range. That's (give or take)

14000-19000 for .25-.36 size, 13000-16500 for .40-53 size, and 9000-14000 for 60 size 2 stroke engines. 90 size, 8000-13500.

Low pitch=low gear. Pulls hard but not fast. High pitch=high gear. Pulls weakly, but gradually goes fast.

Practical pitch limits on 9" to 11" props is 4 to 7 pitch except on certain competition engines.

Practical pitch goes all the way up to 15 on very long props.

Bob

I'm no expert but the MA Scimitar I have is for IC engines, i've never heard of anyone using a glow prop in an electric set up before, assuming it is the same prop. I do know that glow props are made chunkier and heavier than a prop on an electric set up needs to be, to handle the flick starts, backfires and vibrations etc. So you'll probably find a proper electric one will be more efficient in your setup, but if that's the size the plans specify then try it! Although i'd assume with your set up being a geared one it may not turn the prop as fast as a glow engine can, but let me know how it goes. Oh you might want to carefully sand-off the sharp edges, personal preference really but I decided to do it on mine.

I bought a thin electric APC at the same time I bought the heavier Graupner nylon. I tried the Graupner first (just because it looks more scale) and I liked it so much, I've put the thin electric away. I know I'd have to go with a 12x if I used those - they have the thinnest blade area of all that I used.

I think I'll try the scimitar. Maybe I'll pick up one of each (12x and 11x) and see which one works better. They almost look like an APC electric.

Thanks! Dan.