[JVFan]

Hi to all of you,
I would like to understand the prop chart, I have OS 46 AX with a 10-7 prop, what append if I put an 11-6 or a 10-6.

What the lenght does ?

And what the pitch does?



Thank

[Vulcan1]

Yves,
For a quick and dirty way think of the air is like water. The diameter is the size of the hole you cut through it and the pitch is how much distance it will travel. Ie a 10x7p prop should theoretically move forward 7in. also if you go up in dia. you should also go down in pitch and vice versa. It never really works for 100% but I usually calculate at 75% to get close.
There will be lots of stuff coming on this.
John

[AJCoholic]

Basically, any engine can use a wide series of props. For instance, your 46 will happily run on anything from a 9-6 to an 11-8 and anything in between.

However, to best utilise the power of the engine you have tomatch it up with the plane and what you want to do with it.

Higher pitch = faster top speed (but at a loss of pulling power and accelleration especially on take off)

Lower pitch = more pulling power (at a loss of flying speed)

and the more diameter, the larger the effective area of the prop disk and the more thrust you will get, in simple terms.

Some examples of where to use different props on the same .46 engine:

clean (low drag) speed plane: 9-7 or 9-8
general sport plane or trainer: 10-7 or 11-6
sport aerobatic plane: 11-5 or 11-6
fun fly plane: 11-4 or 12-3

The best thing to do is try a few different props and see how it affects your plane. Just remember to retune the high speed needle for each time you swap a prop.

[voyager_663rd]

Good stuff Andrew.

I use a 9x9 on my SPAD DDust for 100MPH as an example. It sags on takeoff (low pulling power) but great top end.

Kinda like a car transmission: the 9x9 is like starting from 0 mph in
5th gear. Slow to start but look out once she gets motoring.

[AJCoholic]

And conversely, I run an 11-4 on my Jett .46 in a fun fly plane. The plane leaps off the ground like a scalded cat, but it doesnt go very fast in the air... (nor do I want it to )

I forgot to add, in a draggy scale plane like a bipe, especially with a large cowl, you definitely want to go larger diameter and lower pitch. In that type of plane, a prop like the 9x7 or 9x8 probaby wont even keep you in the air.