The more I learn about this hobby the more I realize I don't know. That being said, how do you determine what size prop you should put on your motor? I would imagine that motor size, motor kV (RPM) rating, plane size and weight are the major considerations but I don't know how to put all the pieces of the puzzle to gether. Also, how does the prop size pertain to speed(i.e. the larger theprop the faster/slower your plane will fly)?Any help woudl be greatly appreciated.

Brett

Unlike Glow and Gas engine planes, the PROP on an electric plane, determines how much power the electrical system will consume.

Put too large of a prop on a glow engine plane, and the engine will bog down, but it is still likely to run.

Do the same with an electric plane, and you are likely to see smoke billowing out of your plane!


The prop size is selected to most effectively match the power capacity you've designed into your electrical system/motor, while giving you the amount of power you are seeking.

Sound a bit nebulous?

Well it is, because selecting the prop on an EP plane is not how you normally start off!

See next message....

Instead of retyping a long tome, refer to this thread: [link=http://www.rcuniverse.com/forum/m_9391093/anchors_9395561/mpage_1/key_/anchor/tm.htm#9395561]Click me![/link]

I already have a Super Tigre .400 motor 20A speed controler and 3S 1800mAh battery. All this is on my Slow Stick. I have noticed that there are many different prop sizes, even those listed as slow flyer props (which, I would assume, you would use on a slow stick). I just was curious if there were any advantages or disadvantages to the prop size. It would seem to me opjose, based on what you said, that the smaller the prop the better it is for your engine, correct?

Smaller is not necessarily better, but it is "safer".

Some motors have recommended props, which tends to keep the motor well under it's limits.

However changing one of the variables such as voltage, etc. can mean that the same prop may blow your motor or ESC.

So things have to be balanced out somewhat.


The larger the diameter, and/or the higher the pitch, the more current is consumed by your system.

But at the same time, the more powerful your plane becomes...


On a slow stick, you don't want a lot of speed, so a wide low pitch "E" or "SF" prop may be what you are looking for.

What is the KV rating of your 400 motor?

What is it's rated Continuous and Max Amp handling capacity?

Thank you for your help. My motor has a 900kV rating. As far as the amperage rating... I don't know. I know the Super Tigre recommends their 20A speed controler with it so I would imagin that the maximum amperage would be somewhere around 20A. I read your posts from your above link. Lots of great information, even if it will take me a little while to digest all of it.