The right prop.

[fly boy3]

Hi all, when selecting a prop (electric) for the first time, is this the right way to go about it.

1, to suit the motor speed/watts

2, to suit the model weight

3, to suit type of model

I f it is more than one of the above points, where do you start. Cheers

Edited By fly boy3 on 23/09/2015 18:04:16

[Dave Hopkin]

If its scale then I start with the scale sized prop

Otherwise the ground clearance is a limiting factor

From then I look at the watts needed for the models weight and flying style

Then I look at the size and cell count of the batteries I want to use in it

Then I look for a motor that will give me the required watts and that lipo

[fly boy3]

Thanks for prompt reply Dave. No, not scale but sport flying and OD stuff.  eg say a 1.5 metre glider, or an Acrowot type model Thanks

Edited By fly boy3 on 23/09/2015 18:11:57

[iqon]

when you have done all that , enter the info into ecalc

it will tell you how it will fly ( if you can understand it all )

you will need

weight

cell count and mah

esc

motor

prop size

now you are confused.....

[fly boy3]

WOW, never had this problem with ic, you are right icon, quite confusing, I had better not go there for the time being. LoL. Thanks

Edited By fly boy3 on 23/09/2015 21:45:20

[Geoff S]

The most important thing is to select a prop that draws a current at or below (preferable) the rating for the motor and speed controller. So choose a prop to suit the motor first and choose a motor that is specced to deliver the power you need.  The old rule of thumb was 100 watts/lb for aerobatic performance and that still holds though watts go a bit further with modern brushless motors.

To a first approximation a motor will try to run at a speed determined by the battery voltage and kv (rpm/volt) of the motor and will draw as much current as it needs to achieve that. So, by fitting a prop that's too big you can easliy damage the motor and/or the esc. So a Wattmeter is an essential tool and should always be used when first setting up an electric power system.

Electric power systems have advantages over ic engines in that they are very flexible and by fitting approriate energy sources and the right prop the same motor can deliver the power you need.

Geoff

Edited By Geoff Sleath on 23/09/2015 22:06:59

[Dave Hopkin]

It might sound like a minefield, and unless you use a watt meter and the on-line data about motors it is BUT many motor suppliers sell motors specifically selected as replacements for popular sized engines so that can remove a lot of the heart ache

Tools like ecalc allow you to play with various parameters to simulate performance, ie different motors,lipos props etc which is a very useful approximation