What do all the numbers mean on the prop's ie 8 x 3.8 etc and how do work out what prop you should use on what motor?

Cheers Lawrence

the first # would be inches- how long the prop is.

The second # would be pitch. This would be how much forward movement there is. This is the twist in the prop.

If everything being equal- if you increase the prop size in lenght, it will slow the rpm's but increase the thrust.

If you increase the pitch and use a smaller prop, it will lower the thrust but increase speed.

So, your 8x3.8 prop is 8 inches long with a pitch speed of 3.8

When you buy a motor, they usally recommend different props at different voltages. Also using a watt meter will help knowing how far you can push a motor, battery, esc without damage.

Just one tiny correction to the good information provided by BgCatfish1.

The second number in a prop specification is not pitch speed, but simply pitch. It is measured in the same units as the diameter of the prop.

For example, a 8 x 3.8 prop has a diameter of 8 inches and a pitch of 3.8 inches. The 3.8 inches represents how far forward the prop would travel for each revolution if it was running in a perfect "jello-like" medium where every bit of prop motion was translated into forward movement.

- Jeff

Thanks Jeff and Catfish

So I was looking at Hobby Lobby and in a package deal the prop is the same as a GWS1047 (254 X 119mm) so is this just the metric version[]

Cheers Lawrence

Yes, the GWS1047 is 10 x 4.7 inches, which is the same as 254 x 119mm.

- Jeff

to-mato---ta-mato

Good call JD. I just start typing and rambling it all starts to blend together. However, I do agree you are correct.

Thanks Guy's

i just got a brushless motor 5400kv with a 5to1 box it rated 16-18amps and for a 8x3.8 prop
i didnt have a the 8x3.8 so i used a 9x3.8 and on the watt metter wot got about 16 17amps but the motor got warm to fast and so i let it cool down room temp and set it about half throtale for about one min. pulling 6.5amps and it got hot and the 25amp esc was warm
called them guys i got it from explaning the above and they said that the prop was to big put a 8x3.8 on it and it will be fine is that so will over proping a motor but not pulling to many amps still cause it to heat up?

The larger the prop the more work it has to do. Work equals heat. Heat equals bad. You need to get a prop that is called for by the motor maker. They have tested it with different props and battery voltage and they will give you a list of props that will work with that motor and battery voltage. Try and stay in this range. Putting to big a prop on a motor is like driving up a hill in third gear instead of second. You can go slower, but the motor is still working to hard and you need to shift down. Proping a motor is like gearing a car, you want it to do the work, but not lug it down in the process. Drop down on the prop and everything should be OK.
Ed

ok thanks a lot Ed, lhs didnt have one in stock but its do in tomorrow