I flew gas years ago and just put on whatever prop the kit recommended with a given gas motor.
I am now into electric and have a basic grasp of how to choose a motor/ECS and such.
However props just elude me. I see standard 10x8s, 10x8e and 10x8 thin terms used whatever they all are.
Is there tutorial out there I have not seen to teach someone about props?

I have also considered buying a calculator for the computer so I could leave all other items the same and see what changing the ptich and diameter does to the wattage and amp draw on given motor/battery combinations. Maybe this would help me "see" what is happening.

The motor manufacturers have the data for amp draw with a variety of props. There's really no need to spend money on a calculator for that. As for the props you are looking at, an "e" prop is electric only. They are a little thinner and lighter to be more efficient. They can be made that way because electric motors aren't as rough on props as glow engines are.

The two best tools are an in-line meter and a tach.

Plug the meter between the battery and ESC and do some runs with different props. The meter tells you the current draw and the tack tells you the rpm.

My most recent test was picking out a prop for a glider. The OEM motor had eaten itself up and the replacement didn't show up in any of the available applications.

I knew the advertised power for the motor in watts. That was what I wanted to see on the meter with at least one of my props. I ran every prop I had and wrote each ones numbers down as I went. The one that was closest to being right on was what I flew first. Then flew a couple that were close. Got a couple of prop choices out of the test and didn't waste time flying every one in the pile.

Climb was the only parameter that mattered for my glider. The rpm really isn't important for that. But it matters for other model types so I've gotten used to recording it no matter what. I did a prop test awhile back on a buddy's daily flyer and picked the 1st to fly from the meter reading and the rpm. The rpm isn't actually of much concern unless you're worried about either the top speed or the landing speed. You're going to test fly after all.

The ground tests just save you time by rejecting some of the available. Truth is, I don't rely much on the online applications except to suggest what props to take out to the test.

Watts Up meter. Best purchase for electrics since I got into the silent side. http://www3.towerhobbies.com/cgi-bin...&I=LXLMV0&P=ML

I have the watt meter, the problem being if you don't know what you are doing it means buying selections of props and trips to out of town to the LHS.
I thought it there was a tutorial out there it would help.

You'll also want to look at the general configuration of the plane to get a sense of what end of the available pitch/diameter spectrum you'll be wanting to sample from.

ex. - a draggy biplane with flying wires and a lot of scale junk would fly like crap with a small diameter high pitched prop and a lot of RPM's, but that same prop might be ideal for a small/clean fast racer, even though both planes might be using identical motors/ESC and battery.

I downloaded the trail edition of Motor Calc just to see how it worked and with the 450 motor and my plane and a 3s battery it came up with a 10x8 as the ideal prop.
I see however that using that program could help me with my needs and save me money in the long run.
I just might have to pay the $39 and go ahead and get the full version of it.
It just might be cheaper than running 20 miles to the LHSand guessing on props and trying them to find out that I am pulling too many amps.

The more tools you have and know how to use the better.

Use the present motor calc and run an assortment of props through it. Then try them to see if your readings match up to the predictions.

The last time I was in your situation, that's what I did. It was eye opening when I got the real props on the real airplane and ran them. About half of them did not produce as predicted. Some didn't get the power out. Some didn't turn the rpm. One even gave more rpm than predicted.

Good thing was how much time I saved not flying something that wasn't up to the mark.

The whole process provided a bunch of experience. Best thing about it was seeing what worked and what didn't. Next time won't take half the number of props or time. It was really true that theory often doesn't provide very good answers when you actually "ask the question".

I actually didn't use Motor Calc. There are a couple of decent apps online. Can't remember which I used, but if you don't want to "waste money on props", then consider not wasting money on an application that costs money when there are ones that don't.

Personally, I think props are cheap and worth the cost.

Well Iam confused now.
Motor Calc, the demo version, showed the 10x8 as the ideal prop when configured with my plane, my attitude and the other variables.
But whenI put the 10x8 prop on the plane on the bench to test with the watt meter I show 19.73 amps peak at full throttle and 227 watts running the 3s battery.
OK, did someone make a mistake programming the program? My motor is only rated for 14 amps continuous and 18 amps burst for 15 seconds.
OK, I am fully aware that you will not use full throttle much ideally.
But what gives?

Now you see why a lot of us don't rely too heavily on the apps.

But don't be confused about one thing. $40 for an app isn't going to save you any money on props.

You don't mention it, but did Motor Calc predict the watt meter readings? If it did, then try again and check that you got all your input correct. And look carefully at the input you didn't do. Most apps I've used have proven to be worthless unless the motor I plan to use is listed exactly.

I'll try to find that app I used the last time. It's predictions were spot on for the few props it had that I had or could find. BTW, I wound up using a prop that wasn't on it's list.

Yes it showed pretty much what I got on the watt meter which believes me to thing that the specs for  the E Flite Park 450 are incorrect within that program?
The props being tested are G/F Series 3 Master Airscrews I picked up at the local hobby shop.
I did some more testing which some of the same brand/series I have and found that the10x6 is almost perfect for the continuous amps of the motor at 14.6 amps and 174 watts and a 10x7 was 15.9A and 188 watts.
Weighing the plane, a Mini Ultra Stick and then doing some math I find the watts per pound to be the following:

10X6 Prop     108 W/#

10x7 Prop      116 W/#

10X8 Prop      141W/#

Interesting to see the differences anyway.</p>

Not Motor Calc but this site helped me quite well and it's free.

http://www.s4a.ch/eflight/motorcalc_e.htm

Also check the prop chart and basic electric set up sticky at the top of this forum.


Happy flyin' Oscar

So far your cost has been whatever those 3 props cost you.

What I'd do next is buy a couple more props. Any other brand 10x8 and an 11x7 or 11x6. Or do what all of us at the field do, borrow them from somebody.

Fly the 10x8 until you get the 11"ers and you'll have a better feel for how the next best test prop works in the air.

I've never felt I could get a better answer from a formula or app over what I could do with some time, good weather, and a flying field.

I'm pretty new to this too, but I've learned there can be a big difference in props of the same pitch and diameter from different brands. Some may also pull similar watts but generate more thrust.

It might be interesting to see what an APCe does compared to the master airscrew.

Also, as I understand it, the motor will likely pull more amps static testing on the ground than it will in the air, due to airspeed unloading the prop somewhat?