I've held out and avoided the electric for a long time until now so i have questions. I hate being a newbee again. I created a foam delta wing with a 36" wingspan. It weighs in at about 29 ounces fully loaded. Power is eflite park 450 brushless outrunner with eflite 40 amp esc. Brake is disabled. Manual states motor is good for scale park flyers up to 30 ounce . LHS recommended APC 10X7E "thin electric" prop. (not slow flyer) Manual recommends 10X5 to 12X6E. Manual states 890 rpm per volt which comes to 9879 rpm. I am getting around 7500 with 3cell 11.1 volt 2100 pack. Am i over-propped or this a good speed for the set-up? Weather permitting, test flight will be tomorrow morning. I was going to use a spare Align 430XL from my trex collection but was advised that was a bad idea however, the align motor manual includes a prop chart. Does that refer to using a gearbox maybe?

The best way to check for the correct prop is with a watt meter. What you want is to get the most watts at wot without exceeding the rated amps of your motor. Your motor and esc should not get beyond warm to the touch. If you cant keep your hand on either one after flight you are overloading them.

Can i guess that i should use the most prop/pitch that the motor will handle to put it close to peak amps or am i looking for max RPM's?

The idea on this is to get the most power out of your motor without doing it harm at wide open throttle. So yes I would say that getting as close to max amp without overloading is more important than rpms.

IF you want climb performance then go with a longer prop of lower ptich, speed performance is the opposite.

You can get to the max amps from either end of the spectrum, but you need to first figure out the type of fling u want to do, then experiment.........

Yep, the 890 kv is a give away, good motor for spinning bigger props at lower amps. Per MotoCalc 12.1 amps, 21oz thrust, and a prop speed of 43mph. Now that said, M/C is saying 8130 rpm at top speed as the prop unloads. Also 83.3 watts of power.

Like said, watts are watts, how you get there is up to you and your equipment. Say a 10 volt system at a 10 amp draw is 100 watts. So is 20 volt system at 5 amp draw.
Ditto changing prop pitch and diameter, you can change the flight characteristics and still keep similar watts.

Going from the 10 x7 to say a 9x9, drops the amps to 11.4, thrust goes down to 15.9, prop speed goes up to 58.3. Watts 82.2

Similar watts, but a lot more speed with all the rest of the equipment staying the same.

No wonder i held out so long on the nitro. I went through a small learning curve many months ago with some electric helis but they were pretty much all matched up right out of the box. Guess i'll go get me a watt meter and a masters degree. Thanks for all the help.

Ahh, no biggie. Follow through with the stuff Ron told you to read on a rainy day. It won't take long and all of a sudden it will click and start to make sense.

Heck I made the switch back in 2004, and if I can do it you can too.

I see you're down in Fort Misery. I lived there from 84 till 94. Where you flying at?

I just bought a place up in Lakeland, Home to TOP GUN!!!!

Brad

I know it's not that complicated but i've been flying nitro since 1979. 30 years of "should i put a 40 or a 60 in it"? Yes, we had thoughts of moving out but like everyone else, our home is worth about half of what it was three years ago so i guess we are stuck here. I belong to the R/C Hawks in the Cape. I spent a lot of time in Z-hills at skydive city and other drop zones around there. Nice area. I'll make it to Top Gun one of these years.