Switching to lipo, need new prop

[kevinmuff]

So i went to the hobbystore, because im in the process of switching to lipo.
I have read on here that a switch to a 10X6, or 5 prop would be recomended so you dont burn out the motor after the lipo change.
But when i went to the hobbystore, the guy there said that the supercub actually comes with a 10X6 prop origionaly, and going with a more aggressive prop would actually burn out the motor faster.
I then purchased the supercub LP prop, which is a 9X6 i think.

Anyway... which prop should i use?
I also want to note that the ACP 10X5 prop that i found, would not have connected to the supercub anyways, it did not have that hex patern for connection.

[flydiver]

Ah yes, use a GWS 10x6 HD, the 'new' stock 9x6, or an APCe 10x5 (need collet adapter).

More than burn out the motor, the larger props can burn out the ESC/RX if used too long. Motor cheap, RX/ESC expensive and sometimes impossible to get.

3S Lipo @ 12.6v is MUCH higher voltage > much higher prop RPM > much larger power draw > much more electrical stress on the electronics.
To counteract this you 'prop down', much like shifting a car to a lower gear when the load becomes excessive.
Over propping is a frequent mistake, and a major problem with folks that don't understand electric motors. Pretty soon you'll have people like me telling you to get a wattmeter.

www.rcgroups.com/forums/showthread.php?t=311574

Once you start modifying or building your own power systems it becomes an indispensable tool.

[kevinmuff]

i have this
www.tequipment.net/TPI133.asp
will it work?
So if im understanding correctly, you want to get a BIGGER prop correct?
The one i just purchased, the 9X6, will work as well?

Im just a bit confused, because the two contradict each other. The prop i have on right now is a bigger one, so why would i want to go down to the 9X6 smaller one?

And what is that "collet adapter" that you speak of? Is that how i get the APC 10X5 to work on the plane?

[flydiver]

The DVM is a useful tool. It is NOT a wattmeter. Wattmeter is WAY more useful in this sport. Read the link. If you want to learn you read all the links I provide. I don't go look them up for my education.

Electric motors are constants speed devices. They always want to go at the maximum amount of RPM they are designed for. As you increase voltage, they go faster. BUT, like all motors they also have a maximum load. As you increase RPM you increase the load. As you increase prop size you increase load. Too much load > fried motor.

It sounds backwards but as you increase voltage > you decrease prop size. If you don't decrease the prop as you increase voltage you are effectively increasing the load. At some point you exceed the motor's capability, excess voltage is turned to heat > either you toast the motor or exceed the ESC rating and something fries. In the stock SC it'll be the ESC most likely.....it's more expensive.
Some kind of Murphy's Law you'll always toast the most expensive or hardest to replace part.

You are getting a higher voltage battery > you need a smaller prop compared to the NiMh 10x8 prop.
Those props I listed above all have different sizes but when hooked up with a wattmeter with the same motor and battery they will have almost identical outputs. Size designation is not the entire story, which makes prop selection harder and the wattmeter more of an important tool.

Collet adapter:
www.bphobbies.com/view.asp?id=C3692004&pid=C3581987
www.headsuprc.com/servlet/the-PROP-MOUNTING-cln-Prop-Adapters/Categories
Most planes do not have threaded shafts. This is a more common way of fitting props.
The Cub is a trainer, it has LOTS of compromises and non-standard equipment.