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Newbie question

#1
Hello
I have always bought rtf planes . I have decided to give building a try.
Could someone please explain how I find the right motor etc prop combination

There are a hell of alot of motors etc and I don't have a clue what it all meens .

How do you decide what the correct mix of components to use ?

Is there a formula or perhaps a mobile phone app or website that can make it easier ?

Thanks
 

Merv

Well-known member
#2
All of the Flite Test plans have a recommended equipment, this is a great place to start.
A lot depends on the size of plane you want to build and how you want to fly, fast, slow, 3D, etc. Here are some general guidelines.
  • Less than 50W/lb - very lightweight / low wing loading slow flyer.
  • 50 to 80 W/lb - light powered gliders, basic park flyers and trainers, classic biplanes and vintage ('Old Timer') type planes.
  • 80 to 120 W/lb - general sport flying and basic/intermediate aerobatics. Many scale (eg warbirds) planes suit this power band.
  • 120 to 180W/lb - more serious aerobatics, pattern flying, 3D and scale EDF jets.
  • 180 to 200+W/lb - faster jets and anything that requires cloud-punching power!
Regarding motors. All motors will have a kv, that is how may RPM's per volt. A 1,000 kv motor will spin 10,000 rpm's on 10 volts. More volts = more rpm. We typically use Lipo batteries, 4.2 Volts per cell. More cells = more volts. So more cells = more rpm's.

Regarding props. The faster you spin a prop, the harder it will pull. The larger the diameter, the harder it will pull. The larger the pitch, the harder it will pull. Prop pitch is how far it will move forward with one revolution. More pitch = faster plane but less thrust. Less pitch = more thrust but less speed.
 

quorneng

Active member
#3
Garyinnz
There is no magic formula.
How about starting off by designing a plane similar in size and weight to one of your rtfs? You will then have a "workable" motor, prop and battery combination available either directly transferred over from the rtf itself or by buying new equivalents.
You will achieve something if your design actually flies"better" than the rtf in some way that you intended.
 
#4
For your first few builds its hard to beat the simplicity and enjoyment of doing one of the FliteTest speed build kits with the power pack they send with it... you can watch all the build videos you want and get ideas, but until you start putting things together yourself it's hard to know what will work best for you.

Be careful though... the building is almost more addictive than the flying!

in no time flat you'll have a shelf full of spare parts, a wall full of marginally flyable planes, a box full of random lipo battery sizes, and plans in your head how it all goes together to build another one...