Arms lenght for tricopter

[crlock]

Hi guys, i wonder, what is the reason behind the long arms on the tricopter? for quads doesn't seem to be a big deal, but for tricopters the rule is that they have to be long.

I ask, because i'm thinking on a frame with short fixed arms, something like 28-30 cm (11 inches)

cheers.

 

[Craftydan]

I'm in process of building one w/ 10" arms, and I've seen smaller.

No physics restricting it -- mostly depends on the builder and how much they want to copy from David

 

[xuzme720]

Longer is just more stable where shorter is more agile. To a point, you can go too long and introduce torsional issues...

 

[cranialrectosis]

I am also building with 10" booms. I like the quickness of my 14" H quad but to learn to fly a tri-copter I want the stability I have with my 20" AnyCopter (9" booms). The 10" booms will give me a wingspan on a Bat bone of almost 22" from rear rotor to front rotors.

I am hoping that will make for a nice stable copter.