Three-blade rotor heads have become a hot topic in
the RC helicopter world. A number of manufacturers
have released helicopters with three-blade heads
or retrofit kits for existing helis, and some of the
best 3D pilots in the world are using these designs
in competition. This month, I’d like to take a look at
three-blade heads and their strengths and limitations.
That way, you can decide whether three-blade flight
might be right for you.
Three-Blade Rotor Heads
Are three blades better than two?
Heli Talk
Text & photos by Jim Ryan
Theory
The underlying theory behind a three-blade rotor head is pretty logical.
The idea is that with three blades you get both greater stability and
greater responsiveness. So how does this free lunch work?
Stability: With three blades instead of two, you have greater rotor disc
inertia owing to the 50 percent greater rotational mass, thereby making
the helicopter more stable in a hover and in cruising flight. In essence, the
rotor disc is a spinning gyroscope, and the greater the mass, the more it
will resist deviating from its present attitude.
Responsiveness: It may seem counterintuitive that a more stable
rotor head can also be more responsive, but with three blades, you have
SAB has been a leader in the three-blade revolution, with three-blade
versions available for several of its
most popular machines. Here, Kyle
Stacey shows off the paces of the
three-blade Goblin 700 at the
2016 IRCHA Jamboree.
