Rotors

[jander14indoor]

You can probably shorten the spray time, only needs a VERY little glue. But I wouldn't sweat it for that little additional gain left.

As to hazards, frankly I suspect the hazard of what your parents will do to you after they discover the mess the overspray leaves unless you protect a very large area indoors far exceeds the cancer risks. Outdoors your exposure is VERY low unless you stand down wind and spray it directly on you. But do what you are comfortable with for safety.

Jeff Anderson
Livonia, MI

[smartkid222]

I wear safety goggles when I use spray glue because once the wind blew the glue onto my face.

[carneyf1d]

Does a variable diameter mechanism count as pitch changing?

[thewinner]

It wouldn't change the pitch...

[thewinner]

And either way, that would add quite a bit of weight.

[smartkid222]

how would such a mechanism work?

[chalker7]

Unless the angle of the blades is changing as well, variable diameter rotors would, technically, change the pitch. If you maintain a constant angle on the blade, but start out with a larger diameter and progressively move to a smaller diameter, the pitch is decreasing. Pitch is determined by the angle of the blade at some fixed location away from the center, as the lower angles move closer to the center, the pitch of the rotor would correspondingly go down as well.

The most common design used in indoor free flight (and by most common, I mean there are probably fewer than 5 people on the planet who successfully use them on a regular basis...variable pitch setups are far more common), uses a trapezoidal hinge system with a rubber band that closes when the centrifugal force on the prop lowers as the power decreases on the rubber band. As you might imagine, they are incredibly difficult to build and get to work properly (and not to mention in questionable legal territory for Science Olympiad helicopters), but I'd definitely encourage anyone with some free time to try it out and post a video if it works!

[lllazar]

So are variable pitch mechanisms really helpful in increasing flight time? I ask out of curiosity, i might try to make something like that.

[smartkid222]

Just so you know for this event the rotors need to be fixed pitch according to the rules.

[lllazar]

I am aware, i just thought it'd be cool to do something like that