Aerodynamic lift of blades of a helicopter?

Question

There really isn't a category for this but there should be one for R/C aircraft. I have the micro helicopters and am considering making the blades.

It's a simple matter to reproduce the angle and cover it with the vinyl material for this purpose.

They make carbon composite blades for strength and lightness. They also make blades out of balsa because it's light and cheap. I'm considering using a hardwood. Considering how well that terns out as a start, the balsa wood is pretty cheap to buy. Basically, one has to have a table saw and router to create this little blades. I think the extra weight of the hardwood won't keep it from getting off the ground.

I'm wondering about altering the design. What I'm thinking of doing, is making the blades shorter so that they have less lift and the response will be slower and less prone to over-flying, just for learning.

I believe that if I made the blades wider and/or longer, it would be more for the motor to turn.

This little piece of machinery is quite advanced and quite responsive. In learning how to to control it, if it tips over a bit and touches the ground, there goes the blades.

Therefore, wanting to create blades that are less responsive and barely able to give it lift off the ground.

I know they make they things in ratios for a reason, I hadn't considered over reving the main motor.

But, I guess, it'll be an experiment in model technology. BTW, last I heard, someone was working on a R/C model of the Harrier jet with ducted fan little jet engines.

Answer 1

Helicopter blades are just wings flying in a circle. So, the same things that apply to wings apply to helicopter blades.

Long, thin blades will have a higher efficiency (lift-to-drag ratio), but long, thin blades are of course not as sturdy, so it is important to use a strong material.

The responsiveness of the motor will depend on the moment of inertia of the blades, and if you keep the mass of each blade the same while making them shorter, the responsiveness will be increased, due to the smaller moment of inertia.

The question is will the smaller moment of inertia be outweighed by the loss in efficiency? Only experimentation (or computational fluid dynamics) can tell for sure.

Answer 2

You need the blades to be flexible, so that when the copter bites the dust the blades will flex, but not snap.

See if you can make them out of a thin plastic material, and make them flexible.

We have several small captive "Whirlybird" copters, and their blades are a very thin plastic, and they have their outside ends tied together with a circular piece of plastic to which each blade is attached.
Each blade (there are four blades) makes a radius of the circle and is attached to both the hub and the outside ring. The whole blade assembly very structurally sound, yet still flexible.

Answer 3

Not knowing which type of micro-copter you have it is hard to make a suggestion.
If you have the new one with a single main rotor and not the contra-rotating kind, I would suggest a very small increase in the weight of the small flybar above the main rotor.
Be very careful how much you change the mass and keep it balanced but it should slow down the response of the rotor.
cheers.

Answer 4

they actually tried this with the apache helos...The army could not figure out why they were burning up gear boxes..The shortening of the blades caused the rotor to overrotate..basically overspeed the engine.
I dont know if you will have this problem with your rc or not.
either way good luck.