Rotors

[Draylon Fogg]

no the motor stick is solid. otherwise that would be the first thing i would change

[WCarneyJX]

Next thing I would check would be that the rotors have equal twist. Did you build yours from a jig? This seems a more likely source of trouble than the weight being balanced. Then I would check the shaft for bend/twist or that it has wiggle room in the shaft. Also look at your hook, is the rubber in-line when wound?

[ironchef48]

Do you necessarily need spars on your rotors? if so do they need to be curved to make the wing aerodynamic?

[illusionist]

Do you mean Spars, or Ribs? Ribs are the ones that go between the spars, and the spars are the long members(usually around 39 cm). The spars do not need to be curved or bent. Curving the ribs creates an aerofoil for the rotor, possibly improving flight.

[illusionist]

Sorry for the double-post. For making a jig like this one: http://www.turnertoys.com/G1/parlorcopter.htm (scroll down a bit), does anyone have any proven dimensions. To get the right pitch (I know it varies with rubber size), but is there certain dimensions that seem to work for you?

[calgoddard]

It llooks like someone else already posted an answer to the question about spars three posts above during the time I was writing this answer. I will go aheand and post it anyway.

I think you might be confused between spars and ribs. A spar for a built-up rotor for a SciOly helicopter is typically a 1/16" square piece of balsa that extends radially outward from
the axis of rotation. Typically such a rotor has a leading edge spar and a trailing edge spar, connectd by curved balsa ribs and covered with plastic film or tissue paper. The rotor is usually constructed by placing two such spars in criss-cross fashion on a jig so they can be connected with ribs to produce a rotor comprised of pair of oppositely extending helically-shaped blades.

Spars are not technically needed to construct a rotor for a SciOly helicopter. You can make the blades from 1/32"sheet balsa, curved to provide the optimum blade shape, without any need for spars or ribs. At our recently completed regionals I don't recall any of the helicopters that were flown in competition using solid balsa rotors.

In a built-up rotor, the ribs do not need to be curved, however, the general consensus is apparently that curved ribs result in a more efficient rotor in terms of the lift it provides.

[lllazar]

They definitely do (Curved rotors), and with an easy build jig, it's not that difficult to build them^^

Is it possible to use 1/32 strips for the ribs? They would be 1/16 x 1/32, would they be too flimsy? I'd just like to cut down the mass of my rotors from 1g to around .9g because i need a little more lee way in terms of final mass of the heli so that i can add more clay to the bottom.

[smartkid222]

I do not recommend it. Examine what density you are using and see if you can use lighter wood. I assume that you are using ultrafilm or lighter covering. If not, using lighter covering may help.

[lllazar]

Well i am actually using ultra mylar. But anyway, i think the problem is my spars - they are really dense. I thought they'd need to be like that but im gonna cut it down to .2g per spar, maybe less.

[illusionist]

Does one work better than the other?:
(Large or small is based on the surface area of the rotors)

1) Large rotors, with a low pitch
2) Smaller rotors with a high pitch