Rotors

[jander14indoor]

You'll have to experiment to determine if curved are worth the effort overstraight ribs, but broad past experience points that way.
As to shaping ribs, two ways. Mold them or cut them to shape. Look back through this site on helicopters and to last years Wright Stuff archive for details, subject covered several times. Search on "cut ribs".

You can make a shorter rotor lift as much as a longer one, but it will probably take more power, thus flying a shorter time. And you can build the larger ones to the target weight, since there is a minimum weight, any savings of a shorter prop will just be added back as ballast. And it will still need to be twisted along its length since the center of the rotor is flying in a shorter path through the air than the tip. That's what the jig in the photo you cited does automatically the correct amount. Again, look back through the helicopter discussion for an explanation of how this works.

I'm not aware of how you can 'calculate' the angle needed for desired lift. Not that it can't be done, just not sure how practical it is with less than a college level aero degree and a fairly large computer. Probably best to start from a reasonable point based on what you've seen work and experiment from there. See discussions on static testing to speed process.

Jeff Anderson
Livonia, MI

[gabuilder]

How could we create a jig for curved rotors? Mine are extremely hard to put together evenly.

Also, to what degree does the weight of the rotors affect the speed they can spin at?

[Ze_Duke101]

AGAIN CAN I USE WOODEN GEARS ON THE HELICOPTER?!?!?!?!
SERIOUSLY I NEED AN ANSWER FAST!

[fleet130]

AGAIN CAN I USE WOODEN GEARS ON THE HELICOPTER?!?!?!?!
SERIOUSLY I NEED AN ANSWER FAST!

YES you can, but is there anything to be gained?? ( See item #2 under Code of Ethics & General Rules on the National website.) Seriously, the energy needed to overcome the friction in the gears would most likely outweigh any advantage. Of course you might be able to prove me wrong.

[illusionist]

AGAIN CAN I USE WOODEN GEARS ON THE HELICOPTER?!?!?!?!
SERIOUSLY I NEED AN ANSWER FAST!

According to the rules, they are legal. But what would be the benefit of them? They weigh quite a bit... Do you plan on increasing the speed of you rotors or decreasing the power(also called increasing the power)?

[Ze_Duke101]

I can possibly do something to them my little secret :3

[illusionist]

I can possibly do something to them my little secret :3

Haha, okay. If you ever feel like it though, drop me a hint.

[SFCMS]

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[Littleboy]

Section 2a says that commercial kits are allowed. How could your coach miss it?
[quote=]2a. DESIGN: Helicopters may be constructed from published plan(s), commercial kits, and/or a student’s design.[/quote]

[new horizon]

That's true, commercial kits are allowed. If you've never built a helicopter before it may be wise to start with a commercial kit.

Also, can someone please explain pitch/diameter ratios for a rotor? Is pitch in degrees or radians? and diameter in cm or inches? I'm very confused on the units because it seems to make a large difference in what you resulting ratio would be.