Helicopter B/C [Trial]

[baker]

Yeah, 10 grams was way too heavy for the lift. Used 2 liter pop bottle plastic for props, 15 deg right for push, 15 deg left for tractor (1.7 gr each), props were approx 6 inch lg, 1 1/2 in span. Glued to a 1/8 inch dowel approx 2 inch lg., 1/8 in. ID alum tubing approx 2 in lg for a prop hub. Adjustable pitch by twisting in hub. Harlin S.O. bearing. Old motor stick from W.S. days (2.5 gr). Used the pusher blades for fixed postion, tractor on the motor. Started with .090 motor but prop speed was way to slow. changed over to .125 motor, with flat pitch, then tried 45 deg pitch, but broke tail hook when I put loaded motor on (80 turns / 16:1). Just no lift, too heavy. But like I said, that was take one. First W.S. was less than a minute, but last one was 4:28 at states.

[cypressfalls Robert]

baker, 10 grams is way too heavy, you need to cut that in half at least to get it to fly. Did you have one or two 12 inch diameter props? If one, how did you control the torque? What pitch(s)?

cypressfalls_Robert, a prop is the propellor or rotor which spins to create the lift in a helicopter (thrust for a plane). In a full size copter its the blades on the top of the copter which spin around, disk parallel to the ground. The motor stick is just the main structural element, usually a simple stick for these competitions, which holds the rubber motor. There's a hook on one end, and a bearing on the other to hold one of the rotors. The wound motor goes between the hook and the shaft of the rotor.

Hope that helps, if I can find more time, I'll try a drawing, but that's definitely NOT my strength.

Jeff Anderson
Livonia, MI

I kind of have a picture in my head, thanks

Yeah, 10 grams was way too heavy for the lift. Used 2 liter pop bottle plastic for props, 15 deg right for push, 15 deg left for tractor (1.7 gr each), props were approx 6 inch lg, 1 1/2 in span. Glued to a 1/8 inch dowel approx 2 inch lg., 1/8 in. ID alum tubing approx 2 in lg for a prop hub. Adjustable pitch by twisting in hub. Harlin S.O. bearing. Old motor stick from W.S. days (2.5 gr). Used the pusher blades for fixed postion, tractor on the motor. Started with .090 motor but prop speed was way to slow. changed over to .125 motor, with flat pitch, then tried 45 deg pitch, but broke tail hook when I put loaded motor on (80 turns / 16:1). Just no lift, too heavy. But like I said, that was take one. First W.S. was less than a minute, but last one was 4:28 at states.

I have no clue what that means, which is why I need drastic help.

[baker]

http://home.att.net/~dannysoar/ceilingWalker.htm
http://www.hobbylinc.com/htm/mid/mid52202.htm

[cypressfalls Robert]

I picked up an old wrightstuff plan booklet thing and got most of the information i needed, thanks jander for helping(I don't really need a picture), also I had one more question; should the copter be designed to fly in a climbing turn or fly straight up and down?

EDIT: does anyone have any website(s) that shows helicopter plans?

[bchero]

Hey everyone! I'm a newbie for this event and wanted some more information about kits. What kit would you recommend for a newbie like me? I have seen the pennicopter and the Wright Bat, but I was unsure as what to buy. Could someone help me out here because I need to have this thing built by states in NY? Thanks!

[wlsguy]

Who said solid prop? Not required in the rules...

The rules say that "Helicopters must be constructed only from wood, paper, plastic film covering and glue."
I think this pretty much rules out using plastic for the props.
The items left are solid balsa prop blades or something built up (like an indoor duration plane).

Anyone disagree? Do you think it needs a clarification?

Thanks.

[shaneisgreenland]

Alrighty, so I found this design on eHow:

http://www.ehow.com/how_4678177_make-ru ... opter.html

It seems pretty good, and I think that the copter would actually fly. But I have two questions: 1. How do they weigh the motor? Because there doesn't really seem to be a motor in this design, really, so I was confused. 2. Are the materials they list safe to use without getting in trouble? I know that everything besides the bead are safe, from what I've checked, but I don't really know. Some help would be very nice.

EDIT:
Also, how would one go with making the blade? Would they make them a little bit angled, or just straight, or what? I feel like I won't understand the answer to this, though.

[jander14indoor]

Hey everyone! I'm a newbie for this event and wanted some more information about kits. What kit would you recommend for a newbie like me? I have seen the pennicopter and the Wright Bat, but I was unsure as what to buy. Could someone help me out here because I need to have this thing built by states in NY? Thanks!

None of the existing kits I'm aware of meet the rules unmodified. Both those kits will fly well enough and can be a place to start. The Wright Bat is easiest, Penni Copter probably flys better. See below for a possibly better alternative. Also see below for comments on the rotor that may come with those kits.

<SNIP> I had one more question; should the copter be designed to fly in a climbing turn or fly straight up and down? <SNIP>

Straight up and down works, probably some circling motion will remain. I have a sneaking suspiscion a climbing turn is more efficient (real copters fly better when moving forward than hovering) but I haven't seen it done on this scale.

<SNIP>I think this pretty much rules out using plastic for the props.
The items left are solid balsa prop blades or something built up (like an indoor duration plane).

Anyone disagree? Do you think it needs a clarification?

Thanks.

I know the intent was for the student to make the rotor, not buy it. If the words aren't clear, a clarification is certainly in order. Heck, that's the purpose of trial events, to get these things worked out before team results and state/national invites are on the line.

<SNIP> But I have two questions: 1. How do they weigh the motor? Because there doesn't really seem to be a motor in this design, really, so I was confused. 2. Are the materials they list safe to use without getting in trouble? I know that everything besides the bead are safe, from what I've checked, but I don't really know. Some help would be very nice.

EDIT:
Also, how would one go with making the blade? Would they make them a little bit angled, or just straight, or what? I feel like I won't understand the answer to this, though.

First, that design is a VERY simplified form of the dual rotor concept we've been talking about in this string. It'll fly, probably not very competitive, but a good place to start.

1. In SO competition the motor is weighed before you assemble it onto the copter. In that design its inside the straw so you'd have to weight the motor before putting it in.

2. What do you mean safe to use? Safety safe or SO rules compliance safe?
Safety safe must always in the end be judge by the user/mentor based on skills, experience, etc, but these parts look pretty innocuous.
Rules compliance safe, the straw is pretty dicey, everything else looked OK

Step two describes making the blades. They are pretty simplistic, but will work. My development model from last year used flat blade props similar to this, but probably lighter, and flew 20-30 seconds. About mid-range to reported times. Higher efficiency (and times) will come from using proper helical twist blades for constant angle of attack along the radius, and by curving the blades to a proper airfoil. All very doable.

Jeff Anderson
Livonia, MI

[smartkid222]

Who said solid prop? Not required in the rules...

The rules say that "Helicopters must be constructed only from wood, paper, plastic film covering and glue."
I think this pretty much rules out using plastic for the props.
The items left are solid balsa prop blades or something built up (like an indoor duration plane).

Anyone disagree? Do you think it needs a clarification?

Thanks.

Actually Jander and I were talking about solid balsa props.
thats included in wood
The rules are very clear
i disagree that you need a clarification.

[bchero]

Hey guys. I looked up the Penni Helicopter Kit and found out that there were prebuilt pulleys included in the kit. This poses a problem because the Helicopter Duration rule states that pulleys cannot be used in transmission. What could I do to solve this problem?