Helicopters B

[SOCoach]

hogger,

Thanks for the reply. We haven't noticed any wobbling or distortion in the rotor by not using the straw (we did glue a small piece of balsa wood next to the wire for support). I figured the straws on silicone spray or WD40 would be the same size but can't seem to find straws that size without buying a whole lot of spray.

Thanks for those other sources of rubber - I'll try those. My students seem to go through a lot of motors lately.

[TrueshotBarrage]

Thank you all for these replies! Even though our helicopter broke (at 11:00 PM the day before), the tips on the wings and other things helped us do really well in Rotor Egg Drop! I have also learned a valuable lesson today: I should have brought a backup helicopter just in case ours didn't work.

[chalker7]

Just a general FYI, there are only two original sources of model airplane grade rubber in the country.

FAI Model Supply is the primary source and essentially every other vendor is selling repackaged and rebranded (and occasionally restripped for custom thickness) FAI Tan II or Super Sport rubber. Buying in bulk from their website is almost certainly cheaper, but you can only get the newest batches of Super Sport from them and only in a small handful of specific sizes. Tan II was an older formulation that most high-level indoor flyers consider to be superior, but as it is no longer available new, prices tend to be extremely high for verified batches.

A2Z corp resells FAI rubber, but they also found a source for their own formulation. This is known as "Tru-torque" rubber on their website. It doesn't have the energy density of FAI rubber so it probably isn't suitable for high-end competition, but is significantly cheaper and might be a good option for early testing or if there are tight budget concerns. I am not aware of anyone that resells tru-torque rubber.

[FenderBender87]

This is my first year of Science Olympiad and I need help. My helicopter is far too heavy I think at 9 grams and I am having trouble generating lift. I am not using a kit, it is homemade. Any suggestions for cutting down the weight and getting lift? Regionals is on Saturday so I am starting to panic, I got three days left of building. Any help is greatly appreciated.

[ThatRoboGuy]

This is my first year of Science Olympiad and I NEED help, my helicopter won't fly. I watched the Kelly Fair North Carolina Science Olympiad videos and I thought I had it down, but regionals are on Saturday and I am freaking out. It is around 11 inches long, and 1 inch wide. I used tissue paper for my wings which are 4.25 inches by 2.25 inches. It is 9 grams, which is that too much? If so please give suggestions to cut the weight down. I used the lightest balsa I could find. The angle of the blades are around 45°, is that right? All I want is a helicopter that flies. My helicopter also is very brittle. PLEASE GIVE ME ADVICE!

1. Calm. Down. You'll only break your helicopter.
2. Our helicopter weighs about 3.05 grams.
3. Can't understand your description. We use the Freedom Flight kits, methinks. I don't memorize wing angle.
4. You are measuring by inches. All of Science Olympiad is always centimeters.
I don't know where to begin to help you. Picture, maybe?

[jander14indoor]

This is my first year of Science Olympiad and I need help. My helicopter is far too heavy I think at 9 grams and I am having trouble generating lift. I am not using a kit, it is homemade. Any suggestions for cutting down the weight and getting lift? Regionals is on Saturday so I am starting to panic, I got three days left of building. Any help is greatly appreciated.

Long run, go back and read this string, the wikis and the archives on helicopter, Wright Stuff, Glider, Bridge, Boom, Tower to learn how to build light, aerodynamics, ect.

Short run, what wood sizes are you using, what type of wood, what density? You HAVE to build to minimum weight in the flying events to succeed. Yes they are more fragile that way, but they actually break LESS because they fly slower and crash with MUCH less energy.

I generally start my coaching sessions with the following rules:
1. You must build as light as the rules allow to succeed.
2. Make sure your airplane/glider/helicopter doesn't weigh any more than it needs to.
3. What didn't you understand about rules 1 and 2?
4. You WILL break your airplane/glider/helicopter, sometimes intentionally to trim it, get over it. Learn to repair quickly and accurately
5. Learn to build FAST, accurately and lightly. Use jigs and patterns for consistency. To succeed you WILL make more than one.

Some suggestions on how to build to weight. You say you think your helicopter is 9 gm, why don't you know? To build to weight you have to plan to build to weight and build to a plan. Make a list of every part that goes into your helicopter (don't forget the glue!). This is called a Bill of Material (BOM). Then figure out what each part weights, figure the density, volume, resulting mass, etc. Add up, if more than 3.0 gm minimum, change part sizes/materials to get down to the minimum weight. Dont' build anything until you have that plan. Now, USE the plan. Prepare your parts, WEIGH them, don't use any that are over OR underweight.

The example in the NC videos is crude, but will fly if you get the weights down. Wood size for the blad outlines should be around 1/16 inch square med density balsa, around 8 lb/ft3. The motor stick should be around 3/16 by 3/8 very light balsa, say 4-5 lb/ft3 11 inch long is fine. Tissue is kind of heavy for covering, it can work, but you can't use as strong of wood for structure. Instead find the lightest/flimsiest grocery bags you can. Look at produce bags. The lightest are far lighter than tissue or plastic wrap. For that NC design 45 degrees is kind of steep, try 30 degrees.

What size rubber are you using? I generally recommend starting at 1/8 wide Tan SuperSport, 15 inch long loop or so. How hard are you winding? Are you lubricating? If you don't regularly break motors you aren't winding hard enough.

Good luck build LIGHT!!!

Jeff Anderson
Livonia, MI

[NASA123]

I am having trouble winging up the rubber motors. For some strange reason, they keep snapping. We are following the instructions in the Freedom Flights instruction packet, (yes the motors are lubricated), but they don't seem to work. We can't get past 420 winds on a 16" long, .140 inch wide Tan SuperSport rubber band. Any ideas?

Also, I was having trouble figuring out the placement of the counterweight on my one bladed rotor design based on the Freedom Flights model. Is keeping it farther out better, or having it closer in more efficient? Does it even matter?

[chalker7]

Could you describe your winding technique beyond what the instructions say? Many of us do not have access to said instructions and it could be useful for you to take a step back to think about how you are handling the motor. What is the ratio of your winder? How fast are you winding? How many times do you wind the motor? What type of lube are you using? What techniques are you using to wind it (stretch, methods of hooking, etc.) .140" rubber is quite thick, I assume you are talking about a 16" loop (~32" strand)?

I'm not sure of how the Freedom Flight kit sets up the counterweight, but essentially the distance from the center to the weight shouldn't matter as long as it is balanced. Having a weight closer will require more mass, while having it further out will require less due to the lever arm length.

I am having trouble winging up the rubber motors. For some strange reason, they keep snapping. We are following the instructions in the Freedom Flights instruction packet, (yes the motors are lubricated), but they don't seem to work. We can't get past 420 winds on a 16" long, .140 inch wide Tan SuperSport rubber band. Any ideas?

Also, I was having trouble figuring out the placement of the counterweight on my one bladed rotor design based on the Freedom Flights model. Is keeping it farther out better, or having it closer in more efficient? Does it even matter?

[steven102938]

Hi,
I was recently researching ways to build a helicopter, is 3d printing a option? I know it will make the helicopter heavier but i only want to print vital parts.
Thanks,

[chalker7]

No, it will be WAY too heavy and much too weak. I have extensive access to a variety of 3D printers at work and have played with using them for helicopter and airplane parts for awhile. I successfully made a few thrust bearings last year, but they broke after only a couple of flights.
Currently I am playing with propellers (very similar to rotors) and have been able to get a 6" prop (~15cm) down to 2.1g. Simply put, that's not going to work for a helicopter.

Hi,
I was recently researching ways to build a helicopter, is 3d printing a option? I know it will make the helicopter heavier but i only want to print vital parts.
Thanks,