Helicopters C

[vjindal]

Dave is taking preorders at this time by email only for delivery in about a month. His website will not be up until the end of Oct or early Nov.

His helicopter is a Sikorsky in the fact that it has 2 rotors that are not coaxial. It is a wild design! Both rotors are pushers. The rotors should be easier to build this year, but the kit has a good bit of "cables" which some might have a bit of a problem with. He told me that he has had 2:30 times in an 8 foot ceiling and that it is very stable.
Each rotor has its own rubber band. My thought is that it will either take 2 torque meters, or one with a board to transfer the wound motor to until it can be loaded on the chopper. It will be interesting to see what his instructions have to say.

Is that 2:30 after the bonus (1 min actual time)?

[Unome]

Dave is taking preorders at this time by email only for delivery in about a month. His website will not be up until the end of Oct or early Nov.

His helicopter is a Sikorsky in the fact that it has 2 rotors that are not coaxial. It is a wild design! Both rotors are pushers. The rotors should be easier to build this year, but the kit has a good bit of "cables" which some might have a bit of a problem with. He told me that he has had 2:30 times in an 8 foot ceiling and that it is very stable.
Each rotor has its own rubber band. My thought is that it will either take 2 torque meters, or one with a board to transfer the wound motor to until it can be loaded on the chopper. It will be interesting to see what his instructions have to say.

Is that 2:30 after the bonus (1 min actual time)?

Probably 2:30 pre-bonus, based on some of the flights by people using his kit. After the bonus, scores are reaching 6 minutes or more.

[coachchuckaahs]

So I'm trying to color the mylar with sharpie before I put them on the rotors and they keep ripping. :/ Is there a better way to color the mylar so that it doesn't rip? :/ Thanks in advance!

We colored with a super large sharpie, AFTER covering the rotor. We laid it on a roll of paper towels to carefully support as we colored. Had to roll it over the paper towels as we progressed in coloring.

Alternatively, could color by stretching it smooth on a table or board. Use chapstick around edge, carefully stretch till flat. Then carefully mark it. We used this approach in Wright Stuff. Marking prior means marking more, more risk of damage. However, marking on the rotor means damage must be rebuilt/replaced.

Chuck

[tivikings]

We had a last minute adjustment to our team and I'm now building the helicopter. It's too late for us to get a kit, can anyone point me to some basic balsa wood models/plans?

We aren't in a super competitive division so if we can get a copter to fly we'll consider it a success. Thanks in advance.

[Unome]

We had a last minute adjustment to our team and I'm now building the helicopter. It's too late for us to get a kit, can anyone point me to some basic balsa wood models/plans?

We aren't in a super competitive division so if we can get a copter to fly we'll consider it a success. Thanks in advance.

Do you have rubber? Do you have any of the other specialized parts? (e.g. the bearings or such that attach the rubber to the rotors)

[jander14indoor]

Plans are on the internet for simple helicopters, you'll need to adjust to fit this years rules.
Here's a couple:
https://paksc.org/pk/science-experiment ... elicopter/
http://www.minnesotaso.org/Files/Helico ... 02010.pptx
https://www.smusd.org/cms/lib/CA0100080 ... rs%20C.pdf
https://scioly.org/gallery/displayimage ... 2&pid=2885
https://www.youtube.com/watch?v=xsGwOCiREBU
https://www.sciencenc.com/resources/hig ... licopters/
etc...

Jeff Anderson
Livonia, MI

[Wabbit]

So, I've been doing helicopters for two years now and have gone through numerous iterations of my own designs, yet I feel like I must be missing some fundamental piece of the puzzle and was hoping someone here could help me out.

For context, my state banned the use of kits this year. I'm generally in support of the policy, since, at least to me, the thing that makes helicopters fun is coming up with your own designs. This means that getting one of the Freedom Flight Models kits is off the table for me as an option, but since the ban isn't in effect for most of the country, it can be hard to find solid advice on how to build a good helicopter from scratch.

Feeling like it would be too difficult to build a chinook, especially without a kit or set of plans to go off of, and knowing that other teams in my state also will have trouble utilizing the bonus due to the ban, I decided to go with a more standard design this year. So far, despite getting my helicopter to be super lightweight (just over 3.0 g), I haven't been able to do much better than about 45-50 second flight times. The most obvious reason for this is that I haven't been able to put more than roughly 300 total winds in my motor. This is an obvious difference between my design and some of the better ones from last year which, if I'm not mistaken, were using upwards of 1500 winds. The other main difference between my designs and objectively better ones is that my frame is significantly shorter, probably only about 30 cm long instead of what appeared to be closer to 90 cm long frames that were being used by the kits from last year.

So, then, the fix should be obvious to me, right? I make a much longer frame which allows me to use a much longer rubber band thereby allowing me to put in many more winds. But this hasn't worked. Every time I try to go with a longer rubber band, a larger frame, or both, I end up getting much shorter flight times. I would imagine this is due to the helicopter as a whole weighing significantly more. Even if I manage to keep the frame lightweight, the added length of the rubber motor makes the whole thing a lot heavier. I've experimented with every possible combination of sizes, and, using my current rotors, the thing that has worked the best is a super small frame with a relatively short rubber band. But I know from seeing other teams at competitions that this sort of design isn't supposed to yield good results, nor has it yet been able to replicate the times of even moderately good teams.

So I guess my question is, what were the kits from last year doing differently? How was it that they were able to use such a long rubber motor and such a large frame without the whole thing weighing way too much?

Thanks for your help!

[Raleway]

So, I've been doing helicopters for two years now and have gone through numerous iterations of my own designs, yet I feel like I must be missing some fundamental piece of the puzzle and was hoping someone here could help me out.

For context, my state banned the use of kits this year. I'm generally in support of the policy, since, at least to me, the thing that makes helicopters fun is coming up with your own designs. This means that getting one of the Freedom Flight Models kits is off the table for me as an option, but since the ban isn't in effect for most of the country, it can be hard to find solid advice on how to build a good helicopter from scratch.

Feeling like it would be too difficult to build a chinook, especially without a kit or set of plans to go off of, and knowing that other teams in my state also will have trouble utilizing the bonus due to the ban, I decided to go with a more standard design this year. So far, despite getting my helicopter to be super lightweight (just over 3.0 g), I haven't been able to do much better than about 45-50 second flight times. The most obvious reason for this is that I haven't been able to put more than roughly 300 total winds in my motor. This is an obvious difference between my design and some of the better ones from last year which, if I'm not mistaken, were using upwards of 1500 winds. The other main difference between my designs and objectively better ones is that my frame is significantly shorter, probably only about 30 cm long instead of what appeared to be closer to 90 cm long frames that were being used by the kits from last year.

So, then, the fix should be obvious to me, right? I make a much longer frame which allows me to use a much longer rubber band thereby allowing me to put in many more winds. But this hasn't worked. Every time I try to go with a longer rubber band, a larger frame, or both, I end up getting much shorter flight times. I would imagine this is due to the helicopter as a whole weighing significantly more. Even if I manage to keep the frame lightweight, the added length of the rubber motor makes the whole thing a lot heavier. I've experimented with every possible combination of sizes, and, using my current rotors, the thing that has worked the best is a super small frame with a relatively short rubber band. But I know from seeing other teams at competitions that this sort of design isn't supposed to yield good results, nor has it yet been able to replicate the times of even moderately good teams.

So I guess my question is, what were the kits from last year doing differently? How was it that they were able to use such a long rubber motor and such a large frame without the whole thing weighing way too much?

Thanks for your help!

First off, it seems weird that only a state would ban kits but if that's the case, you can still draw inspiration from a kit and even shooting emails to Dave would be helpful since he's such a nice and helpful guy. You can definitely build a competitive helicopter without a kit (we just used pictures and guestimated before) but exploring options and following basic concepts of physics would be immensely useful (like torque, aerodynamics, flight physics, etc.)

For the rubber, we determined last year that after a certain length, a longer motor stick with more winds actually doesn't really help you much. It probably has something to do with the fact that the longer it is that the cutoff line for torque vs winds graph is much higher due to the longer distance apart and then the weight counterbalances any other advantage you might get. You would be surprised at how many winds you can get out of a rubber safely (I discovered that myself by breaking a rubber and getting a nasty mark for a week but it was worth it; I don't encourage it but sometimes reality needs to be tested). And also since you don't have a kit build quality is exponentially more important.

Best of luck!

[Rêveur]

Hi all.

I had a couple of questions regarding the rubber motors and winding. I'm having increasingly frustrating problems with my rubber motors breaking after being used only one or twice

Right now I'm using a 15:1 winder to wind my rubber. I am seeing other teams use 10:1 geared winders, however. Is there a significant benefit to using a smaller geared ratio? Possibly something about winding the rubber more slowly?

I'm also confused as to what lubricant to use. I've bought the "Armor All Original Protectant" but I suspect it might be eating away at my rubber motors, which only seem to last one or two flights before breaking. Can anyone give me any advice on this?

[JasperKota]

Hi all.

I had a couple of questions regarding the rubber motors and winding. I'm having increasingly frustrating problems with my rubber motors breaking after being used only one or twice

Right now I'm using a 15:1 winder to wind my rubber. I am seeing other teams use 10:1 geared winders, however. Is there a significant benefit to using a smaller geared ratio? Possibly something about winding the rubber more slowly?

I'm also confused as to what lubricant to use. I've bought the "Armor All Original Protectant" but I suspect it might be eating away at my rubber motors, which only seem to last one or two flights before breaking. Can anyone give me any advice on this?

How much are you winding? Are you stretch winding?

The rubber should also be stretched at LEAST 7 times is original length when winding, but stretching out even longer will help you pack in turns tighter, especially after you have wound the motor 3-5 times...

I've used Armor All Original Protectant and it has worked very well for me, also make sure you're re-lubricating after each hard wind flight.