Designs and Kits

[carneyf1d]

The climb, cruise, and descent phases are heavily dependent on the rubber you're using. It all comes down to the torque. The way that rubber holds torque is there is an initial high torque, which depletes rapidly (climb), a plateau which lasts quite a while (cruise), and a final slow depletion (descent). Depending on which type of rubber you're using, all three of these phases can change.
Another way you can alter the climb, cruise, and descent phase is through variable pitch props. Building a mechanism might be a little overkill, but you can use the natural flex of a blade to give you an advantage.

This should be the same for Wright Stuff and Helicopter.

[calgoddard]

Thanks Jeff for your reply above.

I now have the official 2011 rules for the HELICOPTERS event.

I have a question about the interpretation of rule 2.d.

What is meant by "a vertical axis" in rule 2.d? Does it have to be perfectly vertical or can it be five degrees off vertical? Does this rule apply only when the helicopter is stationary, and not in flight?

From the videos I have seen, the common rotor axis of the twin counter-rotating co-axial rotor helicopters that competed in the trial event last year does not stay vertical throughout the duration of the flight because the motor stick oscillates back and forth almost forty-five degrees from true vertical, typically during descent.

If the vertical requirement of rule 2.d. does not apply when the helicopter is flying, and only applies when it is stationary, what orientation must the helicopter be in when the "vertical axis" requirement is assessed? Real helicopters often use tilted rotors.

If the "vertical axis" requirement of the 2011 rules is interpreted too narrowly the result may be that students will effectively be limited to one of two designs: 1) Wright Bat; or 2) Parlor Copter. I don't think that was the intention.

Even if that is the case, it will be fun to see how well those known designs can be optimized.

[jander14indoor]

I'm going to give my usual weasal worded answer to questions like this.

This is not an official National SO site, any answers given here have NO binding on anyone anywhere. Anything I say here is an OPINION. If you want an official clarification, go to the national site and ask your question there.

OK, that said, no I don't think the intention is perfectly vertical. But you are right, not much help in the current wording for how much not vertical is OK. Ripe for over/mis-interpretation by event supervisors. I think this IS worthy of an official clarification request to the national.

As to your comments on oscilation, not what I've observed. If properly balanced, the twin rotor designs are pretty stable. At least mine is and many I saw at the national contest. Problem is one of balance, which I suspect includes both rotors AND overall CG vs rotor location. Now, the Wright Bat designs do seem to tip over some and stay that way, and if that went too far (so that the big flat anti torque surface starts acting as a wing!), I would worry about disqualification.

As I said at the start, on this site, these are ONLY opinions.

Jeff Anderson
Livonia, MI

[blue cobra]

How small of a MS can you go before encountering problems with this year's rules (generally- I know each piece is unique)? For WS I used 1/4 x 1/8, which I think was rather small, but it was an exceptional piece so it held up well. I was considering using 3/16 x 1/8 for my first copter, because I think I'm going to be slightly overweight even going that small, but I'm especially worried about bending with greater mass and likely greater thickness of rubber.

Your link doesn't work. It seems that the formatting of the url is preventing the forum from recognizing it, so anyone looking to go there should copy and paste the full url. Clicking on it will not work. http://www.a2zcorp.us/store/ProductDeta ... uctID=4562

To fix this problem you can use a url shortener and get http://bit.ly/blNLk8
so Parlor Chopter Kit

Alternatively, DS made a hardurl BBCode:

Code: Select all

[hardurl]http://www.a2zcorp.us/store/ProductDetail.asp?Cguid={4C1E006F-EDBB-4E23-BD81-4F78BEAA8329}&ProductID=4562[/hardurl]

[hardurl]http://www.a2zcorp.us/store/ProductDeta ... uctID=4562[/hardurl]

[jander14indoor]

Motor stick. I just finished designing my demo helicopters for the lecture sessions I give. I've never liked the small motor sticks on WS or for helicopter due to the bending. Small cross section means easier bending, even if you use harder wood. Instead, I tend to go for large cross section, light balsa, medium length.

Example, in my current plan, the weight budget for the motor stick is just at 2.0 gm. That leaves .75 gm for each rotor and .5 gm for hooks, wires, glue, etc. I can hit the .75 gm with 12 lb/ft3 density balsa spars, heavy stuff, and light grocery bag covering. I used 7 lb/ft3 balsa for the sticks, and they come out 1/4 by 3/8 by 11 inches. Stiff. Easily capable of holding a two gm motor without distorting.

Just one approach,

Jeff Anderson
Livonia, MI

[smartkid222]

What do you mean by greater mass?
Yes, I also believe in stiff wood for the motor stick but I think jeff's estimate is still too conservative. I would say that you could go even lower for the motor stick to 1.6g. Of course as long as the entire helicopter is at minimum weight, how you distribute it is up to you.

[GitItWright]

This summer, at the clinic in Indiana, the winning team powered the "bottom" rotor which left the top rotor to have its "hub" fixed. They then attached a "probe", a spear about 8 cm long to the top of the Helicopter. That probe would touch the ceiling first thus preventing the helicopter from clipping its rotor blades on the ceiling. It work very well when flown in a room with a flat ceiling. It did create an "artificial" cruise period for the flight and flew substaintially longer than all others. I would think a tip that was a round surface as opposed to a pointed surface will work best.

So, a strategy note: If you can investigate the expected contest flying site and establish if it has a "smooth" ceiling (or its entire surface is parallel to the floor), consider using a balsa probe. This will require experimentation and the need to consider its mass as part of the anticipated weight schedule for the Helicopter.

BTW, if this subject has been already covered on another thread, post that thread point for others whom may ask.

As Before, Good Luck!

[Kovu]

I am looking at making a helicopter using the Penaud helicopter design but, I am confused how it works I see that one end appears attached while the other is allowed to spin by the rubber band. Can you guys explain this to me.

[lonestar]

I am looking at making a helicopter using the Penaud helicopter design but, I am confused how it works I see that one end appears attached while the other is allowed to spin by the rubber band. Can you guys explain this to me.

Both ends spin, if that's what you're asking. Because it's free to move in the air, the end that's "attached" will, along with the whole body of the helicopter, spin in the direction opposite of the "free" end.

[Kovu]

I understand that they both spin and in different ways but how would you get balance mine seem to just fall in a crumple mess, maybe a diagram could help me.