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Re: Helicopters B

Posted: February 6th, 2013, 3:24 pm
by rmp509
Thank You! i started testing :D
jander14indoor wrote:Your first sentence is wrong. Has NOTHING to do with stretch or length on the motor stick. I'm talking about the length of the rubber loop itself.

A shorter motor of the same width will have less turns than the longer motor, but the SAME power.

A fatter motor of the same length will have less turns, but MORE power.

Whether it runs out faster actually depends on the rotors.

Note, when I'm talking turns I'm talking max turns to breaking a given motor. NOT what you wound on.

Go try some of the tests I mentioned, you'll learn a lot and it will make more sense because it is your experience then, not my words, however correct they may be. Or may NOT be, in science, while you have to have a level of trust, a level of healthy skepticism is important too. I'm not trying to mislead you or anything, just questioning the experts when data differs from theory is important.

Jeff Anderson
Livonia, MI

PS, those times are pretty good, its time to attack these advanced concepts if you intend to improve more.

Re: Helicopters B

Posted: February 6th, 2013, 7:29 pm
by jander14indoor
Had another thought. When I say torque meter to measure rubber twist force, is that clear?

We talked about it last year and in the past with Wright Stuff, so you can look it up in the archives. But if it needs more discussion, ask away. And not just you rmp509, anyone in the audience.

Its a pretty important tool as you advance in this event. You can fly well without it, but to get the last bit of oomph out of your rubber and absolutely maximize your time it becomes more important.

Jeff Anderson
Livonia, MI

Re: Helicopters B

Posted: February 7th, 2013, 12:24 pm
by Itsanthonguise
Do you guys have any general mods to make on a helicopter besides the rubber?

Re: Helicopters B

Posted: February 11th, 2013, 1:12 pm
by gmui
What percentage of winds left on the helicopter after flight would be considered a good amount? I'm assuming a dead stick landing (i.e. no winds left) is too little and too many could mean something needing a different matched motor for the weight. But is there an appropriate number of winds left?

I guess it also depends on max / ceiling height?

Re: Helicopters B

Posted: February 12th, 2013, 8:48 am
by retired1
In the past, we have been competitive with 5 to 10% of the total winds left. One kit builder says that is too much and that I should shorten the band which will reduce the weight and use more of the winds. Since breaking point of the rubber is in the area of 100 winds per inch, shorter rubber means less winds.
Too wide a rubber means that you get to the ceiling very fast. Some choppers wobble like mad at the high power for several seconds.
Uniformity of the rotors is a major part of finding what will work best for you.
Light weight is always good, till it becomes too fragile. This allows you to use more of the winds.

Re: Helicopters B

Posted: February 12th, 2013, 3:57 pm
by 2017Kortman
Hey, does anyone have a design for a helicopter that works really well? Because we need "300% improvement" if we want to get to nationals this year. :cry:

Re: Helicopters B

Posted: February 12th, 2013, 9:39 pm
by mrsteven
"design," not really. Alot of this event comes down to your skill in fine details to get everything exactly in place. Another huge chunk of it is matching the rubber width and length to the helicopter you have. No two helicopters you make, even with identical plans, will be the same.

If you're looking for a general design, look through the image gallery. The parlor helicopter style is very popular. Its successful and more simply to build than an elliptical bladed helicopter (parlor is heliptical). The major differences between them are the "boxy" type blades VS the "egg" type blades. In theory, the elliptical design is more efficient and works better but it requires a HUGE amount of skill to make them correctly such that it gets a positive effect.

If you want a challenge, that is the way I would go. It is definitely interesting, but matching pitch to surface area and getting everything balanced with surface area proved more difficult of a task than I was up to the last couple years.

If you don't already have great modelling skills from prior experience/events, then the elliptical may prove difficult, but I would start on the heliptical front, if you can build/test/refine one of those, then you probably have the base skills needed to bump up to the next level. But I certainly did great with heliptical both years.

Re: Helicopters B

Posted: February 17th, 2013, 3:42 pm
by rmp509
Would putting two o rings on the rubber ( one on top one on bottom ) allow more turns on the rubber without it snapping? I don't wanna break my helicopter :lol:

Re: Helicopters B

Posted: February 18th, 2013, 6:44 am
by chalker7
rmp509 wrote:Would putting two o rings on the rubber ( one on top one on bottom ) allow more turns on the rubber without it snapping? I don't wanna break my helicopter :lol:
O-rings don't let you wind the motor any further, the number of turns you can get on any fixed size, brand and batch of rubber is the same. However, o-rings do allow you to keep more of the turns you put on. That is to say, when you take the motor off of your winder, you don't need to pinch one end and let the turns loose so you can hook onto the motor hook. The o-ring stays stiff and provides a loop for you to latch onto.

Re: Helicopters B

Posted: February 18th, 2013, 4:03 pm
by NerdGirl314
Is it better to have a longer motor stick (or fuselage whatever you want to call it) or shorter motor stick? My partner and I have been making ours around 26-28 cm long. I started thinking maybe it would be easier to make it shorter so that when the rubber band is wound, it wouldn't have to be stretched any further. Any suggestions?