Helicopter B/C [Trial]

Gujju Builder
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Re: Helicopter B/C [Trial]

Postby Gujju Builder » May 7th, 2010, 6:36 pm

:!: :?: What parts do u need to build a regular helicopter. We dont know what to buy?????!?!?!?!?!?!? Are there any plans. :o :shock: :!: :?: :?: :?:

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lllazar
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Re: Helicopter B/C [Trial]

Postby lllazar » May 7th, 2010, 10:47 pm

:!: :?: What parts do u need to build a regular helicopter. We dont know what to buy?????!?!?!?!?!?!? Are there any plans. :o :shock: :!: :?: :?: :?:
Is this for nats?

ON topic, read this thread, there are a lot of basic design ideas floating around, seeing as i think your new to this.
2011 Season Events~

Fossils (Regionals ~1st) (State ~6th)
Towers (Regionals ~1st) (State ~3rd)
Helicopter (Regionals -3rd gahhh) (State ~5th)
Wind Power (Regionals ~1st) (State ~3rd TIERED!)

Hooray for getting everything i wanted?

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Re: Helicopter B/C [Trial]

Postby red_moon » May 11th, 2010, 7:42 am

Right now, I'm working on our rotors, and I read Jander's post about the helical blades, and the way I understood it, if the rotor is larger, the angle of the end is still 17.6 degrees, based on that cylinder visual. I doubt this is right, and was wondering if someone could clarify (I've spent hours researching).

This brings me to another question: for a helical rotor, the middle is straight up and down (or very nearly?), but do the ends ever exceed 90 degrees from the middle? If, say, the presumed angle of the end is 17.6 degrees, would the total twist of the rotor be something like 144.8 degrees (or 72.4 on each side)?

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Re: Helicopter B/C [Trial]

Postby jander14indoor » May 11th, 2010, 11:50 am

Dang a hard one. If you look back a ways on this thread I think you'll find pointers to propellor theory in case I get lost with this explanation.

Yep, here's one: http://www.gregorie.org/freeflight/shee ... index.html

Spend some time understanding that if you haven't already.

Answering some of your specific questions. I'm not sure where you got 17.6 degrees for the tip, this is only correct for one pitch/diameter ratio, not in general. Yes, near the hub the blade ideal angle approaches being parallel to the rotor axis (straight up and down). No the tips never quite reach 90 degrees from the middle. They get closer as the blade gets longer, but never reach it.

I'm going to stop with that for now because the existing explanations are better than what I can write. If that didn't cover what is confusing you, holler and I'll look up a reference to copy with some diagrams.

Jeff Anderson
Livonia, MI

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Re: Helicopter B/C [Trial]

Postby red_moon » May 11th, 2010, 2:00 pm

God, I'm stupid. I took one look at the picture and finally realized what you meant...haha, I guess I'm just a visual person.

Thanks!

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Re: Helicopter B/C [Trial]

Postby jander14indoor » May 11th, 2010, 6:10 pm

NOT stupid. I'm not sure I've ever seen it explained adequately without a picture, trick is has to be the right one to talk to YOU.

And its amazing how hard some subjects seem until you the last clue finally fits in place and makes large amounts of stuff just fit. I'm an engineer, strongly mathematically oriented since elementary school. Breezed through math till I got to calculus in high school. Then bang, while I could do the work by the rules, but it just made no sense because I just didn't get limits. Then one day years later in college, think it was during a physics class, BANG again, it just all made sense. Different explanation, different example. Years of math just fit and I could work from basic principles and solve problems without having a set method.

And it wasn't just once in my life, many times.

Jeff Anderson
Livonia, MI

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Re: Helicopter B/C [Trial]

Postby OlympiadLover » May 15th, 2010, 3:21 pm

It states that the helicopter must be build from wood, paper, and plastic covering, but I saw a few designs with a plastic cups. Is that ok?
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Re: Helicopter B/C [Trial]

Postby jander14indoor » May 16th, 2010, 3:48 am

Illinois specifically varied from the national rule to allow plastic props. There is no national clarification allowing such a prop, so I'd say no.

Jeff Anderson
Livonia, MI

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Re: Helicopter B/C [Trial]

Postby gcruz24 » May 18th, 2010, 6:42 pm

my partner and i worked on a design with the props made out of solid balsa 45 degree angle it weigh 7 grams the thing is it flies but it doesn't last long we have the power but not the duration using very thick rubber help please!!!!!!!!!!ASAP

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Re: Helicopter B/C [Trial]

Postby jander14indoor » May 19th, 2010, 3:47 am

Start by losing 3 grams FAST. Like Wright Stuff (or any flying event where duration wins) weight is critical and ALWAYS bad.

Possible ways. Can you thin your motor stick some. Same question for the blades. How hard would it be to replace the solid blades with a frame covered by light tissue? How hard to replace the blades with lighter balsa? Cut holes in the existing blades so only say 25% of the wood is left and cover holes on one side only with light tissue or light plastic covering like Wright Stuff planes.

Jeff Anderson
Livonia, MI


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