Rotors

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VeritasEnVida
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Re: Rotors

Post by VeritasEnVida » October 24th, 2011, 1:33 pm

Very nice, also I used rubber lube as a last second improvision to reduce friction with the rotor, worked like a charm. There are a lot of lubricants out there is there any you think would work well with helis? Also other tips common guys make these helicopters fly longer than last years nationsl
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Re: Rotors

Post by Lily Essence » October 27th, 2011, 7:19 pm

Chalker, with the rules about that 3x bonus on "chinook style" helicopters, they don't need to be straight side by side to receive the bonus, correct?

Like, if the axises (is that a word?) are skew lines or at 90 degrees from each other, would I still get the bonus?

Thanks for answering!
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Re: Rotors

Post by wlsguy » October 27th, 2011, 7:27 pm

Lily Essence wrote:Chalker, with the rules about that 3x bonus on "chinook style" helicopters, they don't need to be straight side by side to receive the bonus, correct?

Like, if the axises (is that a word?) are skew lines or at 90 degrees from each other, would I still get the bonus?

Thanks for answering!
I'm not Chalker7 but you should probably submit a clarification. It seems many people are asking the same question.

When I read the rules I see the rotors are defined as " ... surfaces that contribute lift by rotating on a common path around a vertical axis".
If the axis are not vertical, they are not rotors.

but, again, submit a clarification. Hopefully the answer will get added to the FAQs (hint, hint, ;) )

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Re: Rotors

Post by chalker7 » October 27th, 2011, 7:32 pm

Lily Essence wrote:Chalker, with the rules about that 3x bonus on "chinook style" helicopters, they don't need to be straight side by side to receive the bonus, correct?

Like, if the axises (is that a word?) are skew lines or at 90 degrees from each other, would I still get the bonus?

Thanks for answering!
We can't answer clarifications like that here, they have to go through the official soinc.org site. We have gotten this exact question several times there, but I'm not sure when they will be posted. If you are impatient, you can submit the question again on your own. A hint to the answer is carefully read 3.d, definition of a rotor.
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Re: Rotors

Post by illusionist » October 28th, 2011, 12:59 pm

Referring back to the elliptical shaped rotors, is there a specific kind of Balsa grain that would make things easier? Last year I tried it with 1/16 x 1/16 balsa and it didn't go too well. Is the best technique to place them in the bath tub with hot water, or to pressure cook them, or use steam from an iron? (I've heard all of these before)

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Re: Rotors

Post by chalker7 » October 28th, 2011, 8:30 pm

illusionist wrote:Referring back to the elliptical shaped rotors, is there a specific kind of Balsa grain that would make things easier? Last year I tried it with 1/16 x 1/16 balsa and it didn't go too well. Is the best technique to place them in the bath tub with hot water, or to pressure cook them, or use steam from an iron? (I've heard all of these before)
1/16" square is too big to bend around the tight turns required for these size helicopters/rotors. I would use 1/32" square sticks stripped off of a sheet. You don't need to worry about strength too much with these parts because there will be a large center rotor shaft that supports the frame (see the links I posted earlier for details on that).

I soak them in water and use a form/jig for the elliptical shape. An important consideration is that balsa wood is less likely to break/kink if it is under tension, so tape one end down, pull on the loose end while wrapping it around the form and tape the other end down, then let it dry overnight. That may take a few practice sessions to get down.

The tighter the radius that you are trying to bend, the more likely you are to break the stick, so if you keep breaking things you might want to make a blunter tip. Also, the smaller the cross-sectional area of the wood, the easier it is to bend (1/16" square has 4 times the cross section of 1/32" square, so 1/32" is much less likely to break or kink), so definitely put extra effort into making thinner strips.
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Re: Rotors

Post by jander14indoor » October 29th, 2011, 4:29 am

IF you find you need more strength for the outline you can bend 1/16 by 1/32 the thin way as easy as 1/32 square. IF still more needed, you can laminate two 1/16 by 1/32, though here you really have to start watching weight.

Alternatively, you could use sheet blades. One popular airplane event, penny plane, typically has 12 inch diameter propellers formed on a block from 1/32 sheet balsa. Weight around .8 gm. Scaled up to 35 cm, should still be able to keep under 1 gm for each rotor. Look around the web for instructions.

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Re: Rotors

Post by kentuckyfan1001 » December 26th, 2011, 8:06 pm

Hey, does anyone know what the ideal motor stick length that would balance coaxial rotors effectively while giving a good length for the rubber motor?

It seems as though optimizing the motor stick length can play a great deal in the times that teams have been getting.
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Re: Rotors

Post by mrsteven » December 27th, 2011, 3:51 pm

Lily Essence wrote:Chalker, with the rules about that 3x bonus on "chinook style" helicopters, they don't need to be straight side by side to receive the bonus, correct?

Like, if the axises (is that a word?) are skew lines or at 90 degrees from each other, would I still get the bonus?

Thanks for answering!
Although Im not Chalker, if your talking about placing a rotor 90 degrees from the vertical rotor that would not count. Rotors are defined in the rules as contributing to upwards movement (simplified, I dont have the specific rules in front of me)
having a rotor on its side wouldnt count b.c it doesnt assist upwards motion.

so the clique actual helicopter design with the small side rotor in back for stabilization wouldnt count towards the multiplier, nor count at all as a rotor.
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Re: Rotors

Post by chalker7 » December 28th, 2011, 6:46 am

mrsteven wrote:
Lily Essence wrote:Chalker, with the rules about that 3x bonus on "chinook style" helicopters, they don't need to be straight side by side to receive the bonus, correct?

Like, if the axises (is that a word?) are skew lines or at 90 degrees from each other, would I still get the bonus?

Thanks for answering!
Although Im not Chalker, if your talking about placing a rotor 90 degrees from the vertical rotor that would not count. Rotors are defined in the rules as contributing to upwards movement (simplified, I dont have the specific rules in front of me)
having a rotor on its side wouldnt count b.c it doesnt assist upwards motion.

so the clique actual helicopter design with the small side rotor in back for stabilization wouldnt count towards the multiplier, nor count at all as a rotor.
An official answer to this question was posted some time ago on the Science Olympiad website. Here's a link: http://soinc.org/node/295
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