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How does the Deuce's Wild! fly?

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mkmilion

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I don't quite understand the phisics of it. I mean compared to a standard model. I understand in a standard model the thrust vector is straight with the CP. I guess I don't understand the canted part.
If someone could explain this in a little more depth. It would be very helpful.
 

jflis

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well, first, there are two principles involved here. None of it all that complex, but quite interesting (at least in *my* mind...)

aside from the *cool* factor, I am assuming that you are asking about the physics behind it. Why and/or *how* it can work. Please correct me if I am wrong.

1) balance and counter-balance. *generally* speaking, if you were to make a rocket with only ONE motor, and it was canted, it would be unstable as there is a sidewards force acting on the bottom of the rocket. *IF*, however, you were to place a second motor, canted in the opposite direction, this sidewards force is cancelled (or balanced) by the second motor. Assuming both motors have identical thrust curves, they will exactly counter (or balance) each other, resulting in a straight flight.

2), the above was speaking generally and didn't take into account a rather interesting *specific* regarding canted motors. To understand the stability of a rocket, you also need to understand the principles of an "Object in Free Fall" An object in free fall (let's ignore atmospheric properties for this discussion) will not rotate or spin unless acted upon. If I were to apply pressure to the object on some point and direction that was NOT at the center of gravity (CG), then the object would begin to rotate (spin) in that direction, and about the center of gravity. HOWEVER, If I were to apply pressure right *at* the center of gravity (or somewhere on its surface along a vector pointing TO the CG), then the object would *move* in the direction that I am pushing, but would *not* rotate or spin. It would remain *stable*

The same consideration can be made in designing rockets with canted motors. If the angle of the motor results in a line (vector) that passes *through* the CG of the rocket, then even if only 1 motor is burning, the rocket will be stable because the motive force will be pushing on the CG. The tendancy would be for the rocket to go off to the side slightly, but would still be pointed up and flying true. The only problem with this "thought experiment" is that as the motor burns it uses up fuel and thus becomes lighter resulting in the CG moving forward so the motor would no longer be pointed at the CG (but the effect is miminal and the larger the model, the less the effect)

To experiment with this principle, take a 12" ruler and (be quick now) place it on your finger at the 5" mark (not balanced) and thrust your hand upward. You will see the ruler spin into the air (you pushed on a point NOT at the CG). Now, balance the ruler at the 6" mark (the CG of the ruler) and thrust your hand upward. You will see that the ruler no longer spins. Not a perfect test as many factors can induce spin, but you will see the effect well enough.

Hope this helps more than it confuses... :)

jim
 

teflonrocketry1

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The two motors are canted toward one another and the horizontal component of the thrust vectors cancel each another out. The vertical component of the thrust is Cos 15 degrees where 15 degrees is the angle of the motor's cant from vertical or about 96.6% of the vertical thrust. Any mismatch in the horizontal component of the motor thrusts is compensated for by the large surface area of the Deuce's fins.

Hope this helps,

Bruce S. Levison, NAR #69055
 

mkmilion

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I personally was curious. I didn't really put much thought into it until my g/f's dad asked how it flew. I never got into the depth of the rocket, because I figure Jim tested, it worked, he kitted it, now I can fly it.
Don't get me wrong though I appreciate the knowledge you shared with me. I just can't wait to explain it to him.
 

sandman

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Yer all nuts!

It's MAGIC!

sandman
 

mkmilion

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I basically thinks happy thoughts X 2, and flies off the pad?
 

astronboy

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Dont' forget to click your slide rule three times!! :D
 

jflis

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we've got you now, my pretty!

And your little motors, toto too!
 

slim_t

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Originally posted by sandman


It's MAGIC!

sandman
LOL! I wish that had worked for me in all those engineering classes. Magic! Actually, I use that answer alot more now that I'm not getting graded.

I was going to help answer the question, but Jim did such a good job that I couldn't think of anything to add.


Tim
 

SwingWing

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Does the Pixie dust ever need replinishment? Or does it just work forever?:rolleyes:
 

wwattles

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I thought you were supposed to kiss it for luck? Although some rockets I've built didn't exactly look "kissable," with "ROCK" being the operative part of their appearance.

WW
 
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