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Inchs To Degrees
Hi
I want to set the control surfaces on my aircraft more precisely . In many instructions they are given in inchs . Is there a formula to transfer this measurments from inchs to degrees ? Thanks for looking Michel
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05302009, 08:00 AM  #2 
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Re: Inchs To Degrees
cos(a) = 1  (T^2 / 2L^2)
Where: a is the angle in degrees T is the throw in one direction L is the length of the control surface
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05302009, 08:21 AM  #3 
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Re: Inchs To Degrees
I won't dispute Ben's equation but I will say that trying to cross reference would be very difficult. As you get further away from the starting point,lets say that is the hinge line the distance in degrees won't change but the amount or distance in between the up and down or center will.If you put your two hands together and make a V with your two fingers ,depending on how far apart they are (number of degrees) notice at the closest part where the two hands touch you have lets say 1/8" gap but at the tip of the two fingers it is 3/4" and if your fingers where two feet long it could be 2" space. So you see the degree doesn't change but depending on the length of the surface the amount of travel does. Hope that doesn't sound to confussing
Some planes are set up in degrees but that only pertains to said plane
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05302009, 08:33 AM  #4 
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Re: Inchs To Degrees
Ben,
Could you explain your formula in a bit more detail or give an example? I am not sure what the "^" means. Must be some form of new math. Thanks, Chris 
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05302009, 08:52 AM  #6 
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Re: Inchs To Degrees
google search http://www.aeroperfect.com/degree.html ,,,

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05302009, 09:14 AM  #7 
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Re: Inchs To Degrees
Chris, the ^2 means squared.
What I posted was just the law of cosines. Jason's way will get you in the neighbourhood as well, but is technically not as accurate as you can't have a right triangle where the hypotenuse is equal to one of the other sides. In this case, the length of the control surface forms two of the sides of the triangle.
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05302009, 12:08 PM  #8  
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Re: Inchs To Degrees
Quote:
If you angle the ruler, or use a curved deflection meter with linear scale on it, then cosine law would be used.
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05302009, 01:18 PM  #9 
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Re: Inchs To Degrees
I would draw a proportional cross section of the wing and control surface on paper, with centerlines through hinge. Then drawing the deflected control surface, at your inch measurement, also with a centerline, you can lay a clear protractor over top and read the degrees. Just how I would do it, hope this makes sense.
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05302009, 01:59 PM  #10 
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Re: Inchs To Degrees
In the end, the difference is nearly negligible for the purpose.
Say you have a 3" surface with 1" deflection. Using Jason's method, you get 19.5 degrees. Using the cosine law, you get 19.2 degrees. The more throw you have, the bigger the difference becomes, though.
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