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Dihedral rise  This thread currently has 300 views. Print
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JGlassFNP
August 28, 2019, 11:33am Report to Moderator

Wing Man
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Ok I am approaching the time to mock up my wings and as we know there is a 3 degree angle built in the root to allow for the dihedral angle. Now I need to know if I’m doing this right before cutting my metal for my struts and wasting my money. If the wing root and tip were on a level plane, and want to rise 3 degrees over basically 12 foot then how many inches would it be blocked up at the wing tip? I used a right triangle trig calculator that rendered 7.5 inches. Does this sound right? I will post the picture of the calculation. Thanks, James
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radfordc
August 28, 2019, 4:07pm Report to Moderator

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I used this calculator to check and it shows pretty close to what you have:  https://www.inchcalculator.com/rise-run-degrees-calculator/

It actually shows that a rise of 7 5/8" is closer to 3 degrees.  If you can get accuracy to 1/8" you're better than most.
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Bob Daly
August 28, 2019, 4:45pm Report to Moderator
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For small angles the tangent and sine trigonometry functions are equivalent so confusing the two doesn't hurt in this application. For 3° they are 0.05. So for a 139" wing, the tip would be raised 7".  
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Keith103
August 28, 2019, 4:50pm Report to Moderator

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Distance from wing root to tip = 139 inches.
Tan of 3 deg = 0.0524
Rise of wing tip from root = 139 x 0.0524 = 7.2836

I used 7 and 1/4 inches for verifying the dihedral.
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Keith103
August 28, 2019, 4:59pm Report to Moderator

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I used a similar calculation to figure out how much to tilt the top of root rib from vertical.



Attachment: root_rib_tilt_8121.jpg
Size: 120.35 KB

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JGlassFNP
August 28, 2019, 7:51pm Report to Moderator

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Sounds good. I appreciate you guys. James
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Greg Doe
August 28, 2019, 8:42pm Report to Moderator
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Don't worry about it. 6 1/2" or 8 1/2", you will never know the difference.
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mullacharjak
August 30, 2019, 4:04pm Report to Moderator

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Wouldnt this work ?



Attachment: untitled_8157.jpg
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Bob Daly
September 2, 2019, 4:40pm Report to Moderator
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Sure would. And if one determines the position of the strut attachment point on the wing relative to the attachment point on the fuselage or axle one can simply use the Pythagorean theorem (z2 = a2 + b2 + c2) to calculate the precise strut lengths without blocking up the wing at all.  For example, the Himax main wing strut attach point is 1.37" behind the fuselage strut point (the strut angles slightly aft) and 38.47" above it and 63.38" out. These distances can all be determined from the plans. Then the strut length is 74.15" plus the necessary bolt hole edge distances. The same procedure will produce the rear strut length.
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