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-   -   how to modify rib profiles when changing wing (https://www.rcuniverse.com/forum/scratch-building-aircraft-design-3d-cad-174/1504126-how-modify-rib-profiles-when-changing-wing.html)

pahtreek 02-06-2004 08:52 PM

how to modify rib profiles when changing wing
 
Is there an easy way to adjust the rib profiles when changing the wing outline? My friend and I are thinking about blowing up some corsair plans and modifying the wing outline to be a little more scale. What is the easiest way to make sure the ribs are correct? I know how to draft and I have Microstation, Autocad and solid works, but I am trying to avoid a lot of sanding/cutting the tops of the ribs once the wing is framed up. I guess I could draw points on each rib that are the same height, then when I elongate or shorten the ribs make sure the new heights are the same at those points.....but there must be a "known way" of doing it.

Thanks for any input given!

Tall Paul 02-06-2004 11:37 PM

RE: how to modify rib profiles when changing wing
 
Measure each rib's position on the wing out the span.
Find the length of the chord at each position, and scale that to the root chord.
Find the percentage difference in chord length, IOW.
Have the CAD program draw each rib to the scale percentage for each chord, in both x and y.
The variation along the wing will then be consistent.

CoosBayLumber 02-06-2004 11:50 PM

RE: how to modify rib profiles when changing wing
 
There is an assumption that the same airfoil is constant and proportional the entire length of the wing. This will work in CAD, but I don't always find this to be true. Many A/C manufacturers used a certain airfoil near the root, and blended to a different one near the tip.

The many airfoil software programs have a function to not only alter the blending of the airfoils, but also calculate the overall rib according to chord length then.

Wm.


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