Wing attachment angles

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imamac96

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May 10, 2018
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North Texas / South Bay
I’m not sure where to put this, but it seems like it should go in general design. I can’t find the answer using the search box and this has been over the course of about a week. Perhaps I don’t have the right keywords.

The Zenith and Thatcher center section spars are square at the end, and the outboard spars have a slight angle at the inboard side to accommodate the dihedral. Why is it this combination (A)? Why do we not instead leave the outboard spars square and taper the inboard (B)? Smaller parts are easier to work with and less expensive to replace if we make a mistake.

I cannot yet see how there is a significant structural difference between the two styles. Am I missing something huge here?
 

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Floydr92

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Aug 13, 2013
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Scotland
For 'A' the outer spar would have to be thinner than the inner spar.
For 'B' the inner spar would have to be thinner than the outer spar.

'B' is thus a bad idea as the inboard section sees higher load.

to maintain a consistent spar height/section size, the angle would have to be the same on both mating ends.
 

wsimpso1

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Oct 18, 2003
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Saline Michigan
If the outboard portion is the same in both cases, the inboard portion is deeper in A, which allows a lighter inboard spar when designed to same strength.
 

Marc W

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Mar 31, 2017
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950
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Colorado
Inboard and outboard spar ends are square on the Thatcher. The top attach brackets are shorter than the bottom brackets in order to set dihedral.
 
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