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Homework Help: Calculating Flexural Rigidity across span of guitar soundboard

  1. Mar 28, 2014 #1
    1. The problem statement, all variables and given/known data

    I am trying to calculate the flexural rigidity across the span of a guitar soundboard.

    The soundboard is comprised of a number of struts, the shape of which can be approximated to a triangular section sitting on a rectangular section. This makes for straightforward calculation of the second moment of area.



    I can see how to calculate the flexural rigidity of each soundboard-brace section: by finding the overall second moment of area of the section (using parallel axis theorem) and then multiplying this by the Young's Modulus (E). (In this case, a standard value for the material in question - Spruce at 10GPa).

    What I can not see how to do is to find the overall flexural rigidity across a span of the soundboard.

    I'd be very grateful if anyone could tell me how to approach this.

    2. Relevant equations

    Parallel Axis Theorem:
    [tex]I_{AB} = I_C + l^2 A[/tex]

    [tex]Flexural Rigidity = EI[/tex]
    Last edited by a moderator: Mar 30, 2014
  2. jcsd
  3. Mar 28, 2014 #2


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    Sorry, right clicking doesn't show any images.
  4. Mar 28, 2014 #3
    I think you have to select "show image in new tab" and it should work...
  5. Mar 28, 2014 #4


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    Sorry, t'aint nothin' there to click on.

    Have you tried to contact a moderator about helping you to attach an image file?
  6. Mar 28, 2014 #5
    Oh, cheers for letting me know! I'll see if I can contact a moderator...
  7. Mar 30, 2014 #6


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    I changed the [ IMG ] tags to [ url ] tags because it's a url rather than an image link.

    The links now seem to work.
  8. Mar 30, 2014 #7
    Thanks a lot Astronuc. I'll bear that in mind for future posts.
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