Calculating Flexural Rigidity across span of guitar soundboard

1. Mar 28, 2014

jellicorse

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.

Diagrams

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:
$$I_{AB} = I_C + l^2 A$$

$$Flexural Rigidity = EI$$

Last edited by a moderator: Mar 30, 2014
2. Mar 28, 2014

SteamKing

Staff Emeritus
Sorry, right clicking doesn't show any images.

3. Mar 28, 2014

jellicorse

I think you have to select "show image in new tab" and it should work...

4. Mar 28, 2014

SteamKing

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

Have you tried to contact a moderator about helping you to attach an image file?

5. Mar 28, 2014

jellicorse

Oh, cheers for letting me know! I'll see if I can contact a moderator...

6. Mar 30, 2014

Astronuc

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

The links now seem to work.

7. Mar 30, 2014

jellicorse

Thanks a lot Astronuc. I'll bear that in mind for future posts.