Determining Panel Mass on Target Plat Thickness Chart

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John Greenlaw
Wandoo
Posts: 13
Joined: Wed Sep 12, 2018 6:23 am

Determining Panel Mass on Target Plat Thickness Chart

Post by John Greenlaw » Thu Sep 13, 2018 11:37 pm

Hello everyone!

I am new to this forum and am very excited about it! I live in Saskatchewan, Canada and starting a 7th acoustic guitar. I have journeyed completely through Trevor's design book four times now and it's an absolute pleasure!

Does anyone know the formula for determining panel mass on the guitar that is being built? I got the excel sheet worked out to calculate panel thickness but could not find the formula to calculate panel mass.

Also, are there any parameters I should change, maybe the vibrational stiffness value (f), when using Honduran Mahogany for the top?

Cheers,

John

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Trevor Gore
Blackwood
Posts: 1365
Joined: Mon Jun 20, 2011 8:11 pm

Re: Determining Panel Mass on Target Plat Thickness Chart

Post by Trevor Gore » Fri Sep 14, 2018 9:02 am

The panel mass is the wood density multiplied by the panel volume. The panel volume is its thickness (which you have just calculated) multiplied by its area. The panel area is the bit that is hard to calculate. If the guitar shape was drawn on a CAD type program, the program will give you the area. If the shape was hand drawn, you might want to consider counting squares on graph paper (a historic way around the problem). Another neat trick involves using the (half) template of the body shape, which nearly everyone makes and some decent digital scales (available at kitchen shops for small $ if you don't already have some). If the template is made out of material of very uniform thickness such as Perspex or Lexan, the density of the plastic can easily be computed when the material is still "in the square". Density = mass divided by (length x width x thickness). Knowing the density, mass and thickness of the template, you can calculate its area - Area = (mass of template)/(density x thickness of template).

Make sure you account for all the zeros as you swap between millimeters and meters and grams and kilograms.

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