Measure guitar volume?

[Len McIntosh]

I'm in the process of completing a parlor size guitar but deeper ,
I then wondered how it would compare volumn wise with say a ooo size
My first thought was perimeter measurement comparison but this changes with the waist size so hmmmmi coud fill each with jelly beans, any other ideas?

[Bryan Bear]

You need to calculate the area of the top (or back) and multiply by the depth. Assuming the sides are tapered, this complicates things. You could put the body shape on graph paper and tediously count out the squares and partial squared to get an estimate (better you than me). . . I'm not in the know about computer design, but I bet there is an automated way to calculate area of an irregularly shap. Actually, I assume that same program would be able to calculate volume. Now that I have offered no real help, I'll go. <G>

[Darrel Friesen]

There's a few ways short of autocad that you could use. Running a string or low tack strip of masking tape around the perimeter then forming a circle with it, averaging the depth and using Pi x radius squared x the thickness should get you close. Filling with puffed wheat or rice krispies similar to your idea would get you close as well. Just repeating things I've seen over the years when this question comes up.

[Chuck Tweedy]

cheerios

[Darrel Friesen]

All bran.

[Trevor Gore]

Dried peas, measuring jug.

[Michael Lewis]

Why?

[Len McIntosh]

Trying to answer the why, my first attempt became an essay into guitar shapes but really i just want to know how my deep parlor body compares with my shallower 000 volumn wise, just curious.
We know that over the last 180 years Martin standerdized on dimensions for each shape, they dont make a 000 depth dreadnaugh or one thats 6 inches deep at the end piece, their parlor guitars are a specific depth, when i preped the sides for mine i decided to leave them about 3/8 of an inch wider rather than trim to spec, we shall see how she sounds in about six weeks.
By the way im leaning to rice plus golf balls.
Second choice is graph paper on the top (or back) count the squares,and average the body depth over several points.
thanks to all - this forum inspires

[Chuck Tweedy]

By the way im leaning to rice plus golf balls.

Now think of how heavy a guitar filled with rice and golf balls will be. That could lead to a very unfortunate accident. That is why the suggestion of Cheerios or Rice Krispies.

Second choice is graph paper on the top (or back) count the squares,and average the body depth over several points.

That will not account for blocks and bracing. Also I don't think it will be very accurate in the first place (even without the internal "obstructions")

[Dave Stewart]

This sounds like a curiosity thing for you, so accuracy to the third decimal is probably not needed. First, do no harm. Second, even cheap cad programs allow you to trace the perimeter of a freeform object (eg guitar) & calc. area. (Get yourself turbocad or similar.) From there, calc. volume for the max depth & min. depth of your sides and estimate an "average" depth for final volume.

[Bryan Bear]

Darrel, I’m not convinced that perimeter and pi will be enough to calculate area of a guitar shaped object. I could be wrong since math is not my strong suit though. I have a rubber band sitting on my desk, the area it encloses is mostly round. If I squeeze it on two opposite sides, the circle (now oval) gets much thinner but not a whole lot longer. You don’t need t measure it to see that the area enclosed by the rubber band is much less in oval form than circle form. That is the extreme example but I can make it into a few different guitar shapes and to the eye they also do not appear to have the same area (though it is much harder to tell). What am I missing?
Chuck, conceding the blocks and bracing issue, how is the graph paper inaccurate. Sure it will not be as accurate as a computer model but I’m not sure that is the degree accuracy we are after in this case. The estimating of enclosed area of partial squares around the perimeter would be annoying but as the grid square size decreases accuracy increases (as well as neck pains. . .).

[Darrel Friesen]

You're correct Bryan. It would be a rough calculation and more importantly a comparison between two different guitars that should give you a ballpark idea of the difference in volume between the two. I've been having a bit of a run lately on failing to explain myself with a high degree of alacrity. Ha!

[Len McIntosh]

My original wish was for a formula to measure relative volumn between body sizes.
I have not given up but have been working on same.
First off i wanted to get an order of magnitde hoping for numbers similar to car engine sizes - which would be cool.
Did a quick calc of my 000 (area of two circles x avg depth) 870 cubic inchs!! Thats almost 4 us gallons ,over 14 liters, big shock had guessed about half that number.
Decided to fine tune the formula, so i divided the shape into 7 segments, right and left, upper and lower hemispheres, a rectangle across the waist and two rectangles separating the hemisheres.
Measurments used were body length, bout widths, waist width, and an approximate radius for each bout and depth at five points.
Fyi my max depth numbers are, 000 - 4 1/8. Reg parlor (aka 12 fret 0) 4 3/16. My "deep parlor" 4 9/16 (3/8 more)
My formula gave volumns as follows 000 792, reg p 721, deep p 769
Wondering just how inaccurate this was i decided to get out the quad paper (1/4") and an hour later came up with the following ( pretty accurate) numbers
000 894 , reg p 744, deep p 802.
Whats next? Gonna tinker with the formula and finish the deep parlor cant wait! As the first guitar player said to the second "Stay tuned"

[Dave Stewart]

FWIW here are some figures I had buried in my vast notes..........may help
Soundboard Areas:
OM: 227.184 inches squared.
00: 208.893 inches squared.
L-00: 213.566 inches squared.
Dred: 257.323 inches squared.
Marlin sp? 15": 183.247 inches squared.

Box Volumes:
OM (4.09-3.35" sides): 845.124 cubic inches
00 (4.13-3.385" sides): 784.915
L-00 (4.37-3.46" sides): 836.110
Dred (4.875-3.75" sides): 1109.705