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PostPosted: Fri Nov 06, 2009 2:55 pm 
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Walnut
Walnut
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Joined: Wed Sep 30, 2009 4:55 pm
Posts: 29
First name: David
Last Name: Hurd
City: Hilo
State: HI
Zip/Postal Code: 96720
Country: USA
Focus: Build
Status: Professional
After Part 3 of the series, you are pretty much in business with respect to beginning to collect numbers. But now what?

Using an Excel spreadsheet to store and modify the data has been useful to me. Here is a link to a sample spreadsheet having data from a Kenny Hill Palo Escrito #3027:

http://www.ukuleles.com/spreadsheets/HillPE3027dataform2lbscorr.xls

To download the spreadsheet, just click on the SAVE button. Locate the file and single or double click on it to open it.

The file consists of two parts: a simplified map of a guitar top with the 0,0 point being the center of the lower bout; and a four column data storage and modification section. The first two column locate the data point locations on the guitar, the third normalizes the data to a particular effective weight and the fourth column is the actual collected deflection data.

If we're all going to look at numbers and compare them in a rational manner, we need to be using either the same or one of a limited number of choices. I suggest that a 2 lb effective weight is good for ukuleles and nylon string guitars. Perhaps a 3 lb effective weight would be better for steel string acoustics.

For plotting the data, I really like the program DPlot by David Hyde: http://www.dplot.com . For ~$60 this is to me a terrific program with all sorts of uses besides just making surface plots. If you're thinking of dropping $150 on a ToneRite or $200 on the Somogyi books, Hyde's program is chump change by comparison.

In any case, here's what a sample top deflection plot looks like for the guitar in question using Hyde's program:

Image

Note that the measurements were made with the strings slacked and the bridge on. For anyone interested in using Hyde's program, I'll be happy to post or send them a sample plot file using the above data.

aloha,

_________________
David C. Hurd
http://www.ukuleles.com

Alice laughed: "There's no use trying," she said; "one can't believe impossible things." "I daresay you haven't had much practice," said the Queen. Through the Looking Glass by L. Carroll

"Since my house has burned down, I have a much better view of the moon"


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PostPosted: Fri Dec 24, 2010 12:48 am 
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Brazilian Rosewood
Brazilian Rosewood
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Joined: Thu Aug 18, 2005 2:21 am
Posts: 2924
Location: Changes when ever I move..Australia
Focus: Build
Status: Amateur
You are currently viewing part 4 of 4.

PART 1: http://www.luthiersforum.com/forum/viewtopic.php?f=10117&t=24469

PART 2: http://www.luthiersforum.com/forum/viewtopic.php?f=10117&t=24470

PART 3: http://www.luthiersforum.com/forum/viewtopic.php?f=10117&t=24471

Cheers

Kim


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