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I just started doing deflection testing on my last guitar but only did it when i thicknessed my top. used 5lbs and thinned down till it dropped .25. just wondering if you guys do deflection testing for your backs and also if you do test on your tops and backs with braces attached. the only threads i can find on deflection testing is on thincknessing tops. i i would like to start deflection testing everything.

I havn't used it yet, but am thinking to go along these lines following Brian Howard's post with this link to his blog.
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=47095&p=623491&hilit=howard+brick+deflection#p623491

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I do mine very similiar to Brian Howard brick and all, in fact got the idea from him and that website. The only thing I decided to do differently was to do the deflection when the plate is still a rectangle rather than cut to shape. I have my own metrics involved in it and really that's what it's all about. After I brace it I also do deflection by placing the ends of the X-Brace up on small blocks. I think that's a very valuable measurement to take. It's one thing to get all your plates to the same stiffness but then when you brace it that all changes. So if you are going for identical as possible guitar tones then it seems to me that you would want to know that every thing is the same or close enough after bracing.

Yeah that's what I want to do what measurement do you try to get it to drop with the braces on

I have no idea

But seriously. This is only the 3rd guitar I have done this with. I'm thinking I need at least ten before the data set starts to make sense. I'd have to look at my notebook but the above unbraced deflection was something like .4in and when it was braced it was like .0-somthing. So it hardly moves, but it does and my guess is that it's important to know.

James Blilie has a nice section on testing wood samples in his article in the most recent 'American Lutherie'. He advocates using cutoffs of the back and top for this, which certainly makes it easy to get samples. You can also test brace stock this way. One advantage of this sort of protocol is that you get 'universal' numbers: Young's modulus along and across the grain. It makes it really easy to compare your results with those of other people, so you can use their numbers as a leg up, rather than having to make a bunch of guitars to find out what to do. Of course, everybody's system is a bit different, and you will probably end up tweaking things to suit the way you work, but it still gives you some sort of starting point.