Official Luthiers Forum!

I'm new to building(working on #3 now) and have a question about deflection testing. I've been looking at past posts and can't seem to find a definitive answer as to why you do deflection testing (on the top is what I've been looking at)? Does it help for consistent strength? Tone?

Also, I've noticed a lot of people have their way to test, but is there a standard method of testing with results that can be compared to others?

Thanks,
Clay

well Clay .. every piece of wood has different strength properties .. if you built guitars from various tops of the same species, say lutz, they will likely all require to be different thicknesses in order to provide the same stiffness and strength. If you simply built the guitars with the tops all the same thickenss, you will find some guitars will sound/work better than others, simply because some pieces are now too stiff, or conversely, too loose and floppy. Go to your local guitar shop .. try all the Taylor 414s they have .. do they sound the same .. do some have better bass or trebles .... well, all the tops on Taylor 414s are the pretty much the same thickness and that accounts for a lot of that difference.

All that said, you also have to have an idea of how strong your bracing pattern and braces are in order to work in conjunction with your chosen top stiffness. Its a system if you will. Some thin tops and use heavier braces, some will leave tops heavier and use lighter braces.

There is no single (and simple) answer ....

_________________
Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

When I first saw the title of this thread I was going deflect the question.....

Clay buddy in addition to what Coach Tony said if you record the deflection data and bracing data for each top you have a better shot at modifying or repeating to a degree your results another time.

I think that we all probably have our own systems for measuring deflection so that data that has been recorded is useless to anyone else unless they use the same system. Just suspend your top between 2 fixed points (and record the distance or better yet set-up a jig so you can repeat this) and place a given weight on the top and measure the top's deflection and record same. I have only done this along the grain so far but it could be done across the grain too but with less weight then I use......

The real value of the data comes into play when you start acquiring a bit of a database of results to compare and contrast and develop a method/system to accurately evaluate your guitars..... The later of the two is NO easy task to quantify and perhaps impossible....