Tiny bindings

[Hans Mattes]

The fact that top purfling doesn't extend past the lining doesn't mean that there's no "hinge effect." The top is substantially thinner where the purfling is installed. Even if there's full-thickness top fastened to the lining inboard of the purfling, the glue joint there is narrow and won't give as much rigidity to the top as if the full-thickness top extended all the way to the outer binding.

I'd be interested to know if folks who've made many guitars (and I'm still on my first one) have noticed any tonal effect due to the width of the top purfling (e.g., thin purfling vs. an abalone trim around the top).

[John Parchem]

The fact that top purfling doesn't extend past the lining doesn't mean that there's no "hinge effect." The top is substantially thinner where the purfling is installed. Even if there's full-thickness top fastened to the lining inboard of the purfling, the glue joint there is narrow and won't give as much rigidity to the top as if the full-thickness top extended all the way to the outer binding.

I'd be interested to know if folks who've made many guitars (and I'm still on my first one) have noticed any tonal effect due to the width of the top purfling (e.g., thin purfling vs. an abalone trim around the top).

I have made them with thin and fat purfling lines and have not noticed any difference. The top is not just sitting on the lining it is glued down. Mechanically I can not see how a filled in purling rebate right above a giant brace (the lining) provides any hinge. There is a huge impedance mismatch between the top and the lining, that reflects the energy back to the top. Thinning the top on the edge (inside of the lining) does increase the impedance mismatch between the lining and the top and can be beneficial. I can not see a thin or fat purfling line doing anything tonally. They are just decorative. While making your fist guitar there will be a bunch of things that you are doing that will make major differences to the sound of the guitar. Selection of purflings is not one of them.

[ken cierp]

I have made them with thin and fat purfling lines and have not noticed any difference. The top is not just sitting on the lining it is glued down. Mechanically I can not see how a filled in purling rebate right above a giant brace (the lining) provides any hinge. There is a huge impedance mismatch between the top and the lining, that reflects the energy back to the top. Thinning the top on the edge (inside of the lining) does increase the impedance mismatch between the lining and the top and can be beneficial. I can not see a thin or fat purfling line doing anything tonally. They are just decorative. While making your fist guitar there will be a bunch of things that you are doing that will make major differences to the sound of the guitar. Selection of purflings is not one of them.

Ditto all the way

Now I have read where some teachers have reported an improvement in sound quality when class room project guitars which are not bound during the course have bindings added at a later date -- I think I can buy that since to me the bindings do add structural integrity.

[Dave Bagwill]

Yep that was Brian Burns - two students took their guitars home unbound because of time constraints - complained the sound sucked - Brian agreed, then bound them, and the result was all the sound they had been looking for.

The actual thread:
http://acousticguitarconstructionforum. ... t=30#p6192

[John Parchem]

I agree that binding changes things on my guitars. I can see it when I tap the top and take a frequency spectrum both bound and unbound. There is a noticeable change in the resonance.

[Dave Bagwill]

John, do you thin the perimeter of the soundboard as well? What method do you use?

[John Parchem]

I did try once using a plane but stopped after I got tearout by going the wrong direction. If a top seems stiff I will go after the perimeter with a ROS with 120 grit. I never take it down very much. I mark out the area I want to thin lightly with a pencil and sand the pencil marks away. I then recheck both how it taps and sometimes with my magic probe.