Replies to This Discussion

Permalink Reply by Kirk on September 14, 2018 at 5:03am

My own personal thoughts, please don't take offense.  But if you're going to brace and tap tune, just make an acoustic 6 string, and not a CBG.

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Permalink Reply by Paul Craig on September 14, 2018 at 5:26pm

CBG's are simple instruments, often made of crude materials, using crude construction techniques  and often used to play crude music styles.

Of course that doesn't mean that you can't make a CBG with better materials and using better construction techniques, but then it really becomes something else and lose it's original charm.

Tap tuning can be used on most any instrument made, but the results would depend on how well your CBG is made.

A simple tune by ear or electronic tuner of the open strings and checked/compensated at the 12 fret (and 24th fret if you have one) is good enough. 

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Permalink Reply by Taffy Evans on September 16, 2018 at 8:22pm

Hi, I tune the soundboard and back of the acoustic guitars I build, I always have done. But with the limitations of a cbg, as small as it is,I think is it worth it or even beneficial to creating a better sounding instrument. Some builders have used cross braced tops, I have too, thinking, well acoustic guitars have them. But I feel they are not needed. Cross braces in a guitar are there as structural support. CBG tops are very narrow and I think simple suitably carved 'ladder" style braces would suffice. If you say "I don't need braces then you tops may be too heavy/thick.

The best sounding CBG I have built was built using acoustic guitar principals and techniques.

These included a box with dimensions that I had found most suitable.                                             Hardwood back and thin sides, Blackwood in this case                                                                           Top was close grain Cedar                                                                                                                Top and Back were quarter sawn, book matched and thinned to a suitable flexibility                        Quarter sawn spruce braces cut were carved to reduce mass but retain strength and not inhibit top or back vibrations.                                                                                                              I probably tapped the top and back whilst carving the braces, mainly to test response quality, I did not try to "tune" as I would in a full guitar.                                                                                    I used kerfed linings.

The guitar when it is played to customers raises eyebrows and "wow's" when heard. I play other models first, and then this baby. I should mention that it is a 6 string, so drives this top very easily. Three string? I'd work the top to a different tolerance, but it must be responsive.

Its the guitar take on trips it gives a pleasing loud acoustic sound with excellent sustain.

I was playing this guitar in my motel room, with the door open, and a guy from the car yard next door called out to ask what I was playing. Ya gotta be happy with that.  

I agree with to comments from the previous contributors: if you going to all that trouble etc.               and ..........it loses it's original charm. Love this guitar for modern style blues, but equally love my cbg that is very basically built but has that dry delta blues sound.

Gee I do get carried away...sorry.                                                                                                                    

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Permalink Reply by Ken I on September 17, 2018 at 2:05am

First I want to thank everyone for their opinions. I think I agree with the general consensus. These are CBG's. A huge part of their charm is the fact they are "home made" from found materials. Introducing professional guitar building techniques could destroy this charm.

Taffy,

I don't think you got carried away. I found your response informative and enjoyable to read. I am just beginning my CBG journey coupled with other wood working projects and ideas. I haven't given any serious thought to making a standard guitar, but the idea has crossed my mind to consider further in the future.In light of this all information about guitar building is interesting to me. I appreciate you taking the time to write this response.

Thanks again to everyone.

Ken

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Permalink Reply by Ron Lutz on September 18, 2018 at 2:49pm

I have found excellent results placing the bridge at the rear nodal point.  inside box length X 22.4% to find placement from tail end of box.  If one holds a piece of wood between thumb and finger and tap the wood while held in different places you will arrive at a spot that produces the best tone and sustain.  This is the node.  That spot is the place of least vibration,  placing the bridge there allows maximum freedom of vibration for the remainder of the top.   There is a nodal point at each end of a piece of wood the same distance from each end.  A visual image would be similar to the waves from an oscilloscope.  with a line through the middle, the node would be where the wave meets the center line.  that may help illustrate the comparable movement of the wood as it flexes up and down.  It would be easier to see the illustration actually drawn out.  I am probably over complicating the explanation.  but in the end this procedure works best for me.   Also on the boxes I make from scratch, I find that most hardwoods especially quarter-sawn (vertical grain) gives the best vibration.  I am very fond of using walnut for tops and bottoms around 3/32 thick. in addition to having great resonance and sustain, it is an exceptionally beautiful wood in my opinion.

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Permalink Reply by Cause the Blue rat on September 18, 2018 at 3:44pm

I don't think there is any way to go to far with a CBG. If you can find a way to make a simple box sound better go for it! 

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