Replies to This Discussion

Permalink Reply by Taffy Evans on December 8, 2023 at 10:21am

Hi, without having a box like the ones you described I can only suggest that If you understand some of the reasons for bracing it may help you plan your next build.

1 - to provide support against the tension of the strings. Structural braces.

2- to control the vibrations of the top and back. In so doing, enhancing the desired tone and volume.

This is a balancing act between improving the responsiveness of the back and top or dampening it.

Eg: some folks may suggest a brace under the bridge. But thinking about that, this may provide structural strength, but may also dampen the response created by the strings.
And of course, the size and materials used as well as the positioning all play a part.

Cheers Taff

• ▶ Reply

Permalink Reply by Chance on December 8, 2023 at 12:54pm

Thanks Taffy. Oh yeah, I totally get CBG'S are a balancing, give and take, comprise etc.

It's really amazing you can get a quality sound out of a cigar box and a stick!

• ▶ Reply

Permalink Reply by Bob Herget on February 4, 2024 at 12:27am

Hello,

I've made quite a few builds using pressboard boxes.
I use neck-through design on all my builds.
Using a neck-through design, the only tension is that of the bridge pressing down on the box top.
The rest of the box is then just hanging "there" around the neck and under the top, with absolutely no stress being applied to the box at all.
I've found that the need for bracing is very minimal.
Having the box ends tightly fitted to firmly "hug" the neck provides a lot of stability to what might otherwise be considered to be a flimsy box.

I glue 1/4" square wood stock in the box corners extending from top to bottom and also midway along the sides, again, from the bottom to the top of the box.
That's it.
The top ends of those "post" braces then provide an area to install very small diameter 3/8" long screws through the top to attach it to the box.

The only other special consideration is that pressboard cigar box soundboards tend to deflect quite a bit more from string tension than do most wood boxes, so a bit of additional bridge height needs to be built into them to accommodate the bit of "sinking" of the top that will occur over the first few months of the guitar's life.
I make the bridge about an 3/16" or so higher than I would when using a wood box and live with a somewhat high action until it settles in to its final height, then I adjust as needed by sanding the bottom of the bridge until I have the action I want.
On my very first build, I used threaded rod as a bridge. As the top deflected more over its first months of life, I had to change the threaded rod to increasingly larger diameters to maintain proper string action, which was OK, but I find that I get better sound with handmade wood bridges.
I use 1/4" thick scraps of fretboard padauk for that purpose.
If that "sinking" factor isn't figured in, the strings will soon be resting on the frets.
After that initial break-in and adjustment period, they stabilize and are good to go.
I feel that bracing the top to prevent that deflection would deaden the guitar's sound.
Maybe not.
I've been happy with the way they've turned out for me so far, so I never felt the need to try bracing the top.

Before my first build with a pressboard box, I was concerned that the top wouldn't resonate very well, with the pressboard top being deflected to a greater degree than most wood boxes, but that hasn't happened on any of my pressboard builds.
They sound different than wood boxes, but not worse, to my ear.

There are those who disagree with me, but I have a fondness for the somewhat "plunkier" sound that seems to come from using pressboard boxes.

If your build style depends on the box itself for structural integrity, then by all means, brace away.
My guess, though, is that they actually need less bracing than one might think.
Think through the build and use any bracing in a judicious manner.
Brace what is needed and no more.
I believe that the entire box is much more at play in producing sound in CBGs than it is in traditional guitars.
I'm of the less bracing used, the better camp, for sound quality and weight considerations.

Enjoy the hobby.

Cheers,

Bob

• ▶ Reply

Permalink Reply by Taffy Evans on February 5, 2024 at 11:36am

Hi, this is an interesting subject, it’s good to see it reintroduced for further discussion.
Just a few important issues I consider when building any flat-top stringed instrument.

As the top is the most important part of a stringed instrument in producing sound, it needs to be responsive, to be easily excited by the motion of the strings. I want my tops to produce not only volume but also a pleasing colorful sound.

I find it hard to describe sound quality, but a listener’s face will often tell me they are hearing the differences in different instruments when they hear them played.

The movement of the top is often described as acting like a bellows or pump, it moves up and down acting like a pump, pushing soundwaves out of the soundhole as the strings are plucked. My tops are pretty thin, depending on the timber used 2 – 3mm.
If I press them with my thumb they will sag or collapse slightly in the middle, so I brace them. My thinking is a brace would relieve some of the stress in the top by directing it to the sides. My thinking was that if strung up with collapsed top I’m losing part of the pumping action as the pump is already at one end of its stroke, so to speak.

Liken it to - three people sitting in the middle of a trampoline, a fourth person jumps on and there is very little rebound [movement] left because the surface is already extended, so the full intended motion of the trampoline is lost.

As Bob states it’s easy to over brace. Over-bracing as well as under-bracing has unwelcome effects on full acoustic guitars, as I often see as a repairman. It’s possibly not so noticeable in a CBG, but still something I consider.

Bob's method works well for him, and that’s fine as he is only building for his own use I imagine. But if you are building for others to enjoy they may want their guitar to be perfect from day one.
Taff. Use HTML to reply...

• ▶ Reply

Permalink Reply by Southern Ray on February 16, 2024 at 7:06pm

 Interesting conversation going on here and thank you guys. I've learned from this. I have one observation that I have about a Partagas box that I have. It has a press paper top and I noticed when it gets humid and stays that way for days, I have noticed that it gets quieter when things are damp. That's one of the reasons that I took her apart after initial build and put one of my pup in it. When the weather dries, it seems to go back to normal loudness.

• ▶ Reply

Permalink Reply by Timothy Hunter on February 17, 2024 at 6:40pm

that makes sense. the cardboard is absorbing the humidity. this will do two things. 

1) It will make the pressed paper board denser

2) It will also tend to make the pressed paper board softer.

Both of these things will reduce the vibrations transmitted from the strings. This is why its quieter when its rainy and comes back to life when the board dries out again.

• ▶ Reply

Permalink Reply by Taffy Evans on February 19, 2024 at 12:44pm

I would like to make another comment or two stemming from Tim's information which I think is spot-on and shows the effect the environment has on our instruments.

I have a few guitars that will go flat by half a tone due to the weather, they are still in tune but the concert pitch is now played at the first fret instead of the nut. This is only if the guitars are left on their stands and not in the case.

One of those guitars I built 45 years ago and still holds a very low action for an acoustic guitar, so much so that during seasonal changes the strings will buzz on the upper frets. So, to overcome this I have two bone saddles in the case and swap them to give the desired action when seasonal changes are experienced.

Many years ago my grandaughter brought home a school project to show me. It was a "guitar" made with a tissue box. She was very proud of it. Just for fun, I showed her how to make it sound even better by doing many of the suggestions put forward in this thread, she was really happy then.

So, if a tissue box can be made to sound better...
Cheers Taff

• ▶ Reply

Permalink Reply by Timothy Hunter on February 22, 2024 at 3:45am

cheers Taff, 30 years of playing with copiers and printers has given me a little experience with damp paper..lol

• ▶ Reply

Permalink Reply by jon neet on February 22, 2024 at 5:58pm

• ▶ Reply

Permalink Reply by jon neet on February 22, 2024 at 5:58pm

• ▶ Reply

Permalink Reply by jon neet on February 22, 2024 at 6:00pm

• ▶ Reply

Permalink Reply by Southern Ray on February 22, 2024 at 7:24pm

 Jon,

 Use the HTML Editor at the top right of the posting window.

 Cheers!

• ▶ Reply