Replies to This Discussion

Permalink Reply by MichaelS Country Boy Guitars on December 8, 2010 at 3:35am

I think I have not seen that done before, give it a try it should work.

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Permalink Reply by Rand Moore on December 10, 2010 at 6:53pm

This is an interesting idea. Try it and let us know how it works out. A couple of photos too!

 

I just thought maybe you could do a box with a cut-out for easy access to the upper most frets on the fretboard and then close it in with a wire mesh, forming a sound "hole" that way. See the diagram below. Just an idea sparked by this thread.

-Rand.

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Permalink Reply by MichaelS Country Boy Guitars on December 11, 2010 at 3:51am

What do you need the wire mesh for, juts cut it open, big ol' acoustics don't have wire mesh over their big round hole, plus it will make a nice home for a homeless mouse. Interesting idea either way. 

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Permalink Reply by Rand Moore on December 11, 2010 at 4:38am

The mesh is basically to keep out rodents. It may also serve to make it easier to hold. Not having built one this way, I can't speak from experience. But it probably is another instance of my over-engineering something.

 

-Rand.

MichaelS said:

What do you need the wire mesh for, juts cut it open, big ol' acoustics don't have wire mesh over their big round hole, plus it will make a nice home for a homeless mouse. Interesting idea either way. 

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Permalink Reply by Hip Bone Bellaire on December 11, 2010 at 5:04am

I finally gave in a bought a Forstner Bit kit... I have a drill press and decided this would be the fastest and most perfect way of making the holes.."I have 2 kids and not much time" If I cut a bad line then it'll bother me forever... just like my current bridge... it's off but it's gotta stay.... for a first timer with the Forstner Bit... I can't believe how easy and nice it looked... this box has a paper cover and I was real worried about tearing it up... worked perfect... thanks guys....

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Permalink Reply by MichaelS Country Boy Guitars on December 11, 2010 at 8:46am

Forstner bits are great arent they? I just inherited an old set from my grandfather, what a nice hole they make. I still like the corner cutting and end of box cutting ideas, Rand you should try them and get back to us.

Hip Bone Bellaire said:

I finally gave in a bought a Forstner Bit kit... I have a drill press and decided this would be the fastest and most perfect way of making the holes.."I have 2 kids and not much time" If I cut a bad line then it'll bother me forever... just like my current bridge... it's off but it's gotta stay.... for a first timer with the Forstner Bit... I can't believe how easy and nice it looked... this box has a paper cover and I was real worried about tearing it up... worked perfect... thanks guys....

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Permalink Reply by Rand Moore on December 12, 2010 at 1:44pm

Hi Guys.

The problem I see with indiscriminately cutting off the corners of the box without first re-enforcing them in some way is that you weaken the structural integrity of the box a lot.  The box I built used butt joints and were reinforced by glued on corner posts. If you cut off the 4 corners, the only thing holding the box together is whatever joint you had between the sides of the box and the top and bottom "soundboards". So, if anyone wants to try the cut-off-the-corners-sound-holes idea, then they will need to first re-enforce the box in some way.

 

One way this could be done is to add two vertical posts (from back soundboard to front soundboard) for each corner, locating one in front and the other beyond where the corners will be cut-off. Glue these to the side walls and top and bottom sound boards. Then add some small wood strips (about 1/4" square and cut to length) all the way around the top and bottom sound boards. Then glue the small strips to their associated soundboard and side wall. These will act like little the corner posts and will strengthen these joints. Then glue together the top lid of the cigar box to the bottom, clamp and let dry.  After drying overnight, cut the corners off and see what you get. It should be fairly sturdy. As you can see, this is a lot more work than cutting sound holes. Still it might be worth building one to see what its like.

 

-Rand.

 

MichaelS said:

Forstner bits are great arent they? I just inherited an old set from my grandfather, what a nice hole they make. I still like the corner cutting and end of box cutting ideas, Rand you should try them and get back to us.

Hip Bone Bellaire said:

I finally gave in a bought a Forstner Bit kit... I have a drill press and decided this would be the fastest and most perfect way of making the holes.."I have 2 kids and not much time" If I cut a bad line then it'll bother me forever... just like my current bridge... it's off but it's gotta stay.... for a first timer with the Forstner Bit... I can't believe how easy and nice it looked... this box has a paper cover and I was real worried about tearing it up... worked perfect... thanks guys....

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Permalink Reply by carverman on December 13, 2010 at 7:19am

That would be similar to a cutaway on a regular guitar...not a bad idea, especially if you need access to the higher frets.

I'm now thinking that when I make my next one (6 string), I may try and do a Paul McCartney Hofner Beatle Bass design

for it.  I can cut the fancy side shapes out of spanish cedar on my band saw and perhaps a carved top? with a couple

of small f-holes....the possibilities in this building medium is limited only to the imagination..although there must

be other physical building limitations as well.

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Permalink Reply by carverman on December 13, 2010 at 7:27am

Cover up the mouse holes?   Is that what those round grommets with wire mesh are supposed to do. 

 Probably redundant in my case, since I have a cat in the house.  But I just like the look of nice brass mesh,

It just looks so cool.   

 

Now here is a question on acoustic resonance.   On regular guitars the round sound hole size has a lot to do

with the acoustic resonance of the guitar or f-holes in case of the violin.

 

Is there a formula for the size and number of round grommets /sound holes on GBGs?

Rand Moore said:

The mesh is basically to keep out rodents. It may also serve to make it easier to hold. Not having built one this way, I can't speak from experience. But it probably is another instance of my over-engineering something.

 

-Rand.

MichaelS said:

What do you need the wire mesh for, juts cut it open, big ol' acoustics don't have wire mesh over their big round hole, plus it will make a nice home for a homeless mouse. Interesting idea either way. 

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Permalink Reply by Rand Moore on December 13, 2010 at 2:51pm

There was a discussion recently on CBN's Super Advanced CBG Building group. They may have a formula. Not sure how valid it is. Could also search Google. I don't really know a formula, but if there is one and it has proved out by multiple CBG makers, then it's worth having. I'll look around a bit...

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Comment by herb berwald on November 10, 2010 at 5:06am

1. Calculate box volume, LxWxH
2. Solve for the radius of a sphere of the same volume, ((3*V)/4*pi())^1/3
3. Divide the radius by 4
4. This is the new radius of the sound hole.
5. 2*r is the new sound hole diameter...
for this box it is around 5 inches...almost like a regular guitar. I must have done something wrong.

Assuming the box is 8.25" x 5.5" x 2.75", our calculated hole diameter should be:
    (2 * (((3 * 8.25 * 5.5 * 2.75) / (4 * 3.14))^(1 / 3))) / 4 = 1.55023303

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Does that formula make sense?  I was never good at math.

-Rand.

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Permalink Reply by MichaelS Country Boy Guitars on December 13, 2010 at 3:25pm

Rand, I think the original intent was just to cut the corners off the lid, then of course it got out of hand and into new territiory.  The first idea should work with no problems, the second idea may need some structural help, it should be done anyway, if for nothing more than an excuse to add more brass mesh, lol.

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Permalink Reply by Rand Moore on December 13, 2010 at 5:17pm

Oh, yeah. He's just talking about cutting the corners off the lid and leaving the base (bottom of the box) intact. Yeah, that should work, assuming the top is well secured (glued and/or screwed) to the base. That would also be pretty easy to do. I guess when I add comments to a thread, I should first re-read the original thread, in case I missed something, or my mind wandered off too far.

 

-Rand.

MichaelS said:

Rand, I think the original intent was just to cut the corners off the lid, then of course it got out of hand and into new territiory.  The first idea should work with no problems, the second idea may need some structural help, it should be done anyway, if for nothing more than an excuse to add more brass mesh, lol.

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