Replies to This Discussion

Permalink Reply by Rand Moore on October 4, 2010 at 3:19pm

Hi All...


I have built a few "neck-thru-the-box" style CBGs, but only have attempted one "bolt-on" (or "screw-on") CBG, but it didn't turn out as well as I hoped. So, I am also interested in good ways to attach (guitar) necks to cigar boxes, but I want to do so using a minimal amount of space within the box so I can maximize on the resonating characteristics of my rather small cigar boxes. To share what I've done to date, I have included crude drawings of my design. Here they are:

The poplar wood piece used to strengthen the side of the cigar box is like 5" long, 1.25" wide and 0.75" thick. I actually used another piece of wood under the poplar piece as a kind of shim to make the poplar reinforcement block come up to the level I wanted so the neck of the guitar is level with the top of the cigar box, but this is not shown on my drawings. Here's the rest of my drawings...

On my original design, I wasn't going to use a heel, but I found that I needed to add one because under the tension of tuned strings, the neck would bow upward at this junction. So, I did a "quick-fix heel" by cutting out a triangle bock of wood and glued/screwed it on as shown in the last few drawings on the second image file above. Next time, I'll build a heel onto my neck to begin with and do a nicer job of shaping it. However, I'd actually prefer an alternate design where I don't need a heel. Anymore good ones? Illustrated with drawings or photos? Let's see them. Or, comment on mine in how to make it better.

-Rand

• ▶ Reply

Permalink Reply by ken farmer on October 4, 2010 at 3:58pm

I've built many of mine similar to #2, but with a few differences:
a. I add a heel to the neck with allows for a second fastener
b. I use large lag bolts
c. I take the fretboard further back and add a small screw through the top into the block or top. This works well since my fretboards are screwed on and the screws are the fretmarkers (makes it easy to swap screwed up fretboards)
d. my internal blocks are oak, and not very large - only about 1/2" thick

The end result is very strong, very repeatable, and easily disassembled. I can't say that my necks are exactly identical, but almost. The only tricky part is lining up the holes so that your neck mounts in the exact right location. Also, I built a jig to hold the neck so that the holes drill straight.

• ▶ Reply

Permalink Reply by Bluesdog on October 5, 2010 at 3:22am

I was thinking about a bolt on technique with 2 long bolts split about a centimeter (0.4 ich or so) down the midle and welding those to the downwards part of a t-bar neck reinforcement rod, insert that into a neck with the two bolts at the body end of the neck and feed those trough a neckpocket with nut's at the other end to keep it down, anyone tried something like this before? And if not, will this be strong enough to hold a 3/4 size 6 string neck down?


I like experimenting but dont fancy a neck slamming into my or anyone else's face when it fails and folds up so if anyone can shine a light on this subject strengthwise it would be much apriciated.

• ▶ Reply

Permalink Reply by ChickenboneJohn on October 6, 2010 at 12:25am

The point that so many people seem to be missing here is the mechanics of leverage the leverage exerted by the neck. The fixing bolts/screws need to be spaced far enough apart to resist the leverage that the string tension exerts in the neck/body joint. (obviously twice as much with a 6 string as a 3 string), so the neck needs to be set into the body to allow those fixings.

See how far apart the screws /bolts on a Fender style neck are spaced - about 2 inches? They've done the hard work for you - it works. Space your fixings like this (2 are fine for a 3 or 4 string) and put a corresponding block under the end of the neck to fix thu' and it will be good. You don't need to weld bolts to the neck reinforcement or add a heel...keep it simple, don't make it hard on yourself.

Rand - the reason you needed to add a heel was that the fixing block simply doesn't project into the box enough and couldn't resist the twisting moment (engineering term for a force that's trying to turn something) exerted by the strings - by the way, that internal backing board is adding no significant strength to the joint. A bit more solid timber blocking inside the box isn't going to hurt the sound as long as you keep it away from the vibrating top, and guitars always work better when they don't fold in half when strung up.

• ▶ Reply

Permalink Reply by Rand Moore on October 6, 2010 at 4:13pm

Hi , ChickenboneJohn.

Thanks for the feedback. I'll use your suggestions to retro-fit my CBG and remove my "tacky" heel. I guess I am too worried about the acoustic effects of filling the cigar box with a of extra wood framework, etc. So, this build can be my testbed to see if adding additional wood (reducing internal empty space of the resonator) actually has a negative effect (or not). I've been playing all week with my new CBG, and it sounds pretty good, but looks a bit ugly with my quick and dirty heel. I'll see how it plays when more internal support is added. Thanks again.

-Rand.



ChickenboneJohn said:

The point that so many people seem to be missing here is the mechanics of leverage the leverage exerted by the neck. The fixing bolts/screws need to be spaced far enough apart to resist the leverage that the string tension exerts in the neck/body joint. (obviously twice as much with a 6 string as a 3 string), so the neck needs to be set into the body to allow those fixings.

See how far apart the screws /bolts on a Fender style neck are spaced - about 2 inches? They've done the hard work for you - it works. Space your fixings like this (2 are fine for a 3 or 4 string) and put a corresponding block under the end of the neck to fix thu' and it will be good. You don't need to weld bolts to the neck reinforcement or add a heel...keep it simple, don't make it hard on yourself.

Rand - the reason you needed to add a heel was that the fixing block simply doesn't project into the box enough and couldn't resist the twisting moment (engineering term for a force that's trying to turn something) exerted by the strings - by the way, that internal backing board is adding no significant strength to the joint. A bit more solid timber blocking inside the box isn't going to hurt the sound as long as you keep it away from the vibrating top, and guitars always work better when they don't fold in half when strung up.

• ▶ Reply

Permalink Reply by ChickenboneJohn on October 6, 2010 at 6:23pm

Rand, I'd leave the heel, (unless it offends you greatly), and just try a a different idea on the next one. To prettify it you could probably take the screws out of the heel, profile and re-shape it a little and put the fixings back in. It's obviously added some strength back in where it's needed, so don't take too much off!

If the existing neck only projects a little into the box (about an inch or so?) as per your drawing, you'd have to make a new longer neck or slide the existing one in maybe an inch or more to increase the bearing where you are screwing into the bigger internal block. This will shorten the scale length (a problem if you've fretted it or marked the frets), or you'll have to shift the bridge position back by a corresponding amount. Both of these may have some effect on the sound, so it will be nigh-on impossible to gauge what's changing the sound.

Once you start tinkering with two things at once. (ie putting a bigger heel block in AND moving the bridge or shortening the scale) it's hard to know what it really having an effect. To really assess what difference a change makes, you need to do one thing at a time. It's just being methodical..but that doesn't suit everyone, and quite often a bit of serendipity and luck works best!

Good luck

• ▶ Reply

Permalink Reply by Mister Scott on October 7, 2010 at 1:31am

ChickenboneJohn said:

If the existing neck only projects a little into the box (about an inch or so?) as per your drawing, you'd have to make a new longer neck or slide the existing one in maybe an inch or more to increase the bearing where you are screwing into the bigger internal block.

John, what is the optimal amount of bearing for the screws/bolts? 2 inches? 3 inches? Does it increase with longer necks?

• ▶ Reply

Permalink Reply by Rand Moore on October 7, 2010 at 2:34am

Hi ChickenboneJohn.

Yes, I'm also rethinking my plans. In your drawing (neckjoint.jpg), you show a 2.5" overlap between the neck and the underlying support beam that spans the length of the cigar box. I only had a 1.0" overlap. So, to extend mine to have a 2.5" overlap, I'd have to move the neck down into the box another 1.5", which is feasible, but it would require that I move the bridge back another 1.5" to maintain the scale length. This means the bridge would move from 6" down a 9" long box to 7.5" (or from 66% down to 83% down the box (toward the tail piece)). I'm worried that if I do this the box won't resonate as well. I heard (read) that the bridge should be about 2/3s down the box. So, at this point I remain undecided about which way to go. As it is now, it sounds good and I enjoy playing it. Maybe I'll opt just to redo the heel so as to maintain the current sound.

My next head/neck assembly is already in process, and it is a laminate composed of 3 strips of wood that's 2" wide by 0.25" thick. I'm not sure what kind of wood it is, but it pretty and it seems fairly hard. Since I glued it up, the laminated neck is really rigid and is long enough to do a thru-neck. My problem in China is finding a source of good quality wood for building head/neck assemblies. I got this wood at B&Q, but they don't sell the 1.5" x 0.75" hard wood that you can get easily in the States from Lowe's or Home Depot. The other wood I got from a Chinese source was not kiln dried (wood is sappy). Anyways, if this new neck works out, I'll probably be doing a lot more laminated necks. With a 2" wide neck I'm thinking maybe a six stringer tuned DD-AA-dd or GG-DD-gg or maybe a 8 stringer long neck diatonic mandolin. Hmmm... Let me think about that some more...

Thanks for your suggestions.

-Rand



ChickenboneJohn said:

Rand, I'd leave the heel, (unless it offends you greatly), and just try a a different idea on the next one. To prettify it you could probably take the screws out of the heel, profile and re-shape it a little and put the fixings back in. It's obviously added some strength back in where it's needed, so don't take too much off!

If the existing neck only projects a little into the box (about an inch or so?) as per your drawing, you'd have to make a new longer neck or slide the existing one in maybe an inch or more to increase the bearing where you are screwing into the bigger internal block. This will shorten the scale length (a problem if you've fretted it or marked the frets), or you'll have to shift the bridge position back by a corresponding amount. Both of these may have some effect on the sound, so it will be nigh-on impossible to gauge what's changing the sound.

Once you start tinkering with two things at once. (ie putting a bigger heel block in AND moving the bridge or shortening the scale) it's hard to know what it really having an effect. To really assess what difference a change makes, you need to do one thing at a time. It's just being methodical..but that doesn't suit everyone, and quite often a bit of serendipity and luck works best!

Good luck

• ▶ Reply

Permalink Reply by Mister Scott on October 7, 2010 at 2:50am

Rand Moore said:

Anyways, if this new neck works out, I'll probably be doing a lot more laminated necks. With a 2" wide neck I'm thinking maybe a six stringer tuned DD-AA-dd or GG-DD-gg or maybe a 8 stringer long neck diatonic mandolin.

Laminated necks are fab. Not only are they quite strong, you get people asking "How'd you do that??"

John, I see that your picture says approximately 2 and a half inches, which answers my first question. Does a longer neck mean longer bearing space?

• ▶ Reply

Permalink Reply by ChickenboneJohn on October 7, 2010 at 3:14am

I like to have about 2 inches between the screw fixings in a 3 or 4 string guitar (which is pretty much what Fender use).

It's not so much the length of the neck as the tension on it, so high tunings and heavy strings exert higher forces. If you think about how much rigidity a neck thru' construction gives you, and how stiff the neckstick is, I'm shooting for a similar sort of strength, hence a decent overlap between end of the neck and the heel block or thru' block. Wider spacing on the fixings gives more strength/less stress on the joint fixings, but 2" spacing works well.

Scotty C. said:

ChickenboneJohn said:

If the existing neck only projects a little into the box (about an inch or so?) as per your drawing, you'd have to make a new longer neck or slide the existing one in maybe an inch or more to increase the bearing where you are screwing into the bigger internal block.

John, what is the optimal amount of bearing for the screws/bolts? 2 inches? 3 inches? Does it increase with longer necks?

• ▶ Reply

Permalink Reply by MichaelS Country Boy Guitars on October 8, 2010 at 2:18am

How about extending the board that the neck bolts to outside the box and bolt it from underneath just in front of the box, were a heel would be, would make it easy to remove neck without taking the box apart, or opening it. Like a Fender or other electric.

• ▶ Reply

Permalink Reply by Ted Kaczynski on October 8, 2010 at 5:51am

CBJ Does it mater if the screws are coming in from the top or the bottom?

ChickenboneJohn said:

Here's my sketch.

• ▶ Reply

• ‹ Previous
• 1
• 2
• 3
• Next ›
• Page