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Run into a bit of a snag on a 6 string CBG build.

Posted by carverman on November 4, 2010 at 10:01am in Building Secrets, Tips, Advice, Discussion

I've run into a snag on my first 6 string CBG build. I didn't have any problem with the headstock 

 offset of 15 degrees and the scarf joint, thanks to a previous poster who had pictures posted

of how it is done. B ut now...I have a tech issue that the FB will be on a horizontal 180 degree

 plane and the acoustic homemade bridge that I  plan to use is going to be too high for a

flat glued FB.

 

The typical neck offset on a Les Paul is about 4.5 degrees from the horizontal plane to allow

 lower action when the "tuna-matic" bridge is installed.  

I'm thinking of adding a sloped wedge of wood on top  to create the 4 degree offset on the

 FB that will allow a closer action.

 

 

CBGa.jpg

CBGb.jpg

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Replies

  • carverman November 11, 2010 at 4:39pm
    Ok, thanks Wes. Yes the lid itself (Thomas Hinds CB) is only 4mm thick (plywood) which
    corresponds to slightly more than 1/8"thick at 0.157". There is a 1/2"L x 1/4" thick
    "border" or "ring" which gives the lid some strength, and the hinges and clasp are
    attached to it. I've already cut some slots in the top "border"
    or "ring" and the lid is actually flush with a 1/4" FB temporaily clamped to the neck.
    I presume that with the acoustic bridge I made, this will give me decent action to the
    20th fret or so, but not sure yet.

    Then there is this 2 degree slope that I need to work out to set the CB at that angle.
    Is this necessary?



    Wes Yates said:
    Ok, so your lid is 1/8" thick? Hmmmm. Most (not all) boxes are around 1/4" thick give-or-take. So you might have taken off too much then. You can add a 1/8" shim to bring the lid flush with the top of the neck. Then the fretboard will be flush with the lid. In reality I have a 1/32" gap between the fretboard and the lid so the lid will vibe and make more sound but that is up to you.



    carverman said:
    Hello again Wes.

    I reshaped the neck area where it enters the CB as per the drawing. The only question is
    the "1/4 lid recess". Is the 1/8" thick plywood lid (which is hinged btw) supposed to be flush
    with the FB or down into the recess slightly. I suppose I can figure it out trial and error,
    but maybe a reply from an experienced builder would save me some test fittings in that
    area.

    In other words..if I temporarily tack down 1/4 " thick FB..is the surface of the lid supposed
    to be flush?

    Thanks,



    Wes Yates said:
    ok so one way to do this is to remove the neck -- assuming you didn't glue it and cut away some of the neck top where it is inside the box:

    .
    You might have to add on some reinforcement on the bottom. I will see if I can find the cleaner pic

    -WY

    BETTER ONE:


    email me and I can send it to you.
  • Wes "I'm Baaaaack" Yates November 11, 2010 at 3:55pm
    Ok, so your lid is 1/8" thick? Hmmmm. Most (not all) boxes are around 1/4" thick give-or-take. So you might have taken off too much then. You can add a 1/8" shim to bring the lid flush with the top of the neck. Then the fretboard will be flush with the lid. In reality I have a 1/32" gap between the fretboard and the lid so the lid will vibe and make more sound but that is up to you.



    carverman said:
    Hello again Wes.

    I reshaped the neck area where it enters the CB as per the drawing. The only question is
    the "1/4 lid recess". Is the 1/8" thick plywood lid (which is hinged btw) supposed to be flush
    with the FB or down into the recess slightly. I suppose I can figure it out trial and error,
    but maybe a reply from an experienced builder would save me some test fittings in that
    area.

    In other words..if I temporarily tack down 1/4 " thick FB..is the surface of the lid supposed
    to be flush?

    Thanks,



    Wes Yates said:
    ok so one way to do this is to remove the neck -- assuming you didn't glue it and cut away some of the neck top where it is inside the box:

    .
    You might have to add on some reinforcement on the bottom. I will see if I can find the cleaner pic

    -WY

    BETTER ONE:


    email me and I can send it to you.
  • carverman November 11, 2010 at 3:26pm
    Hello again Wes. I reshaped the neck area where it enters the CB as per the drawing. The only question is the "1/4 lid recess". Is the 1/8" thick plywood lid (which is hinged btw) supposed to be flush with the FB or down into the recess slightly. I suppose I can figure it out trial and error, but maybe a reply from an experienced builder would save me some test fittings in that area. In other words..if I temporarily tack down 1/4 " thick FB..is the surface of the lid supposed to be flush? Thanks,


    Wes Yates said:
    ok so one way to do this is to remove the neck -- assuming you didn't glue it and cut away some of the neck top where it is inside the box:


    .
    You might have to add on some reinforcement on the bottom. I will see if I can find the cleaner pic

    -WY

    BETTER ONE:


    email me and I can send it to you.
  • carverman November 6, 2010 at 12:20am


    Rand Moore said:
    Hi Again.

    I just re-read your original post and you say you are planning to use a "tuna-matic" bridge.     No. I can't use the Gibson style tune-o-matic bridge on the CBG. It has the posts that anchor into
    solid wood and also a bit wider than my 2 inch piece of neck block inside the CB.



    What I was referring too..on my other builds of LP design, I did use commercial t-o-m and a stop
    tail piece and it simplified construction and neck/string angle. In this CBG build, I've decided
    to make a banjo style bridge instead.


    If you are using this kind of bridge, then forget my comments above (I saw the picture of the classically designed bridge and made an assumption - not a safe thing to do).


    Yes, the t-o-m bridge has 6 individual adjusters to set intonation..but having a movable bridger />
    like the banjo style shown in my picture, you can position it on the top of the CB at the appropriate
    scale point where its exactly the same measurement from the nut to the 12th fret and from the />
    12 fret to where the bridge needs to be to achieve correct string intonation.


    I once made one of these tunable bridges for a 4 stringer and found that it would require me to raise everything else (i.e. the fretboard) to maintain playable string height over the entire length of the neck. Mine was build on a little board about 1/4" thick. With the height of the mini bridges added in, it stood 7/8" off the board, which cause the string to rise off the neck at too high an angle such that beyond the 12 fret, the action was to objectionable.


    Yes, and I try to avoid this by using a test line (fishing line) from the nut then touching the
    bridge anddown to the end pin where the TP will be. This gives me a rough idea of
    how much to sand down the banjo style bridge, and what the string angle will be with
    the fret board just "tacked" in placetemporarily.

    As you discovered..if the string angle is incorrect at the start, the CBG will be
    next to useless to play beyond the first 3 to 5 frets.



    So, I removed the bridge and used a "standard" one as I described earlier. If I do this again, I will glue the tracks to the soundboard to save 1/4" there and try to cut the height of the mini-bridges by 1/8" to 3/16". By the way, my mini-bridges were held in only by string tension.


    I plan on doing the same, as movable style acoustic bridges shouldn't really be glued down.


    Thanks. I wouldn't mind seeing a pic of yours. Every idea I get helps me with my build.
    Even if the results from the first one are not what I expect, I will get a lot of experience
    from that to pass onto my second build.


    BR>
    -Rand.




    Rand Moore said:
    i>DIV>Hi Carverman,

    The bridge you are planning to use has a nice "classical" shape, but is pretty tall in my book. Why not just cut off the legs?
    Those "legs" were just there because when I cut out the bridge, I had no idea on FB angle or the
    string height. They are now sanded down considerably.


    Most of my CBG bridges I make are made of red oak and maybe 1/2 to 5/8 inches tall. The cross sectional shape is like a simple "house" made of a square and a triangle with slots cut for the strings through the "ridge of the roof" at appropriate locations. I think you'll get better (more) vibration transfer from your strings to the sound board (cigar box top) if the bridge is in full contact with the soundboard rather than standing up on legs.

    Maybe you are right. I came up with the idea from an archtop violin bridge/banjo bridge, and
    like any idea, it is subject to being modified as one goes along.

    Any opposing arguments? It seems to me a lot simpler a solution to change the bridge than to change how the neck attaches to the box. Just my 2 cents worth.
    Well, most instrument designs can have ideas incorporated on both the neck attachment and the bridge
    to arrive at a final workable solution.

    The mortice&tenon Les Paul neck has about a 4.5 degee neck offset to allow closer string action.
    The violin and acoustic guitars have a dovetail neck attachment at a particular angle as well.
    Whether there is a "right way" or a "wrong way", maybe that is debatable, but the most elegant
    solution is always desirable.

    Dan
  • carverman November 5, 2010 at 11:54pm
    Yes, I have built my own custom Les Pauls..semi acoustic or semi-solid, not sure which term applies,
    but they are very unique and one of a kind. I have made them from walnut/maple/walnut laminated
    necks with truss rods, carved flame/quilted maple tops, walnut sides and maple backs or padauk
    backs.

    I have pics of them together,but they are not CBGs..just some unusual neck through Les Paul designs.
    I carve birds/fish and animals, so hence the username.
    Dan


    Mungo Park said:
    That bridge is very much looks a banjo bridge. I think you can find no end of discussion as to what shape and what material makes the best bridge, but your idea of lowering it would make things more simple to fit together.
    Me thinks Carverman has built some string things before this CBG, but it is just spec.
    Cheers Ron.
  • carverman November 5, 2010 at 11:49pm
    I like this idea Wes. I
    will do the same with mine. I don't want to have too much bulk inside a small
    CB obviously, but since the 6 string TP has a fair amount of tension on it compared to a 3 or 4
    string, it needs more strength. My necks are laminated..spanish cedar/1/4 inch maple/spanish cedar.
    The fb will be either rosewood or some exotic wood like padauk or bubinga, that sort of thing.
    I also have black walnut, which makes a good fb.

    Dan



    Wes Yates said:
    Thanks, Mungo. I must admit tho, I too learned it from someone here, so not completely my original.

    One thing to note tho too, this drawing is using a laminated neck. You don't have to do that. sometimes I build with a single piece of 1x2 and an extra length on the bottom where the neck is inside the box. I glue that on, extending the 'tail' portion, cut a 2deg angle starting from the point where the neck enters the box, and then trim the tail thickness to 1" (.75"). Makes the tail and neck look the same thickness but if you looked inside, you would see the neck inside gets thinner from the neck side of the box to the tail side.

    I might be able to diagram that too.

    -WY
  • carverman November 5, 2010 at 11:44pm
    That's a left over TP from one of my Epiphone Emperor II jazz boxes. Since the string bar has the notches for the 6 string, I've decided to recycle it to save money and save having to make my own. It will be bent around 75 degrees and fasten to the neck tone block at the end. This way, if I have to get inside the lid to change the electronics, I can just slacken off the strings and pull the ball ends out to flip the lid up. Dan

    Rand Moore said:
    Hi again Mr. Carverman.


    What's that weird thing you're using for a tail piece in this photo?

    305679585?profile=original


    -Rand.
  • carverman November 5, 2010 at 11:41pm

    Yes, thanks for your reply. I haven't glued down the box yet, but installed the truss rod and glued down the anchor pin..but I can dig out that out and cut down the neck acording o the pic that Wes has shown. This will allow the edge of the FB to come over the box, but now of course, I have a new problem is that the fb will be in the way to open the lid. Something I didn't think about and not an issue on normal guitars. I suppose, I could cut the fb at the point where it comes in contact with the edge of the CB, or move the CB down a bit by extending the end of the neck tone block. This is my first and proto CBG..I will be making another from spanish cedar that will have a longer CB and incorporate some of the design features into it. I'm using some P-ups and a preamp rod piezo on it..but I'm already thinking it may be too much stuff to fit into a Thomas Hinds CB. Dan
    Mungo Park said:
    Wes has got it in spades, you can raise the neck up by how much you cut out and then when you put on the FB you should be where you want. I leave a 1" "shelf" for the lid to touch the neck and the rest is cut out so the lid is free to resonate, this of course is what I have learned from Wes.

    I see you have a Thomas Hinds box they work really well if you can find the big ones. They have a few stores in Canada but not many. I get mine in Winnipeg where I live.
    Cheers Ron.
  • Wes "I'm Baaaaack" Yates November 5, 2010 at 10:41am
    Thanks, Mungo. I must admit tho, I too learned it from someone here, so not completely my original.

    One thing to note tho too, this drawing is using a laminated neck. You don't have to do that. sometimes I build with a single piece of 1x2 and an extra length on the bottom where the neck is inside the box. I glue that on, extending the 'tail' portion, cut a 2deg angle starting from the point where the neck enters the box, and then trim the tail thickness to 1" (.75"). Makes the tail and neck look the same thickness but if you looked inside, you would see the neck inside gets thinner from the neck side of the box to the tail side.

    I might be able to diagram that too.

    -WY
  • Rand Moore November 5, 2010 at 8:45am
    Hi again Mr. Carverman. What's that weird thing you're using for a tail piece in this photo?

    305679585?profile=original

    -Rand.
This reply was deleted.