Results 1 to 9 of 9

Thread: Truss Rod retrofit

  1. #1
    Registered User James Sanford's Avatar
    Join Date
    Sep 2005
    Location
    Fayette, AL #35555
    Posts
    372
    Blog Entries
    1

    Default Truss Rod retrofit

    I recently built a mandola with H5 scale length and used a Martin guitar truss tube (square) for the truss rod. This did not work due, I think, to creep in the epoxy I used to secure the tube. Subsequently, the neck bowed significantly and being non-adjustable I had to decide how to fix the problem.

    I decided to retrofit the neck with an adjustable truss rod which I have finished. I used the L shape Siminoff design as shown in his H5 plans.

    My question.....The fingerboard is still off of the neck, should I set the initial backbow before replacing the fingerboard or wait until it is reglued? Pros? Cons?

    FWIW Just an observation for future builds... I will absolutely use only adjustable truss rods in the future due to my experience on this and other builds I have made. The non-adjustable truss rod is fine as long as you do not experience the slippage problem I ran into. And I do not understand the best methods or products to use for the non-adjustable rod.

    Thanks in advance for any help.
    James A. Sanford

  2. #2
    Café habitué Paul Hostetter's Avatar
    Join Date
    Sep 2003
    Location
    Santa Cruz, California
    Posts
    6,286

    Default Re: Truss Rod retrofit

    Knowing how well that square tube worked in so many thousands of guitar necks, I find it a bit incomprehensible that creep of epoxy was to blame for your situation. Those square tubes worked great even when just pressed in. I would be more inclined to think that the mortise for your rod had slop, or that the epoxy was badly mixed, or possibly both. Good epoxy properly mixed should kick quite hard and only have the possibility of creep if it's really warmed up—hot to the touch.

    Lots of old Gibson mandolas are doing quite well with no trussrods at all, sometimes just a maple insert into a mahogany or cedar neck, sometimes with a piece of ebony. I've reinforced lots of necks with carbon fiber bars, again, no bowing or slippage. I have to wonder about the tolerances in your mortises. Tight joints shouldn't slip, even with mild glues.

    That said, an adjustable rod is a good idea. You should set it into a neck that's dead flat at rest. If and when string tension pulls the neck up, you can simply adjust it back with the rod.

    What wood is your neck made of?
    .
    ph

    º º º º º º º º º º º º º º º
    Paul Hostetter, luthier
    Santa Cruz, California
    www.lutherie.net

  3. #3
    Registered User Greg Mirken's Avatar
    Join Date
    May 2008
    Location
    Nevada City, CA
    Posts
    315

    Default Re: Truss Rod retrofit

    I agree with Paul that the square tube should have been plenty stiff. I would also question what you used to glue the fingerboard to the neck; I suspect the slippage of that joint contributed much to your neck bow. The most popular epoxy for luthiery is West Systems; I have used it for a long time and it cures rock hard. I would also use that or hot hide glue to attach your fingerboard.
    Shade Tree Fretted Instrument Repair, retired
    Nevada City, California

  4. #4
    Registered User James Sanford's Avatar
    Join Date
    Sep 2005
    Location
    Fayette, AL #35555
    Posts
    372
    Blog Entries
    1

    Default Re: Truss Rod retrofit

    Paul,

    thanks for your response. I expect you are right on two counts. Bad tolerance in the slot and poor mix of epoxy. I lack good tools for cutting the truss rod slot so this will be a target for future tools. The epoxy was in a two cylinder hypodermic type container and I eyeballed it the best I could. What is the correct way to get an accurate mix?

    The neck is maple with no other material sandwiched etc. I expect I may have made the neck too skinny as well.

    So many things to know how to do.................. (sigh)
    James A. Sanford

  5. #5
    Registered User James Sanford's Avatar
    Join Date
    Sep 2005
    Location
    Fayette, AL #35555
    Posts
    372
    Blog Entries
    1

    Default Re: Truss Rod retrofit

    Greg,

    Thanks for your info. I use Elmer's white glue. I never have worked with Hide glue. I guess I will have to experiment in this area as well. I will look into the West Systems expoxy.
    James A. Sanford

  6. #6
    Café habitué Paul Hostetter's Avatar
    Join Date
    Sep 2003
    Location
    Santa Cruz, California
    Posts
    6,286

    Default Re: Truss Rod retrofit

    I asked about neck material because maple, particularly, has a tendency to backbow owing to the water in water-based glues. Given that, I'd recommend a very precise and light dose of heated hide glue, applied and clamped very quickly, or just glue the board on with epoxy.

    The 12-hour Devcon in the twin syringe thing is very good glue. The preciseness of the match of A to B isn't critical, but do your best to get an equal puddle of each. It flows best when it's warm. Where it tends to fail is when the A and the B aren't mixed thoroughly enough. The nice part about 12-hour is you can really take your time mixing it, and finishing the setup and clamping. Epoxy was once considered "not done" for applications like this, but to be honest, it's easier to undo with heat than most other glues, particularly aliphatics. It comes apart as well as heated hide.

    If you use epoxy, keep the palette you mixed it on so you can see 12 hours later how hard it is. If you can flex the remains, it wasn't mixed well enough, and you might as well apply some heat and take it apart and start over ASAP. If you got the mix right, the remains on that palette will be hard and brittle and will snap.
    .
    ph

    º º º º º º º º º º º º º º º
    Paul Hostetter, luthier
    Santa Cruz, California
    www.lutherie.net

  7. #7
    Café habitué Paul Hostetter's Avatar
    Join Date
    Sep 2003
    Location
    Santa Cruz, California
    Posts
    6,286

    Default Re: Truss Rod retrofit

    I would upgrade to Original Titebond (not Titebond II or III!). Elmer's is simply too weak for real use.
    .
    ph

    º º º º º º º º º º º º º º º
    Paul Hostetter, luthier
    Santa Cruz, California
    www.lutherie.net

  8. #8
    Registered User j. condino's Avatar
    Join Date
    Nov 2005
    Location
    Asheville, NC
    Posts
    2,758

    Default Re: Truss Rod retrofit

    James:

    The other folks all gave reasonable responses to your truss rod dilemma. My comment has more to do with the idea of "lacking the proper tools" to cut the truss rod slot. Some folks visualize a process in terms of a specific tool to get the job done- the big name cataloges and suppliers make a LOT of money off this concept. I tend to look more at the end result: I need a small channel cut in the neck- what is handy and what do I have a reasonable amount of skill and experience with. I can cut an fantastic truss rod channel in about ten minutes with an exacto knife; the same amount of time with one of my favorites- a vintage Stanley 271 router plane; or about ten days with a fancy new router bit and template jig ordered from one of the big corporate guys- 9 days and 7 hours for it to get packaged and shipped to me and the 30 seconds to make the fancy cut ( provided it actually works and does not send my instrument flying across the room at 90 mph!!!).

    A GREAT mentor of mine spent about ten minutes mocking me one day when I showed him my fancy cataloge ordered $400 flywheel type rosette cutter. Then he showed me how to make an absolutely perfect and beautiful rosette channel in 30 seconds using an exacto knife blade, a popsicle stick, and a thumbtack....I'd guess that you've already got everything you need sitting right in front of you!

    j.
    www.condino.com

  9. #9
    Registered User James Sanford's Avatar
    Join Date
    Sep 2005
    Location
    Fayette, AL #35555
    Posts
    372
    Blog Entries
    1

    Default Re: Truss Rod retrofit

    Quote Originally Posted by grandcanyonminstrel View Post
    James:

    The other folks all gave reasonable responses to your truss rod dilemma. My comment has more to do with the idea of "lacking the proper tools" to cut the truss rod slot. Some folks visualize a process in terms of a specific tool to get the job done- the big name cataloges and suppliers make a LOT of money off this concept. I tend to look more at the end result: I need a small channel cut in the neck- what is handy and what do I have a reasonable amount of skill and experience with. I can cut an fantastic truss rod channel in about ten minutes with an exacto knife; the same amount of time with one of my favorites- a vintage Stanley 271 router plane; or about ten days with a fancy new router bit and template jig ordered from one of the big corporate guys- 9 days and 7 hours for it to get packaged and shipped to me and the 30 seconds to make the fancy cut ( provided it actually works and does not send my instrument flying across the room at 90 mph!!!).

    A GREAT mentor of mine spent about ten minutes mocking me one day when I showed him my fancy cataloge ordered $400 flywheel type rosette cutter. Then he showed me how to make an absolutely perfect and beautiful rosette channel in 30 seconds using an exacto knife blade, a popsicle stick, and a thumbtack....I'd guess that you've already got everything you need sitting right in front of you!

    j.
    www.condino.com
    You are, of course, correct in what you say. I tend to the "lazy" side and always look to the power tool part of the equation. (remember Tim "the tool man" Taylor) That's me I guess. The thing I really learned from this discussion is that the slot should be cut for a tight fit when using a non-adjustable rod. My approach was to leave room for the adheasive which I now see was incorrect.

    Thanks for your observations.
    James A. Sanford

Bookmarks

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •