so, i did a bit of a search but couldnt find anything definite .
How / where do i layout the truss rod channel? neck is scarf joint and will have a fretboard . i find lots of pictures of channels and rods in channels but not how to place it on the neck . will post pics of truss rod adjustment end later.
Obviously, you'll need access to the adjuster nut on a truss rod once it's installed. That pretty well dictates where the rod must be placed. You'll find some removable guitar necks that have the adjuster at the lower end of the neck. Actually, this is a bit of a pain in the ass to access and adjust.
More commonly, the end of the adjuster nut will be right at the back edge of the guitar's nut. Then, the groove extends pass this point a bit onto the head stock so you can get an L shaped wrench on it once installed. A wooden or plastic cover is installed over the grove for appearance.
Actually a more important thing to consider is Truss rod length. Depending on how long your neck is and how thick it is, you may need a fairly long truss rod. In practice, since cigar boxes are relatively small compared to more traditional guitars, you usually have a lot of neck sticking out past the box and neck :"heel". In a case like that you may need a truss rod as much as 17" long. Too short a truss rod on a long skinny neck just moves the point at which the neck is going to bend.
All that being said, do you really need a truss rod? For three and four stringers with maple or mahogany necks, there isn't usually a need for a truss rod. Softer woods and/or more strings and a truss rod may be needed.
I've used truss rods as short as 12" and as long as 17". Just depends on the build and the neck design.
Hopefully, some other folks will jump in with some more insights.
Most 3 string guitars at 25.5" scale or less won't need a trussrod, but it depends on whether the scale length is long(27" or more), if it's a guitar or bass and what the strength of the wood your using is. If the neck is Pine or Poplar, then you might need a trussrod.
Most of my guitars are 4 string and 25" scale. I use Red Oak necks with Red Oak fretboards. I put a non-adjustable trussrod in each one that extends from middle of first fret to nut area to the 15th or 17th fret depending on where the heel begins. I use a 1/8th" by 3/8th" steel flat bar as my non-adjustable trussrod, cut a channel just bigger than 1/8" wide and just deeper than 3/8" deep, put it in and use toothpicks to lodge it in so it won't rattle and then glue the fretboard on. Just make sure the steel rod is straight first.
A adjustable trussrod on a CBG is probably better to be adjusted at the nut area than the heel area depending on how the construction of your CBG is done. I like the adjustable trussrods that are fit into a aluminum channel better the other types because the adjustment force is applied to the channel rather than the fretboard and the chances of a broke/cracked fretboard are greatly diminished.
Hi Tim, pretty much what Paul says. The type of rod most popular and the type I use on 6 string guitars is the type that is made of two rods welded one end and threaded on the other. They come in single or double action.
For any type of rod I use I cut the channel so that the truss rod is a firm push fit and sits about 1/8" below the surface, then a wood fillet is glued on top of the rod and the fingerboard on top of that.
if just using a single threaded rod anchored one end and threaded at the other, it should be fitted nearer the bottom of the neck, (in a deeper channel) to work efficiently.
However as Paul says if neck timber is a suitable hardwood you should not need one. If you did then I would use something like 3/16 or 1/4" x 1/2" steel or aluminium bar, a tight fit in its channel.
This is what I used in my early 6 string guitars I built in the late 1970's, with two I still play the necks are still perfect.
thanks guys, @Taff. this truss rod if for the 30" 3 string bass i am making. i got a long truss from ebay. https://www.ebay.com.au/itm/52cm-Length-0-9cm-Dia-Guitar-Truss-Rod-...
my first truss rod install and probably the last! i will stick to gits and ukes from now on. but i think i really do need the extra help of a truss rod for the bass.
Hi Tim, just a silly heads up......before installing check for smooth opporation and which way it bends so it's the right way up in the channel. I put it in a vise to do this.
I pretty much do it like Paul and Taff but I stuff a 1/4" or 1/2" round steel rod in there.
I believe for bass, you would need to install 2 of the rectangular steel rods on each side of the neck, with the truss rod in the middle.