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My first 8 builds have the truss rod adjustment at the peg head. The last 8 or so have been adjustable at the sound hole. The truss rods I use can be installed at either location for adjustment. The instructions say that the rod should not enter the body. This makes sense because the major portion of the rod needs to be supported by the fingerboard above and the neck below I know I can extend a tenon from the neck into the body to the upper transverse brace and bring the adjusting nut right up close to the sound hole for easy access but that puts the other end of the 14'" rod around the 3rd fret. Is the simple answer just to add the neck tenon and use a longer truss rod? If I did that, I would need a rod that is about 16"or so. Stewmac has the 14"that I use but the next one is 18" and that is tooooo long. A 2 way would be nice. These are 14 fret to the body acoustic guitars with bolt on necks.

This is what I am talking about...



Thanks, Michael

You don't really want to do that. What is supporting your extended tenon against the downward force of the truss rod ends under load? I can see where a channel in a tenon can help guide an allen wrench to the adjustment nut, but stop the truss rod in the neck block at the very most and better yet stop it at the neck tenon. If you really want to see what will happen if you don't, get Mark Blanchard to make you any size truss rod you want or make your own Cumpiano style rod.

_________________
Ken Franklin
clumsy yet persistent
https://www.kenfranklinukulele.com

Several guitar brands have the adjustment right there close to the sound hole. I sell Yamaha guitars at my store and that is where the adjustment is. It is very convenient and it works. I don't want to tear up a guitar to find out how they do it.

My "theory" is.. Install the long rod in a neck that has a tenon like this one.



This is an early experimental build of mine with with an adjustable neck joint. The truss rod adjustment is at the peghead on ths one.

Michael

Best 2 way rod out there.
You can mount the barrel bolt outside the tenon if you have to but I do it the same way Martin does. Todd and I do it alike. It works .

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Here is a solution I came up with to deal with that issue. It still needs finessing but I think that it will work. I used the stewmac 18" rod on a 25" scale neck. The rod runs the entire length of the neck from nut to the 22nd fret. The neck has a 3/4" thick extension that runs from fret 14-22. This supports the rod then entire length. To also support the tension, I have put an extension on the headblock that runs nearly to the soundhole. I was warned that the extra tension on this style headblock could cause issues because there was no transversal brace, So I cut a slot in the headblock extension and tied the transverse brace directly into the headblock so that it would distribute the tensions across the top all the way to the sides. Ive yet to string it up yet but I think itll hold together. The most difficult part was carving out the soundboard and headblock extension to recieve the neck. Its almost a cross between an electric and acoustic joint. Imagine an electric neck with a heel and tenon. Anyhow here are some pics

top view of the neck with truss rod


side view of the neck


here is the headblock and such


Here is the soundboard/heelblock area carved to recieve the neck.


I know its a very strange way to go about things but it made sense to me at the time of planning. We will see how it turns out.