Broken Single Action to New Double Action Truss Rod

Hey all,
This is a non-tele question but I really wanted to tap into the vast expertise on this website to get the right answer to my question.

I have a Seagull cedar acoustic that I love. A roommate of mine took it upon themselves to fix the buzz in the Low-E and from what I could tell pushed the truss rod beyond its limits. The action was all over the place and a jazz professor of mine confirmed the truss rod is broken. I love this guitar and wanted to repair it. So i took the fretboard off and removed the truss rod. It was definitively warped beyond repair. The counter threads had been torqued so badly that little 1/8" dia rod couldn't take it. I even took it to work and had one of the welders try to reset the nut (the real easy rod)... no dice. Cest La Vie. So I bought a new double action truss rod from Stew Mac hoping it was going to be plug and play basically. Well it is about 1/16" taller than the old truss rod so I would have to rout the truss rod channel deeper. At that point it was really turning into a project and I shelved it till recently.

After doing a bit more research before I start making sawdust, I see that a single action truss rod requires a variable depth (curved) slot and a double action rod should be flat. I am no luthier and want to get some feedback before moving forward.

So can I rout the truss rod slot a bit deeper and put the double action rod in? Or is this approach destined to fail? Any feedback is GREATLY appreciated! Thanks

I am a Luthier and this is how I would do your repair.

I would just get a narrow chisel that is as wide as the truss rod slot and remove the required material to make it fit flush. You can scrape with the chisel to smooth the slot out. No big deal here the hard part is getting the old fretboard back on! Did you clean up the old glue off of the neck and fret board? Now's the time and re-check the fit!

I would also double check the placement of the adjuster end (probably in the sound hole.) to make sure that all of the original access holes line up.

To re-attach the fretboard to the neck I would suggest using tiny brad nails to help locate the neck before the glue goes on. Here's how I do it.

1) Temp clamp the fretboard to the neck with your alignment as close as possible to it's final position. You should make a clamping caul that is notched for the frets (so you are clamping the neck only, not the fret tops). You will probably need 4 clamps and one more that can make it in the sound hole. Make sure you use cauls and aren't clamping on the wood of the guitar directly or it will crush / divot your guitar.

2) Carefully remove the 3rd fret and the 14th (body joint) fret. Be careful to not gouge the fret wire with the fret pullers. You will reinstall them later so save them.

3) Find 2 brad nails that is about 1" long and smaller in diameter that the fret slot.

4) Find a drill bit that is the same size or just smaller than the brad nails.

5) With the fretboard clamped, drill 2 holes in to the fret slots (from the removed frets) off centered of the truss rod slot that go approximately .125 (1/8") into the the neck wood. Depending on the thickness of the fret board you will need to measure the drill bit and mark it with tape to keep from drilling to far.

6) Drive the brads very lightly into the holes till they are snug. Don't drive them home or you will be sorry! ;-)

7) Use some strong dikes / wire cutters and remove the nail head from the brads. Keep at least 1/4" of the nail exposed so you can pry it out later.

Now you have 2 points / pins that will locate the fretboard for you to glue it up. The reason why you do this is because once it's covered in Tightbond the fretboard will get squirmy and want to move around all over the place as you glue it.

8) Un clamp your fretboard and slide it over & off the nail barbs. Now you know why you cut the nail heads off. If you have done this right you should be able to remove the fretboard on / off the nail barbs. These are your locating pins.

Here I would double / triple check the clamping cauls and clamps with a dry run. Use wax paper to keep from gluing your clamping cauls to the guitar! ;-) Don't forget the tongue extension.

9) Put glue on the neck only!! Do not put any glue near the truss rod. Give it an even film and spread it with your finger. Tightbond is just fine here.

10) Using the brads as locating pins, slide the fretboard back on the neck (over the nail barbs) and put all the cauls, wax paper, and clamps on EXACTLY as your dry run. You have about 15 min or so here but don't be pokey (If using Tightbond). DO NOT OVER TIGHTEN THE CLAMPS!! With the water content in the glue (swelling the fibers) and the clamping pressure you can crack the fretboard!!

11) Clean the squeeze out glue with damp (not soaked) paper towels. Get the sloppy stuff right away. You can come back in 15 to 20 min to get the rest.

12) Double check the alignment of everything!! If something is wrong now's the time to correct it. If not, wipe up any remaining glue residue with damp paper towels.

This is an overnight glue joint. Don't rush it.

The next day, remove all the clamps and pry out the brads. I recommend using the cross cutter for nipping fret ends. I usually put a paint stick under it to keep from denting the fret board. The brads come right out no problems. Just grab and pull.

Reinstall the 3rd fret and the 14th fret.

You will really need to do a level, crown, and polish at this point regardless of how you attached the fretboard back on the neck. Everything will have changed slightly and the glue's water base will have swelled the fretboard slightly. You may even need to shim or make a new nut depending on how things are after the whole thing is back to gather and dry. Pretty much I would do a whole setup including level, crown, polish, bone nut and saddle. But that is what I would do at my shop, you make your own call depending on how it turns out.

If you have never done fret work, or attempted this kind of repair you may want to take it to a shop. Otherwise just perform the level crown polish as normal.

If you want to tackle the fretwork on your own and haven't done it before, I suggest looking at the many You Tube videos or visit www.stewmac.com and buy their essential fretting kit and instructional videos. It's not that hard, just time consuming.

Good luck. Half the battle was getting the fretboard off the guitar.

Since this is a Seagull guitar I would also consider double checking the neck set angle. Since you have it apart this becomes a lot easier. The neck is bolted on (unless it's very new) with the exception of the tongue extension on the sound board. If you have the fretboard off it should be easy enough to remove the neck the rest of the way (the 2 bolts are under the label on the head block). I would clamp and glue the fretboard on the neck with it removed from the body.

At this point I would add a degree or two of set angle to lower the effective action if needed. To check the neck set angle, make a straight edge out of aluminum bar stock (The Home Depot & Lowes sells this) with notches to clear the frets and the bridge saddle. The idea here is the straight edge only touches the wood of the fretboard and bridge. Bolt the neck back on (don't glue down the tongue extension yet!). If the neck set angle is correct, the straight edge will lay flat on the fretboard and the top of the bridge with no light showing. You will have to adjust the truss rod so the neck is flat to check this. You can pull 120gr sand paper strips through the neck joint (unbolted held on by hand) to take away heel material as needed. Make sure to tape over the finish as to not damage it. A little adjustment goes a long way so be careful. Once you are happy, bolt the neck back on and glue down the fretboard tongue extension. Then I would do the fret dress last.

A lot of this is a "Depends" situation as to what is needed. The guitar will tell you but you have to check it as you go.

Good luck. Not hard work just very time consuming / labor intensive. You will probably save $400 in labor as this is a lot of hand work. Considering you can BUY a new Seagull for less you are saving money. The experience gained is priceless.

-Mike R-

^^^ What he said.............then fire the roomate!

They make little hand tools called router planes that would be ideal for this type of hand chiseling. It is a cast base with an adjustable chisel. The small one in the pic is the one I'd try.
http://www.inthewoodshop.com/ToolReviews/The%20Veritas%20Small%20Router%20Plane.html You would just remove material until the rod drops in. After all the glue is removed off the surfaces you reglue. Many of the challenge threads have this step done if the folks used a separate fingerboard. Check them out.

Probably if this were mine, I'd do it the hard way and make a 1/4" thick plywood jig that would support a laminate trim router and have a fence to guide it straight. The plywood would be held onto the neck surface with double sided tape. I'd use the acoustic hot rod bit and hot rod from stew mac.

Seagull guitars are great bang for the buck and this one is worth the time to make it work again.

The hard part is getting the old fretboard back on! Did you clean up the old glue off of the neck and fret board? Now's the time and re-check the fit!

Mike, Thank you for your VERY detailed reply. This helps immensly. To provide some more details about my situation I was pleasantly surprised to find when removing the fretboard that seagull installs two steel pins to align the board to the neck. This will make re-alignment a dream, its a very tight fit I did some measuring and the most slop I could induce in the neck with these pins installed by pushing the fretboard to the side is under 1/32". So I am not planning on using brads or removing any frets when re-installing. Thank you Seagull for saving me a few steps!

See the attached images.

I have the cleaned the fretboard and I have sanded the faying surface of the neck that mates to the fretboard. I have not yet figured out how to best clean the old glue out of the truss rod slot. I tried a file but I dont have a real good method to keep it perpendicular and don't want to round the corners. Any suggestions? Is the router plane the way to go at this easy?

The replacement truss rod I did purchase IS in fact a hot-rod from stewmac and I will try to get a .225" dia router bit per thier suggestion. If I can not find it... will the extra .025" slop be an issue? because I already have a .250" dia router bit.

Roommate is long gone... the wifey wants me to actually complete a project for once. LOL!

***EDIT***
I got out the old calipers and the router slot is already at .250 in width. So I purchased a small router plane on Amazon and will tackle that task this weekend. It seems like this will make the job of both removing the glue and shaving off that small amount of material a breeze. Like my Dad always said "Use the right tool, for the right job"

If you read down that link, you'll see them grinding allen wrenches into narrower cutters.

If you're not already committed to the Stew Mac truss rod, they make smaller ones. I believe these require about a 1/16th less depth: http://www.lmii.com/CartTwo/thirdproducts.asp?CategoryName=Truss+Rods%2FNeck+P arts&NameProdHeader=Truss+Rod+%2D+Double+action+welded+ nut

Don't over think the truss rod slot. With the double action truss rod it doesn't have to be down to the thousandths. It just needs to fit well. The main thing to remember here is that you don't want to get glue on the new rod. I would just find a narrow chisel that fits the slot and clean / deepen it until the new rod fits.

Seagull basically made production what I do to build acoustics. That is really cool. Since I am about 90% sure the neck is bolted on, I would recommend peeling off the label on the head block and unbolting the neck.

This gives you the advantage of getting enough clamps in place without damaging the body. When I build, I glue the fretboard on to the neck first. Then the whole thing gets fit to the body (i.e. neck set angle and center). Once I got that, I attach the neck (bolt on or French dovetail) and glue down the tongue extension (the part over the soundboard) all in one process. Dry runs are essential to make sure you don't screw the pooch.

Here are some photos of when I attended the Galloup School of Lutherie. There are a lot but you will find some photos useful as they show some of these steps.

http://s1205.photobucket.com/albums/bb428/mrench01/Galloup%20School%20of%20Lutherie%20Big%20Rapids%20 MI%202011/

With the neck off (and before you attach & glue the tongue extension to the body), I still highly recommend double checking the neck set angle and even adding a degree or two. This will give you more room in the future to lower the action later as the top loads with string torque. If the Bridge Saddle is lower than .125 (1/8") between the D and G strings the neck probably needs reset. The notched straight edge I recommended making earlier will tell you this also.

The strings must have enough break angle over the saddle or the tone will suffer greatly. As the top bellies and the bridge rises most people will file the saddle down. This is OK to a point, that point is .125 for me. I have seen more butchery on acoustics to deal with neck set issues. The worst is filing down the entire bridge. The strings at E standard tuning put about 140lbs of tension across the entire guitar. Thinning the bridge makes it weak and eventually it breaks at the saddle.

For the life of me I will never understand why the acoustic guitar manufactures don't add more set angle in the first place. Almost ALL acoustic guitars will have some amount of top loading (bellying) and it's actually desirable. As this happens over time the saddle needs to be lowered to get the action back. I will also never understand why manufacturers EPOXY the dam neck joint on!!!! Bolt on or Tightbond is fine. Bolt on should be an industry standard for all guitars under $500. Because the cost of a neck reset will come close to the price of a new guitar. Be warned, as of 2012 Seagull / Godin started epoxying the necks on. While it can still be removed, you have to cut the neck joint apart and convert it to a bolt on. Not even worth the money IMHO. I can't stand it when the guitars are treated like disposable items by the companies who make them.

Of the 4 truss rod replacements I have done, 3 were acoustic guitars. All 3 were broken because the owner tried to lower their action with the truss rod. This is a big no no!! The truss rod sets neck relief not the action. It does have an impact on the action but it's not the way you set action. Action is set by the saddle height.

I am sure you will get it back together. All this "scary" stuff really isn't that difficult. It's just time consuming. Good luck!

Cheers!

-Mike R-