Takamine F400 bridge plate and brace issues

[John Yungbluth]

Takamine F400: Submitted for your consideration........

Looking for a little in-depth conversation on repairing a 1975 Takamine F400 12 string. Her back history is unknown. I plan to approach the body issues and finish with a neck reset if required.

I've already repaired a loose sound hole flat brace on the treble side, the traverse bar on the treble side about 3/4" and a broken out 2" piece of the top kerfing that spanned that end of the traverse bar. This is where I stopped to re-evaluate how and in what order I need to proceed.

Material:

All laminated body, spruce top, rosewood sides and back, Laminated bridge plate. Neck is mahogany, no scarf joint on headstock, 2 additional stacked pieces for the heel. Rosewood fingerboard and bridge.

Initial look at the issues:

Sinking top starts behind the end of the fingerboard and goes across the sound hole then rises back up to the X brace joint. The sinking area crosses the sound hole, flat sound hole braces, but rests between X-braces.

The bass side X-brace is sprung loose from the top at the side radial brace one, through two all the way to about the last 1 1/2 -2" length. The rest of both X-braces are still solidly attached. From what I can see under no string tension the two tone braces and the remaining radial braces are all secure.

Bridge was loose from the back edge through bridge pin holes. And the back edge rose up, off the top, above the bulge of the belly as the bridge leaned forward. The bridge has been off before, repaired and was failing again. I removed it completely. No cracks in the bridge, bridge footprint or that I can discern in the bridge plate.

Belly starting about midway through the bridge in front of the pin holes and high points at about an inch behind the bridge tailing down to the tone brace one.

***Unique issue with the bridge plate:***

The bridge plate has a unique issue. I was reaching inside and probing with my fingertip. The leading edge seemed thicker than the trailing edge. Made a crude depth gauge I could get inside. When I took thickness measurements of the bridge plate the trailing half of the bridge plate is less than the leading edge by about .13: I applied clamping pressure to the leading edge and could see the movement in the bridge plate down as I added pressure against the top. The back half of the bridge plate is solidly attached to the top, the leading part is not and sprung loose from the top.  I can't get a feeler gauge under it because of the height of the X-brace.  Not sure how to work Titebond Original into that gap to secure the plate to the top again.

HOW WOULD YOU APPROACH THIS?

And in what order of repair?

Bridge plate:

You are into the tight workspace of where the X-brace and bridge plate draw close to each other. I can't think of how to work glue into that loose end of the bridge plate and deeper into that unknown depth to stabilize the repair. Replace the bridge plate? But working inside to remove a laminate plate against a laminate top, is a potential disaster for the top if done poorly.

Opinions, alternate approach?

Sinking top, live with what has been inflicted. Bridge, bridge plate and X-brace repairs should lift a little, maybe. Add a taller bar shaped brace to stiffen each side? All these would slightly raise the top and even more necessitate a neck reset

X-brace is a repair I've done many times and comfortable doing them.

It's a juggling act to put these issues in a progression of repairs as well as how to repair that bridge plate.

Anyone ever do a neck reset on this model and have first hand experience with it being a dovetail, Mortise/Tenon or butt & Dowel joint.

[Carl Dickinson]

I'd think that removing the back would give access to all of those issues except how the neck is attached....maybe?

[Mark McLean]

I am with Carl - thinking that this work will be hard to do through the sound hole and you would have a much better time of it with the back off.  I have reshaped a collapsed top by taking the back off, spritzing the inside of the soundboard with water and then pushing it out with a hot-and-heavy sandbag (heat it up in your oven, place it inside the guitar which is sitting in a radius dish, pile more weight on top, repeat a few times). This was a Frank Ford trick illustrated on Frets.com

[John Yungbluth]

Carl, Mark,

The deed is done.

The Takamine F400 12 string is returned to playing condition. After all the repairs the geometry was returned to a point it did not require a neck reset. Presently back at its home being watched over since mid July with by Ralph. No movement or issues at this point after 4 months.

A quick update to take you through the steps and process I did to return this to playability.

I used magnets inside and out to make a layout on paper of the top as a guide to braces and bridge plate.

I decided to approach the forward half of the lifting bridge plate first. The bass side X-brace was already loose from the top across a 3-4” length behind the bridge plate and still secure its last 1 1/2”. I carefully separated that brace from the top from the back edge of the bridge plate to the X joint.

This allowed me access under that X-brace to probe the bridge plate separation. Turned out it was about 40% open. I had to modify some of my separation tools/probes to work in the limited work space. Best mod, taking an old flexible hacksaw blade, grinding off all the teeth flush, removing the paint, rolling the edges and polishing it. Then cut to a tool length (2) workable inside the guitar. It was a slow process to work across the space between the 2 X-braces. I used a magnet on the top to see where it reached. But I was able to probe the effected area and see what was still attached to the top.

To deliver glue I chose a veterinarian syringe and needles. Tried 16, 18, 20 and 22 gauge needles on simple glue ups on scrap and quickly determined hot hide glue was not an option. It cooled way too fast in the needles. And I was concerned about strength when adhering to the OEM’s glue. Titebond Original was used. Modified a 18 GA needle with a gentle curve to add ease getting into the workspace and better coverage.

I was faced with a clamping space problem going through the sound hole. Not enough room to clamp the caul and down the whole length of the X-brace on one step.

Opted to use 2 steps.

2 clamps to handle the full sized, plastic film covered, bridge plate caul and a portion of the X-brace. I modified the bridge plate caul with an additional wood strip that added downward pressure on the portion of the X-brace along side the caul that needed to be reglued. Injected about 9cc’s of glue until I could get squeeze out from hand pressure along the open edges. Used a .003” feeler gauge to spread glue now completely through the workspace. Cleaned. Added first clamp and cleaned again, second clamp and another clean up.

Then step 2, the remaining X-brace. Used Titebond Original applied with a plastic syringe, used the .003 feeler gauge to get coverage. Wash, rinse and repeat on cleanup. 2 eyebolt jacks with external stabilization to reglue the remainder of the X-brace.

Repaired the crack in the heel, again using Titebond Original.

Cleaned the top and bridge base and remounted it again. Titebond Original.

In the end the neck/body geometry was very good, and there was no need to do a reset. That was fortunate, because no information could be dug up on what type of neck joint I would find in there. That joint remains another unsolved mystery of the Orient.

Thank you for your insights and perspective.

[Mark McLean]

Well done John.  Nice rescue.  The pulling power of 12 strings can certainly get things bent out of shape, and when braces start to fail it was a real challenge.  Good to know you have it back in good order.