Repair Question on 12 String Bridge String Anchor

[Allen]

I was contacted yesterday about repairing the bridge on a 12 string Adamas guitar.

The remanufacture of the string anchor looks to be simple enough, but what I'm wondering is how that sucker is anchored to the bridge. It looks to be made from Carbon Fibre (I've only seen pictures) and then perhaps glued into a slot. Much like a saddle would be slipped in I suppose.

Being that there is going to some considerable pull on this part, they must have used some very good glue, or perhaps there is more to it than what I can surmise from the pictures.

The owner said that they had to send it back to the USA the last time they needed anything done, and it was less than satisfactory workmanship. So would like to have it done as local as possible. Has anyone had experience with this type of set up before? Any advice is greatly appreciated.

[Taffy Evans]

I wonder if there are small bolts embedded in the insert that also holds the bridge to the top?

[Allen]

Good point Taffy.

Don't know what kind of access there is to the insides of this guitar. You aren't going to be doing much from those sound holes in the upper bout.

[jeffhigh]

Looks like they have used unidirectional CF bar. Not much to stop it delaminating along the line of the holes
A piece of aluminium might do better

[Kim]

I don't know but you may find the string mount and saddle are a one piece affair that has been bonded into a rebate in the underside of the bridge?..I would look around on google to confirm this is not the case before doing much more..Or you could contact Steve (Simso) because if anyone on this forum has repaired one of these it would be him. Failing that you could investigate yourself with an easily filled 1/16" drill bit turned by hand drill to take core samples of the real estate between the string retainer and the saddle.

[simso]

There not bonded with the top.

They just push into place, usually find drops of glue on the sides holding them down

[kiwigeo]

WTF would you design a string anchoring system like that??? I bet this isnt the first of these 12 strings that has turned up in a luthiers shop with this issues.

[Allen]

I had thought that either aluminium or brass would be the go for making a new one. Dead easy to make on the mill. No way I'd want to try it in CF. That's just a recipe for disaster.

Or perhaps some bi-directional CF laminated on either side of brass or aluminium. That might give it the same sort of look.

Thanks Steve for the heads up. So a snug fit with some glue should do the trick

[jeffhigh]

Brass would be a bit heavy-kill the tone LOL
I'd go aluminium with a fresh clean surface set in epoxy

[Taffy Evans]

I thought these bowl back guitars [if thats what it is] had a trap door in the back. But you would have seen that.

[Allen]

I've only seen the pictures that I posted Taffy. Got a call and the photo's yesterday asking if I'd be willing to do a repair. Will know better when I get the instrument in my hands.

[simso]

Nope no access panel , on the ones Ive worked with

[Bob Connor]

Whilst working on the Adamas model it is extremely useful if one owns a trained octopus.

Regards

[charangohabsburg]

WTF would you design a string anchoring system like that??? I bet this isnt the first of these 12 strings that has turned up in a luthiers shop with this issues.

+1
Converting that bridge to a different anchoring system would be the best thing. Go with a conventional pin bridge design or...
...screw a 2mm thick stainless steel L-profile on top of that bridge.

[Taffy Evans]

Hmmm, what kind of clamp would one need to get from the soundhole to the bridge posi?
I've made many special clamps in my time for repairs, but that one would be a challenge

[DarwinStrings]

Perhaps a Estwing clamp Taffy.

Jim

[Kim]

Hmmm, what kind of clamp would one need to get from the soundhole to the bridge posi?
I've made many special clamps in my time for repairs, but that one would be a challenge

A vacuum clamp would work ok but I bet the robot at the factory simply fused the bridge to the top prior to fusing the top to the back bowl while the plastic was still hot from the lazer cutting the bubble in half that form two more shells..

[Taffy Evans]

The old vaccum clamp trick, eh. I did not think of that, maybe cos' I haven't got one.

Long, long time ago when Ovation was the go, and I was repairing them all too often, I asked what the glue was that was used and never got an answer. I sent a chip of the glue to a chemist type guy and the report came back "...for use in a caulking gun and not suitable for my guitar work". He thought I was after some for building guitars.

[Allen]

I have the said instrument in hand now.

There is no access at all except through the sound holes in the upper bout, or through a side port that houses the EQ / preamp etc.

Will have a look today at seeing how easy the bit of CF is to get out of that slot.