Repairing grain tears after bridge removal

[Greg Maxwell]

I am doing some work on a 1975 Gibson Hummingbird that has had some rather poor repairs in the distant past. The current owner has had the guitar since the early 80's and all the work was done prior to this. The guitar needs a neck reset, bridge plate repair, and a new bridge. The current bridge is not original and was glued on in the wrong location, negatively affecting intonation and leaving a shadow of the original showing. It is also cracked all the way along its length.

 

I have removed the bridge using heat, spatulas, and tapping lightly. I worked as carefully as possible but the grain is rather damaged underneath. I removed three usable slivers from the underside of the bridge and reglued them back on. I suspect that most of the damage is due to poor removal of the original.

 

Two questions: What is the best way to fill/repair the grain damage short of inlaying a new thin piece of spruce over the entire area; and what is better in terms of gap filling ability for the gluing of the new replacement bridge, Tightbond or hot hide?

 

Thanks for any help.

 

[Steve Beckwith]

Greg,
I just finished a similar repair on a D35. It to had "previous work". I leveled the under the bridge via sanding and then raised the resulting cavity to the level of the rest of the top by adding an extremely thin layer of spruce (as you mentioned in your posting). Of course you can;'t just lay-in the spruce and hope that it's the correct height. When I do this, I bring the spruce up higher than the top of the rest of the guitar and then carefully level it by sanding back.

- Steve

[Greg Maxwell]

Thanks Steve. Where do you draw the line at when a cavity needs sanded and filled, vs just cleaned before gluing the new bridge? My customer does not want to put more money into this and I already gave him a great price on the neck set and bridge reglue.

[Ned Knepp]

Perhaps you should consider what it may mean to your reputation if the bridge comes off in a year or two.

That mess under the bridge looks like a lot of pulled fibers to me and my concern would be that I was gluing the bridge to glue reinforced with wood fibers rather than solid wood.

You might consider talking to the client about the unforeseen issues. A humming bird should be worth the expense of fixing it correctly.

Ned

[Steve Beckwith]

In some cases, such as this Hummingbird, filling the cavity is an easy decision. When I've pulled bridges, they either need to have the cavity filled or they don't. There's seldom any in-between, scenarios for a full fill. Sometimes you may need to glue down a few pieces of wood spruce to fill in some gouges.

Per Ned's response, it's a good idea to let the customer know ,if the work isn't done properly, then the bridge will not hold. Most likely it will pull-up right after you put it under string tension. It took me around two hours to do this work. Most of it was spent tapering the edges of the fill spruce for a good fit and then sanding it back after it was glued (I used tite-bond). Let the patch set for a day after gluing before gluing the bridge.

[Greg Maxwell]

Thanks for the help. I am very much within the learning curve for handling all the issues that can arise when doing 'basic' repairs. I am not trying to get away with anything less than the correct way to approach this, I just am not that familiar with a damaged top from a previous repair. I will go ahead and fill this, if for nothing other than the experience and knowing the repair will hold.

[Jim Bancroft]

Larger missing pieces, I'd glue in spruce pieces to fill the gaps, using hot hide glue, Tite-bond, or superglue. The smaller voids I'd use wood dust and superglue. Scrape, sand, and level the area. Before gluing the bridge down, I clamp bridge down without glue and work a thin feeler(.004" or so) gauge around the perimeter trying to work it under the bridge. I don't want any gaps once I'm ready to glue.
From your picture it doesn't look like you have any really large pieces missing and probably all you need to do is fill with wood dust and superglue.

I normally use hot hide glue for gluing down the bridge, or Tite-bond is OK too.

I've used this method many times, and never had a failure yet.

Jim

[nathan clark]

Doing some patching with spruce is your best bet. A good wood to wood glue joint with hide glue is the tried and true way to reglue a bridge. Tite-bond has better gap-filling abilities than hide glue, but it's marginal when compared to other modern adhesives.

There was a discussion about bridge reglue top preparation on this forum a while back that's worth checking out.

[Greg Maxwell]

Thanks for the link. I did a search for this topic when starting this thread but didn't find that one.