MIMF

I'm working on a 1971 Gurian S2M steel string acoustic. The guitar has been in storage and has dried out. The top center line joint has come undone between the bridge and tail. When it came to me, the seam was open about .020" with some fibers still attached across the gap. I humidified the guitar at 60% for three days and the joint closed up nicely.

Now what? There is no centerline reinforcement on the underside, so I'm planning on adding this. Small, light, cross grain. I'd like to reglue the seam, but not sure I can force much glue into the now closed up seam. Any thoughts on this? What kind of glue would you use? Thin CA would certainly seep into the joint, but I don't think of CA being particularly good for this kind of joint. Maybe thinned down HHG?

Yes, thinned HHG would be best, but Titebond will work too and will give you more working time. The trick to getting glue into the now tight joint is to place your hand inside the guitar and push up on the seam with the thumb pad. This opens the joint slightly on the outside of the guitar. Now apply a bit of glue and rub it over the seam with the fingers of your other hand. Let the pressure go from inside the guitar and you should see a bit of glue squeeze out of the joint. Wipe the glue off the top with a damp rag. Check that the sides of the crack are lined up, and that one side is not higher. A clamp may be necessary if one side is higher and doesn't stay level after you push it into proper alignment. After the glue dries you can attach your cross grain patches. Hope this helps.

Here's a tip.....The little suction cups that holds "do-dads" onto your window/sliding glass door/shower makes great pumps to pump HHG or Titebond into a crack!

Thanks guys, very helpful.

Really wash your hands before pressing glue into the seam or you will get a dark line as a result. HHG for sure. Magnets combined with thin plexiglass cauls will help level the seam. Put the outside magnet in place with the plexiglass caul before allowing the inside magnet near it's appointed place. Otherwise you risk causing dents in the top. Remove magnets and clean up the remaining glue after a few hours, and put the magnets back in place while the glue fully dries.