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Hey all,

Over the last couple of days I've gotten a start on my next guitar. I edge glued the back plates on Tuesday afternoon with LMI instrument glue. Today, I routed about half way through the back with a 1/4" router bit and installed a 1/4" rosewood/basswood backstrip. I put a bead of LMI glue in the bottom of the channel, tapped the backstrip in and then put a little CA glue along where the strip joined the top on both sides. I sanded the backstrip prior to putting it in, it was a snug fit, but I could have pushed it all the way in with a finger. Anyway, when I took the back out of the clamping plate and looked at it, I discovered that the original glue strip had separated in many spots, causing some gaps that are visible on the top. I'll just route out the backstrip and rejoin the back before putting in another backstrip.

Anyway, what's the general opinion on why the glued line on the back plates let go? I've not had this happen before, and i'd like to avoid it in the future.

Thanks for the insight,

Chris.

Anybody? Really hoping for some insight.

Chris.

Your backstrip probably acted as a wedge popping the back seam apart. Also the water based glue probably assisted this in swelling the backstrip.

CA does not act as a solvent for cured AR glue.

What kind of glue did you use on the back center joint, and what is the back wood species?

Thanks Barry,

The back is curly mahogany, the strip is EIR bound with basswood. I put a bead of LMI instrument maker's glue down the center of the channel and CA down the sides after the backstrip was in. I put the CA down because I wanted to scrape the backstrip down quickly. The back plate join was done with LMI glue also, which had dried for a couple of days.

I'll redo the back join and strip and make the routed channel a little wider this time. This one really surprised me.

Chris.

I don't think you need to make the channel wider. It sounds as if you had a perfect fit. If you could push it in with light finger pressure it sounds perfect. What you need to do is have the back in clamps or have some kind of pressure on the edges of the back so that the slight swelling of the woods won't wedge the joint apart. Keep it under pressure until the glue is dry. If you go wider you may have gaps when things shrink back as they dry. It is very common to support a joint when gluing to prevent splits, blow outs or things like you experienced. So make another perfect fit and support the joint while you glue and leave it until dry.

Link

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Cut to size.....Beat to fit.....Paint to match.

That's a good idea, Link.

Thanks,

Chris.