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I've got a Martin DX-1 that is split at the back to side seam and several other places. I recall a discussion about the correct glue for HPL being epoxy but I can't find that. The old joint does have kerfing, it is not bound. I'm wondering if gel CA might be better for the big breaks and medium and thin CA for the various cracks.

I believe that ordinary carpenters wood glue would suffice for the cracks. I used to press large laminate and we only ever used wood glue.
Granted the press was a few ton and heated.
I think CA would work as long as it did not interact with the old glue or the laminate chemically. But I couldn't be sure.
Wood glue is always a safe bet.

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You just pick up a chord, go twang, and you're got music. -Sid Vicious

The X series are made with Formica as back and side material. The only thing I've found that holds these together for any appreciable amount of time after a break is epoxy and CA glue.

CA is a good choice. About the only thing that stands a chance if the HPL is actually torn.

While I will fix a loose top or back at the rims, Any HPL guitar with a "crack' or tear in the HPL is one of those jobs I will not take in. The results are always less than optimum and the job is tougher than working on a wooden instrument. Just so many things you cannot do with HPL.

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

OK, here is the problem. The back to side seam is opened from the neck block to the waist - mostly the glue joint between the kerfing and back has failed. There is some damage to the side next to the heel and a crack in the back itself.



My thought was to first glue the back back to the side with gel CA and binding tape to hold it in place. Once that had cured put some pieces of surgical gauze inside on the side and back crack and soak the gauze in thin CA. I have had fairly good luck reinforcing some curved (wood) surfaces that couldn't be cleated with the tape and CA.

Plan B would be to take it back to the owner and say "sorry....."

I would be inclined to go with your gut. If you feel like it'll be a problem later on down the road I'd pass. If you feel like you can make it work then I'd emphasize the fact that it will not be perfect and if it breals again then it's time for a new guitar.

Those cracks in the HPL, they will run again at some point. Those on the side will likely go first from the torque on the neck block.

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

Thanks for all the good advice. I decided to go ahead and try to fix this. Closed the kerfed seam with gel CA. let that cure and reinforced the inside of the cracked areas with gauze tape and thin CA. The crack on the back had some over lap so it should be stronger than if it was butted. I'm not going to try to scrape or sand the cracked area to be perfectly flat - it would just look worse.

I'm going to include a copy of this thread with the work order so the owner knows that the repair was done as well as it could be but there is a good chance that it might fail in the future.