MIMF

I have a Celtic Lap Harp in the shop for repair. The sound board has pulled away from the sides and "warped" up in the same area [treble end] on both sides.

The soundboard is three "ply" laminated mahogany. Inner ply is the thickest and runs across the string axis of the board. The outer "plys" are about half the thickness of the core and run along the string axis [with the length of the board].

The separation is NOT at the original glue joint to the sides of the box but between the bottom laminate and the core. The "warp" closes easily and all of the "chips" still attached to the mating surfaces close nicely into thier mating cavities.

Question is what glue do you suggest? I have on hand; Hot Hide, LMI white, Titebond, West epoxy, and polyvinyl [gorrilla].

The original glue joints are tight so there does not appear to be any "old glue" contaminations of the surfaces I need to glue now.

From the squeeze out inside the box it looks like Titebond was used for original construction.

I generally like using hot hide but I have not done a lot of work with laminated wood and I'm a bit concerned that I may not be able to get it worked into the crevasses and clamped before it starts to cool.

I haven't used the gorilla glue before but I am wondering if that might not be the ticket here. I could easily mist distilled water into the separations before gluing and clamping.

The main thing I want to avoid is any further disassembly as, the as mentioned "chips" that have adhered to one surface or the other are still intact, tight, and close well. That includes a couple of places where there are small linear "splints" that are attached at either end to both the outer laminate and the core. These also close and align well. Hence the " don't screw up a good thing" by any further disassembly.

Suggestions and advice/wisdom accepted and appreciated.

Mike J.

I also have thin and medium CA but I'm not sure I could trust the "wick" to get in every where it needs to be.

MJ

A new soundboard might be easiest! A harp glued up with titebond and with a plywood soundboard is unlikely to be of great value or quality...

The entire tension of the strings pulls the join between the soundboard and sides apart, so it needs serious glue. Often screws or nails are used to help hold it down. So to stop it re-de-laminating you might consider screwing a rail down each edge sandwiching the soundboard to the sides.

Thanks Simon, A new top is not within the owners desire or finances. The harp was not a particularly expensive one when it was built 20 years ago by a Seattle builder/company ["Musical Strings"] that is still in business. It appears from their web-site that all of their body construction is with the laminated material.... I will probably give them a call but will do the repair here for the friend/customer as finances are a real concern and here on Lopez Island we do a lot of barter or "karma" transactions.

What is interesting is that the original titebond glue joints have not failed in any way, it was the laminate bond between layers that let go, hence my question about "gorilla" type glue, which I think??? may be the type of glue commonly used to create laminates??

Your idea of a mechanically attached "molding" with a profiled cap to hide the screw heads is a great "light bulb goes on" suggestion. It could made to look intentional and decorative without having any effect on the "free plate" vibration. The sides of the box are about 5/16" thick, so more than enough. THANKS FOR THE IDEA.

Mike J.

Michael, how well do the separated laminations fit back together? Are there any voids?
I would recommend against polyurethane/Gorilla (it's not polyvinyl, by the way, that would be PVA - polyvinylacetate/Titebond) unless the fit is absolutely perfect, and you are able to clamp extremely heavily (polyurethane glue naturally forces joints apart, leaving a poor, weak joint if not clamped correctly).
I would be personally be tempted to use a high quality epoxy.

Thanks Greg, my bad mixing up the "polys". Everything fits back together very well, no noticeable voids. I have west system epoxy in the shop and that may be the way to go, along with Simon's suggestion of "decorative" rails along the edge with mechanical assist.

Mike

If you elect to use epoxy make sure you mix it thoroughly and then some more.

Since the parts all fit well I would probably use hot hide glue and keep a hair dryer at hand to keep things warm and prevent gelling. Thin it a bit and it will wick into the far reaches of the delamination. Pump it a bit before clamping to make sure it gets all the way into the far recesses. Clean up any squeeze out before it dries.

Michael Jennings,
I'd agree with Michael Lewis if everything is fitting as well as you say. If you're confident of the fit, use hot hide glue as he suggests. Good luck however you choose to proceed.

Titebond would probably be strong enough and gives reasonable open time for working it into the separations, but if you are proficient with HHG that might be better. The rails and screws to hold the edges would also be a good addition.
Why do you think it delaminated in the first place?

Sorry guys, been busy at work and not around for the last few days.

The harp is 20+ years old and hasn't been played much. Anyone familiar with the Pacific NW knows we can be damp. Here on Lopez Island there are a majority of folks who heat with wood stoves during the "non-summer" season...so 10 months or so. The owner of this harp lives in a home built cabin and I suspect humidity control is not an aspect of her life.

Her youngest just turned 20 and moved out for his college adventure so she feels she finally has the time to learn and play. I guess that 20 years of sitting, collecting a few cobwebs and those swings from cool and humid to hot and dry took their toll.

I don't know what adhesive was used to create the laminate but the harp joints were done with Titebond.

I glued the first side today.. before I cruised the forum... and used West Epoxy, so we'll see how it goes. I would have been happy with HHG, but even with the heat gun there was just too many little areas and an opening of only a few thousands of an inch to about a max of 3/16 along an 18 inch separation for me to be comfortable getting glue in everywhere I wanted it and getting it clamped in a HHG "timely fashion". The West flowed well into the split and I got the squeeze out i wanted. Cross your fingers.

We have talked about a little better care and storage but given its circumstances it is in really nice shape, once the cobwebs and dust were removed.

The biggest challenge here is going to be tuning the damned thing up.... 24 nylon strings.. diatonic C.... Oh Boy!

Mike

All done... looks good, and holds under tension of 24 strings tuned to pitch.. Time will tell and still have the "alternative plan" in our back pocket.

MJ

Can we see?

Ryan, every time I've tried to figure out how to post photos here... about five minutes in I find my self dreaming of shooting the computer and pouring a large single malt... hummmm not a bad idea regardless. Look me up on FB "Lopez Island" there is at least a before repair photo there.
I freely admit that I am a complete Luddite and an Analog guy hopelessly stuck in a digital world.

MJ