??? Glues and high pressure laminate

[simso]

This is a question I’m putting out there, I know quite a few builders on this forum use carbon fibre braces and so forth and I have seen Trev comment on a fe ideas.

Got a Martin guitar in at the momment with high pressure laminate top, the top is 1.2mm thick and it has no bridgeplate no tone bars or anything inside, it does have a super thin layer of fabric glued between the x brace aft , this is quite large .

No surprise the bridge has come loose a few times and the top deformed.

My only thought process for repair is to fabricate a maple bridgeplate and fit it inside, now the million dollar question, what glue, typically I repair any HPL guitar with epoxy, wondering if something stronger exists

I do Martins warranty repair work, thisis not warranty, Martin have since changed this design and the new design has a bridge plate and a tone bar

Steve

[blackalex1952]

Do the Martin mod?
Ask them what glue they used?

[kiwigeo]

In the oil patch we dress threads with this stuff to stop shoes backing off from our casing strings. https://www.drillingsupplystore.com/thr ... pound.html

Might not be practical on a guitar though

[simso]

Do the Martin mod?
Ask them what glue they used?

Have with no luck, the issue is the hpl is lined with some type of fabric which I cannot get off, the newer ones don’t have the fabric and the wood is epoxied directly to the high pressure laminate, so I need a glue for wood to impregnated fabric, I’m thinking epoxy.....but

Steve

[simso]

In the oil patch we dress threads with this stuff to stop shoes backing off from our casing strings. https://www.drillingsupplystore.com/thr ... pound.html

Might not be practical on a guitar though

Might not be

[kiwigeo]

In the oil patch we dress threads with this stuff to stop shoes backing off from our casing strings. https://www.drillingsupplystore.com/thr ... pound.html

Might not be practical on a guitar though

Might not be

Anything that is Roughneck proof is generally pretty tough

[Steve.Toscano]

So you are wanting to glue a bridge plate ontop of the fabric?
What's your reasons for not wantng to use epoxy?

My first guess would be one of the thicker epoxy's that also gap fill eg techniglue.
As opposed to west systems which when applying enough to take into account the fabric soaking it up would run all over the place and make a mess.

Otherwise if wanting to be safe for easy future repairs maybe hot hide or fish glue. I've used both for sticking fabric to wood, so should be fine for wood to fabric.

[blackalex1952]

A photo of some kind might help perhaps here, Steve. There are some creative thinkers on this forum...
Identify the fabric? Test to see if it sands with sandpaper. Test a small patch to see if epoxy sticks to it. Remember that the function of the bridge plate is primarily to prevent the bridge pins splitting the top, a hard timber that will take ball end strings, and the siffness of the bridge plate acts as a brace and a mass which lowers the top resonance a little. If an ebony bridge is used, it could be replaced with a stained Rosewood one, which would reduce mass to compensate, or a laminated CF bridge aka the Gore/ Gilet method. Epoxy glues which flow into gaps are usually of the thixotropic style, I believe, if the fabric is still porous, thixotropic glues form a kind of meniscus.
From the internet: "Non-sag epoxy systems are said to be thixotropic. Certain applications require the epoxy or urethane compound not to run off the surfaces being coated. An extreme example of a thixotropic compound would be shaving cream. No matter where it is applied, it will not run off the surface."
"https://www.masterbond.com/properties/t ... -adhesives"
"Thixotropic materials are greatly effected by shearing forces. High shear, such as high speed mixing or high pressure dispensing, will usually destroy thixotropic properties.
The degree of thixotrophy is indicated by the thixotropic index, usually shown on technical data sheets for materials developed for this purpose. The higher the index the better the material will cling to a given surface."
Any way, my suspicion is that the guitars in question may or may not have quality loud tone when compared to an all timber top, and that the method used is a commercial mass production technique.
Cheers! Ross

[simso]

Way too much rotation.

The top is 1.23mm thick and the cloth patch takes it up to 1.45mm thick total

[blackalex1952]

Has the cloth patch delaminated?-Ross

[simso]

Its something between a cloth of patch and weaved fabric, at a glance to me it looked like a strip of carbon fibre laid up, super thin.

Nope not coming loose, have tried sanding and scuffing and barely a mark, the few things I have glued with so far have just come straight of with little force

Have put it back on the rack waiting for reply from martin, way too much other work to do

Steve

[kiwigeo]

Its something between a cloth of patch and weaved fabric, at a glance to me it looked like a strip of carbon fibre laid up, super thin.

Carbon Fibre cloth..impregnated with epoxy?

[simso]

That’s what I am thinking, now just got to bond to it

[Mark McLean]

It looks rather like a CF fabric, and so I would be hoping that epoxy would work well with it.

Hey Ross - thanks for that very illuminating outline of the principles of thixotrophy (especially the example of shaving cream - got it straight away). And I am about to rebuild a guitar body made with HPL, so I am very interested in knowing the best glue to use.

This is the reason that I can't go a day without reading ANZLF. So much to learn!

[blackalex1952]

Steve-maybe there are traces of some kind of mold release left which is preventing the bonding to the CF if that's what it is...
Mark, a friend of mine who is a pretty well known and respected luthier uses thixotropic epoxy on his CF tow brace reinforcement. It has a few other good properties as well, I believe, which make it suitable for the purpose.
Cheers! Ross!