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The beginning of the current conversation on glue choice got me thinking. I know glue joints have to be mostly perfect, and especially so for hide glue, but I doubt my linings are good joints. They're little straight facets mated to a curved piece. I doubt I clamp them tight enough to crush down all the corners and round over the facets.

Should I be wrapping my linings around a form and giving them a once over with sand paper to smooth out those curves? Does anyone do that? I guess a lot of my instruments had heat bent solid linings, but it was not my intent to do that all the time.

Thanks,
Mike

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Mike Lindstrom

No!! Seriously, it really isn't a big deal. The Classical lot glue individual straight faceted blocks, just held for a few seconds with the finger. No clamps. They hold perfectly fine.

Why isn't it a problem? Does the side deform easily enough to get a good joint? I don't generally end up with bumpy sides around the edges.

Mike

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Mike Lindstrom

No the sides don't deform, nor do the straight facets of the linings/blocks. I suppose that technically you get a glue line in the centre of the facet. It's usually small enough not to be problematic, there's enough wood to wood contact towards the edges. I can't ever remember having a problem with continuous linings coming loose. I've seen a few blocks come off but mainly when the side has taken a very heavy knock, heavy enough to puncture or severely crack the sides. If you really want a stronger bond with Hide the easiest way is to size the gluing surfaces first.

why ?
Some glues are better at filling than others. If you do the math , your gap is actually pretty small and insignificant in relationship to glue surface area. A glue joint will have a layer of glue and the few thousandths of an inch is not enough to cause an issue as you have a pretty large glue area . Also this is not as stressed a joint as lets say a bridge so you are pretty safe.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I would agree with the others on this. Speaking strictly on the joint itself there are not a lot of stresses on it since it is on the corners where you have multiple grain directions and it is the stiffest part of the guitar body. You have to remember that you are gluing the top to it which gives it more strength and then adding the binding and perfling which stiffen the joint up even more. Plus the act of routing the perfling channels you are making a solid joint along most of the lining on the side anyway so the amount of square to round joint you are talking about is being removed.

I am not sure if you have ever tried removing the top or back of a guitar but I have done a number of them and I can tell you it does not come apart very easily. I usually disassemble them using heat and a separation knife and I don't think I have ever had the linings come off other than a few broken ones but they usually split in half rather than pop off because of a weak glue line.

As long as you clamp them in so you get good wood to wood contact you should be just fine.

Cheers,
Bob

I did actually contemplate switching to Titebond 3 for the lining-to-side joint after reading that glue thread


I had kerfed linings come loose in a few spots when removing the back on one of mine. All hide glue, and I used a lot of water during the back removal. But the nice thing about hide glue is that you don't have to peel them all out and clean them off before regluing.

I guess the question is, if you leave a guitar in extremely high humidity for days, will the glue behind the linings soak up enough water to come loose before anything worse happens?


I've actually found that it's quicker to round over the backs of them for a better joint, because I can make each block wider and thus don't have to make or glue so many of them. Though I do still use narrower flat-backed ones in the waist area.

I use thickened epoxy for my linings. It's gap filling, and it squeezes into the kerfs to make a really solid rim, like solid wood linings. This is with reverse kerfed linings.

You can get by with poor fitting linings and still be okay; however, this shouldn't be your ultimate goal. Some possible tips are to bend the linings in a side bending jig before you glue them. You can also add additional "kerfs" in the linings when you go around tight sections. Backs with a tight radius may require you to cut the lining around the waist region, especially if the lining is fairly rigid in the "up/down" plane.

I like using the Ryan A4 kerfing because good solid connection is easy. Before that I used reversed kerfing. Your goal should be a perfect fit and glue joint; fortunately, this is one situation where good fit isn't as detrimental as other operations. I always find it very important to make sure you forcefully push the lining against the rim and hold it there before adding clamps -- it is easy to develop gaps if you just rely on the small kerfing clamps.

You will be fine if you do short sections and use HHG. Hide glue has much better gap filling characteristics than aliphatics or PVAs, it is the easiest glue to use. If your fitments are a bit loose hide glue is for you. I learned to use it at about 5 years old and still use it today when reversibility is a need. Tim

+1 for the Kevin Ryan's A4 Kerfing. I switched to it a few years back and have been very happy. It is so easy to install and looks great inside the finished instrument. Well worth the cost.

http://www.advancedshelltech.com/Products/A4%20Kerfing/aboutA4Kerfing.html

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Josh House

Canadian Luthier Supply
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Hmmm. That's the opposite of what I've been told in the past.

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Mike Lindstrom

+2 for the Ryan A4 kerfed lining!

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

I'm going with Ryan's linings on my next build project. Cool stuff

Bit of a sweeping statement - just try that on bracing, a bridge or dovetailed neck.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

in my experience Hot hide glue is very poor at filling gaps. Tite bond is better . This is one thing about HHG and fish glue. You need a clean tite joint for them.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I think it was that magazine glue test that stated hide was better at gap filling than PVA glues. Perhaps I'm remembering it wrong but I certainly heard it somewhere recently, which does go against a lot of previous thoughts.
The point is that Hide is certainly good enough for the type of 'gap' (thick glue line?) that we are referring to here. If anyone has had to remove linings glued with Hide from a rib structure you'll realise just how difficult it is. It's easier to knife the linings off in big chips until you are left with just a thin veneer, then wet and heat through what is left.

Hello all, first off to quote the late great Lou Reed, "believe half of what you see and none of what you hear". I don't read woodworking magazines anymore, all too often inaccurate and biased toward their advertisers. You certainly don't have to take my word for it, do what I have done extensively for the past 10 years, do your own tests. To test the gap filling characteristics of glues prepare flat sides on 2 small scraps. Take some waxed paper or parchment and layer up some "shims", say 6 to 8 thousands of an inch, thats a pretty big gap. Apply the glues of choice in the center of the scrap and the shims on the ends, clamp at the ends, leaving the gap in the center where the glue is. This is an area where hide glue shines.

Happy building, Tim

timoM,

I think you may be correct in saying that hide glue can be used as a gap filler but unfortunately it isn't a very strong one.

I have done my own tests and glued non mating surfaces together with hide glue and PVA to find out how they hold. I used some old brace material glued to a piece of a 2X4 that was not sanded or planed but it was cleaned. The mating parts did not fit together perfectly and neither sample was clamped, just glued and stuck together.

My results were that both held together under the pressure of me just pulling on them with my fingers but under shock, using my fret hammer to hit the pieces sideways the HHG joints failed much much quicker than the PVA. With a relative light to medium blow the HHG joint shatters where the PVA joint needed a much heavier blow and when it did let loose it broke the brace material rather than the glue line.

I repeated the test with the same materials but I sanded both surfaces and clamped the joints. In that test the HHG joint was as strong as the PVA but the HHG still broke at the glue line and the PVA still tore wood out.

So my test indicated to me that HHG was not very good at gluing parts that didn't mate very well where PVA was much stronger. I figured it was because the HHG is like glass when it sets up and PVA is more flexible.

I also deduced from my test that HHG is a much more reparable glue joint than PVA since it will shear at the joint line and not tear wood out. Also, HHG glue will stick to itself so you can just heat the joint up, apply a small amount of new HHG and re-glue the parts without having to remove all the old glue. PVA glues are not great at sticking to itself so joints must be cleaned and all glue removed so you are gluing wood to wood.

I did this little test quite a while ago and this is one of the factors of how I determine what glues to use for a specific job. If I don't care about repairability and don't want to take the time to mate surfaces up then PVA is my choice. If I want a joint that can be repaired if it is broken or needs to come apart easily then I use HHG.

Of course, we all do things differently and I am sure someone will disagree with my "informal" test but that is what I learned and how I decided what glue to use for a specific job.

Cheers,
Bob

Bob, I think you learned from your test what you needed and wanted to know. I'm iconoclastic by nature and running the shop I run makes me question many aspects of woodworking and metalworking quite regularly. When someone pays $10,000 for a door or $35,000 for an armoire I don't want anything coming back later, I haven't had a failed glue joint in many years. Our repeat business and referrals have us busy so far in the future I don't really know what our lead time is. I've only been building guitars for just over 4 years and I'm 18 months out on that. All of this is because of design ability, communication skills, and quality and originality of the final product. I've done glue testing to insure the quality and longevity, I simply won't risk this on anyone's opinion, that would be foolhardy. I sincerely doubt I will have a glue failure for decades because of the testing I've done.

Tim

Found it:

http://www.oldbrownglue.com/images/arti ... ue_FWW.pdf

This shows (I believe) that Hide is better than PVA with loose joints, yet worse than Type 1 PVA.
Strange but liquid Hide does much better than everything you read on the luthier forums. I've had virtually zero experience with it. I briefly used it on some furniture many, many years ago.
I'm also convinced they may have got different results if they had sized the Hide glue joints first (not with the loose joints though). I base that on doing many experiments with Hide and gluing soundboard cracks when not using cleats.

Luthier requirements and furniture are different . My Father was a Cabinet maker and used HHG then went to White glue. What I learned from him was the attention to detail when making a joint. If the joint is not tight , your joint is a compromise . In luthier as compared to cabinet making , we are building a box to take stress and movement , just the opposite of furniture making.
We don't build furniture to take apart , instruments we do plan for future repairs.

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

The bottom line here is that if you glue joints are expertly prepared -- then hide glue will work beautifully and Titebond 1 type glues will work beautifully as well.

It seems to me that Titebond has a reputation that is a bit more forgiving since you rarely here about problems with this particular glue. Maybe we are wrong about all this and hide glue is more forgiving but my advice is just to use Titebond until the quality of your work is excellent. Then switch over to hide glue and see if you like it more at that point -- if you prefer Titebond (or LMI, etc.) then stick with that.

Just use solid linings! I have made the change and I'm never going back!