Ladder-braced parlor guitar

[TonyinNYC]

This delamination issue has me intrigued. A guy I know from another forum worked for Franklin and is an expert on adhesives. He knows more about glue than anyone I know. But, then again, I only know one glue expert. Fortunately, the one glue expert I know is an actual, bonefied expert with years of experiance in the field of adhesives. Anyway, I have sent him a message asking for his opinion. Since he worked for the Titebond people, I believe in their specialty adhesives department, but I may be wrong, he may have some insight on this issue. In the event he drops by while I am not around, his name is Hugh. I sent him a link to this thread.

[TonyinNYC]

I received a reply from Hugh. He is going to join the forum soon and post a reply. He sent me a lengthy reply that I would post if I were not on my phone.

[Lonnie B]

Thanks for that Tonyin NYC will be waiting as I'm intrigued by the delam

[Dave Bagwill]

I've decided to re-purpose a guitar I build way back, into a ladder braced parlor. The bones are good, the wood is excellent, but it was way way overbuilt and deserved renewal.
It's a 00 eir, I took the top off and shaved the back braces down to about 1/2 of what they were, cleaned up the insides, removed all the binding, and have braced a new top made out of some amazing redwood. I've never heard anything quite like it when it comes to tone and sustain when tapped. I hope it works out.
I'll also be completely refinishing the instrument.

[Hugh Evans]

Hi everyone, Tony brought this discussion to my attention. As a quick self-introduction: I have previously worked as a Technical Specialist for the makers of Titebond, and have consulted for every large scale guitar company in the US over the years. My educational background consists of a double major in Biochemistry and Mechanical Engineering. I have been building and repairing guitars for about 15 years, although I have been working with wood since age 5.

Here are my thoughts from what I have seen in this thread thus far:

Using a roller is perfectly acceptable for this application. However, assembly needs to be accomplished as fast as possible even if a product such as TB Extend is used. In large scale production those sides would be glued up and under full clamping pressure in under 5 minutes. The caul system pictured in the thread looks like it should be able to do the job, but since the bond line is stressed I would strongly recommend leaving in clamped for 24 to 48 hours. Surface prep consisting of wiping the bonding surfaces with acetone prior to gluing never hurts, especially if any of the wood is an oily species. As for the areas that are delaminating: Try going over them with an iron set to medium-high heat, it can take several seconds to heat the adhesive above its melting temperature but it will rapidly cool down and create a proper bond very quickly. For additional information on this process look up iron-on veneering (if a good guide cannot be found I believe I have a copy of a document I wrote for Franklin.)

It's possible that voids exist elsewhere in the sides. Lightly tapping with a fingernail or an eraser at the end of a pencil can make finding such voids simple as they will have a distinctly different sound from the areas where good adhesion was achieved.

For future reference, vacuum bags are a fantastic technology for back and side laminations due to their exceptionally even pressure and large distributed force (14.7 PSI adds up quick!) Also, since these are parts that will likely never need to be separated TB II Extend generally has better affinity for oily woods and can be a bit less finicky than TB Original or Extend. Clamp times of 24 to 48 hours are still advisable. It's also not a bad idea to throw a dry block of wood into the vacuum bag as it will facilitate moisture migration from the adhesive.

With respect to TB Cold Press for Veneer, I would NOT recommend it for use in guitar construction. It is little more than a heavily filled white glue that was formulated to prevent bleed-through and has poor thermal resistance (which is directly related to creep performance.) It's great if you need to put unbacked veneer onto a piece of furniture, but is absolutely unsuitable for use in musical instruments. The filler used also makes the adhesive highly prone to spoiling, and under the right conditions it can go bad within 3 to 6 months... and I mean bad. It can, and will, grow a thick layer of mold at the top of the bottle while taking on an odor that makes rotten milk seem pleasant.

[Lonnie B]

Hugh,welcome to the forum. I've been looking forward to your explanation. Looking forward to more of your input.

[Dave Bagwill]

Thanks Hugh for the timely information and welcome to the forum!

The question has come up as to whether I used enough TB (original), or whether I had left enough 'wetness' for the process to work. And, as a matter of fact, I did roll the stuff on in, I think, a sufficient amount, BUT did not leave it 'wet'. It was rolled well into the wood and was tacky at best. As well, the process of gluing and placing both sides into the vacuum bag took probably 8-10 minutes.

Can you comment on the wetness issue and the amount issue as well?

Your tips on bagging and on the use of an iron to refresh the glue in the laminates - priceless. Thanks.