Official Luthiers Forum!

Alan,
How about using microscope slides? They would all be uniform in size and mass. Are you going to excite them ala Chladni style? How would you measure the slides?

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tim...
http://www.mcknightguitars.com

Chuck, I did consider welding but it would add mass and also change the physical property of the steel and likely aneal it. Since I was using cold rolled steel there is no way to return it to its un-anealed state, is that a word?

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tim...
http://www.mcknightguitars.com

Without re-doing your entire test, Tim, could you find a machine shop to mill a solid billet of the same cold rolled steel(I mean the same composition) to the shape of the lap jointed glue pieces?

Or not I think the test stands well, just the interpretation of the results. Even without the solid "standard", the results hold up and show how some glues isolate and de-couple the two halves.

You could TIG tack it through the two layers.

Not that I'm saying you should...just that it's an option.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

TIG won't sound like the pre-war welds, you have to use Oxy-Acetylene.

...now back to your discussion about hide glue

Respect!

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

I wanted to throw my two cents in here. Maybe it clarifies a few things. Maybe not

The chemical "sizing" of fiberglass and carbon fibers accomplishes several things. The primary function of sizing is to provide lubricity to keep fibers from abrading and tangling themselves. Secondarily, it cleans the fiber and coats it to better prepare it to receive a specific liquid matrix material. Different matrix materials (epoxy, vinyl ester, polyester...ect.) require different types of sizings. The secondary function of epoxy sizing is as a surfactant. Sizing serves as a "primer" too, because glass is one of the most inert substances there is, but it is mainly to deal with high surface tension. Mixed epoxy has a very high surface tension and the right sizing helps it spread out better.

Epoxy catalysts are usually amine based.....and highly alkaline which means they are corrosive. Prior to cross linking, and depending on the substrate, these amines break down the surface, creating free radicals for the epoxy to crosslink to. That's about as detailed an explanation as I'm able to give. I offer it to differentiate some glues from others. This characteristic won't be nearly as acute with aliphatic or urethane glues. Not sure about cyanoacrylates. Epoxy is particularly corrosive and is very effective on some substrates because of this characteristic.

Lastly, a chemtreat process or a boric, phosphoric, or chromic acid annodization can be used to prepare aluminum for bonding. Oxygen is corrosive to aluminum. Some alloys are worse than others but on the whole, a freshly cut aluminum surface will develop an oxide layer within an hour of exposure to oxygen. Once an oxide layer forms the process ceases. The problem with gluing untreated aluminum is that the glue bond occurs only to the oxide layer which has a peel strength of roughly 1000 lbs per sq. in. Prepping aluminum with one of the above processes greatly reduces the speed at which an oxide layer forms. Generally, the part is etched which removes the existing oxide layer. Then the surface molecules are rearranged with an electrolytic process so they will no longer be affected by oxygen. Now when you try to glue the surface you are bonding to a much purer surface, not an oxide layer, and the peel strength is about 3000 lbs. per sq. in.

Oxidation can still occur slowly over time, however, so a final priming of a freshly annodized part is usually done on aerospace parts prior to painting or bonding. That's the green color some folks may have noticed on raw airplane parts. That's usually a BMS (Boeing mill spec) 1011 primer. This primer allows for the part to be stored for a long period of time prior to bonding or painting.

Ok.....a little pedantic maybe. I did this for 15 years.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

Thanks, Stuart! I, for one, always appreciate the seriously technical posts (because I learn lots of useful stuff!)

Hesh is making some awesome posts on marketing in another thread, as well.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Thanks.

There is a slight error in my post. Annodization on aluminum actually creates a new, sort of synthetic oxide layer to bond to. It's a MUCH more uniform layer. My post sort of suggested the oxide layer is gone.....but it's really just ..... better.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

having read the test report, and the discussion here, does anyone else feel like they have learned nothing, or are atleast back where we started?

oh well, it was an entertaining half hour

thanks

Jonny

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"Anything that happens, happens. Anything that in happening causes something else to happen, causes something else to happen. Anything that in happening happens again, happens again. Though not necessarily in that order." Douglas Adams

Absolutely.
And mostly "cold creep". Although I doubt that TB1 cold creeps noticeably, or at all, with the small stresses present in guitars (compared to industrial use). On a personal level, the guitars I've built using TB1 have been stable and rock solid so far.
So maybe we can call that "hot creep". That seems to me the biggest advantage, that a bit of heat will not soften HHG joints like it does TB1.

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

Todd, I agree. We typically use lots of different adhesives within one guitar. My rationale for delving into this whole glue mess was to see if there was any real foundation to the folklore surrounding the hallowed use of HHG. The results still have me scratching my head...

Good suggestion Mario. I will look into it. best idea yet.

Thanks for chiming in guys.

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tim...
http://www.mcknightguitars.com