Interesting Bit Regarding Action on Acoustics

I came across this 90 year old pamphlet from Gibson.

http://www.frets.com/FretsPages/Museum/Documents/Gibson/Action1914/action1914.html

The first paragraph is really interesting with regards to new instruments. Is that true of all acoustics, even modern builds? The way I interpret it is that they are saying as the bridge settles in the first 90 days, the action will lower. Why does this happen exactly?

I've never purchased a new acoustic, so pardon if this is a stupid question.

jm, I didn't read the article, but I would think that any geometry changes on a new instrument are potentially due to changes in environment (humidity, mostly). All the big-box makers kiln-dry their wood to varying degrees before letting them re-acclimate prior to building, and that really should prevent changes. Certainly the goal is to make a guitar which is perfectly playable from the git-go and doesn't change. Most folks feel that tone changes over time due to some natural aging of the wood, but I don't think that's what you're talking about.

In 1914, Gibson described it this way: ‘The tilted neck and high bridge on all new model “Gibson” instruments give an increased string pressure at bridge of several pounds which causes a settling of the bridge and sounding board of approximately 1/32 to 1/16 of an inch in the course of 60 to 90 days.’

The 'settling' they refer to could result from a combination of wood cellular structure relaxing and glue(s) potentially stretching or shifting. We have come a long way since 1914, and (most) acoustic guitars constructed today are built to much tighter tolerances to begin with. They do not 'settle' significantly; indeed, a 1/16" drop in the soundboard over 60 to 90 days in a guitar built today would likely be cause for alarm, and there could be concern for structural failure. Curiously, necks have the tendency to tilt forward, shifting at the neck block, if they tilt at all. This results in a higher action (and is a leading cause of the need for a neck reset in later life). The lower bout can rise upward behind the bridge (an effect known as 'bellying'), also raising the action. Occasionally, bracing will fail and a bridge will rotate forward and plough downward, causing a lowering of the action. This is not considered 'settling' but, rather, catastrophic failure.

Most builders I know, myself included, send a guitar out with medium gauge strings, regardless of what gauge the player(s) will eventually use. The thinking behind this is the greater string tension A.) Lets the guitar ring to potential from day one; it sounds better. and B.) It may assist in persuading any structural relaxing that might occur to go ahead and occur. But I know of no one that is taking guitars back in to address 1/6" drops in the action height over a 60 to 90 day period.

Christopher Cozad said:

In 1914, Gibson described it this way: ‘The tilted neck and high bridge on all new model “Gibson” instruments give an increased string pressure at bridge of several pounds which causes a settling of the bridge and sounding board of approximately 1/32 to 1/16 of an inch in the course of 60 to 90 days.’

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As a luthier and builder, does that seem counter-intuitive to you? I'm visualizing the forces and geometry, and it does not make sense to me.

jmascis said:

I came across this 90 year old pamphlet from Gibson.

http://www.frets.com/FretsPages/Museum/Documents/Gibson/Action1914/action1914.html

The first paragraph is really interesting with regards to new instruments. Is that true of all acoustics, even modern builds?

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I notice there's a comment in there when they talk about putting a veneer on the bottom of the bridge:
"This does not change the contour to fit the arching", so I got a suspicion it's valid for Gibson archtops built in 1927 but if it were valid for flattops it'd be a much more widely discussed phenomenon.
If it was true of Guilds built between '96 and '04 I'd think I would have seen something from Guild about it when I bought my guitars.
All they mentioned were that the action could be adjusted.
I'm thinking bracing and top radius are quite different on a 1927 Gibson archtop than any modern flattop, and that's what I think the sinking of the top in the first 90 days would result from.
Another consideration is what kind of bridge was being used, was it pinned or was it a tailpiece?
Archtops use a tailpiece which I could see exerting a downward pressure through the bridge that might cause it to "settle in", but a pinned bridge such as most flattops get would tend to pull forward and actually raise the action.
!925 Gibson L5:

jmascis said:

I've never purchased a new acoustic, so pardon if this is a stupid question.

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No worries. Even if we gave you a little guff over in your M20 finish blem thread, we're still here to help, and now hearing it's actually your first acoustic, a whole lot more sympathetic.
In fact, the question made me think "What's going with that?" until I realized it had to be about an archtop.
IN fact, ya got my curiosity up and I had to go find out just when Gibson even started making flattops, and found this info:
(from here:http://www.gibson.com/News-Lifestyle/Features/en-us/the-gibson-acoustic-story.aspx )

"Company founder Orville Gibson invented the archtop guitar in Kalamazoo, Mich., in the 1890s and produced these and archtop mandolins in his small one-man workshop from then until 1902"
I never knew that!
But this is even more telling and I think confirms my guess that that brochure is addressing archtops:
"More significant to any history of the Gibson acoustic guitar is Loar’s development of the L-5 guitar of 1922, originally conceived as the largest member of the new mandolin line, but soon put forward in its own right as Gibson’s flagship instrument."

They did have a flattop to market by 1926 but didn't seem to take' em seriously for 2 years:
"Just two years later Gibson accepted that a quality flat-top was a viable product, and signed up Nick Lucas, the first recorded guitar star, as a signature artist".
That's my story and I'm stickin' to it.
I also notice that later versions of the archtops seem to feature an adjustable bridge which makes me wonder if they introduced that to deal with the issue of top radius fluctuation due to humidity, or maybe to simply allow a player to vary the action according to a given playing style?
At this point I'm not even sure those bridges are original, though.

It sure seems to make more sense regarding an archtop - thanks for the research, Al!

walrus

Here's a shot that gives a great idea of the forces at work on a tail-piece archtop, but I got a suspicion that bridge isn't original:

adorshki said:

Archtops use a tailpiece which I could see exerting a downward pressure through the bridge that might cause it to "settle in", but a pinned bridge such as most flattops get would tend to pull forward and actually raise the action.

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That's exactly what I was thinking...it would raise. So they must be talking about the Archtop.
Do modern archtops do this still?

jmascis said:

That's exactly what I was thinking...it would raise. So they must be talking about the Archtop.
Do modern archtops do this still?

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Outside my usual area of interest but I suspect what Christopher said applies here too: modern techniques, designs, and tolerances probably tend to minimize it.
Also, a lot of 'em have laminated tops now which also resist compression.
Guild themselves started off making electric archtops and continued right through close of Corona, and I don't recall ever hearing of it in that forum.

Guild started off by hiring most of the ex-Epiphone factory workers when the Epiphone factory was moved out of New Jersey to Kalamazoo in the Gibson buy out of Epiphone. Al Dronge saw a large workforce skilled at guitar building, and started up Guild with that workforce. Guild orignally started with archtops, because that is what the former Epiphone workforce was most experienced at making.

I do not build archtops. Among the few I know who do, none of them can confirm such a 'settling' measurement. I intend to keep asking. The topic certainly makes for an interesting conversation.

With only a little exaggeration on my part, I would summarize the article as quoting a Gibson policy that was deliberately over-setting the neck and starting out with a taller-than-you-may-wish bridge, in order to compensate for the fully expected controlled collapse/implosion of the box which, in turn, would result in just-the-right-action for the player once everything 'settled' (now *that* is an artform!). A warning was included to live with the high action for a few months for, should you be panic-stricken and modify the bridge prior to the magic happening, you would suffer the consequences of string buzz.

well, from an engineering perspective, even if the main force wants to pull the bridge toward the neck or tilt it, there is a large force component pushing down when it does that also i would think.

gjmalcyon said:

As a luthier and builder, does that seem counter-intuitive to you? I'm visualizing the forces and geometry, and it does not make sense to me.

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Well, if I am reading this right, they are saying that they were over-setting the neck (which, under "normal" circumstances, would lower the action) but increasing the break angle of the strings by adding a taller bridge/saddle. The combined angles (back set neck and tall bridge/saddle) would certainly result in more downward pressure on the soundboard. Evidently, as the soundboard compressed (or collapsed), the action lowered. An interesting approach, to say the least.

That extra pressure would definitely drive the top. There is always a balance to be sought after when thinking in terms of sufficient energy to set the top in motion, and over-driving it. I wonder how those guitars sounded?

kostask said:

Guild started off by hiring most of the ex-Epiphone factory workers when the Epiphone factory was moved out of New Jersey to Kalamazoo in the Gibson buy out of Epiphone. Al Dronge saw a large workforce skilled at guitar building, and started up Guild with that workforce. Guild orignally started with archtops, because that is what the former Epiphone workforce was most experienced at making.

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Well, actually, Al Dronge was a a bit of a jazz player himself, too.
So I think building jazz archtops was always the primary raison detre and the availability of all those skilled builders came at just the right time.
Epiphone suffered a strike in '51 and moved production to Philadelphia from New York, which left former Epiphone exec George Mann and a bunch of skilled workers looking for a new employer.
Dronge became Mann's partner in '52 but bought him out pretty quickly
This preceded Gibson's purchase of Epiphone and the move to Kalamazoo by 5 years.

swiveltung said:

well, from an engineering perspective, even if the main force wants to pull the bridge toward the neck or tilt it,

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that only applies to pinned bridges on flattops.

swiveltung said:

there is a large force component pushing down when it does that also i would think.

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In a pinned bridge all the force pulls forward, there's no torque fulcrum point to exert downward force.
Or rather, the bridge itself is the fulcrum point and the string torque is tending to rotate it forward from the saddle's 90 degree angle to the top.
The dip or bellying seen on those tops is still a by-product of the bridge's rear edge being pulled towards the soundhole, driving the forward edge into the top..
And that still tends to raise the action, not lower it, which is what Gibson was warning against.
With a tailpiece on the other hand, ALL the torque is applied downward in a 90 degree angle through the bridge and there's no fulcrum point exerting forward (or backward pull) on the bridge. The fulcrum point is at the edge of the top at the tail of the guitar.
So the tail edge is being pulled forward, not the bridge itself.

adorshki said:

that only applies to pinned bridges.

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Let me ask this, which is a bit OT, but I have a Gretsch Duo Jet (electric) that originally had a floating bridge, but Gretsch pinned it for me. Does pinning it increase the forces at all and thus the odds of the neck warping, ski jump neck, or any issues like that?

Christopher Cozad said:

In 1914, Gibson described it this way: ‘The tilted neck and high bridge on all new model “Gibson” instruments give an increased string pressure at bridge of several pounds which causes a settling of the bridge and sounding board of approximately 1/32 to 1/16 of an inch in the course of 60 to 90 days.’

Click to expand...

And in 1914 they hadn't built any flattops yet, so they had to be talking about archtops.

jmascis said:

Let me ask this, which is a bit OT, but I have a Gretsch Duo Jet (electric) that originally had a floating bridge, but Gretsch pinned it for me. Does pinning it increase the forces at all and thus the odds of the neck warping, ski jump neck, or any issues like that?

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A pinned bridge in acoustics refers to a bridge that of retains the strings in the bridge with bridge pins.
Pinning the bridge in an archtop with a floating bridge is a method keeping the bridge located so you don't have to intonate the guitar every time you change strings or accidentally knock the bridge out of place.
I doubt it has any negative effect on long-term durability.

Keep in mind, the pamphlet says "Gibson instruments." Mandolins are listed first. At this time, they were still "The Gibson Mandolin Co." Guitars are listed second in this dissertation. Mandolins were hugely popular at this point in time. This was 7 years before Lloyd Loar joined the Gibson Co. as chief engineer and created the holy grail of mandolins.

dreadnut said:

Keep in mind, the pamphlet says "Gibson instruments." Mandolins are listed first. At this time, they were still "The Gibson Mandolin Co." Guitars are listed second in this dissertation. Mandolins were hugely popular at this point in time. This was 7 years before Lloyd Loar joined the Gibson Co. as chief engineer and created the holy grail of mandolins.

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And I just realized that the pamphlet in the OP was described as "90 years old" so I thought it was from 1927, and completely walked by the notation on the frets.com page that it was packed with a 1914 mandolin, and thought Christopher was citing a different document!

But it's yet more proof that it couldn't possibly be referring to a flat-top guitar.