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Warped & Cracked Tops...

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DanSavage
Posted 2017-02-07 12:48 PM (#532616 - in reply to #532612)
Subject: Re: Warped & Cracked Tops...



Joined:
June 2012
Posts: 1578

Location: Lake Forest, CA
DetlefMichel - 2017-02-07 7:34 AM

I would advice all of you who use old A-braced Ovations, not to use the .12-.53 "tow ropes" on these guitars, better use lighter strings. I prefer the Thomastik "plectrum" .11-.50 by Thomastik-Infeld.

Recently I bought the 1619 "Dan Savage" with the bearclaw top and forward X braces and even this guitar sounds VERY impressive with the Thomastiks.



I use Extra Light Elixir 80/20 Nanoweb strings on my deep-bowl Os (.10-.47) for this very reason.

You'll definitely want to use the lightest strings you can get on the 1619. When I built that guitar I thickness-sanded it down to .094" instead of the usual .100" to get the maximum response out of it.

What is the alloy of the Thomastik-Infeld strings? Are they phosphor-bronze or 80/20 bronze?
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Love O Fair
Posted 2017-02-07 9:04 PM (#532630 - in reply to #532531)
Subject: Re: Warped & Cracked Tops...



Joined:
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Posts: 459

Location: Spin axis of a California map
@Detlef ->>Thomastik "plectrum" .11-.50 by Thomastik-Infeld.<<-

I see those at several suppliers.. they are the model AC-111, right? How much tension load do they take off in comparison to using the 12-53 "tow ropes"? A lot? How do they sound in comparison to, say, the D'Ad EXP-16s or the Adamas 1818s?
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moody, p.i.
Posted 2017-02-07 11:00 PM (#532634 - in reply to #532531)
Subject: Re: Warped & Cracked Tops...


Joined:
March 2002
Posts: 15094

Location: SoCal
I believe that an Ovation needs strings on it heavy enough to drive the top. I've always played mediums (.13-.56) but have gone to lights (.12-.53). I believe that you lose a lot of tone with lighter strings. Dan knows this and the top on the Legend will be good for lights. I hope......
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DetlefMichel
Posted 2017-02-08 5:19 AM (#532638 - in reply to #532531)
Subject: Re: Warped & Cracked Tops...



Joined:
May 2011
Posts: 370

Location: Muenster/Germany
The AC 111 set has a tension of 125 lbs. I really don´t know what alloy it is but I`m quite sure that it is no phosphor bronce. These strings need careful cleaning (fast fret...). I have to admit that on some guitars they will sound a little too light, not really boombastic. But the TONE of these strings is remarkable, esp. when you like to play fingerstyle. On old 6 string guitars they can be the best for old guitar tops, but on 12 string guitars they are the absolute! ultimate! best! strings!!
I use Thomastiks because I have not so much physical power in the left hand due to chronical health problems with my forearm. I would never be able to play (or bend...) .12 or .13 strings. I know that my Martin D 45 guitar would sound greater with "normal" gauges, but I want to play it, so...
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DetlefMichel
Posted 2017-02-08 5:58 AM (#532639 - in reply to #532612)
Subject: Re: Warped & Cracked Tops...



Joined:
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Posts: 370

Location: Muenster/Germany

Here the 1619 before and after the treatment:

not perfect, but enough for me now:

A litte strange looking: the top of my 1759 12string. No cracks!

http://i1377.photobucket.com/albums/ah69/bluesman19591/Ovation%20repair/P1000199_zpseeqz03wh.jpg?t=1486468481

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Love O Fair
Posted 2017-02-08 10:11 AM (#532641 - in reply to #532531)
Subject: Re: Warped & Cracked Tops...



Joined:
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Posts: 459

Location: Spin axis of a California map
Detlef.. that last photo is blowing my mind. All that and no cracks.. amazing. What is the age of that 12er?
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DetlefMichel
Posted 2017-02-08 11:20 AM (#532642 - in reply to #532531)
Subject: Re: Warped & Cracked Tops...



Joined:
May 2011
Posts: 370

Location: Muenster/Germany
The guitar is from 1991. Maybe the movement of the structure was so slow that the finish did go along with it. It really looks crazy when you see the guitar hanging on the wall from a certain angle. But it sounds amazing with endless sustain, ridiculously low action. Could it be that the wave-type structure of the top has an other kind of sound projection? Could be a nice object for physicists....
I use the low-stress Thomastik strings and keep the guitar always de-tuned one halfstep (like all of my 12strings).
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DanSavage
Posted 2017-02-08 12:28 PM (#532644 - in reply to #532638)
Subject: Re: Warped & Cracked Tops...



Joined:
June 2012
Posts: 1578

Location: Lake Forest, CA
DetlefMichel - 2017-02-08 3:19 AM

The AC 111 set has a tension of 125 lbs. I really don´t know what alloy it is but I`m quite sure that it is no phosphor bronce. These strings need careful cleaning (fast fret...). I have to admit that on some guitars they will sound a little too light, not really boombastic. But the TONE of these strings is remarkable, esp. when you like to play fingerstyle. On old 6 string guitars they can be the best for old guitar tops, but on 12 string guitars they are the absolute! ultimate! best! strings!!
I use Thomastiks because I have not so much physical power in the left hand due to chronical health problems with my forearm. I would never be able to play (or bend...) .12 or .13 strings. I know that my Martin D 45 guitar would sound greater with "normal" gauges, but I want to play it, so...


That's pretty light tension. The Elixir extra lights have a tension of 131 lbs.

The lights have 158 lbs. and the mediums, 183 lbs.

Interestingly, the PBs have slightly higher tensions for all of the weights. (135 lbs, 162 lbs. & 188 lbs., respectively)

I use extra light strings on my torrefied tops for three reasons.

First, the tops are thinner than factory Ovation tops. The factory tops are tapered from .130" to .110". The torrefied tops are tapered from .120" to .100", so they would warp easier under the higher tension of mediums.

Second, and more importantly, I'm not sure what's the shear strength of the torrefied wood. I'm concerned whether the bridge would stay attached with the 183 lbs. of tension that the mediums exert. I know the bridge does stay attached with lights, but I haven't tried mediums and I'm not sure I want to find out on one of my guitars.

Now, a couple of bridge screws would help keep the bridge attached, but then the warping problem could rear its ugly head and accelerate the bellying of the top.

Third, I don't like how hard I have to push on the heavier strings when playing.

I treat the torrefied tops like I would a really old guitar and minimize the stress.
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DanSavage
Posted 2017-02-08 12:30 PM (#532645 - in reply to #532634)
Subject: Re: Warped & Cracked Tops...



Joined:
June 2012
Posts: 1578

Location: Lake Forest, CA
moody, p.i. - 2017-02-07 9:00 PM

I believe that an Ovation needs strings on it heavy enough to drive the top. I've always played mediums (.13-.56) but have gone to lights (.12-.53). I believe that you lose a lot of tone with lighter strings. Dan knows this and the top on the Legend will be good for lights. I hope......


Your guitar should easily handle the lights.
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DanSavage
Posted 2017-02-08 12:35 PM (#532646 - in reply to #532642)
Subject: Re: Warped & Cracked Tops...



Joined:
June 2012
Posts: 1578

Location: Lake Forest, CA
DetlefMichel - 2017-02-08 9:20 AM.
I use the low-stress Thomastik strings and keep the guitar always de-tuned one halfstep (like all of my 12strings).


I've always de-tuned my 12s down a full-step. When I got my 1655 I tried tuning it to concert pitch and after a while I noticed it started doing the same thing shown in your photo.

I de-tuned it back down, and the warping mostly went away. It still has a little bit of warping, but not nearly as much as what your photo shows.
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tpa
Posted 2017-02-08 1:39 PM (#532649 - in reply to #532644)
Subject: Re: Warped & Cracked Tops...


Joined:
December 2004
Posts: 404

Location: Denmark
DanSavage - 2017-02-07 7:28 PM
First, the tops are thinner than factory Ovation tops. The factory tops are tapered from .130" to .110". The torrefied tops are tapered from .120" to .100", so they would warp easier under the higher tension of mediums.


Not that I did any of the math to check, but my sense poposes that the brace profiles have a big role in taking the bending action from the offset forces from string tension. Could be interesting to calculate the bending properties of a cross section of the top+brace profiles.
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moody, p.i.
Posted 2017-02-08 4:11 PM (#532651 - in reply to #532646)
Subject: Re: Warped & Cracked Tops...


Joined:
March 2002
Posts: 15094

Location: SoCal
DanSavage - 2017-02-08 10:35 AM

DetlefMichel - 2017-02-08 9:20 AM.
I use the low-stress Thomastik strings and keep the guitar always de-tuned one halfstep (like all of my 12strings).


I've always de-tuned my 12s down a full-step. When I got my 1655 I tried tuning it to concert pitch and after a while I noticed it started doing the same thing shown in your photo.

I de-tuned it back down, and the warping mostly went away. It still has a little bit of warping, but not nearly as much as what your photo shows.

I have owned an Adamas 1 for over 20 years. It always has lights on it and is tuned to concert pitch. The top looks perfect and it sounds magnificent.

When I first got it, I put mediums on it. You could see the pull on the top. They came off in about 15 minutes......


Edited by moody, p.i. 2017-02-08 4:13 PM
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DanSavage
Posted 2017-02-08 4:30 PM (#532652 - in reply to #532649)
Subject: Re: Warped & Cracked Tops...



Joined:
June 2012
Posts: 1578

Location: Lake Forest, CA

tpa - 2017-02-08 11:39 AM

Not that I did any of the math to check, but my sense poposes that the brace profiles have a big role in taking the bending action from the offset forces from string tension. Could be interesting to calculate the bending properties of a cross section of the top+brace profiles.


The top and braces work together to resist string tension. Here's a good article by a structural engineer who's also a luthier that explains it.

The Guitar As A Structure (And Some Practical Information On Bracing)

Here's the meat of the article:

To explain how the stiffness of the braces (and the rest of the guitar) works, I need to introduce some engineering measurements that are used to define the stiffness of structures.  These measurements are section properties and material properties.  Section properties are inherent to the shape of the structure.  Material properties are inherent to the material it is made of.  They act together to define strength and stiffness.  Because engineers understand section properties and material properties (and properly apply them), buildings don’t fall down and airplane wings don’t fall off.

Most people have a tactile, “horse-sense” understanding of section properties:  If a wood plank is taller or wider, it will be stiffer (all other things being equal – this caveat applies throughout; I’ll not repeat it.  In real life, things are never equal.)  A thick Sitka spruce trunk is stiffer and stronger than a thin one.  A ¼-inch thick guitar top is stiffer and stronger than a 3/32-inch thick top.  These are all differences in section properties.

Section properties are simply the exact way that engineers use to measure a “stiffer than” or “stronger than” structural shape.  Section properties are determined exclusively by the shape and size of the structure.  Section properties are not affected in any way by the material – this is the key point.  A two-inch by four-inch plank will have the same section properties whether it is made of steel or plastic or butter.  Section properties are essentially perfectly understood by engineers and have been tested and confirmed millions of times.  They are simple to compute and formulas may be found in the suggestions for further reading (SFR) at the end of this article. Please note that a number of topics that are introduced in this article are discussed in much more detail in some of these suggested readings.

Separate from section properties the other important factor is material properties.  A two-inch diameter steel pipe is much stiffer than a two-inch diameter plastic pipe (both pipes have identical inside diameter (ID) and outside diameter (OD)).  This is the material effect.  Because the ID and OD are identical these two pipes have exactly the same section properties; they are different in stiffness (and strength) because they are made of different materials that have different inherent material properties. These inherent material properties are also precisely measured by engineers.  The primary material property of interest here is the modulus of elasticity, abbreviated as E, and generally referred to as “Young’s Modulus.”  The details on Young’s Modulus and how it is determined and used can be found in the SFR.

The article goes on to discuss material properties. Basically, red spruce is stiffer than Sitka spruce, which is stiffer than Englemann spruce, which is stiffer than red cedar, etc.

So, it's a combination of both that work to control the tension of the strings and are, in turn, affected by the tension of the strings.

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DanSavage
Posted 2017-02-08 4:36 PM (#532653 - in reply to #532651)
Subject: Re: Warped & Cracked Tops...



Joined:
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Posts: 1578

Location: Lake Forest, CA
moody, p.i. - 2017-02-08 2:11 PM

I have owned an Adamas 1 for over 20 years. It always has lights on it and is tuned to concert pitch. The top looks perfect and it sounds magnificent.

When I first got it, I put mediums on it. You could see the pull on the top. They came off in about 15 minutes......


Which is a perfect example of the differences in section and material properties as the above article discusses.

Basically, the CF/birch/CF laminate behaves very much like a cantilever beam.

The birch separates the two layers of CF so that each of them are able to resist both tension and compression. (bending forces)
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Love O Fair
Posted 2017-02-08 10:29 PM (#532661 - in reply to #532531)
Subject: Re: Warped & Cracked Tops...



Joined:
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Posts: 459

Location: Spin axis of a California map
@Dan ->>The primary material property of interest here is the modulus of elasticity<<-

Funny.. in my case it's not "Young's" Modulus.. it's "Old's" Modulus.. since it was just the other day when drying from a shower that I noticed the skin sag on the back of my legs and wondered what the proper term for that condition would be. You suppose switching to a heavier gauge of jeans will help?

Aside from that... good article. Thanks for posting.
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Love O Fair
Posted 2017-02-09 12:01 AM (#532663 - in reply to #532531)
Subject: Re: Warped & Cracked Tops...



Joined:
February 2016
Posts: 459

Location: Spin axis of a California map
My knowledge of guitar bracing is like, zip. So I read on. Figure 3 of the article gets into bracing shapes, including paraboloid. Now I'm picturing a paraboloid bracing strip as shaped something like a water flume flowing down a mountainside. Is that right? If so, then how in the heck would you securely glue (or otherwise attach) something like that to the back of a guitar top??

Edit: Okay, wait.. after more thought I think I might be wising up here. Is it flat across the bottom (as opposed to the flume example which is half-circle curved on the bottom) and glued on that flat side to the guitar's top wood, thus leaving two trough edges pointing upward and essentially doubling the bending modulus strength? Am I lost on this.. lol.

Edited by Love O Fair 2017-02-09 12:25 AM
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DanSavage
Posted 2017-02-09 12:28 AM (#532664 - in reply to #532663)
Subject: Re: Warped & Cracked Tops...



Joined:
June 2012
Posts: 1578

Location: Lake Forest, CA

Love O Fair - 2017-02-08 10:01 PM

My knowledge of guitar bracing is like, zip. So I read on. Figure 3 of the article gets into bracing shapes, including paraboloid. Now I'm picturing a paraboloid bracing strip as shaped something like a water flume flowing down a mountainside. Is that right? If so, then how in the heck would you securely glue (or otherwise attach) something like that to the back of a guitar top??


Yes. the paraboloid shape has the wider end (flat side) glued to the sound board.

I use the go-bars to clamp the pieces to the sound board. The trick is to make sure that the go-bars don't exert any side force that would force the braces to flip sideways. It's pretty much the same as using the go-bars to clamp 1/8" thick braces like those used on an A-brace top.







Edited by DanSavage 2017-02-09 12:30 AM
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Love O Fair
Posted 2017-02-09 12:45 AM (#532665 - in reply to #532531)
Subject: Re: Warped & Cracked Tops...



Joined:
February 2016
Posts: 459

Location: Spin axis of a California map
Dan.. and a whole other ponder on poly wood finishes. What bearing could the temperature of the wood and the liquid finish at the time of application have on how it holds up? Warm finish on cool wood.. cool finish on warm wood.. both cool.. both warm.. I would think that the proper mix of those combinations would be important to the longevity of a nice finish.

Edit again:: Man, as soon as I post a second question, you have already answered the first one! I've said it before, and again now.. you should host some occasional weekend seminars on this stuff where instant Q&A dialogue could take place. I'll gladly pay $100 to sign up for that (but you should have coffee and donuts, too).

Edited by Love O Fair 2017-02-09 12:55 AM
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DanSavage
Posted 2017-02-09 10:28 AM (#532671 - in reply to #532531)
Subject: Re: Warped & Cracked Tops...



Joined:
June 2012
Posts: 1578

Location: Lake Forest, CA
It's best is to have both the piece and the finish at the same temperature of no less than 65 degrees. Worst case is cold and damp.
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moody, p.i.
Posted 2017-02-09 9:27 PM (#532685 - in reply to #532531)
Subject: Re: Warped & Cracked Tops...


Joined:
March 2002
Posts: 15094

Location: SoCal
Dan, is that picture of a current project?
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DanSavage
Posted 2017-02-10 1:56 AM (#532691 - in reply to #532685)
Subject: Re: Warped & Cracked Tops...



Joined:
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Location: Lake Forest, CA
moody, p.i. - 2017-02-09 7:27 PM

Dan, is that picture of a current project?


No. That's the 1717. I started cutting out the braces for the current project(s). I'll finish cutting the braces tomorrow and will start gluing them to the top(s) thereafter.

I'll be starting with your 1117 and Daren's 1528, followed by the 1612 and the 1778T.
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moody, p.i.
Posted 2017-02-10 8:05 AM (#532697 - in reply to #532531)
Subject: Re: Warped & Cracked Tops...


Joined:
March 2002
Posts: 15094

Location: SoCal
Oh boy. Already this morning I was playing my 1537 and 1113. People, on the first guitar, Dan fixed structural problems and on the second, put a new top on. Both play and sound wonderful. West Coast Mothership?
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