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Thread: Top and back graduations

  1. #1

    Default Top and back graduations

    Iím building my second kit, this time from Stew Mac, and notice the thicknesses vary quite a bit, well really only several thousandths, from my recollection of the Arches kit I built a year or so ago. The StewMac kit uses Siminoff thicknesses. The Siminoff measurements are thicker in the bridge area but thinner in the neck and heal areas. I think the edges are within a thousandth or so. Since the top woods are Adi vs European spruce, are the differences to compensate for different wood varieties, or more for stylistic tonal reasons.

    Do you builders carve for species differences? Tonal variation? Wood stiffness properties? All the above? And when you build something you think is special, how do you duplicate it?

    Iím just hoping for different than before for this particular build.
    Silverangel A
    Arches F style kit
    1913 Gibson A-1

  2. #2
    Registered User sunburst's Avatar
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    Default Re: Top and back graduations

    Quote Originally Posted by Br1ck View Post
    Do you builders carve for species differences?
    Not really.

    Quote Originally Posted by Br1ck View Post
    Tonal variation?
    A little bit. I feel that I have some control over sound, but once materials are chosen there are limits.

    Quote Originally Posted by Br1ck View Post
    Wood stiffness properties?
    Yes, but density figures into that with about as much importance.

    Quote Originally Posted by Br1ck View Post
    All the above?
    See above.

    Quote Originally Posted by Br1ck View Post
    And when you build something you think is special, how do you duplicate it?
    They're all special!
    Seriously, I feel that I have developed consistency of sound, though I do have my favorites. Duplicating a sound (meaning exactly the same sound down to details) using other materials is nearly impossible for me, but I always expect a good sound if I do things right.

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  4. #3

    Default Re: Top and back graduations

    Experienced, talented and successful builders seem to have an uncanny ability to evaluate components as they are carving, tapping, flexing and measuring each piece of wood. Their graduations will vary from instrument to instrument. This is an ability that I have not yet developed. But, it is fun .

  5. #4
    Adrian Minarovic
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    Default Re: Top and back graduations

    I made mandolin out of SM kit years ago. I remember the plates were left quite thick machined more or less to uniform thickness of 5mm except the back towards neck that had more meat.
    I would suggest going by good reliable numbers (taken from time proven good instrument, assumng the wood species are same or very similar) and try to remember how the plates flex and feel in fingers, that helps in future judging of the perceived stiffness using different pieces of wood.
    From my limited experience I can say that there are areas of building that are much more important to master than judging the thicknesses for good sound and playability - like good arching shape, good neck geometry, fretboard work and setup etc. It all works together.
    Adrian

  6. #5

    Default Re: Top and back graduations

    I'll just go by the plan numbers. I guess the guy building Red Diamonds knows what he's doing. A big part of the fun at this stage is making anything that sounds good, much less targeting a sound. It is supposed to be a bluegrass mandolin, whatever that means.
    Silverangel A
    Arches F style kit
    1913 Gibson A-1

  7. #6
    Registered User fscotte's Avatar
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    Default Re: Top and back graduations

    The shape of your arch will determine the thickness.

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  9. #7

    Default Re: Top and back graduations

    ".......I guess the guy building Red Diamonds knows what he's doing......"

    The search engine will generate close to 1000 previous threads about graduations, arches, and their effect on voice as well as several very accurate, predictable ways to generate the specific voice you are trying to build.
    Spruce dork

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  11. #8

    Default Re: Top and back graduations

    If you use redwood or Western Red Cedar the tops have to be somewhat thicker to be strong enough.

  12. #9

    Default Re: Top and back graduations

    Quote Originally Posted by grandcanyonminstrel View Post
    ".......I guess the guy building Red Diamonds knows what he's doing......"

    The search engine will generate close to 1000 previous threads about graduations, arches, and their effect on voice as well as several very accurate, predictable ways to generate the specific voice you are trying to build.
    And I ask you, what would we read every day if we got all our info from searching the archives? Time to start a BC pick thread, or maybe a what's the best mandolin I can get for $100.
    Silverangel A
    Arches F style kit
    1913 Gibson A-1

  13. #10
    Adrian Minarovic
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    Default Re: Top and back graduations

    Quote Originally Posted by Br1ck View Post
    I'll just go by the plan numbers. I guess the guy building Red Diamonds knows what he's doing. A big part of the fun at this stage is making anything that sounds good, much less targeting a sound. It is supposed to be a bluegrass mandolin, whatever that means.
    If that means you plan to follow Stew-Mac drawings' thicknesses I would add that those are a bit out-dated by now. You can find a lot of reliable newer measurements and general graduations of Loars online (here on MC) to follow. SM is big company and AFAIK they still sell the same drawing that they used 20 years ago without any revision and that certainly deviates from Loar. (it tool GAL 10 years or so to revise completely wrong neck attachment on their drawings- 14the fret instead of 15th). I published my drawings but for graduation numbers you don't need to buy, everything is out there.
    Search for original "Loar" specs sheets and threads about them and follow that as workers at Gibson did.
    Adrian

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  15. #11

    Default Re: Top and back graduations

    With only 5 builds under my belt I can tell you that my instinct that thinner tops would sound better was wrong. For your second build, you may want to consider erring on the conservative side and then string it up in the white and see how it sounds. You can always take off a little more wood, but you can't put it back. It seems I read in an interview with one of the great builders (can't recall which one, LOL) that he built 10 mandolins before he really knew what he was doing. Don't think I'll live long enough to reach that benchmark. Enjoy the adventure.

  16. #12

    Default Re: Top and back graduations

    Quote Originally Posted by Br1ck View Post
    Do you builders carve for species differences?
    Yes, absolutely. Not for, say, Red spruce vs. Sitka, in which no major species generalizations are going to hold true all the time.
    But let's say you get a set of graduations that works well in Sitka, and then you want to make a redwood or cedar mandolin. If you use the same numbers, you will either get a redwood instrument that sounds like a banjo (not enough structure, just loud and harsh) or one which fails to support the string tension. I built two redwood-topped archtop mandolins based on the general advice, "carve redwood a little thicker than spruce". Which is true. So I made the centers around 20% thicker than Loar specs, and the recurve 10-15% thicker. They sounded bad and failed structurally after a short period of time (fortunately they were experiments and not for sale).

    Actual redwood specs which work are more like 70% thicker in the center. The recurve can still be pretty thin, maybe 20% thicker than Loar specs.
    My initial rough carving target for redwood is .130"/3.3mm in the recurve, .300"/7.6mm in the center. A good stiff piece of redwood will end up between .250"/6.3mm to .300"/7.6mm in the center, but leave the area under the neck and under the bridge proportionally a bit thicker than you would in spruce. So if your recurve is .130"/3.3mm, maybe keep the are under the bridge and fretboard in the neighborhood of .200"/5mm.

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  18. #13
    Registered User sunburst's Avatar
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    Default Re: Top and back graduations

    Quote Originally Posted by Marty Jacobson View Post
    Yes, absolutely. Not for, say, Red spruce vs. Sitka, in which no major species generalizations are going to hold true all the time.
    But let's say you get a set of graduations that works well in Sitka, and then you want to make a redwood or cedar mandolin. If you use the same numbers, you will either get a redwood instrument that sounds like a banjo (not enough structure, just loud and harsh) or one which fails to support the string tension. I built two redwood-topped archtop mandolins based on the general advice, "carve redwood a little thicker than spruce". Which is true. So I made the centers around 20% thicker than Loar specs, and the recurve 10-15% thicker. They sounded bad and failed structurally after a short period of time (fortunately they were experiments and not for sale).

    Actual redwood specs which work are more like 70% thicker in the center. The recurve can still be pretty thin, maybe 20% thicker than Loar specs.
    My initial rough carving target for redwood is .130"/3.3mm in the recurve, .300"/7.6mm in the center. A good stiff piece of redwood will end up between .250"/6.3mm to .300"/7.6mm in the center, but leave the area under the neck and under the bridge proportionally a bit thicker than you would in spruce. So if your recurve is .130"/3.3mm, maybe keep the are under the bridge and fretboard in the neighborhood of .200"/5mm.
    To me that all comes under "wood stiffness properties" as well as split resistance, stability and other things that were not specifically mentioned. If I have a piece of wood that is low density, low stiffness, etc. Ill carve accordingly whether it's redwood, WRC, or other.
    I do start with somewhat preconceived notions when carving engelmann as opposed to red spruce (for example), leaving a little extra wood until final stages, but final carving comes down to stiffness rather than species.

  19. #14

    Default Re: Top and back graduations

    Quote Originally Posted by sunburst View Post
    To me that all comes under "wood stiffness properties" as well as split resistance, stability and other things that were not specifically mentioned.
    I get that - now, after building several failed instruments, at least. I was mostly saying it hoping to save others in the same place from as much time as I wasted.

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  21. #15

    Default Re: Top and back graduations

    Quote Originally Posted by Marty Jacobson View Post
    .... I was mostly saying it hoping to save others in the same place from as much time as I wasted.

    That's the number one reason why I respond here and ironically the number one reason for getting flamed out by folks who seemingly have never built one instrument but know more than my 300+....
    Spruce dork

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    Default Re: Top and back graduations

    There's a lot of talk about thicknesses and that's very important, but to me the actual shaping of the plates is the key. It seems that many new builders don't get the recurve right. It isn't a trench around the outside, it's a gradual valley. That's what allows for the top (and back, just as importantly) to flex. Doesn't matter what the grads are, if you don't get that part right you probably will end up disappointed.
    Go to the Mandolin Archive and study all the photo's Loars. Pay attention to the reflections of the recurves. Check out Gilchrist and Heidens work.

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    Registered User fscotte's Avatar
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    Default Re: Top and back graduations

    Right Jim, I feel the shape of the arch/plates is significantly more important than the thickness.

    Even minor differences in the arch will affect the strength of the plate.

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    Adrian Minarovic
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    Default Re: Top and back graduations

    Sure the shape of arch and it's flow is one of the most important things. From my experience the beginning builders seem to suffer in both getting correct smooth arching shape and good graduations and as they gain experience both areas improve.
    Adrian

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    Default Re: Top and back graduations

    Good morning. I have built 5 instruments using the Siminof plans with the longer nose section. I just like the looks of it better. Tops, red spruce, are usually .180 in the center and .115-.120 in the recurve. Backs, red maple, are usually .190 center and .115-.120 in the recurve. Arch height is in the 15-15.5mm range. Still have not been able to get one that I think sounds really good. Mentor says they dont have any pop, but I have not learned to hear what he is speaking of. I seem to deal with a tinny sound. Any recommendations on what I should try on #6.
    Thanks, Graham

  29. #20
    Adrian Minarovic
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    Default Re: Top and back graduations

    I don't understand the "nose section" term...?
    What is tinny sound? Does it mean shrill high notes and lack of crispy solid bass? If so, that means your top is likely too stiff. With good piece of RS you can go close to 4mm in the center and down to 3mm at recurve. I would taper that towards neck to some 3.5mm or so under florida and back to 4.5mm edge thickness under extension gluing surface. How are your tonebars? Siminoff shows them higher than typical Loar size. Back at 0.190 seems rather thick I aim at 4mm below bridge position, perhaps a tiny bit more for softer Red Maple (especially slab) and I would not fear going close to 2.5mm (0.100") at recurve of back but the thickness of Loars usually increases all the way from center towards neck block (ends at about 7-7.5mm) as the arch is still quite high over the block. Good shaping of recurve may be critical for good sound and placement of highest spot of top arch (I like it right under bridge) and not too full roundish long arch, closer to parabolic - that is IMO one of the most important aspects of top arch. If you do the highest spot ~1" behind bridge like in the drawings the top may deform over time and bulge out even more if it is worked thin. Old mandolins often show the highest spot of arch behind bridge because of deformations that happened over 80 or so years but the more healthy Loars, or thicker Ferns from later periods still carved on the same form, have the apex right under bridge or still very close. Fitting bridge to such arch so it won't lean forward is funny.
    As far as tuning the graduations goes there is ooooold thread called "outside tuning" where I described to detail what I was (and mostly still am) doing.
    Adrian

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    Default Re: Top and back graduations

    Concerning the reference to the Stew-Mac print, I learned the hard way that those grads are way too heavy. They show 1/4" in the center which is what you might find on an archtop guitar.
    Adrian can't advertise his prints here but I can. Get a set and hang the Stew-Mac's on the wall as art.

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  33. #22
    Henry Lawton hank's Avatar
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    Default Re: Top and back graduations

    Gilchrist has some good basic information on the directions an instrument can be taken and how he does it at his Web site. Heiden suggest that too thin a top looses richness of tone and too thin a recurve weakens the power that the plate gets from the rims.
    Has anyone compared actual Loar Era snakehead and F4/2 top and back graduations to to their teen counterparts? I hope to measure my 13 A4 and 23 F4 this coming year and am interested in finding more actual snakehead and F2/4 arching and graduation measurements. I’m also interested in these instruments break angle. I often read of hybrid long neck ovals sounding more percussive like their cousin the F5 and wonder if this added pop is caused by increased break angle and centering of the bridge more than the longer neck dimension.
    "A sudden clash of thunder, the mind doors burst open, and lo, there sits old man Buddha-nature in all his homeliness."
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  35. #23
    Registered User fscotte's Avatar
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    Default Re: Top and back graduations

    Quote Originally Posted by graham darden View Post
    Good morning. I have built 5 instruments using the Siminof plans with the longer nose section. I just like the looks of it better. Tops, red spruce, are usually .180 in the center and .115-.120 in the recurve. Backs, red maple, are usually .190 center and .115-.120 in the recurve. Arch height is in the 15-15.5mm range. Still have not been able to get one that I think sounds really good. Mentor says they dont have any pop, but I have not learned to hear what he is speaking of. I seem to deal with a tinny sound. Any recommendations on what I should try on #6.
    Thanks, Graham
    If building to Griffith Loar A standards, you may wanna pay more attention to the arching.

    Dudenbostel described it as "long and low". I wouldn't trust the Siminoff plans either. One reason being that the size and shape of the peghead isn't accurate. Makes me wonder if the arching profile is off as well..

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  37. #24

    Default Re: Top and back graduations

    I wouldn't trust the Siminoff plans either. One reason being that the size and shape of the peghead isn't accurate. Makes me wonder if the arching profile is off as well..
    The Siminoff arching is off. If you measure the center height at the width cross sections and in the center lengthwise cross section they do not match especially at the end toward the tailpiece.

    I had a lot of difficulty getting the arching to work on my first two mandolins. The graduations were difficult as a result of the cross sections being wrong also. I scrapped two tops figuring it out. I checked the plans and found the problem. Number 3 went much better as a result of resolving the differences by redrawing a couple of cross sections. I will probably go over them again to make sure the high point is located correctly.

    I had questioned the fact that his highest point seemed to be below the bridge also. Adrian's comments confirmed my concern. From a structural strength perspective the bridge should be at the high point. That is basic structural design and statics.
    Last edited by CarlM; Nov-13-2019 at 3:51pm.

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  39. #25
    Mandolin & Mandola maker
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    Default Re: Top and back graduations

    To me that all comes under "wood stiffness properties" as well as split resistance, stability and other things that were not specifically mentioned. If I have a piece of wood that is low density, low stiffness, etc. Ill carve accordingly whether it's redwood, WRC, or other.
    I do start with somewhat preconceived notions when carving engelmann as opposed to red spruce (for example), leaving a little extra wood until final stages, but final carving comes down to stiffness rather than species.
    Yep, exactly, and also stiffness of the back and how it relates to the top. Way too much attention is paid to thickness measurements which are pretty much irrelevant if you don't pay attention to actual stiffness.
    Peter Coombe - mandolins, mandolas and guitars
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