Fretboard with 14' x 20' radius? Humm I build my fretboards (steel string) with 16 inch radius or 16" x 20" compound radius. 14' and 20' is going to be almost flat over a max 2 1/2"-2 3/8" freatbord width.

please this is just conversation    You said and I quote "The braces on my tops are shaped with a 26' diameter." Doing conventional math that is a 13' radius as shown in my sketch. Now I just showed a flat cord length of 20" along the center line of a 26' dome segment. If you tilt your sanding dome so that the the central axis of your dome tilts toward the neck end it does not make any difference in the rise of the sectional cord at its apex. A line from point to point 20" apart on a 26' diameter dome will have a .312" rise based on that cord length. Now the rise based on the upper bout width wise cross session would be less because the cord length is less. But on a lengthwise on a 20" cord length the only change you can make is the angle you view that cord from or in other words the angle of the cord plane in relationship to a theoretical horizontal plane

ok,

16 to 20 then it is.

i am still searching through the archives trying to find the best way to go about it.

oops I must not have made my point clear in my last reply to you.

I have no issue with the 14 x 20 on a freatbord other than I believe you mean inches and not feet. Fretboard radi are typicaly in inches 12" 14", 16" and so on

body domes are in feet 28' 25' 15' and so on

Michael,

No worries - I'm not being confrontational, I'm in my (almost always ) usual relaxed and cool conversational mode

Yes I use 13' radiused braces but no - I don't use a 13' sanding dish or any other sanding dish for that matter. As an extreme if I were to put all of my braces in the lower bout area and none in the middle to upper bout area then the profile of my top would not be like your diagram at all. That's my point really - you can make your top shaped like a section of a sphere if you want to , but to me that would be a load of . . . well round things. My top braces are all profiled to a 13' radius but front to back my tops are not the perfect section of a 13' radius spherical surface.

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Dave White
De Faoite Stringed Instruments
". . . the one thing a machine just can't do is give you character and personalities and sometimes that comes with flaws, but it always comes with humanity" Monty Don talking about hand weaving, "Mastercrafts", Weaving, BBC March 2010

Hesh there was no issue in the process of drawing an arc.

The issue came that I was assuming John was trying to form a radius for a top or back due to his mention of 28' and I wanted John or anyone to understand that a 28' radius dish actually has a 28' radius (56' diameter) dome not a 14'radius (28' diameter dome) this was my miss read of Johns real question

Come to find out John was referring to fretboard radii not tops or backs

I also believe John has gotten confused his dimensional units confused between feet and inches for fretboards

A picture is worth . . . well a few hundred words and iy's fun posting them anyway

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Dave White
De Faoite Stringed Instruments
". . . the one thing a machine just can't do is give you character and personalities and sometimes that comes with flaws, but it always comes with humanity" Monty Don talking about hand weaving, "Mastercrafts", Weaving, BBC March 2010

Cool!! To carry this conversation a bit further, confuse the heck out of everyone and really hijack the thread.

My opinion is that the X-brace sets the dome shape. Any brace that is glued on after the X-brace is glued up simply falls on a segment of the dome the X-brace formed.

Also if you use a 13' radii brace and clamp it to the top for glue up on a dish with a shallower bowl radius or deeper bowl profile, when release it will want to return to the 13' profile plus or minus some minimal imparted stretch or compression of the fiber.

John,

Sorry for hijacking your thread

I'm going back into my non-sperical workshop (aka shed) now where I rightly belong, where local rather than global maxima and minima occur in my building "eccentricities".

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Dave White
De Faoite Stringed Instruments
". . . the one thing a machine just can't do is give you character and personalities and sometimes that comes with flaws, but it always comes with humanity" Monty Don talking about hand weaving, "Mastercrafts", Weaving, BBC March 2010

I think the question is regarding Fretboards, which indicate Inches and not feet. Also, it is my understanding that a fretboard is not a spherical shape, but more of a conical shape, meaning just an arc. So a 14" radius fretboard is actually a 28" diameter Arc, or a 2d circle. Does that make sense?
Tracy

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Tracy
http://www.luthiersuppliers.com

I think it has all been straightened out already but just so that we are all clear!

When you speak of top/back radius it is just that, a radius, half the length across the circle (diametre). When I make a 15 foot radius dish it has a radius of 15 feet. It is section from a ball that would be 30 feet across. Just think of it as a panel in soccer ball.

Fretboard radii are in inches. Kim (larkim) recently posted a thread on the jig he just completed on radiusing a fretboard. that would be a great place to start.

Good Luck Jon

Shane

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Canada

[QUOTE=LuthierSupplier] I think the question is regarding Fretboards, which indicate Inches and not feet. Also, it is my understanding that a fretboard is not a spherical shape, but more of a conical shape, meaning just an arc. So a 14" radius fretboard is actually a 28" diameter Arc, or a 2d circle. Does that make sense?
Tracy[/QUOTE]

you got it!

Well, Shoot!  Discussions aren't fun anymore when everyone is on the same page.  A little misunderstanding goes a long way!  

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

I think you are mixing up terms here. See below:

The circumference is the distance around a closed curve. Circumference is a kind of perimeter.

Contents [hide] 1 Circle 2 Ellipse 2.1 Muir-1883 2.2 Ramanujan-1914 (#1,#2) 3 External links

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[edit] Circle

The circumference of a circle can be calculated from its diameter using the formula:

Or, substituting the radius for the diameter:

where r is the radius and d is the diameter of the circle, and ?I (the Greek letter pi) is the constant 3.141 592 653 589 793...

 

(If there is no image below, see support page.)

The radius of a circle is the length of the line from the center to any point on its edge. The plural form is radii (pronounced "ray-dee-eye"). In the figure above, drag the orange dot around and see that the radius is always constant at any point on the circle.

Sometimes the word 'radius' is used to refer to the line itself. In that sense you may see "draw a radius of the circle". In the more recent sense, it is the length of the line, and so is referred to as "the radius of the circle is 1.7 centimeters"

 

The radius is the radius...get it?

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Dave Bland

remember...

"If it doesn't play in tune...it's just pretty wood"

Was there even a mention of conference in this post? I thought the conversation was about the radius of a domes cross section.

I'm taking my ball and going home!  I'm obviously in over my head. 

_________________
Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

A fret board with a 14 radius on it is NOT conical - it's cylindrical, but with a tapered shape .. it would have to be a compound radii board (ie 12 to 20) to be conical.


The arc of a circle is NOT its radius, the arc HAS a radius - see above in MPs drawing he shows a chord (the 20 inch long section), and an arc - the chord is the straight line between the two end points, the curved, or radiused line is the arc - see wikipedia on geometry.

_________________
Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

 

Radius

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Dave Bland

remember...

"If it doesn't play in tune...it's just pretty wood"

And it r not square.

_________________
Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

All right, I've been a math teacher for nearly 40 years and ya'll are starting to get me confused.    Not really. Everyone here knows and agrees on the answer and everyone is doing the right thing in their building. I've never seen such a knowledgeable group tie such an ugly knot. This is NOT a thread for beginners. It needs a warning label.

Ron

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OLD MAN formerly (and formally) known as:

Ron Wisdom

Somewhere in the middle of Arkansas......

o.k. lost track of things here, but if any clarification is still needed:



using these drawings and the ever so useful Pythagoras thingy that says A^2+b^2 = c^2, you could easily create an arch that is related to a certain Radius(half a diameter).

this also means you do not need a,say, 14' long wire to create a decent arc that is a part of a circle with a 28' diameter.

every "S" has a matching "X" and they all relate directly to a given,pre-determined radius.

so if i wanted to draw an arch(28' Radius), and use that arc to make "rails" so my router could slide on them while routing out radius dishes, i could make a dish of a normal size(it doesnt have to be 28' "long").
say you average guitar body is 24" long, you just divide that lenght by 2 = 12"
so "S" = 12".
you want a radius of 28'.
so: S^2 +(R-X)^2 = R^2...
X= (2R +- sqrt((2R)^2 -4*(s^2)))/2.

since R and S are just numbers, this whole thing gets pretty solve-able.
if to be used, just make sure you convert the R's and S's to the same measurment system(all inches or all feet or whatever...)

in his book,Cumpiano, gives you the X and the S, so the R can be easily calculated as well.

hope this wasnt irrelevant!
Udi.

I hope no one entitles a thread: An Intelligent Question

Ron

_________________
OLD MAN formerly (and formally) known as:

Ron Wisdom

Somewhere in the middle of Arkansas......