Proper Radius for top and back?

[TinWhistle]

What is the range of preferred radii for tops and backs? Does this
'scale' with the size of the instrument? That is, would one expect the back
radius of a tenor ukelele to be about half that of a guitar? Do the uke
makes out there change the radius between their concert, tenor, baritone
ukes?
advThanksance,
Matt
***@hawaii.rr.com

[David C. Hurd]

Aloha Matt,

I make a nominal 30' radius for all size ukulele tops and 20' radius for
all ukulele backs. Looks ok and seems to work well...

aloha,

David C. Hurd
www.ukuleles.com

Post by TinWhistle
What is the range of preferred radii for tops and backs? Does this
'scale' with the size of the instrument? That is, would one expect the back
radius of a tenor ukelele to be about half that of a guitar? Do the uke
makes out there change the radius between their concert, tenor, baritone
ukes?
advThanksance,
Matt

[Dennis E.]

David wrote:

(snip)

Post by David C. Hurd
I make a nominal 30' radius for all size ukulele tops and 20' radius for
all ukulele backs. Looks ok and seems to work well...

(snip)

I'm guessing that the top and back radii you've chosen for your ukes
reflect the fact that there's less tension on the top than on a
guitar, so less arch is needed for support. Now I'm wondering if using
more arch would reduce volume by stiffening the top? Or are there
other considerations here? The point is interesting to me because I'm
thinking of making a tiple or two.

By the way, I an very much looking forward to your book! (I'm going to
try for an autographed copy, of course.)

D..

[David Hajicek]

I use a 25' radius for the top and a 15' radius for the back on a SS guitar.
These are common numbers, but you are free to choose some other radii if you
want. I don't think there is any magic numbers involved. After all, tops
used to be flat and the back just arched.

But I think the radius makes for a better performing instrument, not that I
can prove it.

Dave Hajicek

Post by Dennis E.
(snip)

Post by David C. Hurd
I make a nominal 30' radius for all size ukulele tops and 20' radius for
all ukulele backs. Looks ok and seems to work well...

(snip)
I'm guessing that the top and back radii you've chosen for your ukes
reflect the fact that there's less tension on the top than on a
guitar, so less arch is needed for support. Now I'm wondering if using
more arch would reduce volume by stiffening the top? Or are there
other considerations here? The point is interesting to me because I'm
thinking of making a tiple or two.
By the way, I an very much looking forward to your book! (I'm going to
try for an autographed copy, of course.)
D..

[l***@rubbishearthlink.net]

Post by David Hajicek
I use a 25' radius for the top and a 15' radius for the back on a SS
guitar. These are common numbers,

I can't do trig any more. Can someone tell me what radius gives 1/8" in
12"?

Jim L, via eCS 1.14 version of OS/2

[Mattia Valente]

Post by l***@rubbishearthlink.net

Post by David Hajicek
I use a 25' radius for the top and a 15' radius for the back on a SS
guitar. These are common numbers,

I can't do trig any more. Can someone tell me what radius gives 1/8" in
12"?

http://www.users.globalnet.co.uk/~coleman/Curves.htm

Excel spreadsheet there that should be able to help you out..

Mattia

[Brendan Thompson]

Forgive my newbie question, but I don't understand this post at all. Can
someone please enlighten me? I've only heard the term Radius used in terms
of fretboards...

Post by TinWhistle
What is the range of preferred radii for tops and backs? Does this
'scale' with the size of the instrument? That is, would one expect the back
radius of a tenor ukelele to be about half that of a guitar? Do the uke
makes out there change the radius between their concert, tenor, baritone
ukes?
advThanksance,
Matt

[Mattia Valente]

Post by Brendan Thompson
Forgive my newbie question, but I don't understand this post at all. Can
someone please enlighten me? I've only heard the term Radius used in terms
of fretboards...

Short version: The tops and backs of most acoustic guitars made today
are 'domed', built using dished workboards that are, essentially, a
section of a sphere (usually.) Back is arched more than the top.

http://edge.mcs.drexel.edu/GICL/people/sevy/luthierie/workboards/Arched_Workboards.html

That should tell you a whole lot more, though..

Mattia

[Alan Marshall]

On Thu, 19 Feb 2004 20:05:25 +1100, "Brendan Thompson"

Post by Brendan Thompson
Forgive my newbie question, but I don't understand this post at all. Can
someone please enlighten me? I've only heard the term Radius used in terms
of fretboards...

Tops and backs on acoustic guitars, and similar instruments, are
commonly built with a spherical radius in them.
This radius serves a number of purpouses.

1 It helps the plate to resist cracking
2 It makes the plate stronger from impact
3 It helps reduce the likelihood of standing waves in
the instrument, and hence 'wolf' tones
4 It helps the top resist the torsional forcs exerted
by the string pull on the bridge
5 It looks a whole lot better!

The fact that these rdii are there is sometimes lost on peolpe as some
call this type of instrument a 'flat top' guitar, which in most cases
is a misnomer. I only know of one maker who actually builds the tops
flat, but I also know another who builds his with a cylindrical radius
both top and back, and this gives his quitars a very distinctive look
as you can actually see the radius in the way it alters the side
shape.

Hope this helps you understand a little better.

Best Wishes, --
Alan Marshall
web site http://www.northworthy.com
e-mail ***@northworthy.com

[Brendan Thompson]

Post by Alan Marshall
The fact that these rdii are there is sometimes lost on peolpe as some
call this type of instrument a 'flat top' guitar, which in most cases
is a misnomer.

Well I'll be damned - pulled out my acoustic, and I can see the curves when
I hold it up to light! Thanks guys...

[Kent Fishburn]

"Alan Marshall" wrote in message

Post by Alan Marshall
I only know of one maker who actually builds the tops
flat,

There are some excellent guitars out there that are build with mostly flat
tops. There has to be some compensation for neck angle so none are totally
flat, but they have a flat lower bout . Charles Hoffman and James Olson
build flat tops with the upper bout shaved down to compensate for neck
angle. I know a couple other prominent builders that do other things with
the upper bout to achieve the correct neck angle and leave the rest of the
top flat. This practice is probably more widespread than we realize. It's
just rarely discussed.

Kent

[Kent Fishburn]

I shouldn't have said "none are totally flat". What I meant is, there has to
be some compensation for neck angle somehow.

Post by Kent Fishburn
"Alan Marshall" wrote in message

Post by Alan Marshall
I only know of one maker who actually builds the tops
flat,

There are some excellent guitars out there that are build with mostly flat
tops. There has to be some compensation for neck angle so none are totally
flat, but they have a flat lower bout . Charles Hoffman and James Olson
build flat tops with the upper bout shaved down to compensate for neck
angle. I know a couple other prominent builders that do other things with
the upper bout to achieve the correct neck angle and leave the rest of the
top flat. This practice is probably more widespread than we realize. It's
just rarely discussed.
Kent

[Alan Marshall]

Interesting Ken,
Now I know 3 who build 'em flat!

Best Wishes, --
Alan Marshall
web site http://www.northworthy.com
e-mail ***@northworthy.com

On Fri, 20 Feb 2004 07:45:46 -0600, "Kent Fishburn"

Post by Kent Fishburn
I shouldn't have said "none are totally flat". What I meant is, there has to
be some compensation for neck angle somehow.

Post by Kent Fishburn
"Alan Marshall" wrote in message

Post by Alan Marshall
I only know of one maker who actually builds the tops
flat,

There are some excellent guitars out there that are build with mostly flat
tops. There has to be some compensation for neck angle so none are totally
flat, but they have a flat lower bout . Charles Hoffman and James Olson
build flat tops with the upper bout shaved down to compensate for neck
angle. I know a couple other prominent builders that do other things with
the upper bout to achieve the correct neck angle and leave the rest of the
top flat. This practice is probably more widespread than we realize. It's
just rarely discussed.
Kent