Official Luthiers Forum!

What radius do you use for your tops and backs with regards to an OM size guitar? Does the intended playing style factor in to your choice of radius. Oh, and why do you use what you use. Not looking for just for numbers but the thoughts behind the choices.

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Aoibeann

15' back and 25' top here as well. When you've made 2 dishes of each size, believe me that is enough dust for anyone!

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

I use 28' top and 15' back for 000 and OMs 25' top and 15' backs on every thing larger. I just like a flatter top on smaller bodies. but 25' top would be fine.

15' & 25' here. Why...because that's what most others use. I'm open to change should someone convince me with data and facts.

I do, however keep the upper bout on plane with the FB extension by using a flat (non-radiused) transverse brace.

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JJ
Napa, CA
http://www.DonohueGuitars.com

good point JJ, I do the same to provide a flat surface for the FB extension

15 and 25 here also. I also do the same as JJ and Michael regarding the transverse brace...

-Mark

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Pullman, WA

The more I know, the more I know I don't know.

trippguitars.com
OR
Find me on Facebook

30 for the top, 15 for the back..

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Lance@LuthiersForum.com

18 and 28 ... because I can !!!

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

15 backs and 28 tops! For me the 28 foot radius gives me a perfect neck angle for my design...

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Peter M.
Cornerstone Guitars
http://www.cornerstoneukes.com

13' for the tops and 10' for the backs.

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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

Dave, you seem to be bucking the trend. I checked out your site and your guitars are beautiful. Any reason why you choose these radii?

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Aoibeann

[QUOTE=Aoibeann] Dave, you seem to be bucking the trend. I checked out your site and your guitars are beautiful. Any reason why you choose these radii?[/QUOTE]

Because he's certifiably weird , but he does build great sounding and great looking guitars. I just love it when people think outside of the box (great pun eh!) and Dave does just that. It makes me proud to be British so it does!

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

[QUOTE=Colin S] Because he's certifiably weird , but he does build great sounding and great looking guitars. I just love it when people think outside of the box (great pun eh!) and Dave does just that. It makes me proud to be British so it does!

Colin[/QUOTE]

Okay.


While I'm asking questions, why do we build with a different radius for the front and the back?

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Aoibeann

[QUOTE=JJ Donohue] 15' & 25' here. Why...because that's what most others use. I'm open to change should someone convince me with data and facts.

I do, however keep the upper bout on plane with the FB extension by using a flat (non-radiused) transverse brace. [/QUOTE]

In regards to the non radiused brace do you guys still glue this brace in the dish ??
how does this work

i have just finished making 25' and 15' dishes and the backyard looks like its been snowing in summer...My router and i never want to do this again.

[QUOTE=Aoibeann] Dave, you seem to be bucking the trend. I checked out your site and your guitars are beautiful. Any reason why you choose these radii?[/QUOTE]

Lillian,

Because the guitars I liked the most and aspired to build were those of Stefan Sobell. He uses a huge cylindrical arch on the back and a pretty big one on the top - inspired by an old Martin archtop aparrently.

These are the radii I put on the bottom of the braces. I don't build in spherical molds though, and most of the arching on the tops is from the soundhole backwards. I do have a lateral arch on the upper-bout, but this isn't an issue for me as my fingerboards are free floating over the body. I like the projection, sustain and help towards string balance that this degree of arching gives as part of my overall design.

My own theory on why the back and top have such different arches is tradition, back to the old instruments that evolved into guitars - lutes are an example. Flattish tops and bowl backs. This transformed into classical guitars with bigger arch in backs and flattish tops and moved into steel strings. My theory anyway.

Colin - it helps to be "barking" when you have 4 daughters and even the dogs are all femaile Dave White39031.7417013889

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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

[QUOTE=Dave White] Colin - it helps to be "barking" when you have 4 daughters and even the dogs are all femaile [/QUOTE]

Oh Dave, you have my sympathies!


Everyone else, thanks for the input.

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Aoibeann

[QUOTE=Dave White]Because the guitars I liked the most and aspired to build were those of Stefan Sobell. He uses a huge cylindrical arch on the back and a pretty big one on the top [/QUOTE]
Interesting, Dave. That's been cooking inside my head too, since seeing a Sobell on the cover of a Guitarmaker magazine several years ago. I'm planning to build with a cylindrical arch, if I can get my act together enough to start and finish a guitar before the Winter (and low humidity) is over.

So, am I understanding you correctly--are you building with a cylindrical arch, but not bracing in a dish? If so, how do you achieve your arch?

15' AND 25' here, would like to think outside of the CCF box!

This thread posed a question for me that I could not find the answer to.
I am building my first by the Cumpiano book and I cannot find anywhere
in the book where it states the radius of yop or back.
Anyone know the answer? Curious cats would like to know.

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Christopher C. Cordle
North Muskegon, MI

http://www.yardsaleunderwear.com
http://www.facebook.com/christopher.cordle

[QUOTE=CarltonM]
So, am I understanding you correctly--are you building with a cylindrical arch, but not bracing in a dish? If so, how do you achieve your arch? [/QUOTE]

Carlton,

Not cylindrical. I put the arches on the bottom of the braces and glue them to the top and back in a go-bar deck using cork shims around the sides (I think I got this from Jim Williams book):



The top/back and braces then decid how they are going to equalise tension and settle into shape. These are the best pics I have of the sort of shape (I need to do some better ones):

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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

One good way of skinning the cat, i love that Dave, thanks!