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L-00 top and back radius
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Author:  coach [ Thu May 20, 2010 7:27 pm ]
Post subject:  L-00 top and back radius
I'm a newbie, obviously, to guitar building. :) Well, I've decided to try and build a very close copy of a Gibson L00, and am stumped at the top and back radius. I was planning on just keeping it simple and purchasing a couple radius domes to use with a go bar deck, and also use some templates that LMI sells for making my bracing. I purchased the plan from LMI, but the plan merely gives a top "dome", side-to-side measurement of 3/16"; and a back "dome" measurement of 3/16" crosswise, and 1/8" lengthwise. The plan also mentions "bellying" of the top, but mentions no measurement of this. Please help if you can.

If someone can just give me the degree of radius on the top and back, I'll keep it simple.

Thanks for any help you can offer this newbie.
Author:  GW20 [ Thu May 20, 2010 8:06 pm ]
Post subject:  Re: L-00 top and back radius
Welcome to the group, I too am a newbie building a Gibson L-00.
The plans came from this site.
http://www.grellier.fr/plans.php?lang=en
I had the plans printed out full scale at work on mylar. Great stuff that mylar.
these plans are free to download in PDF or DXF format.
the back radius is 15' and the top is 28'

I would be curious as to the top bracing width and height on your plans. These plans call for the X braces to be 14mm at the high point and 5mm wide.

Let me know what your plans say....

Thanks
Jerry
Author:  Pat Foster [ Thu May 20, 2010 9:42 pm ]
Post subject:  Re: L-00 top and back radius
coach,

Welcome.

Try this web page. You may have to exercise some algebra, but it's a good start.

http://www.liutaiomottola.com/formulae/sag.htm


Pat
Author:  JohnAbercrombie [ Thu May 20, 2010 9:55 pm ]
Post subject:  Re: L-00 top and back radius
coach wrote:
If someone can just give me the degree of radius on the top and back, I'll keep it simple.


EDIT- Pat types faster than me!-EDIT
R.M. Mottola's excellent website has a page about the arithmetic involved in these sorts of problems.
There are calculators on the page.
http://liutaiomottola.com/formulae/sag.htm
However, it sounds like your plans are not using a 'spherical' radius model.
For instance, you say the back has 1/8" arching along the length but 3/16" across the width? With a spherical radius, the longer distance (length) will have the greater amount of arch.
Generally guitars of that type are built without a radius dish, though certainly you could adapt the plan to using a radius dish.
The back arching is not very important- as long as you have some arch and the back joins the sides well, without distortion you are OK.
The top arch needs to be taken into consideration to make sure that the neck/fingerboard 'line up' to put the strings at the 'right' height over the soundboard at the bridge location. It sounds like the sides can be planed 'flat' to join to the edges of the soundboard, using your plan. So you probably don't need radius dishes, and certainly don't need to buy a 'brace template'.

Making a side view drawing with fingerboard, string, soundboard and bridge will make this quite clear.

Now is the right time to be thinking about all this!
[:Y:] [:Y:]

Cheers
John
Author:  coach [ Fri May 21, 2010 6:59 am ]
Post subject:  Re: L-00 top and back radius
JohnAbercrombie wrote:
coach wrote:
If someone can just give me the degree of radius on the top and back, I'll keep it simple.


EDIT- Pat types faster than me!-EDIT
R.M. Mottola's excellent website has a page about the arithmetic involved in these sorts of problems.
There are calculators on the page.
http://liutaiomottola.com/formulae/sag.htm
However, it sounds like your plans are not using a 'spherical' radius model.
For instance, you say the back has 1/8" arching along the length but 3/16" across the width? With a spherical radius, the longer distance (length) will have the greater amount of arch.
Generally guitars of that type are built without a radius dish, though certainly you could adapt the plan to using a radius dish.
The back arching is not very important- as long as you have some arch and the back joins the sides well, without distortion you are OK.
The top arch needs to be taken into consideration to make sure that the neck/fingerboard 'line up' to put the strings at the 'right' height over the soundboard at the bridge location. It sounds like the sides can be planed 'flat' to join to the edges of the soundboard, using your plan. So you probably don't need radius dishes, and certainly don't need to buy a 'brace template'.

Making a side view drawing with fingerboard, string, soundboard and bridge will make this quite clear.

Now is the right time to be thinking about all this!
[:Y:] [:Y:]

Cheers
John


Thanks John,

I really appreciate the advice. Since there is no measurement given for the top, lengthwise, does that mean the top is on a straight plane lengthwise? Also, can you explain to me the difference between "dome" and "bellying"? If you were building a guitar without a spherical radius, How would you get the sides angled correctly to join the top and back? Thanks again.

Sean
Author:  truckjohn [ Fri May 21, 2010 9:50 am ]
Post subject:  Re: L-00 top and back radius
Back in the day -- there were *Many* methods of putting a curve in the top and back.... Unfortunately, none of those methods used a true spherical "Radius Dish" from the historical info I could dig up...

A couple ways I have dug up....
1. Spanish solera method -- a workboard that has a "Hollow" in it (Sometimes curved, sometimes not.lo)
2. Curved braces "Sprung" onto a flat top or back plate
3. Flat braces glued to a super-dry plate -- which would then "Swell" back out into a curve when the plate re-humidified...
4. For a conventional braced Back, or the top of a ladder braced guitar -- Curved braces glued onto the linings to form a skeleton looking deal, then the plate is glued onto the whole assembly

The old "Authentic" L-00 instruments probably used the 2nd method -- curved braces clamped to a flat plate... If you look at the back brace profiles, you may find that they aren't all the same curve per amount of length... Typically, they used more curve at the waist, some curve at the lower bout, and less curve in the upper bout...

I don't know for sure whether Grellier's plans use a true "Radius" or whether they just use curved braces....

Cumpiano's book shows 1 traditional method of shaping the curved braces and then levelling the rims with a sanding board.

On the question of how do you clamp it up? You could use lots of clamps. You could "Rope" it with string or elastic bands, or any number of other ways of holding it all together... (I used ratchet tiedown straps on one of mine, clamps on 2-others, rope on another, and a big pile of books and clamps on another...) Turns out many of those old ways work just fine.

So...

There are several answers to your question....

You could use a radius dish if you want -- many people use 15' for the backs on *everything*...

For the top... you could also use a radius dish if you want.. Many people seem to use 28' for everything...

But.. You don't have to... Many builders don't use radius dishes... and their guitars come out great.

Thanks
Author:  JohnAbercrombie [ Fri May 21, 2010 11:58 am ]
Post subject:  Re: L-00 top and back radius
coach wrote:

Thanks John,

I really appreciate the advice. Since there is no measurement given for the top, lengthwise, does that mean the top is on a straight plane lengthwise? Also, can you explain to me the difference between "dome" and "bellying"? If you were building a guitar without a spherical radius, How would you get the sides angled correctly to join the top and back? Thanks again.

Sean


Sean -
John Cox has given an excellent answer -lots of good info there.
If I were building your project, I'd probably just finish the sides 'flat' where they meet the top (use a flat sanding board, or a flat piece of plywood for checking, and a block plane.) Classical guitars, which are built with a 'dome' in the bridge area are put together this way.
Dome, bellying, radius, are all pretty vague terms- I see them used in different ways. Some plates are shaped to a part of a sphere, others to part of a cylinder, others to some more complex shape. The curvature on most guitar tops is not very great, so you can get away with some variation from the perfect geometry. I generally figure that I should be able to get good contact between the plate and side all around, just using finger pressure or strips of masking tape to hold things together for checking. Once the plate is temporarily taped in place, you can check for good contact on the inside of the guitar as well. You should not need a great deal of clamping pressure to clamp a plate for gluing- a good (padded or semi-flexible) clamping caul helps, as do lots of areas of light clamping.
Fitting by hand using a block plane or sanding stick is not very difficult; it just takes some time and patience.

Cheers
John
Author:  Christophe Grellier [ Sat May 22, 2010 4:10 am ]
Post subject:  Re: L-00 top and back radius
Quote:
I don't know for sure whether Grellier's plans use a true "Radius" or whether they just use curved braces....

Hello,
I did draw the plan with a true radius. I agree that it is not historically correct, but the top and back of my Gibson are pretty deformed : the top is bellied and the back has some cracks that were not repaired well. So I could not simply "measure and draw" the arches of the guitar. I had to guess and presume.
I hope you'll understand my bad english.

Christophe
Author:  coach [ Sat May 22, 2010 6:23 am ]
Post subject:  Re: L-00 top and back radius
Christophe,

Thanks for replying, and I just wanted to tell you I think your guitars are absolutely beautiful. As a matter of fact, the first guitar I want to start building is going to be inspired by your Fedora. I love playing 12 fret guitars, and I really appreciate you sharing your plans online for the L-00. For your Fedora, did you just adjust the bridge location, x brace, and soundhole for the shortened neck?

Thanks,

Sean
Author:  JohnAbercrombie [ Sat May 22, 2010 11:57 am ]
Post subject:  Re: L-00 top and back radius
Christophe-
I just wanted to add my sincere "thank you' for your excellent website and plans.
Building a guitar from your plans is now on my 'project list'.

Cheers
John
Author:  Christophe Grellier [ Sun May 23, 2010 7:29 am ]
Post subject:  Re: L-00 top and back radius
Thank you, Sean and John.
Sean, you are right, the main modification I made for the Fedora was to slide everything toward the tailblock. Maybe I also made some other adjustements with the help of pictures of opened 12fret L-00s found on the web. But, apart from the upper transverse brace, I don't remember if I modified something else. Just keep in mind to make the guitar lightweight, I think this is most important on that kind of guitar.
Good luck,
Christophe
Author:  GW20 [ Sun May 23, 2010 9:39 am ]
Post subject:  Re: L-00 top and back radius
Coach,
The plans are great from Christope. Make sure when you print them they print at 100% and not the default fit to page.

Christope, I too am using your plans for the L-00. Great plans and a great site! Thanks.

I am now ready to radius the bracing. The top has been laid out and I'm quite excited to start the process.

Thanks!!
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