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Hi all

When building an acoustic steelstring with a 25 - 30´radius soundboard, do you "radius" the sides before you glue the soundboard on the sides, just like its done with a radiused back? Or do you you glue the soundboard to sides where the edge is straight?

I hope my question can be understood. Sometimes I´m not sure I understand what i write myself.

I raidus both the top and bottom of the rim before either top or back goes on. On the top, I only radius form the butt to the waist, Then flat sand it from the waist to the neck block.

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Lance@LuthiersForum.com

You need to radius the sides just as you would when installing the back. Of course some people leave the upper bout flat. But either way you need your sides to match your soundboard. If you radius the entire soundboard the same should be done with the sides. If not you will get deformations around the edges or you will not have a good glue joint.

Yes you need to radius the sides to match the top and this is best done with a radius dish.
But you can build flat too, without radiusing the braces or the rim and therefore not needing a radius dish.
I did my first 5 that way and glued bracing on to the top a bit drier than normal so that at regular humidity levels a slight rise in the soundboard was induced. This was then glued to flat rims at 45%Rh.

The various adjustments to the upper bout area that are being suggested are to enable the fretboard to lay flat on the soundboard without shaving or packing, whilst achieving the appropriate neck angle and bridge height.

I have always glued a radiused top to flat sides. It works fine. My tops have a compound radius, but overall the average is about 35 feet.
I use a flat piece of 3/4" plywood against the top when gluing it on.
I radius the sides for the back, using a block plane and wooden gauges.

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John

Thanks for your answers

In my logics, a radiussed soundboard should be fitted to radiussed sides. If not, there will be tension in the soundboard. But I just wanted some feedback.

John,
Please explain what you mean about the 3/4" plywood against the top. Do you mean a narrow strip of plywood around the edges to spread the clamping pressure?

I use a radiused top and flat sides. I use a dish to radius the sides to match the radius of the back.

James

Sure it will. Just like when you string it up adds tension to the soundboard. Is there an assumption that tension on a soundboard is all bad?

I've built both ways. Don't know in my still limited build experience I have a definite preference yet. Both work, just different, and many guitars have been built both ways.

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Wes McMillian
Santo, TX
http://www.wesmcmillian.com

Is there an assumption that tension on a soundboard is all bad?

No, but it seems wrong to me to create a certain shape of a soundboard and then afterwards twist that shape into another shape.
I agree that all stinged instruments end up with tension in the soundboard. My experience is that the less tension you have in the soundboard before you string up, gives the best working instrument.
I wrote this thread because my experience is on building Spanish guitars only and even though I´ve made 100 of those, I feel that I need to relearn a lot of things now that I want to build a steelstring guitar. Its a different beast. Both to build and to play.

I use a radiused sound board and back. I have radius dishes but could never get the hang of using them.

My backs are 16' radiused but I don't use a straight line on them. I keep the back parallel with the top until it is within 2" of the waist, then I slope to the heel depth. The method in Cumpiano & Natelson

To make the top and back fit properly I use a radiused piece of wood (28' for the top & 16' for the back) to get everything right to accept the top and back. I just use block plane and sanding block to get the rims right.

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Joe Beaver
Maker of Sawdust

Mottola has a great description of how to use radius boards here: http://liutaiomottola.com/construction/Ribs.htm

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Doug

Don't let fear or common sense stop you from trying to build something

Use a 25 to 28 foot radius for the top.

Mike