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I think I am going to transition from spherical to cylindrical tops and backs. I would rather buy a sanding board rather than make it. Does anyone sell such a thing?

John

I don't know anyone that sells them, I had to make my own. I would rather have bought one. They're not difficult to make (not anymore than spherical), it's just messy and sort of a pain.

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Jonathan Kendall, Siloam Springs AR

I would think it would be easier to make. Just start with a rectangle and keep your radius guide 90° perpendicular to the board.

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Joe Breault
Merrimack, NH
Perpetual novice

John,
You could just buy some of my radius gauges to use as a template. Just double stick tape my radius gauge to some 1x2's that are 20" long and route with a bearing guide. Then just glue all of them together with poly glue. Should give you what you want. Good luck!
Tracy

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Tracy
http://www.luthiersuppliers.com

Thanks guys

   Todd that looks very doable. I have something like that already only in reverse for sanding a curve on the bottom of my bridges.

   This is a subject that I hope I can shed some light on . Unlike domeing the contour is in one direction. This makes bracing layout very diffiecult.
   You now have to havee a comound radius on your braces unless you use ladder braces. That is what prabolicing works so well as the radius is a natural fit .
    with cylinder shaping the radius on the brace is no longer a static but a dynamic shape. THings we learn in calc class.
   If you don't believe me take something round and look at it on edge , then rotate it and you can see the arc reform as you move the object, it is the same with this and you brace . You will need to make a jig to match this curve to your braces.
john hall
blues creek guitars

I was planning on just forcing the spherical top into a cylinder. Right now I force the ladder back, which is not really braced into a sphere, onto a spherically shaped back section. There is enough give in the wood to accomodate that.

Best advice I can give , is if you need to force it , it isn't right. There is no 1 right way to build and continue on your path . Added stress in not a good thing.
john hall

[QUOTE=ToddStock] glue a piece of 1/2" ply (kerfed every 1/2" to within about an 1/8" of the face - parallel to the axis of the cylinder) to the curved faces of the cross pieces.[/QUOTE]
How about using 1/8" hardboard instead? It's flexible enough without needing to kerf it. Anybody have a reason this wouldn't work?

Hi John, what are you hoping to gain by going to a cylindrical top shape?
It should be easy enough to make, and sanding the x brace shouldn't be a problem either. I usually do a rough contour on my X and then join it and sand to whole assembled x together on my motorized dish sander. You could cut your brace contour as Todd has advised and then sand the assembled brace in your new sanding cylinder but you will probably have best results by supporting the assembly on some sort of flat plane from above the sanding surface.
I'm sure you will come up with a solution and I am interested in the results.

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Tickle your guitar daily, and it'll tickle you back.

John
   I am thinking that I would like the fingerboard extension, the soundhole and the bridge all on the same plane (more like a ridge than a plane to be sure, but lined up all the same) That was what started me thinking about cylinders. Then the stress thing got me thinking that a top would be in less stress arched into a cylinder than it would be forced into a sphere where there is a compound curvature that requires both compression and tension in the top itself. If I took your suggestion and sanded the x brace in the cylinder sanding form it would comply with the top easily enough. I am thinking I will keep the back as a sphere. For now.

So, a cylinder would have the advantages of strength in the direction of the string pull, with less stress on the top and an easier alignment of the fbe and bridge.

What do you think.

John

John,

In essence this is how Howard Klepper builds - he calls it a spline curve. he describes it here on his website. Maybe he will pitch in.

Stefan Sobell builds with most of the arch laterally as well.

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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

thanks for that info Dave

A little consensual validation is a comfort.

Klepper and Sobell are good company.

John