solera vs radius dish

Construction and repair of Classical Guitar and related instruments

solera vs radius dish

Postby Jacob Lee » Sun Jan 13, 2008 6:04 pm

Curious what is the preference among members here as a form for getting the soundboard and back arches. I'm getting my kit together for my first build and haven't decided which one I'll use yet.

thanks,
-J.
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Re: solera vs radius dish

Postby Michael.N. » Sun Jan 13, 2008 11:16 pm

The radius dish is more of a steel string makers tool although I've no doubt that some Classical makers will use them. Traditionally it's the solera that has been used so I'd advise you to go with that - at least for now.
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Re: solera vs radius dish

Postby Jacob Lee » Mon Jan 14, 2008 1:36 am

Thanks Michael. From what I found on the net it seems that a solera is better for keeping the top flat under the fingerboard and for setting the neck angle?
Another issue I was wondering about is what to make it out of. I've started using Baltic birch ply, but am running into large knots in the middle layers. Hard to shape evenly for a smooth curve.

-J.
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Re: solera vs radius dish

Postby Michael.N. » Mon Jan 14, 2008 9:12 am

Yes, the normal method for the solera is to keep the upper bout area flat but just to confuse matters I don't! That's because when I made the solera that's how I thought it was done, makes no difference really apart from making the fretboard harder to fit.
Baltic Birch is nice for certain things but when you start cutting into it your problems start. Plywood is 'balanced' and as soon as you take off outer layers unevenly it's much more likely to warp, you've already discovered the knots and probably the glue that does nothing for edge tools.
Switch to MDF, although it's not that pleasant to use it is homogeneous in it's texture and it sands well - obviously take the precautions regarding the dust issues. I reinforced my version with a 3" deep hardwood beam that runs the full length (underside) as well as a couple of cross pieces that run at the extremes of the upper and lower body bouts. Seal everything with some hard wearing varnish.
The neck angle is planed into the neck extension of the solera. You will have to work out how much of an angle you need because it's determined by factors such as bridge depth and the amount of doming given to the soundboard. It usually runs at between 1 and 2 mm 'lift' at the nut end of the neck but you will need to work it out for your particular model. If it's any comfort I exaggerated this angle when making my solera. Again it doesn't matter because I just stick a piece of veneer at the nut end which brings everything back to where things should be.
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Re: solera vs radius dish

Postby ron sturm » Tue Jan 15, 2008 10:57 pm

Sorry Jacob and Michael, but just to keep things confusing I must disagree about MDF. I really dislike the stuff. Although it will do the job all right, I find it to be much harder on tools than plywood. It is also very heavy and the dust is simply gross. It shrinks and swells more than plywood. (both need to be well sealed for permanence, however). Edges are crumbly and it doesn't hold fasteners well. It is less stiff, so more care has to be taken with how one stores jigs while unused, or they will sag or warp.
All that being said, it is true that they are not making Baltic Birch like they used to---there are indeed knots and even some voids that one never used to see, and therefore flatness has become an issue. Nonetheless, I still prefer B.B. to anything else for jigs and forms. I do glue together 2 layers of 18mm B.B. for radius dish forms, solera, etc. and seal it well.
Lots of folks use MDF, though, so this is just another opinion.
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Re: solera vs radius dish

Postby PerHal » Wed Jan 16, 2008 7:21 am

Hi Jacob, another material to use is ordinary particleboard (if that is the correct English word). I find it somewhat less fragile than mdf. Just my taste I guess. But my input in this discussion is another than the material. Instead of making a solera you could consider making a slightly more versatile system that incorporates a very thin plywood solera on a base.

Here is the base. My is made from scrap that happened to be both plywood and particle board (the plywood on top) but since the material was dry and my workshop is climate controlled it has worked without warping. Anyway, the base is a sturdy wooden beam on which the workboard is attached. The workboard has slots cut out along the body line. You will soon see why. The neck part has no plywood, only the lower layer that consists of the particle board.

http://i194.photobucket.com/albums/z150 ... en/h17.jpg

On the neck part I can fit plywood wedges and thus choose what neck angle I want. My finger point at the nut position and it is lowered 2 mm (in this case). If I want a steeper angle I just change the wedge to another. Since I use the same type of baltic birch plywood it fits right in at the body.

http://i194.photobucket.com/albums/z150 ... en/h18.jpg

Here is the solera positioned at the workboard. It is made from 10 mm plywood but any material can work as long as you can scoop out the doming and it is flexible enough to be bent over the body/neck angle. My finger points at the scooped out part of the solera. In this case it is domed by ca 2 mm.

http://i194.photobucket.com/albums/z150 ... en/h19.jpg

Here is the neck and top positioned on top of the solera. A bolt through the beam/workboard and soundhole is holding a small wooden block pressing the top against the solera. Two clamps is holding the neck. The neck angle is defined.

http://i194.photobucket.com/albums/z150 ... en/h20.jpg

Here are the sides held against the top with spool clamps. A couple of side supports is helping the sides to find their correct outline. At the end block is a heavy block attached to the work board as a support for the smaller block of plywood that is fitted between the big block and the sides. This smaller block has the curve of the body outline against the sides and is flat against the big block.

http://i194.photobucket.com/albums/z150 ... en/h21.jpg

To conclude. With this system you can build any guitar shaped instrument, with any neck angle and any doming by changing neck wedge and solera. I am sure many luthiers around the world are using similar systems since it is a natural development of the traditional solera.

And by the way, those pictures are not taken for this post, they are a part of a more than 200 picture long photo essay I have done on two Swedish guitar forums and one English flamencoguitar forum.
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Re: solera vs radius dish

Postby MarkJ » Wed Jan 16, 2008 2:33 pm

I think you will need both a solera and a radius dish. I use a solera made from MDF for the top as others have described, but a dish work great for getting a slight dome on the back. I have sandpaper stuck to a 28 foot radius dish and I sand the back braces , glue the braces and back reinforcement strip to the back in the dish, and use it to sand the secondary bevel on the sides/lining to get a perfect fit with the back. Some folks use a 25 foot dish.
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Re: solera vs radius dish

Postby PerHal » Wed Jan 16, 2008 3:06 pm

I forgot about the backbraces...I agree with MarkJ. A radiused dish is a good way to achieve the arching of the back, but not the only way. You can make a arching template and rout the arching on the braces. Quicker than sanding in a dish.
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Re: solera vs radius dish

Postby Michael.N. » Wed Jan 16, 2008 4:28 pm

It's clearly not the only way because Torres glued his back braces onto the assembled top/neck/sides before gluing on the actual back.
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Re: solera vs radius dish

Postby Florian Thomas » Wed Jan 16, 2008 6:20 pm

Like it's been said before I think radius dish is not very useful for top because it makes things trickier for the fingerboard fitting but I'm seriously thinking of using it for back bracing because it looks so much easier and accurate as well. Once the linings glued on the ribs you just sand them quickly with the dish... being careful of course not to take too much wood ;)
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Re: solera vs radius dish

Postby Les Backshall » Thu Jan 17, 2008 11:41 pm

I’ve only recently started building guitars and one of the problems I came up against on the first one was keeping everything square and correctly aligned as the work progressed. So recently, I did some mock-ups using both a solera and a radius dish.

As has been mentioned above, I found the solera does something important that the radius dish does not. It ensures the edges of the top lie on a flat plane (even if the centre is domed). This makes it much easier to precisely fit the ribs and control the neck geometry.

By contrast, with a radius dish, the edges of the top will not lie on a flat plane. If you offer a straight edged rib to the top in a radius dish, there will be gaps, most noticeably in the waist area. If you then shape the edge of the rib so that it meets the top all the way along it will be curved and hence no reference plane. Determining the neck geometry will then be much more hit and miss.

The back is obviously not so critical, but I shall definitely use a solera for tops.

Les
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