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One of the persistent struggles that I have relates to the neck angle and the radiused top (I use 25 foot). If I radius the entire top I end up with a drop off of the fretboard at the connection to the body that requires the fretboard to be bent down and glued to the top.

John Hall - you explained your approach to managing the radius and neck angle, but I can't find the link through the search function. Can you post the link? Thanks. Others, can you share how you you manage the geometry of the neck angle and the top (if you radius it) Thanks.

My neck block and neck are 90 degrees, but I arch my upper transverse brace so that the neck block tips back. The neck angle in relation to the soundboard is 1.5 degrees, but the neck block and neck remain 90 degrees, orthoganal to the soundboard arch. The result is no falloff where the neck joins the body and the fretboard remains straight as it extends onto the soundboard, whilst maintaining the correct height at the bridge.

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Old growth, shmold growth!

Corky,

Sorry I can't find you the tute, but here's a brief explanation:

First, a lot of confusion arises because of the different build methods used. For example, those building face down in a solara will say they use a 3mm dome (or similar), neglecting to say that that is only on the lower bout, with the upper bout flatter or just plain flat. Others use the Cumpiano method, like Guitarwhisperer.

If you're building in a spherical dish (which I think you are) you end up with whole top radiused (unless you do something about it) which then means you run in to the trouble you have found.

If you want to use a constant thickness fretboard, with no wedges/tapers over the upper bout, what actually matters is that the tangent to the upper bout projected over your future saddle position hits a specific target number. For me, that target number is 2.5mm from the projection of the tangent down to the soundboard, when used with the fret height, relief and fretboard thickness I use. With a constant radius on the top, you can't get that number. You have to flatten the upper bout so that the projected tangent flies over at a lower altitude. Exactly how much you have to flatten depends on scale length and whether you're using a 12 or 14 fret neck. With a 14 fret neck, you may be able to get away with just skimming the upper bout and removing some plate thickness to get you where you want to be. With a 12 fret neck, you will probably find you have to reduce the curvature on the upper transverse brace, which means you can't glue it down in your dish; you need a caul of the appropriate curvature.

Once that tangent is right, you set the neck angle so that the top of the neck blank is coplanar with the upper bout (no angle/kinks at the body join). The angle of the neck to the sides is irrelevant. It is just what it turns out to be when you have the other criteria satisfied. Your fretboard will then glue down in a continuous plane over the top of the neck and the upper bout without any need for bends or wedges.

There's a few more tricks involved in setting up so that the relief is right, the action is right and the string height above the soundboard is right without getting into "ski-jump" effects on the end of the fretboard. All this comes into the computation of your prefered clearance at the saddle position (the 2.5mm in my case). Details, as ever, in the usual place.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Here is a good guide for angling the upper bout above the soundhole at the same angle as the neck angle. This is on Hesh's website.

Select "Lutherie Info" then "Flattening the Upper Bout". Afterwards, you only see a little bit but you scroll down to see the rest of the tute.


http://www.heshtone.com/

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Formerly known as Adaboy.......

I think it's this one, or one within this series.

Hope it helps.

Kevin Looker

http://www.youtube.com/watch?v=QYHPCeVRUA4

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I'm not a luthier.
I'm just a guy who builds guitars in his basement.
It's better than playing golf.

There is an updated one also
http://www.youtube.com/watch?v=LrgRKKsx ... 8CA71FE7D2
Let me know if this helps you
thanks for watching

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Thanks, all. This is all very helpful. I'll review it all in detail.