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Flattening Upper Bout (Pics..)
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Author:  Hesh [ Sun Feb 07, 2010 1:21 pm ]
Post subject:  Flattening Upper Bout (Pics..)
The following method is how I remove the radius from the upper bout of my tops. The reason why anyone might want to do this is to provide a flat, level surface above the sound hole for the fretboard extension to smoothly transition onto. In short this is one way to avoid the hump that can happen at the neck/body joint and to eliminate gaps where the fretboard is glued to the upper bout of the top.

This method is not mine and I believe that I learned it from a Frank Finochio DVD some years back.

Presumptions: If one is to employ this method it is presumed that they will also take measures to either greatly reduce or eliminate the radius in their tops above the sound hole. I do this simply by using an upper transverse brace that is flat and not radiused. This brace is glued to the top on a flat board also and is the last of the major braces that I glue to my tops.

Others who I know may leave a very slight radius in their UTB such as a 50+ radius or flatten the part of the UTB under the fretboard extension. Since I make my upper transverse brace completely flat I can't speak for these other choices but I do know that this is being done.

Now that we understand that this method is part of a system that presumes that you will remove the radius from the upper bout of your top let's get started.

Step one for me is with the rim top side up and I make pencil marks on the kerfed linings from waist through the neck block.

Attachment:
DSC02790.jpg


These marks will be indicators of our progress as we sand the upper bout flat.

Next I use a flat board that I have dedicated for this purpose but any flat surface will work if you don't mind sticking self-stick 120ish grit sandpaper to it. Here we see a quick check to be sure that my board is pretty flat.

Attachment:
DSC02791.jpg


This is the set-up to flatten your upper bout. The guitar rim is placed top side down on the flat board with self-stick sandpaper on it. The pencil lines have been drawn from the waist forward. A 1/8" shim/stick/whatever is placed under the tail block to elevate the back of the rim.

Attachment:
DSC02792.jpg


Now this is not unlike using a radius dish on the rim except that this time we will be keeping the tail block that is elevated on the 1/8" shim fairly stationary as we move the neck block back and forth effectively sanding the upper bout of the top side of the rim.

Initially since this rim was radiused to 25" we will see most of the action in the waist area. As the sanding progresses we will see the contact area move forward to eventually sand the top of the neck block eliminating the radius in the upper bout.

Attachment:
DSC02793.jpg


Here is a close-up showing the shim/stick under the tail block that acts as our pivot point while sanding the upper bout.

Attachment:
DSC02794.jpg


The next pics will simply show the progress of our sanding until the pencil marks are completely sanded off.

Attachment:
DSC02795.jpg


Attachment:
DSC02798.jpg


And finally we are done!

Attachment:
DSC02801.jpg


Again this method presumes that the builder will also remove or greatly reduce the radius from their top bracing above the sound hole. You can still build in any radius that works for you below the upper transverse brace. In short the rim is prepared for the radiused top and then additionally prepared to accept the flattened upper bout of the top.

Fall Away: Fall away refers to the fretboard extension and building the guitar in such a manner that the fretboard extension's height in relation to the strings is additionally increased from the body joint to the sound hole. I like to see about .015 of fall-away at the last fret when comparing to the fret at the body joint.

The method above provides me with approx .015 of fall-away with no additional tweaking on my part.

I have used this method exactly as described here on L-OO's, OM's, dreadn*ughts, and SJ's and it works great for me.

Thanks for looking! [:Y:] :)
Author:  Joe Sustaire [ Sun Feb 07, 2010 1:46 pm ]
Post subject:  Re: Flattening Upper Bout (Pics..)
Very nice toot Hesh!
I was expecting to see a sanding stick pivoting on the bridge area on a block and sanding a flat onto the fretboard overhang area of the top. (already assembled box) Which is a method I have seen used, but this avoids the problem which is much better.

Thanks,
Joe
Author:  James W B [ Sun Feb 07, 2010 3:38 pm ]
Post subject:  Re: Flattening Upper Bout (Pics..)
This is an excellent toot as usual from Flushtone Guitars :lol: I do the exact same thing ,which I learned from Hesh , and it works perfectly.
SKIN
Author:  JohnAbercrombie [ Sun Feb 07, 2010 3:58 pm ]
Post subject:  Re: Flattening Upper Bout (Pics..)
Very clear- thanks, Hesh!
BTW, you can stick a round of sandpaper on the flat side of a radius dish - saves on the 'workboard clutter' around the shop.

Cheers
John
Author:  Eric Reid [ Sun Feb 07, 2010 11:50 pm ]
Post subject:  Re: Flattening Upper Bout (Pics..)
Very interesting--and well presented. I'm curious about the advantages you see over "traditional" Spanish construction (building up from a top-neck assembly clamped to a solera with curvature only in the lower bout). If the top is lined with dientes, I think the old way is hard to improve on. If kerfed linings are used (a la Torres), I can see that what your doing would give a better fit. (And maybe you're doing what Torres did; I have no idea.) About the fall-away in the fingerboard extension: I know that's common practice, but why? Insurance for future neck rotation? So notes don't "fret out" when bending? I've always thought there were better ways of dealing with both these issues. Again, thanks for posting this--you've got me thinking.
Author:  Hesh [ Mon Feb 08, 2010 6:34 am ]
Post subject:  Re: Flattening Upper Bout (Pics..)
Thanks guys.

John great idea and .... gaah I don't know why I never thought of turning over the dish..... :D

Eric this toot has nothing to do with comparing traditional Spanish construction to anything else. I am just showing how I build a flat upper bout into my guitars instead of trying to flatten the upper bout as an after thought. Having never built with traditional Spanish construction I am not qualified to address your question - sorry. It's a great question though perhaps you should start a thread asking it?

As for fall-away the purpose is simple and that is to put more distance between the top of the frets and the vibrating strings in the area where the strings lash back and forth a great deal and also in the area close to where we pluck/pick them also causing the strings to lash around more. It's to avoid string contact with the frets when we don't want it.

Thanks everyone. :)
Author:  Michael [ Mon Feb 08, 2010 8:20 am ]
Post subject:  Re: Flattening Upper Bout (Pics..)
I build my steel string guitars with flat tops (Steve Stevens) with a slight arch to the upper face brace to set up the proper height for the bridge. To adjust this angle after the box is closed can thin the upper bout too much and has been a major pain. Your method solves all of my problems. Thanks!!
Michael
Author:  Ricardo [ Mon Feb 08, 2010 6:27 pm ]
Post subject:  Re: Flattening Upper Bout (Pics..)
Eric, if you make your solera with enough dome you won't have to do anything with the fingerboard or upper bout. Thats the way I built my Torres 1888. I don't like the idea of thinning the fingerboard as you approach the body or undercut the fingerboard extension.
Author:  Steve Brown [ Mon Feb 08, 2010 7:22 pm ]
Post subject:  Re: Flattening Upper Bout (Pics..)
Hesh,

I noticed that you have holes drilled around the edge of your mold. Can you explain these in a future toot.

Steve Brown
Author:  Hesh [ Mon Feb 08, 2010 7:29 pm ]
Post subject:  Re: Flattening Upper Bout (Pics..)
Sure Steve - prior to building a go-bar deck I used spool clamps to attach the top and back plates to the rim. The holes are for the spool clamps and a relic from my Lutherie past.... :? :) A go-bar deck is MUCH easier AND faster.... [:Y:]

Thanks everyone!
Author:  Stephen Boone [ Mon Feb 08, 2010 7:52 pm ]
Post subject:  Re: Flattening Upper Bout (Pics..)
Very nice Hesh!

This is something that I have been thinking about for the last few days. Does this maintain the neck angle formed with the radius dish but just make everything in a flat plane above the upper transverse brace?

Thanks,
Author:  Hesh [ Tue Feb 09, 2010 6:13 am ]
Post subject:  Re: Flattening Upper Bout (Pics..)
Thanks Stephen!

"Does this maintain the neck angle formed with the radius dish but just make everything in a flat plane above the upper transverse brace?"

Yes as evidenced by how the flat board with self-stick on it made contact with the rim in the waist area and then forward through the neck block. The rim was not touched south of the waist maintaining the radius that was originally sanded into the top south of the sound hole.

All we are doing here is instead of sanding the upper bout flat we are building the upper bout to be flat but still building in our dome, what ever radius we use, south of the sound hole.
Author:  Darryl Young [ Tue Feb 09, 2010 10:40 pm ]
Post subject:  Re: Flattening Upper Bout (Pics..)
Thanks for the great tutorial Hesh! It's good timing for me. When I was at this stage, I sanded a 1 1/2 deg neck angle above the soundhole by using this method:

Attachment:
Neck Angle After Sanding.JPG


However, I didn't use my 28ft radius dish at the time so the rest of the rim (on top) is untouched.

Jump forward to the present. The back is glued to my rim and I'm wanting to get the top of the rim prepped so I can route out the slots for top bracing.

First question: I'm thinking I should use the radius dish, then maybe use my setup pictured above (or your suggested method) to re-establish the flat, neck angle. Sound correct?

Second question: At the point on each side of the rim where the radius contour stops and the flat angle starts, should I try to blend this area a little to make a smooth transition or is this a non-issue? In my mind I picture the soundboard kinked here (which I'm sure wouldn't be good) but since I haven't actually sanded these profiles, maybe it's very subtle.
Author:  Hesh [ Wed Feb 10, 2010 7:33 am ]
Post subject:  Re: Flattening Upper Bout (Pics..)
Darryl Young wrote:

First question: I'm thinking I should use the radius dish, then maybe use my setup pictured above (or your suggested method) to re-establish the flat, neck angle. Sound correct?

Second question: At the point on each side of the rim where the radius contour stops and the flat angle starts, should I try to blend this area a little to make a smooth transition or is this a non-issue? In my mind I picture the soundboard kinked here (which I'm sure wouldn't be good) but since I haven't actually sanded these profiles, maybe it's very subtle.


Darryl buddy I can't know what your set-up does and to what degree so I can't comment. If you do want to flatten the upper bout using the system that I described (it's not mine and I indicated that I learned it from Frank F.) I would use the dish to establish the proper radius and then elevate the tail block 1/8" as described and sand the upper bout of the top flat. Of course I also indicate that this is part of a system so your UTB needs to be flat or nearly flat too.

As for question 2 fitting the top when built with a non-radiused UTB to the rim requires no bending - it will fit nicely as is.

Thanks
Author:  Mike Lindstrom [ Wed Feb 10, 2010 8:45 am ]
Post subject:  Re: Flattening Upper Bout (Pics..)
Good explanation, Hesh. Thanks. My question may be the same as Darryl's, but not quite.

The way I learned (which may be different from what I was taught) to use a flat UTB, and after the neck was on, sand a flat spot under the fretboard. I use a small granite sanding block with a layer of tape on the neck end to keep from wearing down the neck too. It doesn't end up perfectly flat, but close. I'm guessing this eliminates the hump, but also stops any fall-off. (I had forgotten, but I think we planed a little it once the fretboard was on maybe.)

With your method, when you set your neck, how does it match up to the top? If the fall-off is built into the body, do you taper the underside of your FB to match? Does it just flex down when you clamp it?

Thanks,
Mike
Author:  Hesh [ Wed Feb 10, 2010 8:57 am ]
Post subject:  Re: Flattening Upper Bout (Pics..)
Mike my friend this method leaves me with a flat upper bout and I don't have to do anything additional to sand it flat.

As for the fretboard extension what else is happening in that little piece of wood? We are installing frets and they are closer together than they are any other place on the fretboard. As such there is a tendency for the fretboard extension to want to curve downward anyway do to the frets occupying the slots in close proximity.

Now we have an upper bout that has been flattened AND fall-away (approx .015") is built in and we have a fretboard extension that wants to curl downward due to the frets filling the slots - sounds like a match does it not? :) And what I see every time I do this is a near perfect match. I don't have to do anything to the bottom of my fretboards but I do scrape them prior to gluing with a small puddle of Elmers ala Mario P.

The neck angle does not change when doing the method. The bridge is still on a radiused part of the top and the top of the rim where the neck cheeks mate is unchanged. In my experience all necks need to be fitted and flossed but the fitting and flossing is minimal with the method described.
Author:  Darryl Young [ Wed Feb 10, 2010 5:35 pm ]
Post subject:  Re: Flattening Upper Bout (Pics..)
Thanks for responding Hesh!

I don't think anyone can mess up a question worse than I! I'll try asking the question again. To eliminate variables, lets discuss your rim used in the tute above.

After the rdius was sanded in the top of the rim using your dish, you then flattened the top of the rim above the soundhole. If you viewed the rim from the side, where the flat portion of the rim meets the radiused portion of the rim......is it an abrupt transition? Do you hand sand this area to "blend" this transition area from radiused to a flattened angle? Since I haven't tried it, the transition may be very subtle not needing any attention, not sure.

Also, do you touch-up the sanding later.......just prior to glueing the top to the rim?
Author:  Hesh [ Wed Feb 10, 2010 6:13 pm ]
Post subject:  Re: Flattening Upper Bout (Pics..)
I understand Darryl my friend - no there is no noticeable or abrupt transition where the radiused part of the rim meets the flattened part of the rim. You would not be able to tell where this happens it is so very subtle. I've never hand sanded this area and probably could not find it either.

And no I do not touch up anything later prior to joining the top and back to the rim. If by chance the rim is removed from the mold say to install a butt wedgie... I would repeat the dish sanding and flattening the upper bout of the top to be sure that everything is where I want it. But I don't remove the rim from the mold after dish sanding so this is not an issue.

Does this answer your questions? :)
Author:  Darryl Young [ Wed Feb 10, 2010 6:33 pm ]
Post subject:  Re: Flattening Upper Bout (Pics..)
Yes! Thanks Hesh
Author:  Rene [ Thu Mar 04, 2010 3:31 pm ]
Post subject:  Re: Flattening Upper Bout (Pics..)
Hesh,
After going back and looking at your tutorial a second time I noticed in a couple of pics where you placed a stick under the Neck Block. I understand the stick under the tailblock to elevate the lower bout, but can you explain why under the neck block?

Thanks,
René
Author:  Hesh [ Thu Mar 04, 2010 6:26 pm ]
Post subject:  Re: Flattening Upper Bout (Pics..)
Sure Rene - in the pic with the stick under the neck block the point of interest of the picture according to the text are the pencil marks on the neck block and kerfed linings. I simply turned the rim over to photograph the pencil marks and did not remove the stick but probably should have since it confused you. The stick does not need to be in this picture. My apologies.
Author:  Rene [ Thu Mar 04, 2010 6:47 pm ]
Post subject:  Re: Flattening Upper Bout (Pics..)
Hesh,
Thanks for the clarification, I was sure it was more important than that.

René
Author:  Paul Burner [ Fri Mar 19, 2010 8:15 am ]
Post subject:  Re: Flattening Upper Bout (Pics..)
Hesh,

This is very clearly explained - and nice photos to accompany the toot.

Exactly the information I needed.

I had a couple things wrong in my setup - but was close.

Excited to try your method.

Thanks as always!
Author:  Hesh [ Tue Mar 23, 2010 5:43 pm ]
Post subject:  Re: Flattening Upper Bout (Pics..)
You are very welcome Paul - glad this helped.
Author:  coach [ Fri May 21, 2010 7:50 am ]
Post subject:  Re: Flattening Upper Bout (Pics..)
Hesh wrote:
The method above provides me with approx .015 of fall-away with no additional tweaking on my part.

I have used this method exactly as described here on L-OO's, OM's, dreadn*ughts, and SJ's and it works great for me.

Thanks for looking! [:Y:] :)


Thanks so much for sharing that advice! Quick question. When you are sanding the sides for different radii, do you worry about changing the dimensions of the side, like how deep the guitar is at the lower bout versus the upper bout. I was also wondering if you should get your side dimensions accurate before you bend, or after? And do you leave a little extra to compensate for the radii sanding?

Just a newbie, about to build my first and trying to get as much info as possible. Thanks.

Sean
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